Datasets:

knguyennguyen

/

wikipedia_laptop

like 0

OS X Mountain Lion OS X Mountain Lion (version 10.8) is the ninth major release of macOS, Apple Inc.'s desktop and server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012, for purchase and download through Apple's Mac App Store, as part of a switch to releasing OS X versions online and every year, rather than every two years or so. Named to signify its status as a refinement of the previous OS X version, Lion, Apple's stated aims in developing Mountain Lion were to allow users to more easily manage and synchronise content between multiple Apple devices and to make the operating system more familiar. The operating system gained the new malware-blocking system Gatekeeper and integration with Apple's online Game Center and iCloud services, while the Safari web browser was updated to version 6. As on iOS, Notes and Reminders became full applications, separate from Mail and Calendar, while the iChat application was replaced with a version of iOS's Messages. Mountain Lion also added a version of iOS's Notification Center, which groups updates from different applications in one place. Integrated links allowing the user to rapidly transfer content to Twitter were present in the operating system from launch. Facebook integration was also planned but unfinished at launch date. It was released as a downloadable update later. OS X Mountain Lion received positive reviews, with critics praising Notification Center, Messages, and speed improvements over Mac OS X Lion, while criticizing iCloud for unreliability and Game Center for lack of games. Mountain Lion sold three million units in the first four days, and has sold 28 million units as of June 10, 2013, making it Apple's most popular OS X release. Mountain Lion was the last paid upgrade for an OS X major release, with OS X Mavericks and later being free. Apple later allowed free downloads of the OS, especially for customers of older and no longer officially supported Macintosh computers, starting on June 30, 2021. The same practice was also applied to its predecessor, Mac OS X Lion. History OS X Mountain Lion was officially announced by Apple on their website on February 16, 2012, as a successor to OS X Lion. It achieved golden master status on July 9, 2012. During the Apple Worldwide Developers Conference keynote on June 11, 2012, Apple announced a "near final" release version of Mountain Lion for developers, with the public version arriving in July 2012 at a price tag of US$19.99 (€15.99 in Europe, £13.99 in the UK, $20.99 in Australia and ￥128 in Mainland China). The third generation MacBook Pro, revised MacBook Air, iPad Smart Case, and third-generation AirPort Express were announced at the keynote as well. The specific release date of July 25 was not confirmed until the day before, July 24, by Apple CEO, Tim Cook, as part of Apple's 2012 third-quarter earnings announcement. It was released to the Mac App Store on July 25, 2012, where it sold 3 million units in the first four days of release. An update for Mountain Lion, version 10.8.1, was released on August 23, 2012. It resolved issues with iMessages, Migration Assistant, Safari, Microsoft Exchange Server, Mail, and many other applications. Tests of the update revealed that 10.8.1 also improved battery life on laptops, albeit gaining back only half of the battery life that was lost in updating to Mountain Lion. Although 10.8.1 improved battery life for some customers, others continue to complain about reduced battery life and a constant drop in battery health, ultimately resulting in a "Service Battery" message. System requirements The official system requirements of OS X 10.8 are 2 GB RAM, 8 GB available storage, OS X 10.6.8 (Snow Leopard) or later, on any of the following Macs: iMac (Mid 2007 or newer. Late 2006 is supported if an app called MlPostFactor v0.3 is used.) MacBook (Aluminum, Late 2008), (Polycarbonate, Early 2009 or newer) MacBook Pro (Mid/Late 2007 or newer) MacBook Air (Late 2008 or newer) Mac Mini (Early 2009 or newer) Mac Pro (Early 2008 or newer) Xserve (Early 2009) As in 10.7, the earliest models supporting AirDrop are the late-2008 MacBook Pro, late-2010 MacBook Air, late-2008 MacBook, mid-2010 Mac Mini, and early-2009 Mac Pro with an AirPort Extreme card. Any Mac released in or after 2011, except the MacBook, supports AirPlay Mirroring. Power Nap is supported on the mid-2011 or newer MacBook Air and the MacBook Pro with Retina display. The technical basis for these requirements is incompatibility with 32-bit EFI and 32-bit kernel extensions (most importantly, drivers for GPUs shipped in some older Macs). In order to prevent potentially incompatible systems from installing 10.8, the installer contains a whitelist of supported motherboard IDs. Users have bypassed these limitations so that 10.8 may run with varying functionality on some officially unsupported computers. New and changed features Notification Center Notification Center was added in the operating system. It provides an overview of alerts from applications and displays notifications until the user completes an associated action, rather than requiring instant resolution. Users may choose what applications appear in Notification Center, and how they are handled. There are three types of notifications: banners, alerts, and badges. Banners are displayed for a short period of time in the upper right corner of the Mac's screen, and then slide off to the right. The icon of the application is displayed on the left side of the banner, while the message from the application will be displayed on the right side. Alerts are the same as banners, but will not disappear from the screen until the user takes action. Badges are red notification icons that are displayed on the application's icon. They indicate the number of items available for the application. Notification Center can be accessed by clicking the icon in the right corner of the menu bar. When open, the user can click a button to tweet, post status updates to Facebook, or view all notifications in the sidebar pane. Swiping up will reveal the option to disable Notification Center for one day. Many settings of Notification Center can be customized under the "Notifications" pane in System Preferences. Each application can have three ways to display notifications: none, banners, and alerts. Options to toggle the app icons and sounds are also available. Users can click and drag an app in the pane to change the order the applications are displayed within Notification Center. Notes Notes, another transfer from iOS, is added. It is separate from Mail in its own application, with support for desktop notes added (syncs along with its iOS counterpart). Created notes are synced through all the user's Apple devices through the iCloud service. Notes can be arranged in folders, and pinned to the user's desktop. When the application is closed, the pinned note still remains. Notes can be created in three different default fonts - Noteworthy, Marker Felt, and Helvetica. Users can add custom fonts by visiting the menu. The menu allows users to change text size, format lists, choose the alignment (left, center, justify, or right), assign a writing direction, and indent text. Attachments, images, and hyperlinks can also be added into a note. Attachments cannot be viewed on iOS devices. Messages Messages, an instant messaging software application, is added in Mountain Lion. It was announced on February 16, 2012, as part of the OS X Mountain Lion developer preview. Starting with this release, Messages replaced iChat as the default OS X instant-messaging client. A free beta version of Messages was available to download for Mac OS X Lion from the Apple website until June 2012. The final version of Messages was included with the release version of OS X Mountain Lion. As with its predecessor, Messages has text messaging, audio, and screen-sharing capabilities. Messages also contains native video conversation support, utilizing Apple's FaceTime video calling application where possible. However, it does retain video capabilities for interfacing with other instant messaging clients. Messages supports Apple's iMessage, a free instant messaging service previously only available on devices running iOS 5. It also supports both Extensible Messaging and Presence Protocol (XMPP) (shown in the application under its former name, Jabber) and the AOL Instant Messenger (AIM) OSCAR protocol. It also offers a direct connection to Yahoo! Messenger and Google Talk. Game Center The Game Center application from iOS was added in OS X Mountain Lion. It is an online multiplayer social-gaming network, and allows users to invite friends to play a game, start a multiplayer game through matchmaking, track their achievements, and compare their high scores on a leader board. Points are awarded to players as a part of Game Center's achievement tracking system. Players can earn points by meeting specific in-game challenges. A player must establish an Apple ID to associate with a Game Center nickname. A player has the option to create an Apple ID from within Game Center if they do not already have one. Only one nickname may be associated with an Apple ID at any given time. Each player is assigned a profile in Game Center. A profile consists of the player's nickname, the number of Game Center-compatible games the player owns, the number of friends the player has, the number of achievement points a player has, and an optional photo and player-defined status. Application updates OS X Mountain Lion added updates for many applications on the operating system. The Chess app supports Game Center. Dashboard widgets can be managed in a UI similar to Launchpad. Mail adds new VIP feature to save frequent contacts. The Preview app gets an improved user interface. It is able to fill out forms in PDF documents that don't contain actual PDF form fields. Reminders is a new to-do list application, separate from Calendar in its own application that syncs along with its iOS counterpart. Safari 6 gets a new release and features a new address bar; a combination of the address bar and the search field. The address bar also has a "Reader" button, showing the user just the text of the article without advertisements and distraction. When the user is on a website with no article, the button is disabled. Safari 6 is available as a download for Mac OS X Lion. Time Machine is able to do rotating backups on more than one storage medium. Other applications found in Mountain Lion AirPort Utility App Store Archive Utility Audio MIDI Setup Automator Bluetooth File Exchange Boot Camp Assistant Calculator ColorSync Utility) Console Contacts Dictionary Digital Color Meter Disk Utility DVD Player FaceTime Font Book GarageBand (may not be pre-installed) Grab Grapher iMovie (may not be pre-installed) iTunes Image Capture Keychain Access Keynote (may not be pre-installed) Messages Migration Assistant Notes Notification Center Numbers (may not be pre-installed) Pages (may not be pre-installed) Photo Booth QuickTime Player Script Editor Stickies System Information Terminal TextEdit VoiceOver Utility Other updates AirPlay Mirroring is added, which allows wireless mirroring of a Mac's screen to an Apple TV. System-wide integration of AirPlay audio transmission is added. There are many new features for Chinese users, including support for Baidu as an option for Safari search engine, QQ, 163.com and 126.com services for Mail, Contacts and Calendar, Youku, Tudou and Sina Weibo are integrated into share sheets. Dictation, new in Mountain Lion, is a system-wide voice input mechanism that requires a broadband Internet connection. Facebook gained full integration following an update in late 2012. Some of the features include single-sign on and integration in Notification Center, Contacts and Share Sheets. Gatekeeper, also new to Mountain Lion, is an anti-malware feature based on digital signatures and the Mac App Store. Power Nap allows flash storage-based Macintoshes (late 2010 MacBook Air and later, or the MacBook Pro with Retina display) to synchronize with iCloud (Reminders, Calendars, Photo Stream, Notes, Mail, and Find My Mac) while sleeping and also allows a Mac to download App Store and OS X updates as well as make periodic Time Machine backups when it is plugged in and sleeping. Several new screensavers were added. Share Sheets, a "Share" button and dialog box in Safari and other applications, are added. Twitter was integrated with almost all of the applications, with single-sign on, tweeting from an app, Tweet Sheets, tweeting photos and links, using multiple Twitter accounts, Twitter notifications, profile picture integration, and Location Services available. Application updates automatically install from the Mac App Store. The iCloud library User interface (UI) was integrated throughout the operating systems, which includes new Open and Save dialog boxes across built-in applications, iWork and third-party applications via an Application programming interface (API). Applications that make use of this API support a new user interface to view and manage documents in the cloud that are specific to the application being used. Documents can be renamed from the title bar. iWork documents automatically synchronize with iCloud. The full screen ability is on every display. The Dock has received an updated look, emulating the appearance of the aluminum metal surface that much of Apple's current hardware line-up sports. Scroll bars widen when the mouse hovers over them. Finder displays a progress bar in the "size" column when copying a file, and on icons in Launchpad when downloading from the Mac App Store. Launchpad has Spotlight search for finding applications. Address Book was renamed "Contacts", and iCal was renamed "Calendar". Dropped and changed features MobileMe was replaced entirely by iCloud, specifically in System Preferences options. RSS support in Mail and Safari was removed; a message is shown to suggest to users that they search the Mac App Store for an RSS app. The Software Update service was unified into the Mac App Store. The list of updates installed in the past was removed. The "Web Sharing" option was removed from System Preferences. Apache is still included with the operating system and can be enabled using third-party software. When the X11 app is opened, users are directed to the open source XQuartz project instead. Xgrid support was removed (including in OS X Server edition). The Display Preferences status menu was replaced by the AirPlay icon, and it is no longer possible to quickly switch resolutions without first opening up preferences. The option in Menu Bar to display battery life using "Time" is no longer offered. Instead, the only option is to display battery "Percentage". However, battery time can still be viewed in the dropdown by clicking on the battery icon. Reception Reception for OS X Mountain Lion has generally been positive, with users considering it to be a major improvement over 10.7 Lion. John Siracusa of Ars Technica said that 10.8 corrected and simplified UI changes made with Lion, saying that it had become "what 10.7 should've been" and that the faster speeds and features merit the upgrade, then adding that "If we'd had to wait for two years after 10.6 for the next major release of OS X, chances are good that the worst of the missteps in Lion would just be landing on our doorsteps today. I'll take 10.8, thanks." Many reviewers found that Mountain Lion was far more stable than its predecessor, including Jason Snell of Macworld, who said "All told, I found Mountain Lion to be a stable, solid release. Even prerelease builds were far more stable than I've come to expect from OS X betas, leading me to wonder if Apple's new annual schedule is leading to more careful incremental updates (with fewer bugs) rather than great leaps (with more, nastier bugs)." The general attitude towards Mountain Lion was that it was faster and smoother, including Brian Heater of Engadget, who said the following: MG Siegler of TechCrunch said that the difference between Lion and Mountain Lion was not comparable to the difference between Leopard and Snow Leopard because Mountain Lion adds many new features that were not available in Lion. He also praised the application compatibility and said that the only updates needed were to add Notification Center features to applications. Jim Dalrymple of The Loop commented "there will be tens of thousands of words published on Wednesday when Mountain Lion hits the Mac App Store, but let's face it, what you really want to know is whether Mountain Lion is worth the upgrade. Let's get that out of the way now — yes, it is definitely worth it," and said that at $19.99, Mountain Lion was a "bargain". David Pogue of The New York Times said "Over all, then, Mountain Lion is a gentle, thoughtful upgrade. All 200 new features? No, not really. But 10 that you'll use every day? For $20? Yes." While the operating system in general was well received, some reviewers dissented from that viewpoint. Jesus Diaz of Gizmodo felt that Apple was running out of ideas and that Microsoft's Windows 8 may out-innovate OS X. Apple also received criticism for failing to provide an official upgrade pathway for owners of 2006 Mac Pro workstation computers. Game Center was the most criticised aspect of Mountain Lion. Reviewers criticized the service for the lack of games available, reliability issues and the lack of integration with iOS games. Scott Stein of CNET commented "Game Center-compatible titles will have achievements, leaderboard info...and, potentially, a way of playing cross-platform games. As of the time of this post, I could find only seven Game Center games featured the Mac App Store," and "Until Game Center becomes a complete portal for all games on the Mac, and a true method of cross-platform iOS/Mac play, I'm not sure many people will even bother checking it out." Matt Clark of MacLife also commented that if developers don't develop applications for Game Center, it is "likely doomed to sit unnoticed on your hard drive". Mountain Lion sold 3 million units in the first four days, making it Apple's most successful OS X release to date. A report by Chitika Insights revealed that OS X Mountain Lion had been used by 3.2% of OS X users within the first 48 hours of release, and 10% penetration in the first month. Release history Note: Combo updates include all previous releases (ex: 10.8 to 10.8.3). Individual update is a smaller package size and can be used if currently using the previous release (ex: 10.8.2 to 10.8.3). See also History of macOS List of Macintosh software References External links 8 X86-64 operating systems 2012 software Computer-related introductions in 2012

Operating System (OS)

Palm OS Palm OS (also known as Garnet OS) is a discontinued mobile operating system initially developed by Palm, Inc., for personal digital assistants (PDAs) in 1996. Palm OS was designed for ease of use with a touchscreen-based graphical user interface. It is provided with a suite of basic applications for personal information management. Later versions of the OS have been extended to support smartphones. Several other licensees have manufactured devices powered by Palm OS. Following Palm's purchase of the Palm trademark, the currently licensed version from ACCESS was renamed Garnet OS. In 2007, ACCESS introduced the successor to Garnet OS, called Access Linux Platform; additionally, in 2009, the main licensee of Palm OS, Palm, Inc., switched from Palm OS to webOS for their forthcoming devices. Creator and ownership Palm OS was originally developed under the direction of Jeff Hawkins at Palm Computing, Inc. Palm was later acquired by U.S. Robotics Corp., which in turn was later bought by 3Com, which made the Palm subsidiary an independent publicly traded company on March 2, 2000. In January 2002, Palm set up a wholly owned subsidiary to develop and license Palm OS, which was named PalmSource. PalmSource was then spun off from Palm as an independent company on October 28, 2003. Palm (then called palmOne) became a regular licensee of Palm OS, no longer in control of the operating system. In September 2005, PalmSource announced that it was being acquired by ACCESS. In December 2006, Palm gained perpetual rights to the Palm OS source code from ACCESS. With this Palm can modify the licensed operating system as needed without paying further royalties to ACCESS. Together with the May 2005 acquisition of full rights to the Palm brand name, only Palm can publish releases of the operating system under the name 'Palm OS'. As a consequence, on January 25, 2007, ACCESS announced a name change to their current Palm OS operating system, now titled Garnet OS. OS overview Palm OS was a proprietary mobile operating system. Designed in 1996 for Palm Computing, Inc.'s new Pilot PDA, it has been implemented on a wide array of mobile devices, including smartphones, wrist watches, handheld gaming consoles, barcode readers and GPS devices. Palm OS versions earlier than 5.0 run on Motorola/Freescale DragonBall processors. From version 5.0 onwards, Palm OS runs on ARM architecture-based processors. The key features of the current Palm OS Garnet are: Simple, single-tasking environment to allow launching of full screen applications with a basic, common GUI set Monochrome or color screens with resolutions up to 480x320 pixel Handwriting recognition input system called Graffiti 2 HotSync technology for data synchronization with desktop computers Sound playback and record capabilities Simple security model: Device can be locked by password, arbitrary application records can be made private TCP/IP network access Serial port/USB, infrared, Bluetooth and Wi-Fi connections Expansion memory card support Defined standard data format for personal information management applications to store calendar, address, task and note entries, accessible by third-party applications. Included with the OS is also a set of standard applications, with the most relevant ones for the four mentioned PIM operations. Version history and technical background Manufacturers are free to implement different features of the OS in their devices or even add new features. This version history describes the officially licensed version from Palm/PalmSource/ACCESS. All versions prior to Palm OS 5 are based on top of the AMX 68000 kernel licensed from KADAK Products Ltd. While this kernel is technically capable of multitasking, the "terms and conditions of that license specifically state that Palm may not expose the API for creating/manipulating tasks within the OS." Palm OS 1.0 Palm OS 1.0 is the original version present on the Pilot 1000 and 5000. It was introduced in March 1996. Version 1.0 features the classic PIM applications Address, Date Book, Memo Pad, and To Do List. Also included is a calculator and the Security tool to hide records for private use. Palm OS 1.0 does not differentiate between RAM and file system storage. Applications are installed directly into RAM and executed in place. As no dedicated file system is supported, the operating system depends on constant RAM refresh cycles to keep its memory. The OS supports 160x160 monochrome output displays. User input is generated through the Graffiti handwriting recognition system or optionally through a virtual keyboard. The system supports data synchronization to another PC via its HotSync technology over a serial interface. The latest bugfix release is version 1.0.7. Palm OS 2.0 Palm OS 2.0 was introduced on March 10, 1997 with the PalmPilot Personal and Professional. This version adds TCP/IP network, network HotSync, and display backlight support. The last bugfix release is version 2.0.5. Two new applications, Mail and Expense are added, and the standard PIM applications have been enhanced. Palm OS 3.0 Palm OS 3.0 was introduced on March 9, 1998 with the launch of the Palm III series. This version adds IrDA infrared and enhanced font support. This version also features updated PIM applications and an update to the application launcher. Palm OS 3.1 adds only minor new features, like network HotSync support. It was introduced with the Palm IIIx and Palm V. The last bugfix release is version 3.1.1. Palm OS 3.2 adds Web Clipping support, which is an early Palm-specific solution to bring web-content to a small PDA screen. It was introduced with the Palm VII organizer. Palm OS 3.3 adds faster HotSync speeds and the ability to do infrared hotsyncing. It was introduced with the Palm Vx organizer. Palm OS 3.5 is the first version to include native 8-bit color support. It also adds major convenience features that simplify operation, like a context-sensitive icon-bar or simpler menu activation. The datebook application is extended with an additional agenda view. This version was first introduced with the Palm IIIc device. The latest bugfix release is version 3.5.3. As a companion, Palm later offered a Mobile Internet Kit software upgrade for Palm OS 3.5. This included Palm's Web Clipping software, MultiMail (which was later renamed to VersaMail) Version 2.26 e-mail software, handPHONE Version 1.3 SMS software, and Neomar Version 1.5 WAP browser. Palm OS 4.0 Palm OS 4.0 was released with the new Palm m500 series on March 19, 2001. This version adds a standard interface for external file system access (such as SD cards). External file systems are a radical change to the operating system's previous in-place execution. Now, application code and data need to be loaded into the device's RAM, similar to desktop operating system behavior. A new Universal Connector with USB support is introduced. The previous optional Mobile Internet Kit is now part of the operating system. Version 4.0 adds an attention manager to coordinate information from different applications, with several possibilities to get the user's attention, including sound, LED blinking or vibration. 16-bit color screens and different time zones are supported. This version also has security and UI enhancements. Palm OS 4.1 is a bugfix release. It was introduced with the launch of the Palm i705. The later minor OS update to version 4.1.2 includes a backport of Graffiti 2 from Palm OS 5.2. Palm OS 4.2 Simplified Chinese Edition is targeted especially for the Chinese market with fully Simplified Chinese support, co-released with Palm OS 5.3. No device has been manufactured with this version up to now. Palm OS 5.0 Palm OS 5.0 was unveiled by the Palm subsidiary PalmSource in June 2002 and first implemented on the Palm Tungsten T. It is the first version to support ARM devices and replaced the Kadak AMX68000 kernel with the custom MCK kernel, named for its developer, that was written in-house by Palm. Applications written for the prior OS versions use the older DragonBall 68K instruction set and are supported via the Palm Application Compatibility Environment (PACE) emulator in Garnet. Even with the additional overhead of PACE, Palm applications usually run faster on ARM devices than on previous generation hardware. New software can take advantage of the ARM processors with small units of ARM code, referred to as ARMlets. With a more powerful hardware basis, Palm OS 5 adds substantial enhancements for multimedia capabilities. High density 320x320 screens are supported together with a full digital sound playback and record API. Palm's separate Bluetooth stack is added together with an IEEE 802.11b Wi-Fi stack. Secure network connections over SSL are supported. The OS can be customized with different color schemes. For Palm OS 5, PalmSource developed and licensed a web browser called PalmSource Web Browser based on ACCESS' NetFront 3.0 browser. Palm OS 5.2 is mainly a bugfix release, first implemented in the Samsung SGH-i500 in March 2003. It added support for 480x320 resolutions and introduced the new handwriting input system called Graffiti 2; the new input system was prompted by Xerox' lawsuit win against Palm. Graffiti 2 is based on Jot from CIC. The last bugfix release is version 5.2.8. Palm OS 5.3 Simplified Chinese Edition released in September 2003, added full Simplified Chinese support, further support for QVGA resolutions, and a standard API for virtual Graffiti called Dynamic Input Area. This version first shipped on Lenovo's P100 and P300 handhelds. Palm OS Garnet (5.4) added updated Bluetooth libraries and support for multiple screen resolutions ranging from 160x160 up to 480x320. It first shipped on the Treo 650 in November 2004. This version also introduced the Garnet moniker to distinguish it from Palm OS Cobalt 6.0. The last bugfix release is version 5.4.9. Garnet OS 5.5 dropped the Palm moniker and, , is the current version developed by ACCESS. This version is dedicated for use inside the Garnet VM virtual machine. Garnet VM was announced and released by ACCESS in November 2007 as a core part of the Access Linux Platform and as an emulator allowing Nokia Internet Tablets to run applications written for the Garnet OS. In June 2010, ACCESS release Garnet VM version 6 (a.k.a. Garnet VM Beta 6 1.05b). Palm OS Cobalt Palm OS Cobalt (6.0) was the designated successor for Palm OS 5. It was introduced on February 10, 2004, but is no longer offered by ACCESS (see next section). Palm OS 6.0 was renamed to Palm OS Cobalt to make clear that this version was initially not designated to replace Palm OS 5, which adopted the name Palm OS Garnet at the same time. Palm OS Cobalt introduced modern operating system features to an embedded operating system based on a new kernel with multitasking and memory protection, a modern multimedia and graphic framework (derived from Palm's acquired BeOS), new security features, and adjustments of the PIM file formats to better cooperate with Microsoft Outlook. Palm OS Cobalt 6.1 presented standard communication libraries for telecommunication, Wi-Fi, and Bluetooth connectivity. Despite other additions, it failed to interest potential licensees to Palm OS Cobalt. Third-party OS enhancements Several licensees have made custom modifications to the operating system. These are not part of the official licensed version. Palm developed a Bluetooth API for external Bluetooth SDIO Cards for Palm OS 4.0 devices. The Bluetooth stack was later included in Palm OS 5 Palm added a virtual graffiti input area API especially for their Tungsten T3 device. This API was later superseded by the official Dynamic Input Area API in Palm OS 5.3. Palm added the Non-Volatile File System in Palm OS 5.4, and used Flash for storage instead of DRAM, preventing data-loss in the event of battery drain. However, this fundamentally changed the way programs were executed from the Execute-in-Place system that Palm OS traditionally used, and has been the source of many compatibility problems, requiring many applications to add explicit NVFS support for correct operation. For their camera-equipped devices, Palm added the CameraLib API. Sony added a library to support JogDial input available on their CLIÉ organizers. Modernization For several years, PalmSource had been attempting to create a modern successor for Palm OS 5 and have licensees implement it. Although PalmSource shipped Palm OS Cobalt 6.0 to licensees in January 2004, none adopted it for release devices. PalmSource made major improvements to Palm OS Cobalt with the release of Palm OS Cobalt 6.1 in September 2004 to please licensees, but even the new version did not lead to production devices. In December 2004, PalmSource announced a new OS strategy. With the acquisition of the mobile phone software company China Mobilesoft, PalmSource planned to port Palm OS on top of a Linux kernel, while still offering both Palm OS Garnet and Palm OS Cobalt. This strategy was revised in June 2005, when still no device with Palm OS Cobalt was announced. PalmSource announced it was halting all development efforts on any product not directly related to its future Linux based platform. With the acquisition of PalmSource by ACCESS, Palm OS for Linux was changed to become the Access Linux Platform which was first announced in February 2006. The initial versions of the platform and software development kits for the Access Linux Platform were officially released in February 2007. As of January 2011, the Access Linux Platform had then yet to ship on any devices, however development kits then existed and public demonstrations had been showcased. Palm, Inc. the main licensee of Palm OS Garnet did not license Access Linux Platform for their own devices. Instead, Palm developed another Linux-based operating system called Palm webOS. On February 11, 2009, Palm CEO Ed Colligan said there would be no additional Palm OS devices (excepting the Centro being released to other carriers). Palm was focusing on Palm webOS and Windows Mobile devices. On April 1, 2009, Palm announced the availability of a Palm OS emulator for its webOS. Built-in applications Palm OS licensees decide which applications are included on their Palm OS devices. Licensees can also customize the applications. Standard Palm OS applications Note: On the newer models, the standard PIM apps "Address", "Date Book", "Memo Pad" and "ToDos" were replaced by their improved counterparts "Contacts", "Calendar" "Memos" and "Tasks". The Palm's Address program stores contact information, keyed by any of several user-definable categories. Entries are displayed and sorted in last name, first name order (this can be changed only to Company, Last Name order). There are five slots for phone or e-mail, each of which may be designated Work, Home, Fax, Other, E-mail, Main, Pager or Mobile (the slot designations cannot be changed) The newer Contacts app adds the following features: several addresses, 9 new fields: Website, Birthday, More phone numbers, Instant Messaging with quick connect. Calc turns the Palm into a standard 4-function pocket calculator with three shades of purple and blue buttons contrasting with the two red clear buttons. It supports square root and percent keys and has one memory. It also has an option to display a running history of the calculations, much like the paper-tape calculators that were once common. Date Book shows a daily or weekly schedule, or a simple monthly view. The daily schedule has one line per hour, between user-selected begin and end times. Clicking on an empty line creates a new event. Empty lines are crowded out by actual events, whose start and stop times are shown by default bracketed in the left margin. The newer Calendar app adds the following features: New Day view, use of categories for events, event location, event can span midnight, event details, birthdays as timeless events. It supports time zone designation for events, a feature lacking in some more recent competitors. An event, or appointment, can be heralded by an alarm, any number of minutes, hours or days before it begins. These alarms sound even when the unit is switched off. Appointments can recur in a specified number of days, weeks, months or years and can contain notes. Expense tracks common business expenses. No totals are calculated on the Palm. The user must sync with a host computer and view the expense data in a worksheet (templates for Microsoft Excel are supplied). HotSync integrates with the user's PC. Usually activated by a press of the physical HotSync button on the Palm's cradle (a dock station), this application communicates with various conduits on the desktop PC to install software, backup databases, or merge changes made on the PC or the handheld to both devices. It can communicate with the PC through a physical connection (USB on newer models), Bluetooth or IrDA wireless connections, and direct network connections on devices with networking capability. In addition to the conduits provided by the licensee, developers can create their own conduits for integration with other Palm OS applications and desktop products. For example, a time tracking package could provide a conduit to communicate information between Palm OS and Windows executables. A Backup conduit included with the HotSync software backs up (and restores, if necessary) most of the data on a Palm OS device. This allows users to hard reset their Palm—thus clearing all of the data—with few noticeable consequences. This also allows users to migrate to new Palm devices of the same Palm OS version, a feature that is helpful to those who lose or damage their device. Some models of Palm keep their data storage in volatile memory and require constant power to maintain their memory. Although these handhelds attempt to save the contents of memory in low battery situations by not "turning on," leaving a "dead" handheld for an extended period of time can cause this reserve power to be used up and the contents of storage memory to be lost. Some later Palms use NVRAM or microdrive for storage. Memo Pad can hold notes of up to 4,000 characters each; the newer Memos app increases field size from 3 to 30 kB. Memos are ordered in two ways: alphabetically, and manually (which allows the user to choose the order of the memos), and memos can be grouped in user-configurable categories. Memo Pad is for text only, not for drawings, and text can be entered using the Graffiti alphabet, using hardware or software keyboards, or using the 'paste' function. When Palm devices first became available, some Palm users started to create and exchange Memo Pad documents containing generally useful information, which came to be known as Memoware. To do list creates personal reminders and prioritizes the things the user has to do. Each To Do List item may also have: a priority, categories (to organize and view items in logical groups), attached Note (to add more description and clarification of the task). To Do List item can be sorted by: due date, priority or category The newer Tasks app features the following improvements: new interface, repeating tasks, alarms, etc. Preferences (also referred to as Prefs) shows program files with a special preference panel type which are not shown by the normal launcher. Programs can be changed by switching the type to and vice versa. Palm OS contains approximately 15 preference panels by default and new preference panels can be added just like any other application. Preference panels allow users to manage a number of settings, including Graffiti settings, sound settings, text shortcuts, network settings and the system time. Security (which is a panel on newer Palm OS devices) is used to configure Palm OS's security settings. These include the password needed to display hidden records and unlock the device when locked, as well as set up an automatic lockdown time or inactivity threshold. On the PC, only Palm Desktop honors this password but other PC programs can view everything—in other words, all the data protected by this password can be seen by anyone opening the .dat files using a text editor or word processor. Common third-party core OS applications Starting with Palm OS version 5.2, Palm created customized versions of the common PIM application. Some new features have been added, e.g. support for Address categories, Ringtone associations to users, longer memo texts, etc.. They were also renamed to reflect designations from Microsoft Outlook, thus Address became Contacts, Datebook became Calendar, Memo Pad became Memos and To do list became Tasks. Blazer is a web browser for Palm handhelds. The versions 1.0 and 2.0 run on Palm OS 3.1 or higher handhelds, but they needed a proxy server which has been shut down, so they can no longer be used. Version 3.0 is used on the Treo 600 smartphone. The current version of Blazer is Blazer 4.5, which is compliant with most major standards. It is generally bundled with newer smartphones and newer Palm devices capable of accessing the Internet. Palm's Note Pad can be used for quick drawings. With neat handwriting, 20–30 words will fit on one page; for more text, Memo Pad is the better choice. There are three sizes of pen width, plus an eraser and a background color change feature in some models. It is possible to draw a very simple map. The more "advanced" desktop version saves the Memo pad drawings to the desktop. As of 2006, most new Palm handhelds include Photos, which creates a digital photo album used to view pictures on a Palm OS device. As with all the other photo programs, photos can be beamed to other mobile devices. Each photo can be labeled and organized into separate photo albums. A slideshow can also be shown for a specific album, and each photo in the album will be shown full screen. Photos can be edited with the Palm Photos PC software (Windows only), and when the photos are transferred to the handheld they will contain all changes made to the photo. The Palm Photos software is available in the Zire 71, Tungsten C, Tungsten E, Tungsten T2, Tungsten T3 and several others. With the support for Video, Palm Photos was later renamed to Media and even later to Pics& Videos. Some models feature the ability to make voice recordings which are synced using the Voice conduit and can be viewed on a desktop with the Voice Memo application which is part of the Palm Desktop Suite. Third-party applications There are many successful applications that can be installed on a Palm OS device. As of 2008, there were more than 50,000 third-party applications available for the Palm OS platform, which have various licensing types, including open-source, and various closed licensing schemes such as freeware, shareware, and traditional pay-up-front purchase. HackMaster is an extension manager for Palm OS that includes several patches improving OS features. Other third party OS extensions also require HackMaster to work. Application development Palm OS Garnet applications are primarily coded in C/C++. Two officially supported compilers exist: a commercial product, CodeWarrior Development Studio for Palm OS, and an open source tool chain called prc-tools, based on an old version of gcc. CodeWarrior is criticized for being expensive and is no longer being developed, whereas PRC-Tools lacks several of CodeWarrior's features. A version of PRC-Tools is included in a free Palm OS Developer Suite (PODS). OnBoardC is a C compiler, assembler, linker and programming editor that runs on the Palm itself. Palm OS Cobalt applications are also coded in a variation of gcc, but the Cobalt compilers have fewer limitations. There are development tools available for Palm programming that do not require low-level programming in C/C++, such as PocketC/PocketC Architect, CASL, AppForge Crossfire (which uses Visual Basic, Visual Basic .NET, or C#), Handheld Basic, Pendragon Forms, Satellite Forms and NSBasic/Palm (Visual Basic like languages). A Java Virtual Machine was previously available for the Palm OS platform, however on 12 January 2008, Palm, Inc. announced that it would no longer be available. Palm, Inc. further said "There is no alternate Java Virtual Machine that we are aware of for Palm OS." Waba and a derivative of it, SuperWaba, provide a Java-like virtual machine and programming language. A version of the Lua language, called Plua, is also available for Palm; however, due to the fact that it requires an additional runtime to be installed along with the application, it is only used for mainstream applications by a minority of software companies. Quartus Forth is an ISO/ANSI Standard Forth compiler that runs on the Palm itself. It also has an interactive console for dynamic development and debugging. Three environments allow programming in Pascal for Palm OS. The free PP Compiler runs directly on the handheld computer, while PocketStudio is a Delphi-like IDE for Windows Computers that has a visual form designer and generates PRC files for being transferred to handhelds via HotSync. The third option was HSPascal, developed by Danish developer Chriten Fihl, based on his experience with the High Speed Pascal compiler for various 16-bit computer systems, including the Commodore Amiga. As Palm has no connection drivers that enable the transfer of data with a server DBMS (Oracle, mySQL, MS SQL Server), the programmer can use Middleware software that enables this connectivity. A roughly R4RS-compatible implementation of Scheme, LispMe, provides the Palm platform with a GPL-licensed onboard Lisp REPL with some Palm OS-specific adaptations, but although it is functionally a compiler it does not produce code that operates outside the development environment, so its use is restricted to prototyping. Legal issues Palm OS has been involved in various lawsuits over the years. Xerox vs. Palm Computing (1997) – In 1997, Xerox was granted covering the "Unistroke" input system developed by David Goldberg, Xerox PARC in 1993. Xerox filed suit against Palm (then U.S. Robotics), alleging that Palm's Graffiti infringed on this patent. The Palm OS switch from Graffiti 1 to Graffiti 2 was triggered in part by Palm losing this lawsuit to Xerox. The patent was invalidated in May 2004 due to prior art developed at Bell Laboratories in 1982. Pilot Pen Corporation vs. Palm Computing (1998) – The original name for Palm OS handhelds was Pilot. However, a lawsuit from Pilot Pen Corporation forced a name change to PalmPilot, then eventually to Palm. Palm vs. Microsoft (1998) – In 1998, Microsoft planned to name the next version of their handheld computing platform "Palm PC". Palm filed suit against Microsoft, forcing the name change to, first, Palm-sized PC, and later, Pocket PC. E-Pass Technologies vs. Palm, Microsoft and HP (2000) – In 2000, E-Pass Technologies filed suit against Palm, alleging that its handhelds infringed on an E-Pass's patent (#5,276,311) for a multi-function, credit card-sized computer that allows users to securely store account numbers, PIN codes, etc. NCR vs. Handspring and Palm (2001) – In 1987, NCR was granted a patent for a portable e-commerce terminal. In 2001, NCR sued Handspring and Palm. This case was ruled without merit in 2002, a decision that was upheld on appeal. RIM vs. Handspring (2002) – In 2002, Research In Motion (makers of the BlackBerry), sued Handspring. By year end, both Handspring and Palm licensed the patents and the suit was dropped. Peer-to-Peer Systems vs. Palm (2002) – Also in 2002, Peer-to-Peer systems filed lawsuit against Palm that alleges Palm infringed on its patent for wireless gaming. This lawsuit was settled as of February 9, 2005. Forgent Networks vs. HP, Toshiba, palmOne, etc., etc. (2004) – Starting in 2002, Forgent Networks began offering licenses for a patent that encumbers JPEG. In 2004, it filed suit against various companies, including palmOne. The JPEG or 672 patent has been reviewed by the U.S. Patent and Trademark Office, which has rejected 19 of the 47 claims based on prior art. See also Access Linux Platform, planned successor of the Palm OS Graffiti (Palm OS) List of Palm OS devices, includes emulators Memoware Palm, Inc. Palm Desktop Palm webOS PalmSource, Inc. References External links Palm.com Palm OS 4.1 Screenshots PalmDB – Archive for Palm OS Software Preservation Palm OS Wiki – Palm OS Knowledge & History Preservation Wiki ARM operating systems Computer-related introductions in 1996 Discontinued operating systems Embedded operating systems Mobile operating systems Personal digital assistants

Operating System (OS)

Java Desktop System Java Desktop System, briefly known as OpenSolaris Desktop, is a legacy desktop environment developed first by Sun Microsystems and then by Oracle Corporation after the 2010 Oracle acquisition of Sun. Java Desktop System is available for Solaris and was once available for Linux. The Linux version was discontinued after Solaris was released as open source software in 2005. Java Desktop System aims to provide a system familiar to the average computer user with a full suite of office productivity software such as an office suite, a web browser, email, calendaring, and instant messaging. Despite being known as the Java Desktop System, it is not actually written in Java. Rather, it is built around a tweaked version of GNOME along with other common free software projects, which are written mostly in C and C++. The name reflected Sun's promotion of the product as an outlet for corporate users to deploy software written for the Java platform. Versions Sun first bundled a preview release of GNOME 1.4 on a separate CD for Solaris 8. JDS version 2 included: Java GNOME (using the Blueprint theme) StarOffice Mozilla Evolution MP3 and CD player Java Media Framework's Java Media Player Gaim multi-service instant messaging RealPlayer JDS Release 2 was available for Solaris and for the SuSE-based Linux distribution. JDS Release 3 was released in 2005. It was included with Solaris 10 — upon installation of Solaris, one has the choice of using either the CDE or JDS. It was based on GNOME 2.6 and available only for the Solaris 10 platform. OpenSolaris Desktop OpenSolaris received its own version of the Java Desktop System. OpenSolaris Desktop was tied to the OpenSolaris operating system, and did not have its own release schedule. OpenSolaris Desktop 01 (released October 28, 2005) was based on GNOME 2.10 and OpenSolaris Desktop 02 (released December 23, 2005) was based on GNOME 2.12. The last version was released with the release of OpenSolaris 2009.6, and was based on Gnome 2.24. It also included Firefox 3.1, OpenOffice 3 and Sun VirtualBox. The OpenSolaris Desktop line of the Java Desktop System became defunct with the end of the OpenSolaris project. Availability With the end of the OpenSolaris project, JDS Release 3 is now the last release of the project on a currently supported operating system Solaris 10. Newer Solaris based operating systems have abandoned the Java Desktop System. Solaris 11 and projects based upon the OpenSolaris codebase such as OpenIndiana use a stock version of GNOME. See also Project Looking Glass References External links Oracle Documentation OS News review December 2003 eWeek Review December 2003 Desktop environments Java platform software Oracle software Sun Microsystems software Desktop environments based on GTK Free desktop environments GNOME Software forks

Operating System (OS)

Linux on IBM Z Linux on IBM Z (or Linux on Z for short, and previously Linux on z Systems) is the collective term for the Linux operating system compiled to run on IBM mainframes, especially IBM Z and IBM LinuxONE servers. Similar terms which imply the same meaning are Linux on zEnterprise, Linux on zSeries, Linux/390, Linux/390x, etc. The three Linux distributions certified for usage on the IBM Z hardware platform are Red Hat Enterprise Linux (developed by the IBM subsidiary, Red Hat), SUSE Linux Enterprise, and Ubuntu. History Linux on IBM Z originated as two separate efforts to port Linux to IBM's System/390 servers. The first effort, the "Bigfoot" project, developed by Linas Vepstas in late 1998 through early 1999, was an independent distribution and has since been abandoned. IBM published a collection of patches and additions to the Linux 2.2.13 kernel on December 18, 1999, to start today's mainline Linux on Z. Formal product announcements quickly followed in 2000, including the Integrated Facility for Linux (IFL) engines. Think Blue Linux was an early mainframe distribution consisting mainly of Red Hat packages added to the IBM kernel. Commercial Linux distributors introduced mainframe editions very quickly after the initial kernel work. At the start of IBM's involvement, Linux patches for IBM Z included some object code only (OCO) modules, without source code. Soon after IBM replaced the OCO modules with open source modules. Linux on Z is free software under the GNU General Public License. According to IBM, by May, 2006, over 1,700 customers were running Linux on their mainframes. Virtualization Virtualization is required by default on IBM Z; there is no option to run Linux on Z without some degree of virtualization. (Only the very first 64-bit mainframe models, the z900 and z800, included a non-virtualized "basic mode.") First layer virtualization is provided by the Processor Resource and System Manager (PR/SM) to deploy one or more Logical Partitions (LPARs). Each LPAR supports a variety of operating systems including Linux on IBM Z. A hypervisor called z/VM can also be run as the second layer virtualization in LPARs to create as many virtual machines (VMs) as there are resources assigned to the LPARs to support them. KVM on z is another hypervisor option. When Linux applications in an LPAR access data and applications in other LPARs such as CICS, IBM Db2, IMS, Linux, and other mainframe subsystems running on the same physical mainframe, they can utilize HiperSockets – fast, memory-only TCP/IP connections. As compared to TCP/IP over standard network interface cards (NICs, also known as Open System Adapters (OSAs) in mainframes), HiperSockets can improve end-user responsiveness (reduce network latency and processing overhead), security (since there's no network connection to intercept), and reliability (since there's no network connection to lose). With the zEC12, zBC12, and later models, the HiperSocket concept is extended beyond the physical machine boundary via an RDMA over Converged Ethernet (RoCE) adapter to facilitate a secure and high speed inter-system communication. Applications in LPAR A in system A can thus use HiperSockets to communicate with applications in LPAR B in system B to ensure the security and performance attributes. Hardware Beginning with Linux kernel version 4.1 released in early 2015, Linux on Z is only available as a 64-bit operating system compatible with z/Architecture mainframes. Previously Linux on Z was also available as a 31-bit operating system compatible with older model mainframes introduced prior to 2000's z900 model. However, the newer 64-bit Linux kernel and 64-bit Linux on Z distributions are still backward compatible with applications compiled for 31-bit Linux on Z. Historically the Linux kernel architecture designations were "s390" and "s390x" to distinguish between the 31-bit and 64-bit Linux on Z kernels respectively, but "s390" now also refers generally to the one Linux on Z kernel architecture. Linux runs on standard, general purpose mainframe CPs (Central Processors) as well as IFLs (Integrated Facility for Linux). IFLs are mainframe processors dedicated to running Linux, either natively or under a hypervisor (z/VM or KVM on z). Microcode restricts IFLs from running "traditional" workloads, such as z/OS, but they are physically identical to other IBM Z processors. IFLs are typically less expensive to acquire from IBM than CPs. Advantages Linux on Z gives the flexibility of running Linux with the advantages of fault-tolerant mainframe hardware capable of over 90,000 I/O operations per second and with a mean time between failure (MTBF) measured in decades. Using virtualization, numerous smaller servers can be combined onto one mainframe, gaining some benefits of centralization and cost reduction, while still allowing specialized servers. Instead of paravirtualization, IBM mainframes use full virtualization, which permits workload density far greater than paravirtualization does. Combining full virtualization of the hardware plus lightweight Virtual Machine containers that run Linux in isolation (somewhat similar in concept to Docker) result in a platform that supports more virtual servers than any other in a single footprint, which also can lower operating costs. Additional savings can be seen from reduced need for floor space, power, cooling, networking hardware, and the other infrastructure needed to support a data center. IBM mainframes allow transparent use of redundant processor execution steps and integrity checking, which is important for critical applications in certain industries such as banking. Mainframes typically allow hot-swapping of hardware, such as processors and memory. IBM Z provides fault tolerance for all key components, including processors, memory, I/O Interconnect, power supply, channel paths, network cards, and others. Through internal monitoring, possible problems are detected and problem components are designed to be switched over without even failing a single transaction. In the rare event of failure, firmware will automatically enable a spare component, disable the failing component, and notify IBM to dispatch a service representative. This is transparent to the operating system, allowing routine repairs to be performed without shutting down the system. Many industries continue to rely on mainframes where they are considered to be the best option in terms of reliability, security, or cost. Pricing and costs Linux on Z is not generally appropriate on-premises for small businesses that would have fewer than about 10 distributed Linux servers, although some expensive per-processor licensed software can quickly reduce that rule of thumb. Most software vendors, including IBM, treat the highly virtualized IFLs just like non-virtualized processors on other platforms for licensing purposes. In other words, a single IFL running scores of Linux instances still typically counts as one "ordinary" CPU, at the same CPU price, for software licensing. Test, development, quality assurance, training, and redundant production server instances can all run on one IFL (or more IFLs, but only if needed for peak demand performance capacity). Thus, beyond some minimum threshold, Linux on Z can quickly become cost-advantageous when factoring in labor and software costs. The cost equation for Linux on Z is not always well understood and is controversial, and many businesses and governments have difficulty measuring, much less basing decisions on, software, labor, and other costs (such as the costs of outage and security breaches). Acquisition costs are often more visible, and small, non-scalable servers are "cheap." Nonetheless, non-acquisition costs are no less real and are usually far greater than hardware acquisition prices. Also, individual users and departments within larger businesses and governments sometimes have difficulty sharing computing infrastructure (or any other resources, for that matter), citing a loss of control. Server centralization, as Linux on Z provides, might reward cooperation with better service and lower costs, but that's not to say that cooperation is always easily accomplished within a corporate bureaucracy. Linux on Z also supports less expensive disk storage devices than z/OS because Linux does not require FICON or ESCON attachment, although z/OS may use disk space more efficiently, on balance, due to hardware-assisted database compression common on z/OS and the smaller number of operating system instances z/OS typically requires. There are also some operational advantages using some FICON-attached storage with Linux on Z, for example support for z/VM Live Guest Relocation. Appropriate workloads Mainframe characteristics are designed for such business workloads as transaction processing (especially in conjunction with concurrent, high volume batch processing) and large database management. Mainframe design traditionally emphasizes "balanced" performance for all computing elements including input/output, implemented via channel I/O. Mainframes offload I/O, system accounting, and other non-core computing tasks from the main CPUs as much as possible, and z/Architecture additionally offloads cryptographic calculations. For example, in a single IBM z13 machine up to 141 processor cores are available to configure as IFLs. However, every such machine also has 27 additional main cores: 2 as spares, 1 for firmware support, and the remainder running system accounting and I/O support tasks. In addition, each I/O adapter typically has two PowerPC processors, and a z13 supports hundreds of I/O adapters. There are also separate processors handling memory and cache control tasks, environmental monitoring, and internal interconnections, as examples. Historically, mainframes in general, and Linux on Z in particular, did not execute "CPU-intensive" single task computations with notably high performance compared to certain other platforms with a few notable exceptions such as cryptographic calculations. Examples included most scientific simulations, weather forecasting, and molecular modeling. Supercomputers, including Linux-based supercomputers, excel at these workloads. This bifurcation between mainframes and other platforms has significantly blurred in recent years, starting with the introduction of 2008's System z10, a machine based on quad-core 4.4 GHz processors with hardware decimal floating point. As mainframe processor technology has continued to evolve, and especially with the introduction of the IBM LinuxONE and IBM z13 models in 2015, IBM has started promoting its mainframes as ideal platforms to run real-time analytics and other computationally intensive tasks that mainframes did not historically run well. Mainframes do not provide graphics or sound adapters, and are as such ill-suited for digital media editing or computer-aided design (CAD) except perhaps in support roles (e.g. content storage, parts inventories, metadata management, security services, etc.) Support Like all other versions of Linux, Linux on Z is governed by the GPL free software license. Complete Linux on Z source code is available from numerous parties on a free and equal basis, and architectural support is part of the main Linux kernel effort. IBM assigns several of its programmers to the community effort, but IBM is by no means the only participant. Though there are no obstacles to running any Linux on Z distribution on an IBM z System, IBM routinely tests three particular Linux on Z distributions: Red Hat, SUSE, and starting in 2015, Canonical's Ubuntu Linux. Other notable Linux on Z distributions include Debian (upstream for Ubuntu), Fedora (upstream for RHEL), Slackware, CentOS, Alpine Linux and Gentoo. Nearly every free or open-source software package available for Linux generally is available for Linux on Z, including Apache HTTP Server, Samba software, JBoss, PostgreSQL, MySQL, PHP, Python programming language, Concurrent Versions System (CVS), GNU Compiler Collection (GCC), LLVM, and Perl, Rust, among many others. Red Hat and SUSE offer mainline support for their distributions running Linux on Z. In 2015 Canonical announced plans to offer official support for its distribution starting in early 2016. IBM Global Services also offers support contracts, including 24x7 coverage. Some standard Linux software applications are readily available pre-compiled, including popular closed-source enterprise software packages such as WebSphere, DB2 and Oracle databases and applications, SAP R/3, SAP ERP, and IBM's Java Developer's Kit (JDK), to name only a few. Developer resources IBM offers resources to developers wishing to target Linux for z: The Linux Test Drive, a free program granting a single Linux on IBM Z virtual machine for 30 days. The IBM Systems Application Advantage for Linux (Chiphopper), a developer program to help developers write and publish cross-platform Linux software. The Community Development System for Linux on IBM Z (CDSL) program, a platform for providing open source developers a platform for porting to Linux on System z. The Linux Remote Development Program, a fee-based extended developer support program. Linux on Z supports Unicode and ASCII just like any other Linux distribution—it is not an EBCDIC-based operating system. However, for convenience Linux is able to read kernel parameters in EBCDIC. z/VM takes advantage of this capability. Porting Linux applications to Linux on Z is fairly straightforward. Potential issues include endianness (Linux on Z is big-endian) and reliance on non-portable libraries particularly if source code is not available. Programs can be easily cross compiled to z/Architecture binaries on non-mainframe Linux systems. Emulators There are at least three software-based IBM Z mainframe emulators. FLEX-ES from Fundamental Software is a commercially offered option, limited to 31-bit addressing. The open source Hercules emulator supports Linux on IBM Z (and can even run on Linux on System z itself). In 2010, IBM introduced the Rational Developer for System z Unit Test Feature (now called Rational Development and Test Environment for z, or sometimes RDTz for short) which provides a restricted use execution environment that can run on X86 hardware. IBM's license terms limit use of RDTz to certain application development tasks, not including final pre-production compiling or pre-production testing (such as stress testing). RDTz includes z/OS (with common middleware) and is also compatible with Linux on Z. See also Comparison of Linux distributions IBM Secure Service Container OpenSolaris for System z Linux on Power UNIX System Services zIIP zAAP z/TPF z/VSE References External links Linux on IBM Z IBM LinuxONE servers Open Mainframe Project Linux on z/VM Linux on IBM Z developer site Linux for S/390 and zSeries community wiki Linux for S/390 and zSeries web site linux-390, users mailing list linux-s390, kernel devel mailing list IBM Redbooks for Linux on IBM Z technical know-how The Virtualization Cookbook for Linux on Z covering Red Hat Enterprise Linux (REL), SUSE Linux Enterprise Server (SLES), and Ubuntu Server Porting GCC to the IBM S/390 platform Platform-specific Linux distributions IBM mainframe operating systems VM (operating system) Linux distributions

Operating System (OS)

Knoppix KNOPPIX ( ) is an operating system based on Debian designed to be run directly from a CD / DVD (Live CD) or a USB flash drive (Live USB), one of the first of its kind for any operating system. Knoppix was developed by, and named after, Linux consultant Klaus Knopper. When starting a program, it is loaded from the removable medium and decompressed into a RAM drive. The decompression is transparent and on-the-fly. Although KNOPPIX is primarily designed to be used as a Live CD, it can also be installed on a hard disk like a typical operating system. Computers that support booting from USB devices can load KNOPPIX from a live USB flash drive or memory card. There are two main editions: the traditional compact-disc (700 megabytes) edition and the DVD (4.7 gigabytes) "Maxi" edition. The CD edition had not been updated since June 2013 until recently. As of version 9.1, CD images are being released once again. Each main edition has two language-specific editions: English and German. KNOPPIX mostly consists of free and open source software, but also includes some proprietary software, as long as it fulfills certain conditions. Knoppix can be used to copy files easily from hard drives with inaccessible operating systems. To quickly and more safely use Linux software, the Live CD can be used instead of installing another OS. Contents More than 1000 software packages are included on the CD edition, and more than 2600 packages are included on the DVD edition. Up to nine gigabytes can be stored on the DVD in compressed form. These packages include: LXDE, a lightweight X11 desktop environment; default since Knoppix 6.0 and later MPlayer, with MP3 audio, and Ogg Vorbis audio playback support Internet access software, including the KPPP dialer and ISDN utilities The Iceweasel web browser (based on Mozilla Firefox) The Icedove e-mail client (based on Mozilla Thunderbird) GIMP, an image manipulation program Tools for data rescue and system repair Network analysis and administration tools LibreOffice, a comprehensive office suite Terminal server Hardware requirements Minimum hardware requirements for Knoppix: Intel/AMD-compatible processor (i486 or later) Minimum RAM memory requirements: 32 MB for text mode; Live environment with no swap: 512 MB for graphics mode with just LXDE 1 GB to use the web browser and productivity software 2 GB recommended Bootable optical drive: DVD-ROM for current versions; CD-ROM for version 7.2 and older, or a boot floppy and standard CD-ROM (IDE/ATAPI or SCSI) Standard SVGA-compatible graphics card Serial or PS/2 standard mouse, or an IMPS/2-compatible USB-mouse. Saving changes in the environment Prior to Knoppix 3.8.2, any documents or settings a user created would disappear upon reboot. This lack of persistence then made it necessary to save documents directly to a hard drive partition, over the network, or to some removable media, such as a USB flash drive. It was also possible to set up a "persistent home directory", where any documents or settings written to the user's home directory would automatically be redirected to a hard drive or removable media, which could be automatically mounted on bootup. A single file, knoppix.img, was cached on the rewritable media and used to simulate a file system into which files were written for later use. This allowed the user to transparently write to their home directory. Union mount support was added in version 3.8.1 through UnionFS. This was later replaced by Aufs in 5.1.0 to improve stability. The union mount allowed virtual updates to the data on the read-only CD/DVD media by storing changes on separate writable media and then representing the combination of the two as single storage device. The writable media could be memory (ramdisk), a hard disk, USB flash drive, etc. This means that the user could modify the software installed on the Knoppix system, such as by using APT to install or update software. The storage device containing the changes needed to be present whenever Knoppix is started, else only the original data from the disc would be used. While Knoppix would scan available storage devices for a persistent home directory by default, a user could dictate a specific location with a boot option (see below) such as: home=/dev/hda1/knoppix.img By carrying a Knoppix CD and a USB flash drive, a user could have the same environment, programs, settings, and data available on any computer that could run Knoppix. This functionality was only available through Knoppix 5.1.1 (CD release) or 5.3.1 (DVD release). Subsequently, the Live CD paradigm has transformed into portable operating systems that run on external storage. Boot options When using Knoppix as a Live CD, one can use boot options, also known as 'cheatcodes', to override a default setting or automatic hardware detection when it fails. For example, the user may wish to boot into a plain console, or proceed without SCSI support. For this, Knoppix allows the user to enter one or more cheat codes at the prompt before booting. If the user does not enter a cheat code, or does not press any key before the timeout, Knoppix will boot with its default options. For example, to set the language to French rather than the default, one would type: knoppix lang=fr Knoppix is a 32-bit Debian Linux based distro, but recent releases (including the latest version 7.6) have also been equipped with a 64-bit kernel on the DVD edition, where it will automatically boot up for 64-bit computers, or by using the boot option knoppix64 manually in the command-line prompt, while knoppix will boot up the 32-bit kernel. Neither PAE nor 64-bit applications are supported by Knoppix, and system memory with more than 4 GB can only be used with a 64-bit kernel. The DVD edition of Knoppix can also be loaded onto a USB flash drive, with flash-knoppix under the Knoppix system, such that "the KNOPPIX Live System starts and runs about factor 5 faster from USB flash disk than from CD or DVD!". Besides that, the experimental UEFI support is provided for USB flash drive rather than DVD media. 32-bit UEFI firmware can only boot up the 32-bit kernel, while 64-bit UEFI firmware can only boot up the 64-bit kernel. The text interface for UEFI is similar with it for BIOS, one can also press key F2 and F3 to access information on boot options. Popularity Knoppix was one of the first Live CD Linux distributions to gain popularity. There are several factors that contribute to the popularity of Knoppix: Knoppix was one of the first Live CDs available, and is known as the "original" Debian-based Live CD Its extensive hardware detection allows most systems to start Knoppix without any configuration Its ability to automatically connect to most kinds of networks Its utilities for system repair and troubleshooting Knoppix works on a fairly large number of PCs or laptops, but not all. The automatic hardware detection cannot cope with all hardware, and sometimes the drivers used will not be optimal. Knoppix has difficulty recognizing some cards made before 1998, or motherboards with a BIOS made before 2002. (In some cases, manual configuration with codes entered at boot time can overcome problems with automatic detection.) If a PC does not have enough RAM to run KDE and other included programs, the legacy Knoppix (earlier than 6.0) boots up a very limited twm session instead. The only window running in the twm session by default is xterm. Versions The table (to the right) shows the version history of major releases. Knoppix 4.x–5.x As of April 2008, from version 4 up until 5.1.1, Knoppix has been split into a DVD "maxi" edition (with over 9 GB of software), and a CD "light" edition; both were developed in parallel. Up until Knoppix 5.1.1, the CD editions contained a selection of graphical environments, including the TWM window manager, and KDE 3 — a feature-complete desktop environment default in Knoppix 5.3.1 and earlier. No further development is being done on the traditional 5.x versions. Knoppix 6.x KNOPPIX 6.0.1 / ADRIANE 1.1 is a CD-edition again, and a complete rebuild from scratch. LXDE was made the default desktop environment, and the edition contains a substantially reduced software collection in order to easily fit on a CD. The KNOPPIX 6.2.1 release has both CD and DVD editions, and ADRIANE 1.2 only has a CD-edition. Knoppix 6.7.1 has the last CD version with stable touchpad drivers. Knoppix 7.x From June 2013 on until March 2019, Knoppix 7.2 was the most recent release with a CD edition. By 2018, its software had become very outdated, as the libc6 2.17 library no longer suffices for installation of several modern packages. The 7.x version range is known for instabilities with touchpads. Version 7.2 still remains the most recent CD version of Knoppix in wide distribution. Knoppix 8.x The KNOPPIX 8.0.0 edition was released at CeBIT 2017. KNOPPIX 8.1.0 was released in September 2017 as the first public release in the 8.x series. The version 8.0.0 has the dual boot, and a choice between three different desktops:LXDE as default option, KDE or GNOME. Versions 8.2.0 and newer (8.2.x, not 8.5.x) are available on Knoppix mirrors. Knoppix 8.5 was a DVD version that was not available for download, but was published as an exclusive version only bundled with a physical edition of Linux-Magazin or LinuxUser. Version 8.5 no longer includes Systemd, which was replaced by elogind. Spectre and Meltdown kernel vulnerabilities have been mitigated. Knoppix 8.6 (and newer) is a DVD version available for download on Knoppix mirrors. Derivatives Adriane Knoppix Adriane Knoppix is a variation that is intended for blind and visually impaired people, which can be used entirely without vision oriented output devices. It was released in the third quarter of 2007 as a Live CD. Adriane Knoppix is named after Adriane Knopper, the wife of Klaus Knopper, the developer of Knoppix. Adriane has a visual impairment, and has been assisting Klaus with the development of the software. The name Adriane is also a backronym for "Audio Desktop Reference Implementation And Networking Environment". Adriane Knoppix is intended not only for the blind but also for beginners who don’t know much about computers. It uses the SUSE Blinux screen reader with a phoneme generator and speech engine for normal output. Other variations Kali Linux, a live CD/USB distribution now based on Debian. It is a rewrite of BackTrack, which was based on Knoppix. Like its predecessors, Kali is designed for digital forensics and penetration testing. BackTrack itself merged the Auditor Security Collection and WHAX distros. Kanotix, a live distribution now based on Debian. KnoppMyth, a distro that attempts to make the Linux and MythTV installation as trivial as possible. Musix GNU+Linux, specifically for musicians. Poseidon Linux, a widely acclaimed distribution specifically geared for the scientific community. KnoppiXMAME, designed for playing MAME videogames PelicanHPC for clustering TechUSB, an automated computer distro produced by RepairTech, Inc. Unmaintained projects Sorted chronologically, in ascending order. See also Comparison of Linux distributions Debian Live Notes Books News article Distrowatch.com interview with Klaus Knopper (2002) References External links Debian-based distributions Live CD Live USB LiveDistro Operating system distributions bootable from read-only media Linux distributions without systemd Linux distributions

Operating System (OS)

Sintran Sintran (a portmanteau of SINTEF and Fortran; stylized as SINTRAN) is a range of operating systems (OS) for Norsk Data's line of minicomputers. The original version of Sintran, was written in the programming language Fortran, released in 1968, and developed by the Department of Engineering Cybernetics at the Norwegian Institute of Technology together with the affiliated research institute, SINTEF. The different incarnations of the OS shared only name, and to a degree, purpose. Norsk Data took part in developing Sintran II, a multi-user software system that constituted the software platform for the Nord-1 range of terminal servers. By far the most common version of the OS was Sintran III, developed solely by Norsk Data and launched in 1974. This real-time multitasking system was used for Norsk Data's server machines (such as the Nord-10, -100) for the remainder of the company's lifetime, i.e. until 1992. See also Sintran III Fortran software Proprietary operating systems Norsk Data software

Operating System (OS)

Mac OS X Snow Leopard Mac OS X Snow Leopard (version 10.6) is the seventh major release of macOS, Apple's desktop and server operating system for Macintosh computers. Snow Leopard was publicly unveiled on June 8, 2009 at Apple’s Worldwide Developers Conference. On August 28, 2009, it was released worldwide, and was made available for purchase from Apple's website and retail stores at the price of US$29 for a single-user license. As a result of the low price, initial sales of Snow Leopard were significantly higher than that of its predecessors whose price started at US$129. The release of Snow Leopard came nearly two years after the launch of Mac OS X Leopard, the second longest time span between successive Mac OS X releases (the time span between Tiger and Leopard was the longest). Unlike previous versions of Mac OS X, the goals of Snow Leopard were improved performance, greater efficiency and the reduction of its overall memory footprint. Apple famously marketed Snow Leopard as having "zero new features". Its name signified its goal to be a refinement of the previous OS X version, Leopard. Much of the software in Mac OS X was extensively rewritten for this release in order to take full advantage of modern Macintosh hardware and software technologies (64-bit, Cocoa, etc.). New programming frameworks, such as OpenCL, were created, allowing software developers to use graphics cards in their applications. It was also the first Mac OS release since System 7.1.1 to not support Macs using PowerPC processors, as Apple dropped support for them and focused on Intel-based products. As support for Rosetta was dropped in Mac OS X Lion, Snow Leopard is the last version of Mac OS X that is able to run PowerPC-only applications. Though the final release only supports Intel processors, two development builds that supported PowerPC processors are known to exist, builds 10A96 and 10A190. Snow Leopard was succeeded by OS X Lion (version 10.7) on July 20, 2011. For several years, Apple continued to sell Snow Leopard at its online store for the benefit of users that required Snow Leopard in order to upgrade to later versions of OS X. Snow Leopard was the last version of Mac OS X to be distributed primarily through optical disc, as all further releases were mainly distributed through the Mac App Store introduced in the Snow Leopard 10.6.6 update. Snow Leopard was the last release of Mac OS X to support the 32-bit Intel Core Solo and Intel Core Duo CPUs. Because of this, Snow Leopard still remained somewhat popular alongside OS X Lion, despite its lack of continued support, mostly because of its ability to run PowerPC-based applications. Snow Leopard was also the last release of Mac OS X to ship with a welcome video at first boot after installation. Reception of Snow Leopard was positive. System requirements Apple states the following basic Snow Leopard system requirements are: Mac computer with an Intel processor (IA-32). "Yonah" processors such as Core Solo and Core Duo can run only 32-bit applications; later x86-64 architecture processors such as Core 2 Duo, Core i5 and i7 are also able to run 64-bit applications. 1 GB of RAM 5 GB of free disk space DVD drive (also accessible via Remote Disc) or external USB or FireWire DVD drive for installation Additional requirements to use certain features: QuickTime H.264 hardware acceleration support requires an Nvidia GeForce 9400M, 320M, or GT 330M graphics card OpenCL requires a supported Nvidia or ATI graphics card Snow Leopard releases do not support PowerPC-based Macs (e.g., Power Macs, PowerBooks, iBooks, iMacs (G3-G5), all eMacs, plus pre-February 2006 Mac minis and the Power Mac G4 Cube), although PowerPC applications are supported via Rosetta, which is now an optional install. In 2020, two developer previews of Snow Leopard that are universal appeared on the Internet that can be booted on select G4 and G5 Power Macs with modification and patching. License Snow Leopard is available as an upgrade for Intel-based Macintosh computers. Single-user licenses and "family pack" licenses for up to five computers are available. For qualifying Mac computers bought after June 8, 2009, Apple offered a discounted price through its "up-to-date" program, provided that customers' orders were faxed or postmarked by December 26, 2009. The standalone retail version of Snow Leopard is marketed as being restricted to users of Mac OS X Leopard, while the recommended upgrade path from Apple for Mac OS X Tiger is through the "Mac Box Set", which includes Mac OS X Snow Leopard and the current versions of iLife and iWork. There are three licenses available. These licenses differ in their requirements for pre-installed versions of Mac OS X: Leopard Upgrade: requires that Mac OS X Leopard already be installed. If you have purchased an Upgrade for Mac OS X Leopard license, then subject to the terms and conditions of this License, you are granted a limited non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer as long as that computer has a properly licensed copy of Mac OS X Leopard already installed on it. A "Family Pack Upgrade for Mac OS X Leopard" license is also mentioned as a subset of the Leopard Upgrade. Single Use: places no restriction on which (if any) version of Mac OS X should already be installed. Used for the non-upgrade and Mac Box Set versions of Snow Leopard. Subject to the terms and conditions of this License ... you are granted a limited non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer at a time. Family Pack: identical to the Single Use license in this respect. It is not entirely clear which license is offered with the retail version of Snow Leopard. As noted above, Apple's website advertised this version as an "upgrade from Mac OS X Leopard for $29" and suggest that others upgrade using the Mac Box Set, implying the stand-alone retail version to be a "Leopard Upgrade" license. On the other hand, some Apple press materials appear to indicate that this version is, in fact, the "Single Use" license: The Snow Leopard single user license will be available for a suggested retail price of $29 (US) (emphasis added) However, even if the retail edition of Snow Leopard is in fact a "Leopard Upgrade", the company has acknowledged that there is no technical barrier in that edition preventing a direct upgrade from Mac OS X "Tiger". The Leopard Upgrade license explicitly applies to the Up-To-Date Program (US$9.95) for Macs bought between June 8 and December 26, 2009 and the installation discs provided through this program are clearly marked as upgrades unlike either of the retail editions. New or changed features Mac OS X Snow Leopard is intended to be a release aimed to refine the existing feature set, expand the technological capabilities of the operating system, and improve application efficiency. Many of the changes involve how the system works in the background and are not intended to be seen by the user. For example, the Finder application was completely rewritten in the Cocoa application programming interface. Despite significant changes in the software, users will experience almost no changes in the user interface. Snow Leopard includes the following changes: Mac App Store – An app marketplace built in the image of the iOS App Store. Released in version 10.6.6. Boot Camp now allows Windows partitions to read and copy files from HFS+ partitions. The new version also adds support for advanced features on Cinema Displays and a new command-line version of the Startup Disk Control Panel. The Finder has been completely rewritten in Cocoa to take advantage of the new technologies introduced in Snow Leopard. A much smaller OS footprint, taking up about 7 GB less space than Mac OS X Leopard. Some of the recovered disk space (~250 MB) is because printer drivers are now downloaded or installed only as needed, rather than being pre-installed. The default install only contains those drivers needed for existing printers and a small subset of popular printers. iChat enhancements include greater resolution video chats in iChat Theater and lowered upload bandwidth requirements. Microsoft Exchange support is now integrated into the Mail, Address Book, and iCal applications. However, only Microsoft Exchange 2007 is supported and customers using prior versions of Exchange must either upgrade or use Microsoft Entourage. Full multi-touch trackpad support has been added to notebooks prior to those introduced in October 2008. While the original MacBook Air and other early multi-touch trackpad enabled notebooks had support for some gestures, they were unable to use four-finger gestures. This limitation has now been removed in Snow Leopard. Preview can infer the structure of a paragraph in a PDF document. QuickTime X (version 10), the next release of QuickTime player and multimedia framework, has been completely rewritten into a full 64-bit Cocoa application and builds on the media technologies in Mac OS X, such as Core Audio, Core Video, and Core Animation, to deliver playback. Apple has redesigned the QuickTime user interface to resemble the full-screen QuickTime view in prior versions, where the entire window displays the video. The titlebar and playback controls fade in and out as needed. QuickTime X also supports HTTP live streaming and takes advantage of ColorSync to provide high-quality color reproduction. If Snow Leopard is installed on a Mac with an nVidia GeForce 9400M, 320M or GT 330M graphics card, QuickTime X will be able to use its video-decoding capabilities to reduce CPU load. Safari 4 features Top Sites, Cover Flow, VoiceOver, expanded standards support, and built-in crash resistance, which prevents browser crashes caused by plug-ins by running them in separate processes. Safari 4 is bundled with Snow Leopard but does not require it, as it is available for free for Mac OS X Tiger and Leopard as well as Windows. Time Machine connection establishment and backups are now much faster. VoiceOver has also been greatly enhanced in Snow Leopard. Reading of web pages is improved with Auto Web Spots — areas of a page automatically designated for quick access. On newer Apple portables, trackpad gestures can be used to control VoiceOver functions, including the "rotor" gesture first seen in VoiceOver for the iPhone 3GS, allowing for the changing of certain VoiceOver navigation options by rotating fingers on the trackpad. Braille Display support is also improved, with Bluetooth displays supported for the first time. Refinements to the user interface While the Finder was completely rewritten in Cocoa, it did not receive a major user interface overhaul. Instead, the interface has been modified in several areas to promote ease of use. These changes include: The "traffic light" titlebar controls are now slightly lighter in appearance and have less depth than they did in Mac OS X 10.5. Exposé can now display windows for a single program by left clicking and holding its icon in the dock. Windows are arranged in a new grid pattern. Contextual menus which come out of Dock icons now have more options and have a new look, with a semi-transparent charcoal background and white text. An option has been added to the Finder preferences that allows the user to modify search behavior. The default setting can be selected to (1) search the entire computer, (2) search only the current folder from which the search was initiated, or (3) perform the search based on the previously used scope. Dock Stacks, when viewed as a grid, allow viewing of a subfolder as a new stack, rather than launching a Finder window, in a manner similar to "tunnelling". When viewed as grids or lists, scroll-bars are provided to navigate folders with more items than the current screen resolution will accommodate, as the program does not scale the icons to show as many as possible the way it did in OS X 10.5. The default gamma has been changed from 1.8 to 2.2 to better serve the color needs of digital content producers and consumers. Windows can now be minimized directly onto their application's icon in the dock. Faster PDF and JPEG icon refreshes. When searching for a network, the AirPort menu-bar icon animates until it finds a network and shows network strength of available networks in the drop down menu. Prefixes for bytes are now used in strictly decimal meaning (as opposed to their binary meaning) when describing disk space, such that an indicated file size of 1 MB corresponds to 1 million bytes, as commonly used by hard disk manufacturers. Snow Leopard shuts down and goes to sleep faster. New wallpapers As with most upgrades of Mac OS X, new wallpapers are available. There are new wallpapers in the Nature (two of which are of snow leopards), Plants and Black and White sub-folders under the Apple folder. Furthermore, there are new Apple wallpaper sub-folders with multiple wallpapers: Art: Dancer on the Stage, Nighthawks, Poppies Blooming, Sunday Afternoon, Suprematism, The Great Wave, and Water Lilies. Patterns: Pinstripe and Saree. New solid colors can be used as wallpapers as well. There is a new blue and gray, as well as a solid kelp which serves as the "green wallpaper." The default "space nebula" wallpaper has been updated as well. Dropped features AppleTalk is no longer supported. It is no longer possible to change an application's language using the Finder's "Get Info" dialogue. While there are workarounds for some applications, others (such as Adobe After Effects CS4) will not be able to be run in a different language than the one selected in the system without using Terminal commands or third-party software. The option to change language for individual apps was added back in macOS Catalina in 2019. Creator codes, which are per-file metadata attributes that define, for a file that has a creator code, what application should open that file, regardless of its extension, have had their priority in the application selection process reduced. Creating or updating Hierarchical File System (HFS Plus predecessor) volumes is no longer supported. Developer technologies 64-bit architecture Mac OS X Tiger added limited support for 64-bit applications on machines with 64-bit processors; Leopard extended the support for 64-bit applications to include applications using most of Mac OS X's libraries and frameworks. In Snow Leopard, most built-in applications have been rebuilt to use the 64-bit x86-64 architecture (excluding iTunes, Front Row, Grapher and DVD Player applications). They will run in 32-bit mode on machines with 32-bit processors, and in 64-bit mode on machines with 64-bit processors. In addition, the Mac OS X kernel has been rebuilt to run in 64-bit mode on some machines. On those machines, Snow Leopard supports up to 16 terabytes of RAM. Newer Xserve and Mac Pro machines will run a 64-bit kernel by default; newer iMac and MacBook Pro machines can run a 64-bit kernel, but will not do so by default. Users wishing to use the 64-bit kernel on those machines must hold down the numbers 6 and 4 on the keyboard while booting to get the 64-bit kernel to load. A change to the com.apple.Boot.plist will also enable users with compatible computers to permanently boot into 64-bit for those wishing to do so. Stuart Harris, software product marketing manager at Apple Australia, said, "For the most part, everything that they experience on the Mac, from the 64-bit point of view, the applications, the operating system, is all going to be 64-bit, but that at this stage there were very few things, such as device drivers, that required 64-bit mode at the kernel level". With Mac OS X Snow Leopard only the following Apple computers run or are capable of running the 64-bit kernel: Amit Singh has reported that the early 2009 Mac Mini and MacBook may be capable of running the 64-bit kernel; however, Apple has set these models to boot into the 32-bit kernel. With some tweaking, the Unibody MacBook can be set to boot the 64-bit kernel. Grand Central Dispatch Grand Central Dispatch (GCD) uses the multiple processor cores now in every new Macintosh for more efficient performance. Due to the complexity of multithreaded programming and technical difficulties traditionally involved in making applications optimized for multicore CPUs, the majority of computer applications do not effectively use multiple processor cores. As a result, additional processing power, compared to single-core machines, often goes unused. Grand Central Dispatch includes APIs to help programmers efficiently use these cores for parallel programming. Grand Central Dispatch abstracts the notion of threads away, and instead provides developers with the concept of queues—lists of jobs (blocks of code) that need to be executed. GCD takes the responsibility of distributing the jobs among actual threads and cores, and clearing up unused memory created by inactive or old threads to achieve maximum performance. Apple is also releasing APIs for Grand Central Dispatch for developers to use in their applications and also to analyze specific blocks of code running on Grand Central Dispatch. A new C and Objective-C language feature named "Blocks" facilitates creation of code that will easily optimize to take advantage of Grand Central Dispatch. OpenCL OpenCL (Open Computing Language) addresses the power of graphics processing units (GPUs) to leverage them in any application, and not just for graphics-intensive applications like 3D games. OpenCL automatically optimizes for the kind of graphics processor in the Mac, adjusting itself to the available processing power. OpenCL provides consistent numeric precision and accuracy, fixing a problem that has hampered GPU-based programming in the past. OpenCL includes a C-based programming language with a structure that is already familiar to Mac OS X programmers, who can use Xcode developer tools to adapt their programs to work with OpenCL. Only the most process intensive parts of the application need to be written in OpenCL C without affecting the rest of the code. OpenCL is an open standard that has been supported by AMD, Intel, and Nvidia; it is maintained by Khronos Group. It serves a similar purpose to Nvidia's C for CUDA and Microsoft's Direct3D 11 compute shaders. It only works with the following Mac GPUs: NVIDIA GeForce 320M, GT 330M, 9400M, 9600M GT, 8600M GT, GT 120, GT 130, GTX 285, 8800 GT, 8800 GS, Quadro FX 4800, FX 5600 and ATI Radeon HD 4670, HD 4850, HD 4870, HD 5670, HD 5750, HD 5770, HD 5870, HD 6490M, HD 6750M, HD 6770M, HD 6970M. If the system does not possess one of these compatible GPUs, OpenCL code will instead execute on the system's CPU. CUPS CUPS (the printing system used in many Unix-like operating systems) has been updated to version 1.4 which provides improved driver, networking, and Kerberos support along with performance improvements. CUPS 1.4 is also the first implementation of the Internet Printing Protocol version 2.1. Power management Power management has been improved, with implementation of a new wake on demand feature supported on more recent Macintosh hardware. Wake on demand takes advantage of the sleep proxy service implemented in AirPort and Time Capsule routers, so that the computer can sleep while the router responds to mDNS queries. Should the request require the host computer to wake up, the router sends the necessary special wake-up-packet to the sleeping computer. Security Apple strengthened Mac OS X by implementing stack protection, and sandboxing more Mac OS X components such as the H.264 decoder in QuickTime and browser plug-ins as a separate process in Safari. Secure virtual memory was an option in earlier releases on Snow Leopard, but the checkbox to disable it was removed later. An anti-malware feature was also added to the system that alerts the user if malware is detected. Mac OS X 10.6.8 added regular malware definition updates. Computer security researcher Charlie Miller claims that OS X Snow Leopard is more vulnerable to attack than Microsoft Windows for lacking full address space layout randomization (ASLR) since Mac OS X Leopard, a technology that Microsoft started implementing in Windows Vista. The Safari web browser has received updates to version 6.0 in Lion and Mountain Lion, but not in Snow Leopard. Compatibility Snow Leopard breaks compatibility with several older versions of some applications, such as Parallels Desktop 3.0, versions of Aperture before 2.1.1, and versions of Keynote before 2.0.2, among other software. Apple has also published a list of applications with known compatibility issues with Snow Leopard. Printer and scanner drivers used by previous versions of Mac OS X are not compatible with Snow Leopard and will be replaced during Snow Leopard installation. Since the initial release of Snow Leopard many manufacturers have provided compatible drivers that are available via Software Update. If a native driver is not available Snow Leopard also includes CUPS and Gutenprint open source drivers that may provide limited functionality. 10.6.0 introduced a bug that frequently prevented DNS queries from returning IPv6 addresses. This was resolved in 10.6.8. Reception At the WWDC in 2009, Apple stated that Snow Leopard features no new major visual changes. Instead, the release focuses on refining the operating system to enable better performance. OSNews reported that Mac OS X Snow Leopard was well received by critics. Engadget reviewed Snow Leopard and pointed out that the price of Snow Leopard dropped from the $129 Apple charged for previous versions of Mac OS X to $29. Engadget's opinion was that this could be largely because most users would not see a noticeable change in the look and feel of the system. However, most reviews commented on the large improvement in speed of the native Mac OS X applications Finder, iCal, Mail, etc. CNET editors gave it 4 stars out of 5, stating "Intel Mac users will like Snow Leopard's smartly designed interface enhancements, and its Exchange support is a must-have (especially with Outlook for Mac on the way). With a ton of technological improvements, Snow Leopard is worth the $29 upgrade fee." On October 21, 2009, SFGate blogger Yobie Benjamin wrote that the "MacBook Pro that came preloaded with Snow Leopard kicks butt and is a screaming fast machine", but "when I tried to upgrade one of my 'older' MacBooks, it was a fricking disaster from hell". Apart from upgrading, Benjamin also tried a clean install. But he complained of slowness even after his clean install. He wrote, "I ended up downgrading back to OSX 10.5.8" then he concluded by writing, "I might try to do it again but it won't be till Apple releases at least 2 major fix updates. If you want to roll the dice and try, go ahead... your upgrade might work, however, random installs not working is not good for me. Lesson learned --- I'll wait." The single-user upgrade and Family Pack units of Snow Leopard ranked 1 and 2 respectively on Amazon.com's software bestseller charts when Apple announced it would release it within the week. Testmac.com highlighted other unexpected improvements including the release of a new version of Boot Camp, version 3.0, a cleaner, popup software update process and screen and video recording in the new QuickTime Player. The BBC reported that a bug in Mac OS X versions 10.6.0 and 10.6.1 which, in rare cases, caused loss of user account data after use of a previously existing guest account by users who had upgraded from a previous version of Mac OS X, received wide publicity. The bug was fixed as of version 10.6.2. Release history Former Apple CEO Steve Jobs announced Snow Leopard at WWDC on June 9, 2008, and it was privately demonstrated to developers by Senior Vice President of Software Engineering Bertrand Serlet. On Monday, May 11, 2009, after build 10A354, Apple issued a code freeze on Snow Leopard's APIs. The first public demonstration was given at WWDC 2009 by Serlet and Vice President of Mac OS Engineering, Craig Federighi. Mac OS X Server includes these features and other server-related features. Apple initially stated that Server would include ZFS support, but mention of this feature later disappeared from Apple's website and it was not included in the final release due to licensing issues. On January 27, 2016, Apple released an update for the Mac App Store on Mac OS X 10.6. The update was titled "Mac App Store Update for OS X Snow Leopard". The download was 3.5 MB. See also List of Macintosh software References External links Mac OS X Snow Leopard at Apple.com Mac OS X Server Snow Leopard at Apple.com Mac OS X Snow Leopard application compatibility list: a user-edited list of Mac applications that have been tested on Snow Leopard Mac OS X Snow Leopard review at Ars Technica 6 IA-32 operating systems X86-64 operating systems 2009 software Computer-related introductions in 2009

Operating System (OS)

Amiga The Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphics and audio compared to previous 8-bit systems. This includes the Atari ST – released earlier the same year – as well as the Macintosh and Acorn Archimedes. Based on the Motorola 68000 microprocessor, the Amiga differs from its contemporaries through the inclusion of custom hardware to accelerate graphics and sound, including sprites and a blitter, and a pre-emptive multitasking operating system called AmigaOS. The Amiga 1000 was released in July 1985, but production problems kept it from becoming widely available until early 1986. The best-selling model, the Amiga 500 was introduced in 1987 (along with the more expandable Amiga 2000). The Amiga 3000 was introduced in 1990, followed by the Amiga 500 Plus, and the Amiga 600 in March 1992. Finally, the Amiga 1200 and the Amiga 4000 were released in late 1992. The Amiga line sold an estimated 4.85 million units during the late 1980s to early 1990s. Although early advertisements cast the computer as an all-purpose business machine, especially when outfitted with the Sidecar IBM PC compatibility add-on, the Amiga was most commercially successful as a home computer, with a wide range of games and creative software. The Video Toaster hardware and software suite helped Amiga find a prominent role in desktop video and video production. The Amiga's audio hardware made it a popular platform for music tracker software. The processor and memory capacity enabled 3D rendering packages, including LightWave 3D, Imagine, and Traces, a predecessor to Blender. Poor marketing and the failure of later models to repeat the technological advances of the first systems resulted in Commodore quickly losing market share to the rapidly dropping prices of IBM PC compatibles, which gained 256 color graphics in 1987, as well as the fourth generation of video game consoles. Commodore ultimately went bankrupt in April 1994 after a version of the Amiga packaged as a game console, the Amiga CD32, failed in the marketplace. Since the demise of Commodore, various groups have marketed successors to the original Amiga line, including Genesi, Eyetech, ACube Systems Srl and A-EON Technology. AmigaOS has influenced replacements, clones, and compatible systems such as MorphOS and AROS. Currently Belgian company Hyperion Entertainment maintains and develops AmigaOS 4 which is official and direct descendant of AmigaOS 3.1 - the last system made by Commodore for the original Amiga Computers. History Concept and early development Jay Miner joined Atari, Inc. in the 1970s to develop custom integrated circuits, and led development of the Atari 2600's TIA. Almost as soon as its development was complete, the team began developing a much more sophisticated set of chips, CTIA, ANTIC and POKEY, that formed the basis of the Atari 8-bit family. With the 8-bit line's launch in 1979, the team once again started looking at a next generation chipset. Nolan Bushnell had sold the company to Warner Communications in 1978, and the new management was much more interested in the existing lines than development of new products that might cut into their sales. Miner wanted to start work with the new Motorola 68000, but management was only interested in another 6502 based system. Miner left the company, and, for a time, the industry. In 1979, Larry Kaplan left Atari and founded Activision. In 1982, Kaplan was approached by a number of investors who wanted to develop a new game platform. Kaplan hired Miner to run the hardware side of the newly formed company, "Hi-Toro". The system was code-named "Lorraine" in keeping with Miner's policy of giving systems female names, in this case the company president's wife, Lorraine Morse. When Kaplan left the company late in 1982, Miner was promoted to head engineer and the company relaunched as Amiga Corporation. A breadboard prototype (circuit board for testing and development) was largely completed by late 1983, and shown at the January 1984 Consumer Electronics Show (CES). At the time, the operating system was not ready, so the machine was demonstrated with the "Boing Ball" demo, a real-time animation showing a red-and-white spinning ball bouncing and casting a shadow; this bouncing ball became the official logo of the Amiga company. CES attendees had trouble believing the computer being demonstrated had the power to display such a demo and searched in vain for the "real" computer behind it. A further developed version of the system was demonstrated at the June 1984 CES and shown to many companies in hopes of garnering further funding, but found little interest in a market that was in the final stages of the video game crash of 1983. In March, Atari expressed a tepid interest in Lorraine for its potential use in a games console or home computer tentatively known as the . The talks were progressing slowly, and Amiga was running out of money. A temporary arrangement in June led to a $500,000 loan from Atari to Amiga to keep the company going. The terms required the loan to be repaid at the end of the month, otherwise Amiga would forfeit the Lorraine design to Atari. Commodore launch During 1983, Atari lost over $1 million a week, due to the combined effects of the crash and the ongoing price war in the home computer market. By the end of the year, Warner was desperate to sell the company. In January 1984, Jack Tramiel resigned from Commodore due to internal battles over the future direction of the company. A number of Commodore employees followed him to his new company, Tramel Technology. This included a number of the senior technical staff, where they began development of a 68000-based machine of their own. In June, Tramiel arranged a no-cash deal to take over Atari, reforming Tramel Technology as Atari Corporation. As many Commodore technical staff had moved to Atari, Commodore was left with no workable path to design their own next-generation computer. The company approached Amiga offering to fund development as a home computer system. They quickly arranged to repay the Atari loan, ending that threat. The two companies were initially arranging a $4 million license agreement before Commodore offered $24 million to purchase Amiga outright. By late 1984, the prototype breadboard chipset had successfully been turned into integrated circuits, and the system hardware was being readied for production. At this time the operating system (OS) was not as ready, and led to a deal to port an OS known as TRIPOS to the platform. TRIPOS was a multitasking system that had been written in BCPL during the 1970s for the PDP-11 minicomputer, but later experimentally ported to the 68000. This early version was known as AmigaDOS and the GUI as Workbench. The BCPL parts were later rewritten in the C language, and the entire system became AmigaOS. The system was enclosed in a pizza box form factor case; a late change was the introduction of vertical supports on either side of the case to provide a "garage" under the main section of the system where the keyboard could be stored. The first model was announced in 1985 as simply "The Amiga from Commodore", later to be retroactively dubbed the Amiga 1000. They were first offered for sale in August, but by October only 50 had been built, all of which were used by Commodore. Machines only began to arrive in quantity in mid-November, meaning they missed the Christmas buying rush. By the end of the year, they had sold 35,000 machines, and severe cashflow problems made the company pull out of the January 1986 CES. Bad or entirely missing marketing, forcing the development team to move to the east coast, notorious stability problems and other blunders limited sales in early 1986 to between 10,000 and 15,000 units a month. Commercial success In late 1985, Thomas Rattigan was promoted to COO of Commodore, and then to CEO in February 1986. He immediately implemented an ambitious plan that covered almost all of the company's operations. Among these was the long-overdue cancellation of the now outdated PET and VIC-20 lines, as well as a variety of poorly selling Commodore 64 offshoots and the Commodore 900 workstation effort. Another one of the changes was to split the Amiga into two products, a new high-end version of the Amiga aimed at the creative market, and a cost-reduced version that would take over for the Commodore 64 in the low-end market. These new designs were released in 1987 as the Amiga 2000 and Amiga 500, the latter of which went on to widespread success and became their best selling model. Similar high-end/low-end models would make up the Amiga line for the rest of its history; follow-on designs included the Amiga 3000/Amiga 500 Plus/Amiga 600, and the Amiga 4000/Amiga 1200. These models incorporated a series of technical upgrades known as the ECS and AGA, which added higher resolution displays among many other improvements and simplifications. The Amiga line sold an estimated 4,850,000 machines over its lifetime. The machines were most popular in the UK and Germany, with about 1.5 million sold in each country, and sales in the high hundreds of thousands in other European nations. The machine was less popular in North America, where an estimated 700,000 were sold. In the United States, the Amiga found a niche with enthusiasts and in vertical markets for video processing and editing. In the United Kingdom, it was more broadly popular as a home computer and often used for video games. Beginning in 1988 it overlapped with the 16-bit Mega Drive, then the Super Nintendo Entertainment System in the early 1990s. Commodore UK's Kelly Sumner did not see Sega or Nintendo as competitors, but instead credited their marketing campaigns which spent over or for promoting video games as a whole and thus helping to boost Amiga sales. Bankruptcy In spite of his successes in making the company profitable and bringing the Amiga line to market, Rattigan was soon forced out in a power struggle with majority shareholder, Irving Gould. This is widely regarded as the turning point, as further improvements to the Amiga were eroded by rapid improvements in other platforms. On April 29, 1994, Commodore filed for bankruptcy and its assets were purchased by Escom, a German PC manufacturer, who created the subsidiary company Amiga Technologies. They re-released the A1200 and A4000T, and introduced a new 68060 version of the A4000T. Amiga Technologies researched and developed the Amiga Walker prototype. They presented the machine publicly at CeBit. Escom, in turn, went bankrupt in 1997. The Amiga brand was then sold to a U.S. Wintel PC manufacturer, Gateway 2000, which had announced grand plans for it. In 2000, however, Gateway sold the Amiga brand without having released any products. The current owner of the trademark, Amiga, Inc., licensed the rights to sell hardware using either the Amiga or AmigaOne brand to Eyetech Group, Hyperion Entertainment and Commodore USA. Hardware At its core, the Amiga has a custom chipset consisting of several coprocessors, which handle audio, video and direct memory access independently of the Central Processing Unit (CPU). This architecture frees up the CPU for other tasks and gave the Amiga a performance edge over its competitors, particularly in terms of graphics-intensive applications and games. The general Amiga architecture uses two distinct bus subsystems: the chipset bus and the CPU bus. The chipset bus allows the custom coprocessors and CPU to address "Chip RAM". The CPU bus provides addressing to other subsystems, such as conventional RAM, ROM and the Zorro II or Zorro III expansion subsystems. This architecture enables independent operation of the subsystems; the CPU "Fast" bus can be much faster than the chipset bus. CPU expansion boards may provide additional custom buses. Additionally, "busboards" or "bridgeboards" may provide ISA or PCI buses. Central processing unit The Motorola 68000 series of microprocessors was used in all Amiga models from Commodore. While all CPU in the 68000 family have a 32-bit ISA design (programmer uses and sees a 32-bit model), the MC68000 used in the most popular models is a 16-bit (or 16/32-bit) processor because its ALU operates in 16-bit (32-bit operations require additional clock cycles, consuming more time). The MC68000 has a 16-bit external data bus so 32-bits of data is transferred in two consecutive steps, a technique called multiplexing. This is transparent to the software, which was 32-bit from the beginning. The MC68000 can address 16 MB of physical memory. Later Amiga models featured higher-speed, full 32-bit CPUs with a larger address space and instruction pipeline facilities. CPU upgrades were offered by both Commodore and third-party manufacturers. Most Amiga models can be upgraded either by direct CPU replacement or through expansion boards. Such boards often featured faster and higher capacity memory interfaces and hard disk controllers. Towards the end of Commodore's time in charge of Amiga development, there were suggestions that Commodore intended to move away from the 68000 series to higher performance RISC processors, such as the PA-RISC. Those ideas were never developed before Commodore filed for bankruptcy. Despite this, third-party manufacturers designed upgrades featuring a combination of 68000 series and PowerPC processors along with a PowerPC native microkernel and software. Later Amiga clones featured PowerPC processors only. Custom chipset The custom chipset at the core of the Amiga design appeared in three distinct generations, with a large degree of backward-compatibility. The Original Chip Set (OCS) appeared with the launch of the A1000 in 1985. OCS was eventually followed by the modestly improved Enhanced Chip Set (ECS) in 1990 and finally by the partly 32-bit Advanced Graphics Architecture (AGA) in 1992. Each chipset consists of several coprocessors that handle graphics acceleration, digital audio, direct memory access and communication between various peripherals (e.g., CPU, memory and floppy disks). In addition, some models featured auxiliary custom chips that performed tasks such as SCSI control and display de-interlacing. Graphics All Amiga systems can display full-screen animated graphics with 2, 4, 8, 16, 32, 64 (EHB Mode), or 4096 colors (HAM Mode). Models with the AGA chipset (A1200 and A4000) also have non-EHB 64, 128, 256, and 262144 (HAM8 Mode) color modes and a palette expanded from 4096 to 16.8 million colors. The Amiga chipset can genlock, which is the ability to adjust its own screen refresh timing to match an incoming NTSC or PAL video signal. When combined with setting transparency, this allows an Amiga to overlay an external video source with graphics. This ability made the Amiga popular for many applications, and provides the ability to do character generation and CGI effects far more cheaply than earlier systems. This ability has been frequently utilized by wedding videographers, TV stations and their weather forecasting divisions (for weather graphics and radar), advertising channels, music video production, and desktop videographers. The NewTek Video Toaster was made possible by the genlock ability of the Amiga. In 1988, the release of the Amiga A2024 fixed-frequency monochrome monitor with built-in framebuffer and flicker fixer hardware provided the Amiga with a choice of high-resolution graphic modes (1024×800 for NTSC and 1024×1024 for PAL). ReTargetable Graphics ReTargetable Graphics is an API for device drivers mainly used by 3rd party graphics hardware to interface with AmigaOS via a set of libraries. The software libraries may include software tools to adjust resolution, screen colors, pointers and screenmodes. The standard Intuition interface is limited to display depths of 8 bits, while RTG makes it possible to handle higher depths like 24-bits. Sound The sound chip, named Paula, supports four PCM-sample-based sound channels (two for the left speaker and two for the right) with 8-bit resolution for each channel and a 6-bit volume control per channel. The analog output is connected to a low-pass filter, which filters out high-frequency aliases when the Amiga is using a lower sampling rate (see Nyquist frequency). The brightness of the Amiga's power LED is used to indicate the status of the Amiga's low-pass filter. The filter is active when the LED is at normal brightness, and deactivated when dimmed (or off on older A500 Amigas). On Amiga 1000 (and first Amiga 500 and Amiga 2000 model), the power LED had no relation to the filter's status, and a wire needed to be manually soldered between pins on the sound chip to disable the filter. Paula can read directly from the system's RAM, using direct memory access (DMA), making sound playback without CPU intervention possible. Although the hardware is limited to four separate sound channels, software such as OctaMED uses software mixing to allow eight or more virtual channels, and it was possible for software to mix two hardware channels to achieve a single 14-bit resolution channel by playing with the volumes of the channels in such a way that one of the source channels contributes the most significant bits and the other the least. The quality of the Amiga's sound output, and the fact that the hardware is ubiquitous and easily addressed by software, were standout features of Amiga hardware unavailable on PC platforms for years. Third-party sound cards exist that provide DSP functions, multi-track direct-to-disk recording, multiple hardware sound channels and 16-bit and beyond resolutions. A retargetable sound API called AHI was developed allowing these cards to be used transparently by the OS and software. Kickstart firmware Kickstart is the firmware upon which AmigaOS is bootstrapped. Its purpose is to initialize the Amiga hardware and core components of AmigaOS and then attempt to boot from a bootable volume, such as a floppy disk or hard disk drive. Most models (excluding the Amiga 1000) come equipped with Kickstart on an embedded ROM-chip. Keyboard and mouse The keyboard on Amiga computers is similar to that found on a mid-80s IBM PC: Ten function keys, a numeric keypad, and four separate directional arrow keys. Caps Lock and Control share space to the left of A. Absent are Home, End, Page Up, and Page Down keys: These functions are accomplished on Amigas by pressing shift and the appropriate arrow key. The Amiga keyboard adds a Help key, which a function key usually acts as on PCs (usually F1). In addition to the Control and Alt modifier keys, the Amiga has 2 "Amiga" keys, rendered as "Open Amiga" and "Closed Amiga" similar to the Open/Closed Apple logo keys on Apple II keyboards. The left is used to manipulate the operating system (moving screens and the like) and the right delivers commands to the application. The absence of Num lock frees space for more mathematical symbols around the numeric pad. Like IBM-compatible computers, the mouse has two buttons, but in AmigaOS, pressing and holding the right button replaces the system status line at the top of the screen with a Maclike menu bar. As with Apple's Mac OS prior to Mac OS 8, menu options are selected by releasing the button over that option, not by left clicking. Menu items that have a boolean toggle state can be left clicked whilst the menu is kept open with the right button, which allows the user – for example – to set some selected text to bold, underline and italics in one visit to the menus. The mouse plugs into one of two Atari joystick ports used for joysticks, game paddles, and graphics tablets. Although compatible with analog joysticks, Atari-style digital joysticks became standard. Unusually, two independent mice can be connected to the joystick ports; some games, such as Lemmings, were designed to take advantage of this. Other peripherals and expansions The Amiga was one of the first computers for which inexpensive sound sampling and video digitization accessories were available. As a result of this and the Amiga's audio and video capabilities, the Amiga became a popular system for editing and producing both music and video. Many expansion boards were produced for Amiga computers to improve the performance and capability of the hardware, such as memory expansions, SCSI controllers, CPU boards, and graphics boards. Other upgrades include genlocks, network cards for Ethernet, modems, sound cards and samplers, video digitizers, extra serial ports, and IDE controllers. Additions after the demise of Commodore company are USB cards. The most popular upgrades were memory, SCSI controllers and CPU accelerator cards. These were sometimes combined into one device. Early CPU accelerator cards used the full 32-bit CPUs of the 68000 family such as the Motorola 68020 and Motorola 68030, almost always with 32-bit memory and usually with FPUs and MMUs or the facility to add them. Later designs feature the Motorola 68040 or Motorola 68060. Both CPUs feature integrated FPUs and MMUs. Many CPU accelerator cards also had integrated SCSI controllers. Phase5 designed the PowerUP boards (Blizzard PPC and CyberStorm PPC) featuring both a 68k (a 68040 or 68060) and a PowerPC (603 or 604) CPU, which are able to run the two CPUs at the same time and share the system memory. The PowerPC CPU on PowerUP boards is usually used as a coprocessor for heavy computations; a powerful CPU is needed to run MAME for example, but even decoding JPEG pictures and MP3 audio was considered heavy computation at the time. It is also possible to ignore the 68k CPU and run Linux on the PPC via project Linux APUS, but a PowerPC-native AmigaOS promised by Amiga Technologies GmbH was not available when the PowerUP boards first appeared. 24-bit graphics cards and video cards were also available. Graphics cards were designed primarily for 2D artwork production, workstation use, and later, gaming. Video cards are designed for inputting and outputting video signals, and processing and manipulating video. In the North American market, the NewTek Video Toaster was a video effects board that turned the Amiga into an affordable video processing computer that found its way into many professional video environments. One well-known use was to create the special effects in early series of Babylon 5. Due to its NTSC-only design, it did not find a market in countries that used the PAL standard, such as in Europe. In those countries, the OpalVision card was popular, although less featured and supported than the Video Toaster. Low-cost time base correctors (TBC) specifically designed to work with the Toaster quickly came to market, most of which were designed as standard Amiga bus cards. Various manufacturers started producing PCI busboards for the A1200, A3000 and A4000, allowing standard Amiga computers to use PCI cards such as graphics cards, Sound Blaster sound cards, 10/100 Ethernet cards, USB cards, and television tuner cards. Other manufacturers produced hybrid boards that contained an Intel x86 series chip, allowing the Amiga to emulate a PC. PowerPC upgrades with Wide SCSI controllers, PCI busboards with Ethernet, sound and 3D graphics cards, and tower cases allowed the A1200 and A4000 to survive well into the late nineties. Expansion boards were made by Richmond Sound Design that allow their show control and sound design software to communicate with their custom hardware frames either by ribbon cable or fiber optic cable for long distances, allowing the Amiga to control up to eight million digitally controlled external audio, lighting, automation, relay and voltage control channels spread around a large theme park, for example. See Amiga software for more information on these applications. Other devices included the following: Amiga 501 with 512 KB RAM and real-time clock Trumpcard 500 Zorro-II SCSI interface GVP A530 Turbo, accelerator, RAM expansion, PC emulator A2091 / A590 SCSI hard disk controller + 2 MB RAM expansion A3070 SCSI tape backup unit with a capacity of , OEM Archive Viper 1/4-inch A2065 Ethernet Zorro-II interface – the first Ethernet interface for Amiga; uses the AMD Am7990 chip The same interface chip is used in DECstation as well. Ariadne Zorro-II Ethernet interface using the AMD Am7990 A4066 Zorro II Ethernet interface using the SMC 91C90QF X-Surf from Individual Computers using the Realtek 8019AS A2060 Arcnet A1010 floppy disk drive consisting of a 3.5-inch double density (DD), , drive unit connected via DB-23 connector; track-to-track delay is on the order of . The default capacity is . Many clone drives were available, and products such as the Catweasel and KryoFlux make it possible to read and write Amiga and other special disc formats on standard x86 PCs. NE2000-compatible PCMCIA Ethernet cards for Amiga 600 and Amiga 1200 Serial ports The Commodore A2232 board provides seven RS-232C serial ports in addition to the Amiga's built-in serial port. Each port can be driven independently at speeds of 50 to . There is, however, a driver available on Aminet that allows two of the serial ports to be driven at . The serial card used the 65CE02 CPU clocked at . This CPU was also part of the CSG 4510 CPU core that was used in the Commodore 65 computer. Networking Amiga has three networking interface APIs: AS225: the official Commodore TCP/IP stack API with hard-coded drivers in revision 1 (AS225r1) for the A2065 Ethernet and the A2060 Arcnet interfaces. In revision 2, (AS225r2) the SANA-II interface was used. SANA-II: a standardized API for hardware of network interfaces. It uses an inefficient buffer handling scheme, and lacks proper support for promiscuous and multicast modes. Miami Network Interface (MNI): an API that doesn't have the problems that SANA-II suffers from. It requires AmigaOS v2.04 or higher. Different network media were used: Models and variants The original Amiga models were produced from 1985 to 1996. They are, in order of production: 1000, 2000, 500, 1500, 2500, 3000, 3000UX, 3000T, CDTV, 500+, 600, 4000, 1200, CD32, and 4000T. The PowerPC based AmigaOne computers were later marketed beginning in 2002. Several companies and private persons have also released Amiga clones and still do so today. Commodore Amiga The first Amiga model, the Amiga 1000, was launched in 1985. In 2006, PC World rated the Amiga 1000 as the seventh greatest PC of all time, stating "Years ahead of its time, the Amiga was the world's first multimedia, multitasking personal computer". Commodore updated the desktop line of Amiga computers with the Amiga 2000 in 1987, the Amiga 3000 in 1990, and the Amiga 4000 in 1992, each offering improved capabilities and expansion options. The best selling models were the budget models, however, particularly the highly successful Amiga 500 (1987) and the Amiga 1200 (1992). The Amiga 500+ (1991) was the shortest lived model, replacing the Amiga 500 and lasting only six months until it was phased out and replaced with the Amiga 600 (1992), which in turn was also quickly replaced by the Amiga 1200. The CDTV, launched in 1991, was a CD-ROM-based game console and multimedia appliance several years before CD-ROM drives were common. The system never achieved any real success. Commodore's last Amiga offering before filing for bankruptcy was the Amiga CD32 (1993), a 32-bit CD-ROM games console. Although discontinued after Commodore's demise it met with moderate commercial success in Europe. The CD32 was a next generation CDTV, and it was designed to save Commodore by entering the growing video game console market. Following purchase of Commodore's assets by Escom in 1995, the A1200 and A4000T continued to be sold in small quantities until 1996, though the ground lost since the initial launch and the prohibitive expense of these units meant that the Amiga line never regained any real popularity. Several Amiga models contained references to songs by the rock band The B-52's. Early A500 units had the words "B52/ROCK LOBSTER" silk-screen printed onto their printed circuit board, a reference to the song "Rock Lobster" The Amiga 600 referenced "JUNE BUG" (after the song "Junebug") and the Amiga 1200 had "CHANNEL Z" (after "Channel Z")., and the CD-32 had "Spellbound." AmigaOS 4 systems AmigaOS 4 is designed for PowerPC Amiga systems. It is mainly based on AmigaOS 3.1 source code, with some parts of version 3.9. Currently runs on both Amigas equipped with CyberstormPPC or BlizzardPPC accelerator boards, on the Teron series based AmigaOne computers built by Eyetech under license by Amiga, Inc., on the Pegasos II from Genesi/bPlan GmbH, on the ACube Systems Srl Sam440ep / Sam460ex / AmigaOne 500 systems and on the A-EON AmigaOne X1000. AmigaOS 4.0 had been available only in developer pre-releases for numerous years until it was officially released in December 2006. Due to the nature of some provisions of the contract between Amiga Inc. and Hyperion Entertainment (the Belgian company that is developing the OS), the commercial AmigaOS 4 had been available only to licensed buyers of AmigaOne motherboards. AmigaOS 4.0 for Amigas equipped with PowerUP accelerator boards was released in November 2007. Version 4.1 was released in August 2008 for AmigaOne systems, and in May 2011 for Amigas equipped with PowerUP accelerator boards. The most recent release of AmigaOS for all supported platforms is 4.1 update 5. Starting with release 4.1 update 4 there is an Emulation drawer containing official AmigaOS 3.x ROMs (all classic Amiga models including CD32) and relative Workbench files. Acube Systems entered an agreement with Hyperion under which it has ported AmigaOS 4 to its Sam440ep and Sam460ex line of PowerPC-based motherboards. In 2009 a version for Pegasos II was released in co-operation with Acube Systems. In 2012, A-EON Technology Ltd manufactured and released the AmigaOne X1000 to consumers through their partner, Amiga Kit who provided end-user support, assembly and worldwide distribution of the new system. Amiga hardware clones Long-time Amiga developer MacroSystem entered the Amiga-clone market with their DraCo non-linear video editing system. It appears in two versions, initially a tower model and later a cube. DraCo expanded upon and combined a number of earlier expansion cards developed for Amiga (VLabMotion, Toccata, WarpEngine, RetinaIII) into a true Amiga-clone powered by the Motorola 68060 processor. The DraCo can run AmigaOS 3.1 up through AmigaOS 3.9. It is the only Amiga-based system to support FireWire for video I/O. DraCo also offers an Amiga-compatible Zorro-II expansion bus and introduced a faster custom DraCoBus, capable of transfer rates (faster than Commodore's Zorro-III). The technology was later used in the Casablanca system, a set-top-box also designed for non-linear video editing. In 1998, Index Information released the Access, an Amiga-clone similar to the Amiga 1200, but on a motherboard that could fit into a standard 5¼" drive bay. It features either a 68020 or 68030 CPU, with a redesigned AGA chipset, and runs AmigaOS 3.1. In 1998, former Amiga employees (John Smith, Peter Kittel, Dave Haynie and Andy Finkel to mention few) formed a new company called PIOS. Their hardware platform, PIOS One, was aimed at Amiga, Atari and Macintosh users. The company was renamed to Met@box in 1999 until it folded. The NatAmi (short for Native Amiga) hardware project began in 2005 with the aim of designing and building an Amiga clone motherboard that is enhanced with modern features. The NatAmi motherboard is a standard Mini-ITX-compatible form factor computer motherboard, powered by a Motorola/Freescale 68060 and its chipset. It is compatible with the original Amiga chipset, which has been inscribed on a programmable FPGA Altera chip on the board. The NatAmi is the second Amiga clone project after the Minimig motherboard, and its history is very similar to that of the C-One mainboard developed by Jeri Ellsworth and Jens Schönfeld. From a commercial point of view, Natami's circuitry and design are currently closed source. One goal of the NatAmi project is to design an Amiga-compatible motherboard that includes up-to-date features but that does not rely on emulation (as in WinUAE), modern PC Intel components, or a modern PowerPC mainboard. As such, NatAmi is not intended to become another evolutionary heir to classic Amigas, such as with AmigaOne or Pegasos computers. This "purist" philosophy essentially limits the resulting processor speed but puts the focus on bandwidth and low latencies. The developers also recreated the entire Amiga chipset, freeing it from legacy Amiga limitations such as two megabytes of audio and video graphics RAM as in the AGA chipset, and rebuilt this new chipset by programming a modern FPGA Altera Cyclone IV chip. Later, the developers decided to create from scratch a new software-form processor chip, codenamed "N68050" that resides in the physical Altera FPGA programmable chip. In 2006, two new Amiga clones were announced, both using FPGA based hardware synthesis to replace the Amiga OCS custom chipset. The first, the Minimig, is a personal project of Dutch engineer Dennis van Weeren. Referred to as "new Amiga hardware", the original model was built on a Xilinx Spartan-3 development board, but soon a dedicated board was developed. The minimig uses the FPGA to reproduce the custom Denise, Agnus, Paula and Gary chips as well as both 8520 CIAs and implements a simple version of Amber. The rest of the chips are an actual 68000 CPU, ram chips, and a PIC microcontroller for BIOS control. The design for Minimig was released as open-source on July 25, 2007. In February 2008, an Italian company Acube Systems began selling Minimig boards. A third party upgrade replaces the PIC microcontroller with a more powerful ARM processor, providing more functionality such as write access and support for hard disk images. The Minimig core has been ported to the FPGArcade "Replay" board. The Replay uses an FPGA with about three times more capacity and that does support the AGA chipset and a 68020 soft core with 68030 capabilities. The Replay board is designed to implement many older computers and classic arcade machines. The second is the Clone-A system announced by Individual Computers. As of mid 2007 it has been shown in its development form, with FPGA-based boards replacing the Amiga chipset and mounted on an Amiga 500 motherboard. Operating systems AmigaOS AmigaOS is a single-user multitasking operating system. It was one of the first commercially available consumer operating systems for personal computers to implement preemptive multitasking. It was developed first by Commodore International and initially introduced in 1985 with the Amiga 1000. John C. Dvorak wrote in PC Magazine in 1996: AmigaOS combines a command-line interface and graphical user interface. AmigaDOS is the disk operating system and command line portion of the OS and Workbench the native graphical windowing, graphical environment for file management and launching applications. AmigaDOS allows long filenames (up to 107 characters) with whitespace and does not require filename extensions. The windowing system and user interface engine that handles all input events is called Intuition. The multi-tasking kernel is called Exec. It acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritised round-robin scheduling. It enabled true pre-emptive multitasking in as little as 256 KB of free memory. AmigaOS does not implement memory protection; the 68000 CPU does not include a memory management unit. Although this speeds and eases inter-process communication because programs can communicate by simply passing a pointer back and forth, the lack of memory protection made the AmigaOS more vulnerable to crashes from badly behaving programs than other multitasking systems that did implement memory protection, and Amiga OS is fundamentally incapable of enforcing any form of security model since any program had full access to the system. A co-operational memory protection feature was implemented in AmigaOS 4 and could be retrofitted to old AmigaOS systems using Enforcer or CyberGuard tools. The problem was somewhat exacerbated by Commodore's initial decision to release documentation relating not only to the OS's underlying software routines, but also to the hardware itself, enabling intrepid programmers who had developed their skills on the Commodore 64 to POKE the hardware directly, as was done on the older platform. While the decision to release the documentation was a popular one and allowed the creation of fast, sophisticated sound and graphics routines in games and demos, it also contributed to system instabilityas some programmers lacked the expertise to program at this level. For this reason, when the new AGA chipset was released, Commodore declined to release low-level documentation in an attempt to force developers into using the approved software routines. Influence on other operating systems AmigaOS directly or indirectly inspired the development of various operating systems. MorphOS and AROS clearly inherit heavily from the structure of AmigaOS as explained directly in articles regarding these two operating systems. AmigaOS also influenced BeOS, which featured a centralized system of Datatypes, similar to that present in AmigaOS. Likewise, DragonFly BSD was also inspired by AmigaOS as stated by Dragonfly developer Matthew Dillon who is a former Amiga developer. WindowLab and amiwm are among several window managers for the X Window System seek to mimic the Workbench interface. IBM licensed the Amiga GUI from Commodore in exchange for the REXX language license. This allowed OS/2 to have the WPS (Workplace Shell) GUI shell for OS/2 2.0, a 32-bit operating system. Unix and Unix-like systems Commodore-Amiga produced Amiga Unix, informally known as Amix, based on AT&T SVR4. It supports the Amiga 2500 and Amiga 3000 and is included with the Amiga 3000UX. Among other unusual features of Amix is a hardware-accelerated windowing system that can scroll windows without copying data. Amix is not supported on the later Amiga systems based on 68040 or 68060 processors. Other, still maintained, operating systems are available for the classic Amiga platform, including Linux and NetBSD. Both require a CPU with MMU such as the 68020 with 68851 or full versions of the 68030, 68040 or 68060. There is also a version of Linux for Amigas with PowerPC accelerator cards. Debian and Yellow Dog Linux can run on the AmigaOne. There is an official, older version of OpenBSD. The last Amiga release is 3.2. MINIX 1.5.10 also runs on Amiga. Emulating other systems The Amiga Sidecar is a complete IBM PC XT compatible computer contained in an expansion card. It was released by Commodore in 1986 and promoted as a way to run business software on the Amiga 1000. Amiga software In the late 1980s and early 1990s the platform became particularly popular for gaming, demoscene activities and creative software uses. During this time commercial developers marketed a wide range of games and creative software, often developing titles simultaneously for the Atari ST due to the similar hardware architecture. Popular creative software included 3D rendering (ray-tracing) packages, bitmap graphics editors, desktop video software, software development packages and "tracker" music editors. Until the late 1990s the Amiga remained a popular platform for non-commercial software, often developed by enthusiasts, and much of which was freely redistributable. An on-line archive, Aminet, was created in 1992 and until around 1996 was the largest public archive of software, art and documents for any platform. Marketing The name Amiga was chosen by the developers from the Spanish word for a female friend, because they knew Spanish, and because it occurred before Apple and Atari alphabetically. It also conveyed the message that the Amiga computer line was "user friendly" as a pun or play on words. The first official Amiga logo was a rainbow-colored double check mark. In later marketing material Commodore largely dropped the checkmark and used logos styled with various typefaces. Although it was never adopted as a trademark by Commodore, the "Boing Ball" has been synonymous with Amiga since its launch. It became an unofficial and enduring theme after a visually impressive animated demonstration at the 1984 Winter Consumer Electronics Show in January 1984 showing a checkered ball bouncing and rotating. Following Escom's purchase of Commodore in 1996, the Boing Ball theme was incorporated into a new logo. Early Commodore advertisements attempted to cast the computer as an all-purpose business machine, though the Amiga was most commercially successful as a home computer. Throughout the 1980s and early 1990s Commodore primarily placed advertising in computer magazines and occasionally in national newspapers and on television. Legacy Since the demise of Commodore, various groups have marketed successors to the original Amiga line: Genesi sold PowerPC based hardware under the Pegasos brand running AmigaOS and MorphOS; Eyetech sold PowerPC based hardware under the AmigaOne brand from 2002 to 2005 running AmigaOS 4; Amiga Kit distributes and sells PowerPC based hardware under the AmigaOne brand from 2010 to present day running AmigaOS 4; ACube Systems sells the AmigaOS 3 compatible Minimig system with a Freescale MC68SEC000 CPU (Motorola 68000 compatible) and AmigaOS 4 compatible Sam440 / Sam460 / AmigaOne 500 systems with PowerPC processors; A-EON Technology Ltd sells the AmigaOS 4 compatible AmigaOne X1000 system with P.A. Semi PWRficient PA6T-1682M processor. Amiga Kit Amiga Store, Vesalia Computer and AMIGAstore.eu sell numerous items from aftermarket components to refurbished classic systems. AmigaOS and MorphOS are commercial proprietary operating systems. AmigaOS 4, based on AmigaOS 3.1 source code with some parts of version 3.9, is developed by Hyperion Entertainment and runs on PowerPC based hardware. MorphOS, based on some parts of AROS source code, is developed by MorphOS Team and is continued on Apple and other PowerPC based hardware. There is also AROS, a free and open source operating system (re-implementation of the AmigaOS 3.1 APIs), for Amiga 68k, x86 and ARM hardware (one version runs Linux-hosted on the Raspberry Pi). In particular, AROS for Amiga 68k hardware aims to create an open source Kickstart ROM replacement for emulation purpose and/or for use on real "classic" hardware. Magazines Amiga Format, continued until 2000, some six years after Commodore filed for bankruptcy. Amiga Active, was launched in 1999 and was published until 2001. Several magazines are in publication today: Amiga Future, which is available in both English and German; Bitplane.it, a bimonthly magazine in Italian; and AmigaPower, a long-running French magazine. Print magazine Amiga Addict started publication in 2020. Uses The Amiga series of computers found a place in early computer graphic design and television presentation. Below are some examples of notable uses and users: Season 1 and part of season 2 of the television series Babylon 5 were rendered in LightWave 3D on Amigas. Other television series using Amigas for special effects included SeaQuest DSV and Max Headroom. In addition, many other celebrities and notable individuals have made use of the Amiga: Andy Warhol was an early user of the Amiga and appeared at the launch, where he made a computer artwork of Debbie Harry. Warhol used the Amiga to create a new style of art made with computers, and was the author of a multimedia opera called You Are the One, which consists of an animated sequence featuring images of actress Marilyn Monroe assembled in a short movie with a soundtrack. The video was discovered on two old Amiga floppies in a drawer in Warhol's studio and repaired in 2006 by the Detroit Museum of New Art. The pop artist has been quoted as saying: "The thing I like most about doing this kind of work on the Amiga is that it looks like my work in other media". Artist Jean "Moebius" Giraud credits the Amiga he bought for his son as a bridge to learning about "using paint box programs". He uploaded some of his early experiments to the file sharing forums on CompuServe. The "Weird Al" Yankovic film UHF contains a computer animated music video parody of the Dire Straits song "Money for Nothing", titled "Money for Nothing/Beverly Hillbillies*". According to the DVD commentary track, this spoof was created on an Amiga home computer. Rolf Harris used an Amiga to digitize his hand-drawn art work for animation on his television series Rolf's Cartoon Club. Todd Rundgren's video "Change Myself" was produced with Toaster and Lightwave. Scottish pop artist Calvin Harris composed his 2007 debut album I Created Disco with an Amiga 1200. Susumu Hirasawa, a Japanese progressive-electronic artist, is known for using Amigas to compose and perform music, aid his live shows and make his promotional videos. He has also been inspired by the Amiga, and has referenced it in his lyrics. His December 13, 1994 "Adios Jay" Interactive Live Show was dedicated to (then recently deceased) Jay Miner. He also used the Amiga to create the virtual drummer TAINACO, who was a CG rendered figure whose performance was made with Elan Performer and was projected with DCTV. He also composed and performed "Eastern-boot", the AmigaOS 4 boot jingle. Electronic musician Max Tundra created his three albums with an Amiga 500. Bob Casale, keyboardist and guitarist of the new wave band Devo, used Amiga computer graphics on the album cover to Devo's album Total Devo. Most of Pokémon Gold and Silver's music was created on an Amiga computer, converted to MIDI, and then reconverted to the game's music format. Special purpose applications Amigas were used in various NASA laboratories to keep track of low orbiting satellites until 2004. Amigas were used at Kennedy Space Center to run strip-chart recorders, to format and display data, and control stations of platforms for Delta rocket launches. Palomar Observatory used Amigas to calibrate and control the charge-coupled devices in their telescopes, as well as to display and store the digitized images they collected. London Transport Museum developed their own interactive multi-media software for the CD32 including a virtual tour of the museum. Amiga 500 motherboards were used, in conjunction with a LaserDisc player and genlock device, in arcade games manufactured by American Laser Games. A custom Amiga 4000T motherboard was used in the HDI 1000 medical ultrasound system built by Advanced Technology Labs. , the Grand Rapids Public School district uses a Commodore Amiga 2000 with 1200 baud modem to automate its air conditioning and heating systems for the 19 schools covered by the GRPS district. The system has been operating day and night for decades. The Weather Network used Amigas to display the weather on TV. See also Amiga Forever List of Amiga games Amiga emulation SAGE Computer Technology Notes References External links Official AmigaOS website History of the Amiga at Ars Technica Amiga, Inc. Website (Archive.org, October 2017) Amiga Software Database Amiga Hardware Database Big Book of Amiga Hardware RUN Magazine Issue 21, September 1985 article on the introduction of the Amiga Amiga.org: community forums and support English Amiga Board: Amiga community forums and support The Hall of Light: the database of Amiga games The Amiga Museum Computer-related introductions in 1985 American inventions 68000-based home computers Home computers Personal computers

Operating System (OS)

Nucleus RTOS Nucleus RTOS is a real-time operating system (RTOS) produced by the Embedded Software Division of Mentor Graphics, a Siemens Business, supporting 32- and 64-bit embedded system platforms. The operating system (OS) is designed for real-time embedded systems for medical, industrial, consumer, aerospace, and Internet of things (IoT) uses. Nucleus was released first in 1993. The latest version is 3.x, and includes features such as power management, process model, 64-bit support, safety certification, and support for heterogeneous computing multi-core system on a chip (SOCs) processors. Nucleus process model adds space domain partitioning for task and module isolation on SOCs with either a memory management unit (MMU) or memory protection unit (MPU), such as those based on ARMv7/8 Cortex-A/R/M cores. Supported platforms Nucleus supports many embedded processors including leading ARMv7 Cortex A, R, and M devices. Recent releases support ARMv8 64-bit devices. The official website has a full list of supported devices. It includes 32-bit MCUs and MPUs, configurable devices, and 32-bit and 64-bit multi-core processors. History Nucleus 1.x was released first in 1993 by Accelerated Technology (ATI) as Nucleus PLUS. It soon became one of the most commonly used RTOSs in the embedded market. Following its early success there, ATI added support for networking, graphics, and file systems, which accelerated adoption. Mentor Graphics acquired ATI in March 2002, which was soon followed by the second generation of Nucleus RTOS. Version 2.x was released in 2003, improving its portability across different architectures and tool sets. New components like IPv6, Flash memory file system and Universal Serial Bus (USB) 2.0 were added. Mentor replaced the legacy Codelab debugger with EDGE development tools which included compiler tools, debugger, simulator, and profiler. Mentor Graphics introduced the 3rd generation Nucleus in 2010. Version 3.x was intended for both high-end microprocessor units (MPUs), microcontroller units (MCUs), digital signal processors (DSPs), and field-programmable gate arrays (FPGAs). For devices with limited memory resources, Nucleus was designed to scale down to a memory size of <10 kilobytes (KBs) for both code and data. Nucleus 3.x introduced support for symmetric multiprocessing (SMP) and asymmetric multiprocessing (AMP) both unsupervised uAMP and supervised sAMP (using Mentor Embedded Hypervisor). Other additions in Nucleus 3.x: Integrated power management support for kernel and middleware components; includes support for DVFS, tick suppression, and sleep modes including hibernation. Process model for memory partitioning to support dynamic loading and unloading of application modules. Loadable processes are supported on both high end MPUs and low end MCUs with or without hardware memory management support. Wireless support IoT protocols Safety certification for aerospace, medical, industrial and automotive Support for ARM TrustZone Mentor embedded multi-core framework for IPC and processor life cycle management for AMP designs (both supervised sAMP and unsupervised uAMP) Runtime tracing support with host side analysis tools In addition to the new features in version 3.x, Nucleus moved business model from a la carte, to one unified package. Mentor acquired CodeSourcery in Dec 2010 to replace the EDGE development tools with the Sourcery CodeBench. Sourcery CodeBench comprises a compiler tool-chain, debugger, and trace analysis tools. The compiler tool-chain is based on GNU tool-chain. The debugger and integrated development environment (IDE) are based on Eclipse. Sourcery CodeBench supports ARM, IA-32, MIPS, and PPC architectures with built-in workflows and OS awareness for Nucleus RTOS and Mentor Embedded Linux. Nucleus 3.x introduced a unified build and configuration system with which the Kernel is configured through a single file and builds as a single library. Like menuconfig in Linux, a user interface (UI) based configuration tool integrated with CodeBench provides the user with graphically selectable components to customize the kernel at build time. The Nucleus configuration system allows for user customization to integrate new tool-chains, architecture support and build properties. Major components Nucleus RTOS components include: Kernel Services Connectivity File system Networking IoT Framework Wireless Security UI & graphics Kernel Real-time kernel with priority based pre-emptive scheduling Support for dynamic linking using loadable modules Interfaces for C++, Portable Operating System Interface (POSIX), and The Real-time Operating system Nucleus (TRON) microITRON SMP/AMP, supervised and unsupervised SMP support and runtime control for bound computation domain and affinities to processor cores for tasks and interrupts Support for 64-bit architectures Scaleable to fit memory constrained devices Built-in power management framework Source code for all components Services Run-level initialization and registry POSIX: kernel, networking, and file system Shell and tracing Debug agent C++ Power management services Connectivity Nucleus supports the ability to connect to other devices through various interfaces including: USB 2.0 and 3.0 USB Host, Function, and On-The-Go (OTG) stacks Bluetooth with many advanced profiles enabled (A2DP, AVRCP, HFP, HSP, etc.) Peripheral Component Interconnect (PCI), PCI-X and PCIe Controller Area Network (CAN) and CANopen Secure Digital (SDIO) SPI, QSPI Inter-Integrated Circuit (I²C) File system Unlike Windows and Unix-like operating systems, Nucleus does not need a file system to work. However, for complex uses needing local storage, Nucleus supports several file systems including FAT, SAFE (fault tolerant), and LWEXT. Multiple simultaneous file systems File Allocation Table (FAT) SAFE (high reliability power fail safe) LWEXT Install-able third-party file systems Multiple media support CD-ROM Hard drive RAM disk NOR and NAND flash USB drive SD MMC Nucleus provides support for different file systems and storage media though a virtual file system application programming interface (API) that allows access to the supported file systems and storage devices using the same functions calls regardless of the underlying storage format. Networking The Nucleus networking stack is a dual IPv4 and IPv6 stack that supports over 60 networking protocols. Nucleus networking stack supports POSIX and provides an easy to use socket based application interface. A brief list of the supported protocols include: Internet protocol suite (UDP, TCP/IP) Internet Control Message Protocol (ICMP), Dynamic Host Configuration Protocol (DHCP), network address translation (NAT) Point-to-Point Protocol (PPP) and Point-to-Point Protocol over Ethernet (PPPoE) File Transfer Protocol (FTP), Telnet, Secure Shell (SSH) Simple Network Management Protocol (SNMP), Network Time Protocol (NTP) Hypertext Transfer Protocol (HTTP) and HTTPS JSON-XML, WebSockets Security Nucleus supports a wide variety of encryption options for secure communications to protect data at rest or in transit. Nucleus ships with OpenSSL and an OpenSSL-like package wolfSSL (formerly CyaSSL) that is far smaller than OpenSSL for designs needing encryption but limited in memory capacity. Security protocols to protect data in transit include IPsec/IKE, SSH/SSL/TLS/DTLS. Encryption includes DES, 3DES, AES, SHA-256. Public-key cryptography algorithms include RSA. Support includes X.509, RADIUS, and 802.1X. Wireless Several Wi-Fi modules from different chip-makers like QCA, Broadcom, TI, and CSR are supported: IEEE 802.11 a/b/g/n IEEE 802.15.4 Bluetooth, Bluetooth LE UI graphics Nucleus 3.x supports OpenGL and leading 3rd party UI libraries. Nucleus supports the Qt UI framework which has been optimized for code size and integrated into CodeBench for debugging and tracing. Other UIs supported include Embedded Wizard and Socionext CGI Studio. IoT Recent releases of Nucleus include support for HTTPS, Constrained Application Protocol (CoAP), MQTT and 6LoWPAN. Nucleus has also announced support for Microsoft Azure cloud computing framework. Industrial Nucleus has been integrated with 3rd party industrial stacks from industry leaders. Industrial stack support includes OPC Unified Architecture (OPC UA) host and client and EtherNet/IP from Softing and EtherCAT from KoenigPa. Multi-core Nucleus supports asymmetric multiprocessing (AMP) mode and symmetric multiprocessing (SMP) mode for leading 32 and 64-bit heterogeneous multi-core SoCs. Nucleus is also capable of running as a GOS with Mentor Embedded Hypervisor. When operating in AMP mode, Nucleus RTOS can coexist with other instances of Nucleus, Linux, and/or bare machine (metal) programs distributed on the other processors. In this mode, each processor is running independently and behaves as a separate system within the SoC. Mentor Embedded Multicore Framework provides interprocess communication between operating systems on the various cores, and processor life cycle management. SMP operation entails having a instantiation of Nucleus RTOS manage multiple cores simultaneously. Nucleus can distribute its operations across all cores on a multi-core device, or any subset of cores. For this purpose Nucleus offers runtime API support for bound computation domain, and control tasks and interrupt affinities for core assignment. Product packages Nucleus RTOS is packaged as follows: Nucleus ReadyStart Edition ReadyStart which includes the runtime system, middleware, BSP (all in source code) and the IDE, debugger, compiling tools, trace bundle in a single package. Nucleus Ready Start comes in versions packaged for ARM, MIPS and PPC. Nucleus ReadyStart adds specialized eclipse plugins to CodeBench to provide simplified build and configuration workflows and debugging enhancements including kernel awareness, loadable module support, tracing and profiling tools. Nucleus Source Code Edition contains the runtime system and middleware packaged to support unique architectures and/or different tool chains Safety certification Nucleus SafetyCert has been certified for the highest levels of safety for DO-178C, IEC 61508, IEC 62304, and ISO 26262. Example devices using Nucleus products include: New Horizons, interplanetary space probe Honeywell for Critical Terrain Awareness Technology in the aviation industry IVL Technologies' On-Key Karaoke Handheld Player uses Nucleus PLUS Logitech uses it in its Pocket Video Portable Digital Video Cameras SK Telecom's first commercialization of code-division multiple access (CDMA) technology in Korea Mediatek Dual SIM Dual processor based chipsets found on most Chinese phones NEC High Definition Mobile Handset ASC's RBOX Multi-Service Aggregator Family uses Nucleus PLUS TI-Nspire series handheld calculators use Nucleus as the basis of their operating system Telephonics uses it in the USAF C-130 Avionics Modernization Program, SDI System, and the 767 Tanker Program, Aviation Communication System Garmin International to develop the CNX80 navigational Global Positioning System (GPS) for general aviation A large number of Motorola, Samsung, LG, Siemens/Benq, Sagem and NEC mobile phones The S-Class UI on LG Pop, Arena, etc. Intellon Home Plug AV Crestron Electronics on their older 2-series control system processors BSS Audio in their Soundweb London range. Later versions of Creative ZEN product line The Infineon S-Gold2 chipset used in Siemens phones: S75, E71, M81, etc. The Infineon S-Gold2 baseband chip used in Apple's iPhone The Metrotech i5000 Utility Locating Receiver The Creative Zen Vision line Intel Active Management Technology, vPro embedded controller Tandberg MXP video & telephony appliances Datex-Ohmeda Avance anesthesia system Zoll Medical Corporation defibrillators Samsung bada platform based devices Mindray early patient monitor, ultrasound device, and hematology analyzer See also Comparison of real-time operating systems References External links ARM operating systems Embedded operating systems Microkernel-based operating systems Microkernels MIPS operating systems Proprietary operating systems Real-time operating systems

Operating System (OS)

Mac OS X Tiger Mac OS X Tiger (version 10.4) is the fifth major release of macOS, Apple's desktop and server operating system for Mac computers. Tiger was released to the public on April 29, 2005 for US$129.95 as the successor to Mac OS X 10.3 Panther. Some of the new features included a fast searching system called Spotlight, a new version of the Safari web browser, Dashboard, a new 'Unified' theme, and improved support for 64-bit addressing on Power Mac G5s. Mac OS X 10.4 Tiger offered a number of features, such as fast file searching and improved graphics processing, that Microsoft had spent several years struggling to add to Windows with acceptable performance. Mac OS X 10.4 Tiger was included with all new Macs, and was also available as an upgrade for existing Mac OS X users, or users of supported pre-Mac OS X systems. The server edition, Mac OS X Server 10.4, was also available for some Macintosh product lines. Six weeks after its official release, Apple had delivered 2 million copies of Mac OS X 10.4 Tiger, representing 16% of all Mac OS X users. Apple claimed that Mac OS X 10.4 Tiger was the most successful Apple OS release in the company's history. At the WWDC on June 11, 2007, Apple's CEO, Steve Jobs, announced that out of the 22 million Mac OS X users, more than 67% were using Mac OS X 10.4 Tiger. Apple announced a transition to Intel x86 processors during Mac OS X 10.4 Tiger's lifetime, making it the first Apple operating system to work on Apple–Intel architecture machines. The original Apple TV, released in March 2007, shipped with a customized version of Mac OS X 10.4 Tiger branded "Apple TV OS" that replaced the usual GUI with an updated version of Front Row. Mac OS X 10.4 Tiger was succeeded by Mac OS X 10.5 Leopard on October 26, 2007, after 30 months, making Mac OS X 10.4 Tiger the longest running version of Mac OS X. The last security update released for Mac OS X 10.4 Tiger users was the 2009-005 update. The next security update, 2009-006 only included support for Mac OS X 10.5 Leopard and Mac OS X 10.6 Snow Leopard. The latest supported version of QuickTime is 7.6.4. The latest version of iTunes that can run on Mac OS X 10.4 Tiger is 9.2.1, because 10.0 only supports Mac OS X 10.5 Leopard and later. Safari 4.1.3 is the final version for Mac OS X 10.4 Tiger as of November 18, 2010. Despite not having received security updates since then, Mac OS X 10.4 Tiger remains popular with Power Mac users and retrocomputing enthusiasts due to its wide software and hardware compatibility, as it is the last Mac OS X version to support the Classic Environment, a Mac OS 9 compatibility layer, and PowerPC G3 processors. The Classic Environment isn't supported on Macs with Intel processors, as Mac OS 9 only supports PowerPC processors. System requirements Mac OS X 10.4 Tiger was initially available in a PowerPC edition, with an Intel edition released beginning at Mac OS X 10.4.4 Tiger. There is no universal version of the client operating system, although Mac OS X 10.4 Tiger Server was made available on a universal DVD from version Mac OS X 10.4.7 Tiger. While Apple shipped the PowerPC edition bundled with PowerPC-based Macs and also sold it as a separate retail box, the only way to obtain the Intel version was to buy an Intel-based Mac bundled with it. However, it was possible to buy the 'restore' DVDs containing the Intel version through unofficial channels such as eBay, and officially through Apple if one could provide proof of purchase of the appropriate Intel Mac. These grey-colored ‘restore’ DVDs supplied with new Macs, are designed to only restore on the model of Mac that they are intended for. However, they can be modified to work on any Intel Mac. The retail PowerPC-only DVD can be used on any PowerPC-based Mac supported by Mac OS X 10.4 Tiger. The system requirements of the PowerPC edition are: Macintosh computer with a PowerPC G3, G4 or G5 processor Built-in FireWire DVD drive for installation 256MB of RAM 3GB of available hard disk space (4GB if the user install the developer tools) Mac OS X 10.4 Tiger removed support for older New World ROM Macs such as the original iMacs and iBooks that were supported in Mac OS X 10.3 Panther; however it is possible to install Mac OS X 10.4 Tiger on these Macs using third-party software (such as XPostFacto) that overrides the checks made at the beginning of the installation process. Likewise, machines such as beige Power Mac G3s and ‘Wall Street’ PowerBook G3s that were dropped by Mac OS X 10.3 Panther can also be made to run both Mac OS X 10.3 Panther and Mac OS X 10.4 Tiger in this way. Also, Mac OS X 10.4 Tiger can be installed on unsupported New World ROM Macs by installing it on a supported Mac, then swapping hard drives. Old World ROM Macs require the use of XPostFacto to install Mac OS X 10.4 Tiger. Mac OS X 10.4 Tiger was the last version of Mac OS X to support the PowerPC G3 processor. History Apple CEO Steve Jobs first presented Mac OS X 10.4 Tiger in his keynote presentation at the WWDC on June 28, 2004, ten months before its commercial release in April 2005. Four months before that official release, several non-commercial, developer's releases of Mac OS X 10.4 Tiger leaked onto the internet via BitTorrent file sharers. It was first mentioned on Apple's website on May 4, 2004. Apple sued these file sharers. On April 12, 2005, Apple announced Mac OS X 10.4 Tiger's official, worldwide release would be April 29. All Apple Stores around the world held Mac OS X 10.4 Tiger seminars, presentations and demos. On June 6, 2005 at the WWDC in San Francisco, Jobs reported that nearly two million copies had been sold in Mac OS X 10.4 Tiger's first six weeks of release, making Mac OS X 10.4 Tiger the most successful operating system release in Apple's history. Jobs then disclosed that Mac OS X had been engineered from its inception to work with Intel's x86 line of processors in addition to the PowerPC, the CPU for which the operating system had always been publicly marketed. Apple concurrently announced its intent to release the first x86-based computers in June 2006, and to move the rest of its computers to x86 microprocessors by June 2007. On January 10, 2006, Apple presented its new iMac and MacBook Pro computers running on Intel Core Duo processors, and announced that the entire Apple product line would run on Intel processors by the end of 2006. Apple then released the Mac Pro and announced the new Xserve on August 8, completing the Intel transition in 210 days, roughly ten months ahead of the original schedule. Mac OS X 10.4 Tiger is the first version of Mac OS X to be supplied on a DVD, although the DVD could originally be exchanged for CDs for $9.95. It is also currently the only version of Mac OS X/OS X/macOS that had an update version number ending with a value greater than 9, as the last version of Mac OS X 10.4 Tiger was 10.4.11. New and changed features End-user features Apple advertises that Mac OS X 10.4 Tiger has over 150 new and improved features, including: Spotlight — Spotlight is a full-text and metadata search engine, which can search everything on one's Mac including Microsoft Word documents, iCal calendars and Address Book contact cards. The feature is also used to build the concept of ‘smart folders’ into the Finder. Spotlight will index files as they are saved, so they can be quickly and easily found through a search-as-you-type box in the menu bar. As a side-effect, it adds hidden folders and indexing files to removable media like USB flash drives. iChat AV — The new iChat AV 3.0 in Mac OS X 10.4 Tiger supports up to four participants in a video conference and ten participants in an audio conference. It also now supports communication using the XMPP protocol. A XMPP server called iChat Server is included on Mac OS X 10.4 Tiger Server. Safari RSS — The new Safari 2.0 web browser in Mac OS X 10.4 Tiger features a built-in reader for RSS and Atom web syndication that can be accessed easily from an RSS button in the address bar of the web browser window. An updated version of Safari, included as part of the free Mac OS X (10.4.3 Tiger update, can also pass the Acid2 web standards test. Mail 2 — The new version of Mail.app email client included in Mac OS X 10.4 Tiger featured an updated interface, "Smart Mailboxes", which utilizes the Spotlight search system, parental controls, as well as several other features. Dashboard — The Dashboard is a new mini-applications layer based on HTML, CSS, and JavaScript, which returns the desk accessories concept to the Mac OS. These accessories are known as widgets. It comes with several widgets such as Weather, World Clock, Unit Converter, and Dictionary/Thesaurus. More are available for free online. Its similarity to the Konfabulator application caused some criticism. Automator — A scripting tool to link applications together to form complex automated workflows (written in AppleScript, Cocoa, or both). Automator comes with a complete library of actions for several applications that can be used together to make a Workflow. VoiceOver — screen reader interface similar to Jaws for Windows and other Windows screen readers that offers the blind and visually impaired user keyboard control and spoken English descriptions of what is happening on screen. VoiceOver enables users with visual impairment to use applications via keyboard commands. VoiceOver is capable of reading aloud the contents of files including web pages, mail messages and word processing files. Complete keyboard navigation lets the user control the computer with the keyboard rather than the mouse, a menu is displayed in a window showing all the available keyboard commands that can be used. A complete built-in Dictionary/Thesaurus based on the New Oxford American Dictionary, Second Edition, accessible through an application, Dictionary, a Dashboard widget, and as a system-wide command (see below). .Mac syncing — Though this is not a new feature, .Mac syncing in Tiger is much improved over Panther. Syncing tasks in Tiger are now accomplished through the .Mac system preferences pane rather than the iSync application. QuickTime 7 — A new version of Apple's multimedia software has support for the new H.264/AVC codec, which offers better quality and scalability than other video codecs. This new codec is used by iChat AV for clearer video conferencing. New classes within Cocoa provide full access to QuickTime for Cocoa application developers. The new QuickTime 7 player application bundled with Tiger now includes more advanced audio and video controls as well as a more detailed Information dialog, and the new player has been rebuilt using Apple's Cocoa API to take advantage of the new technologies more easily. New Unix features — New versions of cp, mv, and rsync that support files with resource forks. Command-line support for features like the above-mentioned Spotlight are also included. Xcode 2.0 — Xcode 2.0, Apple's Cocoa development tool now includes visual modelling, an integrated Apple Reference Library and graphical remote debugging. New applications in Tiger Automator — Automator uses workflows to process repetitive tasks automatically Grapher — Grapher is a new application capable of creating 2D and 3D graphs similar to those of Graphing Calculator. Dictionary — A dictionary and thesaurus program that uses the New Oxford American Dictionary. It has a fast GUI for displaying the Dictionary, and allows the user to search the dictionary with Spotlight, to print definitions, and to copy and paste text into documents. Dictionary also provides a Dictionary service in the Application menu, and Cocoa and WebKit provides a global keyboard shortcut (ctrl-⌘-D by default) for all applications that display text with them. Its use was furthered in the next version of OS X by providing definitions from Wikipedia. The Dictionary application is a more feature-filled version of the Dictionary widget. Quartz Composer — Quartz Composer is a development tool for processing and rendering graphical data. AU Lab — AU Lab is a developer application for testing and mixing Audio Units. Dashboard — Dashboard is a widget application. Tiger widgets include: a calculator, dictionary, a world clock, a calendar, and more (full list). Users can also download and install more widgets. Improvements An upgraded kernel with optimized kernel resource locking and access control lists, and with support for 64-bit userland address spaces on machines with 64-bit processors. An updated libSystem with both 32-bit and 64-bit versions; combined with the aforementioned kernel change, this allows individual applications to address more than 4 GB of memory when run on 64-bit processors, although an application using Apple libraries or frameworks other than libSystem would need to have two processes, one running the 64-bit code and one running the code that requires other libraries and frameworks. A new startup daemon called launchd that allows for faster booting. The printing dialog in Tiger now features a drop down menu for creating PDFs, sending PDFs to Mail, and other PDF related actions. However, the user interface was criticized for creating a hybrid widget that looks like a plain button but acts like a pop-up menu. This is one of only three places in the entire Mac OS X interface where such an element appears. Dock menus now have menu items to open an application at login, or to remove the icon from the dock. The Window menu in the Finder now features a "Cycle Through Windows" menu item. The Get Info window for items in the Finder now includes a "More Info" section that includes Spotlight information tags such as Image Height & Width, when the file was last opened, and where the file originated. Early development of resolution independence. Apple notes that this will be a user-level feature in a future version of Mac OS X. Among the changes, the maximum size of icons was increased to 256x256. However, the Finder does not yet support this size. Technologies A new graphics processing API, Core Image, leveraging the power of the available accelerated graphics cards. Core Image allows programmers to easily leverage programmable GPUs for fast image processing for special effects and image correction tools. Some of the included Image Units are Blur, Color Blending, Generator Filters, Distortion Filters, Geometry Filters, Halftone features and much more. A new data persistence API, Core Data, that makes it easier for developers to handle structured data in their applications. The Mac OS X Core Data API helps developers create data structures for their applications. Core Data provides undo, redo and save functions for developers without them having to write any code. A new video graphics API, Core Video, which leverages Core Image to provide real-time video processing. Apple's Motion real-time video effects program takes advantage of Core Video in Tiger. Core Video lets developers easily integrate real-time video effects and processing into their applications. Core Audio integrates a range of audio functionality directly into the operating system. Interface differences In Tiger, the menu bar displayed at the top of the screen now features a colored Spotlight button in the upper right corner; the menu itself has a smoother 'glassy' texture to replace the faint pinstripes in Panther. Also of note, Tiger introduces a new window theme, often described as 'Unified'. A variation on the standard, non-brushed metal theme used since the introduction of Mac OS X, this theme integrates the title bar and the toolbar of a window. A prominent example of an application that utilizes this theme is Mail. Accessibility Tiger was the first version of Mac OS X to include the "Zoom" screen magnifier functionality, which allowed the user to zoom on to the area around the mouse by holding CONTROL and scrolling the mouse wheel up or down (to zoom in and out respectively). Tiger trademark lawsuit Shortly before the release of Mac OS X Tiger, the computer retailer TigerDirect.com, Inc. filed a lawsuit against Apple, alleging that Apple infringed TigerDirect.com's trademark with the Mac OS X Tiger operating system. The following is a quotation from TigerDirect.com's court memorandum: Apple Computer's use of its infringing family of Tiger marks to expand sales of products besides its operating system software is already evident — for example, Apple Computer is offering free iPods and laptops as part of its Tiger World Premiere giveaway. In short, notwithstanding its representation to the PTO that it would only use Tiger in connection with their unique computer operating system software, Apple Computer has in recent weeks used a family of Tiger marks in connection with a substantially broader group of products and services, including the very products and services currently offered by Tiger Direct under its famous family of Tiger marks. In 2005 TigerDirect was denied a preliminary injunction that would have prevented Apple from using the mark while the case was decided. Apple and TigerDirect reached a settlement in 2006, after which TigerDirect withdrew its opposition. Support for Intel processors At Apple's 2005 Worldwide Developers Conference, CEO Steve Jobs announced that the company would begin selling Mac computers with Intel x86 processors in 2006. To allow developers to begin producing software for these Intel-based Macs, Apple made available a prototype Intel-based Mac ("Developer Transition Kit") that included a version of Mac OS X v10.4.1 designed to run on x86 processors. This build included Apple's Rosetta compatibility layer — a translation process that allows x86-based versions of the OS to run software designed for PowerPC with a moderate performance penalty. This is contrasted with the contemporary Mac OS 9 Classic mode, which used comparably larger amounts of system resources. Soon after the Developer Transition Kits began shipping, copies of Tiger x86 were leaked onto file sharing networks. Although Apple had implemented a Trusted Computing DRM scheme in the transition hardware and OS in an attempt to stop people installing Tiger x86 on non-Apple PCs, the OSx86 project soon managed to remove this restriction. As Apple released each update with newer safeguards to prevent its use on non-Apple hardware, unofficially modified versions were released that circumvented Apple's safeguards. However, with the release of 10.4.5, 10.4.6, and 10.4.7 the unofficially modified versions continued to use the kernel from 10.4.4 because later kernels have hardware locks and depend heavily on EFI. By late 2006, the 10.4.8 kernel had been cracked. At MacWorld San Francisco 2006, Jobs announced the immediate availability of Mac OS X v10.4.4, the first publicly available release of Tiger compiled for both PowerPC- and Intel x86-based machines. Release history References External links Ars Technica Mac OS X Tiger Review at Ars Technica Mac OS X Tiger at Wikibooks 4 IA-32 operating systems X86-64 operating systems PowerPC operating systems 2005 software Computer-related introductions in 2005

Operating System (OS)

System call In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the kernel of the operating system on which it is executed. This may include hardware-related services (for example, accessing a hard disk drive or accessing the device's camera), creation and execution of new processes, and communication with integral kernel services such as process scheduling. System calls provide an essential interface between a process and the operating system. In most systems, system calls can only be made from userspace processes, while in some systems, OS/360 and successors for example, privileged system code also issues system calls. Privileges The architecture of most modern processors, with the exception of some embedded systems, involves a security model. For example, the rings model specifies multiple privilege levels under which software may be executed: a program is usually limited to its own address space so that it cannot access or modify other running programs or the operating system itself, and is usually prevented from directly manipulating hardware devices (e.g. the frame buffer or network devices). However, many applications need access to these components, so system calls are made available by the operating system to provide well-defined, safe implementations for such operations. The operating system executes at the highest level of privilege, and allows applications to request services via system calls, which are often initiated via interrupts. An interrupt automatically puts the CPU into some elevated privilege level and then passes control to the kernel, which determines whether the calling program should be granted the requested service. If the service is granted, the kernel executes a specific set of instructions over which the calling program has no direct control, returns the privilege level to that of the calling program, and then returns control to the calling program. The library as an intermediary Generally, systems provide a library or API that sits between normal programs and the operating system. On Unix-like systems, that API is usually part of an implementation of the C library (libc), such as glibc, that provides wrapper functions for the system calls, often named the same as the system calls they invoke. On Windows NT, that API is part of the Native API, in the library; this is an undocumented API used by implementations of the regular Windows API and directly used by some system programs on Windows. The library's wrapper functions expose an ordinary function calling convention (a subroutine call on the assembly level) for using the system call, as well as making the system call more modular. Here, the primary function of the wrapper is to place all the arguments to be passed to the system call in the appropriate processor registers (and maybe on the call stack as well), and also setting a unique system call number for the kernel to call. In this way the library, which exists between the OS and the application, increases portability. The call to the library function itself does not cause a switch to kernel mode and is usually a normal subroutine call (using, for example, a "CALL" assembly instruction in some Instruction set architectures (ISAs)). The actual system call does transfer control to the kernel (and is more implementation-dependent and platform-dependent than the library call abstracting it). For example, in Unix-like systems, fork and execve are C library functions that in turn execute instructions that invoke the fork and exec system calls. Making the system call directly in the application code is more complicated and may require embedded assembly code to be used (in C and C++), as well as requiring knowledge of the low-level binary interface for the system call operation, which may be subject to change over time and thus not be part of the application binary interface; the library functions are meant to abstract this away. On exokernel based systems, the library is especially important as an intermediary. On exokernels, libraries shield user applications from the very low level kernel API, and provide abstractions and resource management. IBM's OS/360 and DOS/360 implement most system calls through a library of assembly language macros, although there are a few services with a call linkage. This reflects their origin at a time when programming in assembly language was more common than high-level language usage. IBM system calls were therefore not directly executable by high-level language programs, but required a callable assembly language wrapper subroutine. Since then, IBM has added many services that can be called from high level languages in, e.g., z/OS and z/VSE. Examples and tools On Unix, Unix-like and other POSIX-compliant operating systems, popular system calls are open, read, write, close, wait, exec, fork, exit, and kill. Many modern operating systems have hundreds of system calls. For example, Linux and OpenBSD each have over 300 different calls, NetBSD has close to 500, FreeBSD has over 500, Windows has close to 2000, divided between win32k (graphical) and ntdll (core) system calls while Plan 9 has 51. Tools such as strace, ftrace and truss allow a process to execute from start and report all system calls the process invokes, or can attach to an already running process and intercept any system call made by the said process if the operation does not violate the permissions of the user. This special ability of the program is usually also implemented with system calls such as ptrace or system calls on files in procfs. Typical implementations Implementing system calls requires a transfer of control from user space to kernel space, which involves some sort of architecture-specific feature. A typical way to implement this is to use a software interrupt or trap. Interrupts transfer control to the operating system kernel, so software simply needs to set up some register with the system call number needed, and execute the software interrupt. This is the only technique provided for many RISC processors, but CISC architectures such as x86 support additional techniques. For example, the x86 instruction set contains the instructions SYSCALL/SYSRET and SYSENTER/SYSEXIT (these two mechanisms were independently created by AMD and Intel, respectively, but in essence they do the same thing). These are "fast" control transfer instructions that are designed to quickly transfer control to the kernel for a system call without the overhead of an interrupt. Linux 2.5 began using this on the x86, where available; formerly it used the INT instruction, where the system call number was placed in the EAX register before interrupt 0x80 was executed. An older mechanism is the call gate; originally used in Multics and later, for example, see call gate on the Intel x86. It allows a program to call a kernel function directly using a safe control transfer mechanism, which the operating system sets up in advance. This approach has been unpopular on x86, presumably due to the requirement of a far call (a call to a procedure located in a different segment than the current code segment) which uses x86 memory segmentation and the resulting lack of portability it causes, and the existence of the faster instructions mentioned above. For IA-64 architecture, EPC (Enter Privileged Code) instruction is used. The first eight system call arguments are passed in registers, and the rest are passed on the stack. In the IBM System/360 mainframe family, and its successors, a Supervisor Call instruction (), with the number in the instruction rather than in a register, implements a system call for legacy facilities in most of IBM's own operating systems, and for all system calls in Linux. In later versions of MVS, IBM uses the Program Call (PC) instruction for many newer facilities. In particular, PC is used when the caller might be in Service Request Block (SRB) mode. The PDP-11 minicomputer used the and instructions, which, similar to the IBM System/360 and x86 , put the code in the instruction; they generate interrupts to specific addresses, transferring control to the operating system. The VAX 32-bit successor to the PDP-11 series used the , , and instructions to make system calls to privileged code at various levels; the code is an argument to the instruction. Categories of system calls System calls can be grouped roughly into six major categories: Process control create process (for example, fork on Unix-like systems, or NtCreateProcess in the Windows NT Native API) terminate process load, execute get/set process attributes wait for time, wait event, signal event allocate and free memory File management create file, delete file open, close read, write, reposition get/set file attributes Device management request device, release device read, write, reposition get/set device attributes logically attach or detach devices Information maintenance get/set total system information (including time, date, computer name, enterprise etc.) get/set process, file, or device metadata (including author, opener, creation time and date, etc.) Communication create, delete communication connection send, receive messages transfer status information attach or detach remote devices Protection get/set file permissions Processor mode and context switching System calls in most Unix-like systems are processed in kernel mode, which is accomplished by changing the processor execution mode to a more privileged one, but no process context switch is necessary although a privilege context switch does occur. The hardware sees the world in terms of the execution mode according to the processor status register, and processes are an abstraction provided by the operating system. A system call does not generally require a context switch to another process; instead, it is processed in the context of whichever process invoked it. In a multithreaded process, system calls can be made from multiple threads. The handling of such calls is dependent on the design of the specific operating system kernel and the application runtime environment. The following list shows typical models followed by operating systems: Many-to-one model: All system calls from any user thread in a process are handled by a single kernel-level thread. This model has a serious drawback any blocking system call (like awaiting input from the user) can freeze all the other threads. Also, since only one thread can access the kernel at a time, this model cannot utilize multiple cores of processors. One-to-one model: Every user thread gets attached to a distinct kernel-level thread during a system call. This model solves the above problem of blocking system calls. It is found in all major Linux distributions, macOS, iOS, recent Windows and Solaris versions. Many-to-many model: In this model, a pool of user threads is mapped to a pool of kernel threads. All system calls from a user thread pool are handled by the threads in their corresponding kernel thread pool. Hybrid model: This model implements both many to many and one to one models depending upon the choice made by the kernel. This is found in old versions of IRIX, HP-UX and Solaris. See also Linux kernel API VDSO Notes References External links Linux 64-bit system call reference/listing Up to kernel version 4.20 Linux system call reference Updated system call reference for Linux kernel 2.6.35.4, includes register and data structure references. Also for Linux kernel 4.14 64 bit and 32 bit. A list of modern Unix-like system calls Interactive Linux kernel map with main API functions and structures, PDF version Linux system calls system calls for Linux kernel 2.2, with IA-32 calling conventions How System Calls Work on Linux/i86 (1996, based on the 1993 0.99.2 kernel) Sysenter Based System Call Mechanism in Linux 2.6 (2006) Kernel command using Linux system calls, IBM developerWorks Choudhary, Amit; HOWTO for Implementing a System Call on Linux 2.6 Jorrit N. Herder, Herbert Bos, Ben Gras, Philip Homburg, and Andrew S. Tanenbaum, Modular system programming on Minix 3, ;login: 31, no. 2 (April 2006); 19-28, accessed March 5, 2018 A simple open Unix Shell in C language examples on System Calls under Unix Inside the Native API Windows NT Native API, including system calls Gulbrandsen, John; System Call Optimization with the SYSENTER Instruction, CodeGuru.com, 8 October 2004 Operating system technology Application programming interfaces

Operating System (OS)

NOS (software) NOS (Network Operating System) is a discontinued operating system with time-sharing capabilities, written by Control Data Corporation in the 1970s. NOS ran on the 60-bit CDC 6000 series of mainframe computers and their successors. NOS replaced the earlier CDC Kronos operating system of the 1970s. NOS was intended to be the sole operating system for all CDC machines, a fact CDC promoted heavily. NOS was replaced with NOS/VE on the 64-bit Cyber-180 systems in the mid-1980s. Version 1 of NOS continued to be updated until about 1981; NOS version 2 was released early 1982. Time-sharing commands ACCESS – selects the access subsystem APL – selects APL programing language ASCII – select fill 128-character ASCII ATTACH – links to a permanent file AUTO – automatically generate five-digit line numbers BASIC – selects BASIC system BATCH – selects the batch system BEGIN – starts processing of CCL procedure (control language file) BINARY – selects binary input mode BRIEF – suppresses headers BYE – log off the system CALL – starts processing KCL procedure file (control language before CCL) CATLIST – lists user's permanent files CHANGE – changes parameters of a permanent file CHARGE – set charge number and project number CLEAR – releases all local files CONVERT – converts character sets (CR) – Carriage Return – requests terminal status if it is the first thing on a line CSET – selects the terminal character-set mode DAYFILE – lists a record of the user's activity DEBUG – activates or terminates CYBER interactive Debug DEFINE – create a direct-access permanent file DIAL – sends a one-line message to another terminal EDIT – Selects the text editor ENQUIRE – Requests the current job status EXECUTE – selects the Execute subsystem FORTRAN – selects the FORTRAN subsystem (FORTRAN 5) FTNTS – Selects the FORTRAN Extended Version 4 compiler (CDC's enhanced version of FORTRAN 4) FULL – Selects full-duplex mode GET – gets a copy of a permanent file GOODBYE – same as BYE HALF – clears full-duplex mode HELLO – logs out and starts login HELP – gets descriptions of NOS commands LENGTH – requests the length of a file LIB – get a copy of a permanent file LIMITS – lists the user's limits LIST – lists the contents of a file LNH – same as LIST except no headers LOGIN – same as HELLO LOGOUT – same as BYE MONITOR – connects to a terminal NEW – creates a new primary file NORMAL – clears modes set by ASCII, AUTO, BRIEF, NOSORT, CSET, PARITY, and TAPE NOSORT – prevents the system from sorting the primary file on the subsequent command NULL – selects the null subsystem. OLD – gets a copy of a permanent file P – proceed PACK – compress a file with several logical records into one logical record PACKNAM – direct subsequent file requests to an auxiliary device PARITY – set terminal parity PASSWOR – change user password PERMIT – grants another user permission to access a file PRIMARY – makes temporary file the new primary file PURGE – removes permanent files RECOVER – allows user to resume after terminal was disconnected RENAME – changes file name REPLACE – replace the contents of a permanent file with a temporary file RESEQ – resequece or add line numbers to the primary file SAVE – save a file permanently SETASL – sets SRU account block limit (SRU = System Resurce Unit, on hard drive) SETTL – set CPU time limit SORT – sort the primary file STATUS – same as ENQUIRE STOP – terminates currently running programs SUBMIT – submit a batch job deck image TRAN – select NOS transaction subsystem USER – get terminal number X – process a time-sharing command as a batch command XEDIT – select XEDIT editor From NOS Version 1 Terminal User's Instant Manual, CDC, 1975-1980. See also CDC Kronos CDC SCOPE CDC display code References NOS Discontinued operating systems Time-sharing operating systems

Operating System (OS)

Osiris (software) Osiris Serverless Portal System (usually abbreviated as Osiris sps or Osiris) is a freeware program used to create web portals distributed via peer-to-peer networking (P2P) and autonomous from centralized servers. It is available for Microsoft Windows and Linux operating systems. Unlike common tools used to publish information on the Internet, such as content management systems, Internet forums or blogs based on a centralized system, the data of an Osiris portal are shared (via P2P) between all its participants. Because all the contents necessary for navigation are replicated on every computer, the portal can be used without a central server. Thus, the portal is always accessible because it is immune to denial of service attacks, Internet service provider limitations (such as traffic shaping and censorship) and hardware failure. In this way, a web portal can be operated at very low costs and free from external control. History Osiris was started by a developer named "Berserker" as an outgrowth of KeyForum. Osiris was written in C++ and designed to be decentralized, indestructible and expand beyond a simple a web forum. "Clodo" joined the project several months later. Osiris was officially announced on October 2, 2006 after 2 years of development. The team is composed of 2 developers (Clodo & Berserker), two employees (DanielZ and Rei.Andrea) and a group of supporters/beta-testers (many of whom were already on the team KeyForum). Starting from version 0.12, Osiris has become multi-platform, this was possible by migrating from the Visual Studio to the wxWidgets library. Key features Osiris is the result of a union between peer-to-peer (P2P) technology and web portals. It allows anyone to create a web portal for free, without depending on anyone or needing special technical knowledge. Allows one to create content anonymously, allowing one to contribute to freedom of expression and speech. Osiris offers a full-text search engine that allows searching across all portals' content. Low resource utilization: with the increase of users in a portal there is a reduction of the workload on single nodes, as work is distributed among all network nodes. Uses P2P infrastructure (based on Kademlia) for the portals distribution, a field where there are few and difficult-to-use alternatives. Administration is based on the reputations system, which is a new way to manage users in a distributed system without using central servers. Basic concepts Osiris differs from classic P2P programs in that it is focused on security and distributed data management. Security The system is anonymous. It is not possible to make an association between a user and their IP address, hence one cannot trace the person who created a content. Even with physical access to an Osiris installation it is impossible to trace the actual user without knowing his password. 2048-bit digital keys guarantee the authenticity of content (digitally signed in order to prevent counterfeiting) and the confidentiality of private messages (encrypted between the sender and recipient). To prevent the ISP from intercepting traffic, connections and data transfer to a portal (called alignment), Osiris uses random ports which are cloaked during handshake and encrypted point-to-point via 256-bit AES. The P2P distribution allows content to be present in multiple copies as a guarantee of survival in case of hardware failure or nodes off-line. As the portals are saved locally, one can read the contents even if one works off-line. Reputations system The Reputations system and the subsequent generation of multiple points of view of a portal is one of the most innovative aspects of the program. Unlike "traditional" systems where the computational work (calculation of statistics, indexing of content, etc.) is always made by a central server, Osiris use a distributed approach, where the majority of the works is made by users of a portal, due to this there may be more distinct points of view of a portal, depending on used account. Each user is free to give reputation (positive or negative) to another user according to its contribution to the portal, based on these reputations, the system processes the pages by removing the contents of users evaluated negatively (such as spammers) and importing the reputations of users considered positively. This allow the creation of a network of assessments that allows management of a portal. Note that each client processes the data independently on its machine in a process that is called stabilization of the portal. Monarchist and anarchists portals When a user creates an Osiris portal, the user must choose between two systems of moderation, namely "anarchist" and "monarchy". The choice cannot be changed after the portal is created. In an anarchic portal, every user can rate another user and thus influence that user's reputation among all users of the portal. In this way, a portal can be moderated without the use of a central server. The first reputation is always positive and is set to the administrator, the user who publishes the invitation link (digitally signed) to the portal. In a monarchy portal, only the portal administrator and moderators can generate reputations, and delete or promote contents on the portal. Isis Gateway Isis is a web gateway to Osiris portals, written in PHP 5, through which it is possible to browse a portal without installing Osiris. The particularity of Isis is the management of the workload and the data, which don't lie on the public server that is running Isis, but is managed by the various nodes running Osiris. Isis only forwards web requests from visitors to the nodes that have become available to it, minimizing the use of resources from the server through the load-balancing of requests. Since it is not technically possible to guarantee anonymity in this type of architecture, all accesses by Isis are read-only. This has the dual objective of ensuring the privacy of users and encourage the use of Osiris to actively participate to a portal. Future plans Version 0.15 is available on Linux and Windows and a beta version for OS X is available. Osiris developers are considering an on-disk data management system called the "survival engine". The system would automatically delete content as needed to keep the database lightweight and improve speed / stability of the portal. Optimizations focusing on system alignment and stabilization to make it faster and less resource-intensive. On March 18, 2010, Osiris SPS developers announced that they are planning to migrate Osiris SPS into a GPL licensed open source software project in the following months. However, as of 15 September 2013, the source code has not been made available and the 1.x series has not been released. On December 10, 2014, Osiris SPS developers have announced 1.0 alpha version and discussed the software design problems. It has been proposed by donator/developer of Osiris to create a Kickstarter funding campaign, because the software design improvements would require a lot of resources. See also Peer-to-peer web hosting Forum Anonymous P2P Freenet Syndie References External links Support Forum Osiris official forum Anonymous file sharing networks Distributed data storage 2006 software Software that uses wxWidgets

Operating System (OS)

ISO/IEC 42010 ISO/IEC/IEEE 42010 Systems and software engineering — Architecture description is an international standard for architecture descriptions of systems and software. Overview ISO/IEC/IEEE 42010:2011 defines requirements on the description of system, software and enterprise architectures. It aims to standardise the practice of architecture description by defining standard terms, presenting a conceptual foundation for expressing, communicating and reviewing architectures and specifying requirements that apply to architecture descriptions, architecture frameworks and architecture description languages. Following its predecessor, IEEE 1471, the standard makes a strict distinction between architectures and architecture descriptions. The description of ISO/IEC/IEEE 42010 in this article is based upon the standard published in 2011. History of ISO/IEC/IEEE 42010 The origin of the standard was the fast track international standardization of IEEE 1471:2000. The standard was originally balloted as ISO/IEC DIS 25961. It was subsequently adopted and published as ISO/IEC 42010:2007 which was identical with IEEE 1471:2000. In 2006, ISO/IEC JTC1/SC7 WG 42 and IEEE Computer Society launched a coordinated revision of this standard to address: harmonization with ISO/IEC 12207 and ISO/IEC 15288; alignment with other ISO architecture standards (e.g. ISO/IEC 10746 Reference Model Open Distributed Processing); the specification of architecture frameworks and architecture description languages; architecture decision capture; and correspondences for model and view consistency. In July 2011, the Final Draft International Standard was balloted and approved (21-0) by ISO member bodies. The corresponding IEEE version, P42010/D9, was approved as a revised standard by the IEEE-SA Standards Board on 31 October 2011. ISO/IEC/IEEE 42010:2011 was published by ISO on 24 November 2011. References External links ISO/IEC/IEEE 42010 website A documentation framework for architecture decisions based on 42010 Views and Beyond: The SEI Approach to Architecture Documentation MEGAF is an infrastructure for realizing architecture frameworks that conform to the definition of architecture framework provided in the ISO/IEC/IEEE 42010 standard. 42010 42010 42010 Software architecture

Operating System (OS)

AV Linux AV Linux is a Linux-based operating system aimed for multimedia content creators. Available for the i386 and x86-64 architectures with a kernel customised for maximum performance and low-latency audio production, it has been recommended as a supported Linux platform for Harrison Mixbus. Environment The system is built on top of Debian, and was originally made with remastersys. Versions prior to, and including, version 6 were 32-bit only, running a 32-bit Linux kernel with the IRQ threading and rtirq-init patches activated by default. For computers with more than 4 GB of RAM there was a PAE version available. From AV Linux 2016 onwards, there are both 32-bit and 64-bit versions available. Window management as of version 6.0.2 is handled by the Xfce Desktop Environment. Previous versions used the LXDE Desktop Environment. It is possible to boot AV Linux from either a live CD or a hard drive. Audio playback and routing is handled by JACK (for advanced audio operation) or ALSA (for basic audio operation). Most any audio interface compatible with FFADO is usable out of the box. Software AV Linux is bundled with software for both everyday use and media production. As of AV Linux 2016, AV Linux gets its software packages from the KXStudio repositories, which are compatible with Debian, and therefore AV Linux. This reduces duplication of effort and allows the effort focus to be on a solid base distribution suitable for audio production. For this reason, AV Linux 2016 development has focused more on the base distribution than bundling it with large amounts of software, as it did with previous versions. Instead, the 2016 edition leaves it up to the users to decide what they want to install from the large repository of software available via KXStudio. Audio Preinstalled audio software includes: Ardour, Audacity, Calf Studio Gear, Carla, Guitarix, Hydrogen and MuseScore. Graphics Preinstalled graphics programs include: GIMP, Inkscape and Shotwell. Video Preinstalled software for video editing, playback, capture and 3D animation include: Blender, Cinelerra, Kdenlive and Openshot. Everyday use For typical day-to-day activities there are several programs available including Firefox and LibreOffice Suite. Forum AV Linux has an active forum. The forum was closed in September 2019 despite the development of AV Linux being expected to continue. Manual The maintainer of AV Linux, Glen MacArthur, also provides a thorough manual to complement AV Linux. This manual provides users with "84 illustrated pages of FAQ’s and important Operational details". Reception LinuxInsider: "The modified (Xfce) menus add a big element of ease to finding your most frequently used apps. The menu hierarchy uses a two-tiered design. this drastically cuts down on the need to rummage through long cascading menu lists" LinuxJournal: "AV Linux Control Panel... provides easy access to tools and utilities for system management, administration, and customization. Its amenities include an installer for ATI/nVidia binary video drivers and a very useful tool that scans and analyzes your system for its readiness for realtime performance." ZDNet: "Everything in AV Linux is aimed at reducing the operating system overhead, and leaving as much of the processing power as possible available for the multimedia editing applications." Softpedia Linux: "As mentioned before, the distribution provides users with a large collection of video and audio production software, ranging from simple audio and video players to sophisticated video editors and CD rippers. Additionally, it comes with a patched Linux kernel package that allows for low-latency audio performance. The Live DVD can be used as-is or installed on a local disk drive." Also review was written by InfoWorld. References External links AVLinux at DistroWatch LMP: The Advantages of Choosing an Audio Orientated Linux Distribution Debian-based distributions Linux media creation distributions Free audio software Free music software Free video software Free graphics software Linux distributions

Operating System (OS)

IBM System/360 architecture The IBM System/360 architecture is the model independent architecture for the entire S/360 line of mainframe computers, including but not limited to the instruction set architecture. The elements of the architecture are documented in the IBM System/360 Principles of Operation and the IBM System/360 I/O Interface Channel to Control Unit Original Equipment Manufacturers' Information manuals. Features The System/360 architecture provides the following features: 16 32-bit general-purpose registers 4 64-bit floating-point registers 64-bit processor status register (PSW), which includes a 24-bit instruction address 24-bit (16 MB) byte-addressable memory space Big-endian byte/word order A standard instruction set, including fixed-point binary arithmetic and logical instructions, present on all System/360 models (except the Model 20, see below). A commercial instruction set, adding decimal arithmetic instructions, is optional on some models, as is a scientific instruction set, which adds floating-point instructions. The universal instruction set includes all of the above plus the storage protection instructions and is standard for some models. The Model 44 provides a few unique instructions for data acquisition and real-time processing and is missing the storage-to-storage instructions. However, IBM offered a Commercial Instruction Set" feature that ran in bump storage and simulated the missing instructions. The Model 20 offers a stripped-down version of the standard instruction set, limited to eight general registers with halfword (16-bit) instructions only, plus the commercial instruction set, and unique instructions for input/output. The Model 67 includes some instructions to handle 32-bit addresses and "dynamic address translation", with additional privileged instructions to provide virtual memory. Memory Memory (storage) in System/360 is addressed in terms of 8-bit bytes. Various instructions operate on larger units called halfword (2 bytes), fullword (4 bytes), doubleword (8 bytes), quad word (16 bytes) and 2048 byte storage block, specifying the leftmost (lowest address) of the unit. Within a halfword, fullword, doubleword or quadword, low numbered bytes are more significant than high numbered bytes; this is sometimes referred to as big-endian. Many uses for these units require aligning them on the corresponding boundaries. Within this article the unqualified term word refers to a fullword. The original architecture of System/360 provided for up to 224 = 16,777,216 bytes of memory. The later Model 67 extended the architecture to allow up to 232 = 4,294,967,296 bytes of virtual memory. Addressing System/360 uses truncated addressing similar to that of the UNIVAC III. That means that instructions do not contain complete addresses, but rather specify a base register and a positive offset from the addresses in the base registers. In the case of System/360 the base address is contained in one of 15 general registers. In some instructions, for example shifts, the same computations are performed for 32-bit quantities that are not addresses. Data formats The S/360 architecture defines formats for characters, integers, decimal integers and hexadecimal floating point numbers. Character and integer instructions are mandatory, but decimal and floating point instructions are part of the Decimal arithmetic and Floating-point arithmetic features. Characters are stored as 8-bit bytes. Integers are stored as two's complement binary halfword or fullword values. Packed decimal numbers are stored as 1 to 16 8-bit bytes containing an odd number of decimal digits followed by a 4-bit sign. Sign values of hexadecimal A, C, E, and F are positive and sign values of hexadecimal B and D are negative. Digit values of hexadecimal A-F and sign values of 0-9 are invalid, but the PACK and UNPK instructions do not test for validity. Zoned decimal numbers are stored as 1 to 16 8-bit bytes, each containing a zone in bits 0-3 and a digit in bits 4-7. The zone of the rightmost byte is interpreted as a sign. Floating point numbers are only stored as fullword or doubleword values on older models. On the 360/85 and 360/195 there are also extended precision floating point numbers stored as quadwords. For all three formats, bit 0 is a sign and bits 0-7 are a characteristic (exponent, biased by 64). Bits 8-31 (8-63) are a hexadecimal fraction. For extended precision, the low order doubleword has its own sign and characteristic, which are ignored on input and generated on output. Instruction formats Instructions in the S/360 are two, four or six bytes in length, with the opcode in byte 0. Instructions have one of the following formats: RR (two bytes). Generally byte 1 specifies two 4-bit register numbers, but in some cases, e.g., SVC, byte 1 is a single 8-bit immediate field. RS (four bytes). Byte 1 specifies two register numbers; bytes 2-3 specify a base and displacement. RX (four bytes). Bits 0-3 of byte 1 specify either a register number or a modifier; bits 4-7 of byte 1 specify the number of the general register to be used as an index; bytes 2-3 specify a base and displacement. SI (four bytes). Byte 1 specifies an immediate field; bytes 2-3 specify a base and displacement. SS (six bytes). Byte 1 specifies two 4-bit length fields or one 8-bit length field; bytes 2-3 and 4-5 each specify a base and displacement. The encoding of the length fields is length-1. Instructions must be on a two-byte boundary in memory; hence the low-order bit of the instruction address is always 0. Program Status Word (PSW) The Program Status Word (PSW) contains a variety of controls for the currently operating program. The 64-bit PSW describes (among other things) the address of the current instruction being executed, condition code and interrupt masks. Load Program Status Word (LPSW) is a privileged instruction that loads the Program Status Word (PSW), including the program mode, protection key, and the address of the next instruction to be executed. LPSW is most often used to "return" from an interruption by loading the "old" PSW which is associated with the interruption class. Other privileged instructions (e.g., SSM, STNSM, STOSM, SPKA, etcetera) are available for manipulating subsets of the PSW without causing an interruption or loading a PSW; and one non-privileged instruction (SPM) is available for manipulating the program mask. Interruption system The architecture defines 5 classes of interruption. An interruption is a mechanism for automatically changing the program state; it is used for both synchronous and asynchronous events. There are two storage fields assigned to each class of interruption on the S/360; an old PSW double-word and a new PSW double-word. The processor stores the PSW, with an interruption code inserted, into the old PSW location and then loads the PSW from the new PSW location. This generally replaces the instruction address, thereby effecting a branch, and (optionally) sets and/or resets other fields within the PSW, thereby effecting a mode change. The S/360 architecture defines a priority to each interruption class, but it is only relevant when two interruptions occur simultaneously; an interruption routine can be interrupted by any other enabled interruption, including another occurrence of the initial interruption. For this reason, it is normal practice to specify all of the mask bits, with the exception of machine-check mask bit, as 0 for the "first-level" interruption handlers. "Second-level" interruption handlers are generally designed for stacked interruptions (multiple occurrences of interruptions of the same interruption class). Input/Output interruption An I/O interruptionPoOps occurs at the completion of a channel program, after fetching a CCW with the PCI bit set and also for asynchronous events detected by the device, control unit or channel, e.g., completion of a mechanical movement. The system stores the device address into the interruption code and stores channel status into the CSW at location 64 ('40'X). Program interruption A Program interruption occurs when an instruction encounters one of 15 exceptions; however, if the Program Mask bit corresponding to an exception is 0 then there is no interruption for that exception. On 360/65, 360/67 and 360/85 the Protection Exception and Addressing Exception interruptions can be imprecise, in which case they store an Instruction Length Code of 0. The Interruption code may be any of An operation exceptionPoOps is recognized when a program attempts to execute an instruction with an opcode that the computer does not implement. In particular, an operation exception is recognized when a program is written for an optional feature, e.g., floating point, that is not installed. A privileged operation exceptionPoOps is recognized when a program attempts to execute a privileged instruction when the problem state bit in the PSW is 1. An execute exceptionPoOps is recognized when the operand of an EXECUTE instruction (EX) is another EXECUTE instruction. A protection exceptionPoOps is recognized when a program attempts to store into a location whose storage protect key does not match the PSW key, or to fetch from a fetch protected location whose storage protect key does not match the PSW key. An addressing exceptionPoOps is recognized when a program attempts to access a storage location that is not currently available. This normally occurs with an address beyond the capacity of the machine, but it may also occur on machines that allow blocks of storage to be taken offline. A specification exceptionPoOps is recognized when an instruction has a length or register field with values not permitted by the operation, or when it has an operand address that does not satisfy the alignment requirements of the opcode, e.g., a LH instruction with an odd operand address on a machine without the byte alignment feature. A data exceptionPoOps is recognized when a decimal instruction specifies invalid operands, e.g., invalid data, invalid overlap. A fixed-point overflow exceptionPoOps is recognized when significant bits are lost in a fixed point arithmetic or shift instruction, other than divide. A fixed-point divide exceptionPoOps is recognized when significant bits are lost in a fixed point divide or Convert to Binary instruction. A decimal overflow exceptionPoOps is recognized when significant digits are lost in a decimal arithmetic instruction, other than divide. A decimal divide exceptionPoOps is recognized when significant bits are lost in a decimal divide instruction. The destination is not altered. An exponent overflow exceptionPoOps is recognized when the characteristic in a floating-point arithmetic operation exceeds 127 and the fraction is not zero. An exponent underflow exceptionPoOps is recognized when the characteristic in a floating-point arithmetic operation is negative and the fraction is not zero. A significance exceptionPoOps is recognized when the fraction in a floating-point add or subtract operation is zero. A floating-point divide exceptionPoOps is recognized when the fraction in the divisor of a floating-point divide operation is zero. Supervisor Call interruption A Supervisor Call interruptionPoOps occurs as the result of a Supervisor Call instruction; the system stores bits 8-15 of the SVC instruction as the Interruption Code. External interruption An ExternalPoOps interruption occurs as the result of certain asynchronous events. Bits 16-24 of the External Old PSW are set to 0 and one or more of bits 24-31 is set to 1 Machine Check interruption A Machine Check interruptionPoOps occurs to report unusual conditions associated with the channel or CPU that cannot be reported by another class of interruption. The most important class of conditions causing a Machine Check is a hardware error such as a parity error found in registers or storage, but some models may use it to report less serious conditions. Both the interruption code and the data stored in the scanout area at '80'x (128 decimal) are model dependent. Input/Output This article describes I/O from the CPU perspective. It does not discuss the channel cable or connectors, but there is a summary elsewhere and details can be found in the IBM literature. I/O is carried out by a conceptually separate processor called a channel. Channels have their own instruction set, and access memory independently of the program running on the CPU. On the smaller models (through 360/50) a single microcode engine runs both the CPU program and the channel program. On the larger models the channels are in separate cabinets and have their own interfaces to memory. A channel may contain multiple subchannels, each containing the status of an individual channel program. A subchannel associated with multiple devices that cannot concurrently have channel programs is referred to as shared; a subchannel representing a single device is referred to as unshared. There are three types of channels on the S/360: A byte multiplexer channel is capable of executing multiple CCWs concurrently; it is normally used to attach slow devices such as card readers and telecommunications lines. A byte multiplexer channel could have a number of selector subchannels, each with only a single subchannel, which behave like low-speed selector channels. A selector channel has only a single subchannel, and hence is only capable of executing one channel command at a time. It is normally used to attach fast devices that are not capable of exploiting a block multiplexer channel to suspend the connection, such as magnetic tape drives. A block multiplexer channel is capable of concurrently running multiple channel programs, but only one at a time can be active. The control unit can request suspension at the end of a channel command and can later request resumption. This is intended for devices in which there is a mechanical delay after completion of data transfer, e.g., for seeks on moving-head DASD. The block multiplexer channel was a late addition to the System/360 architecture; early machines had only byte multiplexer channels and selector channels. The block multiplexer channel was an optional feature only on the models 85 and 195. The block multiplexor channel was also available on the later System/370 computers. Conceptually peripheral equipment is attached to a S/360 through control units, which in turn are attached through channels. However, the architecture does not require that control units be physically distinct, and in practice they are sometimes integrated with the devices that they control. Similarly, the architecture does not require the channels to be physically distinct from the processor, and the smaller S/360 models (through 360/50) have integrated channels that steal cycles from the processor. Peripheral devices are addressed with 16-bit addresses., referred to as cua or cuu; this article will use the term cuu. The high 8 bits identify a channel, numbered from 0 to 6, while the low 8 bits identify a device on that channel. A device may have multiple cuu addresses. Control units are assigned an address "capture" range. For example, a CU might be assigned range 20-2F or 40-7F. The purpose of this is to assist with the connection and prioritization of multiple control units to a channel. For example, a channel might have three disk control units at 20-2F, 50-5F, and 80-8F. Not all of the captured addresses need to have an assigned physical device. Each control unit is also marked as High or Low priority on the channel. Device selection progresses from the channel to each control unit in the order they are physically attached to their channel. At the end of the chain the selection process continues in reverse back towards the channel. If the selection returns to the channel then no control unit accepted the command and SIO returns Condition Code 3. Control units marked as High Priority check the outbound CUU to be within their range. If so, then the I/O was processed. If not, then the selection was passed to the next outbound CU. Control units marked as Low Priority check for inbound (returning) CUU to be within their range. If so, then the I/O is processed. If not, then the selection is passed to the next inbound CU (or the channel). The connection of three controls unit to a channel might be physically -A-B-C and, if all are marked as High then the priority would be ABC. If all are marked low then the priority would be CBA. If B was marked High and AC low then the order would be BCA. Extending this line of reasoning then the first of N controllers would be priority 1 (High) or 2N-1 (Low), the second priority 2 or 2N-2, the third priority 3 or 2N-3, etc. The last physically attached would always be priority N. There are three storage fields reserved for I/O; a double word I/O old PSW, a doubleword I/O new PSW and a fullword Channel Address Word (CAW). Performing an I/O normally requires the following: initializing the CAW with the storage key and the address of the first CCW issuing a Start I/O (SIO) instruction that specifies the cuu for the operation waiting for an I/O interruption handling any unusual conditions indicated in the Channel Status Word (CSW) A channel program consists of a sequence of Channel Control Words (CCWs) chained together (see below.) Normally the channel fetches CCWs from consecutive doublewords, but a control unit can direct the channel to skip a CCW and a Transfer In Channel (TIC) CCW can direct the channel to start fetching CCWs from a new location. There are several defined ways for a channel command to complete. Some of these allow the channel to continue fetching CCWs, while others terminate the channel program. In general, if the CCW does not have the chain-command bit set and is not a TIC, then the channel will terminate the I/O operation and cause an I/O interruption when the command completes. Certain status bits from the control unit suppress chaining. The most common ways for a command to complete are for the count to be exhausted when chain-data is not set and for the control unit to signal that no more data transfers should be made. If Suppress-Length-Indication (SLI) is not set and one of those occurs without the other, chaining is not allowed. The most common situations that suppress chaining are unit-exception and unit-check. However, the combination of unit-check and status-modifier does not suppress chaining; rather, it causes the channel to do a command retry, reprocessing the same CCW. In addition to the interruption signal sent to the CPU when an I/O operation is complete, a channel can also send a Program-Controlled interruption (PCI) to the CPU while the channel program is running, without terminating the operation, and a delayed device-end interruption after the I/O completion interruption. Channel status These conditions are detected by the channel and indicated in the CSW.PoOps Program-controlled interruptionPoOps indicates that the channel has fetched a CCW with the PCI bit set. The channel continues processing; this interruption simply informs the CPU of the channel's progress. An example of the use of Program-controlled interruption is in the "Program Fetch" function of Contents Supervision, whereby the control program is notified that a Control/Relocation Record has been read. To ensure that this record has been completely read into main storage, a "disabled bit spin", one of the few which remains in the control program, is initiated. Satisfaction of the spin indicates that the Control/Relocation Record is completely in main storage and the immediately preceding Text Record may be relocated. After relocation, a NOP CCW is changed to a TIC and the channel program continues. In this way, an entire load module may be read and relocated while utilizing only one EXCP, and possibly only one revolution of the disk drive. PCI also has applications in teleprocessing access method buffer management. Incorrect lengthPoOps indicates that the data transfer for a command completed before the Count was exhausted. This indication is suppressed if the Suppress-Length-Indication bit in the CCW is set. Program checkPoOps indicates one of the following errors Nonzero bits where zeros are required An invalid data or CCW address The CAW or a TIC refers to a TIC Protection checkPoOps indicates that the protection key in the CAW is non-zero and does not match the storage protection key. Channel data checkPoOps indicates a parity error during a data transfer. Channel control checkPoOps indicates a channel malfunction other than Channel data check or Interface control check. Interface control checkPoOps indicates an invalid signal in the channel to control unit interface. Chaining checkPoOps indicates lost data during data chaining. Unit status These conditions are presented to the channel by the control unit or device.PoOps In some cases they are handled by the channel and in other cases they are indicated in the CSW. There is no distinction between conditions detected by the control unit and conditions detected by the device. AttentionPoOps indicates an unusual condition not associated with an ongoing channel program. It often indicates some sort of operator action like requesting input, in which case the CPU would respond by issuing a read-type command, most often a sense command (04h) from which additional information could be deduced. Attention is a special condition, and requires specific operating system support, and for which the operating system has a special attention table with a necessarily limited number of entries. Status modifierPoOps (SM) indicates one of three unusual conditions A Test I/O instruction was issued to a device that does not support it. A Busy status refers to the control unit rather than to the device. A device has detected a condition that requires skipping a CCW. A CCW with a command for which Status Modifier is possible will normally specify command chaining, in which case the SM is processed by the channel and does not cause an interruption. A typical channel program where SM occurs is ... Search Id Equal TIC *-8 Read Data where the TIC causes the channel to refetch the search until the device indicates a successful search by raising SM. Control unit endPoOps indicates that a previous control unit busy status has been cleared. BusyPoOps indicates that a device (SM=0) or a control unit (SM=1) is busy. Channel endPoOps indicates that the device has completed the data transfer for a channel command. There may also be an Incorrect length indication if the Count field of the CCW is exhausted, depending on the value of the Suppress-Length-Indication bit. Device endPoOps indicates that the device has completed an operation and is ready to accept another. DE may be signalled concurrently with CE or may be delayed. Unit checkPoOps indicates that the device or control unit has detected an unusual conditions and that details may be obtained by issuing a Sense command. Unit exceptionPoOps indicates that the device has detected an unusual condition, e.g., end of file. Channel Address Word The fullword Channel Address Word (CAW) contains a 4-bit storage protection key and a 24-bit address of the channel program to be started. Channel Command Word A Channel Command Word is a doubleword containing the following: an 8-bit channel Command CodePoOps a 24-bit addressPoOps a 5-bit flag fieldPoOps an unsigned halfword Count fieldPoOps CCW Command codes The low order 2 or 4 bits determine the six types of operations that the channel performs;. The encoding is The meaning of the high order six or four bits, the modifier bits, M in the table above, depends upon the type of I/O device attached, see e.g., DASD CKD CCWs. All eight bits are sent to and interpreted in the associated control unit (or its functional equivalent). Control is used to cause a state change in a device or control unit, often associated with mechanical motion, e.g., rewind, seek. Sense is used to read data describing the status of the device. The most important case is that when a command terminates with unit check, the specific cause can only be determined by doing a Sense and examining the data returned. A Sense command with the modifier bits all zero is always valid. A noteworthy deviation from the architecture is that DASD use Sense command codes for Reserve and Release, instead of using Control. CCW flags The flags in a CCW affect how it executes and terminates. Channel Status Word The Channel Status Word (CSW) provides data associated with an I/O interruption. The Protection Key field contains the protect key from the CAW at the time that the I/O operation was initiated for I/O complete or PCI interruptions.PoOps The Command Address field contains the address+8 of the last CCW fetched for an I/O complete or PCI interruption. However, there are 9 exceptionsPoOps. The Status field contains one byte of Channel status bits, indicating conditions detected by the channelPoOps, and one byte of Unit status bits, indicating conditions detected by the I/O unitPoOps. There is no distinction between conditions detected by the control unit and conditions detected by the device. The Residual Count is a half word that gives the number of bytes in the area described by the CCW that have not been transferred to or from the channelPoOps. The difference between the count in the CCW and the residual count gives the number of bytes transferred. Operator controls The architecture of System/360 specified the existence of several common functions, but did not specify their means of implementation. This allowed IBM to use different physical means, e.g., dial, keyboard, pushbutton, roller, image or text on a CRT, for selecting the functions and values on different processors. Any reference to key or switch should be read as applying to, e.g., a light-pen selection, an equivalent keyboard sequence. System Reset sends a reset signal on every I/O channel and clears the processor state; all pending interruptions are cancelled. System Reset is not guaranteed to correct parity errors in general registers, floating point registers or storage. System Reset does not reset the state of shared I/O devices. Initial Program Load (IPL)PoOps is a process for loading a program when there isn't a loader available in storage, usually because the machine was just powered on or to load an alternative operating system. This process is sometimes known as Booting. As part of the IPL facility the operator has a means of specifying a 12-bit device address, typically with three dials as shown in the operator controls drawing. When the operator selects the Load function, the system performs a System Reset, sends a Read IPL channel command to the selected device in order to read 24 bytes into locations 0-23 and causes the channel to begin fetching CCWs at location 8; the effect is as if the channel had fetched a CCW with a length of 24, and address of 0 and the flags containing Command Chaining + Suppress Length Indication. At the completion of the operation, the system stores the I/O address in the halfword at location 2 and loads the PSW from location 0. Initial program loading is typically done from a tape, a card reader, or a disk drive. Generally, the operating system was loaded from a disk drive; IPL from tape or cards was used only for diagnostics or for installing an operating system on a new computer. Emergency pull switchPoOps (Emergency power off, EPO) sends an EPO signal to every I/O channel, then turns off power to the processor complex. Because EPO bypasses the normal sequencing of power down, damage can result, and the EPO control has a mechanical latch to ensure that a customer engineer inspects the equipment before attempting to power it back on. Power onPoOps powers up all components of the processor complex and performs a system reset. Power offPoOps initiates an orderly power-off sequence. Although the contents of storage are preserved, the associated storage keys may be lost. The Interrupt keyPoOps causes an external interruption with bit 25 set in the External Old PSW. The Wait lightPoOps indicates that the PSW has bit 14 (wait) set; the processor is temporarily halted but resumes operation when an interruption condition occurs. The Manual lightPoOps indicates that the CPU is in a stopped state. The System lightPoOps indicates that a meter is running, either due to CPU activity or due to I/O channel activity. The Test lightPoOps indicates that certain operator controls are active, when certain facilities, e.g., INSTRUCTION STEP, have been used by a Diagnose instruction or when abnormal thermal conditions exist. The details are model dependent. The Load lightPoOps is turned on by IPL and external start. It is turned off by loading the PSW from location 0 at the completion of the load process. The Load unitPoOps controls provide the rightmost 11 bits of the device from which to perform an IPL. The Load KeyPoOps starts the IPL sequence. The Prefix Select Key SwitchPoOps selects whether IPL will used the primary prefix or the alternative prefix. The System-Reset KeyPoOps initiates a System Reset. The Stop KeyPoOps puts the CPU in a stopped state; channel programs continue running and interruption conditions remain pending. The Rate SwitchPoOps determines the mode in which the processor fetches instructions. Two modes are defined by the architecture: PROCESS INSTRUCTION STEP The Start KeyPoOps initiates instruction fetching in accordance with the setting of the Rate Switch. The Storage-Select SwitchPoOps determines the type of resource accessed by the Store Key and Display Key. Three selections are defined by the architecture: Main storage General registers Floating-point registers The Address SwitchesPoOps specify the address or register number for the Store Key, Display Key and, on some models, the Set IC Key.. The Data SwitchesPoOps specify the data for the Store Key and, on some models, the Set IC Key. The Store KeyPoOps stores the value in the Data Switches as specified by the Storage-Select Switch and the Address Switches. The Display KeyPoOps displays the value specified by the Storage-Select Switch and the Address Switches. The Set IC=PoOps sets the instruction address portion of the PSW from the Data Switches or the Address Switches, depending on the model. The Address-Compare SwitchesPoOps select the mode of comparison and what is compared. Stop on instruction address compare is present on all models, but stop on data address compare is only present on some models. The Alternate-Prefix LightPoOps is on when the prefix trigger is in the alternate state. Optional features Byte-aligned operands On some models the alignment requirements for some problem-state instructions were relaxed. There is no mechanism to turn off this feature, and programs depending on receiving a program check type 6 (alignment) on those instructions must be modified. Decimal arithmetic The decimal arithmetic feature provides instructions that operate on packed decimal data. A packed decimal number has 1-31 decimal digits followed by a 4-bit sign. All of the decimal arithmetic instructions except PACK and UNPACK generate a Data exception if a digit is not in the range 0-9 or a sign is not in the range A-F. Direct Control The Direct ControlPoOps feature provides six external signal lines and an 8-bit data path to/from storage. Floating-point arithmetic The floating-point arithmetic feature provides 4 64-bit floating point registers and instructions to operate on 32 and 64 bit hexadecimal floating point numbers. The 360/85 and 360/195 also support 128 bit extended precision floating point numbers. Interval timer If the interval timer feature is installed, the processor decrements the word at location 80 ('50'X) at regular intervals; the architecture does not specify the interval but does require that value subtracted make it appear as though 1 were subtracted from bit 23 300 times per second. The smaller models decremented at the same frequency (50 Hz or 60 Hz) as the AC power supply, but larger models had a high resolution timer feature. The processor causes an External interruption when the timer goes to zero. Multi-system operationMulti-system operation''PoOps is a set of features to support multi-processor systems, e.g., Direct Control, direct address relocation (prefixing). Storage protection If the storage protection feature is installed, then there is a 4-bit storage key associated with every 2,048-byte block of storage and that key is checked when storing into any address in that block by either a CPU or an I/O channel. A CPU or channel key of 0 disables the check; a nonzero CPU or channel key allows data to be stored only in a block with the matching key. Storage Protection was used to prevent a defective application from writing over storage belonging to the operating system or another application. This permitted testing to be performed along with production. Because the key was only four bits in length, the maximum number of different applications that could be run simultaneously was 15. An additional option available on some models was fetch protection. It allowed the operating system to specify that blocks were protected from fetching as well as from storing. Deviations and extensions The System/360 Model 20 is radically different and should not be considered to be a S/360. The System/360 Model 44 is missing certain instructions, but a feature allowed the missing instructions to be simulated in hidden memory thus allowing the use of standard S/360 operating systems and applications. Some models have features that extended the architecture, e.g., emulation instructions, paging, and some models make minor deviations from the architecture. Examples include: The multisystem feature on the S/360-65 which modifies the behavior of the direct control feature and of the Set System Mask (SSM) instruction. The System/360 Model 67-2 had similar, but incompatible, changes. Some deviations served as prototypes for features of the S/370 architecture. See also Memory protection key Notes ReferencesS360''' Further reading Chapter 3 (pp. 41110) describes the System/360 architecture. External links Introduction to IBM System/360 Architecture (Student Text) Computer architecture Computing platforms architecture Instruction set architectures Computer-related introductions in 1964

Operating System (OS)

IBM System/360 The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applications and to cover a complete range of applications from small to large. The design distinguished between architecture and implementation, allowing IBM to release a suite of compatible designs at different prices. All but the only partially compatible Model 44 and the most expensive systems use microcode to implement the instruction set, which features 8-bit byte addressing and binary, decimal, and hexadecimal floating-point calculations. The System/360 family introduced IBM's Solid Logic Technology (SLT), which packed more transistors onto a circuit card, allowing more powerful but smaller computers to be built. The slowest System/360 model announced in 1964, the Model 30, could perform up to 34,500 instructions per second, with memory from 8 to 64 KB. High-performance models came later. The 1967 IBM System/360 Model 91 could execute up to 16.6 million instructions per second. The larger 360 models could have up to 8 MB of main memory, though that much main memory was unusual—a large installation might have as little as 256 KB of main storage, but 512 KB, 768 KB or 1024 KB was more common. Up to 8 megabytes of slower (8 microsecond) Large Capacity Storage (LCS) was also available for some models. The IBM 360 was extremely successful in the market, allowing customers to purchase a smaller system with the knowledge they would be able to move to larger ones if their needs grew, without reprogramming application software or replacing peripheral devices. Its design influenced computer design for years to come; many consider it one of the most successful computers in history. The chief architect of System/360 was Gene Amdahl, and the project was managed by Fred Brooks, responsible to Chairman Thomas J. Watson Jr. The commercial release was piloted by another of Watson's lieutenants, John R. Opel, who managed the launch of IBM’s System 360 mainframe family in 1964. Application-level compatibility (with some restrictions) for System/360 software is maintained to the present day with the System z mainframe servers. System/360 history A family of computers Contrasting with industry practice of the day, IBM created an entire new series of computers, from small to large, low- to high-performance, all using the same instruction set (with two exceptions for specific markets). This feat allowed customers to use a cheaper model and then upgrade to larger systems as their needs increased without the time and expense of rewriting software. Before the introduction of System/360, business and scientific applications used different computers with different instruction sets and operating systems. Different-sized computers also had their own instruction sets. IBM was the first manufacturer to exploit microcode technology to implement a compatible range of computers of widely differing performance, although the largest, fastest models had hard-wired logic instead. This flexibility greatly lowered barriers to entry. With most other vendors customers had to choose between machines they could outgrow and machines that were potentially too powerful and thus too costly. This meant that many companies simply did not buy computers. Models IBM initially announced a series of six computers and forty common peripherals. IBM eventually delivered fourteen models, including rare one-off models for NASA. The least expensive model was the Model 20 with as little as 4096 bytes of core memory, eight 16-bit registers instead of the sixteen 32-bit registers of other System/360 models, and an instruction set that was a subset of that used by the rest of the range. The initial announcement in 1964 included Models 30, 40, 50, 60, 62, and 70. The first three were low- to middle-range systems aimed at the IBM 1400 series market. All three first shipped in mid-1965. The last three, intended to replace the 7000 series machines, never shipped and were replaced with the 65 and 75, which were first delivered in November 1965, and January 1966, respectively. Later additions to the low-end included models 20 (1966, mentioned above), 22 (1971), and 25 (1968). The Model 20 had several sub-models; sub-model 5 was at the higher end of the model. The Model 22 was a recycled Model 30 with minor limitations: a smaller maximum memory configuration, and slower I/O channels, which limited it to slower and lower-capacity disk and tape devices than on the 30. The Model 44 (1966) was a specialized model, designed for scientific computing and for real-time computing and process control, featuring some additional instructions, and with all storage-to-storage instructions and five other complex instructions eliminated. A succession of high-end machines included the Model 67 (1966, mentioned below, briefly anticipated as the 64 and 66), 85 (1969), 91 (1967, anticipated as the 92), 95 (1968), and 195 (1971). The 85 design was intermediate between the System/360 line and the follow-on System/370 and was the basis for the 370/165. There was a System/370 version of the 195, but it did not include Dynamic Address Translation. The implementations differed substantially, using different native data path widths, presence or absence of microcode, yet were extremely compatible. Except where specifically documented, the models were architecturally compatible. The 91, for example, was designed for scientific computing and provided out-of-order instruction execution (and could yield "imprecise interrupts" if a program trap occurred while several instructions were being read), but lacked the decimal instruction set used in commercial applications. New features could be added without violating architectural definitions: the 65 had a dual-processor version (M65MP) with extensions for inter-CPU signalling; the 85 introduced cache memory. Models 44, 75, 91, 95, and 195 were implemented with hardwired logic, rather than microcoded as all other models. The Model 67, announced in August 1965, was the first production IBM system to offer dynamic address translation (virtual memory) hardware to support time-sharing. "DAT" is now more commonly referred to as an MMU. An experimental one-off unit was built based on a model 40. Before the 67, IBM had announced models 64 and 66, DAT versions of the 60 and 62, but they were almost immediately replaced with the 67 at the same time that the 60 and 62 were replaced with the 65. DAT hardware would reappear in the S/370 series in 1972, though it was initially absent from the series. Like its close relative, the 65, the 67 also offered dual CPUs. IBM stopped marketing all System/360 models by the end of 1977. Backward compatibility IBM's existing customers had a large investment in software that executed on second-generation machines. Several models offered the option of emulation of the customer's previous computer using a combination of special hardware, special microcode and an emulation program that used the emulation instructions to simulate the target system, so that old programs could run on the new machine. Customers initially had to halt the computer and load the emulation program. IBM later added features and modified emulator programs to allow emulation of the 1401, 1440, 1460, 1410 and 7010 under the control of an operating system. The Model 85 and later System/370 maintained the precedent, retaining emulation options and allowing emulator programs to execute under operating system control alongside native programs. Successors and variants System/360 (excepting the Model 20) was replaced with the compatible System/370 range in 1970 and Model 20 users were targeted to move to the IBM System/3. (The idea of a major breakthrough with FS technology was dropped in the mid-1970s for cost-effectiveness and continuity reasons.) Later compatible IBM systems include the 4300 family, the 308x family, the 3090, the ES/9000 and 9672 families (System/390 family), and the IBM Z series. Computers that were mostly identical or compatible in terms of the machine code or architecture of the System/360 included Amdahl's 470 family (and its successors), Hitachi mainframes, the UNIVAC 9000 series, Fujitsu as the Facom, the RCA Spectra 70 series, and the English Electric System 4. The System 4 machines were built under license to RCA. RCA sold the Spectra series to what was then UNIVAC, where they became the UNIVAC Series 70. UNIVAC also developed the UNIVAC Series 90 as successors to the 9000 series and Series 70. The Soviet Union produced a System/360 clone named the ES EVM. The IBM 5100 portable computer, introduced in 1975, offered an option to execute the System/360's APL.SV programming language through a hardware emulator. IBM used this approach to avoid the costs and delay of creating a 5100-specific version of APL. Special radiation-hardened and otherwise somewhat modified System/360s, in the form of the System/4 Pi avionics computer, are used in several fighter and bomber jet aircraft. In the complete 32-bit AP-101 version, 4 Pi machines were used as the replicated computing nodes of the fault-tolerant Space Shuttle computer system (in five nodes). The U.S. Federal Aviation Administration operated the IBM 9020, a special cluster of modified System/360s for air traffic control, from 1970 until the 1990s. (Some 9020 software is apparently still used via emulation on newer hardware.) Table of System/360 models Model summary Six of the twenty IBM System/360 models announced either were never shipped or were never released. Fourteen of the twenty IBM System/360 models announced shipped. Technical description Influential features The System/360 introduced a number of industry standards to the marketplace, such as: The 8-bit byte (against financial pressure during development to reduce the byte to 4 or 6 bits), rather than adopting the 7030 concept of accessing bytes of variable size at arbitrary bit addresses. Byte-addressable memory (as opposed to bit-addressable or word-addressable memory) 32-bit words The Bus and Tag I/O channel standardized in FIPS-60 Commercial use of microcoded CPUs The IBM Floating Point Architecture The EBCDIC character set Nine track magnetic tape Architectural overview The System/360 series has a computer system architecture specification. This specification makes no assumptions on the implementation itself, but rather describes the interfaces and expected behavior of an implementation. The architecture describes mandatory interfaces that must be available on all implementations, and optional interfaces. Some aspects of this architecture are: Big endian byte ordering A processor with 16 32-bit general purpose registers (R0-R15) A 64-bit program status word (PSW), which describes (among other things) Interrupt masks Privilege states A condition code A 24-bit instruction address An interruption mechanism, maskable and unmaskable interruption classes and subclasses An instruction set. Each instruction is wholly described and also defines the conditions under which an exception is recognized in the form of program interruption. A memory (called storage) subsystem with 8 bits per byte A special processor communication area starting at address 0 24-bit addressing Manual control operations that allow A bootstrap process (a process called Initial Program Load or IPL) Operator-initiated interrupts Resetting the system Basic debugging facilities Manual display and modifications of the system's state (memory and processor) An Input/Output mechanism - which does not describe the devices themselves Some of the optional features are: Binary-coded decimal instructions Floating point instructions Timing facilities (interval timer) Key-controlled memory protection All models of System/360, except for the Model 20 and Model 44, implemented that specification. Binary arithmetic and logical operations are performed as register-to-register and as memory-to-register/register-to-memory as a standard feature. If the Commercial Instruction Set option was installed, packed decimal arithmetic could be performed as memory-to-memory with some memory-to-register operations. The Scientific Instruction Set feature, if installed, provided access to four floating point registers that could be programmed for either 32-bit or 64-bit floating point operations. The Models 85 and 195 could also operate on 128-bit extended-precision floating point numbers stored in pairs of floating point registers, and software provided emulation in other models. The System/360 used an 8-bit byte, 32-bit word, 64-bit double-word, and 4-bit nibble. Machine instructions had operators with operands, which could contain register numbers or memory addresses. This complex combination of instruction options resulted in a variety of instruction lengths and formats. Memory addressing was accomplished using a base-plus-displacement scheme, with registers 1 through F (15). A displacement was encoded in 12 bits, thus allowing a 4096-byte displacement (0-4095), as the offset from the address put in a base register. Register 0 could not be used as a base register nor as an index register (nor as a branch address register), as "0" was reserved to indicate an address in the first 4 KB of memory, that is, if register 0 was specified as described, the value 0x00000000 was implicitly input to the effective address calculation in place of whatever value might be contained within register 0 (or if specified as a branch address register, then no branch was taken, and the content of register 0 was ignored, but any side effect of the instruction was performed). This specific behavior permitted initial execution of an interrupt routines, since base registers would not necessarily be set to 0 during the first few instruction cycles of an interrupt routine. It isn't needed for IPL ("Initial Program Load" or boot), as one can always clear a register without the need to save it. With the exception of the Model 67, all addresses were real memory addresses. Virtual memory was not available in most IBM mainframes until the System/370 series. The Model 67 introduced a virtual memory architecture, which MTS, CP-67, and TSS/360 used—but not IBM's mainline System/360 operating systems. The System/360 machine-code instructions are 2 bytes long (no memory operands), 4 bytes long (one operand), or 6 bytes long (two operands). Instructions are always situated on 2-byte boundaries. Operations like MVC (Move-Characters) (Hex: D2) can only move at most 256 bytes of information. Moving more than 256 bytes of data required multiple MVC operations. (The System/370 series introduced a family of more powerful instructions such as the MVCL "Move-Characters-Long" instruction, which supports moving up to 16 MB as a single block.) An operand is two bytes long, typically representing an address as a 4-bit nibble denoting a base register and a 12-bit displacement relative to the contents of that register, in the range 000–FFF (shown here as hexadecimal numbers). The address corresponding to that operand is the contents of the specified general-purpose register plus the displacement. For example, an MVC instruction that moves 256 bytes (with length code 255 in hexadecimal as FF) from base register 7, plus displacement 000, to base register 8, plus displacement 001, would be coded as the 6-byte instruction "D2FF 8001 7000" (operator/length/address1/address2). The System/360 was designed to separate the system state from the problem state. This provided a basic level of security and recoverability from programming errors. Problem (user) programs could not modify data or program storage associated with the system state. Addressing, data, or operation exception errors made the machine enter the system state through a controlled routine so the operating system could try to correct or terminate the program in error. Similarly, it could recover certain processor hardware errors through the machine check routines. Channels Peripherals interfaced to the system via channels. A channel is a specialized processor with the instruction set optimized for transferring data between a peripheral and main memory. In modern terms, this could be compared to direct memory access (DMA). The S/360 connects channels to control units with bus and tag cables; IBM eventually replaced these with (Enterprise Systems Connection (ESCON) and Fibre Connection (FICON) channels. Byte-multiplexor and selector channels There were initially two types of channels; byte-multiplexer channels (known at the time simply as "multiplexor channels"), for connecting "slow speed" devices such as card readers and punches, line printers, and communications controllers, and selector channels for connecting high speed devices, such as disk drives, tape drives, data cells and drums. Every System/360 (except for the Model 20, which was not a standard 360) has a byte-multiplexer channel and 1 or more selector channels, though the model 25 has just one channel, which can be either a byte-multiplexor or selector channel. The smaller models (up to the model 50) have integrated channels, while for the larger models (model 65 and above) the channels are large separate units in separate cabinets: the IBM 2870 is the byte-multiplexor channel with up to four selector sub-channels, and the IBM 2860 is up to three selector channels. The byte-multiplexer channel is able to handle I/O to/from several devices simultaneously at the device's highest rated speeds, hence the name, as it multiplexed I/O from those devices onto a single data path to main memory. Devices connected to a byte-multiplexer channel are configured to operate in 1-byte, 2-byte, 4-byte, or "burst" mode. The larger "blocks" of data are used to handle progressively faster devices. For example, a 2501 card reader operating at 600 cards per minute would be in 1-byte mode, while a 1403-N1 printer would be in burst mode. Also, the byte-multiplexer channels on larger models have an optional selector subchannel section that would accommodate tape drives. The byte-multiplexor's channel address was typically "0" and the selector subchannel addresses were from "C0" to "FF." Thus, tape drives on System/360 were commonly addressed at 0C0-0C7. Other common byte-multiplexer addresses are: 00A: 2501 Card Reader, 00C/00D: 2540 Reader/Punch, 00E/00F: 1403-N1 Printers, 010-013: 3211 Printers, 020-0BF: 2701/2703 Telecommunications Units. These addresses are still commonly used in z/VM virtual machines. System/360 models 40 and 50 have an integrated 1052-7 console that is usually addressed as 01F, however, this was not connected to the byte-multiplexer channel, but rather, had a direct internal connection to the mainframe. The model 30 attached a different model of 1052 through a 1051 control unit. The models 60 through 75 also use the 1052-7. Selector channels enabled I/O to high speed devices. These storage devices were attached to a control unit and then to the channel. The control unit let clusters of devices be attached to the channels. On higher speed models, multiple selector channels, which could operate simultaneously or in parallel, improved overall performance. Control units are connected to the channels with "bus and tag" cable pairs. The bus cables carried the address and data information and the tag cables identified what data was on the bus. The general configuration of a channel is to connect the devices in a chain, like this: Mainframe—Control Unit X—Control Unit Y—Control Unit Z. Each control unit is assigned a "capture range" of addresses that it services. For example, control unit X might capture addresses 40-4F, control unit Y: C0-DF, and control unit Z: 80-9F. Capture ranges had to be a multiple of 8, 16, 32, 64, or 128 devices and be aligned on appropriate boundaries. Each control unit in turn has one or more devices attached to it. For example, you could have control unit Y with 6 disks, that would be addressed as C0-C5. There are three general types of bus-and-tag cables produced by IBM. The first is the standard gray bus-and-tag cable, followed by the blue bus-and-tag cable, and finally the tan bus-and-tag cable. Generally, newer cable revisions are capable of higher speeds or longer distances, and some peripherals specified minimum cable revisions both upstream and downstream. The cable ordering of the control units on the channel is also significant. Each control unit is "strapped" as High or Low priority. When a device selection was sent out on a mainframe's channel, the selection was sent from X->Y->Z->Y->X. If the control unit was "high" then the selection was checked in the outbound direction, if "low" then the inbound direction. Thus, control unit X was either 1st or 5th, Y was either 2nd or 4th, and Z was 3rd in line. It is also possible to have multiple channels attached to a control unit from the same or multiple mainframes, thus providing a rich high-performance, multiple-access, and backup capability. Typically the total cable length of a channel is limited to 200 feet, less being preferred. Each control unit accounts for about 10 "feet" of the 200-foot limit. Block multiplexer channel IBM first introduced a new type of I/O channel on the Model 85 and Model 195, the 2880 block multiplexer channel, and then made them standard on the System/370. This channel allowed a device to suspend a channel program, pending the completion of an I/O operation and thus to free the channel for use by another device. A block multiplexer channel can support either standard 1.5 MB/second connections or, with the 2-byte interface feature, 3 MB/second; the latter use one tag cable and two bus cables. On the S/370 there is an option for a 3.0 MB/s data streaming channel with one bus cable and one tag cable. The initial use for this was the 2305 fixed-head disk, which has 8 "exposures" (alias addresses) and rotational position sensing (RPS). Block multiplexer channels can operate as a selector channel to allow compatible attachment of legacy subsystems. Basic hardware components Being uncertain of the reliability and availability of the then new monolithic integrated circuits, IBM chose instead to design and manufacture its own custom hybrid integrated circuits. These were built on 11 mm square ceramic substrates. Resistors were silk screened on and discrete glass encapsulated transistors and diodes were added. The substrate was then covered with a metal lid or encapsulated in plastic to create a "Solid Logic Technology" (SLT) module. A number of these SLT modules were then flip chip mounted onto a small multi-layer printed circuit "SLT card". Each card had one or two sockets on one edge that plugged onto pins on one of the computer's "SLT boards". This was the reverse of how most other company's cards were mounted, where the cards had pins or printed contact areas and plugged into sockets on the computer's boards. Up to twenty SLT boards could be assembled side-by-side (vertically and horizontally) to form a "logic gate". Several gates mounted together constituted a box-shaped "logic frame". The outer gates were generally hinged along one vertical edge so they could be swung open to provide access to the fixed inner gates. The larger machines could have more than one frame bolted together to produce the final unit, such as a multi-frame Central Processing Unit (CPU). Operating system software The smaller System/360 models used the Basic Operating System/360 (BOS/360), Tape Operating System (TOS/360), or Disk Operating System/360 (DOS/360, which evolved into DOS/VS, DOS/VSE, VSE/AF, VSE/SP, VSE/ESA, and then z/VSE). The larger models used Operating System/360 (OS/360). IBM developed several levels of OS/360, with increasingly powerful features: Primary Control Program (PCP), Multiprogramming with a Fixed number of Tasks (MFT), and Multiprogramming with a Variable number of Tasks (MVT). MVT took a long time to develop into a usable system, and the less ambitious MFT was widely used. PCP was used on intermediate machines too small to run MFT well, and on larger machines before MFT was available; the final releases of OS/360 included only MFT and MVT. For the System/370 and later machines, MFT evolved into OS/VS1, while MVT evolved into OS/VS2 (SVS) (Single Virtual Storage), then various versions of MVS (Multiple Virtual Storage) culminating in the current z/OS. When it announced the Model 67 in August 1965, IBM also announced TSS/360 (Time-Sharing System) for delivery at the same time as the 67. TSS/360, a response to Multics, was an ambitious project that included many advanced features. It had performance problems, was delayed, canceled, reinstated, and finally canceled again in 1971. Customers migrated to CP-67, MTS (Michigan Terminal System), TSO (Time Sharing Option for OS/360), or one of several other time-sharing systems. CP-67, the original virtual machine system, was also known as CP/CMS. CP/67 was developed outside the IBM mainstream at IBM's Cambridge Scientific Center, in cooperation with MIT researchers. CP/CMS eventually won wide acceptance, and led to the development of VM/370 (Virtual Machine) which had a primary interactive "sub" operating system known as VM/CMS (Conversational Monitoring System). This evolved into today's z/VM. The Model 20 offered a simplified and rarely used tape-based system called TPS (Tape Processing System), and DPS (Disk Processing System) that provided support for the 2311 disk drive. TPS could run on a machine with 8 KB of memory; DPS required 12 KB, which was pretty hefty for a Model 20. Many customers ran quite happily with 4 KB and CPS (Card Processing System). With TPS and DPS, the card reader was used to read the Job Control Language cards that defined the stack of jobs to run and to read in transaction data such as customer payments. The operating system was held on tape or disk, and results could also be stored on the tapes or hard drives. Stacked job processing became an exciting possibility for the small but adventurous computer user. A little-known and little-used suite of 80-column punched-card utility programs known as Basic Programming Support (BPS) (jocularly: Barely Programming Support), a precursor of TOS, was available for smaller systems. Component names IBM created a new naming system for the new components created for System/360, although well-known old names, like IBM 1403 and IBM 1052, were retained. In this new naming system, components were given four-digit numbers starting with 2. The second digit described the type of component, as follows: Peripherals IBM developed a new family of peripheral equipment for System/360, carrying over a few from its older 1400 series. Interfaces were standardized, allowing greater flexibility to mix and match processors, controllers and peripherals than in the earlier product lines. In addition, System/360 computers could use certain peripherals that were originally developed for earlier computers. These earlier peripherals used a different numbering system, such as the IBM 1403 chain printer. The 1403, an extremely reliable device that had already earned a reputation as a workhorse, was sold as the 1403-N1 when adapted for the System/360. Also available were optical character recognition (OCR) readers IBM 1287 and IBM 1288 which could read Alpha Numeric (A/N) and Numeric Hand Printed (NHP/NHW) Characters from Cashier's rolls of tape to full legal size pages. At the time this was done with very large optical/logic readers. Software was too slow and expensive at that time. Models 65 and below sold with an IBM 1052-7 as the console typewriter. The 360/85 with feature 5450 uses a display console that was not compatible with anything else in the line; the later 3066 console for the 370/165 and 370/168 use the same basic display design as the 360/85. The IBM System/360 models 91 and 195 use a graphical display similar to the IBM 2250 as their primary console. Additional operator consoles were also available. Certain high-end machines could optionally be purchased with a 2250 graphical display, costing upwards of US $100,000; smaller machines could use the less expensive 2260 display or later the 3270. Direct access storage devices (DASD) The first disk drives for System/360 were IBM 2302s and IBM 2311s. The first drum for System/360 was the IBM 7320. The 156 KB/second 2302 was based on the earlier 1302 and was available as a model 3 with two 112.79 MB modules or as a model 4 with four such modules. The 2311, with a removable 1316 disk pack, was based on the IBM 1311 and had a theoretical capacity of 7.2 MB, although actual capacity varied with record design. (When used with a 360/20, the 1316 pack was formatted into fixed-length 270 byte sectors, giving a maximum capacity of 5.4MB.) In 1966, the first 2314s shipped. This device had up to eight usable disk drives with an integral control unit; there were nine drives, but one was reserved as a spare. Each drive used a removable 2316 disk pack with a capacity of nearly 28 MB. The disk packs for the 2311 and 2314 were physically large by today's standards — e.g., the 1316 disk pack was about in diameter and had six platters stacked on a central spindle. The top and bottom outside platters did not store data. Data were recorded on the inner sides of the top and bottom platters and both sides of the inner platters, providing 10 recording surfaces. The 10 read/write heads moved together across the surfaces of the platters, which were formatted with 203 concentric tracks. To reduce the amount of head movement (seeking), data was written in a virtual cylinder from inside top platter down to inside bottom platter. These disks were not usually formatted with fixed-sized sectors as are today's hard drives (though this was done with CP/CMS). Rather, most System/360 I/O software could customize the length of the data record (variable-length records), as was the case with magnetic tapes. Some of the most powerful early System/360s used high-speed head-per-track drum storage devices. The 3,500 RPM 2301, which replaced the 7320, was part of the original System/360 announcement, with a capacity of 4 MB. The 303.8 KB/second IBM 2303 was announced on January 31, 1966, with a capacity of 3.913 MB. These were the only drums announced for System/360 and System/370, and their niche was later filled by fixed-head disks. The 6,000 RPM 2305 appeared in 1970, with capacities of 5 MB (2305-1) or 11 MB (2305-2) per module. Although these devices did not have large capacity, their speed and transfer rates made them attractive for high-performance needs. A typical use was overlay linkage (e.g. for OS and application subroutines) for program sections written to alternate in the same memory regions. Fixed head disks and drums were particularly effective as paging devices on the early virtual memory systems. The 2305, although often called a "drum" was actually a head-per-track disk device, with 12 recording surfaces and a data transfer rate up to 3 MB per second. Rarely seen was the IBM 2321 Data Cell, a mechanically complex device that contained multiple magnetic strips to hold data; strips could be randomly accessed, placed upon a cylinder-shaped drum for read/write operations; then returned to an internal storage cartridge. The IBM Data Cell [noodle picker] was among several IBM trademarked "speedy" mass online direct-access storage peripherals (reincarnated in recent years as "virtual tape" and automated tape librarian peripherals). The 2321 file had a capacity of 400 MB, at the time when the 2311 disk drive only had 7.2 MB. The IBM Data Cell was proposed to fill cost/capacity/speed gap between magnetic tapes—which had high capacity with relatively low cost per stored byte—and disks, which had higher expense per byte. Some installations also found the electromechanical operation less dependable and opted for less mechanical forms of direct-access storage. The Model 44 was unique in offering an integrated single-disk drive as a standard feature. This drive used the 2315 "ramkit" cartridge and provided 1,171,200 bytes of storage. Tape drives The 2400 tape drives consisted of a combined drive and control unit, plus individual 1/2" tape drives attached. With System/360, IBM switched from IBM 7 track to 9 track tape format. 2400 drives could be purchased that read and wrote 7-track tapes for compatibility with the older IBM 729 tape drives. In 1967, a slower and cheaper pair of tape drives with integrated control unit was introduced: the 2415. In 1968, the IBM 2420 tape system was released, offering much higher data rates, self-threading tape operation and 1600bpi packing density. It remained in the product line until 1979. Unit record devices Punched card devices included the 2501 card reader and the 2540 card reader punch. Virtually every System/360 had a 2540. The 2560 MFCM ("Multi-Function Card Machine") reader/sorter/punch, listed above, was for the Model 20 only. It was notorious for reliability problems (earning humorous acronyms often involving "...Card Muncher" or "Mal-Function Card Machine"). Line printers were the IBM 1403 and the slower IBM 1443. A paper tape reader, the IBM 2671, was introduced in 1964. It had a rated speed of 1,000 cps. There were also a paper tape reader and paper tape punch from an earlier era, available only as RPQs (Request Price Quotation). The 1054 (reader) and 1055 (punch), which were carried forward (like the 1052 console typewriter) from the IBM 1050 Teleprocessing System. All these devices operated at a maximum of 15.5 characters per second. The paper tape punch from the IBM 1080 System was also available by RPQ, but at a prohibitively expensive price. Optical character recognition (OCR) devices 1287 and later the 1288 were available on the 360's. The 1287 could read handwritten numerals, some OCR fonts, and cash register OCR paper tape reels. The 1288 'page reader' could handle up to legal size OCR font typewritten pages, as well as handwritten numerals. Both of these OCR devices employed a 'flying spot' scanning principle, with the raster scan provided by a large CRT, and the reflected light density changes were picked up by a high gain photomultiplier tube. Magnetic ink character recognition (MICR) was provided by the IBM 1412 and 1419 cheque sorters, with magnetic ink printing (for cheque books) on 1445 printers (a modified 1443 that used an MICR ribbon). 1412/1419 and 1445 were mainly used by banking institutions. Remaining machines Despite having been sold or leased in very large numbers for a mainframe system of its era only a few of System/360 computers remain mainly as non-operating property of museums or collectors. Examples of existing systems include: The Computer History Museum in Mountain View, California has a non-working Model 30 on display, as do the Museum of Transport and Technology (Motat) in Auckland, New Zealand and the Vienna University of Technology in Austria. The University of Western Australia Computer Club has a complete Model 40 in storage. The KCG Computer Museum of Kyoto Computer Gakuin, Japan's first computer school in town, has an IBM System/360 Model 40 on display. Two IBM System/360 Model 20 processors along with numerous peripherals (forming at least one complete system) located in Nuremberg, Germany were purchased on eBay in April/May 2019 for €3710 by two UK enthusiasts who, over the course of some months, moved the machine to Creslow Park in Buckinghamshire, United Kingdom. The system was in a small, abandoned building left untouched for decades, and apparently had been used in that building since all peripherals were still fully wired and interconnected. The systems are now in a dedicated machine room, and are undergoing restoration in preparation for public display in the future. A running list of remaining System/360s that are more than just 'front panels' can be found at World Inventory of remaining System/360 CPUs. Gallery This gallery shows the operator's console, with register value lamps, toggle switches (middle of pictures), and "emergency pull" switch (upper right of pictures) of the various models. See also History of IBM List of IBM products IBM System/4 Pi Gerrit Blaauw Bob O. Evans Notes References External links IBM System/360 System Summary 11th edition August 1969 IBM's announcement of the System/360 Dates of announcement, first ship and withdrawal of all models of the IBM System/360 Generations of the IBM 360/370/3090/390 by Lars Poulsen with multiple links and references Description of a large IBM System/360 model 75 installation at JPL "The Beginning of I.T. Civilization - IBM's System/360 Mainframe" by Mike Kahn Illustrations from “Introduction to IBM Data Processing Systems”, 1968: contains photographs of IBM System/360 computers and peripherals IBM System 360 RPG Debugging Template and Keypunch Card Video of a two-hour lecture and panel discussion entitled The IBM System/360 Revolution, from the Computer History Museum on 2004-04-07 Original vintage film from 1964 IBM System/360 Computer History Archives Project Several photos of a dual processor IBM 360/67 at the University of Michigan's academic Computing Center in the late 1960s or early 1970s are included in Dave Mills' article describing the Michigan Terminal System (MTS) Pictures of an IBM System/360 Model 67 at Newcastle (UK) University From the IBM Journal of Research and Development From IBM Systems Journal Computing platforms 1960s software Computer-related introductions in 1964 Instruction set architectures 32-bit computers

Operating System (OS)

Pintos Pintos is computer software, a simple instructional operating system framework for the x86 instruction set architecture. It supports kernel threads, loading and running user programs, and a file system, but it implements all of these in a very simple way. It was created at Stanford University by Ben Pfaff in 2004. It originated as a replacement for Not Another Completely Heuristic Operating System (Nachos), a similar system originally developed at UC Berkeley by Thomas E. Anderson, and was designed along similar lines. Like Nachos, Pintos is intended to introduce undergraduates to concepts in operating system design and implementation by requiring them to implement significant portions of a real operating system, including thread and memory management and file system access. Pintos also teaches students valuable debugging skills. Unlike Nachos, Pintos can run on actual x86 hardware, though it is often run atop an x86 emulator, such as Bochs or QEMU. Nachos, by contrast, runs as a user process on a host operating system, and targets the MIPS architecture (Nachos code must run atop a MIPS simulator). Pintos and its accompanying assignments are also written in the programming language C instead of C++ (used for original Nachos) or Java (used for Nachos 5.0j). Pintos is currently used by multiple institutions, including UC Berkeley and Imperial College London, as an academic aid in Operating Systems class curriculums. References External links Free software operating systems X86 operating systems Educational operating systems Software using the BSD license 2004 software

Operating System (OS)

Netrunner (operating system) Netrunner is a free operating system for desktop computers, laptops or netbooks, and arm-based device-types like the Odroid C1 microcomputer or the Pinebook. It comes in two versions: Netrunner and Netrunner Core, which are both based on Debian Stable. The Core versions features KDE Plasma plus a minimal selection of applications, multimedia codecs and some Firefox browser plugins. Overview Netrunner is only available as a 64-bit desktop operating system that uses the Calamares graphical installer. Since the August 20th 2019 release Netrunner is based on Debian Stable. Conceptualized for everyday use the desktop environment is based on Plasma Desktop by KDE targeting new users as well as users experienced with Linux. Netrunner is aimed at users who want an operating system to work "out-of-the-box", reducing the time to add other essential programs, multimedia codecs, firmware and other enhancements manually, post installation. Netrunner Core is a desktop version with a minimal amount of application. Core versions also feature both Pinebook and Odroid C1 ARM images. Default software Among the default software selection of Netrunner Desktop are many applications such as: KDE Plasma Desktop Mozilla Firefox (including Plasma integration) Mozilla Thunderbird (including Plasma integration) VLC media player LibreOffice GIMP Krita Gwenview Kdenlive Inkscape Samba Mounter (easy NAS setup) Steam VirtualBox Release history The following is the release history for Netrunner Core and Desktop: The following is the release history for previously Kubuntu based Netrunner versions (discontinued): The following is the release history for the Netrunner Rolling, which has been discontinued in favor of Manjaro collaboration efforts: Reception Jack M Germain reviewed Netrunner 19.01. Hectic Geek reviewed Netrunner 14. LinuxInsider wrote a post. Its review of Netrunner 13: Jesse Smith from DistroWatch Weekly wrote review of Netrunner 4.2: Dedoimedo reviewed Netrunner 4.2 "Dryland" with following words: References External links 2010 software KDE

Operating System (OS)

Real-Time Multiprogramming Operating System Real-Time Multiprogramming Operating System (RTMOS) was a 24-bit process control operating system developed in the 1960s by General Electric that supported both real-time computing and multiprogramming. Programming was done in assembly language or Process FORTRAN. The two languages could be used in the same program, allowing programmers to alternate between the two as desired. Multiprogramming operating systems are now considered obsolete, having been replaced by multitasking. References General Electric Real-time operating systems

Operating System (OS)

Environmental subsystem Environmental subsystems are central components of operating systems of the Windows NT type. They allow the operating system to run software developed for the platform in question. For example, Windows NT 4.0 has four environmental subsystems, viz Win32, DOS or Win16, OS/2, and POSIX, the latter of which is a Unix standard. The latter resides primarily in the Dynamic Link Library posix.dll. The environmental subsystems are one part of the strategy Microsoft developed for making the Windows NT stream of operating systems a hub for multi-platform computing Others include four Hardware Abstraction layers, one for Intel processors, three for RISC processors (DEC Alpha, PowerPC, Mips), and a driver for the HPFS, the standard for OS/2. Since Windows 2000, the FAT32 file system first introduced with Windows 95 has also been present, with HPFS deprecated then being omitted in later systems. A third-party driver for FAT32 can be used on the earlier NT operating systems. Therefore, Windows NT as of version 4.0 had a default of four file systems (NTFS, HPFS, FAT12, and FAT16), and installations of the system with a driver allowing access to a fifth FAT32) are very common, and tools allowing access to Unix file systems are also in existence. Interoperability with Novell Netware is generally implemented at the applications and systems programming level rather than at the kernel and data link layer and therefore further from the physical hardware. References Windows NT architecture

Operating System (OS)

System requirements To be used efficiently, all computer software needs certain hardware components or other software resources to be present on a computer. These prerequisites are known as (computer) system requirements and are often used as a guideline as opposed to an absolute rule. Most software defines two sets of system requirements: minimum and recommended. With increasing demand for higher processing power and resources in newer versions of software, system requirements tend to increase over time. Industry analysts suggest that this trend plays a bigger part in driving upgrades to existing computer systems than technological advancements. A second meaning of the term of system requirements, is a generalisation of this first definition, giving the requirements to be met in the design of a system or sub-system. Recommended system requirements Often manufacturers of games will provide the consumer with a set of requirements that are different from those that are needed to run a software. These requirements are usually called the recommended requirements. These requirements are almost always of a significantly higher level than the minimum requirements, and represent the ideal situation in which to run the software. Generally speaking, this is a better guideline than minimum system requirements in order to have a fully usable and enjoyable experience with that software. Hardware requirements The most common set of requirements defined by any operating system or software application is the physical computer resources, also known as hardware, A hardware requirements list is often accompanied by a hardware compatibility list (HCL), especially in case of operating systems. An HCL lists tested, compatible, and sometimes incompatible hardware devices for a particular operating system or application. The following sub-sections discuss the various aspects of hardware requirements. Architecture All computer operating systems are designed for a particular computer architecture. Most software applications are limited to particular operating systems running on particular architectures. Although architecture-independent operating systems and applications exist, most need to be recompiled to run on a new architecture. See also a list of common operating systems and their supporting architectures. Processing power The power of the central processing unit (CPU) is a fundamental system requirement for any software. Most software running on x86 architecture define processing power as the model and the clock speed of the CPU. Many other features of a CPU that influence its speed and power, like bus speed, cache, and MIPS are often ignored. This definition of power is often erroneous, as AMD Athlon and Intel Pentium CPUs at similar clock speed often have different throughput speeds. Intel Pentium CPUs have enjoyed a considerable degree of popularity, and are often mentioned in this category. Memory All software, when run, resides in the random access memory (RAM) of a computer. Memory requirements are defined after considering demands of the application, operating system, supporting software and files, and other running processes. Optimal performance of other unrelated software running on a multi-tasking computer system is also considered when defining this requirement. Secondary storage Data storage device requirements vary, depending on the size of software installation, temporary files created and maintained while installing or running the software, and possible use of swap space (if RAM is insufficient). Display adapter Software requiring a better than average computer graphics display, like graphics editors and high-end games, often define high-end display adapters in the system requirements. Peripherals Some software applications need to make extensive and/or special use of some peripherals, demanding the higher performance or functionality of such peripherals. Such peripherals include CD-ROM drives, keyboards, pointing devices, network devices, etc. Software requirements Software requirements deal with defining software resource requirements and prerequisites that need to be installed on a computer to provide optimal functioning of an application. These requirements or prerequisites are generally not included in the software installation package and need to be installed separately before the software is installed. Platform A computing platform describes some sort of framework, either in hardware or software, which allows software to run. Typical platforms include a computer's architecture, operating system, or programming languages and their runtime libraries. Operating system is one of the requirements mentioned when defining system requirements (software). Software may not be compatible with different versions of same line of operating systems, although some measure of backward compatibility is often maintained. For example, most software designed for Microsoft Windows XP does not run on Microsoft Windows 98, although the converse is not always true. Similarly, software designed using newer features of Linux Kernel v2.6 generally does not run or compile properly (or at all) on Linux distributions using Kernel v2.2 or v2.4. APIs and drivers Software making extensive use of special hardware devices, like high-end display adapters, needs special API or newer device drivers. A good example is DirectX, which is a collection of APIs for handling tasks related to multimedia, especially game programming, on Microsoft platforms. Web browser Most web applications and software depend heavily on web technologies to make use of the default browser installed on the system. Microsoft Internet Explorer is a frequent choice of software running on Microsoft Windows, which makes use of ActiveX controls, despite their vulnerabilities. Other requirements Some software also has other requirements for proper performance. Internet connection (type and speed) and resolution of the display screen are notable examples. Examples Following are a few examples of system requirement definitions for popular PC games and trend of ever-increasing resource needs: For instance, while StarCraft (1998) requires: Doom 3 (2004) requires: Star Wars: The Force Unleashed (2009) requires: Grand Theft Auto V (2015) requires: See also Requirement Requirements analysis Software Requirements Specification Specification (technical standard) System requirements specification (SyRS) References Software requirements

Operating System (OS)

OS X Lion Mac OS X Lion, also known as OS X Lion, (version 10.7) is the eighth major release of macOS, Apple's desktop and server operating system for Macintosh computers. A preview of Mac OS X 10.7 Lion was publicly shown at the "Back to the Mac" Apple Special Event on October 20, 2010. It brought many developments made in Apple's iOS, such as an easily navigable display of installed applications, to the Mac, and includes support for the Mac App Store, as introduced in Mac OS X 10.6 Snow Leopard version 10.6.6. On February 24, 2011, the first developer's preview of Lion (11A390) was released to subscribers to the Apple Developer program. Other developer previews were subsequently released, with Lion Preview 4 (11A480b) being released at WWDC 2011. Lion was released to manufacturing on July 1, 2011, followed by its final release via the Mac App Store on July 20, 2011. Apple reported over one million Lion sales on the first day of its release. , Mac OS X Lion had sold over six million copies worldwide. Lion is the final release whose development was overseen by Bertrand Serlet, considered the "founding father of Mac OS X". Although originally paid, Apple later allowed free downloads of the OS, especially for customers of older and no longer officially supported Macintosh computers, starting on June 30, 2021. The same practice was also applied to its successor, OS X Mountain Lion. Release and distribution On June 6, 2011, at the Apple Worldwide Developers Conference, it was announced that the official release for Lion would be in July 2011. The specific release date of July 20 was not confirmed until the day before, July 19, by Apple CFO, Peter Oppenheimer, as part of Apple's 2011 third-quarter earnings announcement. Apple did not initially announce any physical media distribution for Lion, such as a set of CD-ROMs or a DVD-ROM as used for past releases. Instead, the operating system was said to be available exclusively as a download from the Mac App Store for US$29.99. The only prior version of OS X that supports the Mac App Store is Snow Leopard, which implied that any machines that support Lion currently running Tiger or Leopard would first have to be upgraded to Snow Leopard, as opposed to allowing a direct upgrade to Lion. Apple later announced two alternative distribution mechanisms for the benefit of users without broadband Internet access: in-store downloads at retail Apple Stores, and a USB flash drive containing the OS, priced at US$69, available through the online Apple Store beginning in August. On August 4, 2011, Apple started to take orders for Mac OS X Lion's USB installation flash drives for $69.99. The Server portion of Lion is available as a separate download from the Mac App Store for US$49.99, which is in addition to the purchase price of Lion itself. In July 2012, Lion was removed from the Mac App Store and retail Apple stores following the release of OS X Mountain Lion. Following the removal of Lion from the Mac App Store, customers could still purchase Lion by phone at the reduced price of $20. In October 2013, Lion was returned to the Apple Store website concurrently with Mountain Lion following the release of OS X Mavericks for the convenience of users who cannot run Mavericks on older Mac models. Hardware support The first developer preview of Lion added TRIM support for Solid-state drives (SSD) shipped with Macs, which is also included in the latest version of Snow Leopard (10.6.8) shipping with MacBook Pros before July 20, 2011. Other SSDs have built-in TRIM-like optimization, while yet others require OS patching. System requirements x86-64 CPU (64-bit Macs, with an Intel Core 2 Duo, Intel Core i5, Intel Core i7, or Xeon processor.) At least 2 GB of memory Mac OS X 10.6.6 or later (Mac OS X 10.6.8 is recommended) 7 GB of available space AirDrop is supported on the following Mac models: MacBook Pro (late 2008 or newer), MacBook Air (late 2010 or newer), MacBook (late 2008 or newer), iMac (early 2009 or newer), Mac Mini (mid-2010 or newer), Mac Pro (early 2009 with AirPort Extreme card and mid-2010 or newer). New or changed features Some new features were announced at the "Back to the Mac" keynote in October 2010, and the Apple website was updated in February 2011, with more details. Other features were announced at the WWDC 2011 keynote or on Apple's Mac OS X Lion Web site after the keynote. Apple states that there are over 250 new or changed features in Lion, including: Address Book uses an iPad-like user interface. It also includes improved Yahoo support and FaceTime calling. AirDrop – Lion-to-Lion direct file sharing via Wi-Fi Direct, with no wireless access point required. Address space layout randomization – Address space layout randomization (ASLR), a security technique that puts important data in unpredictable locations, making it harder to target known weaknesses, is available for 32-bit applications, and "has been improved for all applications", in Lion. Apple Push Notification Service – Send over-the-air alerts, such as news updates or social networking status changes, using Apple's Push Notification service to applications that support APNS. APNS allows Mac OS X Lion and iOS clients to receive push changes to items such as mail, calendar and contacts from a configured OS X Lion Server. Auto-correction behaves much like on iOS devices, displaying an iOS-like popup box. Auto Save – As in iOS, documents in applications written to use Auto Save are saved automatically so users do not have to worry about manually managing their documents. The Auto Save feature significantly alters traditional workflow patterns and is a controversial addition to the system. Emoji support – Apple has added a new Emoji font commonly used in chat to express ideograms. Exposé in the Dock, a way of activating Exposé for a single application from the Dock, a feature added in Mac OS X 10.6, is altered. One must double-tap with two fingers on a dock icon to initiate single-application Exposé, or simply right-click or control-click and select Show All Windows. FaceTime comes bundled with Lion. FileVault offers full disk encryption and added security with XTS-AES 128 data encryption. Support for FileVault on external hard drives has also been added. Finder improvements – Finder search allows multiple search criteria to be specified without creating a smart folder, Finder search offers suggestions, files can be grouped by various attributes, and one can merge files under two folders with the same name – a prompt appears asking to replace or keep both files. The navigation sidebar lost the ability to show the specific icon of a map or volume (by default; there is a hack to still add the old ability), instead it shows a grey standard map icon. Font Book 3 – Font Book 3 provides more flexible displays of character glyphs supplied by a particular font face. Duplicate font files are flagged with a warning icon, and can be fixed automatically or resolved manually. Full-screen apps – Native, system-wide support for full-screen applications running in their own space. Supporting applications display a new button at the top right of application window, this button opens applications in full-screen mode. However, full screen mode is not supported for dual screen setups. High-quality multilingual speech voices – users can download new high-quality voices in more than forty languages and dialects. iCal has an updated user interface, an annual view, and support for a full-screen view. iChat has support for logging into Yahoo! Messenger. Users can audio- and video-chat with other iChat users using their Yahoo! accounts. Languages/Localization – Arabic, Czech, Turkish and Hungarian are added as full system languages, to make the total number of twenty-two languages available in Mac OS X. Launchpad – An application launcher that displays an iOS-like icon grid of installed applications. It features the ability to make multiple pages and group apps into folders that function the same as folders in iOS. Mac App Store – An application store built in the image of the iOS App Store. Like in iOS, it provides ways for shoppers to discover apps, one-click installation of apps, and one-click updates of all or selected installed applications. Despite being announced as a future feature of Lion, the Mac App Store was released for Mac OS X 10.6 Snow Leopard on January 6, 2011, as it was bundled with the Mac OS X 10.6.6 update. Mail 5 – Uses an iPad-like user interface, has a fullscreen-optimized view, uses chronological "Conversations" to organize messages, and supports Exchange 2010 (but not through the Exchange ActiveSync protocol, as iOS). Mission Control replaces the "All windows" Exposé feature. It gives an overview of all running applications just like "All windows" but groups windows from the same application. At the top of the screen it gives quick access to the Dashboard, Spaces, and running full-screen applications. Multi-touch gestures – Similar to iOS, additional gestures performed using a multi-touch input device (e.g. Magic Mouse, Magic Trackpad) allow the user to scroll, swipe to different pages, and enter Mission Control. While this is not the first official multi-touch support for Mac OS X, it has been expanded; other frameworks, such as Lux, have already created multi-touch support. Multi-User Screen Sharing – The built-in Screen Sharing feature allows remote users to log into a separate user account from the one that is currently logged in. While one user is logged into a machine, a second user can log into the same machine remotely, seeing their own desktop and user environment. Preview gains several features, including full-screen support and the ability to sign a document just by holding a signed piece of paper up to the camera. Profile Manager provides several features, including push notification-based management of OS X Lion and above. QuickTime reincorporates some features from QuickTime Pro. New features cited include Copy/Paste, Insert Clip, Crop Video, Rotate Video, Resize, Trim, and more Export options. Recovery Partition – Apple has introduced a recovery partition that includes utilities generally found on the OS X discs. This partition permits the user to restore their computer to its original factory state. If the partition were to become damaged or otherwise not available, such as with a new drive, a new copy of OS X Lion can be installed over the internet. Resume – Applications resume in the same state when re-opened as already seen in iOS. Safari – With full-screen mode and the new WebKit2 layout engine. System Information – This feature is a re-design of System Profiler, which has been completely altered with new views which display graphical information on displays, storage devices, memory usage along with other hardware information. The previous layout remains available by clicking "System Report". Early builds of Lion also used System Information as a replacement for "About This Mac", although the final release reinstated the version of this dialog box found in Snow Leopard. Terminal has extra features, including full screen mode. TextEdit gains a new graphical toolbar with font selection and text highlighting. The new TextEdit also supports Apple's new automatic file saving and versions technologies. Versions – Time Machine-like saving and browsing of past versions of documents for applications written to use Versions. Vertical text – Lion supports vertical layouts for East Asian languages. The complete list was on Apple's website but has since been taken down; it can now be found on the Internet Archive. The developer release notes may also be of interest. Server features Wiki Server 3 – Making it easier to collaborate, share, and exchange information. Users can quickly switch between a server's home page, My Page, Updates, Wikis, People, and Podcasts. File sharing is simpler, and a new Page Editor is added for easy customization. WebDAV File Sharing – Lion Server delivers wireless file sharing for clients that support WebDAV. Enabling WebDAV in Lion Server gives iOS users the ability to access, copy, and share documents on the server from applications such as Keynote, Numbers, and Pages. Profile Manager – Profile Manager delivers simple, profile-based setup and management for Mac OS X Lion, iPhone, iPad, and iPod touch devices. It also integrates with existing directory services and delivers automatic over-the-air profile updates using the Apple Push Notification service. User interface changes Redesigned Aqua user interface elements, including buttons and progress bars. The red, yellow, and green buttons in the window decorations have also been made smaller, with a slightly changed design. Flexible window resizing from any corner or edge of the window, similar to window resizing in Microsoft Windows and many window managers for X11. The metal finish has also been slightly altered. It is a lighter shade of grey and features a speckled texture. Scrollbar arrows have been removed. Scrolling is reversed by default, to act more like a touch screen device, so that content moves in the direction of finger movement on touch-pad or mouse (with the scrollbar moving in the opposite direction), rather than the scrollbar moving in the direction of finger movement (with the content moving in the opposite direction). Also, like in iOS, scrolling "bounces" when the scroll bar hits the top or bottom of the window. When resizing a window by clicking on the green button (left-top), a transform effect animates the enlargement. New windows fly to the front (like opening an app in iOS). The dashboard is its own space in Mission Control, rather than in previous versions of OS X where the widgets simply flew in and the background dimmed. The "ripple effect" that was seen previously when adding widgets is no longer there due to this change. Users have the option to return to the old dashboard configuration in System Preferences. Tabs, when selected, have a recessed and darkened appearance as opposed to previous versions where selected tabs were highlighted in aqua blue. Dropped features Save As – replaced by Duplicate and Revert functions due to the introduction of Auto Save and Versions (only applies to applications modified to support Auto Save, such as TextEdit; applications not modified to support Auto Save, such as Microsoft Word, retain this functionality). Front Row, a media center application. The application has been copied into Lion by third-party users, however its incompatibility with iTunes 10.4 renders some features useless. Rosetta, software that makes possible the execution of PowerPC software on x86 hardware, is no longer available. This disables some programs that ran on previous versions of Mac OS X. Programs requiring Rosetta to operate are not allowed to be distributed via the Mac App Store. Adobe Flash Player and Apple's Java Runtime Environment (JRE) are not included in new installations of Lion, but both can still be downloaded and installed manually. Apple is no longer actively maintaining its JRE, but Software Update offers to download Snow Leopard's JRE when a user tries to run a Java program and the JRE is not installed. Programs using Java are not allowed to be distributed via the Mac App Store. iSync, software used for syncing contacts and calendars to third-party mobile phones, is no longer included; however, iSync v3.1.2 from Snow Leopard continues to work. Remote Install Mac OS X, software that allows OS X to be installed using the Remote Disk feature. Using Target Disk Mode, users can circumvent this omission. This is replaced by the Recovery Partition, which does exactly the same thing but without needing an external disk, as long as the hard disk is not damaged. Apple USB Modem is not compatible with Lion. QuickTime Streaming Server, software used to deliver video and audio on request to users over a computer network, including the Internet. WPA Enterprise configuration for wireless networks was replaced by the requirement to obtain a configuration profile. The Post-Install Welcome Video was removed. Reception Reception for OS X Lion has been mixed; complaints include a substantial backlash by "Pro" users with workflows affected by the Autosave/Revert workflow. Other highly criticized decisions include the change to "natural scrolling", hiding of the scroll bar, the omission of the iSync program necessary to synchronize a Mac with non-Apple mobile devices, as well as abandoned functionality in Exposé and Spaces. However, in an extensive review of the operating system, Ars Technica recommended Lion. They noted that it feels like it is the start of a new line of operating systems that will continue to be influenced by Apple's iOS platform. The review also compared the introduction of Lion, along with its new conventions that change traditional ways of computing, with the original Mac OS X and when it replaced the classic Mac OS. Macworld called Lion a "radical revision", praising the changes made to the operating system to be more user friendly to new Mac users who are familiar with the iOS interface, while criticizing the limited utility of the interface. Ultimately, the magazine considered Lion an operating system worth getting, giving it 4.5 out of 5 stars. guardian.co.uk called Lion a substantial improvement from its predecessors and considered it a "steal" given its price. On the other hand, Gizmodo stated that the new interface "feels like a failure" and concluded by saying that "it doesn't feel like a must-have upgrade". Ted Landau of MacObserver also had serious criticism of Lion, reversing his earlier praise of Autosave and writing, "Auto Save takes irritatingly long when working with large documents. Still others lament the loss of the Save As… command, noting that the new Duplicate option is not as convenient to use. The consensus is that none of this would matter much — if you could disable Auto Save. If you like how it works, leave things as is. Otherwise, get rid of it. But Lion offers no way to turn Auto Save off. This is the heart of the "my way or the highway" complaint. A posting sums it up: "The new features are intrusive, non-respectful of the users' choices, and cannot be changed." Due to Lion's enhanced security features, including application sandboxing, Dino Dai Zovi, principal of security consultancy Trail of Bits and the coauthor (with Charles Miller) of The Mac Hacker's Handbook, characterized Lion's security as "a significant improvement, and the best way that I've described the level of security in Lion is that it's Windows 7, plus, plus. I generally tell Mac users that if they care about security, they should upgrade to Lion sooner rather than later, and the same goes for Windows users, too." Software incompatibilities Applications depending on Rosetta, such as Office for Mac 2004, AppleWorks, and early versions of Quicken for Mac 2007, are no longer supported. This affects applications listed as Classic or PowerPC in System Profiler. Unix package managers for Mac OS X such as Fink and MacPorts require reinstalling and then running Xcode. Release history References External links 7 X86-64 operating systems 2011 software Computer-related introductions in 2011

Operating System (OS)

DragonFly BSD DragonFly BSD is a free and open-source Unix-like operating system forked from FreeBSD 4.8. Matthew Dillon, an Amiga developer in the late 1980s and early 1990s and FreeBSD developer between 1994 and 2003, began working on DragonFly BSD in June 2003 and announced it on the FreeBSD mailing lists on 16 July 2003. Dillon started DragonFly in the belief that the techniques adopted for threading and symmetric multiprocessing in FreeBSD 5 would lead to poor performance and maintenance problems. He sought to correct these anticipated problems within the FreeBSD project. Due to conflicts with other FreeBSD developers over the implementation of his ideas, his ability to directly change the codebase was eventually revoked. Despite this, the DragonFly BSD and FreeBSD projects still work together, sharing bug fixes, driver updates, and other improvements. Intended as the logical continuation of the FreeBSD 4.x series, DragonFly has diverged significantly from FreeBSD, implementing lightweight kernel threads (LWKT), an in-kernel message passing system, and the HAMMER file system. Many design concepts were influenced by AmigaOS. System design Kernel The kernel messaging subsystem being developed is similar to those found in microkernels such as Mach, though it is less complex by design. However, DragonFly uses a monolithic kernel system. DragonFly's messaging subsystem has the ability to act in either a synchronous or asynchronous fashion, and attempts to use this capability to achieve the best performance possible in any given situation. According to developer Matthew Dillon, progress is being made to provide both device input/output (I/O) and virtual file system (VFS) messaging capabilities that will enable the remainder of the project goals to be met. The new infrastructure will allow many parts of the kernel to be migrated out into userspace; here they will be more easily debugged as they will be smaller, isolated programs, instead of being small parts entwined in a larger chunk of code. Additionally, the migration of select kernel code into userspace has the benefit of making the system more robust; if a userspace driver crashes, it will not crash the kernel. System calls are being split into userland and kernel versions and being encapsulated into messages. This will help reduce the size and complexity of the kernel by moving variants of standard system calls into a userland compatibility layer, and help maintain forwards and backwards compatibility between DragonFly versions. Linux and other Unix-like OS compatibility code is being migrated out similarly. Threading As support for multiple instruction set architectures complicates symmetric multiprocessing (SMP) support, DragonFly BSD now limits its support to the x86-64 platform. DragonFly originally ran on the x86 architecture, however as of version 4.0 it is no longer supported. Since version 1.10, DragonFly supports 1:1 userland threading (one kernel thread per userland thread), which is regarded as a relatively simple solution that is also easy to maintain. Inherited from FreeBSD, DragonFly also supports multi-threading. In DragonFly, each CPU has its own thread scheduler. Upon creation, threads are assigned to processors and are never preemptively switched from one processor to another; they are only migrated by the passing of an inter-processor interrupt (IPI) message between the CPUs involved. Inter-processor thread scheduling is also accomplished by sending asynchronous IPI messages. One advantage to this clean compartmentalization of the threading subsystem is that the processors' on-board caches in symmetric multiprocessor systems do not contain duplicated data, allowing for higher performance by giving each processor in the system the ability to use its own cache to store different things to work on. The LWKT subsystem is being employed to partition work among multiple kernel threads (for example in the networking code there is one thread per protocol per processor), reducing competition by removing the need to share certain resources among various kernel tasks. Shared resources protection In order to run safely on multiprocessor machines, access to shared resources (like files, data structures) must be serialized so that threads or processes do not attempt to modify the same resource at the same time. In order to prevent multiple threads from accessing or modifying a shared resource simultaneously, DragonFly employs critical sections, and serializing tokens to prevent concurrent access. While both Linux and FreeBSD 5 employ fine-grained mutex models to achieve higher performance on multiprocessor systems, DragonFly does not. Until recently, DragonFly also employed spls, but these were replaced with critical sections. Much of the system's core, including the LWKT subsystem, the IPI messaging subsystem and the new kernel memory allocator, are lockless, meaning that they work without using mutexes, with each process operating on a single CPU. Critical sections are used to protect against local interrupts, individually for each CPU, guaranteeing that a thread currently being executed will not be preempted. Serializing tokens are used to prevent concurrent accesses from other CPUs and may be held simultaneously by multiple threads, ensuring that only one of those threads is running at any given time. Blocked or sleeping threads therefore do not prevent other threads from accessing the shared resource unlike a thread that is holding a mutex. Among other things, the use of serializing tokens prevents many of the situations that could result in deadlocks and priority inversions when using mutexes, as well as greatly simplifying the design and implementation of a many-step procedure that would require a resource to be shared among multiple threads. The serializing token code is evolving into something quite similar to the "Read-copy-update" feature now available in Linux. Unlike Linux's current RCU implementation, DragonFly's is being implemented such that only processors competing for the same token are affected rather than all processors in the computer. DragonFly switched to multiprocessor safe slab allocator, which requires neither mutexes nor blocking operations for memory assignment tasks. It was eventually ported into standard C library in the userland, where it replaced FreeBSD's malloc implementation. Virtual kernel Since release 1.8 DragonFly has a virtualization mechanism similar to User-mode Linux, allowing a user to run another kernel in the userland. The virtual kernel (vkernel) is run in completely isolated environment with emulated network and storage interfaces, thus simplifying testing kernel subsystems and clustering features. The vkernel has two important differences from the real kernel: it lacks many routines for dealing with the low-level hardware management and it uses C standard library (libc) functions in place of in-kernel implementations wherever possible. As both real and virtual kernel are compiled from the same code base, this effectively means that platform-dependent routines and re-implementations of libc functions are clearly separated in a source tree. The vkernel runs on top of hardware abstractions provided by the real kernel. These include the kqueue-based timer, the console (mapped to the virtual terminal where vkernel is executed), the disk image and virtual kernel Ethernet device (VKE), tunneling all packets to the host's tap interface. Package management Third-party software is available on DragonFly as binary packages via pkgng or from a native ports collection – DPorts. DragonFly originally used the FreeBSD Ports collection as its official package management system, but starting with the 1.4 release switched to NetBSD's pkgsrc system, which was perceived as a way of lessening the amount of work needed for third-party software availability. Eventually, maintaining compatibility with pkgsrc proved to require more effort than was initially anticipated, so the project created DPorts, an overlay on top of the FreeBSD Ports collection. CARP support The initial implementation of Common Address Redundancy Protocol (commonly referred to as CARP) was finished in March 2007. As of 2011, CARP support is integrated into DragonFly BSD. HAMMER file systems Alongside the Unix File System, which is typically the default file system on BSDs, DragonFly BSD supports the HAMMER and HAMMER2 file systems. HAMMER2 is the default file system as of version 5.2.0. HAMMER was developed specifically for DragonFly BSD to provide a feature-rich yet better designed analogue of the increasingly popular ZFS. HAMMER supports configurable file system history, snapshots, checksumming, data deduplication and other features typical for file systems of its kind. HAMMER2, the successor of the HAMMER file system, is now considered stable, used by default, and the focus of further development. Plans for its development were initially shared in 2012. In 2017, Dillon announced that the next DragonFly BSD version (5.0.0) would include a usable, though still experimental, version of HAMMER2, and described features of the design. With the release after 5.0.0, version 5.2.0, HAMMER2 became the new default file system. devfs In 2007 DragonFly BSD received a new device file system (devfs), which dynamically adds and removes device nodes, allows accessing devices by connection paths, recognises drives by serial numbers and removes the need for pre-populated /dev file system hierarchy. It was implemented as a Google Summer of Code 2009 project. Application snapshots DragonFly BSD supports Amiga-style resident applications feature: it takes a snapshot of a large, dynamically linked program's virtual memory space after loading, allowing future instances of the program to start much more quickly than it otherwise would have. This replaces the prelinking capability that was being worked on earlier in the project's history, as the resident support is much more efficient. Large programs like those found in KDE Software Compilation with many shared libraries will benefit the most from this support. Development and distribution As with FreeBSD and OpenBSD, the developers of DragonFly BSD are slowly replacing pre-function prototype-style C code with more modern, ANSI equivalents. Similar to other operating systems, DragonFly's version of the GNU Compiler Collection has an enhancement called the Stack-Smashing Protector (ProPolice) enabled by default, providing some additional protection against buffer overflow based attacks. , the kernel is no longer built with this protection by default. Being a derivative of FreeBSD, DragonFly has inherited an easy-to-use integrated build system that can rebuild the entire base system from source with only a few commands. The DragonFly developers use the Git version control system to manage changes to the DragonFly source code. Unlike its parent FreeBSD, DragonFly has both stable and unstable releases in a single source tree, due to a smaller developer base. Like the other BSD kernels (and those of most modern operating systems), DragonFly employs a built-in kernel debugger to help the developers find kernel bugs. Furthermore, , a debug kernel, which makes bug reports more useful for tracking down kernel-related problems, is installed by default, at the expense of a relatively small quantity of disk space. When a new kernel is installed, the backup copy of the previous kernel and its modules are stripped of their debugging symbols to further minimize disk space usage. Distribution media The operating system is distributed as a Live CD and Live USB (full X11 flavour available) that boots into a complete DragonFly system. It includes the base system and a complete set of manual pages, and may include source code and useful packages in future versions. The advantage of this is that with a single CD users can install the software onto a computer, use a full set of tools to repair a damaged installation, or demonstrate the capabilities of the system without installing it. Daily snapshots are available from the master site for those who want to install the most recent versions of DragonFly without building from source. Like the other free and open-source BSDs, DragonFly is distributed under the terms of the modern version of the BSD license. Release history See also Comparison of BSD operating systems Comparison of open-source operating systems Comparison of operating system kernels References External links 2004 software Berkeley Software Distribution Free software operating systems Operating system distributions bootable from read-only media Software forks Software using the BSD license Unix variants X86 operating systems

Operating System (OS)

RISC iX RISC iX is a discontinued Unix operating system designed to run on a series of workstations based on the Acorn Archimedes microcomputer. Heavily based on 4.3BSD, it was initially completed in 1988, a year after Arthur but before RISC OS. It was introduced in the ARM2-based R140 workstation in 1989, followed up by the ARM3-based R200-series workstations in 1990. Features X11 (initially Release 2) with Ardent Window Manager, Tab Window Manager and Ultrix Window Manager available by default, plus X.desktop from IXI Limited System V virtual memory extensions, compatible with the "System V Interface Definition" C Compiler with ANSI C and Portable C Compiler (pcc) (Berkeley) compatibility Sun Microsystems Network File System version 3.2 ARM assembly language Although Acorn had licensed Sun Microsystems' NeWS in 1987, broad industry adoption of the X Window System, including Sun's belated endorsement, resulted in X11 technologies featuring in RISC iX. RISC iX 1.2 upgraded the X11 server to release 4, and was certified to conform to the X/Open Portability Guide 3 Base profile. Peculiarly, the system console featured a two-cursor text copying mechanism inspired by Acorn's own earlier 8-bit range including the BBC Micro. Architecture-related features The system implemented transparent demand paging of compressed executable programs, allowing the constituent pages of these compressed executables to be loaded into memory by the existing demand paging mechanism and then expanded in place for execution, taking advantage of the availability of sparse files (files with zero-padded regions) to reduce the disc space occupied by these pages. Shared library support, enabling processes to share library code, was also introduced to work around other "unpleasant" consequences of the hardware's 32 KB page size, one of these being the excess space occupied by processes residing in main memory, especially in situations where separate pages need to be allocated. Despite these remedies, the workstations offering RISC iX were regarded as being hampered by the memory management unit (MMU) using 32 KB pages. The hardware supporting RISC iX also did not have direct memory access capabilities for disk operations, meaning that the CPU would spend time servicing interrupts related to disk transfers resulting in "a definite reduction in, but not a complete loss of, available CPU power during disc transfers". However, by reducing the amount of data being fetched, the executable decompression technique did reduce CPU involvement in performing disc transfers, albeit at the expense of incurring CPU usage in the decompression of retrieved pages. Positive outcomes of the decompression scheme also included reduced loading on storage devices, of importance for networked storage, and generally improved disc transfer performance. Distribution RISC iX was either supplied preinstalled on new computer hardware or was installed onsite from a portable tape drive by Granada Microcare, who would take the installation tape away with them. Upgrades to RISC iX 1.2 from earlier versions started at £349 for R140 machines, and new installations for A400-series machines started at £999. Installations required 100 MB of space on suitable hard drive or network storage, with hard drive and SCSI card bundles being offered from £1699 for R140 machines and from £2326 for A400-series machines. Once installed a backup of the core operating system to three floppy disks was possible, allowing future reinstallation through the use of remote filesystems or backup media to transfer files to a machine. Supported hardware According to documentation concerning RISC iX 1.2 availability, the operating system could be used on the R140, R225 and R260, being pre-installed on the R260, accessible via a fileserver (such as an R260) on the R225, and as an upgrade from RISC iX 1.15 or earlier on the R140. The A540, being practically identical to the R260, could support RISC iX as delivered, whereas A400-series machines required an Acorn SCSI card, with older A400-series machines also needing a memory controller upgrade and "all the appropriate field change orders" to have been performed. A300-series and the A3000 machines were not supported. RISC iX is not compatible with later Archimedes machines. Machines Several machines were designed specifically to run RISC iX. M4 An unreleased machine, built internally by Acorn for the development of RISC iX. Reputedly only three were built and one of them has subsequently been destroyed. All known examples are owned by The National Museum of Computing. A680 Technical Publishing System Prototyped but unreleased, the A680 contained an ARM2 processor, 8 MB RAM, a 70 MB hard drive running from an onboard SCSI controller, and either a 40 MB cartridge tape drive or a single 2 MB floppy drive. Up to four "podule" expansion cards could be fitted, although one slot was occupied by the laser beam printer (LBP) expansion card supporting a directly-driven low-cost laser printer as an alternative to a PostScript printer connected via the serial port. The system was meant to run Frame Technology's FrameMaker under the "Acorn UNIX" operating system. To support 8 MB of RAM, dual memory controller (MEMC) units were employed. No other machine from Acorn Computers included integrated SCSI. However, it is rumoured that overheating from the SCSI controller was one reason for the machine to never be released. R140 Based on the A440/1, the R140 uses the same 8 MHz ARM2 processor and 4 MB RAM, also providing a 60 MB ST506 hard drive, with the option of adding a second hard drive using the same internal controller. A SCSI adaptor was available (priced at £299 plus VAT) for other storage peripherals. Since the hardware is based on the Archimedes series, Acorn's podule expansions could be added, although appropriate drivers would have needed to be written. At the time of initial release in 1989, the cost of the R140 was £3,500 for a standalone workstation without Ethernet connectivity. For the additional cost of the Ethernet expansion (£449 plus VAT), a network-capable workstation could be configured. A floating point expansion card based on the WE32206 could also be added (priced at £599 plus VAT). A discount introduced at the start of 1990 offered the R140 bundled with Ethernet expansion and either a 14-inch colour monitor with PC emulation software or a 19-inch monochrome monitor for £2999 plus VAT. Supplied with RISC OS 2 in ROM, the machine would boot that OS then could either automatically boot RISC iX totally removing RISC OS from memory or continue running RISC OSoptionally being rebooted into RISC iX at any time. An ordinary A440/1 with at least 4 MB RAM and a suitable hard drive could also run RISC iX. R260 Based on the A540, the R260 originally contained a 26 MHz, (later 33 MHz) ARM3 processor, 8 MB RAM (upgradable to 16 MB) SCSI adapter and a 100 MB or 120 MB SCSI hard drive (typically a Conner CP30100). It booted in the same style as the earlier R140, but was normally configured for customers to boot straight into RISC iX. The machine was supplied with an Ethernet adapter. The system was released in 1990 priced at £3995 plus VAT, having been announced with a price of £5000 plus VAT. A floating point accelerator or "arithmetic co-processor", the FPA10, was made available in 1993 for the R260, as well as for the A540 and A5000 machines, priced at £99 plus VAT. These machines were designed to support the FPA device via a dedicated socket on the processor card (or, in the case of the A5000, on the motherboard), and offered a peak throughput of 5 MFLOPS at 26 MHz. A similarly configured A540 could run RISC iX. Production of the A540 and R260 was discontinued in mid-1993. R225 The R225 was a diskless version of the R260. It required a network file server or an R260 to boot. The system was released alongside the R260 priced at £1995 plus VAT, having been announced with a price of £3000 plus VAT. Peripherals As well as industry-standard Ethernet, Acorn's own Econet was supported, facilitating connectivity between Econet and IP-based Ethernet networks. Moreover, the Econet interface on a RISC iX workstation could be treated as a "Unix networking" interface, permitting TCP/IP requests to be sent over Econet to hosts capable of handling them. In 1991, with Ethernet becoming more widespread on campus networks, Acorn offered a Network Gateway Starter Pack featuring the R140 equipped with Econet and Ethernet adapters at a price of £2499, with a licence for the TCP/IP Protocol Suite included to allow Archimedes computers to be able to communicate with such Ethernet-based networks via the gateway. Similar Econet gateway capabilities were eventually extended to computers running RISC OS with Acorn's TCP/IP Protocol Suite product and with the broader Acorn Universal Networking (AUN) suite of technologies, and a device driver update eventually provided a similar means of routing TCP/IP communications over Econet networks for RISC OS machines. Application software In 1989, Acorn announced support for the R140 from a number of application software vendors, including Informix, along with applications such as Uniplex, Q-Office (from Quadratron), Tetraplan, Sculptor (from MPD), Sea Change (from Thomson), Recital ("a dBase compatible relational database") and Q-Calc ("a Lotus, key-compatible spreadsheet"). Applications for school administration and financial management - SIMS and SCRIPT (a COBOL-based school administration system) - were also offered in a bundle with the R140 workstation. The database application development tool DataFlex was announced for the R140 in mid-1990. Legacy Despite Acorn stating an intention to offer a Unix system from as early as 1982, with the National Semiconductor 32016 platform being the proposed vehicle for such a product, technical difficulties with the 32016's chipset led to the Acorn Cambridge Workstation - the surviving product from the Acorn Business Computer range - shipping with a proprietary Acorn operating system instead of the planned Xenix-based Unix offering. With the development of the ARM chipset, however, Acorn was finally in a position to deliver its own system capable of running Unix, announcing work as early as the autumn of 1987 on an "upmarket ARM-based workstation to run the Unix operating system" for release in mid-1988 to compete with Sun and Apollo models in the higher education market, featuring a built-in WE32206 "arithmetic co-processor", and eventually bringing the R140 to market alongside the second iteration of ARM2-based Archimedes 400-series models and the R260 to market alongside the high-end, ARM3-based A540, all within the space of a couple of years. Nevertheless, Acorn discontinued R260 production in 1993, shortly after announcing the floating point accelerator unit, which had been announced in 1991 and repeatedly delayed, and subsequently offered no new RISC iX system products. Although there were expectations that Acorn's corporate parent, Olivetti, might have provided opportunities for ARM-based Unix workstation products, leveraging its relationship with AT&T as the proprietor of Unix, it became apparent that AT&T's own interests lay with products based on the SPARC architecture. Olivetti itself had previously made a workstation, the CP486, based on the Intel 80486 running SCO Unix or Xenix and offering support for the Weitek 4167 floating point unit and Intel i860 "application accelerator". This machine was available in 1989 and described as the basis of a "high-cost authoring workstation" in a European initiative, but was rather more expensive than Acorn's RISC iX workstations, costing $16,250 for a configuration with 4 MB of RAM and 150 MB hard disk. Crude hardware performance comparisons based on Dhrystone benchmarking under like-for-like environments - taking results from CP486 benchmarks run under DOS and from Archimedes benchmarks run under RISC OS - indicate that the CP486 (rated at 25456 Dhrystones per second) was several times faster than the R140 (similar ARM2-based machines producing a rating of approximately 6000) and was still considerably faster than the R260 (rated at 22425). Floating-point arithmetic performance of the CP486 was approximately double that of the R260 with FPA fitted (5847 KWhetstones per second for the former versus 2788 for the latter). In 1994, the Risc PC launched with an improved chipset that was amenable to running Unix, and amidst a certain level of interest in the "large potential" of Unix running on the new machine, the independent RiscBSD initiative was announced in August 1994 to bring "a base of BSD4.4 - probably the NetBSD flavour" to this hardware platform. A "very, very alpha kernel" was demonstrated after six weeks of initial effort by the RiscBSD developers at the Acorn World show in late 1994. Meanwhile, another initiative, ArcBSD, sought to port FreeBSD to "all 32-bit Acorn machines with sufficient RAM and hard disc space". Although not developed with any significant Acorn involvement, RiscBSD eventually became NetBSD/arm32 (being imported in NetBSD 1.2) and was used in a Risc PC-based product sold by Acorn's education joint venture, Xemplar, called NCServer. Support for this product continued after the Apple takeover of Xemplar in 1999 through a company, Precedence Technologies, founded to continue development having acquired the remaining network computer inventory. The product evolved to employ server hardware based on the Simtec CATS board, providing access to files and applications stored on the server via an HTML-based interface, with RISC OS-based network computers being able to run the NCWorks suite of applications customised from various familiar RISC OS applications such as Draw, Paint, EasiWriter, DataPower and Schema. References External links RISCiX computers Playing with UNIX The R140 Acorn operating systems ARM operating systems Berkeley Software Distribution Discontinued operating systems 1988 software

Operating System (OS)

Virtual DOS machine Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware, and is a userland that originated in earlier versions of Windows and included up to Windows 10. Overview Virtual DOS machines can operate either exclusively through typical software emulation methods (e.g. dynamic recompilation) or can rely on the virtual 8086 mode of the Intel 80386 processor, which allows real mode 8086 software to run in a controlled environment by catching all operations which involve accessing protected hardware and forwarding them to the normal operating system (as exceptions). The operating system can then perform an emulation and resume the execution of the DOS software. VDMs generally also implement support for running 16- and 32-bit protected mode software (DOS extenders), which has to conform to the DOS Protected Mode Interface (DPMI). When a DOS program running inside a VDM needs to access a peripheral, Windows will either allow this directly (rarely), or will present the DOS program with a virtual device driver (VDD) which emulates the hardware using operating system functions. A VDM will systematically have emulations for the Intel 8259A interrupt controllers, the 8254 timer chips, the 8237 DMA controller, etc. Concurrent DOS 8086 emulation mode In January 1985 Digital Research together with Intel previewed Concurrent DOS 286 1.0, a version of Concurrent DOS capable of running real mode DOS programs in the 80286's protected mode. The method devised on B-1 stepping processor chips, however, in May 1985 stopped working on the C-1 and subsequent processor steppings shortly before Digital Research was about to release the product. Although with the E-1 stepping Intel started to address the issues in August 1985, so that Digital Research's "8086 emulation mode" worked again utilizing the undocumented LOADALL processor instruction, it was too slow to be practical. Microcode changes for the E-2 stepping improved the speed again. This early implementation can be seen as a predecessor to actual virtual DOS machines. Eventually, Concurrent DOS 286 was reworked from a potential desktop operating system to become FlexOS 286 for industrial use in 1986. It was also licensed by IBM for their 4680 OS in 1986. When Intel's 80386 with its virtual 8086 mode became available (as samples since October 1985 and in quantities since June 1986), Digital Research switched to use this to run real mode DOS programs in virtual DOS machines in protected mode under Concurrent DOS 386 1.0 (February 1987) and FlexOS 386 1.0 (June 1987). However, the architecture of these multiuser multitasking protected mode operating systems was not DOS-based by themselves. Concurrent DOS 386 was later developed to become Multiuser DOS (since 1991) and REAL/32 (since 1995). FlexOS 386 later became 4690 OS in 1993. DOS-based VDMs In contrast to these protected mode operating systems, DOS, by default, is a real-mode operating system, switching to protected mode and virtual 86 mode only on behalf of memory managers and DOS extenders in order to provide access to extended memory or map in memory into the first megabyte, which is accessible to normal DOS programs. DOS-based VDMs appeared with Microsoft's Windows/386 2.01 in September 1987. DOS-based virtual DOS machines were also present in Windows 3.0, 3.1x and Windows for Workgroups 3.1x running in 386 Enhanced Mode as well as in Windows 95, 98, 98 SE and ME. One of the characteristics of these solutions running on top of DOS is that the memory layout shown inside virtual DOS machines are virtual instances of the DOS system and DOS driver configuration run before the multitasker is loaded, and that requests which cannot be handled in protected mode are passed down into the system domain to be executed by the underlying DOS system. Similar to Windows 3.x 386 Enhanced Mode in architecture, EMM386 3.xx of Novell DOS 7, Caldera OpenDOS 7.01, DR-DOS 7.02 (and later) also uses DOS-based VDMs to support pre-emptive multitasking of multiple DOS applications, when the EMM386 /MULTI option is used. This component has been under development at Digital Research / Novell since 1991 under the codename "Vladivar" (originally a separate device driver KRNL386.SYS instead of a module of EMM386). While primarily developed for the next major version of DR DOS, released as Novell DOS 7 in 1994, it was also used in the never released DR DOS "Panther" and "Star Trek" project in 1992/1993. OS/2 MVDM VDMs called MVDM (Multiple Virtual DOS Machine) are used in OS/2 2.0 and later since 1992. OS/2 MVDMs are considerably more powerful than NTVDM. For example, block devices are supported, and various DOS versions can be booted into an OS/2 MVDM. While the OS/2 1.x DOS box was based on DOS 3.0, OS/2 2.x MVDMs emulate DOS 5.0. Seamless integration of Windows 3.1 and later Win32s applications in OS/2 is a concept looking similar on surface to the seamless integration of XP Mode based on Windows Virtual PC in Windows 7. A redirector in a "guest" VDM or NTVDM allows access on the disks of the OS/2 or NT "host". Applications in a "guest" can use named pipes for communication with their "host". Due to a technical limitation, DOS and 16-bit Windows applications under OS/2 were unable to see more than 2 GB of hard drive space, this was fixed in ArcaOS 5.0.4. Windows NTVDM NTVDM is a system component of all IA-32 editions of the Windows NT family from 1993 with the release of Windows NT 3.1 until 2015 with its final appearance in Windows 10, which allows execution of 16-bit Windows and 16-bit / 32-bit DOS applications. It is not included with 64-bit versions. The Windows NT 32-bit user-mode executable which forms the basis for a single DOS (or Windows 3.x) environment is called ntvdm.exe. In order to execute DOS programs, NTVDM loads NTIO.SYS which in turn loads NTDOS.SYS, which executes a modified COMMAND.COM in order to run the application that was passed to NTVDM as command-line argument. The 16-bit real-mode system files are stripped down derivations of their MS-DOS 5.0 equivalents IO.SYS, MSDOS.SYS and COMMAND.COM with all hard-wired assumptions on the FAT file system removed and using the invalid opcode 0xC4 0xC4 to bop down into the 32-bit NTVDM to handle the requests. Originally, NTDOS reported a DOS version of 30.00 to programs, but this was soon changed to report a version of 5.00 at INT 21h/AH=30h and 5.50 at INT 21h/AX=3306h to allow more programs to run unmodified. This holds true even in the newest releases of Windows; many additional MS-DOS functions and commands introduced in MS-DOS versions 6.x and in Windows 9x are missing. 16-bit Windows applications by default all run in their own thread within a single NTVDM process. Although NTVDM itself is a 32-bit process and pre-emptively multitasked with respect to the rest of the system, the 16-bit applications within it are cooperatively multitasked with respect to each other. When the "Run in separate memory space" option is checked in the Run box or the application's shortcut file, each 16-bit Windows application gets its own NTVDM process and is therefore pre-emptively multitasked with respect to other processes, including other 16-bit Windows applications. NTVDM emulates BIOS calls and tables as well as the Windows 3.1 kernel and 16-bit API stubs. The 32-bit WoW translation layer thunks 16-bit API routines. 32-bit DOS emulation is present for DOS Protected Mode Interface (DPMI) and 32-bit memory access. This layer converts the necessary extended and expanded memory calls for DOS functions into Windows NT memory calls. wowexec.exe is the emulation layer that emulates 16-bit Windows. Windows 2000 and Windows XP added Sound Blaster 2.0 emulation. 16-bit virtual device drivers and DOS block device drivers (e.g., RAM disks) are not supported. Inter-process communication with other subsystems can take place through OLE, DDE and named pipes. Since virtual 8086 mode is not available on non-x86-based processors (more specifically, MIPS, DEC Alpha, and PowerPC) NTVDM was instead implemented as a full emulator in these versions of NT, using code licensed from Insignia's SoftPC. Up to Windows NT 3.51, only 80286 emulation was available. With Windows NT 4.0, 486 emulation was added. With Windows 11 dropping support for 32-bit IA-32 processors, development of NTVDM has been discontinued. Commands The following list of commands is part of the Windows XP MS-DOS subsystem. APPEND DEBUG EDIT EDLIN EXE2BIN FASTOPEN FORCEDOS GRAPHICS LOADFIX LOADHIGH (LH) MEM NLSFUNC SETVER SHARE Security issue In January 2010, Google security researcher Tavis Ormandy revealed a serious security flaw in Windows NT's VDM implementation that allowed unprivileged users to escalate their privileges to SYSTEM level, noted as applicable to the security of all x86 versions of the Windows NT kernel since 1993. This included all 32-bit versions of Windows NT, 2000, XP, Server 2003, Vista, Server 2008, and Windows 7. Ormandy published a proof-of-concept exploit for the vulnerability. Prior to Microsoft's release of a security patch, the workaround for this issue was to turn off 16-bit application support, which prevented older programs (those written for DOS and Windows 3.1) from running. 64-bit versions of Windows were not affected since NTVDM subsystem is not installed by default. Once the Microsoft security patches had been applied to the affected operating systems the VDM could be safely reenabled. Limitations A limitation exists in the Windows XP 16-bit subsystem (but not in earlier versions of Windows NT) because of the raised per-session limit for GDI objects which causes GDI handles to be shifted to the right by two bits, when converting them from 32 to 16 bits. As a result, the actual handle cannot be larger than 14 bits and consequently 16-bit applications that happen to be served a handle larger than 16384 by the GDI system crash and terminate with an error message. In an x86-64 CPU, virtual 8086 mode is available as a sub-mode only in its legacy mode (for running 16- and 32-bit operating systems), not in the native 64-bit long mode. The NTVDM is not supported on x86-64 editions of Windows, including DOS programs, because NTVDM uses VM86 CPU mode instead of the Local Descriptor Table in order to enable 16‑bits segment required for addressing and AArch64 because Microsoft did not release a full emulator for this incompatible instruction set like it did on previous incompatible architecture. However, they can still be run using virtualization software, like Windows XP Mode in Windows 7 or VMware Workstation, or by installing NTVDMx64, an unofficial port of the older emulated implementation of the NTVDM which was provided on NT 4 for non-x86 platforms. Another option is OTVDM (WineVDM), a 16-bit Windows interpreter based on MAME's i386 emulation and the 16-bit part of the popular Windows compatibility layer Wine. In general, VDM and similar technologies do not satisfactorily run most older DOS games on today's computers. Emulation is only provided for the most basic peripherals, often implemented incompletely. For example, sound emulation in NTVDM is very limited. NT-family versions of Windows only update the real screen a few times per second when a DOS program writes to it, and they do not emulate higher resolution graphics modes. Because software mostly runs native at the speed of the host CPU, all timing loops will expire prematurely. This either makes a game run much too fast or causes the software not even to notice the emulated hardware peripherals, because it does not wait long enough for an answer. See also Comparison of platform virtualization software DESQview 386 (since 1988) Wine (software) DOSBox DOSEMU Merge (software) List of Microsoft Windows components Hypervisor Windows on Windows (WoW) Virtual machine (VM) Notes References Further reading External links Virtual DOS Machine Structure Troubleshooting MS-DOS-based programs in Windows XP Troubleshooting an MS-DOS application which hangs the NTVDM subsystem in Windows XP and Windows Server 2003 Troubleshooting MS-DOS-based serial communication programs in Windows 2000 and later MS-DOS Player for Win32-x64, a Microsoft MS-DOS Emulator, runs many command line DOS programs like compilers or other tools, also packaged into one stand-alone executable file. vDOS, a DOS emulator designed for the running the more "serious" DOS apps (not games) on 64-bit NT systems (effectively a replacement for NTVDM on modern systems). Virtualization software DOS technology Windows administration DOS emulators Windows components

Operating System (OS)

NetBSD NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems. The NetBSD project focuses on code clarity, careful design, and portability across many computer architectures. Its source code is publicly available and permissively licensed. History NetBSD was originally derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, Berkeley, via their Net/2 source code release and the 386BSD project. The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development. The four founders of the NetBSD project, Chris Demetriou, Theo de Raadt, Adam Glass, and Charles Hannum, felt that a more open development model would benefit the project: one centered on portable, clean, correct code. They aimed to produce a unified, multi-platform, production-quality, BSD-based operating system. The name "NetBSD" was chosen based on the importance and growth of networks such as the Internet at that time, and the distributed, collaborative nature of its development. The NetBSD source code repository was established on 21 March 1993 and the first official release, NetBSD 0.8, was made on 19 April 1993. This was derived from 386BSD 0.1 plus the version 0.2.2 unofficial patchkit, with several programs from the Net/2 release missing from 386BSD re-integrated, and various other improvements. The first multi-platform release, NetBSD 1.0, was made in October 1994, and being updated with 4.4BSD-Lite sources, it was free of all legally encumbered 4.3BSD Net/2 code. Also in 1994, for disputed reasons, one of the founders, Theo de Raadt, was removed from the project. He later founded a new project, OpenBSD, from a forked version of NetBSD 1.0 near the end of 1995. In 1998, NetBSD 1.3 introduced the pkgsrc packages collection. Until 2004, NetBSD 1.x releases were made at roughly annual intervals, with minor "patch" releases in between. From release 2.0 onwards, NetBSD uses semantic versioning, and each major NetBSD release corresponds to an incremented major version number, i.e. the major releases following 2.0 are 3.0, 4.0 and so on. The previous minor releases are now divided into two categories: x.y "stable" maintenance releases and x.y.z releases containing only security and critical fixes. Features Portability As the project's motto ("Of course it runs NetBSD" ) suggests, NetBSD has been ported to a large number of 32- and 64-bit architectures. These range from VAX minicomputers to Pocket PC PDAs. As of 2019, NetBSD supports 59 hardware platforms (across 16 different instruction sets). The kernel and userland for these platforms are all built from a central unified source-code tree managed by CVS. Currently, unlike other kernels such as μClinux, the NetBSD kernel requires the presence of an MMU in any given target architecture. NetBSD's portability is aided by the use of hardware abstraction layer interfaces for low-level hardware access such as bus input/output or DMA. Using this portability layer, device drivers can be split into "machine-independent" and "machine-dependent" components. This makes a single driver easily usable on several platforms by hiding hardware access details, and reduces the work to port it to a new system. This permits a particular device driver for a PCI card to work without modifications, whether it is in a PCI slot on an IA-32, Alpha, PowerPC, SPARC, or other architecture with a PCI bus. Also, a single driver for a specific device can operate via several different buses, like ISA, PCI, or PC Card. In comparison, Linux device driver code often must be reworked for each new architecture. As a consequence, in porting efforts by NetBSD and Linux developers, NetBSD has taken much less time to port to new hardware. This platform independence aids the development of embedded systems, particularly since NetBSD 1.6, when the entire toolchain of compilers, assemblers, linkers, and other tools fully support cross-compiling. In 2005, as a demonstration of NetBSD's portability and suitability for embedded applications, Technologic Systems, a vendor of embedded systems hardware, designed and demonstrated a NetBSD-powered kitchen toaster. Commercial ports to embedded platforms, including the AMD Geode LX800, Freescale PowerQUICC processors, Marvell Orion, AMCC 405 family of PowerPC processors, Intel XScale IOP and IXP series, were available from and supported by Wasabi Systems. Portable build framework The NetBSD cross-compiling framework (also known as "build.sh") lets a developer build a complete NetBSD system for an architecture from a more powerful system of different architecture (cross-compiling), including on a different operating system (the framework supports most POSIX-compliant systems). Several embedded systems using NetBSD have required no additional software development other than toolchain and target rehost. The pkgsrc packages collection NetBSD features pkgsrc (short for "package source"), a framework for building and managing third-party application software packages. The pkgsrc collection consists of more than 20,000 packages as of . Building and installing packages such as KDE, GNOME, the Apache HTTP Server or Perl is performed through the use of a system of makefiles. This can automatically fetch the source code, unpack, patch, configure, build and install the package such that it can be removed again later. An alternative to compiling from source is to use a precompiled binary package. In either case, any prerequisites/dependencies will be installed automatically by the package system, without need for manual intervention. pkgsrc supports not only NetBSD, but also several other BSD variants like FreeBSD and Darwin/Mac OS X, and other Unix-like operating systems such as Linux, Solaris, IRIX, and others, as well as Interix. pkgsrc was previously adopted as the official package management system for DragonFly BSD. Symmetric multiprocessing NetBSD has supported SMP since the NetBSD 2.0 release in 2004, which was initially implemented using the giant lock approach. During the development cycle of the NetBSD 5 release, major work was done to improve SMP support; most of the kernel subsystems were modified to use the fine-grained locking approach. New synchronization primitives were implemented and scheduler activations was replaced with a 1:1 threading model in February 2007. A scalable M2 thread scheduler was implemented, though the old 4.4BSD scheduler still remains the default but was modified to scale with SMP. Threaded software interrupts were implemented to improve synchronization. The virtual memory system, memory allocator and trap handling were made MP safe. The file system framework, including the VFS and major file systems were modified to be MP safe. Since April 2008 the only subsystems running with a giant lock are the network protocols and most device drivers. Security NetBSD provides various features in the security area. The Kernel Authorization framework (or Kauth) is a subsystem managing all authorization requests inside the kernel, and used as system-wide security policy. It allows external modules to plug-in the authorization process. NetBSD also incorporates exploit mitigation features, ASLR, KASLR, restricted mprotect() and Segvguard from the PaX project, and GCC Stack Smashing Protection (SSP, or also known as ProPolice, enabled by default since NetBSD 6.0) compiler extensions. Verified Executables (or Veriexec) is an in-kernel file integrity subsystem in NetBSD. It allows the user to set digital fingerprints (hashes) of files, and take a number of different actions if files do not match their fingerprints. For example, one can allow Perl to run only scripts that match their fingerprints. The cryptographic device driver (CGD) allows using disks or partitions (including CDs and DVDs) for encrypted storage. Virtualization The Xen virtual-machine monitor has been supported in NetBSD since release 3.0. The use of Xen requires a special pre-kernel boot environment that loads a Xen-specialized kernel as the "host OS" (Dom0). Any number of "guest OSes" (DomU) virtualized computers, with or without specific Xen/DomU support, can be run in parallel with the appropriate hardware resources. The need for a third-party boot manager, such as GRUB, was eliminated with NetBSD 5's Xen-compatible boot manager. NetBSD 6 as a Dom0 has been benchmarked comparably to Linux, with better performance than Linux in some tests. As of NetBSD 9.0, accelerated virtualization is provided through the native hypervisor NVMM (NetBSD Virtual Machine Monitor). It provides a virtualization API, libnvmm, that can be leveraged by emulators such as QEMU. A unique property of NVMM is that the kernel never accesses guest VM memory, only creating it. Intel's Hardware Accelerated Execution Manager (HAXM) provides an alternative solution for acceleration in QEMU for Intel CPUs only, similar to Linux's KVM. NetBSD 5.0 introduced the rump kernel, an architecture to run drivers in user-space by emulating kernel-space calls. This anykernel architecture allows adding support of NetBSD drivers to other kernel architectures, ranging from exokernels to monolithic kernels. Storage NetBSD includes many enterprise features like iSCSI, a journaling filesystem, logical volume management and the ZFS filesystem. The bio(4) interface for vendor-agnostic RAID volume management through bioctl has been available in NetBSD since 2007. The WAPBL journaling filesystem, an extension of the BSD FFS filesystem, was contributed by Wasabi Systems in 2008. The NetBSD Logical Volume Manager is based on a BSD reimplementation of a device-mapper driver and a port of the Linux Logical Volume Manager tools. It was mostly written during the Google Summer of Code 2008. The ZFS filesystem developed by Sun Microsystems was imported into the NetBSD base system in 2009. Currently, the NetBSD ZFS port is based on ZFS version 22. The CHFS Flash memory filesystem was imported into NetBSD in November 2011. CHFS is a file system developed at the Department of Software Engineering, University of Szeged, Hungary, and is the first open source Flash-specific file system written for NetBSD. Compatibility with other operating systems At the source code level, NetBSD is very nearly entirely compliant with POSIX.1 (IEEE 1003.1-1990) standard and mostly compliant with POSIX.2 (IEEE 1003.2-1992). NetBSD provides system call-level binary compatibility on the appropriate processor architectures with its previous releases, but also with several other UNIX-derived and UNIX-like operating systems, including Linux, and other 4.3BSD derivatives like SunOS 4. This allows NetBSD users to run many applications that are only distributed in binary form for other operating systems, usually with no significant loss of performance. A variety of "foreign" disk filesystem formats are also supported in NetBSD, including ZFS, FAT, NTFS, Linux ext2fs, Apple HFS and OS X UFS, RISC OS FileCore/ADFS, AmigaOS Fast File System, IRIX EFS, Version 7 Unix File System, and many more through PUFFS. Kernel scripting Kernel-space scripting with the Lua programming language is a relatively new feature in NetBSD; it is available as of NetBSD 7.0. The Lua language (i.e., its interpreter and standard libraries) was initially ported to the NetBSD kernel during Google Summer of Code 2010 and has undergone several improvements since then. There are two main differences between user and kernel space Lua: kernel Lua does not support floating-point numbers; as such, only Lua integers are available. It also does not have full support to user space libraries that rely on the operating system (e.g., io and os). Sensors NetBSD has featured a native hardware monitoring framework since 1999/2000, and in 2003, it served as the inspiration behind the OpenBSD's sysctl hw.sensors framework when some NetBSD drivers were being ported to OpenBSD. , NetBSD had close to 85 device drivers exporting data through the API of the envsys framework. Since the 2007 revision, serialisation of data between the kernel and userland is done through XML property lists with the help of NetBSD's proplib(3). Uses NetBSD's clean design, high performance, scalability, and support for many architectures has led to its use in embedded devices and servers, especially in networking applications. A commercial real-time operating system, QNX, uses a network stack based on NetBSD code, and provides various drivers ported from NetBSD. Dell Force10 uses NetBSD as the underlying operating system that powers FTOS (the Force10 Operating System), which is used in high scalability switch/routers. Force10 also made a donation to the NetBSD Foundation in 2007 to help further research and the open development community. Wasabi Systems provides a commercial Wasabi Certified BSD product based on NetBSD with proprietary enterprise features and extensions, which are focused on embedded, server and storage applications. NetBSD was used in NASA's SAMS-II Project of measuring the microgravity environment on the International Space Station, and for investigations of TCP for use in satellite networks. In 2004, SUNET used NetBSD to set the Internet2 Land Speed Record. NetBSD was chosen "due to the scalability of the TCP code". NetBSD is also used in Apple's AirPort Extreme and Time Capsule products, instead of their own OS X (most of whose Unix-level userland code is derived from FreeBSD code but some is derived from NetBSD code). The operating system of the T-Mobile Sidekick LX 2009 smartphone is based on NetBSD. The Minix operating system uses a mostly NetBSD userland as well as its pkgsrc packages infrastructure since version 3.2. Parts of macOS were originally taken from NetBSD, such as some userspace command line tools. Licensing All of the NetBSD kernel and most of the core userland source code is released under the terms of the BSD License (two, three, and four-clause variants). This essentially allows everyone to use, modify, redistribute or sell it as they wish, as long as they do not remove the copyright notice and license text (the four-clause variants also include terms relating to publicity material). Thus, the development of products based on NetBSD is possible without having to make modifications to the source code public. In contrast, the GPL, which does not apply to NetBSD, stipulates that changes to source code of a product must be released to the product recipient when products derived from those changes are released. On 20 June 2008, the NetBSD Foundation announced a transition to the two clause BSD license, citing concerns with UCB support of clause 3 and industry applicability of clause 4. NetBSD also includes the GNU development tools and other packages, which are covered by the GPL and other open source licenses. As with other BSD projects, NetBSD separates those in its base source tree to make it easier to remove code that is under more restrictive licenses. As for packages, the installed software licenses may be controlled by modifying the list of allowed licenses in the pkgsrc configuration file (mk.conf). Releases The following table lists major NetBSD releases and their notable features in reverse chronological order. Minor and patch releases are not included. Logo The NetBSD "flag" logo, designed by Grant Bissett, was introduced in 2004 and is an abstraction of their older logo, designed by Shawn Mueller in 1994. Mueller's version was based on the famous World War II photograph Raising the Flag on Iwo Jima. The NetBSD Foundation The NetBSD Foundation is the legal entity that owns the intellectual property and trademarks associated with NetBSD, and on 22 January 2004, became a 501(c)3 tax-exempt non-profit organization. The members of the foundation are developers who have CVS commit access. The NetBSD Foundation has a Board of Directors, elected by the voting of members for two years. Hosting Hosting for the project is provided primarily by Columbia University, and Western Washington University, fronted by a CDN provided by Fastly. Mirrors for the project are spread around the world and provided by volunteers and supporters of the project. See also Comparison of operating systems Comparison of operating system kernels References External links ARM operating systems Lightweight Unix-like systems PowerPC operating systems Software using the BSD license 1993 software X86-64 operating systems IA-32 operating systems

Operating System (OS)

User space and kernel space A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kernel space is strictly reserved for running a privileged operating system kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where application software and some drivers execute. Overview The term userland (or user space) refers to all code that runs outside the operating system's kernel. Userland usually refers to the various programs and libraries that the operating system uses to interact with the kernel: software that performs input/output, manipulates file system objects, application software, etc. Each user space process normally runs in its own virtual memory space, and, unless explicitly allowed, cannot access the memory of other processes. This is the basis for memory protection in today's mainstream operating systems, and a building block for privilege separation. A separate user mode can also be used to build efficient virtual machines – see Popek and Goldberg virtualization requirements. With enough privileges, processes can request the kernel to map part of another process's memory space to its own, as is the case for debuggers. Programs can also request shared memory regions with other processes, although other techniques are also available to allow inter-process communication. Implementation The most common way of implementing a user mode separate from kernel mode involves operating system protection rings. Protection rings, in turn, are implemented using CPU modes. Typically, kernel space programs run in kernel mode, also called supervisor mode; normal applications in user space run in user mode. Many operating systems are single address space operating systems—they have a single address space for all user-mode code. (The kernel-mode code may be in the same address space, or it may be in a second address space). Many other operating systems have a per-process address space, a separate address space for each and every user-mode process. Another approach taken in experimental operating systems is to have a single address space for all software, and rely on a programming language's semantics to make sure that arbitrary memory cannot be accessed – applications simply cannot acquire any references to the objects that they are not allowed to access. This approach has been implemented in JXOS, Unununium as well as Microsoft's Singularity research project. See also BIOS CPU modes Early user space Memory protection OS-level virtualization Notes References External links Linux Kernel Space Definition Operating system technology Device drivers

Operating System (OS)

Linux kernel The Linux kernel is a mostly free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for UNIX. Linux as a whole is released under the GNU General Public License version 2 only, but it contains files under other compatible licenses. However, Linux begun including proprietary binary blobs in its source tree and main distribution in 1996. This led to other projects starting work to remove the proprietary blobs in order to produce a 100% libre kernel, which eventually led to the Linux-libre project being founded. Since the late 1990s, it has been included as part of a large number of operating system distributions, many of which are commonly also called Linux. However, there is a controversy surrounding the naming of such systems; some people, including Richard Stallman, argue calling such systems "Linux" is erroneous because the operating system is actually mostly GNU, with the Linux kernel being one component added later on in 1992, 9 years after the initiation of the GNU project in 1983, hence the name "GNU+Linux" or "GNU/Linux" should be used instead. Linux is deployed on a wide variety of computing systems, such as embedded devices, mobile devices (including its use in the Android operating system), personal computers, servers, mainframes, and supercomputers. It can be tailored for specific architectures and for several usage scenarios using a family of simple commands (that is, without the need of manually editing its source code before compilation); privileged users can also fine-tune kernel parameters at runtime. Most of the Linux kernel code is written using the GNU extensions of GCC to the standard C programming language and with the use of architecture specific instructions (ISA). This produces a highly optimized executable (vmlinux) with respect to utilization of memory space and task execution times. Day-to-day development discussions take place on the Linux kernel mailing list (LKML). Changes are tracked using the version control system git, which was originally authored by Torvalds as a free software replacement for BitKeeper. History In April 1991, Linus Torvalds, at the time a 21-year-old computer science student at the University of Helsinki, Finland, started working on some simple ideas for an operating system inspired by UNIX, for a personal computer. He started with a task switcher in Intel 80386 assembly language and a terminal driver. On 25 August 1991, Torvalds posted the following to comp.os.minix, a newsgroup on Usenet: On 17 September 1991, Torvalds prepared version 0.01 of Linux and put on the "ftp.funet.fi" – FTP server of the Finnish University and Research Network (FUNET). It was not even executable since its code still needed Minix for compilation and play. On 5 October 1991, Torvalds announced the first "official" version of Linux, version 0.02. At this point, Linux was able to run Bash, GCC, and some other GNU utilities: After that, despite the limited functionality of the early versions, Linux rapidly gained developers and users. Many people contributed code to the project, including some developers from the MINIX community. At the time, the GNU Project had created many of the components required for its free UNIX replacement, the GNU operating system, but its own kernel, GNU Hurd, was incomplete. For this reason it soon adopted Linux kernel, too. The Berkeley Software Distribution had not yet freed itself from legal encumbrances and was not competing in the space for a free OS kernel. Torvalds assigned version 0 to the kernel to indicate that it was mainly for testing and not intended for productive use. Version 0.11, released in December 1991, was the first self-hosted Linux, for it could be compiled by a computer running the same kernel. When Torvalds released version 0.12 in February 1992, he adopted the GNU General Public License version 2 (GPLv2) over his previous self-drafted license, which had not permitted commercial redistribution. In contrast to Unix, all source files of Linux are freely available, including device drivers. The initial success of Linux was driven by programmers and testers across the world. With the support of the POSIX APIs, through the libC that, whether needed, acts as an entry point to the kernel address space, Linux could run software and applications that had been developed for Unix. On 19 January 1992, the first post to the new newsgroup alt.os.linux was submitted. On 31 March 1992, the newsgroup was renamed comp.os.linux. The fact that Linux is a monolithic kernel rather than a microkernel was the topic of a debate between Andrew S. Tanenbaum, the creator of MINIX, and Torvalds. The Tanenbaum–Torvalds debate started in 1992 on the Usenet group comp.os.minix as a general discussion about kernel architectures. Linux version 0.95 was the first to be capable of running the X Window System. In March 1994, Linux 1.0.0 was released with 176,250 lines of code. It was the first version suitable for use in production environments. It started a versioning system for the kernel with three or four numbers separated by dots where the first represented the major release, the second was the minor release, and the third was the revision. At that time odd-numbered minor releases were for development and tests, whilst even numbered minor releases were for production. The optional fourth digit indicated a set of patches to a revision. Development releases were indicated with -rc ("release candidate") suffix. The current version numbering is slightly different from the above. The even vs. odd numbering has been dropped and a specific major version is now indicated by the first two numbers, taken as a whole. While the time-frame is open for the development of the next major, the -rcN suffix is used to identify the n'th release candidate for the next version. For example, the release of the version 4.16 was preceded by seven 4.16-rcN (from -rc1 to -rc7). Once a stable release is made, its maintenance is passed off to the “stable team". Occasional updates to stable releases are identified by a three numbering scheme (e.g., 4.13.1, 4.13.2, ..., 4.13.16). After version 1.3 of the kernel, Torvalds decided that Linux had evolved enough to warrant a new major number, so he released version 2.0.0 in June 1996. The series included 41 releases. The major feature of 2.0 was support for symmetric multiprocessing (SMP) and support for more types of processors. Starting with version 2.0, Linux is configurable for selecting specific hardware targets and for enabling architecture specific features and optimizations. The make *config family of commands of kbuild are used to enable and configure thousands of options for building ad hoc kernel executables (vmlinux) and loadable modules. Version 2.2, released on 20 January 1999, improved locking granularity and SMP management, added m68k, PowerPC, Sparc64, Alpha, and other 64-bit platforms support. Furthermore, it added new file systems including Microsoft's NTFS read-only capability. In 1999, IBM published its patches to the Linux 2.2.13 code for the support of the S/390 architecture. Version 2.4.0, released on 4 January 2001, contained support for ISA Plug and Play, USB, and PC Cards. Linux 2.4 added support for the Pentium 4 and Itanium (the latter introduced the ia64 ISA that was jointly developed by Intel and Hewlett-Packard to supersede the older PA-RISC), and for the newer 64-bit MIPS processor. Development for 2.4.x changed a bit in that more features were made available throughout the duration of the series, including support for Bluetooth, Logical Volume Manager (LVM) version 1, RAID support, InterMezzo and ext3 file systems. Version 2.6.0 was released on 17 December 2003. The development for 2.6.x changed further towards including new features throughout the duration of the series. Among the changes that have been made in the 2.6 series are: integration of µClinux into the mainline kernel sources, PAE support, support for several new lines of CPUs, integration of Advanced Linux Sound Architecture (ALSA) into the mainline kernel sources, support for up to 232 users (up from 216), support for up to 229 process IDs (64-bit only, 32-bit arches still limited to 215), substantially increased the number of device types and the number of devices of each type, improved 64-bit support, support for file systems which support file sizes of up to 16 terabytes, in-kernel preemption, support for the Native POSIX Thread Library (NPTL), User-mode Linux integration into the mainline kernel sources, SELinux integration into the mainline kernel sources, InfiniBand support, and considerably more. Also notable are the addition of a wide selection of file systems starting with the 2.6.x releases: now the kernel supports a large number of file systems, some that have been designed for Linux, like ext3, ext4, FUSE, Btrfs, and others that are native of other operating systems like JFS, XFS, Minix, Xenix, Irix, Solaris, System V, Windows and MS-DOS. In 2005 the stable team was formed as a response to the lack of a kernel tree where people could work on bug fixes, and it would keep updating stable versions. In February 2008 the linux-next tree was created to serve as a place where patches aimed to be merged during the next development cycle gathered. Several subsystem maintainers also adopted the suffix -next for trees containing code which they mean to submit for inclusion in the next release cycle. , the in-development version of Linux is held in an unstable branch named linux-next. Linux used to be maintained without the help of an automated source code management system until, in 2002, development switched to BitKeeper. It was freely available for Linux developers but it was not free software. In 2005, because of efforts to reverse-engineer it, the company which owned the software revoked the support of the Linux community. In response, Torvalds and others wrote Git. The new system was written within weeks, and in two months the first official kernel made using it was released. Details on the history of the 2.6 kernel series can be found in the ChangeLog files on the 2.6 kernel series source code release area of kernel.org. The 20th anniversary of Linux was celebrated by Torvalds in July 2011 with the release of the 3.0.0 kernel version. As 2.6 has been the version number for 8 years, a new uname26 personality that reports 3.x as 2.6.40+x had to be added to the kernel so that old programs would work. Version 3.0 was released on 22 July 2011. On 30 May 2011, Torvalds announced that the big change was "NOTHING. Absolutely nothing." and asked, "...let's make sure we really make the next release not just an all new shiny number, but a good kernel too." After the expected 6–7 weeks of the development process, it would be released near the 20th anniversary of Linux. On 11 December 2012, Torvalds decided to reduce kernel complexity by removing support for i386 processors, making the 3.7 kernel series the last one still supporting the original processor. The same series unified support for the ARM processor. Version 3.11, released on 2 September 2013, adds many new features such as new flag for to reduce temporary file vulnerabilities, experimental AMD Radeon dynamic power management, low-latency network polling, and zswap (compressed swap cache). The numbering change from 2.6.39 to 3.0, and from 3.19 to 4.0, involved no meaningful technical differentiation. The major version number was increased to avoid large minor numbers. Stable 3.x.y kernels were released until 3.19 in February 2015. In April 2015, Torvalds released kernel version 4.0. By February 2015, Linux had received contributions from nearly 12,000 programmers from more than 1,200 companies, including some of the world's largest software and hardware vendors. Version 4.1 of Linux, released in June 2015, contains over 19.5 million lines of code contributed by almost 14,000 programmers. A total of 1,991 developers, of whom 334 are first collaborators, added more than 553,000 lines of code to version 5.8, breaking the record previously held by version 4.9. According to the Stack Overflow’s annual Developer Survey of 2019, more than the 53% of all respondents have developed software for Linux OS and about 27% for Android, although only about 25% develop with Linux-based operating systems. Most websites run on Linux-based operating systems, and all of the world's 500 most powerful supercomputers use some kind of OS based on Linux. Linux distributions bundle the kernel with system software (e.g., the GNU C Library, systemd, and others Unix utilities and daemons) and a wide selection of application software, but their usage share in desktops is low in comparison to other operating systems. Android, which accounts for the majority of the installed base of all operating systems for mobile devices, is responsible for the rising usage of the Linux kernel, together with its wide use in a large variety of embedded devices. Architecture and features Linux is a monolithic kernel with a modular design (e.g., it can insert and remove loadable kernel modules at runtime), supporting most features once only available in closed source kernels of non-free operating systems. The rest of the article makes use of the UNIX and Unix-like operating systems convention on the official manual pages. The numbers that follow the name of commands, interfaces, and other features, have the purpose of specifying the section (i.e., the type of the OS' component or feature) they belong to (e.g., refers to a system call, while refers to a userspace library wrapper). The following list and the subsequent sections describe a non-comprehensive overview of Linux architectural design and of some of its noteworthy features. Concurrent computing and (with the availability of enough CPU cores for tasks that are ready to run) even true parallel execution of many processes at once (each of them having one or more threads of execution) on SMP and NUMA architectures. Selection and configuration of hundreds of kernel features and drivers (using one of the family of commands, before running compilation), modification of kernel parameters before booting (usually by inserting instructions into the lines of the GRUB2 menu), and fine tuning of kernel behavior at run-time (using the interface to ). Configuration (again using the commands) and run-time modifications of the policies (via , , and the family of syscalls) of the task schedulers that allow preemptive multitasking (both in user mode and, since the 2.6 series, in kernel mode); the Completely Fair Scheduler (CFS) is the default scheduler of Linux since 2007 and it uses a red-black tree which can search, insert and delete process information (task struct) with O(log n) time complexity, where n is the number of runnable tasks. Advanced memory management with paged virtual memory. Inter-process communications and synchronization mechanism. A virtual filesystem on top of several concrete filesystems (ext4, Btrfs, XFS, JFS, FAT32, and many more). Configurable I/O schedulers, syscall that manipulates the underlying device parameters of special files (it is a non standard system call, since arguments, returns, and semantics depends on the device driver in question), support for POSIX asynchronous I/O (however, because they scale poorly with multithreaded applications, a family of Linux specific I/O system calls () had to be created for the management of asynchronous I/O contexts suitable for concurrently processing). OS-level virtualization (with Linux-VServer), paravirtualization and hardware-assisted virtualization (with KVM or Xen, and using QEMU for hardware emulation); On the Xen hypervisor, the Linux kernel provides support to build Linux distributions (such as openSuSE Leap and many others) that work as Dom0, that are virtual machine host servers that provide the management environment for the user's virtual machines (DomU). I/O Virtualization with VFIO and SR-IOV. Virtual Function I/O (VFIO) exposes direct device access to user space in a secure memory (IOMMU) protected environment. With VFIO, a VM Guest can directly access hardware devices on the VM Host Server. This technique improves performance, if compared both to Full virtualization and Paravirtualization. However, with VFIO, devices cannot be shared with multiple VM guests. Single Root I/O Virtualization (SR-IOV) combines the performance gains of VFIO and the ability to share a device with several VM Guests (but it requires special hardware that must be capable to appear to two or more VM guests as different devices). Security mechanisms for discretionary and mandatory access control (SELinux, AppArmor, POSIX ACLs, and others). Several types of layered communication protocols (including the Internet protocol suite). Asymmetric multiprocessing via the RPMsg subsystem. Most Device drivers and kernel extensions run in kernel space (ring 0 in many CPU architectures), with full access to the hardware. Some exceptions run in user space; notable examples are filesystems based on FUSE/CUSE, and parts of UIO. Furthermore, the X Window System and Wayland, the windowing system and display server protocols that most people use with Linux, do not run within the kernel. Differently, the actual interfacing with GPUs of graphics cards is an in-kernel subsystem called Direct Rendering Manager (DRM). Unlike standard monolithic kernels, device drivers are easily configured as modules, and loaded or unloaded while the system is running and can also be pre-empted under certain conditions in order to handle hardware interrupts correctly and to better support symmetric multiprocessing. By choice, Linux has no stable device driver application binary interface. Linux typically makes use of memory protection and virtual memory and can also handle non-uniform memory access, however the project has absorbed μClinux which also makes it possible to run Linux on microcontrollers without virtual memory. The hardware is represented in the file hierarchy. User applications interact with device drivers via entries in the or directories. Processes information as well are mapped to the file system through the directory. Interfaces Linux is a clone of UNIX, and aims towards POSIX and Single UNIX Specification compliance. The kernel also provides system calls and other interfaces that are Linux-specific. In order to be included in the official kernel, the code must comply with a set of licensing rules. The Linux Application binary interface (ABI) between the kernel and the user space has four degrees of stability (stable, testing, obsolete, removed); however, the system calls are expected to never change in order to not break the userspace programs that rely on them. Loadable kernel modules (LKMs), by design, cannot rely on a stable ABI. Therefore they must always be recompiled whenever a new kernel executable is installed in a system, otherwise they will not be loaded. In-tree drivers that are configured to become an integral part of the kernel executable (vmlinux) are statically linked by the building process. There is also no guarantee of stability of source-level in-kernel API and, because of this, device drivers code, as well as the code of any other kernel subsystem, must be kept updated with kernel evolution. Any developer who makes an API change is required to fix any code that breaks as the result of their change. Kernel-to-userspace API The set of the Linux kernel API that regards the interfaces exposed to user applications is fundamentally composed of UNIX and Linux-specific system calls. A system call is an entry point into the Linux kernel. For example, among the Linux-specific ones there is the family of the system calls. Most extensions must be enabled by defining the _GNU_SOURCE macro in a header file or when the user-land code is being compiled. System calls can only be invoked by using assembly instructions which enable the transition from unprivileged user space to privileged kernel space in ring 0. For this reason, the C standard library (libC) acts as a wrapper to most Linux system calls, by exposing C functions that, only whether it is needed, can transparently enter into the kernel which will execute on behalf of the calling process. For those system calls not exposed by libC, e.g. the fast userspace mutex (futex), the library provides a function called which can be used to explicitly invoke them. Pseudo filesystems (e.g., the sysfs and procfs filesystems) and special files (e.g., /dev/random, /dev/sda, /dev/tty, and many others) constitute another layer of interface to kernel data structures representing hardware or logical (software) devices. Kernel-to-userspace ABI Because of the differences existing between the hundreds of various implementations of the Linux OS, executable objects, even though they are compiled, assembled, and linked for running on a specific hardware architecture (that is, they use the ISA of the target hardware), often cannot run on different Linux Distributions. This issue is mainly due to distribution-specific configurations and a set of patches applied to the code of the Linux kernel, differences in system libraries, services (daemons), filesystem hierarchies, and environment variables. The main standard concerning application and binary compatibility of Linux distributions is the Linux Standard Base (LSB). However, the LSB goes beyond what concerns the Linux kernel, because it also defines the desktop specifications, the X libraries and Qt that have little to do with it. The LSB version 5 is built upon several standards and drafts (POSIX, SUS, X/Open, File System Hierarchy (FHS), and others). The parts of the LSB largely relevant to the kernel are the General ABI (gABI), especially the System V ABI and the Executable and Linking Format (ELF), and the Processor Specific ABI (psABI), for example the Core Specification for X86-64. The standard ABI for how x86_64 user programs invoke system calls is to load the syscall number into the rax register, and the other parameters into rdi, rsi, rdx, r10, r8, and r9, and finally to put the syscall assembly instruction in the code. In-kernel API There are several kernel internal APIs utilized between the different subsystems. Some are available only within the kernel subsystems, while a somewhat limited set of in-kernel symbols (i.e., variables, data structures, and functions) is exposed also to dynamically loadable modules (e.g., device drivers loaded on demand) whether they're exported with the and macros (the latter reserved to modules released under a GPL-compatible license). Linux provides in-kernel APIs that manipulate data structures (e.g., linked lists, radix trees, red-black trees, queues) or perform common routines (e.g., copy data from and to user space, allocate memory, print lines to the system log, and so on) that have remained stable at least since Linux version 2.6. In-kernel APIs include libraries of low-level common services used by device drivers: SCSI Interfaces and libATA respectively, a peer-to-peer packet based communication protocol for storage devices attached to USB, SATA, SAS, Fibre Channel, FireWire, ATAPI device, and an in-kernel library to support [S]ATA host controllers and devices. Direct Rendering Manager (DRM) and Kernel Mode Setting (KMS) for interfacing with GPUs and supporting the needs of modern 3D-accelerated video hardware, and for setting screen resolution, color depth and refresh rate DMA buffers (DMA-BUF) for sharing buffers for hardware direct memory access across multiple device drivers and subsystems Video4Linux for video capture hardware Advanced Linux Sound Architecture (ALSA) for sound cards New API for network interface controllers mac80211 and cfg80211 - for wireless network interface controllers In-kernel ABI The Linux developers chose not to maintain a stable in-kernel ABI. Modules compiled for a specific version of the kernel cannot be loaded into another version without being recompiled, assuming that the in-kernel API has remained the same at the source level; otherwise, the module code must also be modified accordingly. Processes and threads Linux creates processes by means of the or by the newer system calls. Depending on the given parameters, the new entity can share most or none of the resources of the caller. These syscalls can create new entities ranging from new independent processes (each having a special identifier called TGID within the task_struct data structure in kernel space, although that same identifier is called PID in userspace), to new threads of execution within the calling process (by using the parameter). In this latter case the new entity owns the same TGID of the calling process and consequently has also the same PID in userspace. If the executable is dynamically linked to shared libraries, a dynamic linker (for ELF objects, it is typically ) is used to find and load the needed objects, prepare the program to run and then run it. The Native POSIX Thread Library, simply known as the NPTL, provides the standard POSIX threads interface (pthreads) to userspace Whenever a new thread is created using the pthread_create(3) POSIX interface, the family of system calls must also be given the address of the function that the new thread must jump to. The Linux kernel provides the (acronym for "Fast user-space mutexes") mechanisms for fast user-space locking and synchronization; the majority of the operations are performed in userspace but it may be necessary to communicate with the kernel using the system call. A very special category of threads is the so-called kernel threads. They must not be confused with the above-mentioned threads of execution of the user's processes. Kernel threads exist only in kernel space and their only purpose is to concurrently run kernel tasks. Differently, whenever an independent process is created, the syscalls return exactly to the next instruction of the same program, concurrently in parent process and in child's one (i.e., one program, two processes). Different return values (one per process) enable the program to know in which of the two processes it is currently executing. Programs need this information because the child process, a few steps after process duplication, usually invokes the system call (possibly via the family of wrapper functions in glibC) and replace the program that is currently being run by the calling process with a new program, with newly initialized stack, heap, and (initialized and uninitialized) data segments. When it is done, it results in two processes that run two different programs. Depending on the effective user id (euid), and on the effective group id (egid), a process running with user zero privileges (root, the system administrator, owns the identifier 0) can perform everything (e.g., kill all the other processes or recursively wipe out whole filesystems), instead non zero user processes cannot. divides the privileges traditionally associated with superuser into distinct units, which can be independently enabled and disabled by the parent process or dropped by the child itself. Scheduling and preemption The Linux scheduler is modular, in the sense that it enables different scheduling classes and policies. Scheduler classes are plugable scheduler algorithms that can be registered with the base scheduler code. Each class schedules different types of processes. The core code of the scheduler iterates over each class in order of priority and chooses the highest priority scheduler that has a schedulable entity of type struct sched_entity ready to run. Entities may be threads, group of threads, and even all the processes of a specific user. Linux provides both user preemption as well as full kernel preemption. Preemption reduces latency, increases responsiveness, and makes Linux more suitable for desktop and real-time applications. For normal tasks, by default, the kernel uses the Completely Fair Scheduler (CFS) class, introduced in the 2.6.23 version of the kernel. Internally this default-scheduler class is defined in a macro of a C header as SCHED_NORMAL. In other POSIX kernels, a similar policy known as SCHED_OTHER allocates CPU timeslices (i.e, it assigns absolute slices of the processor time depending on either predetermined or dynamically computed priority of each process). The Linux CFS does away with absolute timeslices and assigns a fair proportion of CPU time, as a function of parameters like the total number of runnable processes and the time they have already run; this function also takes into account a kind of weight that depends on their relative priorities (nice values). With user preemption, the kernel scheduler can replace the current process with the execution of a context switch to a different one that therefore acquires the computing resources for running (CPU, memory, and more). It makes it according to the CFS algorithm (in particular, it uses a variable called for sorting entities and then chooses the one that has the smaller vruntime, - i.e., the schedulable entity that has had the least share of CPU time), to the active scheduler policy and to the relative priorities. With kernel preemption, the kernel can preempt itself when an interrupt handler returns, when kernel tasks block, and whenever a subsystem explicitly calls the schedule() function. The kernel also contains two POSIX-compliant real-time scheduling classes named SCHED_FIFO (realtime first-in-first-out) and SCHED_RR (realtime round-robin), both of which take precedence over the default class. An additional scheduling policy known as SCHED DEADLINE, implementing the earliest deadline first algorithm (EDF), was added in kernel version 3.14, released on 30 March 2014. SCHED_DEADLINE takes precedence over all the other scheduling classes. Real-time PREEMPT_RT patches, included into the mainline Linux since version 2.6, provide a deterministic scheduler, the removal of preemption and interrupts disabling (where possible), PI Mutexes (i.e., locking primitives that avoid priority inversion), support for high precision event timers (HPET), preemptive Read-copy-update, (forced) IRQ threads, and other minor features. Concurrency and synchronization The kernel has different causes of concurrency (e.g., interrupts, bottom halves, preemption of kernel and users tasks, symmetrical multiprocessing). For protecting critical regions (sections of code that must be executed atomically), shared memory locations (like global variables and other data structures with global scope), and regions of memory that are asynchronously modifiable by hardware (e.g., having the C volatile type qualifier), Linux provides a large set of tools. They consist of atomic types (which can only be manipulated by a set of specific operators), spinlocks, semaphores, mutexes, and lockless algorithms (e.g., RCUs). Most lock-less algorithms are built on top of memory barriers for the purpose of enforcing memory ordering and prevent undesired side effects due to compiler's optimizations. PREEMPT_RT code included in mainline Linux provide RT-mutexes, a special kind of Mutex which do not disable preemption and have support for priority inheritance. Almost all locks are changed into sleeping locks when using configuration for realtime operation. Priority inheritance avoids priority inversion by granting a low-priority task which holds a contended lock the priority of a higher-priority waiter until that lock is released. Linux includes a kernel lock validator called Lockdep. Interrupts management The management of the interrupts, although it could be seen as a single job, is divided in two separate parts. This split in two is due to the different time constraints and to the synchronization needs of the tasks whose the management is composed of. The first part is made up of an asyncronous interrupt service routine that in Linux is known as the top half, while the second part is carried out by one of three types of the so-called bottom halves (softirq, tasklets, and work queues). Linux interrupts service routines can be nested (i.e., a new IRQ can trap into a high priority ISR that preempts any other lower priority ISRs). Memory management Memory management in Linux is a complex topic. First of all, the kernel is not pageable (i.e., it is always resident in physical memory and cannot be swapped to the disk). In the kernel there is no memory protection (no SIGSEGV signals, unlike in userspace), therefore memory violations lead to instability and system crashes. Linux implements virtual memory with 4 and 5-levels page tables. As said, only user memory space is always pageable. It maintains information about each page frame of RAM in apposite data structures (of type ) that are populated immediately after boots and that are kept until shutdown, regardless of them being or not associated with virtual pages. Furthermore, it classifies all page frames in zones, according to their architecture dependent constraints and intended use. For example, pages reserved for DMA operations are in ZONE_DMA, pages that are not permanently mapped to virtual addresses are in ZONE_HIGHMEM (in x86_32 architecture this zone is for physical addresses above 896 MB, while x86_64 does not need it because x86_64 can permanently map physical pages that reside in higher addresses), and all that remains (with the exception of other less used classifications) is in ZONE_NORMAL. Small chunks of memory can be dynamically allocated via the family of kmalloc() API and freed with the appropriate variant of kfree(). vmalloc() and kvfree() are used for large virtually contiguous chunks. alloc_pages() allocates the desired number of entire pages. Kernel includes SLAB, SLUB and SLOB allocators as configurable alternatives. SLUB is the newest and it is also the default allocator. It aims for simplicity and efficiency. SLUB has been made PREEMPT_RT compatible. Supported architectures While not originally designed to be portable, Linux is now one of the most widely ported operating system kernels, running on a diverse range of systems from the ARM architecture to IBM z/Architecture mainframe computers. The first port was performed on the Motorola 68000 platform. The modifications to the kernel were so fundamental that Torvalds viewed the Motorola version as a fork and a "Linux-like operating system". However, that moved Torvalds to lead a major restructure of the code to facilitate porting to more computing architectures. The first Linux that, in a single source tree, had code for more than i386 alone, supported the DEC Alpha AXP 64-bit platform. Linux runs as the main operating system on IBM's Summit; , all of the world's 500 fastest supercomputers run some operating system based on the Linux kernel, a big change from 1998 when the first Linux supercomputer got added to the list. Linux has also been ported to various handheld devices such as Apple's iPhone 3G and iPod. Supported devices In 2007, the LKDDb project has been started to build a comprehensive database of hardware and protocols known by Linux kernels. The database is built automatically by static analysis of the kernel sources. Later in 2014 the Linux Hardware project was launched to automatically collect a database of all tested hardware configurations with the help of users of various Linux distributions. Live patching Rebootless updates can even be applied to the kernel by using live patching technologies such as Ksplice, kpatch and kGraft. Minimalistic foundations for live kernel patching were merged into the Linux kernel mainline in kernel version 4.0, which was released on 12 April 2015. Those foundations, known as livepatch and based primarily on the kernel's ftrace functionality, form a common core capable of supporting hot patching by both kGraft and kpatch, by providing an application programming interface (API) for kernel modules that contain hot patches and an application binary interface (ABI) for the userspace management utilities. However, the common core included into Linux kernel 4.0 supports only the x86 architecture and does not provide any mechanisms for ensuring function-level consistency while the hot patches are applied. , there is ongoing work on porting kpatch and kGraft to the common live patching core provided by the Linux kernel mainline. Security Kernel bugs present potential security issues. For example, they may allow for privilege escalation or create denial-of-service attack vectors. Over the years, numerous bugs affecting system security were found and fixed. New features are frequently implemented to improve the kernel's security. Capabilities(7) have already been introduced in the section about the processes and threads. Android makes use of them and systemd gives administrators detailed control over the capabilities of processes. Linux offers a wealth of mechanisms to reduce kernel attack surface and improve security which are collectively known as the Linux Security Modules (LSM). They comprise the Security-Enhanced Linux (SELinux) module, whose code has been originally developed and then released to the public by the NSA, and AppArmor among others. SELinux is now actively developed and maintained on GitHub. SELinux and AppArmor provide support to access control security policies, including mandatory access control (MAC), though they profoundly differ in complexity and scope. Another security feature is the Seccomp BPF (SECure COMPuting with Berkeley Packet Filters) which works by filtering parameters and reducing the set of system calls available to user-land applications. Critics have accused kernel developers of covering up security flaws, or at least not announcing them; in 2008, Linus Torvalds responded to this with the following: Linux distributions typically release security updates to fix vulnerabilities in the Linux kernel. Many offer long-term support releases that receive security updates for a certain Linux kernel version for an extended period of time. Development Developer community The community of Linux kernel developers comprises about 5000–6000 members. According to the "2017 State of Linux Kernel Development", a study issued by the Linux Foundation, covering the commits for the releases 4.8 to 4.13, about 1500 developers were contributing from about 200-250 companies on average. The top 30 developers contributed a little more than 16% of the code. As of companies, the top contributors are Intel (13.1%) and Red Hat (7.2%), Linaro (5.6%), IBM (4.1%), the second and fifth places are held by the 'none' (8.2%) and 'unknown' (4.1%) categories. As with many large open-source software projects, developers are required to adhere to the Contributor Covenant, a code of conduct intended to address harassment of minority contributors. Additionally, to prevent offense the use of inclusive terminology within the source code is mandated. Source code management The Linux development community uses Git to manage the source code. Git users clone the latest version of Torvalds' tree with and keep it up to date using . Contributions are submitted as patches, in the form of text messages on the LKML (and often also on other mailing lists dedicated to particular subsystems). The patches must conform to a set of rules and to a formal language that, among other things, describes which lines of code are to be deleted and what others are to be added to the specified files. These patches can be automatically processed so that system administrators can apply them in order to make just some changes to the code or to incrementally upgrade to the next version. Linux is distributed also in GNU zip (gzip) and bzip2 formats. Submitting code to the kernel A developer who wants to change the Linux kernel starts with developing and testing that change. Depending on how significant the change is and how many subsystems it modifies, the change will either be submitted as a single patch or in multiple patches of source code. In case of a single subsystem that is maintained by a single maintainer, these patches are sent as e-mails to the maintainer of the subsystem with the appropriate mailing list in Cc. The maintainer and the readers of the mailing list will review the patches and provide feedback. Once the review process has finished the subsystem maintainer accepts the patches in the relevant Git kernel tree. If the changes to the Linux kernel are bug fixes that are considered important enough, a pull request for the patches will be sent to Torvalds within a few days. Otherwise, a pull request will be sent to Torvalds during the next merge window. The merge window usually lasts two weeks and starts immediately after the release of the previous kernel version. The Git kernel source tree names all developers who have contributed to the Linux kernel in the Credits directory and all subsystem maintainers are listed in Maintainers. Programming language and coding style Linux is written in a special C programming language supported by GCC, a compiler that extends in many ways the C standard, for example using inline sections of code written in the assembly language (in GCC's "AT&T-style" syntax) of the target architecture. Since 2002 all the code must adhere to the 21 rules comprising the Linux Kernel Coding Style. GNU toolchain The GNU Compiler Collection (GCC or GNU cc) is the default compiler for the mainline Linux sources and it is invoked by a utility called make. Then, the GNU Assembler (more often called GAS or GNU as) outputs the object files from the GCC generated assembly code. Finally, the GNU Linker (GNU ld) is used to produce a statically linked executable kernel file called . Both and are part of GNU Binary Utilities (binutils). The above-mentioned tools are collectively known as the GNU toolchain. Compiler compatibility GCC was for a long time the only compiler capable of correctly building Linux. In 2004, Intel claimed to have modified the kernel so that its C compiler was also capable of compiling it. There was another such reported success in 2009, with a modified 2.6.22 version. Since 2010, effort has been underway to build Linux with Clang, an alternative compiler for the C language; as of 12 April 2014, the official kernel could almost be compiled by Clang. The project dedicated to this effort is named LLVMLinux after the LLVM compiler infrastructure upon which Clang is built. LLVMLinux does not aim to fork either Linux or the LLVM, therefore it is a meta-project composed of patches that are eventually submitted to the upstream projects. By enabling Linux to be compiled by Clang, developers may benefit from shorter compilation times. In 2017, developers completed upstreaming patches to support building the Linux kernel with Clang in the 4.15 release, having backported support for X86-64 and AArch64 to the 4.4, 4.9, and 4.14 branches of the stable kernel tree. Google's Pixel 2 shipped with the first Clang built Linux kernel, though patches for Pixel (1st generation) did exist. 2018 saw ChromeOS move to building kernels with Clang by default, while Android (operating system) made Clang and LLVM's linker LLD required for kernel builds in 2019. Google moved its production kernel used throughout its datacenters to being built with Clang in 2020. Today, the ClangBuiltLinux group coordinates fixes to both Linux and LLVM to ensure compatibility, both composed of members from LLVMLinux and having upstreamed patches from LLVMLinux. Kernel debugging Bugs involving the Linux Kernel can be difficult to troubleshoot. This is because of the kernel's interaction with userspace and hardware; and also because they might be caused from a wider range of reasons compared to those of user programs. A few examples of the underlying causes are semantic errors in code, misuse of synchronization primitives, and incorrect hardware management. A report of a non-fatal bug in the kernel is called an "oops"; such deviations from correct behavior of the Linux kernel may allow continued operation with compromised reliability. A critical and fatal error is reported via the function. It prints a message and then halts the kernel. One of the most common techniques used to find out bugs in code is debugging by printing. For this purpose Linux provides an in-kernel API called which stores messages in a circular buffer. The system call is used for reading and/or clearing the kernel message ring buffer and for setting the maximum log level of the messages to be sent to the console (i.e., one of the eight parameters of , which tell the severity of the condition reported); usually it is invoked via the glibC wrapper . Kernel messages are also exported to userland through the /dev/kmsg interface (e.g., systemd-journald reads that interface and by default append the messages to ). Another fundamental technique for debugging a running kernel is tracing. The ftrace mechanism is a Linux internal tracer; it is used for monitoring and debugging Linux at runtime and it can also analyze user space latencies due to kernel misbehavior. Furthermore, ftrace allows users to trace Linux at boot-time. kprobes and kretprobes can break (like debuggers in userspace) into Linux and non-disruptively collect information. kprobes can be inserted into code at (almost) any address, while kretprobes work at function return. uprobes have similar purposes but they also have some differences in usage and implementation. With KGDB Linux can be debugged in much the same way as userspace programs. KGDB requires an additional machine that runs GDB and that is connected to the target to be debugged using a serial cable or Ethernet. Development model The Linux kernel project integrates new code on a rolling basis. Software checked into the project must work and compile without error. Each kernel subsystem is assigned a maintainer who is responsible for reviewing patches against the kernel code standards and keeps a queue of patches that can be submitted to Linus Torvalds within a merge window of several weeks. Patches are merged by Torvalds into the source code of the prior stable Linux kernel release, creating the -rc release candidate for the next stable kernel. Once the merge window is closed only fixes to the new code in the development release are accepted. The -rc development release of the kernel goes through regression tests and once it is judged to be stable by Torvalds and the kernel subsystem maintainers a new Linux kernel is released and the development process starts all over again. Developers who feel treated unfairly can report this to the Linux Foundation's Technical Advisory Board. In July 2013, the maintainer of the USB 3.0 driver Sage Sharp asked Torvalds to address the abusive commentary in the kernel development community. In 2014, Sharp backed out of Linux kernel development, saying that "The focus on technical excellence, in combination with overloaded maintainers, and people with different cultural and social norms, means that Linux kernel maintainers are often blunt, rude, or brutal to get their job done". At the linux.conf.au (LCA) conference in 2018, developers expressed the view that the culture of the community has gotten much better in the past few years. Daniel Vetter, the maintainer of the Intel drm/i915 graphics kernel driver, commented that the "rather violent language and discussion" in the kernel community has decreased or disappeared. Laurent Pinchart asked developers for feedback on their experience with the kernel community at the 2017 Embedded Linux Conference Europe. The issues brought up were discussed a few days later at the Maintainers Summit. Concerns over the lack of consistency in how maintainers responded to patches submitted by developers were echoed by Shuah Khan, the maintainer of the kernel self-test framework. Torvalds contended that there would never be consistency in the handling of patches because different kernel subsystems have, over time, adopted different development processes. Therefore, it was agreed upon that each kernel subsystem maintainer would document the rules for patch acceptance. Mainline Linux The Git tree of Linus Torvalds that contains the Linux kernel is referred to as mainline Linux. Every stable kernel release originates from the mainline tree, and is frequently published on kernel.org. Mainline Linux has only solid support for a small subset of the many devices that run Linux. Non-mainline support is provided by independent projects, such as Yocto or Linaro, but in many cases the kernel from the device vendor is needed. Using a vendor kernel likely requires a board support package. Maintaining a kernel tree outside of mainline Linux has proven to be difficult. Mainlining refers to the effort of adding support for a device to the mainline kernel, while there was formerly only support in a fork or no support at all. This usually includes adding drivers or device tree files. When this is finished, the feature or security fix is considered mainlined. Linux-like kernel The maintainer of the stable branch, Greg Kroah-Hartman, has applied the term Linux-like to downstream kernel forks by vendors that add millions of lines of code to the mainline kernel. In 2019, Google stated that they wanted to use the mainline Linux kernel in Android so the number of kernel forks would be reduced. The term Linux-like has also been applied to the Embeddable Linux Kernel Subset, which does not include the full mainline Linux kernel but a small modified subset of the code. Linux forks There are certain communities that develop kernels based on the official Linux. Some interesting bits of code from these forks (i.e., a slang term meaning "derived projects") that include Linux-libre, Compute Node Linux, INK, L4Linux, RTLinux, and User-Mode Linux (UML) have been merged into the mainline. Some operating systems developed for mobile phones initially used heavily modified versions of Linux, including Google Android, Firefox OS, HP webOS, Nokia Maemo and Jolla Sailfish OS. In 2010, the Linux community criticised Google for effectively starting its own kernel tree: Today Android uses a slightly customized Linux where changes are implemented in device drivers so that little or no change to the core kernel code is required. Android developers also submit patches to the official Linux that finally can boot the Android operating system. For example, a Nexus 7 can boot and run the mainline Linux. At a 2001 presentation at the Computer History Museum, Linus Torvalds had this to say in response to a question about distributions of Linux using precisely the same kernel sources or not: Development community conflicts There have been several notable conflicts among Linux kernel developers. Examples of such conflicts are: In July 2007, Con Kolivas announced that he would cease developing for the Linux kernel. In July 2009, Alan Cox quit his role as the TTY layer maintainer after disagreement with Linus Torvalds. In December 2010, there was a discussion between Linux SCSI maintainer James Bottomley and SCST maintainer Vladislav Bolkhovitin about which SCSI target stack should be included in the Linux kernel. This made some Linux users upset. In June 2012, Torvalds made it very clear that he did not agree with NVIDIA releasing its drivers as closed. In April 2014, Torvalds banned Kay Sievers from submitting patches to the Linux kernel for failing to deal with bugs that caused systemd to negatively interact with the kernel. In October 2014, Lennart Poettering accused Torvalds of tolerating the rough discussion style on Linux kernel related mailing lists and of being a bad role model. In March 2015, Christoph Hellwig filed a lawsuit against VMware for infringement of the copyright on the Linux kernel. Linus Torvalds made it clear that he did not agree with this and similar initiatives by calling lawyers a festering disease. In April 2021, a team from the University of Minnesota was found to be submitting "bad faith" patches to the kernel as part of their research. This resulted in the immediate reversion of all patches ever submitted by a member of the university. In addition, a warning was issued by a senior maintainer that any future patch from the university would be rejected on sight. Prominent Linux kernel developers have been aware of the importance of avoiding conflicts between developers. For a long time there was no code of conduct for kernel developers due to opposition by Linus Torvalds. However, a Linux Kernel Code of Conflict was introduced on 8 March 2015. It was replaced on 16 September 2018 by a new Code of Conduct based on the Contributor Covenant. This coincided with a public apology by Torvalds and a brief break from kernel development. On 30 November 2018, complying with the Code of Conduct, Jarkko Sakkinen of Intel sent out patches replacing instances of "fuck" appearing in source code comments with suitable versions focused on the word 'hug'. Codebase , the 5.11 release of the Linux kernel had around 30.34 million lines of code. Roughly 14% of the code is part of the "core" (arch, kernel and mm directories), while 60% is drivers. Estimated cost to redevelop The cost to redevelop the Linux kernel version 2.6.0 in a traditional proprietary development setting has been estimated to be US$612 million (€467M, £394M) in 2004 prices using the COCOMO person-month estimation model. In 2006, a study funded by the European Union put the redevelopment cost of kernel version 2.6.8 higher, at €882M ($1.14bn, £744M). This topic was revisited in October 2008 by Amanda McPherson, Brian Proffitt, and Ron Hale-Evans. Using David A. Wheeler's methodology, they estimated redevelopment of the 2.6.25 kernel now costs $1.3bn (part of a total $10.8bn to redevelop Fedora 9). Again, Garcia-Garcia and Alonso de Magdaleno from University of Oviedo (Spain) estimate that the value annually added to kernel was about €100M between 2005 and 2007 and €225M in 2008, it would cost also more than €1bn (about $1.4bn as of February 2010) to develop in the European Union. , using then-current LOC (lines of code) of a 2.6.x Linux kernel and wage numbers with David A. Wheeler's calculations it would cost approximately $3bn (about €2.2bn) to redevelop the Linux kernel as it keeps getting bigger. An updated calculation , using then-current 20,088,609 LOC (lines of code) for the 4.14.14 Linux kernel and the current US National average programmer salary of $75,506 show it would cost approximately $14,725,449,000 dollars (£11,191,341,000) to rewrite the existing code. Maintenance and long-term support The latest kernel version and older kernel versions are maintained separately. Most latest kernel releases were supervised by Linus Torvalds. Current versions are released by Greg Kroah-Hartman. The Linux kernel developer community maintains a stable kernel by applying fixes for software bugs that have been discovered during the development of the subsequent stable kernel. Therefore, www.kernel.org will always list two stable kernels. The next stable Linux kernel is now released only 8 to 12 weeks later. Therefore, the Linux kernel maintainers have designated some stable kernel releases as longterm, these long-term support Linux kernels are updated with bug fixes for two or more years. , there are six longterm Linux kernels: 5.15.23, 5.10.100, 5.4.179, 4.19.229, 4.14.266, and 4.9.301. The full list of releases is at Linux kernel version history. Relation with Linux distributions Most Linux users run a kernel supplied by their Linux distribution. Some distributions ship the "vanilla" or "stable" kernels. However, several Linux distribution vendors (such as Red Hat and Debian) maintain another set of Linux kernel branches which are integrated into their products. These are usually updated at a slower pace compared to the "vanilla" branch, and they usually include all fixes from the relevant "stable" branch, but at the same time they can also add support for drivers or features which had not been released in the "vanilla" version the distribution vendor started basing their branch from. Legal aspects Licensing terms Initially, Torvalds released Linux under a license which forbade any commercial use. This was changed in version 0.12 by a switch to the GNU General Public License version 2 (GPLv2). This license allows distribution and sale of possibly modified and unmodified versions of Linux but requires that all those copies be released under the same license and be accompanied by - or that, on request, free access is given to - the complete corresponding source code. Torvalds has described licensing Linux under the GPLv2 as the "best thing I ever did". The Linux kernel is licensed explicitly under GNU General Public License version 2 only (GPL-2.0-only) with an explicit syscall exception (Linux-syscall-note), without offering the licensee the option to choose any later version, which is a common GPL extension. Contributed code must be available under GPL-compatible license. Nevertheless, Linux begun including binary blobs, which are proprietary, in its source tree and main distribution in 1996. This led to other projects starting work to remove the proprietary blobs in order to produce a 100% libre kernel, such as gNewSense in 2006, and BLAG in 2007, the work of both of which would eventually lead to the Linux-libre project being founded, which was made into an official GNU package in 2012. There was considerable debate about how easily the license could be changed to use later GPL versions (including version 3), and whether this change is even desirable. Torvalds himself specifically indicated upon the release of version 2.4.0 that his own code is released only under version 2. However, the terms of the GPL state that if no version is specified, then any version may be used, and Alan Cox pointed out that very few other Linux contributors had specified a particular version of the GPL. In September 2006, a survey of 29 key kernel programmers indicated that 28 preferred GPLv2 to the then-current GPLv3 draft. Torvalds commented, "I think a number of outsiders... believed that I personally was just the odd man out because I've been so publicly not a huge fan of the GPLv3." This group of high-profile kernel developers, including Torvalds, Greg Kroah-Hartman and Andrew Morton, commented on mass media about their objections to the GPLv3. They referred to clauses regarding DRM/tivoization, patents, "additional restrictions" and warned a Balkanisation of the "Open Source Universe" by the GPLv3. Linus Torvalds, who decided not to adopt the GPLv3 for the Linux kernel, reiterated his criticism even years later. Loadable kernel modules It is debated whether some loadable kernel modules (LKMs) are to be considered derivative works under copyright law, and thereby whether or not they fall under the terms of the GPL. In accordance with the license rules, LKMs using only a public subset of the kernel interfaces are non-derived works, thus Linux gives system administrators the mechanisms to load out-of-tree binary objects into the kernel address space. There are some out-of-tree loadable modules that make legitimate use of the dma_buf kernel feature. GPL compliant code can certainly use it. However, a different possible use case would be Nvidia Optimus that pairs a fast GPU with an Intel integrated GPU, where the Nvidia GPU writes into the Intel framebuffer when it is active. But, Nvidia cannot use this infrastructure because it necessitates bypassing a rule that can only be used by LKMs that are also GPL. Alan Cox replied on LKML, rejecting a request from one of their engineers to remove this technical enforcement from the API. Torvalds clearly stated on the LKML that "[I] claim that binary-only kernel modules ARE derivative "by default"'". On the other hand, Torvalds has also said that "[one] gray area in particular is something like a driver that was originally written for another operating system (i.e., clearly not a derived work of Linux in origin). THAT is a gray area, and _that_ is the area where I personally believe that some modules may be considered to not be derived works simply because they weren't designed for Linux and don't depend on any special Linux behaviour". Proprietary graphics drivers, in particular, are heavily discussed. Firmware binary blobs The official kernel, that is the Linus git branch at the kernel.org repository, contains proprietary code (binary blobs) despite being released under the terms of the GNU GPLv2 (or later) license. Linux can also search filesystems to locate binary blobs, proprietary firmware, drivers, or other executable modules, then it can load and link them into kernel space. Whenever proprietary modules are loaded into Linux, the kernel marks itself as being "tainted", and therefore bug reports from tainted kernels will often be ignored by developers. When it is needed (e.g., for accessing boot devices or for speed) firmware can be built-in to the kernel, this means building the firmware into vmlinux; however this is not always a viable option for technical or legal issues (e.g., it is not permitted to do this with firmware that is non-GPL compatible, although this is quite common nonetheless). Trademark Linux is a registered trademark of Linus Torvalds in the United States, the European Union, and some other countries. A legal battle over the trademark began in 1996, when William Della Croce, a lawyer who was never involved in the development of Linux, started requesting licensing fees for the use of the word Linux. After it was proven that the word was in common use long before Della Croce's claimed first use, the trademark was awarded to Torvalds. See also Notes References Further reading External links Linux kernel documentation index Linux kernel man pages Kernel bugzilla, and regressions for each recent kernel version Kernel Newbies, a source of various kernel-related information Kernel coverage at LWN.net, an authoritative source of kernel-related information Bootlin's Elixir Cross Referencer, a Linux kernel source code cross-reference Finnish inventions Free software programmed in C Free system software Software using the GPL license Linus Torvalds Monolithic kernels Unix variants Operating systems Free and open-source software

Operating System (OS)

Red Star OS Red Star OS () is a North Korean Linux distribution, with development first starting in 1998 at the Korea Computer Center (KCC). Prior to its release, computers in North Korea typically used Red Hat Linux and Windows XP. Version 3.0 was released in the summer of 2013, but , version 1.0 continues to be more widely used. It is offered only in a Korean language edition, localized with North Korean terminology and spelling. Specifications Red Star OS features a modified Mozilla Firefox browser called Naenara ("My country" in Korean), which is used for browsing the Naenara web portal on North Korea's national intranet known as Kwangmyong. Naenara comes with two search engines. Other software includes a text editor, an office suite, an e-mail client, audio and video players, a file sharing program, and video games. Version 3, like its predecessors, runs Wine, a piece of software that allows Windows programs to be run under Linux. The operating system utilizes customized versions of KDE Software Compilation. Earlier versions had KDE 3-based desktops. Version 3.0 closely resembles Apple's macOS, whereas previous versions more closely resembled Windows XP; current North Korean leader Kim Jong-un was seen with an iMac on his desk in a 2013 photo, indicating a possible connection to the redesign. Media attention The Japan-based North Korea-affiliated newspaper Choson Sinbo interviewed two Red Star OS programmers in June 2006. English-language technology blogs, including Engadget and OSnews, as well as South Korean wire services such as Yonhap, went on to repost the content. In late 2013, Will Scott, who was visiting the Pyongyang University of Science and Technology, purchased a copy of version 3 from a KCC retailer in southern Pyongyang, and uploaded screenshots to the internet. In 2015, two German researchers speaking at the Chaos Communication Congress described the internal operation of the OS. The North Korean government wants to track the underground market of USB flash drives used to exchange foreign films, music and writing, so the system watermarks all files on portable media attached to computers. History Version 1.0 The first version appeared in 2008. It is very reminiscent of the Windows XP operating system. It featured the "Naenara" web browser, based on Mozilla Firefox, and an Office suite based on Open Office, called "Uri 2.0". Wine is also included. So far, no copies have been leaked online. The screenshots of the operating system were officially published by KCNA and discovered by South Korean news sites. Version 2.0 The development of version 2.0 began in March 2008, and was completed on 3 June 2009. Like its predecessor, it is based on the appearance of Windows XP, and was priced at 2000 North Korean won (approx. US$15). The "Naenara" internet browser is also included in this version. The browser was released on 6 August 2009, as part of the operating system, and was priced at 4000 North Korean won (approx. US$28). The operating system uses a special keyboard layout that differs greatly from the South Korean standard layout. Version 3.0 Version 3.0 was introduced on 15 April 2012, and appears heavily based on macOS operating systems of various versions. The new version supports both IPv4 and IPv6 addresses. The operating system comes pre-installed with a number of applications that monitor its users. If a user tries to disable security functions, an error message will appear on the computer, or the operating system will crash and reboot. In addition, a watermarking tool integrated into the system marks all media content with the hard drive's serial number, allowing the North Korean authorities to trace the spread of files. The system also has hidden "anti-virus" software that is capable of removing censored files that are remotely stored by the North Korean secret service. There is a user group called "administrator" in the operating system. Users do not have root access by default, but are able to elevate their privileges to root by running a built-in utility called "rootsetting". However, provisions are made in kernel modules to deny even root users access to certain files, and extensive system integrity checks are done at boot time to ensure these files have not been modified. Red Star OS 3 comes with a customized version of OpenOffice called Sogwang Office. Version 4.0 Very little information is available on version 4.0. As of late 2017 it is known that a Red Star 4.0 exists and is being field tested. According to The Pyongyang Times, an official version of Red Star OS 4.0 has been developed as of January 2019, with full network support as well as system and service management tools. In June and July 2020, South Korea's NKEconomy (NK경제) obtained Red Star 4.0 and published articles about it. Vulnerabilities In 2016, the computer security company Hacker House found a security vulnerability in the integrated web browser Naenara. This vulnerability makes it possible to execute commands on the computer if the user clicks on a crafted link. References External links "Download" redstar-tools: A tool used for analyzing the system. Information technology in North Korea KDE Korean-language computing State-sponsored Linux distributions Linux distributions

Operating System (OS)

Pilot (operating system) Pilot is a single-user, multitasking operating system designed by Xerox PARC in early 1977. Pilot was written in the Mesa programming language, totalling about 24,000 lines of code. Overview Pilot was designed as a single user system in a highly networked environment of other Pilot systems, with interfaces designed for inter-process communication (IPC) across the network via the Pilot stream interface. Pilot combined virtual memory and file storage into one subsystem, and used the manager/kernel architecture for managing the system and its resources. Its designers considered a non-preemptive multitasking model, but later chose a preemptive (run until blocked) system based on monitors. Pilot included a debugger, Co-Pilot, that could debug a frozen snapshot of the operating system, written to disk. A typical Pilot workstation ran 3 operating systems at once on 3 different disk volumes : Co-Co-Pilot (a backup debugger in case the main operating system crashed), Co-Pilot (the main operating system, running under co-pilot and used to compile and bind programs) and an inferior copy of Pilot running in a 3rd disk volume, that could be booted to run test programs (that might crash the main development environment). The debugger was written to read and write variables for a program stored on a separate disk volume. This architecture was unique because it allowed the developer to single-step even operating system code with semaphore locks, stored on an inferior disk volume. However, as the memory and source code of the D-series Xerox processors grew, the time to checkpoint and restore the operating system (known as a "world swap") grew very high. It could take 60-120 seconds to run just one line of code in the inferior operating system environment. Eventually, a co-resident debugger was developed to take the place of Co-Pilot. Pilot was used as the operating system for the Xerox Star workstation. See also Timeline of operating systems References Further reading Horsley, T.R., and Lynch, W.C. Pilot: A software engineering case history. In Proc. 4th Int. Conf. Software Engineering, Munich, Germany, Sept. 1979, pp. 94-99. External links Pilot: An Operating System for a Personal Computer Computer-related introductions in 1981 History of human–computer interaction Proprietary operating systems Window-based operating systems Pilot 1981 software

Operating System (OS)

PikeOS PikeOS is a commercial, hard real-time operating system (RTOS) that offers a separation kernel based hypervisor with multiple logical partition types for many other operating systems (OS), each called a GuestOS, and applications. It enables users to build certifiable smart devices for the Internet of things (IoT) according to the high quality, safety and security standards of different industries. For safety and security critical real-time applications on controller-based systems without memory management unit (MMU) but with memory protection unit (MPU) PikeOS for MPU is available. Overview PikeOS combines a real-time operating system (RTOS) with a virtualization platform and Eclipse-based integrated development environment (IDE) for embedded systems. It is a commercial clone of L4 microkernel family. PikeOS has been developed for safety and security-critical applications with certification needs in the fields of aerospace, defense, automotive, transport, industrial automation, medical, network infrastructures, and consumer electronics. A key feature of PikeOS is an ability to safely execute applications with different safety and security levels concurrently on the same computing platform. This is done by strict spatial and temporal segregation of these applications via software partitions. A software partition can be seen as a container with pre-allocated privileges that can have access to memory, central processing unit (CPU) time, input/output (I/O), and a predefined list of OS services. With PikeOS, the term application refers to an executable linked against the PikeOS application programming interface (API) library and running as a process inside a partition. The nature of the PikeOS application programming interface (API) allows applications to range from simple control loops up to full paravirtualized guest operating systems like Linux or hardware virtualized guests. Software partitions are also called virtual machines (VMs), because it is possible to implement a complete guest operating system inside a partition which executes independently from other partitions and thus can address use cases with mixed criticality. PikeOS can be seen as a Type 1 hypervisor. Supported toolchain, IDE CODEO The Eclipse-based IDE CODEO supports system architects with graphical configuration tools, providing all the components that software engineers will need to develop embedded applications, as well as including comprehensive wizards to help embedded project development in a time-saving and cost-efficient way: Guided configuration Remote debugging (down to the hardware instruction level) Target monitoring Remote application software deployment Timing analysis Several dedicated graphical editing views are supporting the system integrator to always keep the overview on important aspects of the PikeOS system configuration showing partition types, scheduling, communication channels, shared memory and IO device configuration within partitions. Projects can be easily defined with the help of reusable templates and distributed to the development groups. Users can configure predefined components for their project and can also define and add other components during the development process. Key benefits Real-time operating system including type 1 hypervisor defined for highly flexible configuration Supports fast or secure booting times Supporting mixed criticality via separation kernel in one system Configuration of partitions with time and hardware resources Kernel driver and user space drivers supported Hardware independence between processor types and families Easy migration processes and high portability on single- and multi-core Developed to support certification according to multiple safety & security standards Reduced time to market via standard development and verification tools Wide range of supported GuestOS types: APIs No export restriction: European solution Certification standards Safety certification standards according to: Radio Technical Commission for Aeronautics (RTCA) – DO-178B/C International Organization for Standardization (ISO) – 26262 International Electrotechnical Commission (IEC) – 62304, 61508 EN – 50128, 50657 Security certification standards according to: Common Criteria SAR (?) Partner ecosystem SYSGO is committed to establish the technology and business partnerships that will help software engineers to achieve their goals. , SYSGO is working with about 100 partners globally. An excerpt of partners per category is mentioned below: Board vendors: Curtiss-Wright Controls Embedded Computing, Kontron, MEN or ABACO Silicon vendors: NXP, Renesas, Texas Instruments (TI), Xilinx, Infineon, NVidia or Intel Software partners: CoreAVI, wolfSSL, Aicas, AdaCore, Esterel, RTI, PrismTech, Datalight, Systerel, Imagination Technologies or RAPITA Tool partners: Lauterbach, Vector Software, Rapita, iSYSTEM Supported architectures: ARM, PowerPC, x86, or SPARC (on request) Supported GuestOS types Linux or Android (ideally SYSGO Linux distribution ELinOS) POSIX PSE51 with PSE52 extensions ARINC 653 RTEMS Java AUTOSAR Ada, including Ravenscar profile and others End-of-life overview References External links , SYSGO PikeOS Official Product Site PikeOS Product Note (PDF) PikeOS Flyer (PDF) Real-time operating systems Microkernels Virtualization software Embedded operating systems ARM operating systems Microkernel-based operating systems

Operating System (OS)

Opsware Opsware, Inc. was a software company based in Sunnyvale, California, that offered products for server and network device provisioning, configuration, and management targeted toward enterprise customers. Opsware had offices in New York City, Redmond, Washington, Cary, North Carolina, and an engineering office in Cluj, Romania. In July 2007, HP announced that it had agreed to acquire Opsware for $1.65 billion in cash ($14.25 per share). The acquisition closed on September 21, 2007. HP subsequently split into HP Inc. and Hewlett Packard Enterprise (HPE). The latter included Opsware's products and services and, in 2017, the HPE Software business group spin-merged with Micro Focus. History The company that was formerly known as Loudcloud was founded on September 9, 1999 (i.e., 9/9/99) by Marc Andreessen, Ben Horowitz, Tim Howes, and In Sik Rhee as a managed services provider. The company was one of the first to offer software as a service computing with an Infrastructure as a Service model. According to Wired, Loudcloud was one of the first vendors to talk about cloud computing and Software as a Service. In June 2000, Loudcloud raised $120 million, in what was at the time the largest second round of funding. This was shortly followed by a $100 million raise by one of its competitors, Totality Corporation (at the time known as MimEcom). After selling the operations side of the business to EDS in the summer of 2002, Loudcloud became Opsware and went to market as a technology company, offering the software that had been developed internally to support customer systems via automated server life-cycle management. In 2004, Opsware acquired asset management systems provider Tangram Enterprise Solutions, and in February 2005 acquired network device configuration management vendor Rendition Networks. In July 2006 Opsware acquired CreekPath for its Data Center Automation (DCA) product offering to add provisioning of storage components. In April 2007 Opsware acquired Seattle-based iConclude and its run-book automation software in order to integrate datacenter management from end-to-end. In July 2007, HP announced that it had agreed to acquire Opsware for $1.65 billion in cash ($14.25 per share), sixteen times revenues. It was HP's third largest acquisition at the time behind Compaq and Mercury Interactive. HP marketed Opsware products and software as a service solutions as part of the HP Software Division. In 2015, HP's Software division was spun off to become part of Hewlett-Packard Enterprise. Two years later in 2017, HP Software merged with UK-based Micro Focus in a spin-merge. All former Opsware tools are now grouped under the Micro Focus Hybrid Cloud Management suite. Products Opsware had three main systems that it marketed. The Server Automation System (SAS) was designed to provide provisioning, policy enforcement, compliance reporting, and patching of Windows, Unix and Linux servers across thousands of servers. It is now sold as HP Server Automation software. The Network Automation System (NAS) was designed to provide network device provisioning, policy enforcement, security lock-down, software management, and compliance reporting across thousands of devices from over 500 variants of device vendors, models, and OS versions. This product was also OEM'd by Cisco Systems and was called the Cisco "Network Compliance Manager" (NCM). It is now sold as HP Network Automation software. The third system marketed by Opsware was the Process Automation System (PAS), designed to provide run-book automation from former partner iConclude (who was acquired in March 2007). It is now sold as HP Operations Orchestration software. Customers Opsware customers included its now parent HP, GE, EDS (whose acquisition was completed by HP August 26, 2008, and is now called HP Enterprise Services), the Federal government of the United States and numerous Fortune 500 companies who used the software to automate their IT infrastructure. References Lawton, Christopher and Kingsbury, Kevin. "H-P Makes Move Into Data Centers", The Wall Street Journal, July 23, 2007. Accessed July 23, 2007. External links HP IT Management Web site HP Software as a Service Web site Software companies established in 1999 Companies based in Sunnyvale, California Hewlett-Packard acquisitions 1999 establishments in California

Operating System (OS)

QNX QNX ( or ) is a commercial Unix-like real-time operating system, aimed primarily at the embedded systems market. QNX was one of the first commercially successful microkernel operating systems. , it is used in a variety of devices including cars and mobile phones. The product was originally developed in the early 1980s by Canadian company Quantum Software Systems, later renamed QNX Software Systems. The company was ultimately acquired by BlackBerry Limited in 2010. Description As a microkernel-based OS, QNX is based on the idea of running most of the operating system kernel in the form of a number of small tasks, named Resource Managers. This differs from the more traditional monolithic kernel, in which the operating system kernel is one very large program composed of a huge number of parts, with special abilities. In the case of QNX, the use of a microkernel allows users (developers) to turn off any functions they do not need without having to change the OS. Instead, such services will simply not run. To demonstrate the OS's capability and relatively small size, in the late 1990s QNX released a demo image that included the POSIX-compliant QNX 4 OS, a full graphical user interface, graphical text editor, TCP/IP networking, web browser and web server that all fit on a bootable 1.44 MB floppy disk for the 386 PC. QNX Neutrino (2001) has been ported to a number of platforms and now runs on practically any modern central processing unit (CPU) family that is used in the embedded market. This includes the PowerPC, x86, MIPS, SH-4, and the closely interrelated of ARM, StrongARM, and XScale. QNX offers a license for noncommercial and academic users. The BlackBerry PlayBook tablet computer designed by BlackBerry uses a version of QNX as the primary operating system. Devices from BlackBerry running the BlackBerry 10 operating system are also based on QNX. QNX is also used in car infotainment systems with many major car makers offering variants that include an embedded QNX architecture. It is supported by popular SSL/TLS libraries such as wolfSSL. In recent years QNX has been used in automated drive or ADAS systems for automotive projects that require a functional safety certification. QNX provides this with its QNX OS for Safety product. The QNX operating system also contained a web browser known as 'Voyager'. History Gordon Bell and Dan Dodge, both students at the University of Waterloo in 1980, took a course (CS452) in real-time operating systems, in which the students constructed a basic real-time microkernel and user programs. Both were convinced there was a commercial need for such a system, and moved to the high-tech planned community Kanata, Ontario, to start Quantum Software Systems that year. In 1982, the first version of QUNIX was released for the Intel 8088 CPU. In 1984, Quantum Software Systems renamed QUNIX to QNX in an effort to avoid any trademark infringement challenges. One of the first widespread uses of the QNX real-time OS (RTOS) was in the nonembedded world when it was selected as the operating system for the Ontario education system's own computer design, the Unisys ICON. Over the years QNX was used mostly for larger projects, as its 44k kernel was too large to fit inside the one-chip computers of the era. The system garnered a reputation for reliability and became used in running machinery in many industrial applications. In the late-1980s, Quantum realized that the market was rapidly moving towards the Portable Operating System Interface (POSIX) model and decided to rewrite the kernel to be much more compatible at a low level. The result was QNX 4. During this time Patrick Hayden, while working as an intern, along with Robin Burgener (a full-time employee at the time), developed a new windowing system. This patented concept was developed into the embeddable graphical user interface (GUI) named the QNX Photon microGUI. QNX also provided a version of the X Window System. Toward the end of the 1990s, the company, then named QNX Software Systems, began work on a new version of QNX, designed from the ground up to be symmetric multiprocessing (SMP) capable, and to support all current POSIX application programming interfaces (APIs) and any new POSIX APIs that could be anticipated while still retaining the microkernel architecture. This resulted in QNX Neutrino, released in 2001. Along with the Neutrino kernel, QNX Software Systems became a founding member of the Eclipse (integrated development environment) consortium. The company released a suite of Eclipse plug-ins packaged with the Eclipse workbench in 2002, and named QNX Momentics Tool Suite. In 2004, the company announced it had been sold to Harman International Industries. Before this acquisition, QNX software was already widely used in the automotive industry for telematics systems. Since the purchase by Harman, QNX software has been designed into over 200 different automobile makes and models, in telematics systems, and in infotainment and navigation units. The QNX CAR Application Platform was running in over 20 million vehicles as of mid-2011. The company has since released several middleware products including the QNX Aviage Multimedia Suite, the QNX Aviage Acoustic Processing Suite and the QNX HMI Suite. The microkernels of Cisco Systems' IOS-XR (ultra high availability IOS, introduced 2004) and IOS Software Modularity (introduced 2006) are based on QNX. In September 2007, QNX Software Systems announced the availability of some of its source code. On April 9, 2010, Research In Motion announced they would acquire QNX Software Systems from Harman International Industries. On the same day, QNX source code access was restricted from the public and hobbyists. In September 2010, the company announced a tablet computer, the BlackBerry PlayBook, and a new operating system BlackBerry Tablet OS based on QNX to run on the tablet. On October 18, 2011, Research In Motion announced "BBX", which was later renamed BlackBerry 10, in December 2011. Blackberry 10 devices build upon the BlackBerry PlayBook QNX based operating system for touch devices, but adapt the user interface for smartphones using the Qt based Cascades Native User-Interface framework. At the Geneva Motor Show, Apple demonstrated CarPlay which provides an iOS-like user interface to head units in compatible vehicles. Once configured by the automaker, QNX can be programmed to hand off its display and some functions to an Apple CarPlay device. On December 11, 2014, Ford Motor Company stated that it would replace Microsoft Auto with QNX. In January 2017, QNX announced the upcoming release of its SDP 7.0, with support for Intel and ARM 32- and 64-bit platforms, and support for C++14. It was released in March 2017. Technology The QNX kernel, procnto, contains only CPU scheduling, interprocess communication, interrupt redirection and timers. Everything else runs as a user process, including a special process known as proc which performs process creation and memory management by operating in conjunction with the microkernel. This is made possible by two key mechanisms: subroutine-call type interprocess communication, and a boot loader which can load an image containing the kernel and any desired set of user programs and shared libraries. There are no device drivers in the kernel. The network stack is based on NetBSD code. Along with its support for its own, native, device drivers, QNX supports its legacy, io-net manager server, and the network drivers ported from NetBSD. QNX interprocess communication consists of sending a message from one process to another and waiting for a reply. This is a single operation, called MsgSend. The message is copied, by the kernel, from the address space of the sending process to that of the receiving process. If the receiving process is waiting for the message, control of the CPU is transferred at the same time, without a pass through the CPU scheduler. Thus, sending a message to another process and waiting for a reply does not result in "losing one's turn" for the CPU. This tight integration between message passing and CPU scheduling is one of the key mechanisms that makes QNX message passing broadly usable. Most Unix and Linux interprocess communication mechanisms lack this tight integration, although a user space implementation of QNX-type messaging for Linux does exist. Mishandling of this subtle issue is a primary reason for the disappointing performance of some other microkernel systems such as early versions of Mach. The recipient process need not be on the same physical machine. All I/O operations, file system operations, and network operations were meant to work through this mechanism, and the data transferred was copied during message passing. Later versions of QNX reduce the number of separate processes and integrate the network stack and other function blocks into single applications for performance reasons. Message handling is prioritized by thread priority. Since I/O requests are performed using message passing, high priority threads receive I/O service before low priority threads, an essential feature in a hard real-time system. The boot loader is the other key component of the minimal microkernel system. Because user programs can be built into the boot image, the set of device drivers and support libraries needed for startup need not be, and are not, in the kernel. Even such functions as program loading are not in the kernel, but instead are in shared user-space libraries loaded as part of the boot image. It is possible to put an entire boot image into ROM, which is used for diskless embedded systems. Neutrino supports symmetric multiprocessing and processor affinity, called bound multiprocessing (BMP) in QNX terminology. BMP is used to improve cache hitting and to ease the migration of non-SMP safe applications to multi-processor computers. Neutrino supports strict priority-preemptive scheduling and adaptive partition scheduling (APS). APS guarantees minimum CPU percentages to selected groups of threads, even though others may have higher priority. The adaptive partition scheduler is still strictly priority-preemptive when the system is underloaded. It can also be configured to run a selected set of critical threads strictly real time, even when the system is overloaded. QNX RTOS release history QNX RTOS History QNX/Neutrino release history QNX/Neutrino Microkernel history—Forked from QNX 4.24 in 1996. Transparent Distributed Processing Due to its microkernel architecture QNX is also a distributed operating system. Dan Dodge and Peter van der Veen hold based on the QNX operating system's distributed processing features known commercially as Transparent Distributed Processing. This allows the QNX kernels on separate devices to access each other's system services using effectively the same communication mechanism as is used to access local services. Forums OpenQNX is a QNX Community Portal established and run independently. An IRC channel and Newsgroups access via web is available. Diverse industries are represented by the developers on the site. Foundry27 is a web-based QNX community established by the company. It serves as a hub to QNX Neutrino development where developers can register, choose the license, and get the source code and related toolkit of the RTOS. See also Comparison of operating systems Android Auto NNG Open Handset Alliance Windows Embedded Automotive Ford Sync References Further reading External links Development for QNX phones Foundry27 QNX User Community Open source applications GUIdebook > GUIs > QNX QNX used for Canadian Nuclear Power Plants QNX demo floppy disk 1980 establishments in Ontario ARM operating systems BlackBerry Limited Computing platforms Distributed operating systems Embedded operating systems Information technology companies of Canada Lightweight Unix-like systems Microkernel-based operating systems Microkernels Mobile operating systems Proprietary operating systems Real-time operating systems Tablet operating systems Software companies established in 1980

Operating System (OS)

TSS (operating system) The IBM Time Sharing System TSS/360 is a discontinued early time-sharing operating system designed exclusively for a special model of the System/360 line of mainframes, the Model 67. Made available on a trial basis to a limited set of customers in 1967, it was never officially released as a supported product by IBM. TSS pioneered a number of novel features, some of which later appeared in more popular systems such as MVS. TSS was migrated to System/370 and 303x systems, but despite its many advances and novel capabilities, TSS failed to meet expectations and was eventually canceled. TSS/370 was used as the basis for a port of UNIX to the IBM mainframe. TSS/360 also inspired the development of the TSS-8 operating system. Novel characteristics TSS/360 was one of the first implementations of tightly-coupled symmetric multiprocessing. A pair of Model 67 mainframes shared a common physical memory space, and ran a single copy of the kernel (and application) code. An I/O operation launched by one processor could end and cause an interrupt in the other. The Model 67 used a standard 360 instruction called Test and Set to implement locks on code critical sections. It also implemented virtual memory and virtual machines using position-independent code. TSS/360 included an early implementation of a "Table Driven Scheduler" a user-configured table whose columns were parameters such as current priority, working set size, and number of timeslices used to date. The kernel would refer to this table when calculating the new priority of a thread. This later appeared in systems as diverse as Honeywell CP-V and IBM z/OS. As was standard with operating system software at the time, TSS/360 customers (such as General Motors Research Laboratories) were given full access to the entire source of the operating system code and development tools. User-developed improvements and patches were frequently incorporated into the official source code. User interface TSS provides users a command-line interface. Users interact with the command system. The command format consists of Command_Name[ operands]. The command name is one to eight characters without imbedded blanks. The operands are optional depending on the command, and must be separated from the command name by at least one blank. Multiple operands should be separated by TAB characters or commas. Command lines can be continued by typing a hyphen ("-") at the end of the line to be continued and typing the continuation at the beginning of the next line. Multiple commands can be written on a line by separating them with semicolons (";"). Comments are allowed in command lines, separated from the command with a semicolon and included in single quotes ("'"). Operands can be either positional or keyword, with the format "keyword=value". System commands are divided into seven categories: Task management – LOGON, LOGOFF, ABEND, etc. Data management – CATALOG, DDEF, DELETE, etc. Program management – LOAD, DUMP, DISPLAY, TRAP, etc. Command creation – PROCDEF, BUILTIN Message handling User profile – SYNONYM, DEFAULT, PROFILE, etc. Program product language interface – ASM (Assembler (F)), COBOL, HASM (Assembler (H)), PLI (PL/I (F)), PLIOPT (PL/I Optimizing Compiler), FTNH (FORTRAN (H)), etc. Position-independent code TSS provided an early implementation of position-independent code, the ability to have different processes run a single copy of an executable possibly mapped to a different virtual addresses in each process. Each procedure may have a read-only public CSECT, a writable private Prototype Section (PSECT) and a writable save area, typically located in the PSECT. Address constants of external procedures and entry points must be located in the PSECT, since the dynamic loader will not place a routine at the same virtual address in every process. A program that follows Type I linkage conventions is generally responsible at entry for saving its registers in the save area pointed to by register 13, retrieving the address of its PSECT from word 19 of the save area, chaining the save area to a new save area and putting the address of the new save area in register 13. A caller that follows Type I linkage conventions loads a V-constant for the routine into General Register 15 (GR15) and copies an R-constant for the routine's PSECT into the 19th word of the save area pointed to be GR13 prior to calling that routines. When the dynamic loader loads a program, it makes a copy of the PSECT and relocates the adcons to reflect the virtual addresses assigned within the current process, therefore each user of the program has a unique copy of the PSECT. The Dynamic Loader does not load program pages or resolve address constants until the first page fault. Criticism TSS/360 suffered from performance and reliability problems and lack of compatibility with OS/360, although those issues were eventually addressed. IBM attempted to develop TSS on a very aggressive schedule with a large staff of programmers to compete with Multics. By 1967, it had become evident that TSS/360 was suffering from the same kinds of delays as OS/360. In February 1968, at the time of SHARE 30, there were eighteen S/360-67 sites attempting to run TSS. During the conference, IBM announced via "blue letter" that TSS/360 was being decommitted a great blow to the time-sharing community. This decision was temporarily reversed, and TSS/360 was not officially canceled until 1971. However, TSS/360 continued to be quietly available for a time to existing TSS/360 customers, as an interim measure. After TSS/360 was canceled, IBM put its primary efforts into the Time Sharing Option (TSO), a time-sharing monitor for OS/360. Several other groups developed less ambitious, more successful time sharing systems for the S/360-67, notably CP-67 at IBM's Cambridge Scientific Center, an early virtual machine monitor which evolved into VM/370, MTS at the University of Michigan, and ORVYL at Stanford University. IBM also provided the TSS/370 PRPQ as a migration path for existing TSS/360 customers, which went through multiple releases. See also History of IBM mainframe operating systems Time-sharing system evolution History of operating systems Timeline of operating systems References Further reading Describes the origin and schedule problems of TSS. Describes the "second system syndrome" that affected TSS. External links Public domain software archive, includes TSS/370 source and binary archives TSS/360 manual archive at BitSavers.org, contains PDFs for a large number of TSS manuals from IBM IBM mainframe operating systems Time-sharing operating systems Discontinued operating systems 1967 software Computer-related introductions in 1967 Assembly language software

Operating System (OS)

System 9 System 9 or System IX may refer to: Computing IBM System z9, the mainframe line Plan 9 from Bell Labs, the operating system Mac OS 9, latest release of Classic Mac OS operating system OS-9, the Unix-like real time operating system SYSTEM POWER 9, line of power supplies by be quiet! Other STS-9 (Space Transportation System-9), the Space Shuttle mission See also Series 9 OS9 (disambiguation)

Operating System (OS)

Open-system environment reference model Open-system environment (OSE) reference model (RM) or OSE reference model (OSE/RM) is a 1990 reference model for enterprise architecture. It provides a framework for describing open system concepts and defining a lexicon of terms, that can be agreed upon generally by all interested parties. This reference model is meant as an environment model, complementary to the POSIX architecture for open systems. It offers an extensible framework that allows services, interfaces, protocols, and supporting data formats to be defined in terms of nonproprietary specifications that evolve through open (public), consensus-based forums.<ref>ACM Sigsoft (1993) 15th International Conference on Software Engineering, May 17-21, 1993. p.349</ref> This reference model served in the 1990s as a basic building block of several technical reference models and technical architectures. In 1996 this reference model was standardized in the ISO/IEC TR 14252 titled "Information technology -- Guide to the POSIX Open System Environment (OSE)". History The development of the open-system environment reference model started early 1990s by the NIST as refinement of the POSIX (Portable Operating System Interface) standard. POSIX is a standard for maintaining compatibility between operating systems, and addresses interoperation for communications, computing, and entertainment infrastructure. Its development started late 1980s by the POSIX Working Group 1003.0 of the Institute of Electrical and Electronics Engineers (IEEE). The NIST hosted workshops and conducts other support activities to assist users in addressing open systems requirements, preparing for the use of new technology, and identifying the international, national, industry and other open specifications that are available for building open systems frameworks, such as the government's applications portability profile for the open-system environment. NIST sponsors the semiannual Users' Forum on Application Portability Profile (APP) and Open System Environment (OSE) to exchange information and respond to NIST proposals regarding the evaluation and adoption of an integrated set of standards to support the APP and OSE. The quarterly Open Systems Environment Implementors' Workshop (OIW), co-sponsored by NIST and the Institute of Electrical and Electronics Engineers (IEEE) Computer Society, provides a public international technical forum for the timely development of implementation agreements based on emerging OSE standards. OSE/RM topics The open-system environment (OSE) forms an extensible framework that allows services, interfaces, protocols, and supporting data formats to be defined in terms of nonproprietary specifications that evolve through open (public), consensus-based forums. A selected suite of specifications that defines these interfaces, services, protocols, and data formats for a particular class or domain of applications is called a profile. Two types of elements are used in the model: entities consisting of the application software, application platform, and platform external environment; and interfaces including the application program interface and external environment interface. APP service areas The Application Portability Profile (APP) is an OSE profile designed for use by the U.S. Government. It covers a broad range of application software domains of interest to many Federal agencies, but it does not include every domain within the U.S. Government’s application inventory. The individual standards and specifications in the APP define data formats, interfaces, protocols, or a mix of these elements. The services defined in the APP tend to fall into broad service areas. These service areas are: Operating system services (OS) Human/computer interface services (HCI) Data management services (DM) Data interchange services (DI) Software engineering services (SWE) Graphics services (GS) Network services (NS) Each service area is defined in the following sections. The figure illustrates where each of these services areas relates to the OSE/RM. Assume that software engineering services are applicable in all areas. Each of the APP service areas addresses specific components around which interface, data format, or protocol specifications have been or will be defined. Security and management services are common to all of the service areas and pervade these areas in one or more forms. Classes of interfaces There are two classes of interfaces in the OSE reference model: the application program interface and the external environment interface: Application programming interface (API) : The API is the interface between the application software and the application platform. Its primary function is to support portability of application software. An API is categorized in accordance with the types of service accessible via that API. There are four types of API services in the OSE/RM: Human/computer interface services Information interchange services Communication services Internal system services External environment interface (EEI) : The EEI is the interface that supports information transfer between the application platform and the external environment, and between applications executing on the same platform. Consisting chiefly of protocols and supporting data formats, the EEI supports interoperability to a large extent. An EEI is categorized in accordance with the type of information transfer services provided. OSE profile A profile consists of a selected list of standards and other specifications that define a complement of services made available to applications in a specific domain. Examples of domains might include a workstation environment, an embedded process control environment, a distributed environment, a transaction processing environment, or an office automation environment, to name a few. Each of these environments has a different cross-section of service requirements that can be specified independently from the others. Each service, however, is defined in a standard form across all environments. An OSE profile is composed of a selected list of open (public), consensus-based standards and specifications that define services in the OSE/RM. Restricting a profile to a specific domain or group of domains that are of interest to an individual organization results in the definition of an organizational profile. OSE reference model entities The three classes of OSE reference model entities are described as follows: Application software : Within the context of the OSE Reference Model, the application software includes data, documentation, and training, as well as programs. Application platform : The application platform is composed of the collection of hardware and software components that provide the generic application and system services. Platform external environment : The platform external environment consists of those system elements that are external to the application software and the application platform (e.g., services provided by other platforms or peripheral devices). Types of information transfer services There are three types of information transfer services. These are transfer services to and from: Human users External data stores Other application platforms In its simplest form, the OSE/RM illustrates a straightforward user-supplier relationship: the application software is the user of services and the application platform/ external environment entities are the suppliers. The API and EEI define the services that are provided. Applications Basically, the open-system environment model is a basic building block of several technical reference models and technical architecture. A technical architecture identifies and describes the types of applications, platforms, and external entities; their interfaces; and their services; as well as the context within which the entities interoperate. A technical architecture is based on: a Technical Reference Model (TRM); and the selected standards that further describe the TRM elements (the profile). The technical architecture is the basis for selecting and implementing the infrastructure to establish the target architecture. A technical reference model can be defined as a taxonomy of services arranged according to a conceptual model, such as the Open System Environment model. The enumerated services are specific to those needed to support the technology computing style (e.g., distributed object computing) and the industry/business application needs (e.g., Human Services, financial). See also Enterprise architecture framework Federal enterprise architecture GERAM TAFIM TOGAF References Further reading Department of Defense (1996). Technical Architecture Framework for Information Management. Vol. 2, Technical Reference Model. Defense Information Systems Agency (2001). DoD Technical Reference Model, Version 2.0, April 9, 2001. Gary Fisher (1993). Application Portability Profile (APP) : The U.S. Government’s Open System Environment Profile OSE/1 Version 2.0. NIST Special Publication 500-210, June 1993. IEEE P1003.22 Draft Guide for POSIX Open Systems Environment—A Security Framework'' Reference models Enterprise modelling

Operating System (OS)

Fdisk In computing, the fdisk command-line utility provides disk-partitioning functions, preparatory to defining file systems. fdisk features in the DOS, DR FlexOS, IBM OS/2, and Microsoft Windows operating systems, and in certain ports of FreeBSD, NetBSD, OpenBSD, DragonFly BSD and macOS for compatibility reasons. In versions of the Windows NT operating-system line from Windows 2000 onwards, is replaced by a more advanced tool called diskpart. Similar utilities exist for Unix-like systems, for example, BSD disklabel. Implementations IBM PC DOS IBM introduced , Fixed Disk Setup Program version 1.00, with the March 1983 release of the IBM PC/XT, the first PC to store data on a hard disk, and the IBM Personal Computer DOS version 2.0. Version 1 could be used to create one FAT12 DOS partition, delete it, change the active partition, or display partition data. writes the master boot record, which supported up to four partitions. The other three were intended for other operating systems such as CP/M-86 and Xenix, which were expected to have their own partitioning utilities as did not support them. In August 1984, PC DOS 3.0 added FAT16 partitions to support larger hard disks more efficiently. In April 1987, PC DOS/fdisk 3.30 added support for extended partitions, which could hold up to 23 "logical drives" or volumes. IBM PC DOS 7.10 contained and utilities. Microsoft DOS and Windows The command is available in MS-DOS versions 3.2 and later. MS-DOS versions 2.0 through 3.10 included OEM specific partitioning tools, which may or may-not be called . Support for FAT16B was added with Compaq MS-DOS 3.31, and later became available with MS-DOS/PC DOS 4.0. Most DOS programs, including the program that came with the original Windows 95, are only capable of creating FAT partitions of types FAT12, FAT16 and FAT16B. A derivative of the MS-DOS was provided with Windows 95, Windows 98, and later Windows ME. Only those versions shipping with Windows 95B or later are able to manipulate FAT32 partitions. Windows 2000 and later do not use , they have the Logical Disk Manager feature, as well as . Unlike the programs for other operating systems, the programs for DOS and Windows 9x/Me not only alter data in the partition table, but will also overwrite many sectors of data in the partition itself. (However, to create an extended partition any partition editor must put extended boot records before each logical drive on the disk.) Users must be sure the correct disk/partition has been chosen before using a DOS/Windows for partitioning. The switch is undocumented but well known for repairing the master boot record. The supplied with Windows 95 does not report the correct size of a hard disk that is larger than 64 GB. An updated is available from Microsoft that corrects this. Microsoft named the replacement "263044usa8" and is Version 4.72.2811.0. Signature May 23, 2000. The original Windows 98 program size is smaller than the updated one. cannot create partitions larger than 512 GB, despite that the maximal FAT32 partition size is 2 TB. This limitation applies to all versions of supplied with Windows 95 OSR 2.1, Windows 98 and Windows ME. IBM OS/2 OS/2 shipped with two partition table managers up until version 4.0. These were the text mode fdisk and the GUI-based fdiskpm. The two have identical functionality, and can manipulate both FAT partitions and the more advanced HPFS partitions. OS/2 versions 4.5 and higher (including eComStation and ArcaOS) can use the JFS filesystem as well as FAT and HPFS, and replace with the Logical Volume Manager (LVM). DR/Novell DOS and FlexOS DR DOS 6.0 and FlexOS include an implementation of the command. ROM-DOS Datalight ROM-DOS includes an implementation. ROM-DOS was introduced in 1989 as an MS-DOS compatible operating system designed for embedded systems. ROM-DOS 7.1 added support for FAT32 and long file names. FreeDOS The implementation of in FreeDOS is free software. The FreeDOS version was developed by Brian E. Reifsnyder and is licensed under the GNU GPLv2. PTS-DOS Paragon Technology Systems PTS-DOS 2000 Pro includes an implementation. Mach and 386BSD for Mach Operating System was written by Robert Baron. It was ported to 386BSD by Julian Elischer, and the implementation is being used by FreeBSD, NetBSD and DragonFly BSD, all as of 2019, as well as the early versions of OpenBSD between 1995 and 1997 before OpenBSD 2.2. Tobias Weingartner re-wrote in 1997 before OpenBSD 2.2, which has subsequently been forked by Apple Computer, Inc in 2002, and is still used as the basis for on macOS as of 2019. For native partitions, BSD systems traditionally use BSD disklabel, and partitioning is supported only on certain architectures (for compatibility reasons) and only in addition to the BSD disklabel (which is mandatory). Linux In Linux, fdisk is a part of a standard package distributed by the Linux Kernel organization, util-linux. The original program was written by Andries E. Brouwer and A. V. Le Blanc and was later rewritten by Karel Zak and Davidlohr Bueso when they forked the util-linux package in 2006. See also List of disk partitioning software format (command) cfdisk GUID Partition Table References Further reading External links Linux Partition HOWTO. Partitioning with fdisk Linux Programmer's Manual, fdisk(8) fdisk from utils-linux-ng blkid - command-line utility to locate/print block device attributes Using the blkid Command . FreeBSD System Manager's Manual, FDISK(8) External DOS commands OS/2 commands Unix file system-related software Windows administration Disk partitioning software

Operating System (OS)

EmperorLinux EmperorLinux, Inc. is a reseller who, according to PC Magazine, "specialize in the sales of pre-configured Linux laptops for companies and individuals that want stable, easy-to use laptops". EmperorLinux was founded in 1999 by Lincoln Durey, an EE Ph.D. from Tulane University. The company's first product was the BlackPerl Linux laptop, based on a Sony VAIO 505TR with a highly modified Linux kernel. Since 1999, the company has added a range of IBM ThinkPads, Dell Latitudes, and Sharp laptops to its lineup. These laptops are available with most major Linux distributions, including Fedora, RHEL, Debian, Ubuntu, and SuSE. Significant improvements to stock Linux distributions come from the empkernel and a carefully configured /etc directory. Supported features include APM and ACPI suspend and hibernate support, CPU throttling, LCD backlight brightness control, wireless, and generally full support of the hardware under Linux. The company is privately held and based in Atlanta, Georgia, US. See also Free software References External links Linux companies Privately held companies based in Georgia (U.S. state) Companies based in Atlanta Computer companies established in 1999 1999 establishments in Georgia (U.S. state)

Operating System (OS)

OtherOS OtherOS was a feature available in early versions of the PlayStation 3 video game console that allowed user installed software, such as Linux or FreeBSD, to run on the system. The feature is not available in newer models and was removed from older models through system firmware update 3.21, released April 1, 2010. Software running in the OtherOS environment had access to 6 of the 7 Synergistic Processing Elements; Sony implemented a hypervisor restricting access from the RSX. IBM provided an introduction to programming parallel applications on the PlayStation 3. After the option to install OtherOS was removed a class action lawsuit was filed against Sony on behalf of those who wished to pursue legal remedies (see PlayStation 3 system software) but was dismissed with prejudice in 2011 by a federal judge. The judge stated: "As a legal matter, ... plaintiffs have failed to allege facts or articulate a theory on which Sony may be held liable." However, this decision was overturned in a 2014 appellate court decision finding that plaintiffs had indeed made clear and sufficiently substantial claims. Ultimately, in 2016, Sony settled with users who installed Linux or purchased a PlayStation 3 based upon the alternative OS functionality. The settlement was then rejected in February 2017 by judge Yvonne Gonzalez, citing two problems. The first was the percentage being charged by the lawyers and the second involved the hurdles faced by those eligible to collect. Sony responded in September 2017, offering members of a single proposed class up to $65. This is a change from $55 and $9 payouts for members of two separate classes in the prior proposal. History Since 2000, Sony has used the fact that the PlayStation 2 can run Linux in its marketing. They promoted the release of the PS2 Linux Kit, which included a Linux-based operating system, a USB keyboard and mouse, a VGA adapter, a PlayStation 2 Ethernet network adapter, and a 40 GB hard disk drive (HDD). The PlayStation 3 does not have Linux pre-installed. However, Sony included an option in the XMB menu soon after the PlayStation 3 launched that allowed booting into Linux from the hard drive or from a Live CD that the distributor's kernel would boot. The installation manual for the Yellow Dog Linux version for PS3 stated, "It was fully intended that you, a PS3 owner, could play games, watch movies, view photos, listen to music, and run a full-featured Linux operating system that transforms your PS3 into a home computer." When Sony announced the upcoming release of the PS3 Slim in September 2009, they stated that it would not be supporting the OtherOS feature, without offering any explanation for this. In March 2010 Sony announced that the "Other OS" capability of the original PS3 models would be removed due to security concerns in PS3 Firmware 3.21 on April 1, 2010. Several methods of bypassing the updating and retaining the ability to sign into PSN have been discovered, most of which involve using third party DNS servers. George Hotz claims to have created custom firmware for the PS3 called 3.21OO that re-enables OtherOS and has published a video of his custom firmware as proof. Despite the release of a YouTube video which apparently demonstrates the use of his custom firmware, some in the online community claim that this custom firmware was in fact a hoax. On July 14, 2010, Hotz announced that he would not bring out his custom firmware to the PlayStation 3. On April 27, 2010, a class action lawsuit was filed in California. The lawsuit claimed that the removal of the OtherOS feature was "unfair and deceptive" and a "breach of good faith". Most of the filing relates to violation of various consumer protection laws relating to the removal. Several other lawsuits were also filed and are somewhat similar in nature but are filed by other individuals. In January 2011, Sony sued Hotz and members of fail0verflow for their jailbreaking of the PS3. Charges included violating the DMCA, the CFAA, copyright law, and California's CCDAFA, and for breach of contract (related to the PlayStation Network User Agreement), tortious interference, misappropriation, and trespass. In February, 2011, U.S. District Judge Richard Seeborg dismissed most of the class claims with leave to amend, finding the plaintiffs failed to state a claim. Seeborg stated: "While it cannot be concluded as a matter of law at this juncture that Sony could, without legal consequence, force its customers to choose either to forego installing the software update or to lose access to the other OS feature, the present allegations of the complaint largely fail to state a claim. Accordingly, with the exception of one count, the motion to dismiss will be granted, with leave to amend." On May 4, 2011, Youness Alaoui from the PS3MFW team announced the release of a modified PS3 firmware that allows running OtherOS. On December 8, 2011, U.S. District Judge Richard Seeborg dismissed the last remaining count of the class action lawsuit, stating: "As a legal matter, ... plaintiffs have failed to allege facts or articulate a theory on which Sony may be held liable." In January 2014 the U.S. Court of Appeals for the Ninth Circuit partially reversed the dismissal and sent the case back to the district court. In 2016, Sony settled with American users who installed Linux or purchased a PlayStation 3 based upon the alternative OS functionality. This settlement provided a payment of $55 to those owners who used an alternative OS and/or $9 for purchasing a PlayStation based upon the option. The settlement was then rejected in February 2017 by judge Yvonne Gonzalez, citing two problems. The first was the percentage being charged by the lawyers and the second involved the hurdles faced by those eligible to collect. Sony responded in September 2017, offering members of a single proposed class up to $65. This is a change from $55 and $9 payouts for members of two separate classes in the prior proposal. In November 2018 final payouts for members of the class were sent in the amount of $10.07. Linux kernel Linux supported PlayStation 3 with version 2.6.21. No patches or modifications are required. A simple Linux add-on CD for the PS3 includes support for Fedora 8 and other operating systems that already claim to install natively on the PS3. However, there is currently an issue with the latest kboot boot loader provided by kernel.org. Once the user selects the default action, the USB ports are de-registered on some systems. A work-around is available at PSUbuntu. Distributions Debian, Fedora 8, Gentoo, OpenSUSE (10.3 to 11.1), and Ubuntu run on the PlayStation 3. Yellow Dog Linux for the PlayStation 3 was first released in late 2006. Ubuntu Some versions of Ubuntu up to the release 10.10 have been ported to the PS3 platform. The installer cannot run in Live mode when running in 480i or 480p video resolutions, but it offers a text-based installer that installs fully functional Ubuntu. It is possible to mount an external USB hard drive as the home folder during install. The LTS release 8.04 (Hardy Heron) of Ubuntu is incompatible with the PS3. However the 8.10 (Intrepid Ibex) release was ported to the PS3 on the same release date as the official main Ubuntu release. Yellow Dog Linux Yellow Dog Linux 5.0 was one of the first Linux distributions to run on Sony's PlayStation 3 platform. It is designed specifically for HDTV so users with SDTV will have to use the commands 'installtext' and 'ydl480i' to install and run. Yellow Dog Linux is based on the Red Hat Enterprise Linux/CentOS core and relies on the RPM package manager. Digital audio has been verified to function properly, however, the Nvidia graphics card is not supported beyond framebuffer mode. In addition, some other hardware components will not function properly without modifications to the kernel. WiFi functionality via the Network Manager is also not fully supported and must be entered manually via the Network Configuration tool, or in some cases, through the command shell. A workaround is available to enable wireless to be configured via the Network Manager. openSUSE openSUSE 10.3 was the first version of openSUSE to run on the Sony PlayStation 3 platform. openSUSE is a free version of SUSE Linux, which was then owned by Novell. There are PlayStation 3 specific installation instructions available for openSUSE. Starting with openSUSE 11.2, support for the PowerPC (and therefore the PlayStation 3) has been dropped. Fedora Fedora also ran on the PlayStation 3. Fedora 7 works on a USB external hard disk but fails to detect the internal disk, Fedora 9 detects the internal disk but not the USB disk, Fedora 8 will not work due to video "card" detection problems. Fedora 10 installs on the internal hard disk without any issues and works fine without having to change any settings. Fedora 12 only installs on the PlayStation 3 when running the 64 bit kernel. RSX Homebrew Linux on the PlayStation 3 allows for a range of homebrew programs to be developed. Although the Cell's performance is more than enough to handle most media requirements or render complex 3D graphics, it does lack the teraflops performance of a contemporary GPU's texture fetching hardware. For this reason many complex games are not possible on the PlayStation 3 through Linux, as access to hardware acceleration in the RSX is restricted by a hypervisor. There have been developments in enabling access to the RSX through the Linux kernel and the X Window System. It is possible to use the RSX memory as swap space. A trick to access some 3D functions was blocked with firmware 2.10. AsbestOS Reverse engineering advancements focused around a recently discovered USB descriptor parsing vulnerability in 3.41 firmware, which allowed running the Linux kernel on 3.41 firmware. The current state of the project is the ability to load the Linux kernel via TFTP and run it with access to all 7 SPEs (requires applying a small patch to the kernel). The rest of the system can run on an NFS share - hard disk access is currently not implemented, as well as some other features. Also, since the exploit runs the kernel with game privileges, graphics acceleration is now available, although it requires reworking of the nouveau driver code. FreeBSD Support for PlayStation 3 was added to FreeBSD 9.0 in summer 2010. This support is limited to machines with OtherOS functionality still intact (firmware version 3.15 and earlier). See also Illegal number Computer Fraud and Abuse Act PlayStation 3 cluster References External links Open Platform for Playstation 3 Overview 3.21 firmware update removing OtherOS capability How to Bypass PS3 Firmware 3.21 and Connect to PSN using an internal DNS server Linux PlayStation 3 PowerPC operating systems Game console operating systems Video game controversies

Operating System (OS)

Input/Output Control System Input/Output Control System (IOCS) is any of several packages on early IBM entry-level and mainframe computers that provided low level access to records on peripheral equipment. IOCS provides functionality similar to 1960s packages from other vendors, e.g., File Control Processor (FCP) in RCA 3301 Realcom Operating System, GEFRC in GECOS, and to the later Record Management Services (RMS) in DEC VAX/VMS (later OpenVMS.) Computers in the 1950s and 1960s typically dealt with data that were organized into records either by the nature of the media, e.g., lines of print, or by application requirements. IOCS was intended to allow Assembler language programmers to read and write records without having to worry about the details of the various devices or the blocking of logical records into physical records. IOCS provided the run time I/O support for several compilers. Computers of this era often did not have operating systems in the modern sense. Application programs called IOCS routines in a resident monitor, or included macro instructions that expanded to IOCS routines. In some cases IOCS was designed to coexist with Simultaneous Peripheral Operations On-line (SPOOL) software. The level of access is at a higher level than that provided by BIOS and BDOS in the PC world; in fact, IOCS has no support for character-oriented I/O, primarily because the systems for which it was designed didn't support it. Versions of IOCS existed for the IBM 705 III, 1401/1440/1460, 1410/7010, 7070/7072/7074, 7080 and 7040/7044/7090/7094. These systems heavily influenced the data management components of the operating systems for the System/360; the name IOCS was carried through in DOS/360 through z/VSE, with a distinction between Logical IOCS (LIOCS) and Physical IOCS (PIOCS). Although some technical details and nomenclature are different among the various IOCS packages, the fundamental concepts are the same. For concreteness, the discussion and examples in this article will mostly be in terms of 7070 IOCS. Also, multiple continuation lines will be shown as ellipses (...) when they don't serve to illustrate the narrative. Structure An IOCS program must do three things, each discussed in a subsection below. Identify required IOCS services Create control blocks for individual files Process files For the 7070 these are done using 7070 Autocoder declarative statements and macro instructions. Identify required IOCS services IOCS supported several classes of I/O equipment Disk drives Tape drives Unit record equipment. The record length was dictated by the physical media, which were Lines of print on paper Punched 80-column cards Some services offered by IOCS were not needed by all applications, e.g., checkpoints, label processing. An IOCS program must identify the particular devices types and services it uses. A 7070 IOCS program must specify one or more DIOCS statements: These declarative statements identify index registers reserved for the use of IOCS, indicate channels used, indicate whether the program is to coexist with SPOOL and provide processing options. The END DIOCS statement causes the assembly of IOCS unless a preassembled version is requested. The first (general) form is omitted when the D729 form is used. In some other IOCS packages similar functions are provided by control cards. Create control blocks for individual files An IOCS program must create a control block for each file, specifying information unique to the file. For 7070 IOCS these are entries in the File Specification Table for tape files, each of which is generated by a DTF statement, or separate control blocks generated by DDF or DUF statements. 11 22 6 56 01 DTF OUT FCHANNEL 2 ... ... DAFILE DDF IODEVICE 5 DREFMODE 4 ... ... DUF CONSFILE,1,4,CARDRDW,CARDIX,CONSEOF,CONSERR In some other IOCS packages similar functions are provided by control cards. Process files The above code defines a tape file on channel 1 called OUT, a sequential 1301/1302 disk file called DAFILE and a card file called CONSFILE. Any IOCS program must specify the actions that it wishes to perform. In 7070 IOCS this is done with processing macros. 11 22 6 56 01 OPEN CONSFILE,OUT LOOP GET CONSFILE PUT OUT B LOOP CONSEOF CLOSECONSFILE,OUT In some other IOCS packages similar functions are provided by explicit subroutine calls. See also BIOS Sharp IOCS, a similarly named system on 8-bit pocket computers by Sharp Notes References External links "RCA 3301 Realcom Training Manual", 94-06-000, November 1964 history of operating systems Operating Systems - History of Operating System Computer Hardware and System Software Concepts IBM operating systems IBM 700/7000 series IBM 1400 series IBM mainframe operating systems System software

Operating System (OS)

Symbian Symbian is a discontinued mobile operating system (OS) and computing platform designed for smartphones. Symbian was originally developed as a proprietary software OS for PDAs in 1998 by the Symbian Ltd. consortium. Symbian OS is a descendant of Psion's EPOC, and was released exclusively on ARM processors, although an unreleased x86 port existed. Symbian was used by many major mobile phone brands, like Samsung, Motorola, Sony Ericsson, and above all by Nokia. It was also prevalent in Japan by brands including Fujitsu, Sharp and Mitsubishi. As a pioneer that established the smartphone industry, it was the most popular smartphone OS on a worldwide average until the end of 2010, at a time when smartphones were in limited use, when it was overtaken by iOS and Android. It was notably less popular in North America. The Symbian OS platform is formed of two components: one being the microkernel-based operating system with its associated libraries, and the other being the user interface (as middleware), which provides the graphical shell atop the OS. The most prominent user interface was the S60 (formerly Series 60) platform built by Nokia, first released in 2002 and powering most Nokia Symbian devices. UIQ was a competing user interface mostly used by Motorola and Sony Ericsson that focused on pen-based devices, rather than a traditional keyboard interface from S60. Another interface was the MOAP(S) platform from carrier NTT DoCoMo in the Japanese market. Applications of these different interfaces were not compatible with each other, despite each being built atop Symbian OS. Nokia became the largest shareholder of Symbian Ltd. in 2004 and purchased the entire company in 2008. The non-profit Symbian Foundation was then created to make a royalty-free successor to Symbian OS. Seeking to unify the platform, S60 became the Foundation's favoured interface and UIQ stopped development. The touchscreen-focused Symbian^1 (or S60 5th Edition) was created as a result in 2009. Symbian^2 (based on MOAP) was used by NTT DoCoMo, one of the members of the Foundation, for the Japanese market. Symbian^3 was released in 2010 as the successor to S60 5th Edition, by which time it became fully free software. The transition from a proprietary operating system to a free software project is believed to be one of the largest in history. Symbian^3 received the Anna and Belle updates in 2011. The Symbian Foundation disintegrated in late 2010 and Nokia took back control of the OS development. In February 2011, Nokia, by now the only remaining company still supporting Symbian outside Japan, announced that it would use Microsoft's Windows Phone 7 as its primary smartphone platform, while Symbian would be gradually wound down. Two months later, Nokia moved the OS to proprietary licensing, only collaborating with the Japanese OEMs and later outsourced Symbian development to Accenture. Although support was promised until 2016, including two major planned updates, by 2012 Nokia had mostly abandoned development and most Symbian developers had already left Accenture, and in January 2014 Nokia stopped accepting new or changed Symbian software from developers. The Nokia 808 PureView in 2012 was officially the last Symbian smartphone from Nokia. NTT DoCoMo continued releasing OPP(S) (Operator Pack Symbian, successor of MOAP) devices in Japan, which still act as middleware on top of Symbian. Phones running this include the from Fujitsu and from Sharp in 2014. History Symbian originated from EPOC32, an operating system created by Psion in the 1990s. In June 1998, Psion Software became Symbian Ltd., a major joint venture between Psion and phone manufacturers Ericsson, Motorola, and Nokia. Afterwards, different software platforms were created for Symbian, backed by different groups of mobile phone manufacturers. They include S60 (Nokia, Samsung and LG), UIQ (Sony Ericsson and Motorola) and MOAP(S) (Japanese only such as Fujitsu, Sharp etc.). With no major competition in the smartphone OS then (Palm OS and Windows Mobile were comparatively small players), Symbian reached as high as 67% of the global smartphone market share in 2006. Despite its sizable market share then, Symbian was at various stages difficult to develop for: First (at around early-to-mid-2000s) due to the complexity of then the only native programming languages Open Programming Language (OPL) and Symbian C++, and of the OS; then the stubborn developer bureaucracy, along with high prices of various integrated development environments (IDEs) and software development kits (SDKs), which were prohibitive for independent or very small developers; and then the subsequent fragmentation, which was in part caused by infighting among and within manufacturers, each of which also had their own IDEs and SDKs. All of this discouraged third-party developers, and served to cause the native app ecosystem for Symbian not to evolve to a scale later reached by Apple's App Store or Android's Google Play. By contrast, iPhone OS (renamed iOS in 2010) and Android had comparatively simpler design, provided easier and much more centralized infrastructure to create and obtain third-party apps, offered certain developer tools and programming languages with a manageable level of complexity, and having abilities such as multitasking and graphics to meet future consumer demands. Although Symbian was difficult to program for, this issue could be worked around by creating Java Mobile Edition apps, ostensibly under a "write once, run anywhere" slogan. This wasn't always the case because of fragmentation due to different device screen sizes and differences in levels of Java ME support on various devices. In June 2008, Nokia announced the acquisition of Symbian Ltd., and a new independent non-profit organization called the Symbian Foundation was established. Symbian OS and its associated user interfaces S60, UIQ, and MOAP(S) were contributed by their owners Nokia, NTT DoCoMo, Sony Ericsson, and Symbian Ltd., to the foundation with the objective of creating the Symbian platform as a royalty-free, Free software, under the Free Software Foundation (FSF) and Open Source Initiative (OSI) approved Eclipse Public License (EPL). The platform was designated as the successor to Symbian OS, following the official launch of the Symbian Foundation in April 2009. The Symbian platform was officially made available as Free software in February 2010. Nokia became the major contributor to Symbian's code, since it then possessed the development resources for both the Symbian OS core and the user interface. Since then Nokia maintained its own code repository for the platform development, regularly releasing its development to the public repository. Symbian was intended to be developed by a community led by the Symbian Foundation, which was first announced in June 2008 and which officially launched in April 2009. Its objective was to publish the source code for the entire Symbian platform under the OSI and FSF approved EPL). The code was published under EPL on 4 February 2010; Symbian Foundation reported this event to be the largest codebase moved to Free software in history. However, some important components within Symbian OS were licensed from third parties, which prevented the foundation from publishing the full source under EPL immediately; instead much of the source was published under a more restrictive Symbian Foundation License (SFL) and access to the full source code was limited to member companies only, although membership was open to any organisation. Also, the Free software Qt framework was introduced to Symbian in 2010, as the primary upgrade path to MeeGo, which was to be the next mobile operating system to replace and supplant Symbian on high-end devices; Qt was by its nature free and very convenient to develop with. Several other frameworks were deployed to the platform, among them Standard C and C++, Python, Ruby, and Adobe Flash Lite. IDEs and SDKs were developed and then released for free, and application software (app) development for Symbian picked up. In November 2010, the Symbian Foundation announced that due to changes in global economic and market conditions (and also a lack of support from members such as Samsung and Sony Ericsson), it would transition to a licensing-only organisation; Nokia announced it would take over the stewardship of the Symbian platform. Symbian Foundation would remain the trademark holder and licensing entity and would only have non-executive directors involved. With market share sliding from 39% in Q32010 to 31% in Q42010, Symbian was losing ground to iOS and Android quickly, eventually falling behind Android in Q42010. Stephen Elop was appointed the CEO of Nokia in September 2010, and on 11 February 2011, he announced a partnership with Microsoft that would see Nokia adopt Windows Phone as its primary smartphone platform, and Symbian would be gradually phased out, together with MeeGo. As a consequence, Symbian's market share fell, and application developers for Symbian dropped out rapidly. Research in June 2011 indicated that over 39% of mobile developers using Symbian at the time of publication were planning to abandon the platform. By 5 April 2011, Nokia ceased to make free any portion of the Symbian software and reduced its collaboration to a small group of preselected partners in Japan. Source code released under the original EPL remains available in third party repositories, including a full set of all public code from the project as of 7 December 2010. On 22 June 2011, Nokia made an agreement with Accenture for an outsourcing program. Accenture will provide Symbian-based software development and support services to Nokia through 2016; about 2,800 Nokia employees became Accenture employees as of October 2011. The transfer was completed on 30 September 2011. Nokia terminated its support of software development and maintenance for Symbian with effect from 1 January 2014, thereafter refusing to publish new or changed Symbian applications or content in the Nokia Store and terminating its 'Symbian Signed' program for software certification. Features User interface Symbian has had a native graphics toolkit since its inception, known as AVKON (formerly known as Series 60). S60 was designed to be manipulated by a keyboard-like interface metaphor, such as the ~15-key augmented telephone keypad, or the mini-QWERTY keyboards. AVKON-based software is binary-compatible with Symbian versions up to and including Symbian^3. Symbian^3 includes the Qt framework, which is now the recommended user interface toolkit for new applications. Qt can also be installed on older Symbian devices. Symbian^4 was planned to introduce a new GUI library framework specifically designed for a touch-based interface, known as "UI Extensions for Mobile" or UIEMO (internal project name "Orbit"), which was built on top of Qt Widget; a preview was released in January 2010, however in October 2010 Nokia announced that Orbit/UIEMO had been cancelled. Nokia later recommended that developers use Qt Quick with QML, the new high-level declarative UI and scripting framework for creating visually rich touchscreen interfaces that allowed development for both Symbian and MeeGo; it would be delivered to existing Symbian^3 devices as a Qt update. When more applications gradually feature a user interface reworked in Qt, the legacy S60 framework (AVKON) would be deprecated and no longer included with new devices at some point, thus breaking binary compatibility with older S60 applications. Browser Symbian^3 and earlier have a built-in WebKit based browser. Symbian was the first mobile platform to make use of WebKit (in June 2005). Some older Symbian models have Opera Mobile as their default browser. Nokia released a new browser with the release of Symbian Anna with improved speed and an improved user interface. Multiple language support Symbian had strong localization support enabling manufacturers and 3rd party application developers to localize Symbian based products to support global distribution. Nokia made languages available in the device, in language packs: a set of languages which cover those commonly spoken in the area where a device variant is to be sold. All language packs have in common English, or a locally relevant dialect of it. The last release, Symbian Belle, supports these 48 languages, with [dialects], and (scripts): Symbian Belle marks the introduction of Kazakh, while Korean is no longer supported. Japanese is only available on Symbian^2 devices as they are made in Japan, and on other Symbian devices Japanese is still supported with limitations. Application development From 2010, Symbian switched to using standard C++ with Qt as the main SDK, which can be used with either Qt Creator or Carbide.c++. Qt supports the older Symbian/S60 3rd (starting with Feature Pack 1, a.k.a. S60 3.1) and Symbian/S60 5th Edition (a.k.a. S60 5.01b) releases, as well as the new Symbian platform. It also supports Maemo and MeeGo, Windows, Linux and Mac OS X. Alternative application development can be done using Python (see Python for S60), Adobe Flash Lite or Java ME. Symbian OS previously used a Symbian specific C++ version, along with CodeWarrior and later Carbide.c++ integrated development environment (IDE), as the native application development environment. Web Run time (WRT) is a portable application framework that allows creating widgets on the S60 Platform; it is an extension to the S60 WebKit based browser that allows launching multiple browser instances as separate JavaScript applications. Application development Qt As of 2010, the SDK for Symbian is standard C++, using Qt. It can be used with either Qt Creator, or Carbide (the older IDE previously used for Symbian development). A phone simulator allows testing of Qt apps. Apps compiled for the simulator are compiled to native code for the development platform, rather than having to be emulated. Application development can either use C++ or QML. Symbian C++ As Symbian OS is written in C++ using Symbian Software's coding standards, it is possible to develop using Symbian C++, although it is not a standard implementation. Before the release of the Qt SDK, this was the standard development environment. There were multiple platforms based on Symbian OS that provided software development kits (SDKs) for application developers wishing to target Symbian OS devices, the main ones being UIQ and S60. Individual phone products, or families, often had SDKs or SDK extensions downloadable from the maker's website too. The SDKs contain documentation, the header files and library files needed to build Symbian OS software, and a Windows-based emulator ("WINS"). Up until Symbian OS version 8, the SDKs also included a version of the GNU Compiler Collection (GCC) compiler (a cross-compiler) needed to build software to work on the device. Symbian OS 9 and the Symbian platform use a new application binary interface (ABI) and needed a different compiler. A choice of compilers is available including a newer version of GCC (see external links below). Unfortunately, Symbian C++ programming has a steep learning curve, as Symbian C++ requires the use of special techniques such as descriptors, active objects and the cleanup stack. This can make even relatively simple programs initially harder to implement than in other environments. It is possible that the techniques, developed for the much more restricted mobile hardware and compilers of the 1990s, caused extra complexity in source code because programmers are required to concentrate on low-level details instead of more application-specific features. As of 2010, these issues are no longer the case when using standard C++, with the Qt SDK. Symbian C++ programming is commonly done with an integrated development environment (IDE). For earlier versions of Symbian OS, the commercial IDE CodeWarrior for Symbian OS was favoured. The CodeWarrior tools were replaced during 2006 by Carbide.c++, an Eclipse-based IDE developed by Nokia. Carbide.c++ is offered in four different versions: Express, Developer, Professional, and OEM, with increasing levels of capability. Fully featured software can be created and released with the Express edition, which is free. Features such as UI design, crash debugging etc. are available in the other, charged-for, editions. Microsoft Visual Studio 2003 and 2005 are also supported via the Carbide.vs plugin. Other languages Symbian devices can also be programmed using Python, Java ME, Flash Lite, Ruby, .NET, Web Runtime (WRT) Widgets and Standard C/C++. Visual Basic programmers can use NS Basic to develop apps for S60 3rd Edition and UIQ 3 devices. In the past, Visual Basic, Visual Basic .NET, and C# development for Symbian were possible through AppForge Crossfire, a plugin for Microsoft Visual Studio. On 13 March 2007 AppForge ceased operations; Oracle purchased the intellectual property, but announced that they did not plan to sell or provide support for former AppForge products. Net60, a .NET compact framework for Symbian, which is developed by redFIVElabs, is sold as a commercial product. With Net60, VB.NET, and C# (and other) source code is compiled into an intermediate language (IL) which is executed within the Symbian OS using a just-in-time compiler. (As of 18 January 2010, RedFiveLabs has ceased development of Net60 with this announcement on their landing page: "At this stage we are pursuing some options to sell the IP so that Net60 may continue to have a future.") There is also a version of a Borland IDE for Symbian OS. Symbian development is also possible on Linux and macOS using tools and methods developed by the community, partly enabled by Symbian releasing the source code for key tools. A plugin that allows development of Symbian OS applications in Apple's Xcode IDE for Mac OS X was available. Java ME applications for Symbian OS are developed using standard techniques and tools such as the Sun Java Wireless Toolkit (formerly the J2ME Wireless Toolkit). They are packaged as JAR (and possibly JAD) files. Both CLDC and CDC applications can be created with NetBeans. Other tools include SuperWaba, which can be used to build Symbian 7.0 and 7.0s programs using Java. Nokia S60 phones can also run Python scripts when the interpreter Python for S60 is installed, with a custom made API that allows for Bluetooth support and such. There is also an interactive console to allow the user to write Python scripts directly from the phone. Deployment Once developed, Symbian applications need to find a route to customers' mobile phones. They are packaged in SIS files which may be installed over-the-air, via PC connect, Bluetooth or on a memory card. An alternative is to partner with a phone manufacturer and have the software included on the phone itself. Applications must be Symbian Signed for Symbian OS 9.x to make use of certain capabilities (system capabilities, restricted capabilities and device manufacturer capabilities). Applications could be signed for free in 2010. Architecture Technology domains and packages Symbian's design is subdivided into technology domains, each of which comprises a set of software packages. Each technology domain has its own roadmap, and the Symbian Foundation has a team of technology managers who manage these technology domain roadmaps. Every package is allocated to exactly one technology domain, based on the general functional area to which the package contributes and by which it may be influenced. By grouping related packages by themes, the Symbian Foundation hopes to encourage a strong community to form around them and to generate discussion and review. The Symbian System Model illustrates the scope of each of the technology domains across the platform packages. Packages are owned and maintained by a package owner, a named individual from an organization member of the Symbian Foundation, who accepts code contributions from the wider Symbian community and is responsible for package. Symbian kernel The Symbian kernel (EKA2) supports sufficiently fast real-time response to build a single-core phone around it – that is, a phone in which a single processor core executes both the user applications and the signalling stack. The real-time kernel has a microkernel architecture containing only the minimum, most basic primitives and functionality, for maximum robustness, availability and responsiveness. It has been termed a nanokernel, because it needs an extended kernel to implement any other abstractions. It contains a scheduler, memory management and device drivers, with networking, telephony, and file system support services in the OS Services Layer or the Base Services Layer. The inclusion of device drivers means the kernel is not a true microkernel. Design Symbian features pre-emptive multitasking and memory protection, like other operating systems (especially those created for use on desktop computers). EPOC's approach to multitasking was inspired by VMS and is based on asynchronous server-based events. Symbian OS was created with three systems design principles in mind: the integrity and security of user data is paramount user time must not be wasted all resources are scarce To best follow these principles, Symbian uses a microkernel, has a request-and-callback approach to services, and maintains separation between user interface and engine. The OS is optimised for low-power battery-based devices and for read-only memory (ROM)-based systems (e.g. features like XIP and re-entrancy in shared libraries). The OS, and application software, follows an object-oriented programming design named model–view–controller (MVC). Later OS iterations diluted this approach in response to market demands, notably with the introduction of a real-time kernel and a platform security model in versions 8 and 9. There is a strong emphasis on conserving resources which is exemplified by Symbian-specific programming idioms like descriptors and a cleanup stack. Similar methods exist to conserve storage space. Further, all Symbian programming is event-based, and the central processing unit (CPU) is switched into a low power mode when applications are not directly dealing with an event. This is done via a programming idiom called active objects. Similarly the Symbian approach to threads and processes is driven by reducing overheads. Operating system The All over Model contains the following layers, from top to bottom: UI Framework Layer Application Services Layer Java ME OS Services Layer generic OS services communications services multimedia and graphics services connectivity services Base Services Layer Kernel Services & Hardware Interface Layer The Base Services Layer is the lowest level reachable by user-side operations; it includes the File Server and User Library, a Plug-In Framework which manages all plug-ins, Store, Central Repository, DBMS and cryptographic services. It also includes the Text Window Server and the Text Shell: the two basic services from which a completely functional port can be created without the need for any higher layer services. Symbian has a microkernel architecture, which means that the minimum necessary is within the kernel to maximise robustness, availability and responsiveness. It contains a scheduler, memory management and device drivers, but other services like networking, telephony and file system support are placed in the OS Services Layer or the Base Services Layer. The inclusion of device drivers means the kernel is not a true microkernel. The EKA2 real-time kernel, which has been termed a nanokernel, contains only the most basic primitives and requires an extended kernel to implement any other abstractions. Symbian is designed to emphasise compatibility with other devices, especially removable media file systems. Early development of EPOC led to adopting File Allocation Table (FAT) as the internal file system, and this remains, but an object-oriented persistence model was placed over the underlying FAT to provide a POSIX-style interface and a streaming model. The internal data formats rely on using the same APIs that create the data to run all file manipulations. This has resulted in data-dependence and associated difficulties with changes and data migration. There is a large networking and communication subsystem, which has three main servers called: ETEL (EPOC telephony), ESOCK (EPOC sockets) and C32 (responsible for serial communication). Each of these has a plug-in scheme. For example, ESOCK allows different ".PRT" protocol modules to implement various networking protocol schemes. The subsystem also contains code that supports short-range communication links, such as Bluetooth, IrDA and USB. There is also a large volume of user interface (UI) Code. Only the base classes and substructure were contained in Symbian OS, while most of the actual user interfaces were maintained by third parties. This is no longer the case. The three major UIs – S60, UIQ and MOAP – were contributed to Symbian in 2009. Symbian also contains graphics, text layout and font rendering libraries. All native Symbian C++ applications are built up from three framework classes defined by the application architecture: an application class, a document class and an application user interface class. These classes create the fundamental application behaviour. The remaining needed functions, the application view, data model and data interface, are created independently and interact solely through their APIs with the other classes. Many other things do not yet fit into this model – for example, SyncML, Java ME providing another set of APIs on top of most of the OS and multimedia. Many of these are frameworks, and vendors are expected to supply plug-ins to these frameworks from third parties (for example, Helix Player for multimedia codecs). This has the advantage that the APIs to such areas of functionality are the same on many phone models, and that vendors get a lot of flexibility. But it means that phone vendors needed to do a great deal of integration work to make a Symbian OS phone. Symbian includes a reference user-interface called "TechView." It provides a basis for starting customisation and is the environment in which much Symbian test and example code runs. It is very similar to the user interface from the Psion Series 5 personal organiser and is not used for any production phone user interface. Symbian UI variants, platforms Symbian, as it advanced to OS version 7.0, spun off into several different graphical user interfaces, each backed by a certain company or group of companies. Unlike Android OS's cosmetic GUIs, Symbian GUIs are referred to as "platforms" due to more significant modifications and integrations. Things became more complicated when applications developed for different Symbian GUI platforms were not compatible with each other, and this led to OS fragmentation. User Interfaces platforms that run on or are based on Symbian OS include: S60, Symbian, also called Series 60. It was backed mainly by Nokia. There are several editions of this platform, appearing first as S60 (1st Edition) on Nokia 7650. It was followed by S60 2nd Edition (e.g. Nokia N70), S60 3rd Edition (e.g. Nokia N73) and S60 5th Edition (which introduced touch UI e.g. Nokia N97). The name, S60, was changed to just Symbian after the formation of Symbian Foundation, and subsequently called Symbian^1, 2 and 3. Series 80 used by Nokia Communicators such as Nokia 9300i. Series 90 Touch and button based. The only phone using this platform is Nokia 7710. UIQ backed mainly by Sony Ericsson and then Motorola. It is compatible with both buttons and touch/stylus based inputs. The last major release version is UIQ3.1 in 2008, on Sony Ericsson G900. It was discontinued after the formation of Symbian Foundation, and the decision to consolidate different Symbian UI variants into one led to the adoption of S60 as the version going forward. MOAP (Mobile Oriented Applications Platform) [Japan Only] used by Fujitsu, Mitsubishi, Sony Ericsson and Sharp-developed phones for NTT DoCoMo. It uses an interface developed specifically for DoCoMo's FOMA "Freedom of Mobile Access" network brand and is based on the UI from earlier Fujitsu FOMA models. The user cannot install new C++ applications. (Japan Only) OPP [Japan Only], successor of MOAP, used on NTT DoCoMo's FOMA phone. Version comparison * Manufactured by Fujitsu † Manufactured by Sharp ▲ Software update service for Nokia Belle and Symbian (S60) phones is discontinued at the end of December 2015 Market share and competition In Q1 2004 2.4 million Symbian phones were shipped, double the number as in Q1 2003. Symbian Ltd. was particularly impressed by progress made in Japan. 3.7 million devices were shipped in Q3 2004, a growth of 201% compared to Q3 2003 and market share growing from 30.5% to 50.2%. However, in the United States it was much less popular, with a 6% market share in Q3 2004, well behind Palm OS (43%) and Windows Mobile (25%). This has been attributed to North American customers preferring wireless PDAs over smartphones, as well as Nokia's low popularity there. On 16 November 2006, the 100 millionth smartphone running the OS was shipped. As of 21 July 2009, more than 250 million devices running Symbian OS had been produced. In 2006, Symbian had 73% of the smartphone market, compared with 22.1% of the market in the second quarter of 2011. By the end of May 2006, 10 million Symbian-powered phones were sold in Japan, representing 11% of Symbian's total worldwide shipments of 89 million. By November 2007 the figure was 30 million, achieving a market share of 65% by June 2007 in the Japanese market. Symbian has lost market share over the years as the market has dramatically grown, with new competing platforms entering the market, though its sales have increased during the same timeframe. E.g., although Symbian's share of the global smartphone market dropped from 52.4% in 2008 to 47.2% in 2009, shipments of Symbian devices grew 4.8%, from 74.9 million units to 78.5 million units. From Q2 2009 to Q2 2010, shipments of Symbian devices grew 41.5%, by 8.0 million units, from 19,178,910 units to 27,129,340; compared to an increase of 9.6 million units for Android, 3.3 million units for RIM, and 3.2 million units for Apple. Prior reports on device shipments as published in February 2010 showed that the Symbian devices formed a 47.2% share of the smart mobile devices shipped in 2009, with RIM having 20.8%, Apple having 15.1% (via iOS), Microsoft having 8.8% (via Windows CE and Windows Mobile) and Android having 4.7%. In the number of "smart mobile device" sales, Symbian devices were the market leaders for 2010. Statistics showed that Symbian devices formed a 37.6% share of smart mobile devices sold, with Android having 22.7%, RIM having 16%, and Apple having 15.7% (via iOS). Some estimates indicate that the number of mobile devices shipped with the Symbian OS up to the end of Q2 2010 is 385 million. Over the course of 2009–10, Motorola, Samsung, LG, and Sony Ericsson announced their withdrawal from Symbian in favour of alternative platforms including Google's Android, Microsoft's Windows Phone. In Q2 2012, according to IDC worldwide market share has dropped to an all-time low of 4.4%. Criticism The users of Symbian in the countries with non-Latin alphabets (such as Russia, Ukraine and others) have been criticizing the complicated method of language switching for many years. For example, if a user wants to type a Latin letter, they must call the menu, click the languages item, use arrow keys to choose, for example, the English language from among many other languages, and then press the 'OK' button. After typing the Latin letter, the user must repeat the procedure to return to their native keyboard. This method slows down typing significantly. In touch-phones and QWERTY phones the procedure is slightly different but remains time-consuming. All other mobile operating systems, as well as Nokia's S40 phones, enable switching between two initially selected languages by one click or a single gesture. Early versions of the firmware for the original Nokia N97, running on Symbian^1/Series 60 5th Edition have been heavily criticized as buggy (also contributed by the low amount of RAM installed in the phone). In November 2010, Smartphone blog All About Symbian criticized the performance of Symbian's default web browser and recommended the alternative browser Opera Mobile. Nokia's Senior Vice President Jo Harlow promised an updated browser in the first quarter of 2011. There are many different versions and editions of Symbian, which led to fragmentation. Apps and software may be incompatible when installed across different versions of Symbian. Malware Symbian OS is subject to a variety of viruses, the best known of which is Cabir. Usually these send themselves from phone to phone by Bluetooth. So far, none have exploited any flaws in Symbian OS. Instead, they have all asked the user whether they want to install the software, with somewhat prominent warnings that it can't be trusted, although some rely on social engineering, often in the form of messages that come with the malware: rogue software purporting to be a utility, game, or some other application for Symbian. However, with a view that the average mobile phone user shouldn't have to worry about security, Symbian OS 9.x adopted a Unix-style capability model (permissions per process, not per object). Installed software is theoretically unable to do damaging things (such as costing the user money by sending network data) without being digitally signed – thus making it traceable. Commercial developers who can afford the cost can apply to have their software signed via the Symbian Signed program. Developers also have the option of self-signing their programs. However, the set of available features does not include access to Bluetooth, IrDA, GSM CellID, voice calls, GPS and few others. Some operators opted to disable all certificates other than the Symbian Signed certificates. Some other hostile programs are listed below, but all of them still require the input of the user to run. Drever.A is a malicious SIS file trojan that attempts to disable the automatic startup from Simworks and Kaspersky Symbian Anti-Virus applications. Locknut.B is a malicious SIS file trojan that pretends to be a patch for Symbian S60 mobile phones. When installed, it drops a binary that will crash a critical system service component. This will prevent any application from being launched in the phone. Mabir.A is basically Cabir with added MMS functionality. The two are written by the same author, and the code shares many similarities. It spreads using Bluetooth via the same routine as early variants of Cabir. As Mabir.A activates, it will search for the first phone it finds, and starts sending copies of itself to that phone. Fontal.A is an SIS file trojan that installs a corrupted file which causes the phone to fail at reboot. If the user tries to reboot the infected phone, it will be permanently stuck on the reboot screen, and cannot be used without disinfection – that is, the use of the reformat key combination which causes the phone to lose all data. Being a trojan, Fontal cannot spread by itself – the most likely way for the user to get infected would be to acquire the file from untrusted sources, and then install it to the phone, inadvertently or otherwise. A new form of malware threat to Symbian OS in the form of 'cooked firmware' was demonstrated at the International Malware Conference, Malcon, December 2010, by Indian hacker Atul Alex. Bypassing platform security Symbian OS 9.x devices can be hacked to remove the platform security introduced in OS 9.1 onwards, allowing users to execute unsigned code. This allows altering system files, and access to previously locked areas of the OS. The hack was criticised by Nokia for potentially increasing the threat posed by mobile viruses as unsigned code can be executed. Version history List of devices See also General Bada Nokia Ovi suite Nokia PC Suite, software package used to establish an interface between Nokia mobile devices and computers running Microsoft Windows operating system; not limited to Symbian Nokia Software Updater Ovi store Nokia's application store on the Internet, not limited to Symbian Development-related Accredited Symbian Developer Carbide.c++, alternative application and OS development IDE Cleanup stack P.I.P.S. Is POSIX on Symbian Python for S60, alternative application development language Qt, preferred development tool, both for the OS and applications, not limited to Symbian Qt Creator IDE Qt Quick QML, JavaScript based language MBM (file format) References Bibliography External links Symbian foundation blog (which the homepage redirects to) Symbian on Ohloh Symbian^3 EPL source Most complete Symbian Open Source archive wildducks – Beagleboard port of Symbian S^3 Symaptic – C-Make build system Symbian Mercurial Repository (Windows platform) Discontinued operating systems Discontinued software Accenture ARM operating systems Embedded operating systems History of software Microkernel-based operating systems Mobile operating systems Nokia platforms Real-time operating systems Smartphones Microkernels

Operating System (OS)

IOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone and iPod Touch; the term also included the versions running on iPads until the name iPadOS was introduced with version 13 in 2019. It is the world's second-most widely installed mobile operating system, after Android. It is the basis for three other operating systems made by Apple: iPadOS, tvOS, and watchOS. It is proprietary software, although some parts of it are open source under the Apple Public Source License and other licenses. Unveiled in 2007 for the first-generation iPhone, iOS has since been extended to support other Apple devices such as the iPod Touch (September 2007) and the iPad (introduced: January 2010; availability: April 2010.) , Apple's App Store contains more than 2.1 million iOS applications, 1 million of which are native for iPads. These mobile apps have collectively been downloaded more than 130 billion times. Major versions of iOS are released annually. The current stable version, iOS 15, was released to the public on September 20, 2021. History In 2005, when Steve Jobs began planning the iPhone, he had a choice to either "shrink the Mac, which would be an epic feat of engineering, or enlarge the iPod". Jobs favored the former approach but pitted the Macintosh and iPod teams, led by Scott Forstall and Tony Fadell, respectively, against each other in an internal competition, with Forstall winning by creating the iPhone OS. The decision enabled the success of the iPhone as a platform for third-party developers: using a well-known desktop operating system as its basis allowed the many third-party Mac developers to write software for the iPhone with minimal retraining. Forstall was also responsible for creating a software development kit for programmers to build iPhone apps, as well as an App Store within iTunes. The operating system was unveiled with the iPhone at the Macworld Conference & Expo on January 9, 2007, and released in June of that year. At the time of its unveiling in January, Steve Jobs claimed: "iPhone runs OS X" and runs "desktop class applications", but at the time of the iPhone's release, the operating system was renamed "iPhone OS". Initially, third-party native applications were not supported. Jobs' reasoning was that developers could build web applications through the Safari web browser that "would behave like native apps on the iPhone". In October 2007, Apple announced that a native Software Development Kit (SDK) was under development and that they planned to put it "in developers' hands in February". On March 6, 2008, Apple held a press event, announcing the iPhone SDK. The iOS App Store was opened on July 10, 2008, with an initial 500 applications available. This quickly grew to 3,000 in September 2008, 15,000 in January 2009, 50,000 in June 2009, 100,000 in November 2009, 250,000 in August 2010, 650,000 in July 2012, 1 million in October 2013, 2 million in June 2016, and 2.2 million in January 2017. , 1 million apps are natively compatible with the iPad tablet computer. These apps have collectively been downloaded more than 130 billion times. App intelligence firm Sensor Tower has estimated that the App Store will reach 5 million apps by the year 2020. In September 2007, Apple announced the iPod Touch, a redesigned iPod based on the iPhone form factor. On January 27, 2010, Apple introduced their much-anticipated media tablet, the iPad, featuring a larger screen than the iPhone and iPod Touch, and designed for web browsing, media consumption, and reading, and offering multi-touch interaction with multimedia formats including newspapers, e-books, photos, videos, music, word processing documents, video games, and most existing iPhone apps using a 9.7-inch screen. It also includes a mobile version of Safari for web browsing, as well as access to the App Store, iTunes Library, iBookstore, Contacts, and Notes. Content is downloadable via Wi-Fi and optional 3G service or synced through the user's computer. AT&T was initially the sole U.S. provider of 3G wireless access for the iPad. In June 2010, Apple rebranded iPhone OS as "iOS". The trademark "IOS" had been used by Cisco for over a decade for its operating system, IOS, used on its routers. To avoid any potential lawsuit, Apple licensed the "IOS" trademark from Cisco. The Apple Watch smartwatch was announced by Tim Cook on September 9, 2014, being introduced as a product with health and fitness-tracking. It was released on April 24, 2015. It uses watchOS as operative system, which is based on IOS. On November 22, 2016, a five-second video file originally named "IMG_0942.MP4" started crashing iOS on an increasing count of devices, forcing users to reboot. It gained massive popularity through social media channels and messaging services. In October 2016, Apple opened its first iOS Developer Academy in Naples inside University of Naples Federico II's new campus. The course is completely free, aimed at acquiring specific technical skills on the creation and management of applications for the Apple ecosystem platforms. At the academy there are also issues of business administration (business planning and business management with a focus on digital opportunities) and there is a path dedicated to the design of graphical interfaces. Students have the opportunity to participate in the "Enterprise Track", an in-depth training experience on the entire life cycle of an app, from design to implementation, to security, troubleshooting, data storage and cloud usage. As of 2020, the academy graduated almost a thousand students from all over the world, who have worked on 400 app ideas and have already published about 50 apps on the iOS App Store. In the 2018–2019 academic year, students from more than 30 different countries arrived. 35 of these have been selected to attend the Worldwide Developer Conference, the annual Apple Developer Conference held annually in California in early June. On June 3, 2019, iPadOS, the branded version of iOS for iPad, was announced at the 2019 WWDC; it was launched on September 25, 2019. Features Interface The iOS user interface is based upon direct manipulation, using multi-touch gestures such as swipe, tap, pinch, and reverse pinch. Interface control elements include sliders, switches, and buttons. Internal accelerometers are used by some applications to respond to shaking the device (one common result is the undo command) or rotating it in three dimensions (one common result is switching between portrait and landscape mode). Various accessibility described in functions enable users with vision and hearing disabilities to properly use iOS. iOS devices boot to the homescreen, the primary navigation and information "hub" on iOS devices, analogous to the desktop found on personal computers. iOS homescreens are typically made up of app icons and widgets; app icons launch the associated app, whereas widgets display live, auto-updating content, such as a weather forecast, the user's email inbox, or a news ticker directly on the homescreen. Along the top of the screen is a status bar, showing information about the device and its connectivity. The status bar itself contains two elements, the Control Center and the Notification Center. The Control Center can be "pulled" down from the top right of the notch, on the new iPhones, giving access to various toggles to manage the device more quickly without having to open the Settings. It is possible to manage brightness, volume, wireless connections, music player, etc. Instead, scrolling from the top left to the bottom will open the Notification Center, which in the latest versions of iOS is very similar to the lockscreen. It displays notifications in chronological order and groups them by application. From the notifications of some apps it is possible to interact directly, for example by replying a message directly from it. Notifications are sent in two modes, the important notifications that are displayed on the lock screen and signaled by a distinctive sound, accompanied by a warning banner and the app badge icon, and the secondary mode where they are displayed in the Notification Center, but they are not shown on the lock screen, nor are they indicated by warning banners, badge icons or sounds. It is possible to choose if notifications from an app can be shown on the lock screen, Notification Center, banner, or all three; whether the banner should be temporary or permanent; activate or deactivate the sound; choose whether to group by app or not and whether to show previews when locked. It is possible to turn off unwanted app notifications. Older notifications are automatically deleted after a few days. A homescreen may be made up of several pages, between which the user can swipe back and forth, one of the ways to do this is to hold down on the "dots" shown on each page and swipe left or right. To the right of the last page, the App Library lists and categorizes apps installed on the device. Apps within each category are arranged based on the frequency of their usage. In addition to a category for suggested apps, a "recent" category lists apps recently installed alongside App Clips recently accessed. Users can search for the app they want or browse them in alphabetical order. iOS also integrates seamlessly with other programming frameworks and technologies, such as Apple Pay, HomeKit, HealthKit, and ResearchKit. On iOS, the main page button is usually located at the top right. To go back in an application there is almost always a "back" button. You can go back in 4 different ways, it varies depending on the context. Press the "Back" button at the top left of the display Swipe right from the left edge of the screen (gesture) Press the "Finish" action at the top right of the screen Scroll down on the screen content The page title is practically always present and very visible, but it shrinks as the user scrolls down. Navigation destinations that cannot be contained in the bottom tab bar can: be moved to a generic "More" tab or appear as actions in the top left or top right of other destinations. Modal views are single-screen activities that are displayed by swiping into the foreground, while allowing the previous screen to peek up, retreating into the background. You can ignore them by scrolling down or tapping "Back" at the top. Full screen views are media content such as photos or videos that take up the entire screen. They disappear on scrolling down. Occasionally on iOS, important page actions appear on a lower toolbar. Action menus can be activated by any button or by attempting to perform any action. They scroll from bottom to top. On earlier iPhones with home button, screenshots can be created with the simultaneous press of the home and power buttons. In comparison to Android OS, which requires the buttons to be held down, a short press does suffice on iOS. On the more recent iPhones which lack a physical home button, screenshots are captured using the volume-down and power buttons instead. The camera application used a skeuomorphic closing camera shutter animation prior to iOS 7. Since then, it uses a simple short blackout effect. Notable additions over time include HDR photography and the option to save both normal and high dynamic range photographs simultaneously where the former prevents ghosting effects from moving objects (since iPhone 5, iOS 6), automatic HDR adjustment (iOS 7.1), "live photo" with short video bundled to each photo if enabled (iPhone 6s, iOS 9), and a digital zoom shortcut (iPhone 7 Plus, iOS 10). Some camera settings such as video resolution and frame rate are not adjustable through the camera interface itself, but are outsourced to the system settings. A new feature in iOS 13 called "context menus" shows related actions when you touch and hold an item. When the context menu is displayed, the background is blurred. To choose from a few options, a selection control is used. Selectors can appear anchored at the bottom or in line with the content (called date selectors). Date selectors take on the appearance of any other selection control, but with a column for day, month, and optionally year. Alerts appear in the center of the screen, but there are also alerts that scroll up from the bottom of the screen (called "action panels"). Destructive actions (such as eliminating any element) are colored red. The official font of iOS is San Francisco. It is designed for small text readability, and is used throughout the operating system, including third-party apps. The icons are 180x180px in size for iPhones with a larger screen, usually models over 6 inches, including iPhone 11 Pro and iPhone 8 Plus, while it's 120x120px on iPhones with smaller displays. Applications iOS devices come with preinstalled apps developed by Apple including Mail, Maps, TV, Music, FaceTime, Wallet, Health, and many more. Applications ("apps") are the most general form of application software that can be installed on iOS. They are downloaded from the official catalog of the App Store digital store, where apps are subjected to security checks before being made available to users. In June 2017, Apple updated its guidelines to specify that app developers will no longer have the ability to use custom prompts for encouraging users to leave reviews for their apps. IOS applications can also be installed directly from an IPA file provided by the software distributor, via unofficial ways. They are written using iOS Software Development Kit (SDK) and, often, combined with Xcode, using officially supported programming languages, including Swift and Objective-C. Other companies have also created tools that allow for the development of native iOS apps using their respective programming languages. Applications for iOS are mostly built using components of UIKit, a programming framework. It allows applications to have a consistent look and feel with the OS, nevertheless offering customization. Elements automatically update along with iOS updates, automatically including new interface rules. UIKit elements are very adaptable, this allows developers to design a single app that looks the same on any iOS device. In addition to defining the iOS interface, UIKit defines the functionality of the application. At first, Apple did not intend to release an SDK to developers, because they did not want third-party apps to be developed for iOS, building web apps instead. However, this technology never entered into common use, this led Apple to change its opinion, so in October 2007 the SDK for developers was announced, finally released on March 6, 2008. The SDK includes an inclusive set of development tools, including an audio mixer and an iPhone simulator. It is a free download for Mac users. It is not available for Microsoft Windows PCs. To test the application, get technical support, and distribute applications through App Store, developers are required to subscribe to the Apple Developer Program. Over the years, the Apple Store apps surpassed multiple major milestones, including 50,000, 100,000, 250,000, 500,000, 1 million, and 2 million apps. The billionth application was installed on April 24, 2009. Home screen The home screen, rendered by SpringBoard, displays application icons and a dock at the bottom where users can pin their most frequently used apps. The home screen appears whenever the user unlocks the device or presses the physical "Home" button while in another app. Before iOS 4 on the iPhone 3GS (or later), the screen's background could be customized only through jailbreaking, but can now be changed out-of-the-box. The screen has a status bar across the top to display data, such as time, battery level, and signal strength. The rest of the screen is devoted to the current application. When a passcode is set and a user switches on the device, the passcode must be entered at the Lock Screen before access to the Home screen is granted. In iPhone OS 3, Spotlight was introduced, allowing users to search media, apps, emails, contacts, messages, reminders, calendar events, and similar content. In iOS 7 and later, Spotlight is accessed by pulling down anywhere on the home screen (except for the top and bottom edges that open Notification Center and Control Center). In iOS 9, there are two ways to access Spotlight. As with iOS 7 and 8, pulling down on any homescreen will show Spotlight. However, it can also be accessed as it was in iOS 3 – 6. This endows Spotlight with Siri suggestions, which include app suggestions, contact suggestions and news. In iOS 10, Spotlight is at the top of the now-dedicated "Today" panel. Since iOS 3.2, users are able to set a background image for the Home Screen. This feature is only available on third-generation devices—iPhone 3GS, third-generation iPod touch (iOS 4.0 or newer), and all iPad models (since iOS 3.2)—or newer. iOS 7 introduced a parallax effect on the Home Screen, which shifts the device's wallpaper and icons in response to the movement of the device, creating a 3D effect and an illusion of floating icons. This effect is also visible in the tab view of Mail and Safari. Researchers found that users organize icons on their homescreens based on usage frequency and relatedness of the applications, as well as for reasons of usability and aesthetics. System font iOS originally used Helvetica as the system font. Apple switched to Helvetica Neue exclusively for the iPhone 4 and its Retina Display, and retained Helvetica as the system font for older iPhone devices on iOS 4. With iOS 7, Apple announced that they would change the system font to Helvetica Neue Light, a decision that sparked criticism for inappropriate usage of a light, thin typeface for low-resolution mobile screens. Apple eventually chose Helvetica Neue instead. The release of iOS 7 also introduced the ability to scale text or apply other forms of text accessibility changes through Settings. With iOS 9, Apple changed the font to San Francisco, an Apple-designed font aimed at maximum legibility and font consistency across its product lineup. Folders iOS 4 introduced folders, which can be created by dragging an application on top of another, and from then on, more items can be added to the folder using the same procedure. A title for the folder is automatically selected by the category of applications inside, but the name can also be edited by the user. When apps inside folders receive notification badges, the individual numbers of notifications are added up and the total number is displayed as a notification badge on the folder itself. Originally, folders on an iPhone could include up to 12 apps, while folders on iPad could include 20. With increasing display sizes on newer iPhone hardware, iOS 7 updated the folders with pages similar to the home screen layout, allowing for a significant expansion of folder functionality. Each page of a folder can contain up to nine apps, and there can be 15 pages in total, allowing for a total of 135 apps in a single folder. In iOS 9, Apple updated folder sizes for iPad hardware, allowing for 16 apps per page, still at 15 pages maximum, increasing the total to 240 apps. Notification Center Before iOS 5, notifications were delivered in a modal window and couldn't be viewed after being dismissed. In iOS 5, Apple introduced Notification Center, which allows users to view a history of notifications. The user can tap a notification to open its corresponding app, or clear it. Notifications are now delivered in banners that appear briefly at the top of the screen. If a user taps a received notification, the application that sent the notification will be opened. Users can also choose to view notifications in modal alert windows by adjusting the application's notification settings. Introduced with iOS 8, widgets are now accessible through the Notification Center, defined by 3rd parties. When an app sends a notification while closed, a red badge appears on its icon. This badge tells the user, at a glance, how many notifications that app has sent. Opening the app clears the badge. Accessibility iOS offers various accessibility features to help users with vision and hearing disabilities. One major feature, VoiceOver, provides a voice reading information on the screen, including contextual buttons, icons, links and other user interface elements, and allows the user to navigate the operating system through gestures. Any apps with default controls and developed with a UIKit framework gets VoiceOver functionality built in. One example includes holding up the iPhone to take a photo, with VoiceOver describing the photo scenery. As part of a "Made for iPhone" program, introduced with the release of iOS 7 in 2013, Apple has developed technology to use Bluetooth and a special technology protocol to let compatible third-party equipment connect with iPhones and iPads for streaming audio directly to a user's ears. Additional customization available for Made for iPhone products include battery tracking and adjustable sound settings for different environments. Apple made further efforts for accessibility for the release of iOS 10 in 2016, adding a new pronunciation editor to VoiceOver, adding a Magnifier setting to enlarge objects through the device's camera, software TTY support for deaf people to make phone calls from the iPhone, and giving tutorials and guidelines for third-party developers to incorporate proper accessibility functions into their apps. In 2012, Liat Kornowski from The Atlantic wrote that "the iPhone has turned out to be one of the most revolutionary developments since the invention of Braille", and in 2016, Steven Aquino of TechCrunch described Apple as "leading the way in assistive technology", with Sarah Herrlinger, Senior Manager for Global Accessibility Policy and Initiatives at Apple, stating that "We see accessibility as a basic human right. Building into the core of our products supports a vision of an inclusive world where opportunity and access to information are barrier-free, empowering individuals with disabilities to achieve their goals". Criticism has been aimed at iOS depending on both internet connection (either WiFi or through iTunes) and a working SIM card upon first activation. This restriction has been loosened in iOS 12, which no longer requires the latter. Multitasking Multitasking for iOS was first released in June 2010 along with the release of iOS 4. Only certain devices—iPhone 4, iPhone 3GS, and iPod Touch 3rd generation—were able to multitask. The iPad did not get multitasking until iOS 4.2.1 in that November. The implementation of multitasking in iOS has been criticized for its approach, which limits the work that applications in the background can perform to a limited function set and requires application developers to add explicit support for it. Before iOS 4, multitasking was limited to a selection of the applications Apple included on the device. Users could however "jailbreak" their device in order to unofficially multitask. Starting with iOS 4, on third-generation and newer iOS devices, multitasking is supported through seven background APIs: Background audio – application continues to run in the background as long as it is playing audio or video content Voice over IP – application is suspended when a phone call is not in progress Background location – application is notified of location changes Push notifications Local notifications – application schedules local notifications to be delivered at a predetermined time Task completion – application asks the system for extra time to complete a given task Fast app switching – application does not execute any code and may be removed from memory at any time In iOS 5, three new background APIs were introduced: Newsstand – application can download content in the background to be ready for the user External Accessory – application communicates with an external accessory and shares data at regular intervals Bluetooth Accessory – application communicates with a bluetooth accessory and shares data at regular intervals In iOS 7, Apple introduced a new multitasking feature, providing all apps with the ability to perform background updates. This feature prefers to update the user's most frequently used apps and prefers to use Wi-Fi networks over a cellular network, without markedly reducing the device's battery life. Switching applications In iOS 4.0 to iOS 6.x, double-clicking the home button activates the application switcher. A scrollable dock-style interface appears from the bottom, moving the contents of the screen up. Choosing an icon switches to an application. To the far left are icons which function as music controls, a rotation lock, and on iOS 4.2 and above, a volume controller. With the introduction of iOS 7, double-clicking the home button also activates the application switcher. However, unlike previous versions it displays screenshots of open applications on top of the icon and horizontal scrolling allows for browsing through previous apps, and it is possible to close applications by dragging them up, similar to how WebOS handled multiple cards. With the introduction of iOS 9, the application switcher received a significant visual change; while still retaining the card metaphor introduced in iOS 7, the application icon is smaller, and appears above the screenshot (which is now larger, due to the removal of "Recent and Favorite Contacts"), and each application "card" overlaps the other, forming a rolodex effect as the user scrolls. Now, instead of the home screen appearing at the leftmost of the application switcher, it appears rightmost. In iOS 11, the application switcher receives a major redesign. In the iPad, the Control Center and app switcher are combined. The app switcher in the iPad can also be accessed by swiping up from the bottom. In the iPhone, the app switcher cannot be accessed if there are no apps in the RAM. Ending tasks In iOS 4.0 to iOS 6.x, briefly holding the icons in the application switcher makes them "jiggle" (similarly to the homescreen) and allows the user to force quit the applications by tapping the red minus circle that appears at the corner of the app's icon. Clearing applications from multitasking stayed the same from iOS 4.0 through 6.1.6, the last version of iOS 6. As of iOS 7, the process has become faster and easier. In iOS 7, instead of holding the icons to close them, they are closed by simply swiping them upwards off the screen. Up to three apps can be cleared at a time compared to one in versions up to iOS 6.1.6. Task completion Task completion allows apps to continue a certain task after the app has been suspended. As of iOS 4.0, apps can request up to ten minutes to complete a task in the background. This doesn't extend to background uploads and downloads though (e.g. if a user starts a download in one application, it won't finish if they switch away from the application). Siri Siri () is an intelligent personal assistant integrated into iOS. The assistant uses voice queries and a natural language user interface to answer questions, make recommendations, and perform actions by delegating requests to a set of Internet services. The software adapts to users' individual language usages, searches, and preferences, with continuing use. Returned results are individualized. Originally released as an app for iOS in February 2010, it was acquired by Apple two months later, and then integrated into iPhone 4S at its release in October 2011. At that time, the separate app was also removed from the iOS App Store. Siri supports a wide range of user commands, including performing phone actions, checking basic information, scheduling events and reminders, handling device settings, searching the Internet, navigating areas, finding information on entertainment, and is able to engage with iOS-integrated apps. With the release of iOS 10 in 2016, Apple opened up limited third-party access to Siri, including third-party messaging apps, as well as payments, ride-sharing, and Internet calling apps. With the release of iOS 11, Apple updated Siri's voices for more clear, human voices, it now supports follow-up questions and language translation, and additional third-party actions. Game Center Game Center is an online multiplayer "social gaming network" released by Apple. It allows users to "invite friends to play a game, start a multiplayer game through matchmaking, track their achievements, and compare their high scores on a leaderboard." iOS 5 and above adds support for profile photos. Game Center was announced during an iOS 4 preview event hosted by Apple on April 8, 2010. A preview was released to registered Apple developers in August. It was released on September 8, 2010, with iOS 4.1 on iPhone 4, iPhone 3GS, and iPod Touch 2nd generation through 4th generation. Game Center made its public debut on the iPad with iOS 4.2.1. There is no support for the iPhone 3G, original iPhone and the first-generation iPod Touch (the latter two devices did not have Game Center because they did not get iOS 4). However, Game Center is unofficially available on the iPhone 3G via a hack. Hardware The main hardware platform for iOS is the ARM architecture (the ARMv7, ARMv8-A, ARMv8.2-A, ARMv8.3-A). iOS releases before iOS 7 can only be run on iOS devices with 32-bit ARM processors (ARMv6 and ARMv7-A architectures). In 2013, iOS 7 was released with full 64-bit support (which includes a native 64-bit kernel, libraries, drivers as well as all built-in applications), after Apple announced that they were switching to 64-bit ARMv8-A processors with the introduction of the Apple A7 chip. 64-bit support was also enforced for all apps in the App Store; All new apps submitted to the App Store with a deadline of February 2015, and all app updates submitted to the App Store with a deadline of June 1, 2015. iOS 11 drops support for all iOS devices with 32-bit ARM processors as well as 32-bit applications, making iOS 64-bit only. Supported locales iOS has support for many locales. Notes The iPod Touch at its launch supported English, French, German, Japanese, Dutch, Italian, Spanish, Portuguese, Danish, Finnish, Norwegian, Swedish, Korean, Simplified Chinese, Traditional Chinese, Russian, and Polish. However, most of these languages were not available in the iPhone until iPhone 2.0. As of iOS 8, users can add more than one locale to use on the device. If one language is not supported, the next one is used instead. The language on the top of the list is the primary one. While these regions are present in iOS 8, they fall back to the generic regions for the system language. This issue has been resolved in iOS 9 and later, when a default region is added. de-AT, de-CH: de en-CA, en-US: en es-ES: es es-419: es-MX fr-CH: fr iOS 9 and above improved the locale handling process, now applying a default region to those that have multiple regions. The region is not displayed in the locale name if the region is the same as the country/region setting, or if only one region is added for a language. German: German (Germany) English: English (US) Spanish: Spanish (Spain) French: French (France) Italian: Italian (Italy) Dutch: Dutch (Netherlands) Portuguese: Portuguese (Brazil) Chinese, Traditional: Chinese, Traditional (Taiwan) Dutch (Belgium) was previously shown as Flemish in iOS 9 before being fixed in iOS 10, to bring it more in line with other locales. iOS 10 and macOS Sierra were the last versions in which new locales were added for the languages supported by iOS and macOS. English (US): United States, Canada English (UK): United Kingdom, Ireland, Singapore, South Africa English (Australia): Australia, New Zealand English (India): India Chinese, Simplified: China mainland Chinese, Traditional (Taiwan): Taiwan Chinese, Traditional (Hong Kong): Hong Kong, Macau Japanese: Japan Spanish (Spain): Spain Spanish (Latin America): Latin America, Argentina, Bolivia, Chile, Colombia, Costa Rica, Dominican Republic, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Puerto Rico, Uruguay, US, Venezuela French (France): France, Belgium, Switzerland French (Canada): Canada German: Germany, Austria, Switzerland Russian: Russia Portuguese (Brazil): Brazil Portuguese (Portugal): Portugal Italian: Italy, Switzerland Korean: South Korea Turkish: Turkey Dutch: Netherlands, Belgium Arabic: Saudi Arabia Thai: Thailand Swedish: Sweden Danish: Denmark Vietnamese: Vietnam Norwegian Bokmål: Norway Polish: Poland Finnish: Finland Indonesian: Indonesia Hebrew: Israel Greek: Greece Romanian: Romania Hungarian: Hungary Czech: Czechia Catalan: Spain Slovak: Slovakia Ukrainian: Ukraine Croatian: Croatia Malay: Malaysia Hindi: India It is possible to add custom locales in the iOS Simulator by editing the AppleLanguages portion of the .GlobalPreferences.plist file for each simulator. Development The iOS SDK (Software Development Kit) allows for the development of mobile apps on iOS. While originally developing iPhone prior to its unveiling in 2007, Apple's then-CEO Steve Jobs did not intend to let third-party developers build native apps for iOS, instead directing them to make web applications for the Safari web browser. However, backlash from developers prompted the company to reconsider, with Jobs announcing in October 2007 that Apple would have a software development kit available for developers by February 2008. The SDK was released on March 6, 2008. The SDK is a free download for users of Mac personal computers. It is not available for Microsoft Windows PCs. The SDK contains sets giving developers access to various functions and services of iOS devices, such as hardware and software attributes. It also contains an iPhone simulator to mimic the look and feel of the device on the computer while developing. New versions of the SDK accompany new versions of iOS. In order to test applications, get technical support, and distribute apps through App Store, developers are required to subscribe to the Apple Developer Program. Combined with Xcode, the iOS SDK helps developers write iOS apps using officially supported programming languages, including Swift and Objective-C. Other companies have also created tools that allow for the development of native iOS apps using their respective programming languages. Update schedule Apple provides major updates to the iOS operating system annually via iTunes and since iOS 5, also over-the-air. The device checks an XML-based PLIST file on mesu.apple.com for updates. The updates are delivered in plain unencrypted ZIP files. On all recent iOS devices, iOS regularly checks on the availability of an update, and if one is available, will prompt the user to permit its automatic installation. The latest stable version is iOS 15, released on September 20, 2021. It is available for iPhone 6S and later, and the seventh-generation iPod Touch. In addition to the release of iOS 15, iPadOS 15 was released. Apple debuted iOS 15 and iPadOS 15 at its annual WWDC keynote on June 22, 2020. iPadOS 15 is available on the same devices as iOS 14. Devices supported are iPad Air 2 and later, iPad fifth-generation and later, iPad mini 4 and later and all versions of the iPad Pro. The update introduced new features such as redesigned notifications, a more informative Weather app, Focus Mode, SharePlay, Live Text, and more. Originally, iPod Touch users had to pay for system software updates. This was due to accounting rules that designated it not a "subscription device" like iPhone or Apple TV, and improvements to the device required payments. The requirement to pay to upgrade caused iPod Touch owners to stay away from updates. However, in September 2009, a change in accounting rules won tentative approval, affecting Apple's earnings and stock price, and allowing iPod Touch updates to be delivered for free. Apple has significantly extended the cycle of updates for iOS supported devices over the years. The iPhone (1st generation) and iPhone 3G only received two iOS updates, while later models had support for five, six, and seven years. XNU kernel The iOS kernel is the XNU kernel of Darwin. The original iPhone OS (1.0) up to iPhone OS 3.1.3 used Darwin 9.0.0d1. iOS 4 was based on Darwin 10. iOS 5 was based on Darwin 11. iOS 6 was based on Darwin 13. iOS 7 and iOS 8 are based on Darwin 14. iOS 9 is based on Darwin 15. iOS 10 is based on Darwin 16. iOS 11 is based on Darwin 17. iOS 12 is based on Darwin 18. iOS 13 is based on Darwin 19. In iOS 6 the kernel is subject to ASLR, similar to that of OS X Mountain Lion. This makes exploit possibilities more complex since it is not possible to know the location of kernel code. Since XNU is based on the BSD kernel, it is open source. The source is under a 3-clause BSD license for the original BSD parts, with parts added by Apple under the Apple Public Source License. The versions contained in iOS are not available; only the versions used in macOS are available. iOS does not have kernel extensions (kexts) in the file system, even if they are actually present. The kernel cache can be decompressed to show the correct kernel, along with the kexts (all packed in the __PRELINK_TEXT section) and their plists (in the __PRELINK_INFO section). The kernel cache can also be directly decompressed (if decrypted) using third-party tools. With the advent of iOS 10 betas and default plain text kernelcaches, these tools can only be used after unpacking and applying lzssdec to unpack the kernel cache to its full size. The kextstat provided by the Cydia alternative software does not work on iOS because the kextstat is based on kmod_get_info(...), which is a deprecated API in iOS 4 and Mac OS X Snow Leopard. There are other alternative software that can also dump raw XML data. On developing devices, the kernel is always stored as a statically linked cache stored in /System/Library/Caches/com.apple.kernelcaches/kernelcache which is unpacked and executed at boot. In the beginning, iOS had a kernel version usually higher than the corresponding version of macOS. Over time, the kernels of iOS and macOS have gotten closer. This is not surprising, considering that iOS introduced new features (such as the ASLR Kernel, the default freezer, and various security-strengthening features) that were first incorporated and subsequently arrived on macOS. It appears Apple is gradually merging the iOS and macOS kernels over time. The build date for each version varies slightly between processors. This is due to the fact that the builds are sequential. The latest version of the Darwin Kernel updated to iOS 13.6 is 19.6.0, dated July 27, 2020, while for iOS 14 beta 4 it is 20.0.0, dated July 27, 2020. Kernel Image The kernel image base is randomized by the boot loader (iBoot). This is done by creating random data, doing a SHA-1 hash of it and then using a byte from the SHA-1 hash for the kernel slide. The slide is calculated with this formula: base=0x01000000+(slide_byte*0x00200000) If the slide is 0, the static offset of 0x21000000 is used instead. The adjusted base is passed to the kernel in the boot arguments structure at offset 0x04, which is equivalent to gBootArgs->virtBase. Kernel Map The kernel map is used for kernel allocations of all types (kalloc(), kernel_memory_allocate(), etc.) and spans all of kernel space (0x80000000-0xFFFEFFFF). The kernel based maps are submaps of the kernel_map, for example zone_map, ipc_kernel_map, etc. The strategy is to randomize the base of the kernel_map. A random 9-bit value is generated right after kmem_init() which establishes kernel_map, is multiplied by the page size. The resulting value is used as the size for the initial kernel_map allocation. Future kernel_map (and submap) allocations are pushed forward by a random amount. The allocation is silently removed after the first garbage collection and reused. This behaviour can be overridden with the "kmapoff" boot parameter. Attacks Kext_request() allows applications to request information about kernel modules, divided into active and passive operations. Active operations (load, unload, start, stop, etc.) require root access. iOS removes the ability to load kernel extensions. Passive operations were originally (before iOS 6) unrestricted and allowed unprivileged users to query kernel module base addresses. iOS6 inadvertently removed some limitations; only the load address requests are disallowed. So attackers can use kKextRequestPredicateGetLoaded to get load addresses and mach-o header dumps. The load address and mach-o segment headers are obscured to hide the ASLR slide, but mach-o section headers are not. This reveals the virtual addresses of loaded kernel sections. This information leak has been closed with iOS 6.0.1. Versions codenames Internally, iOS identifies each version by a codename, often used internally only, normally to maintain secrecy of the project. For example, the codename for iOS 14 is Azul. Jailbreaking Since its initial release, iOS has been subject to a variety of different hacks centered around adding functionality not allowed by Apple. Prior to the 2008 debut of Apple's native iOS App Store, the primary motive for jailbreaking was to bypass Apple's purchase mechanism for installing the App Store's native applications. Apple claimed that it would not release iOS software updates designed specifically to break these tools (other than applications that perform SIM unlocking); however, with each subsequent iOS update, previously un-patched jailbreak exploits are usually patched. When a device is booting, it loads Apple's own kernel initially, so a jailbroken device must be exploited and have the kernel patched each time it is booted up. There are different types of jailbreak. An untethered jailbreak uses exploits that are powerful enough to allow the user to turn their device off and back on at will, with the device starting up completely, and the kernel will be patched without the help of a computer – in other words, it will be jailbroken even after each reboot. However, some jailbreaks are tethered. A tethered jailbreak is only able to temporarily jailbreak the device during a single boot. If the user turns the device off and then boots it back up without the help of a jailbreak tool, the device will no longer be running a patched kernel, and it may get stuck in a partially started state, such as Recovery Mode. In order for the device to start completely and with a patched kernel, it must be "re-jailbroken" with a computer (using the "boot tethered" feature of a tool) each time it is turned on. All changes to the files on the device (such as installed package files or edited system files) will persist between reboots, including changes that can only function if the device is jailbroken (such as installed package files). In more recent years, two other solutions have been created – semi-tethered and semi-untethered. A semi-tethered solution is one where the device is able to start up on its own, but it will no longer have a patched kernel, and therefore will not be able to run modified code. It will, however, still be usable for normal functions, just like stock iOS. To start with a patched kernel, the user must start the device with the help of the jailbreak tool. A semi-untethered jailbreak gives the ability to start the device on its own. On first boot, the device will not be running a patched kernel. However, rather than having to run a tool from a computer to apply the kernel patches, the user is able to re-jailbreak their device with the help of an app (usually sideloaded using Cydia Impactor) running on their device. In the case of the iOS 9.2-9.3.3 jailbreak, a Safari-based exploit was available, thereby meaning a website could be used to rejailbreak. In more detail: Each iOS device has a bootchain that tries to make sure only trusted/signed code is loaded. A device with a tethered jailbreak is able to boot up with the help of a jailbreaking tool because the tool executes exploits via USB that bypass parts of that "chain of trust", bootstrapping to a pwned (no signature check) iBSS, iBEC, or iBoot to finish the boot process. Since the arrival of Apple's native iOS App Store, and—along with it—third-party applications, the general motives for jailbreaking have changed. People jailbreak for many different reasons, including gaining filesystem access, installing custom device themes, and modifying SpringBoard. An additional motivation is that it may enable the installation of pirated apps. On some devices, jailbreaking also makes it possible to install alternative operating systems, such as Android and the Linux kernel. Primarily, users jailbreak their devices because of the limitations of iOS. Depending on the method used, the effects of jailbreaking may be permanent or temporary. In 2010, the Electronic Frontier Foundation (EFF) successfully convinced the U.S. Copyright Office to allow an exemption to the general prohibition on circumvention of copyright protection systems under the Digital Millennium Copyright Act (DMCA). The exemption allows jailbreaking of iPhones for the sole purpose of allowing legally obtained applications to be added to the iPhone. The exemption does not affect the contractual relations between Apple and an iPhone owner, for example, jailbreaking voiding the iPhone warranty; however, it is solely based on Apple's discretion on whether they will fix jailbroken devices in the event that they need to be repaired. At the same time, the Copyright Office exempted unlocking an iPhone from DMCA's anticircumvention prohibitions. Unlocking an iPhone allows the iPhone to be used with any wireless carrier using the same GSM or CDMA technology for which the particular phone model was designed to operate. Unlocking Initially most wireless carriers in the US did not allow iPhone owners to unlock it for use with other carriers. However AT&T allowed iPhone owners who have satisfied contract requirements to unlock their iPhone. Instructions to unlock the device are available from Apple, but it is ultimately the sole discretion of the carrier to authorize the device to be unlocked. This allows the use of a carrier-sourced iPhone on other networks. Modern versions of iOS and the iPhone fully support LTE across multiple carriers despite where the phone was originally purchased from. There are programs to remove SIM lock restrictions, but are not supported by Apple and most often not a permanent unlock – a soft-unlock. A software unlock is the process by which the iPhone is modified such that the baseband will accept the SIM card of any GSM carrier. This is entirely different from a jailbreak; jailbreaking one's iPhone does not unlock it. A jailbreak is, however, required for all currently public, unofficial software unlocks. The legality of software unlocking varies in each country; for example, in the US, there is a DMCA exemption for unofficial software unlocking, but the exemption is limited to devices purchased before January 26, 2013 (so software unlocks for newer devices are in a legal grey area). Digital rights management The closed and proprietary nature of iOS has garnered criticism, particularly by digital rights advocates such as the Electronic Frontier Foundation, computer engineer and activist Brewster Kahle, Internet-law specialist Jonathan Zittrain, and the Free Software Foundation who protested the iPad's introductory event and have targeted the iPad with their "Defective by Design" campaign. Competitor Microsoft, via a PR spokesman, criticized Apple's control over its platform. At issue are restrictions imposed by the design of iOS, namely digital rights management (DRM) intended to lock purchased media to Apple's platform, the development model (requiring a yearly subscription to distribute apps developed for the iOS), the centralized approval process for apps, as well as Apple's general control and lockdown of the platform itself. Particularly at issue is the ability for Apple to remotely disable or delete apps at will. Some in the tech community have expressed concern that the locked-down iOS represents a growing trend in Apple's approach to computing, particularly Apple's shift away from machines that hobbyists can "tinker with" and note the potential for such restrictions to stifle software innovation. Former Facebook developer Joe Hewitt protested against Apple's control over its hardware as a "horrible precedent" but praised iOS's sandboxing of apps. Security and privacy iOS utilizes many security features in both hardware and software. Below are summaries of the most prominent features. Secure Boot Before fully booting into iOS, there is low-level code that runs from the Boot ROM. Its task is to verify that the Low-Level Bootloader is signed by the Apple Root CA public key before running it. This process is to ensure that no malicious or otherwise unauthorized software can be run on an iOS device. After the Low-Level Bootloader finishes its tasks, it runs the higher level bootloader, known as iBoot. If all goes well, iBoot will then proceed to load the iOS kernel as well as the rest of the operating system. Secure Enclave The Secure Enclave is a coprocessor found in iOS devices part of the A7 and newer chips used for data protection, Touch ID and Face ID. The purpose of the Secure Enclave is to handle keys and other info such as biometrics that is sensitive enough to not be handled by the Application Processor (AP). It is isolated with a hardware filter so the AP cannot access it. It shares RAM with the AP, but its portion of the RAM (known as TZ0) is encrypted. The secure enclave itself is a flashable 4 MB AKF processor core called the secure enclave processor (SEP) as documented in Apple Patent Application 20130308838. The technology used is similar to ARM's TrustZone/SecurCore but contains proprietary code for Apple KF cores in general and SEP specifically. It is also responsible for generating the UID key on A9 or newer chips that protects user data at rest. It has its own secure boot process to ensure that it is completely secure. A hardware random number generator is also included as a part of this coprocessor. Each device's Secure Enclave has a unique ID that is given to it when it is made and cannot be changed. This identifier is used to create a temporary key that encrypts the memory in this portion of the system. The Secure Enclave also contains an anti-replay counter to prevent brute force attacks. The SEP is located in the devicetree under IODeviceTree:/arm-io/sep and managed by the AppleSEPManager driver. In 2020, security flaws in the SEP were discovered, causing concerns about Apple devices such as iPhones. Face ID Face ID is a face scanner that is embedded in the notch on iPhone models X, XS, XS Max, XR, 11, 11 Pro, 11 Pro Max, 12, 12 Mini, 12 Pro, and 12 Pro Max, and 13, 13 Mini, 13 Pro, and 13 Pro Max. It can be used to unlock the device, make purchases, and log into applications among other functions. When used, Face ID only temporarily stores the face data in encrypted memory in the Secure Enclave, as described below. There is no way for the device's main processor or any other part of the system to access the raw data that is obtained from the Face ID sensor. Passcode iOS devices can have a passcode that is used to unlock the device, make changes to system settings, and encrypt the device's contents. Until recently, these were typically four numerical digits long. However, since unlocking the devices with a fingerprint by using Touch ID has become more widespread, six-digit passcodes are now the default on iOS with the option to switch back to four or use an alphanumeric passcode. Touch ID Touch ID is a fingerprint scanner that is embedded in the home button and can be used to unlock the device, make purchases, and log into applications among other functions. When used, Touch ID only temporarily stores the fingerprint data in encrypted memory in the Secure Enclave, as described above. There is no way for the device's main processor or any other part of the system to access the raw fingerprint data that is obtained from the Touch ID sensor. Address Space Layout Randomization Address Space Layout Randomization (ASLR) is a low-level technique of preventing memory corruption attacks such as buffer overflows. It involves placing data in randomly selected locations in memory in order to make it more difficult to predict ways to corrupt the system and create exploits. ASLR makes app bugs more likely to crash the app than to silently overwrite memory, regardless of whether the behavior is accidental or malicious. Non-Executable Memory iOS utilizes the ARM architecture's Execute Never (XN) feature. This allows some portions of the memory to be marked as non-executable, working alongside ASLR to prevent buffer overflow attacks including return-to-libc attacks. Encryption As mentioned above, one use of encryption in iOS is in the memory of the Secure Enclave. When a passcode is utilized on an iOS device, the contents of the device are encrypted. This is done by using a hardware AES 256 implementation that is very efficient because it is placed directly between the flash storage and RAM. iOS, in combination with its specific hardware, uses crypto-shredding when erasing all content and settings by obliterating all the keys in 'effaceable storage'. This renders all user data on the device cryptographically inaccessible. Keychain The iOS keychain is a database of login information that can be shared across apps written by the same person or organization. This service is often used for storing passwords for web applications. App Security Third-party applications such as those distributed through the App Store must be code signed with an Apple-issued certificate. In principle, this continues the chain of trust all the way from the Secure Boot process as mentioned above to the actions of the applications installed on the device by users. Applications are also sandboxed, meaning that they can only modify the data within their individual home directory unless explicitly given permission to do otherwise. For example, they cannot access data owned by other user-installed applications on the device. There is a very extensive set of privacy controls contained within iOS with options to control apps' ability to access a wide variety of permissions such as the camera, contacts, background app refresh, cellular data, and access to other data and services. Most of the code in iOS, including third-party applications, runs as the "mobile" user which does not have root privileges. This ensures that system files and other iOS system resources remain hidden and inaccessible to user-installed applications. App Store bypasses Companies can apply to Apple for enterprise developer certificates. These can be used to sign apps such that iOS will install them directly (sometimes called "sideloading"), without the app needing to be distributed via the App Store. The terms under which they are granted make clear that they are only to be used for companies who wish to distribute apps directly to their employees. Circa January–February 2019, it emerged that a number of software developers were misusing enterprise developer certificates to distribute software directly to non-employees, thereby bypassing the App Store. Facebook was found to be abusing an Apple enterprise developer certificate to distribute an application to underage users that would give Facebook access to all private data on their devices. Google was abusing an Apple enterprise developer certificate to distribute an app to adults to collect data from their devices, including unencrypted data belonging to third parties. TutuApp, Panda Helper, AppValley, and TweakBox have all been abusing enterprise developer certificates to distribute apps that offer pirated software. Network Security iOS supports TLS with both low- and high-level APIs for developers. By default, the App Transport Security framework requires that servers use at least TLS 1.2. However, developers are free to override this framework and utilize their own methods of communicating over networks. When Wi-Fi is enabled, iOS uses a randomized MAC address so that devices cannot be tracked by anyone sniffing wireless traffic. Two-Factor Authentication Two-factor authentication is an option in iOS to ensure that even if an unauthorized person knows an Apple ID and password combination, they cannot gain access to the account. It works by requiring not only the Apple ID and password, but also a verification code that is sent to an iDevice or mobile phone number that is already known to be trusted. If an unauthorized user attempts to sign in using another user's Apple ID, the owner of the Apple ID receives a notification that allows them to deny access to the unrecognized device. Reception Market share iOS is the second most popular mobile operating system in the world, after Android. Sales of iPads in recent years are also behind Android, while, by web use (a proxy for all use), iPads (using iOS) are still the most popular. By the middle of 2012, there were 410 million devices activated. At WWDC 2014, Tim Cook said 800 million devices had been sold by June 2014. During Apple's quarterly earnings call in January 2015, the company announced that they had sold over one billion iOS devices since 2007. By late 2011, iOS accounted for 60% of the market share for smartphones and tablets. By the end of 2014, iOS accounted for 14.8% of the smartphone market and 27.6% of the tablet and two-in-one market. In February 2015, StatCounter reported iOS was used on 23.18% of smartphones and 66.25% of tablets worldwide, measured by internet usage instead of sales. In the third quarter of 2015, research from Strategy Analytics showed that iOS adoption of the worldwide smartphone market was at a record low 12.1%, attributed to lackluster performance in China and Africa. Android accounted for 87.5% of the market, with Windows Phone and BlackBerry accounting for the rest. Devices See also Comparison of mobile operating systems Android (operating system) References Further reading External links Dev Center at Apple Developer Connection iOS Reference Library – on the Apple Developer Connection website Apple Inc. operating systems Mach (kernel) Mobile operating systems Products introduced in 2007 Smartphones Tablet operating systems

Operating System (OS)

System V printing system The printing subsystem of UNIX System V is one of several standardized systems for printing on Unix, and is typical of commercial System V-based Unix versions such as Solaris and SCO OpenServer. A system running this print architecture could traditionally be identified by the use of the user command as the primary interface to the print system, as opposed to the BSD command (though some systems provide as an alias to ). Typical user commands available to the System V printing system are: : the user command to print a document : shows the current print queue : deletes a job from the print queue : a system administration command that configures the print system : a system administration command that moves jobs between print queues History In the Unix programming model, device files are special files that act as access points to peripheral devices such as printers. For example, the first line printer on a Unix system might be represented by a file in the device () directory, i.e., . Using the file metaphor, a document could by printed by "copying" the file onto the device: . While this worked well enough for the case where there was one printer per user, this model did not scale out well to multiple users having to share one printer. The solution was to create a queue (or "spool") of documents to be printed and use a daemon (system process) to manage this queue and send the documents to the printer in the order in which they arrived. Such a system, with an command to send documents to the queue, was first introduced in 1973 in Version 4 of Unix. By the release of System V Release 4, the suite of utilities had grown to include commands for canceling print jobs, moving jobs among queues, enabling and disabling queues, enabling and disabling a job scheduler daemon, and status reports of the print system. The command handled queue documents to be printed and had over 20 different options that controlled the appearance of the document and its place in the queue, and even handled email notification of the user once the document had finished printing. The command returned a "job id" which could be used by the cancel or lpstat commands to remove the job from the queue or check on its progress, respectively. While the system was considered to be quite complex to set up and administer, most uses were expected to only use these three commands. With its distribution in the influential AT&T Unix System V, the interface if not the implementation became the standard for users' control over printers. The command was included as a requirement in the POSIX.2 standard, and a command by that name appeared in the subsequent lpr, LPRng and CUPS printing systems. (In SVR4 derivates like SCO UNIX, the command was simply an alias for the command used by the BSD-based system.) As late as 1996, Running Linux stated "The Linux printing software consists of the UNIX standard lp and lpr software," but by 1999 support for lp was waning and the third edition simply stated "The lpr command prints a document on Linux." By 2003, a survey of the Debian, Mandrake, Red Hat, Slackware and SuSE distributions showed that all of them were running some combination of lpr, LPRng and CUPS. The original System V printing system remains proprietary; however, the Solaris print system, heavily modified from the original, has been released as open source software as part of the OpenSolaris project. The Common Unix Printing System emulates both System V and Berkeley print architectures on the interface level, though its internal architecture is different from both. Criticism In his introduction to a simplified configuration system for lp, author Peter Gray of the University of Wollongong described several weaknesses of the version shipping with the then-current Solaris (operating system) version 2. As opposed to the single daemon used by the simpler BSD lpr system, the lp system used separate daemons, one for scheduling and one for remote communication. The lpr system could be controlled with a single configuration file while lp requires a separate program for administration. The lp system did support permissions, but the model did not scale to hundreds of users. As a result, Gray observed that "many administrators choose to simply run the old lpr/lpd system on the SVR4 boxes." See also Berkeley printing system Common Unix Printing System (CUPS) LPRng References External links lp lpstat Printing administration on Solaris 10 Computer printing UNIX System V

Operating System (OS)

IBM TopView TopView is the first object-oriented, multitasking, and windowing, personal computer operating environment for PC DOS developed by IBM, announced in August 1984 and shipped in March 1985. TopView provided a text-mode (although it also ran in graphics mode) operating environment that allowed users to run more than one application at the same time on a PC. IBM demonstrated an early version of the product to key customers before making it generally available, around the time they shipped their new PC AT computer. Hopeful beginnings When Microsoft announced Windows 1.0 in November 1983, International Business Machines (IBM), Microsoft's important partner in popularizing MS-DOS for the IBM PC, notably did not announce support for the forthcoming window environment. IBM determined that the microcomputer market needed a multitasking environment. When it released TopView in 1985, the press speculated that the software was the start of IBM's plan to increase its control over the IBM PC (even though IBM published the specifications publicly) by creating a proprietary operating system for it, similar to what IBM had offered for years on its larger computers. TopView also allowed IBM to serve customers who were surprised that the new IBM AT did not come with an operating system able to use the hardware multitasking and protected mode features of the new 80286 CPU, as DOS and most applications were still running in 8086/8088 real mode. Even given TopView's virtual memory management capabilities, hardware limitations still held the new environment back—a base AT with 256 KB of RAM only had room for 80 KB of application code and data in RAM once DOS and TopView had loaded up. 512-640 KB was recommended to load up two typical application programs of the time. This was the maximum the earlier IBM XT could have installed. Once loaded, TopView took back much of the memory consumed by DOS, but still not enough to satisfy industry critics. TopView ran in real mode on any x86 processor and could run well behaved DOS programs (i.e. programs that did not write directly to the screen but used BIOS int 10h and DOS int 21h, such as the IBM Assistant Series of productivity programs) in an arrangement of windows. Well behaved applications would use standard DOS and BIOS function calls to access system services and hardware. Misbehaving programs (i.e. such as programs that did write directly to the screen) such as Lotus 1-2-3, WordStar and dBase III would still run in the TopView environment, but would consume the entire screen. Object-oriented applications were written using the TopView API. TopView was developed to run on the 8088 (and required what IBM referred to as a fixed disk) and later the 80286. TopView was not updated to make use of the virtual 8086 mode added in the Intel 80386 processors that allowed better virtualization. Initially, compatibility with the extended features was limited mainly to IBM applications, along with a few third-party products like WordPerfect and VolksWriter. A chicken-and-egg situation developed where third-party developers were reluctant to add extended feature support (such as block insert and delete to allow users to do cut/copy/paste between applications) when they did not see market demand for them. Most DOS programs did, however, support these functions and did allow the user to perform the cut, copy, and paste operations by using the TopView pop-up menus. Some believed that IBM planned to use TopView to force reliance on them to comply with the new technical specifications. As later versions of TopView were released, it was able to successfully make more challenging DOS apps run in a multitasking fashion by intercepting direct access to system services and hardware. TopView first introduced Program Information Files (PIF files), which defined how a given DOS program should be run in a multi-tasking environment, notably to avoid giving it unnecessary resources which could remain available to other programs. TopView's PIF files were inherited and extended by Quarterdeck's DESQview and Microsoft Windows. The concept of Program Information Files was also used under Digital Research operating systems such as Concurrent DOS, Multiuser DOS, Datapac System Manager and REAL/32; however, using the PIFED command, the necessary program information got directly embedded into the .EXE or .COM executable file. Version history Version 1.1, introduced in June 1986, added support for the IBM PC Network and IBM 3270 terminal emulation. Importantly, support for swapping non-resident programs was added—onto the hard disk on all computers and into the high memory area on machines equipped with a 286 CPU. The initially poor support for DOS batch files was improved. Version 1.12, introduced in April 1987, added support for the new IBM PS/2 series, their DOS 3.30 operating system, and their new PS/2 mice. It could also now use up to four serial ports. Decline and discontinuation TopView sold below expectations from the start, with many potential users already satisfied with cheaper, less memory-intensive TSR task switchers like Ready, Spotlight, and Borland Sidekick which didn't need a multitasking environment. TopView ran in graphics mode (TOPVIEW /G); however, this was rarely used. By mid-1987, IBM began to shift focus away from TopView and was promoting the use of OS/2 to developers and end users alike. OS/2 1.0 was a pre-emptive multitasking, multithreading OS that allowed one real mode and multiple 16-bit protected mode sessions to run at the same time on the PC/AT based 80286 and provided as a DOS alternative announced in April 1987 and made available later that December. A graphical user interface (Presentation Manager) was added with OS/2 1.1 in October 1988. 1.1 could run with or without Presentation Manager as well as an embedded system with no screen, keyboard or mouse interface required. IBM officially stopped marketing the final release of TopView, version 1.12, on 3 July 1990. TopView's concept was carried forward by other DOS multitaskers, most notably Quarterdeck's DESQview, which retained TopView's user interface and many features, plus added more features such as support for the special features of the 80286, 80386 and compatible processors, and, with DESQview/X (released in June 1992), a true GUI interface running on DOS. A variety of similar programs to TopView were also available, including one from Dynamical Systems called Mondrian, which Microsoft bought in 1986 with the stated intention of implementing TopView API compatibility into Windows which never happened. Later in April 1992, IBM introduced OS/2 2.0 which included virtual 8086 mode and full 32-bit support of the Intel 80386 superseding even DESQview and other similar environments. OS/2 2.0 was a priority based preemptive multitasking multithreading OS including 32 levels of priority (from time critical to idle time) for the 386. TopView requires IBM PC DOS versions 2.0 to 5.0 or MS-DOS 2.0 to 6.0, and will not run with later releases. Key contributors to TopView included David Morrill (the "father of TopView" code-named "Orion" once the GLASS project was moved to Boca Raton), Dennis McKinley (tasking), Ross Cook (memory management), Bob Hobbs (TopView Toolkit) and Neal Whitten (product manager). Bill Gates, Steve Ballmer, Gordon Letwin and other key Microsoft executives accepted an invitation from IBM executive Don Estridge to IBM Boca Raton to see a special demonstration of TopView. Gates was disturbed that Windows did not have the multitasking (Windows used a cooperative method to share the CPU) and windowing capabilities (i.e. overlapping windows, etc.) that TopView had. Gates witnessed TopView running multiple copies of the Microsoft BASIC interpreter running in windows (overlapping and side-by-side) in a multitasking fashion. Microsoft later released a multitasking version of MS-DOS 4.0 (multitasking) from what it learned from the meeting. Even though there was no joint development agreement with Microsoft for the development of TopView, Estridge asked and later told Whitten (against Whitten's and the TopView team's wishes) to turn over all source code and documentation of TopView to Microsoft. Within a short time after the meeting, Estridge's request was granted. Gates gave the code and documentation to a group headed by Nathan Myhrvold. Once the code had been modified according to Gates' specifications, he purchased the company. The product itself, Mondrian, was never released. Gates, however, gave members of the team key positions at Microsoft. This led to a Joint Development Agreement with Microsoft (an agreement that previously only included DOS) to co-develop OS/2 (an agreement that lasted until 1990). This was all done in order to satisfy the USA vs. IBM anti-trust court case that was filed in 1969. Even though it was dismissed in 1982, IBM was mired in antitrust troubles for more than a decade after the dismissal and did not recover from the legal morass until the early to mid-90s. In June 1990 an FTC probe was launched into possible collusion between Microsoft and IBM in the PC software market. Reception InfoWorld in 1985 described TopView as "bland, plain vanilla software that hogs far too much memory". BYTE also criticized TopView's memory usage, but stated that "you will find that most software written for the IBM PC is TopView-compatible". Noting the low price and "innovative multitasking features", the magazine predicted that the software "will attract a lot of takers". In 1985, Digital Research positioned their multitasking Concurrent DOS 4.1 with GEM as alternative for TopView. See also DOS Shell MS-DOS 4.0 (multitasking) OS/2 Visi On VM/386 References External links TopView: An early multi-tasking OS for the PC - a history of TopView by its lead developer DOS software TopView Operating system APIs Process (computing)

Operating System (OS)

SharpOS SharpOS is a discontinued computer operating system based on the .NET Framework and related programming language C#. It was developed by a group of volunteers and presided over by a team of six project administrators: Mircea-Cristian Racasan, Bruce Markham, Johann MacDonagh, Sander van Rossen, Jae Hyun, and William Lahti. It is no longer in active development, and resources have been moved to the MOSA project. As of 2017, SharpOS is one of three C#-based operating systems released under a free and open-source software license. SharpOS has only one public version available. and a basic command-line interface. History SharpOS began in November 2006 as a public discussion on the Mono development mailing list as a thread named Operating System in C#. After attracting many participants, Michael Schurter created the SharpOS.org wiki and mailing list to continue the discussion at a more relevant location. Soon after, the core developers (Bruce Markham, William Lahti, Sander van Rossen, and Mircea-Cristian Racasan) decided that they would design their own ahead-of-time (AOT) compiler to allow the operating system to run its boot sequence without using another programming language. Once the AOT compiler was developed enough, the team then began to code the kernel. This was met with long periods of inactivity and few active developers due to lack of interest in unsafe kernel programming. On 1 January 2008, the SharpOS team made their first milestone release public, this is the first version of the software to appear in the SharpOS SourceForge package repository available for general public use. Notes See also Singularity (operating system) Cosmos (operating system) External links Interview with SharpOS team sharpos-developers mailing list Operating system kernels Free software operating systems Beta software Hobbyist operating systems Microkernel-based operating systems Microkernels Discontinued operating systems

Operating System (OS)

AliOS AliOS (formerly YunOS and Aliyun OS) is a Linux distribution developed by Alibaba Cloud, a subsidiary of Mainland Chinese company Alibaba Group. It is designed for smart cars and Internet of Things (IoT) devices, and it had been used as a mobile operating system. History On 28 July 2011, Alibaba Cloud confirmed the existence of its own mobile operating system, the YunOS. The system was described as the result of three years of development and uses Alibaba Cloud's self-developed distributed file system and virtual machine, making it fully compatible with Android-based applications. With its YunOS, the company is challenging the dominant Android in China and is also looking to expand into Western markets. It was first used in the K-Touch W700 in 2011. As of May 2012, 1 million YunOS-powered smartphones have been sold. It was expected to become the second biggest operating system in China by shipments at the end of 2016, with 14% of the market. The latest publicly available version of YunOS, YunOS 5 Atom, as a forked version of Android 6.0, was released on 10 December 2015. In October 2017, Alibaba Group decided to upgrade its operating system strategy to focus investment on the burgeoning Internet of Things sector. As part of the move, Alibaba rebranded its YunOS operating system as AliOS, an operating system offering OS solutions for automobile, industrial and IoT devices. At the same time, Alibaba introduced an open-source IoT edition of AliOS, named as AliOS Things. Overview AliOS revolves around the idea of bringing cloud functionality to smart devices. According to the company, AliOS will feature cloud-based e-mail, Web search, weather updates, and GPS navigation tools. In addition, the AliOS services will synchronize and store call data, text messages, and photos in the cloud for access across other devices, including personal computers. Alibaba says it will offer customers 100 GB of storage at launch. AliOS would allow users to access applications from the Web, rather than download apps to their devices. In the meantime, AliOS Things, as a lightweight IoT embedded operating system for the IoT field, would be suitable for all kinds of small loT devices, and can be widely used in smart home, smart city, new travel and other fields. Relations with Android According to Google, AliOS is a forked but incompatible version of its open-source Android operating system. The company therefore attempted to prevent Acer Inc. from shipping an AliOS-powered phone, arguing that Acer, a member of the Open Handset Alliance, had agreed not to produce phones running incompatible Android versions. Andy Rubin, who at the time was in charge of the Android division at Google, stated that while AliOS is not part of the Android ecosystem, it uses runtimes, framework and various tools from Android. Alibaba disputes the claim that AliOS is a version of Android by stating the following:"Aliyun OS [now AliOS] incorporates its own virtual machine, which is different from Android's Dalvik virtual machine. AliOS' runtime environment, which is the core of the OS, consists of both its own Java virtual machine, which is different from Android’s Dalvik virtual machine, and its own cloud app engine, which supports HTML5 web applications. AliOS uses some of the Android application framework and tools (open source) merely as a patch to allow AliOS users to enjoy third-party apps in addition to the cloud-based AliOS apps in our ecosystem."However, as of September 2012, the AliOS app store still contains some pirated Android applications, including many from Google. AliOS Things AliOS Things is the IoT version of AliOS announced and open-sourced in 2017. It is designed for low power, resource constrained MCUs, as well as connectivity SoCs. AliOS Things comes in two editions, one based on the Linux kernel and the other based on Rhino, Alibaba's RTOS kernel. Controversy In 2015 November, following Chinese State Administration of Press, Publication, Radio, Film and Television's policy, dozens of third-party applications installed by users on their own YunOS set-top boxes were automatically removed and blocked from re-installation. See also Flyme OS HarmonyOS References Cloud clients Mobile Linux Products introduced in 2011 Mobile operating systems Alibaba Group Chinese brands

Operating System (OS)

IBM platform (disambiguation) The term IBM platform could refer to any of the hardware and operating systems below. Current IBM Power Systems, a family name for the merged System p and System i PureSystems, an IBM product line of factory pre-configured components and servers also being referred to as an "Expert Integrated System" IBM Z, a family name used by IBM for all of its z/Architecture mainframe computers from the Z900 on; this is the most recent architecture descended from IBM System/360 IBM System z, an older name for IBM Z IBM z System, an older name for IBM Z IBM PC compatible, a machine compatible with the IBM PC and successors. IBM i, an operating system that runs on IBM Power Systems and IBM PureSystems, preceded by: CPF, the operating system for the S/38 OS/400, the operating system for the AS/400 i5/OS, the operating system for the eServer i5 z/OS, a 64-bit operating system for IBM mainframes; this is the most recent incarnation of OS/360 and successors Discontinued IBM System i, preceded by S/38, AS/400 and eServer i5, is a line of midrange computer systems from IBM that uses the IBM i operating system IBM System p, formerly known as RS/6000, was IBM's RISC/UNIX-based server product line. IBM System/360, the predecessor to S/370 IBM System/370, the predecessor to XA/370 IBM Extended Architecture/370 (XA/370), the predecessor to ESA/370 IBM Enterprise Systems Architecture/370 (ESA/370), the predecessor to IBM System/390 IBM System/390, the predecessor to IBM System z IBM Personal Computer, commonly known as the IBM PC, is the original version of the IBM PC compatible hardware platform Operating System/360 (OS/360), IBM's flagship operating system for S/360 and early S/370 OS/VS1, successor to OS/360 MFT SVS, OS/VS2 Release 1, successor to OS/360 MVT and predecessor to MVS MVS/370 is a generic term for all versions of the MVS operating system prior to MVS/XA OS/VS2 Release 2 through 3.8 MVS/System Extension (MVS/SE) MVS/System Product (MVS/SP) Version 1 MVS/XA, predecessor of MVS/ESA MVS/ESA, predecessor of OS/390 OS/390, predecessor of z/OS Suprercomputer platforms: IBM Scalable POWERparallel (1993-2000) QCDOC (1998-1999) IBM Blue Gene (1999-2015) IBM iDataPlex (2008-2014) IBM PERCS (2011) IBM Intelligent Cluster, (2001-2014, now Lenovo Intelligent Cluster) See also IBM System (disambiguation)

Operating System (OS)

Verve (operating system) Verve is a research operating system developed by Microsoft Research. Verve is verified end-to-end for type safety and memory safety. Because of their complexity, a holy grail of software verification has been to verify properties of operating systems. Operating systems are usually written in low-level languages, such as C, that provide very few guarantees. The Singularity project took the approach of writing an operating system in C#, a type-safe, memory-safe language. A weakness of this approach is that operating systems necessarily need to call lower-level code to, for instance, move the stack pointer. Verve addresses this problem by partitioning the operating system into verified assembly language that is required to be low-level and a trusted interface to rest of the operating system, written in C#. There is a trusted specification that guarantees the low-level assembly code does not modify the heap and that the high-level C# code does not modify the stacks. Verve consists of a small Nucleus, which acts as a minimal hardware abstraction layer, and a Kernel, which uses primitives provided by the Nucleus to expose a more traditional interface to applications. All components of the system other than the Nucleus are written in managed code C# and compiled by Bartok (originally developed for the Singularity project) into typed assembly language (TAL), which is verified by a TAL checker. The Nucleus implements a memory allocator and garbage collection, support for stack switching, and managing interrupt handlers. It is written in BoogiePL, which serves as input to MSR's Boogie verifier, which proves the Nucleus correct using the Z3 Theorem Prover satisfiability modulo theories (SMT) automated theorem prover (solver). The Nucleus relies on the Kernel to implement threads, scheduling, synchronization, and to provide most interrupt handlers. Even though the Kernel is not formally verified, so, for example, a bug in scheduling could cause the system to hang, it cannot violate type or memory safety, and thus cannot directly cause undefined behavior. If it attempts to make invalid requests to the Nucleus, formal verification guarantees that the Nucleus handles the situation in a controlled manner. Verve's trusted computing base (TCB) is limited to: Boogie/Z3 for verifying the Nucleus's correctness; BoogieASM for translating it into x86 assembly; the BoogiePL specification of how the Nucleus should behave; the TAL verifier; the assembler and linker; and the bootloader. Notably, neither the C# compiler/runtime nor the Bartok compiler are part of the TCB. References Safe to the Last Instruction: Automated Verification of a Type-Safe Operating System, Jean Yang and Chris Hawblitzel. Programming Language Design and Implementation, 2010. Safe to the Last Instruction: Automated Verification of a Type-Safe Operating System, Jean Yang and Chris Hawblitzel. CACM Research Highlight. Communications of the ACM, September 2010. Technical Perspective: Safety First! Verve: A Type Safe Operating System. Interview with Chris Hawblitzel. Verve: A Type Safe Operating System. OSnews. Announcing Verve – A Type-Safe Operating System. InfoQ. Microsoft operating systems Microsoft Research Microkernel-based operating systems Microkernels Nanokernels

Operating System (OS)

Open platform In computing, an open platform describes a software system which is based on open standards, such as published and fully documented external application programming interfaces (API) that allow using the software to function in other ways than the original programmer intended, without requiring modification of the source code. Using these interfaces, a third party could integrate with the platform to add functionality. The opposite is a closed platform. An open platform does not mean it is open source, however most open platforms have multiple implementations of APIs. For example, Common Gateway Interface (CGI) is implemented by open source web servers as well as Microsoft Internet Information Server (IIS). An open platform can consist of software components or modules that are either proprietary or open source or both. It can also exist as a part of closed platform, such as CGI, which is an open platform, while many servers that implement CGI also have other proprietary parts that are not part of the open platform. An open platform implies that the vendor allows, and perhaps supports, the ability to do this. Using an open platform a developer could add features or functionality that the platform vendor had not completed or had not conceived of. An open platform allows the developer to change existing functionality, as the specifications are publicly available open standards. A service-oriented architecture allows applications, running as services, to be accessed in a distributed computing environment, such as between multiple systems or across the Internet. A major focus of Web services is to make functional building blocks accessible over standard Internet protocols that are independent from platforms and programming languages. An open SOA platform would allow anyone to access and interact with these building blocks. A 2008 Harvard Business School working paper, titled "Opening Platforms: How, When and Why?", differentiated a platform's openness in four aspects and gave example platforms. References See also Application programming interface Open standard Open architecture Service-oriented architecture Application programming interfaces Computing platforms

Operating System (OS)

Open Programming Language Open Programming Language (OPL) is a programming language for embedded systems and mobile devices that run the operating systems EPOC and Symbian. It was released by the English company Psion in 1984. Use It can be found on the Nokia 9200, 9300 and 9500 Communicator series mobile telephone and personal digital assistant (PDA) and the Sony Ericsson P800, P900, P910 series. On classic Psion PDAs such as the Series 3, 5/5mx, Series 7, and netBook–netPad, and the MC218, OPL is part of the standard application suite. OPL is also included in Psion Teklogix industrial handhelds such as the Workabout mx. OPL is an interpreted language similar to BASIC. A fully Visual Basic-compatible language OVAL has been also developed. History The language was originally named Organiser Programming Language, developed by Psion Ltd for the Psion Organiser. Designed by Colly Myers with the first iteration implemented by Richard Harrison and Martin Stamp. The first implementation (without graphics) was for the original Psion Organiser (now referred to as the Psion Organiser I, 1984), and it came bundled with the Science, Finance and Math data packs. It became truly accessible as built-in software in the Psion Organiser II (1986), and the language went on to be used in the Psion Series 3 and later. After Psion retired from the personal digital assistant market, the project was delayed until 2003, when the fledgling Symbian Developer Program released it as open-source software. The language is now developed on SourceForge in a project named opl-dev. The language is unavailable from Symbian OS v8 and later, mainly due to lack of interest and support from major Symbian licencees Nokia and Sony Ericsson. Hence, OPL will most likely never be made available for later generations of Symbian OS phones such as Sony Ericsson P990, M600, W950, P1i, and Nokia E61i and E90. As of 2010, Nokia device developers are encouraged to use Python for S60 instead (See Python for S60). Examples Here is the console version of a "Hello, World!" program: PROC main: PRINT "Hello World!" PAUSE 40 ENDP (Source code taken from the PCDevPrimer in the OPL Wiki.) And here is a GUI version for Nokia's Series 80 user interface: CONST KKeyEnter%=13 PROC hello: dINIT "Hello" dTEXT "","Hello World!" dBUTTONS "OK",KKeyEnter% DIALOG ENDP OPL is a structured programming language. OPL programs contain PROCedures, which are much like functions (subroutines) in other programming languages. The dINIT keyword in this example initializes a dialog box (intuitively enough, all dialog-box related functions begin with a letter 'd'; for clarity, this letter is in lower case, but the language is case independent). The first argument of the dialog is an optional string, which is used for the title of the dialog, displayed in the title bar. The dTEXT function displays text, with two compulsory arguments: a left-aligned 'prompt' string, and a main string. The dBUTTONS keyword allows you to put buttons on the dialog box - here there is a button with the text "OK". The second argument to each button is both the special notation of the shortcut key for that button and the dialog's return code, in this case the "Enter" key. Finally, the DIALOG keyword is required for the previously initialized dialog box to be shown on the screen. Testing dialog responses An example: PROC test: dINIT "Your Challenge" dTEXT "","Will your answer to this question be no?" dBUTTONS "Yes",%y,"No",%n IF DIALOG=%y PRINT "No it wasn't!" ELSE PRINT "Yes it was!" ENDIF GET ENDP In this cruel interrogative program, the Yes button is assigned the shortcut of Ctrl+y, while No has Ctrl+n, represented by %y and %n respectively. The user's input from the DIALOG is tested in the IF statement, PRINTing appropriate responses to the screen. Note that the 'GET' keyword, which gets user input without using a dialog box, is here used simply to wait for a keypress before terminating the program (otherwise it would end immediately without giving time for the user to read the text). The output from DIALOG can also be stored in a variable. Variables specific to a procedure must be declared with the LOCAL keyword; global variables are defined with the GLOBAL keyword. Variable types The table below uses an example variable named var. Minutiae OPL interfaced with advanced Psion Series 3 features by means of operating system CALLs, but in the later Psion Series 5mx this was changed to a so-called OPX library, stored in the system read-only memory (ROM), termed the Z drive. 'OPX' libraries were also made available for the Nokia 9210, Nokia 9300 and Nokia 9500 Communicators, adding OPXs routines for handling Short Message Service (SMS) and managing Bluetooth communication. Other OPL features include those starting with a letter: g for graphical functions, m for menus, and d for dialogs. See also Psion Organiser Symbian References External links The opl-dev project OPL wiki on Internet Archive containing documents detailing OPL keywords, OPX interfaces and much other information OPL Blog by Symbian, now dead, but old versions are available from the Internet Archive Russian site about OPL OPL programming tutorial Embedded systems Free mobile software Symbian OS Procedural programming languages BASIC programming language family Software using the LGPL license Computer-related introductions in 1984

Operating System (OS)

File system In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one large body of data with no way to tell where one piece of data stopped and the next began, or where any piece of data was located when it was time to retrieve it. By separating the data into pieces and giving each piece a name, the data is easily isolated and identified. Taking its name from the way a paper-based data management system is named, each group of data is called a "file." The structure and logic rules used to manage the groups of data and their names is called a "file system." There are many different kinds of file systems. Each one has different structure and logic, properties of speed, flexibility, security, size and more. Some file systems have been designed to be used for specific applications. For example, the ISO 9660 file system is designed specifically for optical discs. File systems can be used on numerous different types of storage devices that use different kinds of media. As of 2019, hard disk drives have been key storage devices and are projected to remain so for the foreseeable future. Other kinds of media that are used include SSDs, magnetic tapes, and optical discs. In some cases, such as with tmpfs, the computer's main memory (random-access memory, RAM) is used to create a temporary file system for short-term use. Some file systems are used on local data storage devices; others provide file access via a network protocol (for example, NFS, SMB, or 9P clients). Some file systems are "virtual", meaning that the supplied "files" (called virtual files) are computed on request (such as procfs and sysfs) or are merely a mapping into a different file system used as a backing store. The file system manages access to both the content of files and the metadata about those files. It is responsible for arranging storage space; reliability, efficiency, and tuning with regard to the physical storage medium are important design considerations. Origin of the term Before the advent of computers the term file system was used to describe a method of storing and retrieving paper documents. By 1961, the term was being applied to computerized filing alongside the original meaning. By 1964, it was in general use. Architecture A file system consists of two or three layers. Sometimes the layers are explicitly separated, and sometimes the functions are combined. The logical file system is responsible for interaction with the user application. It provides the application program interface (API) for file operations — OPEN, CLOSE, READ, etc., and passes the requested operation to the layer below it for processing. The logical file system "manage[s] open file table entries and per-process file descriptors". This layer provides "file access, directory operations, [and] security and protection". The second optional layer is the virtual file system. "This interface allows support for multiple concurrent instances of physical file systems, each of which is called a file system implementation". The third layer is the physical file system. This layer is concerned with the physical operation of the storage device (e.g. disk). It processes physical blocks being read or written. It handles buffering and memory management and is responsible for the physical placement of blocks in specific locations on the storage medium. The physical file system interacts with the device drivers or with the channel to drive the storage device. Aspects of file systems Space management Note: this only applies to file systems used in storage devices. File systems allocate space in a granular manner, usually multiple physical units on the device. The file system is responsible for organizing files and directories, and keeping track of which areas of the media belong to which file and which are not being used. For example, in Apple DOS of the early 1980s, 256-byte sectors on 140 kilobyte floppy disk used a track/sector map. This results in unused space when a file is not an exact multiple of the allocation unit, sometimes referred to as slack space. For a 512-byte allocation, the average unused space is 256 bytes. For 64 KB clusters, the average unused space is 32 KB. The size of the allocation unit is chosen when the file system is created. Choosing the allocation size based on the average size of the files expected to be in the file system can minimize the amount of unusable space. Frequently the default allocation may provide reasonable usage. Choosing an allocation size that is too small results in excessive overhead if the file system will contain mostly very large files. File system fragmentation occurs when unused space or single files are not contiguous. As a file system is used, files are created, modified and deleted. When a file is created, the file system allocates space for the data. Some file systems permit or require specifying an initial space allocation and subsequent incremental allocations as the file grows. As files are deleted, the space they were allocated eventually is considered available for use by other files. This creates alternating used and unused areas of various sizes. This is free space fragmentation. When a file is created and there is not an area of contiguous space available for its initial allocation, the space must be assigned in fragments. When a file is modified such that it becomes larger, it may exceed the space initially allocated to it, another allocation must be assigned elsewhere and the file becomes fragmented. In some operating systems, a system administrator may use disk quotas to limit the allocation of disk space. Filenames A filename (or file name) is used to identify a storage location in the file system. Most file systems have restrictions on the length of filenames. In some file systems, filenames are not case sensitive (i.e., the names MYFILE and myfile refer to the same file in a directory); in others, filenames are case sensitive (i.e., the names MYFILE, MyFile, and myfile refer to three separate files that are in the same directory). Most modern file systems allow filenames to contain a wide range of characters from the Unicode character set. However, they may have restrictions on the use of certain special characters, disallowing them within filenames; those characters might be used to indicate a device, device type, directory prefix, file path separator, or file type. Directories File systems typically have directories (also called folders) which allow the user to group files into separate collections. This may be implemented by associating the file name with an index in a table of contents or an inode in a Unix-like file system. Directory structures may be flat (i.e. linear), or allow hierarchies where directories may contain subdirectories. The first file system to support arbitrary hierarchies of directories was used in the Multics operating system. The native file systems of Unix-like systems also support arbitrary directory hierarchies, as do, for example, Apple's Hierarchical File System, and its successor HFS+ in classic Mac OS, the FAT file system in MS-DOS 2.0 and later versions of MS-DOS and in Microsoft Windows, the NTFS file system in the Windows NT family of operating systems, and the ODS-2 (On-Disk Structure-2) and higher levels of the Files-11 file system in OpenVMS. Metadata Other bookkeeping information is typically associated with each file within a file system. The length of the data contained in a file may be stored as the number of blocks allocated for the file or as a byte count. The time that the file was last modified may be stored as the file's timestamp. File systems might store the file creation time, the time it was last accessed, the time the file's metadata was changed, or the time the file was last backed up. Other information can include the file's device type (e.g. block, character, socket, subdirectory, etc.), its owner user ID and group ID, its access permissions and other file attributes (e.g. whether the file is read-only, executable, etc.). A file system stores all the metadata associated with the file—including the file name, the length of the contents of a file, and the location of the file in the folder hierarchy—separate from the contents of the file. Most file systems store the names of all the files in one directory in one place—the directory table for that directory—which is often stored like any other file. Many file systems put only some of the metadata for a file in the directory table, and the rest of the metadata for that file in a completely separate structure, such as the inode. Most file systems also store metadata not associated with any one particular file. Such metadata includes information about unused regions—free space bitmap, block availability map—and information about bad sectors. Often such information about an allocation group is stored inside the allocation group itself. Additional attributes can be associated on file systems, such as NTFS, XFS, ext2, ext3, some versions of UFS, and HFS+, using extended file attributes. Some file systems provide for user defined attributes such as the author of the document, the character encoding of a document or the size of an image. Some file systems allow for different data collections to be associated with one file name. These separate collections may be referred to as streams or forks. Apple has long used a forked file system on the Macintosh, and Microsoft supports streams in NTFS. Some file systems maintain multiple past revisions of a file under a single file name; the filename by itself retrieves the most recent version, while prior saved version can be accessed using a special naming convention such as "filename;4" or "filename(-4)" to access the version four saves ago. See comparison of file systems#Metadata for details on which file systems support which kinds of metadata. File system as an abstract user interface In some cases, a file system may not make use of a storage device but can be used to organize and represent access to any data, whether it is stored or dynamically generated (e.g. procfs). Utilities File systems include utilities to initialize, alter parameters of and remove an instance of the file system. Some include the ability to extend or truncate the space allocated to the file system. Directory utilities may be used to create, rename and delete directory entries, which are also known as dentries (singular: dentry), and to alter metadata associated with a directory. Directory utilities may also include capabilities to create additional links to a directory (hard links in Unix), to rename parent links (".." in Unix-like operating systems), and to create bidirectional links to files. File utilities create, list, copy, move and delete files, and alter metadata. They may be able to truncate data, truncate or extend space allocation, append to, move, and modify files in-place. Depending on the underlying structure of the file system, they may provide a mechanism to prepend to or truncate from the beginning of a file, insert entries into the middle of a file, or delete entries from a file. Utilities to free space for deleted files, if the file system provides an undelete function, also belong to this category. Some file systems defer operations such as reorganization of free space, secure erasing of free space, and rebuilding of hierarchical structures by providing utilities to perform these functions at times of minimal activity. An example is the file system defragmentation utilities. Some of the most important features of file system utilities are supervisory activities which may involve bypassing ownership or direct access to the underlying device. These include high-performance backup and recovery, data replication, and reorganization of various data structures and allocation tables within the file system. Restricting and permitting access There are several mechanisms used by file systems to control access to data. Usually the intent is to prevent reading or modifying files by a user or group of users. Another reason is to ensure data is modified in a controlled way so access may be restricted to a specific program. Examples include passwords stored in the metadata of the file or elsewhere and file permissions in the form of permission bits, access control lists, or capabilities. The need for file system utilities to be able to access the data at the media level to reorganize the structures and provide efficient backup usually means that these are only effective for polite users but are not effective against intruders. Methods for encrypting file data are sometimes included in the file system. This is very effective since there is no need for file system utilities to know the encryption seed to effectively manage the data. The risks of relying on encryption include the fact that an attacker can copy the data and use brute force to decrypt the data. Additionally, losing the seed means losing the data. Maintaining integrity One significant responsibility of a file system is to ensure that the file system structures in secondary storage remain consistent, regardless of the actions by programs accessing the file system. This includes actions taken if a program modifying the file system terminates abnormally or neglects to inform the file system that it has completed its activities. This may include updating the metadata, the directory entry and handling any data that was buffered but not yet updated on the physical storage media. Other failures which the file system must deal with include media failures or loss of connection to remote systems. In the event of an operating system failure or "soft" power failure, special routines in the file system must be invoked similar to when an individual program fails. The file system must also be able to correct damaged structures. These may occur as a result of an operating system failure for which the OS was unable to notify the file system, a power failure, or a reset. The file system must also record events to allow analysis of systemic issues as well as problems with specific files or directories. User data The most important purpose of a file system is to manage user data. This includes storing, retrieving and updating data. Some file systems accept data for storage as a stream of bytes which are collected and stored in a manner efficient for the media. When a program retrieves the data, it specifies the size of a memory buffer and the file system transfers data from the media to the buffer. A runtime library routine may sometimes allow the user program to define a record based on a library call specifying a length. When the user program reads the data, the library retrieves data via the file system and returns a record. Some file systems allow the specification of a fixed record length which is used for all writes and reads. This facilitates locating the nth record as well as updating records. An identification for each record, also known as a key, makes for a more sophisticated file system. The user program can read, write and update records without regard to their location. This requires complicated management of blocks of media usually separating key blocks and data blocks. Very efficient algorithms can be developed with pyramid structures for locating records. Using a file system Utilities, language specific run-time libraries and user programs use file system APIs to make requests of the file system. These include data transfer, positioning, updating metadata, managing directories, managing access specifications, and removal. Multiple file systems within a single system Frequently, retail systems are configured with a single file system occupying the entire storage device. Another approach is to partition the disk so that several file systems with different attributes can be used. One file system, for use as browser cache or email storage, might be configured with a small allocation size. This keeps the activity of creating and deleting files typical of browser activity in a narrow area of the disk where it will not interfere with other file allocations. Another partition might be created for the storage of audio or video files with a relatively large block size. Yet another may normally be set read-only and only periodically be set writable. A third approach, which is mostly used in cloud systems, is to use "disk images" to house additional file systems, with the same attributes or not, within another (host) file system as a file. A common example is virtualization: one user can run an experimental Linux distribution (using the ext4 file system) in a virtual machine under his/her production Windows environment (using NTFS). The ext4 file system resides in a disk image, which is treated as a file (or multiple files, depending on the hypervisor and settings) in the NTFS host file system. Having multiple file systems on a single system has the additional benefit that in the event of a corruption of a single partition, the remaining file systems will frequently still be intact. This includes virus destruction of the system partition or even a system that will not boot. File system utilities which require dedicated access can be effectively completed piecemeal. In addition, defragmentation may be more effective. Several system maintenance utilities, such as virus scans and backups, can also be processed in segments. For example, it is not necessary to backup the file system containing videos along with all the other files if none have been added since the last backup. As for the image files, one can easily "spin off" differential images which contain only "new" data written to the master (original) image. Differential images can be used for both safety concerns (as a "disposable" system - can be quickly restored if destroyed or contaminated by a virus, as the old image can be removed and a new image can be created in matter of seconds, even without automated procedures) and quick virtual machine deployment (since the differential images can be quickly spawned using a script in batches). Design limitations All file systems have some functional limit that defines the maximum storable data capacity within that system. These functional limits are a best-guess effort by the designer based on how large the storage systems are right now and how large storage systems are likely to become in the future. Disk storage has continued to increase at near exponential rates (see Moore's law), so after a few years, file systems have kept reaching design limitations that require computer users to repeatedly move to a newer system with ever-greater capacity. File system complexity typically varies proportionally with the available storage capacity. The file systems of early 1980s home computers with 50 KB to 512 KB of storage would not be a reasonable choice for modern storage systems with hundreds of gigabytes of capacity. Likewise, modern file systems would not be a reasonable choice for these early systems, since the complexity of modern file system structures would quickly consume or even exceed the very limited capacity of the early storage systems. Types of file systems File system types can be classified into disk/tape file systems, network file systems and special-purpose file systems. Disk file systems A disk file system takes advantages of the ability of disk storage media to randomly address data in a short amount of time. Additional considerations include the speed of accessing data following that initially requested and the anticipation that the following data may also be requested. This permits multiple users (or processes) access to various data on the disk without regard to the sequential location of the data. Examples include FAT (FAT12, FAT16, FAT32), exFAT, NTFS, HFS and HFS+, HPFS, APFS, UFS, ext2, ext3, ext4, XFS, btrfs, Files-11, Veritas File System, VMFS, ZFS, ReiserFS and ScoutFS. Some disk file systems are journaling file systems or versioning file systems. Optical discs ISO 9660 and Universal Disk Format (UDF) are two common formats that target Compact Discs, DVDs and Blu-ray discs. Mount Rainier is an extension to UDF supported since 2.6 series of the Linux kernel and since Windows Vista that facilitates rewriting to DVDs. Flash file systems A flash file system considers the special abilities, performance and restrictions of flash memory devices. Frequently a disk file system can use a flash memory device as the underlying storage media but it is much better to use a file system specifically designed for a flash device. Tape file systems A tape file system is a file system and tape format designed to store files on tape. Magnetic tapes are sequential storage media with significantly longer random data access times than disks, posing challenges to the creation and efficient management of a general-purpose file system. In a disk file system there is typically a master file directory, and a map of used and free data regions. Any file additions, changes, or removals require updating the directory and the used/free maps. Random access to data regions is measured in milliseconds so this system works well for disks. Tape requires linear motion to wind and unwind potentially very long reels of media. This tape motion may take several seconds to several minutes to move the read/write head from one end of the tape to the other. Consequently, a master file directory and usage map can be extremely slow and inefficient with tape. Writing typically involves reading the block usage map to find free blocks for writing, updating the usage map and directory to add the data, and then advancing the tape to write the data in the correct spot. Each additional file write requires updating the map and directory and writing the data, which may take several seconds to occur for each file. Tape file systems instead typically allow for the file directory to be spread across the tape intermixed with the data, referred to as streaming, so that time-consuming and repeated tape motions are not required to write new data. However, a side effect of this design is that reading the file directory of a tape usually requires scanning the entire tape to read all the scattered directory entries. Most data archiving software that works with tape storage will store a local copy of the tape catalog on a disk file system, so that adding files to a tape can be done quickly without having to rescan the tape media. The local tape catalog copy is usually discarded if not used for a specified period of time, at which point the tape must be re-scanned if it is to be used in the future. IBM has developed a file system for tape called the Linear Tape File System. The IBM implementation of this file system has been released as the open-source IBM Linear Tape File System — Single Drive Edition (LTFS-SDE) product. The Linear Tape File System uses a separate partition on the tape to record the index meta-data, thereby avoiding the problems associated with scattering directory entries across the entire tape. Tape formatting Writing data to a tape, erasing, or formatting a tape is often a significantly time-consuming process and can take several hours on large tapes. With many data tape technologies it is not necessary to format the tape before over-writing new data to the tape. This is due to the inherently destructive nature of overwriting data on sequential media. Because of the time it can take to format a tape, typically tapes are pre-formatted so that the tape user does not need to spend time preparing each new tape for use. All that is usually necessary is to write an identifying media label to the tape before use, and even this can be automatically written by software when a new tape is used for the first time. Database file systems Another concept for file management is the idea of a database-based file system. Instead of, or in addition to, hierarchical structured management, files are identified by their characteristics, like type of file, topic, author, or similar rich metadata. IBM DB2 for i (formerly known as DB2/400 and DB2 for i5/OS) is a database file system as part of the object based IBM i operating system (formerly known as OS/400 and i5/OS), incorporating a single level store and running on IBM Power Systems (formerly known as AS/400 and iSeries), designed by Frank G. Soltis IBM's former chief scientist for IBM i. Around 1978 to 1988 Frank G. Soltis and his team at IBM Rochester have successfully designed and applied technologies like the database file system where others like Microsoft later failed to accomplish. These technologies are informally known as 'Fortress Rochester' and were in few basic aspects extended from early Mainframe technologies but in many ways more advanced from a technological perspective. Some other projects that aren't "pure" database file systems but that use some aspects of a database file system: Many Web content management systems use a relational DBMS to store and retrieve files. For example, XHTML files are stored as XML or text fields, while image files are stored as blob fields; SQL SELECT (with optional XPath) statements retrieve the files, and allow the use of a sophisticated logic and more rich information associations than "usual file systems." Many CMSs also have the option of storing only metadata within the database, with the standard filesystem used to store the content of files. Very large file systems, embodied by applications like Apache Hadoop and Google File System, use some database file system concepts. Transactional file systems Some programs need to either make multiple file system changes, or, if one or more of the changes fail for any reason, make none of the changes. For example, a program which is installing or updating software may write executables, libraries, and/or configuration files. If some of the writing fails and the software is left partially installed or updated, the software may be broken or unusable. An incomplete update of a key system utility, such as the command shell, may leave the entire system in an unusable state. Transaction processing introduces the atomicity guarantee, ensuring that operations inside of a transaction are either all committed or the transaction can be aborted and the system discards all of its partial results. This means that if there is a crash or power failure, after recovery, the stored state will be consistent. Either the software will be completely installed or the failed installation will be completely rolled back, but an unusable partial install will not be left on the system. Transactions also provide the isolation guarantee, meaning that operations within a transaction are hidden from other threads on the system until the transaction commits, and that interfering operations on the system will be properly serialized with the transaction. Windows, beginning with Vista, added transaction support to NTFS, in a feature called Transactional NTFS, but its use is now discouraged. There are a number of research prototypes of transactional file systems for UNIX systems, including the Valor file system, Amino, LFS, and a transactional ext3 file system on the TxOS kernel, as well as transactional file systems targeting embedded systems, such as TFFS. Ensuring consistency across multiple file system operations is difficult, if not impossible, without file system transactions. File locking can be used as a concurrency control mechanism for individual files, but it typically does not protect the directory structure or file metadata. For instance, file locking cannot prevent TOCTTOU race conditions on symbolic links. File locking also cannot automatically roll back a failed operation, such as a software upgrade; this requires atomicity. Journaling file systems is one technique used to introduce transaction-level consistency to file system structures. Journal transactions are not exposed to programs as part of the OS API; they are only used internally to ensure consistency at the granularity of a single system call. Data backup systems typically do not provide support for direct backup of data stored in a transactional manner, which makes the recovery of reliable and consistent data sets difficult. Most backup software simply notes what files have changed since a certain time, regardless of the transactional state shared across multiple files in the overall dataset. As a workaround, some database systems simply produce an archived state file containing all data up to that point, and the backup software only backs that up and does not interact directly with the active transactional databases at all. Recovery requires separate recreation of the database from the state file after the file has been restored by the backup software. Network file systems A network file system is a file system that acts as a client for a remote file access protocol, providing access to files on a server. Programs using local interfaces can transparently create, manage and access hierarchical directories and files in remote network-connected computers. Examples of network file systems include clients for the NFS, AFS, SMB protocols, and file-system-like clients for FTP and WebDAV. Shared disk file systems A shared disk file system is one in which a number of machines (usually servers) all have access to the same external disk subsystem (usually a SAN). The file system arbitrates access to that subsystem, preventing write collisions. Examples include GFS2 from Red Hat, GPFS, now known as Spectrum Scale, from IBM, SFS from DataPlow, CXFS from SGI, StorNext from Quantum Corporation and ScoutFS from Versity. Special file systems A special file system presents non-file elements of an operating system as files so they can be acted on using file system APIs. This is most commonly done in Unix-like operating systems, but devices are given file names in some non-Unix-like operating systems as well. Device file systems A device file system represents I/O devices and pseudo-devices as files, called device files. Examples in Unix-like systems include devfs and, in Linux 2.6 systems, udev. In non-Unix-like systems, such as TOPS-10 and other operating systems influenced by it, where the full filename or pathname of a file can include a device prefix, devices other than those containing file systems are referred to by a device prefix specifying the device, without anything following it. Other special file systems In the Linux kernel, configfs and sysfs provide files that can be used to query the kernel for information and configure entities in the kernel. procfs maps processes and, on Linux, other operating system structures into a filespace. Minimal file system / audio-cassette storage In the 1970s disk and digital tape devices were too expensive for some early microcomputer users. An inexpensive basic data storage system was devised that used common audio cassette tape. When the system needed to write data, the user was notified to press "RECORD" on the cassette recorder, then press "RETURN" on the keyboard to notify the system that the cassette recorder was recording. The system wrote a sound to provide time synchronization, then modulated sounds that encoded a prefix, the data, a checksum and a suffix. When the system needed to read data, the user was instructed to press "PLAY" on the cassette recorder. The system would listen to the sounds on the tape waiting until a burst of sound could be recognized as the synchronization. The system would then interpret subsequent sounds as data. When the data read was complete, the system would notify the user to press "STOP" on the cassette recorder. It was primitive, but it (mostly) worked. Data was stored sequentially, usually in an unnamed format, although some systems (such as the Commodore PET series of computers) did allow the files to be named. Multiple sets of data could be written and located by fast-forwarding the tape and observing at the tape counter to find the approximate start of the next data region on the tape. The user might have to listen to the sounds to find the right spot to begin playing the next data region. Some implementations even included audible sounds interspersed with the data. Flat file systems In a flat file system, there are no subdirectories; directory entries for all files are stored in a single directory. When floppy disk media was first available this type of file system was adequate due to the relatively small amount of data space available. CP/M machines featured a flat file system, where files could be assigned to one of 16 user areas and generic file operations narrowed to work on one instead of defaulting to work on all of them. These user areas were no more than special attributes associated with the files; that is, it was not necessary to define specific quota for each of these areas and files could be added to groups for as long as there was still free storage space on the disk. The early Apple Macintosh also featured a flat file system, the Macintosh File System. It was unusual in that the file management program (Macintosh Finder) created the illusion of a partially hierarchical filing system on top of EMFS. This structure required every file to have a unique name, even if it appeared to be in a separate folder. IBM DOS/360 and OS/360 store entries for all files on a disk pack (volume) in a directory on the pack called a Volume Table of Contents (VTOC). While simple, flat file systems become awkward as the number of files grows and makes it difficult to organize data into related groups of files. A recent addition to the flat file system family is Amazon's S3, a remote storage service, which is intentionally simplistic to allow users the ability to customize how their data is stored. The only constructs are buckets (imagine a disk drive of unlimited size) and objects (similar, but not identical to the standard concept of a file). Advanced file management is allowed by being able to use nearly any character (including '/') in the object's name, and the ability to select subsets of the bucket's content based on identical prefixes. File systems and operating systems Many operating systems include support for more than one file system. Sometimes the OS and the file system are so tightly interwoven that it is difficult to separate out file system functions. There needs to be an interface provided by the operating system software between the user and the file system. This interface can be textual (such as provided by a command line interface, such as the Unix shell, or OpenVMS DCL) or graphical (such as provided by a graphical user interface, such as file browsers). If graphical, the metaphor of the folder, containing documents, other files, and nested folders is often used (see also: directory and folder). Unix and Unix-like operating systems Unix-like operating systems create a virtual file system, which makes all the files on all the devices appear to exist in a single hierarchy. This means, in those systems, there is one root directory, and every file existing on the system is located under it somewhere. Unix-like systems can use a RAM disk or network shared resource as its root directory. Unix-like systems assign a device name to each device, but this is not how the files on that device are accessed. Instead, to gain access to files on another device, the operating system must first be informed where in the directory tree those files should appear. This process is called mounting a file system. For example, to access the files on a CD-ROM, one must tell the operating system "Take the file system from this CD-ROM and make it appear under such-and-such directory." The directory given to the operating system is called the mount point – it might, for example, be . The directory exists on many Unix systems (as specified in the Filesystem Hierarchy Standard) and is intended specifically for use as a mount point for removable media such as CDs, DVDs, USB drives or floppy disks. It may be empty, or it may contain subdirectories for mounting individual devices. Generally, only the administrator (i.e. root user) may authorize the mounting of file systems. Unix-like operating systems often include software and tools that assist in the mounting process and provide it new functionality. Some of these strategies have been coined "auto-mounting" as a reflection of their purpose. In many situations, file systems other than the root need to be available as soon as the operating system has booted. All Unix-like systems therefore provide a facility for mounting file systems at boot time. System administrators define these file systems in the configuration file fstab (vfstab in Solaris), which also indicates options and mount points. In some situations, there is no need to mount certain file systems at boot time, although their use may be desired thereafter. There are some utilities for Unix-like systems that allow the mounting of predefined file systems upon demand. Removable media allow programs and data to be transferred between machines without a physical connection. Common examples include USB flash drives, CD-ROMs, and DVDs. Utilities have therefore been developed to detect the presence and availability of a medium and then mount that medium without any user intervention. Progressive Unix-like systems have also introduced a concept called supermounting; see, for example, the Linux supermount-ng project. For example, a floppy disk that has been supermounted can be physically removed from the system. Under normal circumstances, the disk should have been synchronized and then unmounted before its removal. Provided synchronization has occurred, a different disk can be inserted into the drive. The system automatically notices that the disk has changed and updates the mount point contents to reflect the new medium. An automounter will automatically mount a file system when a reference is made to the directory atop which it should be mounted. This is usually used for file systems on network servers, rather than relying on events such as the insertion of media, as would be appropriate for removable media. Linux Linux supports numerous file systems, but common choices for the system disk on a block device include the ext* family (ext2, ext3 and ext4), XFS, JFS, and btrfs. For raw flash without a flash translation layer (FTL) or Memory Technology Device (MTD), there are UBIFS, JFFS2 and YAFFS, among others. SquashFS is a common compressed read-only file system. Solaris Solaris in earlier releases defaulted to (non-journaled or non-logging) UFS for bootable and supplementary file systems. Solaris defaulted to, supported, and extended UFS. Support for other file systems and significant enhancements were added over time, including Veritas Software Corp. (journaling) VxFS, Sun Microsystems (clustering) QFS, Sun Microsystems (journaling) UFS, and Sun Microsystems (open source, poolable, 128 bit compressible, and error-correcting) ZFS. Kernel extensions were added to Solaris to allow for bootable Veritas VxFS operation. Logging or journaling was added to UFS in Sun's Solaris 7. Releases of Solaris 10, Solaris Express, OpenSolaris, and other open source variants of the Solaris operating system later supported bootable ZFS. Logical Volume Management allows for spanning a file system across multiple devices for the purpose of adding redundancy, capacity, and/or throughput. Legacy environments in Solaris may use Solaris Volume Manager (formerly known as Solstice DiskSuite). Multiple operating systems (including Solaris) may use Veritas Volume Manager. Modern Solaris based operating systems eclipse the need for volume management through leveraging virtual storage pools in ZFS. macOS macOS (formerly Mac OS X) uses the Apple File System (APFS), which in 2017 replaced a file system inherited from classic Mac OS called HFS Plus (HFS+). Apple also uses the term "Mac OS Extended" for HFS+. HFS Plus is a metadata-rich and case-preserving but (usually) case-insensitive file system. Due to the Unix roots of macOS, Unix permissions were added to HFS Plus. Later versions of HFS Plus added journaling to prevent corruption of the file system structure and introduced a number of optimizations to the allocation algorithms in an attempt to defragment files automatically without requiring an external defragmenter. Filenames can be up to 255 characters. HFS Plus uses Unicode to store filenames. On macOS, the filetype can come from the type code, stored in file's metadata, or the filename extension. HFS Plus has three kinds of links: Unix-style hard links, Unix-style symbolic links, and aliases. Aliases are designed to maintain a link to their original file even if they are moved or renamed; they are not interpreted by the file system itself, but by the File Manager code in userland. macOS 10.13 High Sierra, which was announced on June 5, 2017 at Apple's WWDC event, uses the Apple File System on solid-state drives. macOS also supported the UFS file system, derived from the BSD Unix Fast File System via NeXTSTEP. However, as of Mac OS X Leopard, macOS could no longer be installed on a UFS volume, nor can a pre-Leopard system installed on a UFS volume be upgraded to Leopard. As of Mac OS X Lion UFS support was completely dropped. Newer versions of macOS are capable of reading and writing to the legacy FAT file systems (16 and 32) common on Windows. They are also capable of reading the newer NTFS file systems for Windows. In order to write to NTFS file systems on macOS versions prior to Mac OS X Snow Leopard third party software is necessary. Mac OS X 10.6 (Snow Leopard) and later allow writing to NTFS file systems, but only after a non-trivial system setting change (third party software exists that automates this). Finally, macOS supports reading and writing of the exFAT file system since Mac OS X Snow Leopard, starting from version 10.6.5. OS/2 OS/2 1.2 introduced the High Performance File System (HPFS). HPFS supports mixed case file names in different code pages, long file names (255 characters), more efficient use of disk space, an architecture that keeps related items close to each other on the disk volume, less fragmentation of data, extent-based space allocation, a B+ tree structure for directories, and the root directory located at the midpoint of the disk, for faster average access. A journaled filesystem (JFS) was shipped in 1999. PC-BSD PC-BSD is a desktop version of FreeBSD, which inherits FreeBSD's ZFS support, similarly to FreeNAS. The new graphical installer of PC-BSD can handle / (root) on ZFS and RAID-Z pool installs and disk encryption using Geli right from the start in an easy convenient (GUI) way. The current PC-BSD 9.0+ 'Isotope Edition' has ZFS filesystem version 5 and ZFS storage pool version 28. Plan 9 Plan 9 from Bell Labs treats everything as a file and accesses all objects as a file would be accessed (i.e., there is no ioctl or mmap): networking, graphics, debugging, authentication, capabilities, encryption, and other services are accessed via I/O operations on file descriptors. The 9P protocol removes the difference between local and remote files. File systems in Plan 9 are organized with the help of private, per-process namespaces, allowing each process to have a different view of the many file systems that provide resources in a distributed system. The Inferno operating system shares these concepts with Plan 9. Microsoft Windows Windows makes use of the FAT, NTFS, exFAT, Live File System and ReFS file systems (the last of these is only supported and usable in Windows Server 2012, Windows Server 2016, Windows 8, Windows 8.1, and Windows 10; Windows cannot boot from it). Windows uses a drive letter abstraction at the user level to distinguish one disk or partition from another. For example, the path represents a directory on the partition represented by the letter C. Drive C: is most commonly used for the primary hard disk drive partition, on which Windows is usually installed and from which it boots. This "tradition" has become so firmly ingrained that bugs exist in many applications which make assumptions that the drive that the operating system is installed on is C. The use of drive letters, and the tradition of using "C" as the drive letter for the primary hard disk drive partition, can be traced to MS-DOS, where the letters A and B were reserved for up to two floppy disk drives. This in turn derived from CP/M in the 1970s, and ultimately from IBM's CP/CMS of 1967. FAT The family of FAT file systems is supported by almost all operating systems for personal computers, including all versions of Windows and MS-DOS/PC DOS, OS/2, and DR-DOS. (PC DOS is an OEM version of MS-DOS, MS-DOS was originally based on SCP's 86-DOS. DR-DOS was based on Digital Research's Concurrent DOS, a successor of CP/M-86.) The FAT file systems are therefore well-suited as a universal exchange format between computers and devices of most any type and age. The FAT file system traces its roots back to an (incompatible) 8-bit FAT precursor in Standalone Disk BASIC and the short-lived MDOS/MIDAS project. Over the years, the file system has been expanded from FAT12 to FAT16 and FAT32. Various features have been added to the file system including subdirectories, codepage support, extended attributes, and long filenames. Third parties such as Digital Research have incorporated optional support for deletion tracking, and volume/directory/file-based multi-user security schemes to support file and directory passwords and permissions such as read/write/execute/delete access rights. Most of these extensions are not supported by Windows. The FAT12 and FAT16 file systems had a limit on the number of entries in the root directory of the file system and had restrictions on the maximum size of FAT-formatted disks or partitions. FAT32 addresses the limitations in FAT12 and FAT16, except for the file size limit of close to 4 GB, but it remains limited compared to NTFS. FAT12, FAT16 and FAT32 also have a limit of eight characters for the file name, and three characters for the extension (such as .exe). This is commonly referred to as the 8.3 filename limit. VFAT, an optional extension to FAT12, FAT16 and FAT32, introduced in Windows 95 and Windows NT 3.5, allowed long file names (LFN) to be stored in the FAT file system in a backwards compatible fashion. NTFS NTFS, introduced with the Windows NT operating system in 1993, allowed ACL-based permission control. Other features also supported by NTFS include hard links, multiple file streams, attribute indexing, quota tracking, sparse files, encryption, compression, and reparse points (directories working as mount-points for other file systems, symlinks, junctions, remote storage links). exFAT exFAT has certain advantages over NTFS with regard to file system overhead. exFAT is not backward compatible with FAT file systems such as FAT12, FAT16 or FAT32. The file system is supported with newer Windows systems, such as Windows XP, Windows Server 2003, Windows Vista, Windows 2008, Windows 7, Windows 8, and Windows 10. exFAT is supported in macOS starting with version 10.6.5 (Snow Leopard). Support in other operating systems is sparse since implementing support for exFAT requires a license. exFAT is the only file system that is fully supported on both macOS and Windows that can hold files larger than 4 GB. OpenVMS MVS Prior to the introduction of VSAM, OS/360 systems implemented a hybrid file system. The system was designed to easily support removable disk packs, so the information relating to all files on one disk (volume in IBM terminology) is stored on that disk in a flat system file called the Volume Table of Contents (VTOC). The VTOC stores all metadata for the file. Later a hierarchical directory structure was imposed with the introduction of the System Catalog, which can optionally catalog files (datasets) on resident and removable volumes. The catalog only contains information to relate a dataset to a specific volume. If the user requests access to a dataset on an offline volume, and they have suitable privileges, the system will attempt to mount the required volume. Cataloged and non-cataloged datasets can still be accessed using information in the VTOC, bypassing the catalog, if the required volume id is provided to the OPEN request. Still later the VTOC was indexed to speed up access. Conversational Monitor System The IBM Conversational Monitor System (CMS) component of VM/370 uses a separate flat file system for each virtual disk (minidisk). File data and control information are scattered and intermixed. The anchor is a record called the Master File Directory (MFD), always located in the fourth block on the disk. Originally CMS used fixed-length 800-byte blocks, but later versions used larger size blocks up to 4K. Access to a data record requires two levels of indirection, where the file's directory entry (called a File Status Table (FST) entry) points to blocks containing a list of addresses of the individual records. AS/400 file system Data on the AS/400 and its successors consists of system objects mapped into the system virtual address space in a single-level store. Many types of objects are defined including the directories and files found in other file systems. File objects, along with other types of objects, form the basis of the AS/400's support for an integrated relational database. Other file systems The Prospero File System is a file system based on the Virtual System Model. The system was created by Dr. B. Clifford Neuman of the Information Sciences Institute at the University of Southern California. RSRE FLEX file system - written in ALGOL 68 The file system of the Michigan Terminal System (MTS) is interesting because: (i) it provides "line files" where record lengths and line numbers are associated as metadata with each record in the file, lines can be added, replaced, updated with the same or different length records, and deleted anywhere in the file without the need to read and rewrite the entire file; (ii) using program keys files may be shared or permitted to commands and programs in addition to users and groups; and (iii) there is a comprehensive file locking mechanism that protects both the file's data and its metadata. Limitations Converting the type of a file system It may be advantageous or necessary to have files in a different file system than they currently exist. Reasons include the need for an increase in the space requirements beyond the limits of the current file system. The depth of path may need to be increased beyond the restrictions of the file system. There may be performance or reliability considerations. Providing access to another operating system which does not support the existing file system is another reason. In-place conversion In some cases conversion can be done in-place, although migrating the file system is more conservative, as it involves a creating a copy of the data and is recommended. On Windows, FAT and FAT32 file systems can be converted to NTFS via the convert.exe utility, but not the reverse. On Linux, ext2 can be converted to ext3 (and converted back), and ext3 can be converted to ext4 (but not back), and both ext3 and ext4 can be converted to btrfs, and converted back until the undo information is deleted. These conversions are possible due to using the same format for the file data itself, and relocating the metadata into empty space, in some cases using sparse file support. Migrating to a different file system Migration has the disadvantage of requiring additional space although it may be faster. The best case is if there is unused space on media which will contain the final file system. For example, to migrate a FAT32 file system to an ext2 file system. First create a new ext2 file system, then copy the data to the file system, then delete the FAT32 file system. An alternative, when there is not sufficient space to retain the original file system until the new one is created, is to use a work area (such as a removable media). This takes longer but a backup of the data is a nice side effect. Long file paths and long file names In hierarchical file systems, files are accessed by means of a path that is a branching list of directories containing the file. Different file systems have different limits on the depth of the path. File systems also have a limit on the length of an individual filename. Copying files with long names or located in paths of significant depth from one file system to another may cause undesirable results. This depends on how the utility doing the copying handles the discrepancy. See also Comparison of file systems Disk quota List of file systems List of Unix commands Directory structure Disk sharing Distributed file system Distributed Data Management Architecture File manager File system fragmentation Filename extension Global filesystem Object storage Physical and logical storage Storage efficiency Virtual file system Notes References Sources Further reading Books Prabhakaran, Vijayan (2006). IRON File Systems. PhD dissertation, University of Wisconsin-Madison. Online Benchmarking Filesystems (outdated) by Justin Piszcz, Linux Gazette 102, May 2004 Benchmarking Filesystems Part II using kernel 2.6, by Justin Piszcz, Linux Gazette 122, January 2006 Filesystems (ext3, ReiserFS, XFS, JFS) comparison on Debian Etch 2006 Interview With the People Behind JFS, ReiserFS & XFS Journal File System Performance (outdated): ReiserFS, JFS, and Ext3FS show their merits on a fast RAID appliance Journaled Filesystem Benchmarks (outdated): A comparison of ReiserFS, XFS, JFS, ext3 & ext2 Large List of File System Summaries (most recent update 2006-11-19) Linux File System Benchmarks v2.6 kernel with a stress on CPU usage Linux large file support (outdated) Local Filesystems for Windows Overview of some filesystems (outdated) Sparse files support (outdated) External links Interesting File System Projects

Operating System (OS)

Minix 3 Minix 3 is a project to create a small, high availability, high functioning Unix-like operating system. It is published under a BSD-3-Clause license and is a successor project to the earlier versions, Minix 1 and 2. The main goal of the project is for the system to be fault-tolerant by detecting and repairing its own faults on the fly, with no user intervention. The main uses of the system are envisaged to be embedded systems and education. , MINIX 3 supports IA-32 and ARM architecture processors. It can also run on emulators or virtual machines, such as Bochs, VMware Workstation, Microsoft Virtual PC, Oracle VirtualBox, and QEMU. A port to PowerPC architecture is in development. The distribution comes on a live CD and can be downloaded as a live USB stick image. The latest release is "minix_R3.4.0rc6-d5e4fc0.iso.bz2" (9 May 2017). MINIX 3 is believed to have inspired the Intel Management Engine (ME) OS found in Intel's Platform Controller Hub starting with the introduction of ME 11 which is used with Skylake and Kaby Lake processors. Its use in the Intel ME could make it the most widely used OS on x86/AMD64 processors starting , with more installations than Microsoft Windows, Linux, or macOS. Goals of the project Reflecting on the nature of monolithic kernel based systems, where a driver (which has, according to MINIX creator Tanenbaum, approximately 3–7 times as many bugs as a usual program) can bring down the whole system, MINIX 3 aims to create an operating system that is a "reliable, self-healing, multiserver Unix clone". To achieve that, the code running in kernel must be minimal, with the file server, process server, and each device driver running as separate user-mode processes. Each driver is carefully monitored by a part of the system named the reincarnation server. If a driver fails to respond to pings from this server, it is shut down and replaced by a fresh copy of the driver. In a monolithic system, a bug in a driver can easily crash the whole kernel. This is far less likely to occur in MINIX 3. History MINIX 3 was publicly announced on 24 October 2005 by Andrew Tanenbaum during his keynote speech on top of the Association for Computing Machinery (ACM) Symposium Operating Systems Principles conference. Although it still serves as an example for the new edition of Tanenbaum and Woodhull's textbook, it is comprehensively redesigned to be "usable as a serious system on resource-limited and embedded computers and for applications requiring high reliability." Initially released under the same BSD-3-Clause license that MINIX was licensed under since 2000. In late 2005, the copyright owner was changed and a fourth clause was added. Reliability policies One of the main goals of MINIX 3 is reliability. Below, some of the more important principles that enhance its reliability are discussed. Reduce kernel size Monolithic operating systems such as Linux and FreeBSD and hybrids like Windows have millions of lines of kernel code. In contrast, MINIX 3 has about 6,000 lines of executable kernel code, which can make problems easier to find in the code. Cage the bugs In monolithic kernels, device drivers reside in the kernel. Thus, when a new peripheral is installed, unknown, untrusted code is inserted in the kernel. One bad line of code in a driver can bring down the system. Instead, in MINIX 3, each device driver is a separate user-mode process. Drivers cannot execute privileged instructions, change the page tables, perform arbitrary input/output (I/O), or write to absolute memory. They must make kernel calls for these services and the kernel checks each call for authority. Limit drivers' memory access In monolithic kernels, a driver can write to any word of memory and thus accidentally corrupt user programs. In MINIX 3, when a user expects data from, for example, the file system, it builds a descriptor telling who has access and at what addresses. It then passes an index to this descriptor to the file system, which may pass it to a driver. The file system or driver then asks the kernel to write via the descriptor, making it impossible for them to write to addresses outside the buffer. Survive bad pointers Dereferencing a bad pointer within a driver will crash the driver process, but will have no effect on the system as a whole. The reincarnation server will restart the crashed driver automatically. Users will not notice recovery for some drivers (e.g., disk and network) but for others (e.g., audio and printer), they might. In monolithic kernels, dereferencing a bad pointer in a driver normally leads to a system crash. Tame infinite loops If a driver gets into an infinite loop, the scheduler will gradually lower its priority until it becomes idle. Eventually the reincarnation server will see that it is not responding to status requests, so it will kill and restart the looping driver. In a monolithic kernel, a looping driver could hang the system. Limit damage from buffer overflows MINIX 3 uses fixed-length messages for internal communication, which eliminates certain buffer overflows and buffer management problems. Also, many exploits work by overrunning a buffer to trick the program into returning from a function call using an overwritten stack return address pointing into attacker controlled memory, usually the overrun buffer. In MINIX 3, this attack is mitigated because instruction and data space are split and only code in (read-only) instruction space can be executed, termed executable space protection. However, attacks which rely on running legitimately executable memory in a malicious way (return-to-libc, return-oriented programming) are not prevented by this mitigation. Restrict access to kernel functions Device drivers obtain kernel services (such as copying data to users' address spaces) by making kernel calls. The MINIX 3 kernel has a bit map for each driver specifying which calls it is authorized to make. In monolithic kernels, every driver can call every kernel function, authorized or not. Restrict access to I/O ports The kernel also maintains a table telling which I/O ports each driver may access. Thus, a driver can only touch its own I/O ports. In monolithic kernels, a buggy driver can access I/O ports belonging to another device. Restrict communication with OS components Not every driver and server needs to communicate with every other driver and server. Accordingly, a per-process bit map determines which destinations each process may send to. Reincarnate dead or sick drivers A special process, called the reincarnation server, periodically pings each device driver. If the driver dies or fails to respond correctly to pings, the reincarnation server automatically replaces it with a fresh copy. Detecting and replacing non-functioning drivers is automatic, with no user action needed. This feature does not work for disk drivers at present, but in the next release the system will be able to recover even disk drivers, which will be shadowed in random-access memory (RAM). Driver recovery does not affect running processes. Integrate interrupts and messages When an interrupt occurs, it is converted at a low level to a notification sent to the appropriate driver. If the driver is waiting for a message, it gets the interrupt immediately; otherwise it gets the notification the next time it does a RECEIVE to get a message. This scheme eliminates nested interrupts and makes driver programming easier. Architecture As can be seen, at the bottom level is the microkernel, which is about 4,000 lines of code (mostly in C, plus a small amount of assembly language). It handles interrupts, scheduling, and message passing. It also supports an application programming interface (API) of about 30 kernel calls that authorized servers and drivers can make. User programs cannot make these calls. Instead, they can issue POSIX system calls which send messages to the servers. The kernel calls perform functions such as setting interrupts and copying data between address spaces. At the next level up, there are the device drivers, each one running as a separate userland process. Each one controls some I/O device, such as a disk or printer. The drivers do not have access to the I/O port space and cannot issue I/O instructions directly. Instead, they must make kernel calls giving a list of I/O ports to write to and the values to be written. While there is a small amount of overhead in doing this (typically 500 ns), this scheme makes it possible for the kernel to check authorization, so that, for example, the audio driver cannot write on the disk. At the next level there are the servers. This is where nearly all the operating system functionality is located. User processes obtain file service, for example, by sending messages to the file server to open, close, read, and write files. In turn, the file server gets disk I/O performed by sending messages to the disk driver, which controls the disk. One of the key servers is the reincarnation server. Its job is to poll all the other servers and drivers to check on their health periodically. If a component fails to respond correctly, or exits, or gets into an infinite loop, the reincarnation server (which is the parent process of the drivers and servers) kills the faulty component and replaces it with a fresh copy. In this way the system is automatically made self-healing without interfering with running programs. Currently the reincarnation server, the process server, and the microkernel are part of the trusted computing base. If any of them fail, the system crashes. Nevertheless, reducing the trusted computing base from 3-5 million lines of code, as in Linux and Windows systems, to about 20,000 lines greatly enhances system reliability. Differences between MINIX 3 and prior versions MINIX 1.0, 1.5, and 2.0 were developed as tools to help people learn about the design of operating systems. MINIX 1.0, released in 1987, was 12,000 lines of C and some x86 assembly language. Source code of the kernel, memory manager, and file system of MINIX 1.0 are printed in the book. Tanenbaum originally developed MINIX for compatibility with the IBM PC and IBM PC/AT microcomputers available at the time. MINIX 1.5, released in 1991, included support for MicroChannel IBM PS/2 systems and was also ported to the Motorola 68000 and SPARC architectures, supporting the Atari ST, Commodore Amiga, Apple Macintosh and Sun Microsystems SPARCstation computer platforms. A version of MINIX running as a user process under SunOS was also available. MINIX 2.0, released in 1997, was only available for the x86 and Solaris-hosted SPARC architectures. Minix-vmd was created by two Vrije Universiteit researchers, and added virtual memory and support for the X Window System. MINIX 3 does the same, and provides a modern operating system with many newer tools and many Unix applications. Prof. Tanenbaum once said: Many improvements have also been made in the structure of the kernel since the MINIX 2 release, making the system more reliable. MINIX version 3.1.5 was released 5 Nov 2009. It contains X11, Emacs, vi, cc, GCC, Perl, Python, Almquist shell, Bash, Z shell, FTP client, SSH client, Telnet client, Pine, and over 400 other common Unix utility programs. With the addition of X11, this version marks the transition away from a text-only system. Another feature of this version, which will be improved in future ones, is the ability of the system to withstand device driver crashes, and in many cases having them automatically replaced without affecting running processes. In this way, MINIX is self-healing and can be used in applications demanding high reliability. MINIX 3.2.0 was released in February 2012. This version has many new features, including the Clang compiler, experimental symmetric multiprocessing support, procfs and ext2fs filesystem support, and GNU Debugger (GDB). Several parts of NetBSD are also integrated in the release, including the bootloader, libc and various utilities and other libraries. MINIX 3.3.0 was released in September 2014. This release is the first version to support the ARM architecture in addition to x86. It also supports a NetBSD userland, with thousands of NetBSD packages running right out of the box. Mascot Rocky Raccoon is the mascot of MINIX 3. MINIXCon MINIXCon is a conference on sharing talks, efforts and researches related to MINIX. It was held once in 2016. MINIXCon2017 was cancelled due lack of talks submitted. See also Comparison of operating system kernels MINIX file system List of computing mascots :Category:Computing mascots Notes References Further reading Building a dependable operating system: fault tolerance in MINIX 3 by Jorrit N. Herder (PDF) Reorganizing Unix for Reliability by Jorrit N. Herder, Herbert Bos, Ben Gras, Philip Homburg, and Andrew S. Tanenbaum (PDF) Modular system programming in MINIX 3 by Jorrit N. Herder, Herbert Bos, Ben Gras, Philip Homburg, and Andrew S Tanenbaum (PDF) J. N. Herder et al., Modular System Programming in MINIX 3, ;Login, April 2006 (PDF) Pablo A Pessolani. MINIX4RT: A Real-Time Operating System Based on MINIX Building Performance Measurement Tools for the MINIX 3 Operating System, by Rogier Meurs (PDF) Design and implementation of the MINIX virtual file system (PDF) Reference manual for MINIX 3 Kernel API (PDF) Towards a true microkernel operating system (PDF) Construction of a Highly Dependable Operating System (PDF) Minix 3 and the microkernel experience: Smart Kernel by Rüdiger Weis (PDF) Safe and Automatic Live Update by Cristiano Giuffrida (PDF) External links Wiki Source code minix3.ru comp.os.minix – official forum (since 1987) Description of Minix 3 by Andy Tanenbaum MINIX: what is it, and why is it still relevant? An interview with Andy Tanenbaum Minix Network Service Documentation Can We Make Operating Systems Reliable and Secure? A reimplementation of NetBSD based on a microkernel MINIX 3 on ARM by Kees Jongenburger Lessons Learned from 30 Years of MINIX By Andrew S. Tanenbaum 2005 software Computer science in the Netherlands Computing platforms Educational operating systems Information technology in the Netherlands Microkernels MINIX Operating system distributions bootable from read-only media

Operating System (OS)

Singularity (operating system) Singularity is an experimental operating system developed by Microsoft Research between July 9, 2003, and February 7, 2015. It was designed as a high dependability OS in which the kernel, device drivers, and application software were all written in managed code. Internal security uses type safety instead of hardware memory protection. Operation The lowest-level x86 interrupt dispatch code is written in assembly language and C. Once this code has done its job, it invokes the kernel, which runtime system and garbage collector are written in Sing# (an extended version of Spec#, itself an extension of C#) and runs in unprotected mode. The hardware abstraction layer is written in C++ and runs in protected mode. There is also some C code to handle debugging. The computer's basic input/output system (BIOS) is invoked during the 16-bit real mode bootstrap stage; once in 32-bit mode, Singularity never invokes the BIOS again, but invokes device drivers written in Sing#. During installation, Common Intermediate Language (CIL) opcodes are compiled into x86 opcodes using the Bartok compiler. Security design Singularity is a microkernel operating system. Unlike most historic microkernels, its components execute in the same address space (process), which contains software-isolated processes (SIPs). Each SIP has its own data and code layout, and is independent from other SIPs. These SIPs behave like normal processes, but avoid the cost of task-switches. Protection in this system is provided by a set of rules called invariants that are verified by static program analysis. For example, in the memory-invariant states there must be no cross-references (or memory pointers) between two SIPs; communication between SIPs occurs via higher-order communication channels managed by the operating system. Invariants are checked during installation of the application. (In Singularity, installation is managed by the operating system.) Most of the invariants rely on the use of safer memory-managed languages, such as Sing#, which have a garbage collector, allow no arbitrary pointers, and allow code to be verified to meet a given computer security policy. Project status The first Singularity Research Development Kit (RDK), RDK 1.1, was initially released on March 4, 2008, being released under a shared source license allowing academic non-commercial use and available from CodePlex. RDK 2.0 was later released on November 14, 2008. Similar projects Inferno, first created in 1995, based on Plan 9 from Bell Labs; programs are run in a virtual machine and written in Limbo instead of C# with CIL JavaOS, a legacy OS based on the same concept as Singularity JNode, an OS similar in concept to Singularity, but with Java instead of C# with CIL JX, a Java OS that, like Singularity, uses type safety instead of computer hardware memory protection Phantom OS, a managed OS SharpOS, a former effort to write an operating system using C#; open-source software MOSA, a .NET Framework compiler and operating system using C# Cosmos, a building blocks toolkit for developing an OS using C#; open-source software TempleOS, a ring-0 operating system with JIT compiler; open-source software See also Language-based system, general kernel design using language-based protection instead of hardware protection. Spec#, programming language derived from C# by adding Eiffel-like design by contract. Sing#, programming language derived from Spec# by adding channels and low-level constructs; used to build Singularity. Midori, a Microsoft-developed microkernel-based operating system mooted as a possible successor to Microsoft Windows by some members of the information technology (IT) press. Based on and related to Singularity. References External links Singularity Design Motivation and an overview of the Singularity Project Singularity source code on CodePlex Singularity: A research OS written in C# an interview of the Channel 9 team to Jim Larus and Galen Hunt (video & thread) Singularity III: Revenge of the SIP, an interview of the Channel 9 team to 3 researchers of the Singularity Project Team (video & thread). Singularity IV: Return of the UI, a demo of Singularity actually running (video & thread). Singularity Revisited, an interview of the Channel 9 team to 4 researchers of the Singularity Project Team (video & thread) Microsoft operating systems Microsoft Research Microkernel-based operating systems Microkernels .NET Operating system distributions bootable from read-only media

Operating System (OS)

Time Sharing Operating System Time Sharing Operating System, or TSOS, is a discontinued operating system for RCA mainframe computers of the Spectra 70 series. TSOS was originally designed in 1968 for the Spectra 70/46, a modified version of the 70/45. TSOS quickly evolved into the Virtual Memory Operating System (VMOS) by 1970. VMOS continued to be supported on the later RCA 3 and RCA 7 computer systems. RCA was in the computer business until 1971 when it sold its computer business to Sperry Corporation. Sperry renamed TSOS to VS/9 and continued to market it into the early 1980s. In the mid seventies, an enhanced version of TSOS called BS2000 was offered by the German company Siemens. While Sperry – now Unisys – discontinued VS/9, the BS2000 variant, now called BS2000/OSD, is still offered by Fujitsu and used by their mainframe customers primarily in Germany and other European countries. As the name suggests, TSOS provided time sharing features. Beyond that it provided a common user interface for both time sharing and batch, which was a big advantage over IBM's OS/360 or its successors MVS, OS/390 and z/OS. See also Timeline of operating systems References External links TSOS manuals at Bitsavers Time-sharing operating systems Proprietary operating systems Discontinued operating systems UNIVAC software 1968 software

Operating System (OS)

Newton OS Newton OS is a discontinued operating system for the Apple Newton PDAs produced by Apple Computer, Inc. between 1993 and 1997. It was written entirely in C++ and trimmed to be low power consuming and use the available memory efficiently. Many applications were pre-installed in the ROM of the Newton (making for quick start-up) to save on RAM and flash memory storage for user applications. Features Newton OS features many interface elements that the Macintosh system software didn't have at the time, such as drawers and the "poof" animation. An animation similar to this is found in Mac OS X, and parts of the Newton's handwriting recognition system have been implemented as Inkwell in Mac OS X. Sound responsive — Clicking menus and icons makes a sound; this feature was later introduced in Mac OS 8. Icons - Similar to the Macintosh Desktop metaphor, Newton OS uses icons to open applications. Tabbed documents — Similar to tabbed browsing in today's browsers and Apple's At Ease interface, documents titles appear in a small tab at the top right hand of the screen. Screen rotation — In Newton 2.0, the screen can be rotated to be used for drawing or word processing. File documents — Notes and Drawings can be categorized. E.g. Fun, Business, Personal, etc. Print documents — Documents on the Newton can be printed. Send documents — Documents can be sent to another Newton via Infrared technology or sent using the Internet by E-Mail, or faxed. Menus — Similar to menus seen in Mac OS, but menu titles are instead presented at the bottom of the screen in small rectangles, making them similar to buttons with attached "pop-up" menus. Many features of the Newton are best appreciated in the context of the history of Pen computing. Software Shortly after the Newton PDA's release in 1993, developers were not paying much attention to the new Newton OS API and were still more interested in developing for the Macintosh and Windows platforms. It was not until two years later that developers saw a potential market available to them in creating software for Newton OS. Several programs were made by third-party developers, including software to enhance the disappointing hand writing recognition technology of Newton OS 1.x. The basic software that came with Newton OS: Works — A program for drawing and word processing, with typical capabilities such as: rulers, margins, page breaks, formatting, printing, spell checking and find & replace tools. Notes — Used for checklists, as well as both drawing and writing in the same program either with a newton keyboard or a stylus pen. Dates — Calendar program where you can schedule appointments and other special events. Names — Program for storing extensive contacts information in a flexible format. Formulas — Program that offers metric conversions, currency conversions, loan and mortgage calculators, etc. Calculator — A basic calculator with square root, percentage, MR, M+ and M- functions additional to the basic functions found on a calculator. Clock — A small floating window type application, known as a desktop accessory on the Macintosh. The Newton clock also includes features for an alarm, minute timer and the date. Book Reader — Support for displaying electronic books is built in. Version history Handwriting recognition The Newton uses the CalliGrapher word-based handwriting recognition engine developed by ParaGraph International Inc, led by former Soviet scientist Stepan Pachikov. The earliest versions had weaknesses that resulted in bad publicity and reviews. However, with the release of Newton PDAs based upon version 2.0 of the OS, the handwriting recognition substantially improved, partially being a product of ParaGraph and an Apple-created recognizer pair: Apple's Rosetta and Mondello. Newton's handwriting recognition, particularly the print recognizer, has been considered by many reviewers, testers, and users to be the best in the industry, even 10 years after it was introduced. It was developed by Apple's Advanced Technology Group, and was described in 2012 as "the world's first genuinely usable handwriting recognition system". The Newton can recognize hand-printed text, cursive, or a mix of the two, and can also accept free-hand "Sketches", "Shapes", and "ink text". Text can also be entered by tapping with the stylus on a small on-screen pop-up QWERTY keyboard. With "Shapes", Newton can recognize that the user was attempting to draw a circle, a line, a polygon, etc., and it cleans them up into "perfect" vector representations (with modifiable control points and defined vertices) of what the user is attempting to draw. "Shapes" and "Sketches" can be scaled or deformed once drawn. "Ink text" captures the user's free-hand writing but allows it to be treated somewhat like recognized text when manipulating for later editing purposes ("ink text" supported word wrap, could be formatted to be bold, italic, etc.). At any time a user can also direct the Newton to recognize selected "ink text" and turn it into recognized text (deferred recognition). A Newton Note document (or the notes attached to each contact in Names and each calendar event) can contain any mix of interleaved text, ink text, Shapes, and Sketches. NewtonScript Newton OS runs applications written in C++, along with an interpreted, user-friendly language called NewtonScript. These applications are stored in packages. See also Apple Newton eMate 300 Pen computing iOS Motorola Marco Notes A selection of PDFs of Apple's Newton manuals Newton FAQ Pen Computing's First Look at Newton OS 2.0 The Newton Hall of Fame: People behind the Newton Pen Computing's Why did Apple kill the Newton? Pen Computing's Newton Notes column archive A.I. Magazine article by Yaeger on Newton HWR design, algorithms, & quality and associated slides Info on Newton HWR from Apple's HWR Technical Lead References External links Additional resources & information NewtonTalk discussion email list Einstein: a Newton emulator CalliGrapher handwriting recognition software Annotated bibliography of references to handwriting recognition and pen computing Reviews MacTech's review of MessagePad 2000 MessagePad 2000 review at "The History and Macintosh Society" Prof. Wittmann's collection of Newton & MessagePad reviews CNET compares a MessagePad to a Samsung Q1 UMPC Apple Inc. operating systems Apple Newton ARM operating systems Discontinued operating systems 1993 software

Operating System (OS)

End system In networking jargon, a computer connected to a computer network is sometimes referred to as an end system or end station, because it sits at the edge of the network. The end user directly interacts with an end system that provides information or services. End systems that are connected to the Internet are also referred to as internet hosts; this is because they host (run) internet applications such as a web browser or an email retrieval program. The Internet's end systems include some computers with which the end user does not directly interact. These include mail servers, web servers, or database servers. With the emergence of the internet of things, household items (such as toasters and refrigerators) as well as portable, handheld computers and digital cameras are all being connected to the internet as end systems. End systems are generally connected to each other using switching devices known as routers rather than using a single communication link. The path that transmitted information takes from the sending end system, through a series of communications links and routers, to the receiving end system is known as a route or path through the network. The sending and receiving route can be different, and can be reallocated during transmission due to changes in the network topology. Normally the cheapest or fastest route is chosen. For the end user the actual routing should be completely transparent. See also Communication endpoint Data terminal equipment End instrument Host (network) Node (networking) Terminal (telecommunication) References Computing terminology Internet architecture

Operating System (OS)

Computer operator A computer operator is a role in IT which oversees the running of computer systems, ensuring that the machines, and computers are running properly. The job of a computer operator as defined by the United States Bureau of Labor Statistics is to "monitor and control ... and respond to ... enter commands ... set controls on computer and peripheral devices. This Excludes Data Entry." Overview The position has evolved from its beginnings in the punched card era. A Bureau of Labor Statistics report published in 2018 showed that, in the public sector, a major employer of those categorized as Computer Operator was United States Postal Service. In the private sector, companies involved in data processing, hosting, or related services employed computer operators at an even higher rate. The states in the USA with the highest employment for computer operators, as of 2018, are: New York, Texas, California, New Jersey, and Florida. Job role description The former role of a computer operator was to work with mainframe computers which required a great deal of management day-to-day including manually running batch jobs; however, now they often work with a variety of different systems and applications. The computer operator normally works in a server room or a data center, but can also work remotely so that they can operate systems across multiple sites. Most of their duties are taught on the job, as their job description will vary according to the systems and set-up they help manage. A computer operator can work inside the home on the network editing domains and nets, or they can work on the road or as part of a company. Responsibilities of a computer operator may include: Monitor and control electronic computer and peripheral electronic data processing equipment to process business, scientific, engineering, and other data according to operating instructions. Monitor and respond to operating and error messages. May enter commands at a computer terminal and set controls on computer and peripheral devices. Excludes "Computer Occupations" (15-1100) and "Data Entry Keyers" (43-9021). The role also includes maintaining records and logging events, listing each backup that is run, each machine malfunction and program abnormal termination. Operators assist system administrators and programmers in testing and debugging of new systems and programs prior to their becoming production environments. Modern-day computing has led to a greater proliferation of personal computers, with a rapid change from older mainframe systems to newer self-managing systems. This is reflected in the operator's role. Tasks may include managing the backup systems, cycling tapes or other media, filling and maintaining printers. Overall the operator fills in as a lower level system administrator or operations analyst. Most operations departments work 24x7. A computer operator also has knowledge of disaster recovery and business continuity procedures. Formerly, this would have meant sending physical data tapes offsite, but now the data is more than likely transmitted over computer networks. Specializations Console operator A console operator interacts with a multi-user system's console entering commands via a keyboard replying to requests for information taking actions such as mounting computer tapes that were "pulled" by a tape librarian supervising a tape operator, especially when there is a a non-specific mount request. These individuals would be trained to use specialized equipment related to their duties. Beyond the IBM System/360 era One example of specific hardware used by a console operator is the IBM 3066 Model 2 system console, which included a light pen as an interface device. Other then-new features were: replaced "most switch, pushbutton, and indicator functions" as with the 165's Model 1, had a microfiche document viewer,<>the online manual has an extra dot: "d.ocument"</ref> a feature introduced for the 360/85's console. A console printer (up to 85 characters per second) to provide hard copy was optional when the console was in display mode, and required when it was in printer-keyboard mode. Peripherals operator A peripherals operator uses dedicated peripheral equipment connected to computer(s) such as printers, scanners, or storage devices for data transfer to and/or from computers. Tape operator Historically, tape operators were in charge of swapping out reels of paper tape, reels of magnetic tape or magnetic tape cartridges that stored computer data or instructions. Card reader operator Depending on the type of card reader, either the "9-edge" or the "12-edge" was towards the card reader operator inserting the cards - but the deck of cards was always placed face down. The United States Army's wordings were: Load cards in hopper face down, 12 edge out, column 1 to the left (1977) Place cards in hopper face down with 12 edge to operator (1981) 12 edge / face down : IBM orientation. nine-edge (also face down) : some other card readers. Printer operator In addition to filing or delivering computer printouts, a printer operator at times loads standard or, as directed by a console operator or a remote console, specialized forms. Tab operator The tab operator (short for tabulating) would be responsible for preparing and operating tabulating machines to produce statistical results. Hardware such as the IBM 08x sorter series were called tabulating equipment. The 1980 census specifically counted Tab operators ("Tabulating-machine operator"). Tape librarian A tape librarian is responsible for the management, storage, and reporting involving data storage tapes. The tape librarian would develop and/or maintain an organization system for the storage and retrieval of tapes, and assist in disaster recovery. Additionally, the librarian would ensure the integrity of the tapes, and submit recommendations for replacement when needed. Some examples of equipment a tape librarian may work with are the IBM 3850. Gallery Worldwide Computer operator positions are advertised worldwide. See also System administration References Computer occupations

Operating System (OS)

MTS system architecture MTS System Architecture describes the software organization of the Michigan Terminal System, a time-sharing computer operating system in use from 1967 to 1999 on IBM S/360-67, IBM System/370, and compatible computers. Overview The University of Michigan Multi-Programming Supervisor (UMMPS), has complete control of the hardware and manages a collection of job programs. One of the job programs is MTS, the job program with which most users interact. MTS operates as a collection of command language subsystems (CLSs). One of the CLSs allows for the execution of user programs. MTS provides a collection of system subroutines that are available to CLSs, user programs, and MTS itself. Among other things these system subroutines provide standard access to Device Support Routines (DSRs), the components that perform device dependent input/output. Organization The system is organized as a set of independent components with well-defined interfaces between them. This idea is, of course, neither new nor unique; but MTS components are generally larger, interfaces between components more rigid, and a component communicates with fewer other components than in many systems. As a result, components are more independent of each other and it is easier to replace one component without affecting others. The interface with the supervisor is the same for all components and very few special cases are allowed; for example, all input/output operations are done using the same supervisor facilities whether the input/output is for a card reader, a paging device, or any other device. Most access to supervisor services is via system subroutines that issue the necessary Supervisor Call instructions (SVCs) rather than by direct use of SVCs. Control blocks are accessed only indirectly by calls to subroutines within the component that "owns" the control block. The interfaces used by user programs are the cleanest of all. User programs may never refer directly to any system control block (neither for reference nor change), because the virtual memory segment(s) that contain system control blocks (the system segments) are removed from a job's virtual address space when a user mode program is running. The subroutine interfaces available to user programs are also used by most other parts of the system (system mode programs, CLSs, ...) even through components running in system mode do have access to the "system" virtual memory segment(s). Transitions from user mode to system mode and back are managed by a special protected set of subroutine interfaces known as "the gate" (initially developed at Wayne State University). The programming effort for MTS is divided vertically rather than horizontally. This means that one or two individuals are assigned responsibility for a component and then follow it from design through implementation and maintenance. The responsible person has considerable freedom to design the internal structure of the component and even extend interfaces, so long as all appropriate existing interfaces are maintained unchanged. Programming languages and system level debugging The supervisor, most job programs, large parts of MTS including many DSRs and CLSs are written in 360/370 assembler language. A few job programs and portions of MTS including some DSRs and CLSs are written in higher level languages such as Plus or GOM. User programs are written in a wide range of languages from assembler to any of the higher level languages that are available. Most components of the system, including user programs, CLSs, and subroutines loaded in shared virtual memory, can be debugged and new versions of many can be installed while the system is running without requiring a system shutdown. It is possible to substitute a private copy of all components except the supervisor and parts of some job programs. A "test" version of the MTS job program (TMTS) is available to allow testing in the regular production environment. SWAT is an interface that allows the Symbolic Debugging System, which is normally used to debug user programs, to be used to debug MTS. $PEEK is a privileged MTS command that uses Program Event Recording (PER) and other facilities to facilitate debugging one job program from another. Components that cannot be debugged in this way can be debugged by running in an MTS virtual machine (a user program). Supervisor University of Michigan Multi-Programming Supervisor (UMMPS) is the name of the MTS supervisor. UMMPS is the only portion of the system that runs in S/360 supervisor state. It runs with virtual memory (relocation) turned off and with hardware interrupts disabled. With multi-processor configurations it may be executing on more than one processor concurrently. UMMPS is what today would be called a microkernel, although UMMPS was developed long before that term was in common use. To jobs UMMPS appears to be an extension of the S/360 or S/370 hardware and is responsible for: allocating all hardware resources (processors, real memory, input/output devices), scheduling I/O operations, processing all hardware interrupts including page-faults and program interrupts due to errors in job programs, implementing virtual memory including: the allocation of VM addresses, managing segment and page tables, providing protected or read-only memory by setting storage keys, managing memory reference and change bits, managing named address spaces (NASs), determining when and which pages should be moved between real memory and secondary storage to implement demand paging, providing services to job programs that issue Supervisor Call (SVC) and Monitor call (MC) instructions, including: starting and terminating jobs, initiation of input/output operations (channel programs), scheduling timer interrupts, communication with the system operator, providing inter-task communication services, allowing jobs to acquire and release software locks, allowing jobs to enter and leave user and system mode, where user mode programs do not have access to some virtual memory segments and the full range of SVCs, providing services to allow the synchronization of job programs, providing shadow segment and page tables and other services that allow job programs to provide virtual machine services, simulating a few machine instructions that are present on some, but not all, models of the S/360 or S/370 computers, simulating the Branch on Program Interrupt (BPI) pseudo instructions, machine check error recovery, writing job dumps (making a snapshot of the current execution state of a job by writing out all real memory, all the job's virtual memory, general registers, and program status word to magnetic tape), tracking the amount of processor time used and the number of page-ins for jobs, maintaining the time of day clock, and assisting in the creation of diagnostic trace tapes. After initialization UMMPS is entirely interrupt driven. The interrupts may be due to supervisor (SVC) or monitor (MC) call instructions issued by job programs to request services, page fault interrupts for virtual memory pages that are not in real memory when referenced by a job program, program interrupts caused by abnormal conditions in job programs, timer interrupts on behalf of job programs or used internally within the supervisor, interrupts from the input/output subsystem, machine check interrupts, external (operator initiated) interrupts, and interrupts from other processors in a multiprocessor configuration. A program interrupt in supervisor state is a system failure that results in a supervisor dump (a Super Dump, where the machine state and the contents of all real memory is written to magnetic tape) followed by a system restart (re-IPL). Branch on Program Interrupt (BPI) The Branch on Program Interrupt (BPI) pseudo instruction provides a simple way for a sequence of code to retain control following a program interrupt. This can be useful to test for valid addresses in a parameter list, to catch overflow, underflow, and other exceptions during calculations, or really any situation where a program interrupt is possible. BPIs can be used at very low cost for the usually more common case where there is no program interrupt. UMMPS implements the Branch on Program Interrupt (BPI) pseudo instruction using a special type of NOP instruction. The form of the BPI instruction is: BPI M2,D2(B2) [RX] or BC 0,D2(M2,B2) [RX] Op Code Mask1 Mask2 Base Displacement +--------------+-------+-------+-------+------------+ | x'47' | 0 | M2 | B2 | D2 | +--------------+-------+-------+-------+------------+ 0 8 12 16 20 31 Where Mask1 is always zero, Mask2 is a name or value as described in the table below, and the base and displacement specify a branch address. Several BPI instructions may be given in succession. The BPI instruction is available for use in problem-state as well as supervisor-state (that is, within UMMPS itself). When an instruction causes a program interrupt, the following instruction is checked to determine if it is a BPI instruction. If it is, the type of program interrupt that occurred is compared with the type categories specified in the Mask2 portion of the BPI instruction. If there is a match, the condition code is set to reflect the interrupt that occurred and the branch is taken. Otherwise, the next instruction is checked to determine if it is a BPI instruction, etc. If there is no BPI transfer made (either because there was no BPI instruction or because the program interrupt type did not match the mask of any BPIs that were present), the normal processing of the program interrupt occurs. When the BPI instruction is executed normally (when there is no program interrupt on the previous instruction), it is a NOP or "branch never" instruction. BPI interrupt-type categories: {| class="Wikitable" !Mask2Name !Mask2Value !InterruptNumber !InterruptName !Condition Codeon Branch |- | |- align="center" |OPCD |8 |1 |Operation |1 |- align="center" | | |2 |Privileged operation |2 |- align="center" | | |3 |Execute |3 |- | |- align="center" |OPND |4 |4 |Protection |0 |- align="center" | | |5 |Addressing |1 |- align="center" | | |6 |Specification |2 |- align="center" | | |7 |Data |3 |- | |- align="center" |OVDIV |2 |8 |Fixed overflow |0 |- align="center" | | |9 |Fixed divide |1 |- align="center" | | |10 |Decimal overflow |2 |- align="center" | | |11 |Decimal divide |3 |- | |- align="center" |FP |1 |12 |Exponent overflow |0 |- align="center" | | |13 |Exponent underflow |1 |- align="center" | | |14 |Significance |2 |- align="center" | | |15 |Floating-point divide |3 |} Job programs All job programs run in S/360 problem state, may run with virtual addressing enabled or disabled, and may or may not be reentrant (more than one instance of the job program may or may not be allowed to execute). With multiprocessor configurations a single job will only execute on a single processor at a time, but the supervisor may assign a job to different processors at different times. The MTS job program is the one with which most users interact and provides command interpretation, execution control, file and device management, and accounting services. Other job programs assist the supervisor (the Paging Device Processor or PDP, the OPERATOR console job, the Disk Manager or DMGR, ...), provide common or shared services (spooled local and remote batch services via HASP and the HASPlings or later the Resource Manager or RM which was developed at the University of British Columbia to replace HASP), or allow the system operators to display status and otherwise control the system (JOBS, UNITS, STOP, BLAST, GOOSE, STARTUP, SHUTDOWN, REW, WTM, ...). New jobs, other than the very first job, are started by requests to UMMPS from other jobs, most often the OPERATOR job. The very first job, INIT, is started immediately after IPL and supervisor initialization. 24, 31, and 32-bit addressing From their start and for much of their lifetime UMMPS and MTS operated using 24-bit addressing. UMMPS never used the 32-bit virtual memory addresses that were available on the IBM S/360-67. In August 1982 the University of Alberta changed UMMPS to operate in 31-bit addressing mode to allow more than 16 MB of real memory to be used, although real memory above 16 MB was only used for to hold virtual memory pages. Job programs and user programs continued to use 24-bit addresses. In 1985 Rensselaer Polytechnic Institute (RPI) made changes to UMMPS to support S/370-XA which among other things allowed either 24 or 31-bit addressing for job programs and for user programs running under MTS. Changes were made at the University of Michigan in 1990 to allow user programs using 31-bit addresses to work smoothly: object modules could be flagged as supporting 31-bit addressing (or not), compilers and assemblers were changed to supply the correct flags, programs would switch between 24 and 31-bit addressing modes as needed when transitioning between system and user modes. Protection MTS has a strong protection model that uses the virtual memory hardware and the S/360 and S/370 hardware's supervisor and problem states and via software divides problem state execution into system (privileged or unprotected) and user (protected or unprivileged) modes. Relatively little code runs in supervisor state. For example, Device Support Routines (DSRs, aka device drivers) are not part of the supervisor and run in system mode in problem state rather than in supervisor state. Virtual memory and paging Virtual memory (VM) and demand paging support were added to UMMPS in November 1967, making MTS the first operating system to use the Dynamic Address Translation (DAT) features that were added to the IBM S/360-67. UMMPS uses 4096-byte virtual memory pages and 256-page virtual memory segments. UMMPS could be conditionally assembled to use the small (64 page) segments that were available on S/370 hardware, but job programs were always presented with what appeared to be large (256 page) segments. Both 2K and 4K block storage keys are supported. There is a three-level storage hierarchy: (1) real memory, (2) high-speed paging devices, and (3) paging disks. High-speed paging devices include the IBM 2301 Drum, IBM 2305 Fixed Head File, and various third party "solid-state" I/O devices such as the STC 4305 and Intel 3805 that simulate spinning disks or more often provide more efficient fixed block architecture (FBA) access to external RAM-based storage. The high-speed paging devices are attached using "two-byte" I/O channels operating at up to 3.0 MB per second whenever possible. The paging disks were separate from the disks used for the file system and were used if the higher speed paging devices became full. Virtual memory pages migrate between real memory and the paging devices. In the early versions of MTS pages did not migrate between individual paging devices. In later versions, less frequently used pages would migrate from the high-speed paging devices to the paging disks, when the high-speed devices were close to being full. Later in its life the system was changed to use IBM S/370-XA Extended Storage as part of the second level of the storage hierarchy and to use the same disks for the file system and for paging. Virtual memory is managed by UMMPS with assistance from the Paging Device Processor (PDP) job program. UMMPS responds to requests to allocate and free VM from job programs, allocates VM addresses, allocates real memory, manages segment and page tables, sets storage keys, manages reference and change bits, determines which virtual memory pages should be paged in or out, and communicates with the PDP. New virtual memory pages are initialized to a "core constant" value of x'81' on first reference. The PDP is a real memory job program. It allocates space on the paging devices, initiates all I/O to the paging devices, is responsible for recovery from I/O errors, and communicates with UMMPS. To reduce the likelihood of thrashing UMMPS uses a "big job mechanism" that identifies jobs with more real pages than a threshold, limits the number of these "big" jobs that are eligible to execute at a given time, and gives the big jobs an extended time slice when they do execute. This allows big jobs to accumulate more real memory pages and to make better use of those pages before they come to time slice end, but big jobs will wait longer between time slices when there are too many big jobs contending for limited real memory pages. The number of pages that a job can have before it is considered big (the big job threshold or BJT) and the number of big jobs (NBJ) that are eligible for execution are external parameters that are reevaluated and set outside of the supervisor every 20 seconds based on the overall system load. Other than the big job mechanism, UMMPS storage, processor, and I/O scheduling are independent, with each area allowed to "take care of itself". Virtual memory is divided into regions as follows: Segment 0: shared virtual equals real memory (read-only) Segments 1 to 4: shared virtual memory (read-only) Segment 5: private virtual memory (system segment, only available to system mode (unprotected) programs) Segments 6 to 12: private virtual memory (user segments, read-write to any program) Different numbers of segments were assigned to the various regions over time and with the advent of 31-bit addressing and the ability to use VM segments larger than 16, the regions were expanded as follows: Segment 0: shared virtual equals real memory (read-only) Segments 1 to 5: shared virtual memory (read-only) Segments 6-7: private virtual memory (system segments, only available to system mode (unprotected) programs) Segment 8: shared virtual memory for attachment of named address spaces (NASs) (read-only) Segments 9-55: private virtual memory (user segments, read-write to any program) Segments 56-59: private virtual memory (system segments, only available to system mode (unprotected) programs) Segments 60-63: shared virtual memory for attachment of named address spaces (NASs) (read-only) Some real memory is not addressable using virtual memory addresses and so is only available to UMMPS or real memory job programs. Read-only virtual memory may be changed by privileged programs that turn memory protection off (usually for very limited periods of time). Named address spaces (NASs) allow the attachment of named segments of virtual memory. They are shared virtual memory spaces that may be attached and detached from a given job's virtual address space and the same addresses may have different contents depending on which named address spaces are attached. NAS support is mostly used by MTS to attach VM segments preloaded with system components as a way to extend shared virtual memory without using VM address space below the magic 16 MB line and thus keeping more of this valuable address space available for use by 24-bit user programs. Signon and project IDs Everybody who uses MTS is assigned a signon ID (also called userids or Computing Center IDs, CCIDs). Signon IDs are always 4 characters long. If necessary shorter IDs are automatically padded on the right using the string ".$.". Thus, the IDs "MTS.", "DAB.", "ME$." or "C.$." could be written as "MTS", "DAB", "ME" and "C", respectively. Signon IDs are protected using passwords which must be given at the start of each session (as part of or more often immediately after the $SIGNON command). Exceptions are jobs submitted via *BATCH* that run under the same ID that submitted the new job, jobs scheduled to run repeatedly at a particular time or on a particular day when the jobs run under the same ID that scheduled them, or jobs initiated from the operator's console. Passwords are from 1 to 12 characters long, lower case letters are converted to uppercase, special characters other than comma and blank are allowed. Passwords can be changed using the $SET PW command. Changing a password from a terminal session requires entering the original password, and the new password must be entered twice for verification. Entering an incorrect password is counted and reported to the user at the next successful signon. Too many password failures without a successful entry are reported to the system operator and still more password failures without a successful entry will cause the signon ID to be "locked out" until it is reset by business office staff. A short delay is introduced between failed password entry attempts to prevent large numbers of password "guesses" from being made quickly. Individuals can have multiple sign on IDs for use in different courses, different research projects, or with different funding sources (university, government, non-profit, industry, ...). The sharing of signon IDs by individuals is discouraged, but does occur. Signon IDs are grouped into projects. Each signon ID is a member of one and only one project. Project IDs, like signon IDs, are 4 characters long. Many projects are controlled by a "Project Leader" signon ID which can allocate resources to the accounts that are members of the project (within the resource limits allocated to the project) using the $ACCOUNTING MANAGEMENT command. Signon and project IDs are also used to control access to files and to send e-mail. With one exception there are no signon IDs with "special" privileges by virtue of the ID itself. Instead, flags can be set that allow specific signon IDs to: create public files and set public program keys, run with a zero or negative account balance, perform privileged operations, including: flagging files to run in system (unprotected) rather than user (protected) mode by default, use the PROT=OFF options on the $SET and $RUN commands, use the test command language subsystem ($#CLS), use privileged options of the $SYSTEMSTATUS and other command language subsystems (CLSs). The exception is the signon ID "MTS.", which can read, but not modify or permit, any file in the system regardless of ownership or permit status. The MTS. ID can also use the $SET FILEREF=OFF option, which prevents the file reference dates on files from being updated (useful when recovering from file system problems or investigating security issues). There is no ability for a program or user to assume the privileges of a signon ID other than the one that was used to sign on to the current session. Instead, programs and files may be permitted to specific signon IDs, projects, and program keys or to combinations of signon IDs, projects, and program keys. Terminal, batch, and server sessions MTS supports terminal, batch, and server sessions. All three use the same command language. Terminal sessions are interactive with the user able to respond to the output produced including error messages and prompts. Batch jobs are not interactive and so all input needs to be prepared in advance with little or no opportunity for the user to alter the input (at least not without programming) once the batch job starts to execute. Server sessions can support user to MTS or client to MTS interactions and while there may be interaction with the user, MTS commands are usually read from a command file and the user is not likely to have to know or enter MTS commands. Server sessions can be sponsored in which case they will appear to be free to the user, and do not require that the user enter an ID and password. Server sessions can also be charged for and require a valid ID and password. Server sessions can be initiated from the network or from within an MTS session using the $MOUNT command. The University of Alberta developed a Student Oriented Batch Facility in 1971 to provide quick job turnaround for undergrad students learning to program in FORTRAN, ALGOL, PL/C, and 360 Assembler. It was a dedicated punch card input, printer output system that provided 5 minute turn around and ran several thousands of jobs a week at a fixed cost per job (15 cents). Command language MTS reads commands from the *SOURCE* pseudo device, which is initially the user's terminal or the batch input stream. Programs may execute MTS commands by calling the CMD, CMDNOE, and COMMAND subroutines. Leading and trailing blanks as well as null and all blank lines are ignored. Lines that start with an asterisk (* or $*) are treated as comments. Command lines that end with a continuation character (by default the minus-sign) are continued on the next line. Command lines may be up to 255 characters long. MTS uses keyword oriented commands and command options. The command verb (SIGNON, RUN, EDIT, ...) is the first keyword on the command line. Commands may start with an optional dollar-sign ($SIGNON, $RUN, $EDIT, ...). In batch jobs, following invalid commands and some other errors, MTS looks for the next line that starts with a dollar-sign ($) in column 1 as the next command to execute. All commands and most command options allow initial sub-string abbreviations (C for COPY, R for RUN, DEB for DEBUG, ...). MTS commands and most command options are case-insensitive. MTS has "one-shot" commands (CREATE, FILESTATUS, SIGNOFF, ...) and commands that have sub-command modes (EDIT, CALC, SYSTEMSTATUS, ...). Most commands with sub-command modes can also be invoked as one-shot commands by giving one or more sub-commands on the command line. All MTS jobs start with a SIGNON command and most end with a SIGNOFF command. Commands may be stored in files and executed using the SOURCE command. Commands may be stored in signon-files (sigfiles) or project-signon-files (projectsigfiles) that are always executed immediately after the SIGNON command. The execution of sigfiles may be required (SIGFILEATTN=OFF) or optional (SIGFILEATTN=ON, the default). Global control SIGNON { ccid | * } [ option ... ] [ comment ] SIGNOFF [ SHORT | $ | LONG ] [ RECEIPTS | NORECEIPTS ] ACCOUNTING [ option ... ] ACCOUNTING MANAGEMENT COMMENT [ text ] DISPLAY item [ OUTPUT=FDname ] SET option ... SINK [ FDname | PREVIOUS ] SOURCE [ FDname | PREVIOUS ] SYSTEMSTATUS [ option ] #CLS FDname [ options ] (privileged command that runs a test CLS) File management CREATE filename [ SIZE={ n | nP } ] [MAXSIZE={n | nP} ] [TYPE={LINE | SEQ | SEQWL} ] DESTROY filelist [ OK | ALLOK | PROMPT ] DUPLICATE oldname [ AS | TO ] newname [ options ] [ OK | ALLOK | PROMPT ] EDIT [ filename ] [ :edit-command ] EMPTY [ filelist ] [ OK | ALLOK | PROMPT ] TRUNCATE filelist [ ALLOK | PROMPT ] RENAME oldname [ AS ] newname [ OK | ALLOK | PROMPT ] RENUMBER filelist [ first [ last [ begin [ increment ] ] ] ] [ ALLOK | PROMPT ] FILESTATUS [ filelist ] [ format ] [ items ] FILEMENU [ filelist ] [ items ] FMENU [ filelist ] [ items ] PERMIT filelist [ access [ accessor ] ] PERMIT filelist LIKE filelist2 [ EXCEPT access [ accessor ] ] LOCK filename [ how ] [ WAIT | NOWAIT ] [ QUIT | NOQUIT ] UNLOCK filename LOCKSTATUS [ filename | JOB nnnnnn ] [ LOCK ] [ WAIT ] LSTATUS [ filename | JOB nnnnnn ] [ LOCK ] [ WAIT ] File and device management COPY [ FROM ] { FDlist1 | 'string' } [ [ TO ] [ FDlist2 ] CREATE *pdn* TYPE={ PRINT | IMPORT | EXPORT | DUMMY } DESTROY *pdn* [ OK | ALLOK | PROMPT ] LIST FDlist [ [ ON | TO ] FDname ] [ [ WITH ] option ... ] LIST FDlist WITH options [ {ON | TO} FDname ] LIST MOUNT [ request [; request ] ... ] CANCEL *...* [ [ JOB ] nnnnnn ] [ {ID | CCID}=ccid ] RELEASE { *PRINT* | *PUNCH* | *BATCH* | *pdn* } LOCATE { SYSTEM | LOCAL | FULL | SHORT | HELP } LOCATE { jobnumber | jobname } [ option ... ] VIEW [ jobnumber [ ; view-command ] ] LOG [ FDname1 ] { [ ON ] FDname2 [ format ] [ options ] | OFF } FTP [ hostname ] GET FDname (old fashioned and obsolete, but sometimes still useful) NUMBER (old fashioned and obsolete way to enter data into a file) User program execution and control RUN [ FDname ] [ I/Ounits ] [ option ] ... [ PAR=parameters ] RERUN [ ECHO | NOECHO ] [ I/Ounits ] [ option ] ... [ PAR=parameters ] DEBUG [ FDname ] [ I/Ounits ] [ option ] ... [ PAR=parameters ] SDS [ sds-command ] LOAD [ FDname ] [ I/Ounits ] [ option ] ... [ PAR=parameters ] START [ [ AT ] [ RF={hhhhhh | GRx} ] location ] [ I/Ounits ] [ option ] ... RESTART [ [ AT ] location ] [ I/Ounits ] [ option ] ... UNLOAD [ CLS=clsname ] ALTER location value ... ... DISPLAY [ format ] location [ OUTPUT=FDname ] DUMP [ format ] [ OUTPUT=FDname ] IF RUNRC condition integer, MTS-command ERRORDUMP (obsolete command, causes an automatic dump in batch mode following abnormal termination of a user program) Miscellaneous CALC [ expression ] MESSAGESYSTEM [ message-command ] FSMESSAGE [ FSMessage-command ] NET [ host | *pdn* ] [ .network-command ] HEXADD [ hexnumber1 ] [ hexnumber2 ] (obsolete, replaced by $Calc) HEXSUB [ hexnumber1 ] [ hexnumber2 ] (obsolete, replaced by $Calc) PASSWORD (obsolete, removed, allowed changes to public files before true shared file access was available) File-name patterns Several MTS commands that use file names or lists of file names allow the use of file-name patterns: COPY, DESTROY, DUPLICATE, EMPTY, EDIT, FILESTATUS, FILEMENU, LIST, LOCKSTATUS, PERMIT, RENAME, RENUMBER, and TRUNCATE. A question-mark (?) is the pattern match character. A single question-mark used in a file-name will match zero or more characters. "?" matches all files for the current signon ID, "?.S" matches all files that end with ".S", "A?B" matches all files that begin with "A" and end with "B", "A?B?C" matches all files that start with "A", end with "C", and contain a "B". Two or more consecutive question-marks match "n-1" characters. "???.S" matches all four character file-names that end with ".S", and "????" matches all three character file-names. "W163:?" matches all files under the signon ID "W163" to which the current user has some access. Command Macros The MTS command macro processor allows users to define their own MTS commands. It provides a "scripting" language with conditional commands and is available for use with any lines read from *SOURCE* by user programs or command language sub-systems as well with MTS commands. Macro processor lines are usually prefixed with the greater than character (>). The command macro processor is controlled using the $SET command as well as by I/O modifiers on FDnames. Prefix Characters To help users keep track of what command, command subsystem, or program they are working with and when input is expected, MTS displays a prefix character or sometimes a prefix string at the front of each input and output line it writes to the user's terminal. The common prefixes are: # MTS command mode #- MTS command continuation mode ? Prompts > COPY and LIST commands . Program loader blank User programs : Editor + Symbolic Debugging System (SDS) @ Message System ftp> FTP (File-Transfer) Command language subsystems The MTS job program is always executing one of several command language subsystems or CLSs. Many of the MTS commands are built into MTS and execute as part of the MTS CLS. User programs execute as the USER CLS. The USER CLS has a special relationship to the Symbolic Debugging System (SDS CLS) when the debugger is active. Other MTS commands are implemented as separate modules, confusingly also named command language subsystems or CLSs, that may be executed from shared virtual memory or may be loaded from files. These separate CLSs each have their own four character name and they execute as a separate CLS in the original sense of the term. Many, but not all, of these CLSs provide their own separate sub-command language. There are $SET command options to cause old or new versions of CLSs rather than the current versions to be used. There is an option on the $UNLOAD command to unload a CLS (free the virtual memory it is using, close any FDnames and release any devices or pseudo devices that it has open). Only one CLS is executing at a time, but one CLS of each type may be active and it is possible to switch from one CLS to another without exiting or unloading the original CLS and then to later return to the original CLS and continue working from where one left off. CLSs that have their own sub-commands usually support a STOP command to exit from the CLS, an MTS and/or a RETURN command to return to the calling CLS or MTS command mode, and commands that begin with a dollar-sign ($) are executed as MTS commands with an immediate return to the original CLS. All CLSs except for the USER CLS execute in system mode in problem state. Limited-service state MTS sessions normally operate in "full-service state", but during times of extreme system overload terminal sessions may be placed into "limited-service state" (LSS). The LSS mechanism is manually enabled by the system operator and is normally only used when the hardware system is operating at reduced capacity due to a malfunction. A terminal session is placed into LSS if LSS has been enabled by the system operator and the system is overloaded at signon. LSS sessions may only issue MTS commands and run programs with a short local time limit. Rather than giving all users poor performance, LSS limits the size of the tasks that some users may perform to relatively small tasks such as editing of files and reading of messages in order to allow other users to receive reasonable performance on larger tasks. Users may request that their session be changed to full-service state ($SET LSS=OFF) and such requests are granted if the system is not overloaded at the time the request is made. Command statistics Each MTS command that is issued is recorded, first to a disk file and later to magnetic tape. This information is only available to staff and is used to investigate software problems, security problems, rebate requests, and to provide statistics about how the command language is used. User programs User program refers to a program run by the user and which is not necessarily a program that belongs to or that was created by a user. User programs may be supplied in public files, in files available under the OLD: or NEW: signon IDs, in files belonging to other users and permitted for use by others, or user programs may be developed by the current user in files that they own. User programs are executed using the $RUN, $RERUN, and $DEBUG commands or less often using the $LOAD and $START commands. The $RESTART command may be used to restart execution of a program following an attention interrupt that was not handled by the program, a program interrupt that was not handled by the program (although restarting after a program interrupt usually does not work well), or following an explicit return to MTS from a call to the MTS subroutine. MTS loads programs using a dynamic linking loader (UMLOAD) that reads loader records (ESD, TXT, CSI, RDL, LCS, END, ...) from the file or device specified by the user and will selectively include subroutines from libraries supplied by the user, from system subroutine libraries such as *LIBRARY, and from system subroutines pre-loaded in shared virtual memory. MTS uses standard OS/360 loader records which makes it fairly easy for MTS to use compilers developed for use under other IBM operating systems. When a program starts execution a number of logical I/O units will be set either explicitly on the $RUN or other command or by default. Any text string given following the PAR= keyword is passed to the program as a parameter. By default user programs execute with the program key *EXEC, but a different program key may be set using the $CONTROL command. Programs may call a system subroutine to shorten the program key they are using or switch to the *EXEC program key thus temporary giving themselves less access to files, devices, and other services controlled using program keys. Programs may also call a system subroutine to lengthen or restore their program key according to some pre-established rules. MTS uses the standard S-type and, less often, R-type calling sequences used in OS/360. By default user programs execute in user mode in problem state. User mode programs do not have access to the system virtual memory segment and therefore have no access to system control blocks, may not call privileged system subroutines, and may not issue privileged supervisor calls (SVCs). User mode programs can issue non-privileged SVCs, but few programs do so directly and instead call system subroutines to obtain system services. User mode programs may call system subroutines that switch to system mode after checking that the protected service is allowed for the particular caller, there is a return to user mode when the system subroutine returns. Selected user programs can be flagged to run in system rather than user mode by staff with privileged signon IDs or staff with privileges can cause a user program to run in system mode using a keyword on the $RUN or $SET command. Device independent input/output All input/output requests, whether by the MTS job program itself or by a program running under MTS, is done using a common set of subroutine calls (GETFD, FREEFD, READ, WRITE, CONTROL, GDINFO, ATTNTRP, ...). The same subroutines are used no matter what program is doing the I/O and no matter what type of file or device is being used (typewriter or graphics terminal, line printer, card punch, disk file, magnetic and paper tape, etc.). No knowledge of the format or contents of system control blocks is required to use these subroutines. Programs may use specific characteristics of a particular device, but such programs will be somewhat less device independent. MTS input/output is record or line oriented. Programs read lines from a terminal, card reader, disk file, or tape and write lines to a terminal, printer, disk file, or tape. Conversion to and from ASCII/EBCDIC and end-of-line processing is usually done by a front end processor or Device Support Routine (DSR) and so is not a concern of most programs. While it is possible to do character I/O to a terminal by reading or writing single character lines, reading or writing many such very short lines is not very efficient. Each line read or written consists of from 0 to 32,767 bytes of data and an associated line number (a signed integer number scaled by 1000) giving the line's location. The length of each line read or written is given explicitly, so programs do not need to do their own processing of line ending characters (CR/LF, NL) or other terminators (null). Some devices support zero length lines, while others do not. For many files and devices the line number is simply a sequential count of the lines read, while some file types explicitly associate a specific line number with each line of the file, and in other cases the line number is synthesized from data that appears at the start of an input line or the line number can be prepended to an output line. File or device names Input/output is done directly by referencing a file or device by its name (FDname) or indirectly by referencing a logical I/O unit (SCARDS or INPUT, SPRINT or PRINT, SPUNCH or OBJECT, GUSER, SERCOM, 0 to 99). FDnames are assigned to logical I/O units using keywords in the command language or by default. FDnames can be a simple file name such as MYFILE, a simple device name prefixed with a greater than sign such as >T901, or a pseudo-device name such as *PRINT*. All FDnames are converted to uppercase before they are used, so like MTS commands, FDnames are case independent. I/O modifiers, line number ranges, and explicit concatenation can be used to create complex FDnames from simple FDnames. For example: FILE1@-TRIM (I/O modifier that retains trailing blanks) FILE2(1,10) (line number range that reads lines from 1 to 10 inclusive) FILE3+*SOURCE* (explicit concatenation) FILE4(1,10)@-TRIM+*TAPE*@-TRIM (all of the above in a single complex FDname) Pseudo device names Pseudo device names (PDNs) begin and end with an asterisk (e.g., *name*). Common pseudo devices include: *SOURCE* standard input (normally either a terminal or for batch jobs, the input queue); *SINK* standard output (normally a terminal or for batch jobs, a printer); *MSOURCE* master source, not re-assignable, usually a terminal or a card reader; *MSINK* master sink, not re-assignable, usually a terminal or a printer; *BATCH* spooled input to a new batch job; *PRINT* spooled output to a printer, same as *MSINK* for batch jobs; *PUNCH* spooled output to a card punch (until card punches were retired); and *DUMMY* all data written is discarded and all reads return an End-of-File (much like /dev/null for UNIX); and *AFD* the active file or device as established using the $GET command. The $SOURCE and $SINK commands may be used to reassign the FDnames assigned to *SOURCE* and *SINK*. The $MOUNT command assigns pseudo device names (e.g. *T22*, *NET*) to devices such as magnetic and paper tapes and network connections (including server connections). The $CREATE command can be used to create pseudo device names for use with BITNET import and export, for spooled print jobs, and for dummy devices. I/O modifiers I/O modifiers, possibly negated, may be associated with an FDname to modify default behaviors. An I/O modifier is specified by appending an at-sign followed by the modifier's name to an FDname. For example, *SOURCE*@UC would cause lines read from *SOURCE* to be converted to uppercase before they are presented to a program and MYFILE@UC@-TRIM would cause lines read from the file MYFILE to be converted to uppercase and any trailing spaces at the end of the line would be retained. Some commonly used I/O modifiers are: @S (sequential), @I (indexed), @FWD (forward), @BKWD (backward), @EBCD (EBCDIC), @BIN (binary), @UC (uppercase), @CC (logical carriage control), @MCC (machine carriage control), @NOCC (no carriage control), @TRIM (trim all but last training blank). Some I/O modifiers are processed in a device independent fashion by MTS and others are device dependent and processed by the Device Support Routines (DSRs). Not all files or devices support all I/O modifiers. Different files and devices have different default I/O modifiers and a few I/O modifier defaults can be changed using the $SET command. Line number ranges Specific parts of a file or device can be referenced by including starting and ending line numbers and possibly a line number increment in parentheses separated by commas. The line numbers and increment are integers scaled by 1000 and can be positive or negative (±nnnnn.nnn). For example, SIMPLE.F(-35,197.5) would open the file SIMPLE.F, starting at the first line number greater or equal to -35 and return an 'end of file' instead of the first line number greater than 197.5. One can also include line number increments—as an example: SIMPLE.F(2,200,2) would return all (and only) even line numbers between 2 and 200 (inclusive). The symbolic line numbers FIRST or *F, LAST or *L, MIN, and MAX may refer to the first, last, minimum possible, and maximum possible lines, respectively. For example, SIMPLE.F(*F,0) would refer to the 'negative' lines of the file SIMPLE.F. This is where programmers might place self-documentation for a (often binary) file, actual data in the file would start at line number 1. One can also do simple addition and subtraction with the symbolic line numbers: FIRST±m, *F±m, LAST±m, *L±m, MIN+m, MAX-m, where m is an integer with or without a decimal point scaled by 1000 (±nnnnn.nnn). So to add new lines to the end of an existing file one could use an FDname of the form SIMPLE.F(LAST+1). File or device concatenation Explicit concatenation allows FDnames to be connected using a plus-sign, as NAMEA+NAMEB. In this case MTS transparently returns the contents of NAMEA followed by the contents of NAMEB or writes to NAMEB after writing to NAMEA reaches an end of file or other error condition. Implicit concatenation occurs when an input line contains the string: $CONTINUE WITH FDname MTS will continue with the FDname given as the new source of data. Or, if a line of the form: $CONTINUE WITH FDname RETURN is read, MTS will return the contents of the new FDname until and End-of-File is reached and then return the next line of the original FDname (note that, a file that continues with itself causes an infinite loop, usually a mistake, but sometimes used to good effect). While the line starts with a dollar-sign, $CONTINUE WITH is not an MTS command, but rather a delimiter. The @IC I/O modifier and the command $SET IC={ON | OFF} can be used to control implicit concatenation. $ENDFILE lines If a line contains the string $ENDFILE, MTS returns a 'soft' end of file. While the line starts with a dollar-sign, $ENDFILE is not an MTS command, but rather a delimiter. The @ENDFILE I/O modifier and the command $SET ENDFILE={ALWAYS | SOURCE | NEVER} can be used to control $ENDFILE processing. $9700 and $9700CONTROL lines Lines that begin with the strings "$9700" or "$9700CONTROL" may be copied or written to *PRINT* to control print options on the Xerox 9700 page printer. $9700 lines take effect at the point where they occur, while $9700CONTROL lines apply to the entire print job in which they occur. While these lines have a form similar to MTS commands, they are really device commands and not true MTS commands. Files MTS files are stored as 4096 byte "pages" on one or more public or private disk volumes. Volumes have volume labels, volume numbers, and volume names (usually MTS001, MTS002, ..., MTSnnn). Disk volumes are stored on traditional cylinder-track-record and fixed block architecture (FBA) disk drives or at one time on the IBM 2321 Data Cell. Individual files do not span disk volumes. The maximum size of a file is limited to the free space available on the disk volume where it resides. By default, files are created one page in size, but a larger size as well as a maximum size may be specified ($CREATE name SIZE=nP MAXSIZE=nP). Files will automatically expand until they reach their maximum size or the disk space limit for the owner's signon ID is exceeded. Users may request that a file be created on a specific disk volume ($CREATE name VOLUME=name). MTS files fall into one of three categories: public files, user files, and temporary files: Public files are files whose names begin, but do not end, with an asterisk (e.g., *LIBRARY, *USERDIRECTORY). Public files, often called 'star files', are publicly available files that contain programs and data that are widely available to all users. For example, *LIBRARY is a library of commonly used system subroutines. In the earliest days of MTS public files were the only files that could be shared and then only as read-only files. Later, public files could be permitted and shared in the same fashion as any other files. User files are files whose names do not begin with an asterisk or a minus sign. They must be explicitly created ($CREATE) and destroyed ($DESTROY). They are owned by and initially permitted to just the userID that creates them, but they can be permitted for use by other userIDs using the $PERMIT command. To reference a file belonging to another user, the file name is prefixed with the owner's userID followed by a colon (e.g., W163:MYPROGRAM). There are charges for the amount of disk space used and most signon IDs have a maximum disk space limit. Temporary files are files whose names begin with a minus sign (e.g., -TEMP). Their names are unique within a single session. They are created implicitly on first use, are not charged for, do not count against a signon ID's disk space limit, and are automatically destroyed when the terminal or batch session ends. MTS doesn't implement directories, but there is a de facto two-tier grouping of files owing to the inclusion in a file's name of its owner's four-character MTS user ID. File names, like all FDnames, are converted to uppercase before use and so are case-insensitive. File types MTS supports three types of file, line files, sequential files, and sequential with line number files, but line files were by far the most common: Line files Line files ($CREATE name or $CREATE name TYPE=LINE) are line-oriented files which are indexed (and randomly accessible) by line number. Allowed line numbers are ±2147483.647—essentially a signed integer value divided by 1000, but command line references were limited to ±99999.999. Regular writes to a file increase the line number by 1. Lines are variable length, and a line can be rewritten to any length between 1 and the line length limit (originally 256, but later changed to 32767) without affecting the surrounding lines. Rewriting a pre-existing line to a length of zero deletes that line without affecting surrounding lines. By default the first line number written to an empty file is 1, and is incremented by 1 with each subsequent write. By default, reading a file starts with the first line number at or above 1 and continues by reading each line in order of increasing line numbers. This means that negative line numbers are 'invisible' parts of a file, which require specific references to read. There are commands (and system subroutines) to renumber lines. A contiguous set of lines can be renumbered to any combination of start and increment as long as lines of the file are not re-ordered. For example, if a file consists of lines 10, 20, 30, 40 and 50, lines 30–40 can be renumbered as 35,36, but not as 135,136, as that would change the sequence of lines. The line index and data are stored on separate disk pages except for the smallest (one page) files, where the line index and data are stored together. The $CREATE command creates line files by default. A side effect of the line-based file system is that programs can read and write individual lines incrementally. If one edits a file (usually a text file) with the MTS file editor ($EDIT), any changes made to lines are written immediately, as are insertions and deletions of specific lines. This makes it quite different from most (byte-oriented) file systems where a file is usually read into and changed in memory, and then saved to disk in bulk. Due to hardware or software problems, line files can become corrupt. The program *VALIDATEFILE checks the structure of line files. Sequential files Sequential files ($CREATE name TYPE=SEQ) are line-oriented files with the first line number being implicitly 1 and incremented by 1 for each line. Once written the length of a line (other than the last line of a file) can not be changed, although any line can be replaced by a line of the same length. Sequential files are generally only readable sequentially from start to end, or written by appending to the end. One can, however, request a reference for the current line of a sequential file, and use that reference to jump to that specific location again. Sequential files are somewhat more efficient in terms of space than line files and can be more efficient in terms of CPU time too when compared with large disorganized line files. But the main reason for the existence of SEQ files is that they supported long lines (up to 32,767 characters) before line files did. Sequential files were less common once line files could support long lines. Sequential files are also used to force new lines to be appended to the end of the file without the need to give the line number range (LAST+1). Sequential with line number files Sequential With Line Number files ($CREATE name TYPE=SEQWL) are similar to Sequential Files, except that their line numbers were explicitly stored. They have all the restrictions of Sequential Files, except that the line number could be specifically supplied when writing to a file (as long as it is greater than the last line number written to the file). Unlike Line Files, the first read of an SEQWL file returns the first line of the file, even if it was negative. SEQWL files were rarely used, and were not officially supported or were removed from the documentation by some MTS sites. Because line files did not work well with the Data Cell, SEQWL files were implemented as a way to allow the Data Cell to be used for longer term less expensive storage of files while still preserving line numbers. Shared files Over time the sharing of files between MTS users evolved in four stages. Stage one allowed for limited file sharing, where public or library files (files whose names start with an asterisk) were readable by all users and all other files (user files) could only be accessed by their owners. Public files were owned and maintained by Computing Center staff members, so at this stage only Computing Center files were shared. Stage two allowed for limited file sharing, where the program *PERMIT could be used to (i) make a file read-only (RO) to the file's owner and all other MTS users, (ii) make a file available for copying by members of the same project as the file's owner using the program *COPY, or (iii) make a file available for copying by all other users using the program *COPY. As for stage one, by default owners had unlimited access to their own files and the files were not accessible to other users. Stage three allowed for "really shared files", where the $PERMIT command or the PERMIT subroutine can be used to share a file in a variety of ways with lists of other users, projects, all other users, or a combination of these. The types of access that can be allowed are read, write-extend, write-change or empty, renumber or truncate, destroy, and permit. As for stages one and two, by default a user file is permitted with unlimited access for its owner and no access for others. A file's owner's access can also be changed, although an owner always retains permit access. The $FILESTATUS command or FILEINFO and GFINFO subroutines can be used to obtain a file's permit status. Stage four added program keys (PKeys) to the list of things to which a file can be permitted. Thus files can be permitted to users, projects, all other users, program keys, or a combination of these. Program keys were associated with MTS commands and files, which allowed files to be permitted to specific programs or to specific MTS commands. Among other things this allowed the creation of execute-only or run-only programs in MTS. Files can also be permitted to the initial sub-string of a userID, projectID, or program key. As a result, it may happen that a single userID, projectID, and program key may potentially have more than one type of access. In such cases, the actual access is resolved according to the following rules: (i) userIDs, alone or in combination with program keys, take precedence over projectIDs and program keys, ii) projectIDs, alone or in combination with program keys, take precedence over program keys, (iii) longer sub-string matches take precedence over shorter sub-string matches, and (iv) if there is no specific userID, projectID, or program key match then the access specified for "others" is used. The PKEY subroutine can be used to shorten the program key of the currently running program or switch the program key of the currently running program to *EXEC and later restore the program key, allowing a program to voluntarily limit the access it has to files by virtue of its program key. File locking As part of "really shared files" (stage three above), file locking was introduced to control simultaneous access to shared files between active MTS sessions (that is, between separate running tasks or processes). File locking does not limit or block access to files within a single MTS session (between command language subsystems or user programs running as part of the same MTS session). File locking in MTS is mandatory rather than advisory. Files are locked implicitly on first use of a particular type of access or explicitly using the $LOCK command or the LOCK subroutine. Files are unlocked implicitly when the last use of a file within a task is closed or explicitly using the $UNLOCK command or the UNLK subroutine. The $LOCKSTATUS command or LSFILE and LSTASK subroutines can be used to obtain a file's or a task's current lock status. A file may be "open", "not open", or "waiting for open" and "not locked", "locked for read", "locked for modify", "locked for destroy", "waiting for read", "waiting for modify", or "waiting for destroy". A file's open status is independent of its lock status. Locking a file for modification also locks the file for reading and locking a file for destroying also locks the file for modification and reading. Any number of tasks can have a file locked for reading at any given time, but only one task can have a file locked for modification at any given time and then only if no task has the file locked for reading, or locked for destroying. Only one task can have a file locked for destroying at any given time, and then only if no task has the file open, locked for reading, or locked for modification. When an attempt to lock a file cannot be satisfied, the calling task will wait either indefinitely or for a specific period for another task to unlock the file, or until an attention interrupt is received. If the file cannot be locked, an error indicating this is returned. The file locking software detects deadlocks between tasks using Warshall's algorithm and returns an error indication without locking the file and without waiting. Locking a file is in effect locking the name of that file. For example, the following sequence of commands can be executed while leaving FILE1 locked even though a file with the name FILE1 does not always exist: $lock FILE1 RENAME $rename FILE1 as FILE2 $create FILE1 At a later date this capability to lock names allowed the "file" locking routines to be used to implement record level locking between tasks accessing the centrally managed file *MESSAGES that was used by the MTS $Messagesystem to hold mailboxes and messages for individual users. The addition of file locking allowed removal of the restriction that a single userID could only be signed on once. Instead, the number of simultaneous sign ons was controlled by a maximum that could be set in the user's accounting record by the project manager or a site's business office. File save and restore Files are regularly backed up to tape unless they have been marked as NOSAVE. The file save process includes full and partial backups. Full saves are typically done once a week with no users signed on to the system. Partial saves save just the files that have changed since the last full or partial save and are typically done once each day in the late evening or early morning during normal operation with users signed on to the system. At the University of Michigan two copies of the full save tapes were made and one copy was stored "off-site". Save tapes were kept for six weeks and then reused. The tapes from every sixth full save were kept "forever". Files are saved to allow recovery from "disk disasters" in which the file system becomes damaged or corrupt, usually due to a hardware failure. But users could restore individual files as well using the program *RESTORE. Terminal support At its peak, MTS at the University of Michigan simultaneously supported more than 600 terminal sessions as well as several batch jobs. Terminals are attached to MTS over dial-in modems, leased or dedicated data circuits, and network connections. The Michigan Communications Protocol (MCP), a simple framing protocol for use with asynchronous connections that provides error detection and retransmission, was developed to improve the reliability of terminal to MTS and computer to MTS connections. A very wide range of terminals are supported including the 10 character per second (cps) Teletype Model 33, the 30 cps LA-36 and 120 cps LA-120 DECWriter, the 14 cps IBM 2741, and at ever increasing speeds up to 56,000 bits per second, the VT100 display, the Visual 550 display, the Ontel OP-1 and OP-1/R displays, Tektronix 4000 series of graphic displays, and personal computers from Apple (AMIE for the Apple ][), IBM (PCTie for DOS), and others running terminal emulation programs, including some specifically developed for use with MTS. Most terminals that are compatible with any of these models are also supported. MTS also supports access from 10- or 12-button touch-tone telephones via the IBM 7772 Audio Response Unit and later the Votrax Audio Response Unit,<ref>"The University of Michigan Audio Response System and Speech Synthesis Facility", Edward J. Fronczak, Second USA Japan Computer Conference, Proceedings, pp. 380-84, 1975</ref> IBM 1052 consoles, IBM 3066 console displays, and IBM 3270 family of locally attached displays (IBM 3272 and 3274 control units, but not remote 3270 displays). Front-end communication processors MTS can and does use communication controllers such as the IBM 2703 and the Memorex 1270 to support dial-in terminals and remote batch stations over dial-in and dedicated data circuits, but these controllers proved to be fairly inflexible and unsatisfactory for connecting large numbers of diverse terminals and later personal computers running terminal emulation software at ever higher data rates. Most MTS sites choose to build their own front-end processors or to use a front-end processor developed by one of the other MTS sites to provide terminal support. These front-end processors, usually DEC PDP-8, PDP-11, or LSI-11 based with locally developed custom hardware and software, would act as IBM control units attached to the IBM input/output channels on one side and to modems and phone lines on the other. At the University of Michigan the front-end processor was known as the Data Concentrator (DC). The DC was developed as part of the CONCOMP project by Dave Mills and others and was the first non-IBM device developed for attachment to an IBM I/O Channel. Initially a PDP-8 based system, the DC was upgraded to use PDP-11 hardware and a Remote Data Concentrator (RDC) was developed that used LSI-11 hardware that connected back to a DC over a synchronous data circuit. The University of British Columbia (UBC) developed two PDP-11 based systems: the Host Interface Machine (HIM) and the Network Interface Machine (NIM). The University of Alberta used a PDP-11 based Front-end processor. These front-end systems support their own command language of "device commands", usually lines prefixed with a special character such as a percent-sign (%), to allow the user to configure and control the connections. The $CONTROL command and programs running on MTS can use the CONTROL subroutine to issue device commands to front-end and network control units. Network support Over time some front-ends evolved to provide true network support rather than just providing support for connections to MTS. At the University of Michigan (UM) and Wayne State University (WSU) there was a parallel development effort by the Merit Network to develop network support. The Merit nodes were PDP-11 based and used custom hardware and software to provide host to host interactive connections between MTS systems and between MTS and the CDC SCOPE/HUSTLER system at Michigan State University (MSU). The Merit nodes were known as Communication Computers (CCs) and acted as IBM Control Units on the one side while providing links to other CCs on the other side. The initial host to host interactive connections were supplemented a bit later by terminal to host (TL) connections, and later still by host to host batch connections which allowed remote jobs submitted from one system to be executed (EX) on another with printed (PR) and punched card output (PU) returned to the submitting system or to another host on the network. The remote batch jobs could be submitted from a real card reader or via *BATCH* using a #NET "card" at the front of the job. Merit renamed its Communication Computers to be Primary Communication Processors (PCPs) and created LSI-11 based Secondary Communication Processors (SCPs). PCPs formed the core of the network and were attached to each other over Ethernet and dedicated synchronous data circuits. SCPs were attached to PCPs over synchronous data circuits. PCPs and SCPs would eventually include Ethernet interfaces and support local area network (LAN) attachments. PCPs would also serve as gateways to commercial networks such as GTE's Telenet (later SprintNet), Tymnet, and ADP's Autonet, providing national and international network access to MTS. Later still the PCPs provided gateway services to the TCP/IP networks that became today's Internet. The Merit PCPs and SCPs eventually replaced the Data Concentrators and Remote Data Concentrators at the University of Michigan. At their peak there were more than 300 Merit PCPs and SCPs installed, supporting more than 10,000 terminal ports. Virtual environments UMMPS provides facilities that allow the creation of virtual environments, either virtual machines or virtual operating systems. Both are implemented as user programs that run under MTS. The initial work on the first MTS virtual machine was done at the University of Michigan to simulate the IBM S/360-67 and allow debugging of UMMPS and MTS. Later the University of British Columbia did the initial work to create a S/370 MTS virtual machine. In theory these virtual machines could be used to run any S/360 or S/370 system, but in practice the virtual machines were only used to debug MTS and so there may be subtle features that are not used by MTS that are not completely or correctly implemented. The MTS virtual machine was never updated to support the S/370-XA architecture (instead other tools such as SWAT and PEEK were used to debug MTS and IBM's VM/XA or VM/ESA were used to debug UMMPS). In the early 1970s work was done at Wayne State University to run a version of OS/MVT in a modified virtual machine (VOS) under MTS as a production service. "Student" virtual machines in MTS have also been created as teaching tools. Here the OS running in the virtual machine (written by the student) uses simulated devices and has no connection to the "real" outside world at all (except possibly a console). In addition to virtual machines, MTS provides two programs that implement virtual operating system environments. *FAKEOS, developed at the University of Michigan, allows programs from OS/360 to run as user programs in MTS. *VSS, developed at the University of British Columbia, allows programs from OS/VS1 and MVS/370 to run as user programs in MTS. Neither program actually runs the IBM operating system, instead they simulate enough of the operating environment to allow individual programs developed for those operating systems to run. Both programs can be run directly, but often they are run from driver files that give an end user the impression that they are running a regular MTS user program. Electronic mail At least three different implementations of e-mail were available under MTS at different times: *MAIL from NUMAC, but not available at all MTS sites; CONFER, the computer conferencing system written by Robert Parnes at UM; and $MESSAGESYSTEM from the University of Michigan Computing Center.MTS Volume 23: Messaging and Conferencing in MTS, University of Michigan Computing Center, Ann Arbor, Michigan CONFER and *MAIL only sent and received mail to and from "local" users. Available to users in July 1981, $MESSAGESYSTEM is the last of the three systems to be implemented and became the most widely used. Between 1981 and 1993 it was used to send and receive more than 18 million messages at the University of Michigan. It can send: local and network e-mail messages, dispatches (immediate messages displayed at another user's terminal unless dispatches were blocked by the other user), bulletins (messages sent by the system operator to particular users delivered automatically at the beginning of an MTS session), and signon messages (messages sent by the system operator to all users delivered automatically before the start of an MTS session). Some notable features of $MESSAGESYSTEM include the ability: to send to individuals by signon ID or name, to groups of individuals by signon ID, project ID, or group name, or to the system operator; to send to a list stored in a file; to use the program *USERDIRECTORY to create and maintain a database of e-mail names for individuals and for groups including names and groups that include remote or network users; to recall/delete messages that hadn't already been read; to add or remove recipients to messages after they had been sent; to display a history of messages in an e-mail chain without the need to include the text from older messages in each new message; to set expiration and hold until dates and times for e-mail messages; to display the status of incoming and outgoing messages; to retrieve incoming and outgoing messages using a database model (incoming, outgoing, new, old/seen, to recipients, from recipients, message number, date sent, expiration date, ...); to permit a mailbox allowing uses by signon IDs other than the mailbox owner's; to automatically forward messages from one mailbox to another; to archive older messages, and send and receive messages using a subroutine interface in addition to commands. An application for the Apple Macintosh, InfoX (aka MacHost), was developed to provide a modern interface to the MTS Message System and *USERDIRECTORY. In 1984 MTS could be used to send and receive remote e-mail to and from over 300 sites around the world. The first ability to send and receive e-mail messages to and from users on remote systems (remote messages or network mail) was implemented in 1982 as part of the MAILNET project, a joint effort of 16 universities and EDUCOM (later EDUCAUSE) supported with funding from the Carnegie Corporation. MIT served as a relay hub between the MAILNET sites and as a gateway to CSNET, ARPANET, and BITNET. MTS at the University of Michigan used its connections to the Merit Network and through Merit to GTE's commercial X.25 network, Telenet (later SprintNet), to communicate with MIT. MTS at the University of Michigan served as a relay site for other sites on the UM campus and for other MTS sites that did not have direct access to the MAILNET relay at MIT. The remote e-mail addresses for an MTS user at the University of Michigan were: name@UMich-MTS.Mailnet (from MAILNET and BITNET sites) name%UMich-MTS.Mailnet@MIT-MULTICS.ARPA (from CSNET and ARPANET sites) name@UM (from other UM or MTS sites) To send e-mail to a remote site, MTS users at the University of Michigan used addresses of the form: name@CARNEGIE (to Carnegie-Mellon University a MAILNET site) name@CARNEGIE.MAILNET (the more official, but longer name for CMU) name@WSU (to Wayne State University an MTS site) name@Wayne-MTS.Mailnet (the more official but longer name for WSU) name%brown@CSNET-RELAY.ARPA (to Brown University a CSNET Phonenet site) (to Cornell University a CSNET or ARPANET site) name@STANFORD.BITNET (to Stanford University a BITNET site) Over time as more and more computers had direct connections to the Internet the MAILNET relay approach was replaced with the more direct and more reliable peer to peer e-mail delivery and Internet domain style of e-mail addresses in use today (name''@um.cc.umich.edu). InfoX InfoX (pronounced "info-ex", originally InfoDisk) is a program for the Apple Macintosh developed by the Information Technology Division at the University of Michigan. It provides a modern user interface (menus, icons, windows, and buttons) that can be used to check MTS electronic mail, participate in CONFER II conferences, access the MTS User Directory, and create, edit, and manipulate files. InfoX adds Macintosh-style word processing features to the more traditional editing functions available from the MTS, $Message, $Edit, and CONFER command-line interfaces. One can use the standard Cut, Copy, and Paste commands under the Macintosh Edit menu to move text from any Macintosh file. Accounting and charging Each signon ID is allocated resource limits (money, disk space, connect time, ...) which control the amount and types of work that can be done by the ID. IDs can be limited to using just terminal sessions or just batch jobs or restricted to working during times of the day or days of the week when the rates charged are lower. Each signon ID is assigned an expiration date. Resources that can be charged for include: CPU time—charged in seconds of CPU time Memory usage—charged as CPU-VM integral ... e.g. 40 pages of virtual memory used for 10 seconds is charged as 400 page-seconds Printer usage—charged as pages of paper and lines of output (for line printers) or pages and sheets (for page printers) Disk space used—charged in page-months (one page=4096 bytes) Terminal or network connect time-charged in minutes Cards read and punched-charged by the card Paper tape punched-charged by the foot Tapes mounted and tape drive usage time-charged by number of tapes mounted and minutes of usage Program product surcharges (charged on a program by program basis for certain licensed program products) Other resources (e.g. plotters, photo-typesetters, etc.) Note that while there is a charge for virtual memory used, there is no charge for real memory used. Note too that there is no change for page-in operations, although they are included in the session summary information that is reported at sign off. Different rates can be changed for different classes of projects (internal, external, commercial, ...) and for different times of the day or days of the week. Depending on the policies and practices at different sites, charges can be for "real money" or "soft money" (soft money is sometimes called "funny money", although just how funny it is usually depends on who is or isn't paying the bills). Users can display the cost of a session using the $DISPLAY COST command, can display their account balances using the $ACCOUNTING command, and the costs of a session and the account's remaining balance are displayed when the job or session ends. There is also an option ($SET COST=ON) that will cause the incremental and cumulative session cost to be displayed after each MTS command is executed. To prevent a user from overdrawing their account, the money limit is checked when the user attempts to sign on. If the account balance is zero or negative, the sign on is not allowed. For batch jobs, if the account balance is not sufficient to cover the charges estimated for the job, the job is not run. For terminal sessions, when an account's balance falls below one dollar, a warning "You have run out of money" followed by the current balance is printed. This "out of money" message is repeated at regular intervals until the user signs off. Signon IDs can run a negative balance, but usually not a large one or by accident. Depending on the administrative policies at a particular site, projects often have to pay for resources used even if they are beyond the amount authorized. To provide additional protection against accidents that might quickly use more resources than desired, users may also set global and local limits on CPU time usage. Global time limits ($SIGNON ccid T=maxtime) apply to an entire job or session. Local time limits apply to running individual programs ($RUN program T=maxtime). Global and local limits on the number of pages to be printed and the number of cards to be punched can also be set ($SIGNON ccid P=maxpages C=maxcards and $RUN program P=maxpages C=maxcards). A default local CPU time limit can be established using the $SET TIME=maxtime command. References 1960s software Discontinued operating systems IBM mainframe operating systems Operating systems by architecture Time-sharing operating systems

Operating System (OS)

NeXTSTEP NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprietary workstation computers such as the NeXTcube. It was later ported to several other computer architectures. Although relatively unsuccessful at the time, it attracted interest from computer scientists and researchers. It was used as the original platform for the development of the Electronic AppWrapper, the first commercial electronic software distribution catalog to collectively manage encryption and provide digital rights for application software and digital media, a forerunner of the modern "app store" concept. It was also the platform on which Tim Berners-Lee created the first web browser, and on which id Software developed the video games Doom and Quake. In 1996, NeXT was acquired by Apple Computer. The NeXTSTEP platform and OpenStep later became components of the Unix-based architecture of Mac OS X (now macOS) — a successor to the classic Mac OS that leveraged a combination of Unix supplemented by NeXTSTEP components and Apple's own technologies. Unix derivatives incorporating NeXTSTEP would eventually power all of Apple's platforms, including iPhone. Overview NeXTSTEP (also stylized as NeXTstep, NeXTStep, and NEXTSTEP) is a combination of several parts: a Unix operating system based on the Mach kernel, plus source code from BSD Display PostScript and a proprietary windowing engine the Objective-C language and runtime an object-oriented (OO) application layer, including several "kits" development tools for the OO layers. NeXTSTEP is notable for having been a preeminent implementation of the latter three items. The toolkits offer considerable power, and are the canonical development system for all of the software on the machine. It introduced the idea of the Dock (carried through OpenStep and into today's macOS) and the Shelf. NeXTSTEP also originated or innovated a large number of other GUI concepts which became common in other operating systems: 3D "chiseled" widgets, large full-color icons, system-wide drag and drop of a wide range of objects beyond file icons, system-wide piped services, real-time scrolling and window dragging, properties dialog boxes called "inspectors", and window modification notices (such as the saved status of a file). The system is among the first general-purpose user interfaces to handle publishing color standards, transparency, sophisticated sound and music processing (through a Motorola 56000 DSP), advanced graphics primitives, internationalization, and modern typography, in a consistent manner across all applications. Additional kits were added to the product line to make the system more attractive. These include Portable Distributed Objects (PDO), which allow easy remote invocation, and Enterprise Objects Framework, a powerful object-relational database system. The kits made the system particularly interesting to custom application programmers, and NeXTSTEP had a long history in the financial programming community. History A preview release of NeXTSTEP (version 0.8) was shown with the launch of the NeXT Computer on October 12, 1988. The first full release, NeXTSTEP 1.0, shipped on September 18, 1989. The last version, 3.3, was released in early 1995, by which time it ran on not only the Motorola 68000 family processors used in NeXT computers, but also on Intel x86, Sun SPARC, and HP PA-RISC-based systems. NeXTSTEP was later modified to separate the underlying operating system from the higher-level object libraries. The result was the OpenStep API, which ran on multiple underlying operating systems, including NeXT's own OPENSTEP, Windows NT and Solaris. NeXTSTEP's legacy stands today in the form of its direct descendants, Apple's macOS, iOS, watchOS, and tvOS operating systems. Unix From day one, the operating system of NeXTSTEP was built upon Mach/BSD. It was initially built on 4.3BSD-Tahoe. It changed to 4.3BSD-Reno after the release of NeXTSTEP 3.0. It changed to 4.4BSD during the development of Rhapsody. Legacy The first web browser, WorldWideWeb, and the first-ever app store were all invented on the NeXTSTEP platform. Some features and keyboard shortcuts now commonly found in web browsers can be traced back to NeXTSTEP conventions. The basic layout options of HTML 1.0 and 2.0 are attributable to those features available in NeXT's Text class. Lighthouse Design Ltd. developed Diagram!, a drawing tool, originally called BLT (for Box-and-Line Tool) in which objects (boxes) are connected together using "smart links" (lines) to construct diagrams such a flow charts. This basic design could be enhanced by the simple addition of new links and new documents, located anywhere in the local area network, that foreshadowed Tim Berners-Lee's initial prototype that was written in NeXTStep (October–December 1990). In the 1990s, the pioneering PC games Doom (with its WAD level editor), Doom II, and Quake (with its respective level editor) were developed by id Software on NeXT machines. Other games based on the Doom engine such as Heretic and its sequel Hexen by Raven Software as well as Strife by Rogue Entertainment were also developed on NeXT hardware using id's tools. Altsys made a NeXTSTEP application called Virtuoso, version 2 of which was ported to Mac OS and Windows to become Macromedia FreeHand version 4. The modern "Notebook" interface for Mathematica, and the advanced spreadsheet Lotus Improv, were developed using NeXTSTEP. The software that controlled MCI's Friends and Family calling plan program was developed using NeXTSTEP. About the time of the release of NeXTSTEP 3.2, NeXT partnered with Sun Microsystems to develop OpenStep. It is the product of an effort to separate the underlying operating system from the higher-level object libraries to create a cross-platform object-oriented API standard derived from NeXTSTEP. The OpenStep API targets multiple underlying operating systems, including NeXT's own OPENSTEP. Implementations of that standard were released for Sun's Solaris, Windows NT, and NeXT's version of the Mach kernel. NeXT's implementation is called "OPENSTEP for Mach" and its first release (4.0) superseded NeXTSTEP 3.3 on NeXT, Sun, and Intel IA-32 systems. Following an announcement on December 20, 1996, Apple Computer acquired NeXT on February 4, 1997, for $429 million. Based upon the "OPENSTEP for Mach" operating system, and developing the OPENSTEP API to become Cocoa, Apple created the basis of Mac OS X, and eventually, in turn, of iOS/iPadOS, watchOS, and tvOS. A free software implementation of the OpenStep standard, GNUstep, also exists. Release history Versions up to 4.1 are general releases. OPENSTEP 4.2 pre-release 2 is a bug-fix release published by Apple and supported for five years after its September 1997 release. See also OpenStep, the object-oriented application programming interface derived from NeXTSTEP GNUstep, an open-source implementation of Cocoa API respectively OpenStep API Window Maker, a window manager designed to emulate the NeXT GUI for the X Window System Bundle (macOS) Miller Columns, the method of directory browsing that NeXTSTEP's File Viewer used Multi-architecture binary NeXT character set Previous, an emulator for NeXT hardware capable of running some versions of NeXTSTEP References http://www.cnet.com/news/ibm-buys-sequent-for-810-million A complete guide to the confusing series of names applied to the system External links NeXTComputers.org The Next Step BYTE Magazine 14-03, Object Oriented Programming with NextStep A modern NextStep inspired desktop environment. 1989 software Berkeley Software Distribution Discontinued operating systems Mach (kernel) NeXT Object-oriented operating systems Unix variants Window-based operating systems

Operating System (OS)

List of Linux-supported computer architectures The basic components of the Linux family of operating systems, which are based on the Linux kernel, the GNU C Library, BusyBox or forks thereof like μClinux and uClibc, have been programmed with a certain level of abstraction in mind. Also, there are distinct code paths in the assembly language or C source code which support certain hardware. Therefore, the source code can be successfully compiled onor cross-compiled fora great number of computer architectures. Furthermore, the required free and open-source software has also been developed to interface between Linux and the hardware Linux is to be executed on. For example, compilers are available, e.g. GNU Compiler Collection (GCC) and LLVM/Clang. For cross-compilation a number of complete toolchains are available, like GNU toolchain, OpenWrt Buildroot or OpenEmbedded. The Yocto Project is targeted at embedded use cases. The portability section of the Linux kernel article contains information and references to technical details. Note that further components like a display server, or programs like Blender, can be present or absent. Fundamentally any software has to be ported, i.e. specifically adapted, to any kind of hardware it is supposed to be executed on. The level of abstraction that has been kept in mind while programming that software in the first place dictates the necessary effort. The relevant term is of the porting target is computer architecture; it comprises the instruction set(s) and the microarchitecture(s) of the processor(s), at least of the CPU. The target also comprises the "system design" of the entire system, be it a supercomputer, a desktop computer or some SoC, e.g. in case some unique bus is being used. In former times, the memory controller was part of the chipset on the motherboard and not on the CPU-die. Although the support of a specific instruction set is the task of the compiler, the software must be written with a certain level of abstraction in mind to make this portability possible. Any code written in Assembly language will be specific to the instruction set. The support of a specific microarchitecture includes optimizations for the CPU cache hierarchy, the TLB, etc. Releases DEC Alpha (alpha) Analog Devices Blackfin (supported since 2.6.22 and dropped since 4.17) (blackfin) Andes Technology NDS32 (nds32) ARM family of instruction sets (32- and 64-bit) (arm and arm64): Acorn Archimedes and RiscPC series (original machines were supported in 2.6.22) Allwinner Apple M series processors Broadcom VideoCore DEC StrongARM Samsung Exynos Marvell (formerly Intel) XScale Sharp Zaurus HiSilicon iPAQ Palm, Inc.'s Tungsten Handheld Gamepark Holdings' GP2X Open Pandora MediaTek Nokia 770 Internet Tablet Nokia N800 Nokia N810 Nokia N900 Nomadik NovaThor (discontinued) gumstix Sony Mylo Qualcomm Snapdragon Nvidia Tegra TI OMAP Psion 5, 5MX, Series 7, netBook Rockchip Some Models of Apple iPods (see iPodLinux) OpenMoko Neo 1973, Neo FreeRunner Freescale's (formerly Motorola's) i.MX multimedia processors Atmel AVR32 (dropped since 4.12) (avr32) C-SKY Axis Communications' ETRAX CRIS (dropped since 4.17) Texas Instruments TMS320 family of DSPs from Texas Instruments TMS320C64x (c6x) Freescale's (formerly Motorola's) 68k architecture (68020, 68030, 68040, 68060) (m68k): Some Amigas: A1200, A2500, A3000, A4000 Apple Macintosh II, LC, Quadra, Centris and early Performa series Some Atari computers (TT and Falcon030) Fujitsu FR-V (dropped since 4.17) (frv) Qualcomm Hexagon (hexagon) Hewlett-Packard's PA-RISC (parisc) H8 architecture from Renesas Technology, formerly Hitachi (h8300) H8/300 H8/500 International Business Machines (IBM) System/390 (31-bit) (s390) (dropped since 4.1 in favor of s390x except for user space compat mode) z/Architecture (IBM Z and IBM LinuxONE) (64-bit) (s390x) Imagination META (dropped since 4.17) Intel IA-64 Itanium, Itanium II (ia64) x86 architecture (x86): IBM PC compatibles using IA-32 and x86-64 processors: Intel 80386 (dropped since 3.8), 80486, and their AMD, Cyrix, Texas Instruments and IBM variants The entire Pentium series and its Celeron and Xeon variants Intel Core processors AMD 5x86, K5, K6, Athlon (all 32-bit versions), Duron, Sempron x86-64: 64-bit processor architecture, now officially known as AMD64 (AMD) or Intel64 (Intel); supported by the Athlon 64, Opteron and Intel Core 2 processors, among others Cyrix 5x86, 6x86 (M1), 6x86MX and MediaGX (National/AMD Geode) series VIA Technologies Eden (Samuel II), VIA C3, and VIA C7 processors (all 32-bit) and VIA Nano (x86-64) Microsoft's Xbox (Pentium III processor), through the Xbox Linux project SGI Visual Workstation (Pentium II/III processor(s) with SGI chipset) Sun Microsystems Sun386i workstation (80386 and 80486) Support for 8086, 8088, 80186, 80188 and 80286 CPUs is under development (the ELKS fork) M32R from Mitsubishi (dropped since 4.17) (m32r) Microblaze from Xilinx (microblaze) MIPS architecture (mips): Dingoo Infineon's Amazon & Danube Network Processors Ingenic Jz4740 Loongson (MIPS-compatible), and models 2 and 2E, from BLX IC Design Ltd (China) Some PlayStation 2 models, through the PS2 Linux project PlayStation Portable uClinux 2.4.19 port Broadcom wireless chipsets Dreambox (HD models) Cavium Octeon packet processors MN103 from Panasonic Corporation (dropped since 4.17) (mn10300) OpenRISC (openrisc) OpenRISC 1000 family in the mainline Linux Kernel as of 3.1 Beyond Semiconductor OR1200 Beyond Semiconductor OR1210 Power ISA: IBM Servers PowerPC architecture (powerpc): IBM's Cell Most pre-Intel Apple computers (all PCI-based Power Macintoshes, limited support for the older NuBus Power Macs) Clones of the PCI Power Mac marketed by Power Computing, UMAX and Motorola Amigas upgraded with a "Power-UP" card (such as the Blizzard or CyberStorm) AmigaOne motherboard from Eyetech Group Ltd (UK) Samantha from Soft3 (Italy) IBM RS/6000, AS/400 and pSeries systems Pegasos I and II boards from Genesi Nintendo GameCube and Wii, through Nintendo GameCube Linux Project BlackDog from Realm Systems, Inc. Sony PlayStation 3 Microsoft's Xbox 360, through the free60 project V-Dragon CPU from Culturecom Virtex II Pro field-programmable gate array (FPGA) from Xilinx with PowerPC cores Dreambox (non-HD models) RISC-V SPARC (sparc) SPARC (32-bit): Sun-4 (dropped since 2.6.27) SPARCstation/SPARCserver series (sun4m, sun4d) sun4c (dropped since version 3.5) LEON UltraSPARC (64-bit): Sun Ultra series Sun Blade Sun Fire SPARC Enterprise systems, also the based on the UltraSPARC T1, UltraSPARC T2, UltraSPARC T3, and UltraSPARC T4 processors SuperH (sh) Sega Dreamcast (SuperH SH4) HP Jornada 680 through Jlime distribution (SuperH SH3) Synopsys DesignWare ARC cores, originally developed by ARC International (arc) S+core (dropped since 4.17) (score) Tilera (dropped since 4.17) Xtensa from Tensilica UniCore32 (unicore32) Additional processors (particularly Freescale's 68000 and ColdFire) are supported by the MMU-less μClinux variant. See also Comparison of operating system kernels Comparison of operating systems Embeddable Linux Kernel Subset User-mode Linux References External links BlueCat Linux Kernel Porting Guide Portability and supported architectures

Operating System (OS)

Genode Genode is a free and open-source software operating system (OS) framework consisting of a microkernel abstraction layer and a set of user space components. The framework is notable as one of the few open-source operating systems not derived from a proprietary OS, such as Unix. The characteristic design philosophy is that a small trusted computing base is of primary concern in a security-oriented OS. Genode can be used as a basis for a desktop computer or tablet OS or as a virtual machine monitor for guest operating systems. The framework has been used as a trusted component of secure virtualization systems for both x86 and ARM. The small codebase of Genode makes it a flexible alternative to more complex Unix-derived operating systems. For this reason the framework has been used as a base system for research in such fields as virtualization, inter-process communication, IP stack isolation, monitoring, and software development. History Genode was first conceived as the Bastei OS Architecture research report at the Technical University of Dresden (TU Dresden). The focus of the report was to determine the practicality of a component-based OS using capability-based security. This report was motivated in part by research into L4 microhypervisors conducted during the same time. Following the success of an early prototype, the authors of the report founded the company Genode Labs to develop Bastei as the Genode OS Framework. Releases The project is developed publicly as an open source project released under the terms of the GNU Affero General Public License with a commercial entity offering alternative licensing. Releases are scheduled at three-month intervals to make changes to the system application binary interface (ABI), application programming interface (API), and issue documentation. The OS framework is available in source code form and following the 18.02 release a general purpose derivative named Sculpt is provided with on-target binary deployment. Architectural features Genode builds on the general philosophy of microkernels: the smaller and simpler the code, the easier it is to verify for trustworthiness and correctness. Genode extends this philosophy to user space by composing complex applications from small components. Each component exists in a strict hierarchy of parent-child relationships. Any component acting as a parent may apply resource and inter-process communication (IPC) access policies to its children. This hierarchical system layout yields intuitive partitioning and privilege deescalation as specialized subsystems are nested within more general subsystems, mitigating the confused deputy problem endemic to centralized or superuser system policy. The framework is designed to be hosted by microkernels, however the features of any given microkernel fall mostly within a common set, and monolithic kernels implement a superset of those features. Abstracting these features allows Genode to act as user space for variety of L4 microkernels, and Linux. Criticism C++ Genode is often criticized for the choice of its implementation language, C++ (a few other operating systems implemented in C++ include BeOS, Fuchsia, Ghost, Haiku, IncludeOS, OSv, Palm OS, ReactOS, Syllable, and all major browser engines). This critique usually asserts that C++ is a poor choice for implementing system libraries and APIs because of the inherent complexity of C++ and the difficulty in analyzing code for correct behavior. While Genode does make use of multiple inheritance and templates in its system library, the use of the C++ Standard Library is not allowed and language features that rely on implicit global state, such as thread-local storage and the global allocator, have been removed from the language runtime. Comprehensive static analysis of C++ is not possible. However, the Genode project publishes unit tests for empirical analysis. XML Genode components consume and publish state using structured data serialized in XML, in contrast to the plain text model of Unix derivatives. The Genode framework makes use of XML in effectively all of its components because XML is easily parsed and generated programmatically while still being possible to understand and edit manually. Local namespacing Genode lacks any practical global namespace; there is no global file system or registry of processes or IPC endpoints. This is in contrast to systems such as Unix which feature a ubiquitous file system and allow a superuser context to arbitrarily manage any process within the system. Explicitly declaring the permissions and routing of components may be perceived as labor-intensive relative to Unix. However, compartmentalizing administration allows subsystems to be managed by mutually untrusted system administrators on the same machine without resorting to virtualizing, a common isolation method. Sculpt The Genode project publishes a desktop operating system named Sculpt that targets contemporary consumer laptops. Sculpt is a small base system with automatic device detection and configuration, some GUI control interfaces, and frontends to the Genode package manager. The system does not feature a full desktop environment, but requires users to deploy virtual machines hosting traditional OSes for a fully featured desktop. Sculpt is distinguished from the Genode operating system framework in that it relies heavily on dynamic reconfiguration using privileged control components in contrast to specialized systems with static policies. See also HelenOS, a desktop microkernel based operating system QNX, a proprietary Unix-like operating system hosted by a microkernel Qubes OS, a desktop operating system that provides security through virtualization Subgraph (operating system), a Linux distribution that provides security through sandboxing Capability-based security Secure by default References External links Official websites Research projects KV-Cache: A Scalable High-Performance Web-Object Cache for Manycore TrApps: Secure Compartments in the Evil Cloud Development of an Embedded Platform for Secure CPS Services Secure-OS project of IIT Madras Kernel isolation of a Capability-based security Operating System Mobile Device Security with ARM TrustZone ARM operating systems Capability systems Free software operating systems Free software programmed in C++ Microkernel-based operating systems Operating system security X86 operating systems X86-64 operating systems

Operating System (OS)

Amdahl UTS UTS is a discontinued implementation of the UNIX operating system for IBM mainframe (and compatible) computers. Amdahl created the first versions of UTS, and released it in May 1981, with UTS Global acquiring rights to the product in 2002. UTS Global has since gone out of business. System requirements UTS Release 4.5 supports the following S/390 model processors and their successors: Amdahl 5990, 5995A, 5995M series of ECL processors Amdahl Millennium Global Server series of CMOS processors Fujitsu Global Server IBM ES/9000/9021 series of ECL processors IBM G4, G5 & G6 Servers (the 9672 R and X series of CMOS processors) History The UTS project had its origins in work started at Princeton University in 1975 to port UNIX to the IBM VM/370 system. Team members there were Tom Lyon, Joseph Skudlarek, Peter Eichenberger, and Eric Schmidt. Tom Lyon joined Amdahl in 1978, and by 1979 there was a full Version 6 Unix system on the Amdahl 470 being used internally for design automation engineering. In late 1979 this was updated to the more commonly ported Version 7. In 1980 Amdahl announced support for Unix on the System 470. Five years later, IBM announced its own mainframe Unix, IX/370, as a competitive response to Amdahl. The commercial versions of UTS were based on UNIX System III and UNIX System V. In 1986, Amdahl announced the first version to run natively on IBM/370-compatible hardware, UTS/580 for its Amdahl 580 series of machines; previous Unix ports always ran as "guests" under the IBM VM hypervisor. Version 4.5 was based on Unix System V, Release 4 (SVR4). See also Linux on IBM Z OpenSolaris for System z UNIX System Services in OS/390 and its successors References External links UTS Global home page (archived page at Archive.org, April 2008) Unix variants 1981 software

Operating System (OS)

Microware Microware was a US corporation based in Clive, Iowa that produced the OS-9 real-time operating system. Microware Systems Corporation existed as a separate entity from 1977 until September 2001, when it was bought by RadiSys Corp., and became a division of that company. The rights to Microware OS-9 and related software were purchased by a group of distributors on 1 March 2013. The new owner was Microware LP. Microware initially produced a version of BASIC and a real-time kernel for the Motorola 6800 processor, and was asked by Motorola to develop what turned into BASIC09 for the then-new Motorola 6809 processor. Having written BASIC09, they decided it needed an operating system underlying it, and they created the first version of OS-9. OS-9 was ported to the 68000 family of processors and, after being rewritten mostly in C, to the Intel 80x86, PowerPC, ARM, MIPS, and some of the Hitachi SuperH (SH) series processors. Initially, in the days of the SS-50 bus and SS-50C bus systems such as SWTPC, Gimix, and Smoke Signal Broadcasting, OS-9 was used more as a general purpose microcomputer operating system and had a large, active hobbyist-user population. OS-9 was also popular with industrial and embedded-system users. This was especially true when OS-9 was available for popular 6809-based computers such as the FM-7, FM-77, and the Tandy TRS-80 Color Computer and its near-clone, the Dragon. Over time, Microware concentrated on industrial customers and neglected the hobbyist base that was porting a great many Unix packages and utilities to OS-9. Microware products RT68 – the original product for the 6800 OS-9 and OS-9000 – real-time operating systems for a wide range of embedded CPU architectures. CD-RTOS – the operating system used in the Philips CD-i players, which was a special version of OS-9/68K v2.4. DAVID – the Digital Audio Video Interactive Decoder platform for digital TV. Ariel – a micro OS based on an OS Microware acquired (MTOS-UX by IPI). Color Computer 3 BASIC ROM extensions to support 80-column text and new graphics modes not in the CoCo 1 and 2's Extended Color BASIC ROM External links Official site Real-time operating systems Embedded operating systems TRS-80 Color Computer Unix variants ARM operating systems X86 operating systems

Operating System (OS)

Computer Othello Computer Othello refers to computer architecture encompassing computer hardware and computer software capable of playing the game of Othello. Availability There are many Othello programs such as NTest, Saio, Edax, Cassio, Pointy Stone, Herakles, WZebra, and Logistello that can be downloaded from the Internet for free. These programs, when run on any up-to-date computer, can play games in which the best human players are easily defeated. This is because although the consequences of moves are predictable for both computers and humans, computers are better at envisaging them. Search techniques Computer Othello programs search for any possible legal moves using a game tree. In theory, they examine all positions / nodes, where each move by one player is called a "ply". This search continues until a certain maximum search depth or the program determines that a final "leaf" position has been reached. A naive implementation of this approach, known as Minimax or Negamax, can only search to a small depth in a practical amount of time, so various methods have been devised to greatly increase the speed of the search for good moves. These are based on Alpha-beta pruning, Negascout, MTD(f), NegaC*. The alphabeta algorithm is a method for speeding up the Minimax searching routine by pruning off cases that will not be used anyway. This method takes advantage of the fact that every other level in the tree will maximize and every other level will minimize. Several heuristics are also used to reduce the size of the searched tree: good move ordering, transposition table and selective Search. To speed up the search on machines with multiple processors or cores, a "parallel search" may be implemented. Several experiments have been made with the game Othello, like ABDADA or APHID On recent programs, the YBWC seems the preferred approach. Multi-Prob cut Multi-ProbCut is a heuristic used in alpha–beta pruning of the search tree. The ProbCut heuristic estimates evaluation scores at deeper levels of the search tree using a linear regression between deeper and shallower scores. Multi-ProbCut extends this approach to multiple levels of the search tree. The linear regression itself is learned through previous tree searches, making the heuristic a kind of dynamic search control. It is particularly useful in games such as Othello where there is a strong correlation between evaluations scores at deeper and shallower levels. Evaluation techniques There are three different paradigms for creating evaluation functions. Disk-square tables Different squares have different values - corners are good and the squares next to corners are bad. Disregarding symmetries, there are 10 different positions on a board, and each of these is given a value for each of the three possibilities: black disk, white disk and empty. A more sophisticated approach is to have different values for each position during the different stages of the game; e.g. corners are more important in the opening and early midgame than in the endgame. Mobility-based Most human players strive to maximize mobility (number of moves available) and minimize frontier disks (disks adjacent to empty squares). Player mobility and opponent mobility are calculated, and player potential mobility and opponent potential mobility are calculated as well. These measures can be found very quickly, and they significantly increase playing strength. Most programs have knowledge of edge and corner configurations and try to minimize the number of disks during the early midgame, another strategy used by human players. Pattern-based / pattern coefficients Mobility maximization and frontier minimization can be broken down into local configurations which can be added together; the usual implementation is to evaluate each row, column, diagonal and corner configuration separately and add together the values, many different patterns have to be evaluated. The process of determining values for all configurations is done by taking a large database of games played between strong players and calculating statistics for each configuration in each game stage from all the games. The most common choice to predict the final disc difference uses a weighted disk difference measure where the winning side gets a bonus corresponding to the number of disks. Opening book Opening books aid computer programs by giving common openings that are considered good ways to counter poor openings. All strong programs use opening books and update their books automatically after each game. To go through all positions from all games in the game database and determine the best move not played in any database game, transposition tables are used to record positions that have been previously searched. This means those positions do not need to be searched again. This is time-consuming as a deep search must be performed for each position, but once this is done, updating the book is easy. After each game played, all new positions are searched for the best deviation. Other optimizations Faster hardware and additional processors can improve Othello-playing program abilities, such as deeper ply searching. Solving Othello During gameplay, players alternate moves. The human player uses black counters while the computer uses white. The human player starts the game. Othello is strongly solved on 4×4 and 6×6 boards, with the second player (white) winning in perfect play. It remains unsolved on a standard 8×8 board, but computer analysis gives thousands of draw lines, or paths to a draw, although no such line has been fully proven. Othello 4 × 4 Othello 4x4 has a very small game tree and has been solved in less than one second by many simple Othello programs that use the Minimax method, which generates all possible positions (nearly 10 million). The result is that white wins with a +8 margin (3-11). Othello 6 × 6 Othello 6x6 has been solved in less than 100 hours by many simple Othello programs that use the Minimax method, which generates all possible positions (nearly 3.6 trillion). The result is that white wins with a +4 margin (16-20). Othello 8 × 8 The Othello 8x8 game tree size is estimated at 1054 nodes, and the number of legal positions is estimated at less than 1028. The game remains unsolved. A solution could possibly be found using intensive computation with top programs on fast parallel hardware or through distributed computation. Some top programs have expanded their books for many years now. As a result, many lines are in practice draws or wins for either side. Regarding the three main openings of diagonal, perpendicular and parallel, it appears that both diagonal and perpendicular openings lead to drawing lines, while the parallel opening is a win for black. The drawing tree also seems bigger after the diagonal opening than after the perpendicular opening. The parallel opening has strong advantages for the black player, enabling him to always win in a perfect play. Milestones in computer Othello 1977: Scientific American made the earliest known published reference to an Othello/Reversi program, written by N. J. D. Jacobs in BCPL. BYTE published "Othello, a New Ancient Game" as a BASIC type-in program in October. 1977: Creative Computing published a version of Othello written by Ed Wright in FORTRAN. 1978: Nintendo releases the video game Computer Othello in arcades. 1980: The Othello program The Moor (written by Mike Reeve and David Levy) won one game in a six-game match against world champion Hiroshi Inoue. Peter W Frey of Northwestern University discussed computer and human Othello strategies in BYTE, and discussed his TRS-80 Othello game which, Frey claimed, easily defeated Wright's version running on a CDC 6600. Paul Rosenbloom of Carnegie Mellon University developed IAGO, which finished in third place at a Northwestern University computer tournament. When IAGO played The Moor, IAGO was better at capturing pieces permanently and limiting its opponent's mobility. 1981: IAGO running on a DEC KA10 finished ahead of 19 other contestants at the Santa Cruz Open Othello Tournament at the University of California, Santa Cruz, with the only undefeated record. Charles Heath's TRS 80-based game finished in second place. Microcomputer CPU-based engines won the second through seventh places, ahead of several mainframes and minicomputers; Frey speculated that this was because computer Othello does not benefit from several of the advantages of larger computers, such as faster floating-point arithmetic. Late 1980s: Kai-Fu Lee and Sanjoy Mahajan created the Othello program BILL, which was similar to IAGO but incorporated Bayesian learning. BILL reliably beat IAGO. 1992: Michael Buro began work on the Othello program Logistello. Logistello's search techniques, evaluation function, and knowledge base of patterns were better than those in earlier programs. Logistello perfected its game by playing over 100,000 games against itself. 1997: Logistello won every game in a six-game match against world champion Takeshi Murakami. Though there had not been much doubt that Othello programs were stronger than humans, it had been 17 years since the last match between a computer and a reigning world champion. After the 1997 match, there was no longer any doubt: Logistello was significantly better than any human player. 1998: Michael Buro retired Logistello. Research interest in Othello waned somewhat, but some programs, including Ntest, Saio, Edax, Cassio, Zebra and Herakles, continued to be developed. 2004: Ntest became the strongest program, significantly stronger than Logistello. 2005: Ntest, Saio, Edax, Cyrano and Zebra, became significantly stronger than Logistello. Ntest and Zebra retired. 2011: Saio, Edax and Cyrano, became much faster than Logistello and other programs. List of top Othello/ Reversi programs NTest (Ntest) by Chris Welty Edax (Edax) by Richard Delorme Logistello by Michael Buro See also Computer Go Computer shogi Computer chess Computer Olympiad Reversi Notes External links 4 × 4 Othello 6 × 6 Othello List of Othello programs Chess programming Reversi software Abstract strategy games PSPACE-complete problems

Operating System (OS)

BSD (disambiguation) BSD is the Berkeley Software Distribution, a free Unix-like operating system, and numerous variants. BSD may also refer to: Science and technology Bipolar spectrum disorder Birch and Swinnerton-Dyer conjecture, an important unsolved problem in mathematics Computing BSD licenses, a family of permissive free software licenses originally from the Berkeley Software Distribution Bit stream decoder, a video decoder in a graphics processing unit Organizations Birsa Seva Dal, a political group in India Bob- und Schlittenverband für Deutschland, the bobsleigh, luge, and skeleton federation for Germany Blue State Digital, a new media strategy and technology firm Cray Business Systems Division, or Cray BSD Schools Beaverton School District, a school district in Beaverton, Oregon, US Bellevue School District, the school district of Bellevue, Washington, US Benoit School District, the school district of Benoit, Mississippi, US Brandywine School District, a school district in New Castle County, Delaware, US Burlingame School District, a school district in Burlingame, California, US Places Bumi Serpong Damai, a planned city in Greater Jakarta, Indonesia Baoshan Yunduan Airport (IATA code), China Other uses BSD Records, a 1950s record label Black Spiral Dancer, a Tribe of evil-aligned werewolves in the White Wolf produced role-playing game Werewolf: The Apocalypse Besiyata Dishmaya, BS"D, an Aramaic phrase meaning "with the help of Heaven" Bahamian dollar (ISO 4217 code) Bungo Stray Dogs, a Japanese manga and anime series. See also Berkeley Software Design (BSDi), a former corporation which developed, sold and supported BSD/OS BSD/OS, originally called BSD/386 and sometimes known as BSDi, a proprietary version of the BSD operating system developed by Berkeley Software Design List of BSD operating systems Blue Screen of Death (BSoD), an error screen displayed after a fatal system error Bipolar Spectrum Diagnostic Scale (BSDS)

Operating System (OS)

Operational availability Operational availability in systems engineering is a measurement of how long a system has been available to use when compared with how long it should have been available to be used. Definition Operational availability is a management concept that evaluates the following. Diagnostic down time Criticality Fault isolation down time Logistics delay down time Corrective maintenance down time Any failed item that is not corrected will induce operational failure. is used to evaluate that risk. Operational failure is unacceptable in any situation where the following can occur. Capital equipment loss Injury or loss of life Sustained failure to accomplish mission In military acquisition, operational availability is used as one of the Key Performance Parameters in requirements documents, to form the basis for decision support analyses. History Aircraft systems, ship systems, missile systems, and space systems have a large number of failure modes that must be addressed with limited resources. Formal reliability modeling during development is required to prioritize resource allocation before operation begins. Estimated failure rates and logistics delay are used to identify the number of forward positioned spare parts required to avoid excessive down time. This is also used to justify the expense associated with redundancy. Formal availability measurement is used during operation to prioritize management decisions involving upgrade resource allocation, manpower allocation, and spare parts planning. Principle Operational availability is used to evaluate the following performance characteristic. For a system that is expected to be available constantly, the below operational availability figures translate to the system being unavailable for approximately the following lengths of time (when all outages during a year are added together): The following data is collected for maintenance actions while in operation to prioritize corrective funding. Diagnostic down time is required to identify the amount of time spent perform maintenance when fault reporting does not support condition-based maintenance. Criticality identifies level of risk associated with loss of mission, injury or loss of life, and capitol equipment. Fault isolation down time is required to identify the amount of time spent locating a failure. Logistics delay down time is required to identify the amount of time required to obtain replacement parts or software. Corrective maintenance down time is required to identify the amount of time required to install and reconfigure replacement parts and software. This data is applied to the reliability block diagram to evaluate individual availability reduction contributions using the following formulas. Redundant items do not contribute to availability reduction unless all of the redundant components fail simultaneously. Operational availability is the overall availability considering each of these contributions. See also Active redundancy Availability Downtime Reliability block diagram References Maintenance Engineering concepts Reliability engineering Safety Fault tolerance Fault-tolerant computer systems

Operating System (OS)

Windows Server 2008 Windows Server 2008 is is the third release of the Windows Server operating system produced by Microsoft as part of the Windows NT family of the operating systems. It was released to manufacturing on February 4, 2008, and generally to retail on February 27, 2008. Derived from Windows Vista, Windows Server 2008 is the successor of Windows Server 2003, which is derived from the Windows XP codebase, released nearly five years earlier. On January 12, 2016, Microsoft ended support for all Internet Explorer versions older than Internet Explorer 11 released in 2013 for Windows 7. Extended support for Windows Server 2008 ended on January 14, 2020, after which the supported Windows versions were scattered across unsupported Windows versions. Extended Security Updates (ESU) updates last until January 10, 2023 (January 9, 2024 for Azure customers). Windows Server 2008 is the final version which supports IA-32-based processors (also known as 32-bit processors). Its successor, Windows Server 2008 R2, requires a 64-bit processor in any supported architecture (x86-64 for x86 and Itanium). History Originally known as Windows Server Codename "Longhorn", Microsoft chairman Bill Gates announced its official title (Windows Server 2008) during his keynote address at WinHEC 16 May 2007. Beta 1 was released on July 27, 2005; Beta 2 was announced and released on May 23, 2006, at WinHEC 2006 and Beta 3 was released publicly on April 25, 2007. Release Candidate 0 was released to the general public on September 24, 2007 and Release Candidate 1 was released to the general public on December 5, 2007. Windows Server 2008 was released to manufacturing on February 4, 2008, and officially launched on 27th of that month. Features Windows Server 2008 is built from the same codebase as Windows Vista and thus it shares much of the same architecture and functionality. Since the codebase is common, Windows Server 2008 inherits most of the technical, security, management and administrative features new to Windows Vista such as the rewritten networking stack (native IPv6, native wireless, speed and security improvements); improved image-based installation, deployment and recovery; improved diagnostics, monitoring, event logging and reporting tools; new security features such as BitLocker and address space layout randomization (ASLR); the improved Windows Firewall with secure default configuration; .NET Framework 3.0 technologies, specifically Windows Communication Foundation, Microsoft Message Queuing and Windows Workflow Foundation; and the core kernel, memory and file system improvements. Processors and memory devices are modeled as Plug and Play devices to allow hot-plugging of these devices. This allows the system resources to be partitioned dynamically using dynamic hardware partitioning - each partition has its own memory, processor and I/O host bridge devices independent of other partitions. Server Core Windows Server 2008 includes a variation of installation called Server Core. Server Core is a significantly scaled-back installation where no Windows Explorer shell is installed. It also lacks Internet Explorer, and many other non-essential features. All configuration and maintenance is done entirely through command-line interface windows, or by connecting to the machine remotely using Microsoft Management Console (MMC). Notepad and some Control Panel applets, such as Regional Settings, are available. A Server Core installation can be configured for several basic roles, including the domain controller (Active Directory Domain Services), Active Directory Lightweight Directory Services (formerly known as Active Directory Application Mode), DNS Server, DHCP server, file server, print server, Windows Media Server, Internet Information Services 7 web server and Hyper-V virtual server roles. Server Core can also be used to create a cluster with high availability using failover clustering or network load balancing. Andrew Mason, a program manager on the Windows Server team, noted that a primary motivation for producing a Server Core variant of Windows Server 2008 was to reduce the attack surface of the operating system, and that about 70% of the security vulnerabilities in Microsoft Windows from the prior five years would not have affected Server Core. Active Directory The Active Directory domain functionality that was retained from Windows Server 2003 was renamed to Active Directory Domain Services (ADDS). Active Directory Federation Services (ADFS) enables enterprises to share credentials with trusted partners and customers, allowing a consultant to use their company user name and password to log in on a client's network. Active Directory Lightweight Directory Services (AD LDS), (formerly Active Directory Application Mode, or ADAM) Active Directory Certificate Services (ADCS) allow administrators to manage user accounts and the digital certificates that allow them to access certain services and systems. Identity Integration Feature Pack is included as Active Directory Metadirectory Services. Active Directory Rights Management Services (ADRMS) Read-only domain controllers (RODCs), intended for use in branch office or other scenarios where a domain controller may reside in a low physical security environment. The RODC holds a non-writeable copy of Active Directory, and redirects all write attempts to a full domain controller. It replicates all accounts except sensitive ones. In RODC mode, credentials are not cached by default. Also, local administrators can be designated to log on to the machine to perform maintenance tasks without requiring administrative rights on the entire domain. Restartable Active Directory allows ADDS to be stopped and restarted from the Management Console or the command-line without rebooting the domain controller. This reduces downtime for offline operations and reduces overall DC servicing requirements with Server Core. ADDS is implemented as a Domain Controller Service in Windows Server 2008. All of the Group Policy improvements from Windows Vista are included. Group Policy Management Console (GPMC) is built-in. The Group Policy objects are indexed for search and can be commented on. Policy-based networking with Network Access Protection, improved branch management and enhanced end user collaboration. Policies can be created to ensure greater quality of service for certain applications or services that require prioritization of network bandwidth between client and server. Granular password settings within a single domain - ability to implement different password policies for administrative accounts on a "group" and "user" basis, instead of a single set of password settings to the whole domain. Failover Clustering Windows Server 2008 offers high availability to services and applications through Failover Clustering. Most server features and roles can be kept running with little to no downtime. In Windows Server 2008, the way clusters are qualified changed significantly with the introduction of the cluster validation wizard. The cluster validation wizard is a feature that is integrated into failover clustering in Windows Server 2008. With the cluster validation wizard, an administrator can run a set of focused tests on a collection of servers that are intended to use as nodes in a cluster. This cluster validation process tests the underlying hardware and software directly, and individually, to obtain an accurate assessment of how well failover clustering can be supported on a given configuration. This feature is only available in Enterprise and Datacenter editions of Windows Server. Disk management and file storage The ability to resize hard disk partitions without stopping the server, even the system partition. This applies only to simple and spanned volumes, not to striped volumes. Shadow Copy based block-level backup which supports optical media, network shares and Windows Recovery Environment. DFS enhancements - SYSVOL on DFS-R, Read-only Folder Replication Member. There is also support for domain-based DFS namespaces that exceed the previous size recommendation of 5,000 folders with targets in a namespace. Several improvements to Failover Clustering (high-availability clusters). Internet Storage Naming Server (iSNS) enables central registration, deregistration and queries for iSCSI hard drives. Self-healing NTFS: In Windows versions prior to Windows Vista, if the operating system detected corruption in the file system of an NTFS volume, it marked the volume "dirty"; to correct errors on the volume, it had to be taken offline. With self-healing NTFS, an NTFS worker thread is spawned in the background which performs a localized fix-up of damaged data structures, with only the corrupted files/folders remaining unavailable without locking out the entire volume and needing the server to be taken down. S.M.A.R.T. detection techniques were added to help determine when a hard disk may fail. Hyper-V Hyper-V is hypervisor-based virtualization software, forming a core part of Microsoft's virtualization strategy. It virtualizes servers on an operating system's kernel layer. It can be thought of as partitioning a single physical server into multiple small computational partitions. Hyper-V includes the ability to act as a Xen virtualization hypervisor host allowing Xen-enabled guest operating systems to run virtualized. A beta version of Hyper-V shipped with certain x86-64 editions of Windows Server 2008, prior to Microsoft's release of the final version of Hyper-V on 26 June 2008 as a free download. Also, a standalone variant of Hyper-V exists; this variant supports only x86-64 architecture. While the IA-32 editions of Windows Server 2008 cannot run or install Hyper-V, they can run the MMC snap-in for managing Hyper-V. Windows System Resource Manager Windows System Resource Manager (WSRM) is integrated into Windows Server 2008. It provides resource management and can be used to control the amount of resources a process or a user can use based on business priorities. Process Matching Criteria, which is defined by the name, type or owner of the process, enforces restrictions on the resource usage by a process that matches the criteria. CPU time, bandwidth that it can use, number of processors it can be run on, and allocated to a process can be restricted. Restrictions can be set to be imposed only on certain dates as well. Server Manager Server Manager is a new roles-based management tool for Windows Server 2008. It is a combination of Manage Your Server and Security Configuration Wizard from Windows Server 2003. Server Manager is an improvement of the Configure my server dialog that launches by default on Windows Server 2003 machines. However, rather than serve only as a starting point to configuring new roles, Server Manager gathers together all of the operations users would want to conduct on the server, such as, getting a remote deployment method set up, adding more server roles etc., and provides a consolidated, portal-like view about the status of each role. Protocol and cryptography Support for 128- and 256-bit AES encryption for the Kerberos authentication protocol. New cryptography (CNG) API which supports elliptic curve cryptography and improved certificate management. Secure Socket Tunneling Protocol, a new Microsoft proprietary VPN protocol. AuthIP, a Microsoft proprietary extension of the IKE cryptographic protocol used in IPsec VPN networks. Server Message Block 2.0 protocol in the new TCP/IP stack provides a number of communication enhancements, including greater performance when connecting to file shares over high-latency links and better security through the use of mutual authentication and message signing. Miscellaneous Fully componentized operating system. Improved hot patching, a feature that allows non-kernel patches to occur without the need for a reboot. Support for being booted from Extensible Firmware Interface (EFI)-compliant firmware on x86-64 systems. Dynamic Hardware Partitioning supports hot-addition or replacement of processors and memory, on capable hardware. Windows Deployment Services (WDS) replacing Automated Deployment Services Windows Server 2008 home entertainment and Remote Installation Services. Windows Deployment Services supports an enhanced multicast feature when deploying operating system images. Internet Information Services 7 - Increased security, Robocopy deployment, improved diagnostic tools, delegated administration. Windows Internal Database, a variant of SQL Server Express 2005, which serves as a common storage back-end for several other components such as Windows System Resource Manager, Windows SharePoint Services and Windows Server Update Services. It is not intended to be used by third-party applications. An optional "desktop experience" component provides the same Windows Aero user interface as Windows Vista, both for local users, as well as remote users connecting through Remote Desktop. Removed features The Open Shortest Path First (OSPF) routing protocol component in Routing and Remote Access Service was removed. Services for Macintosh, which provided file and print sharing via the now deprecated AppleTalk protocol, has been removed. Services for Macintosh were initially removed in Windows XP but were available in Windows Server 2003. NTBackup is replaced by Windows Server Backup, and no longer supports backing up to tape drives. As a result of NTBackup removal, Exchange Server 2007 does not have volume snapshot backup functionality; however Exchange Server 2007 SP2 adds back an Exchange backup plug-in for Windows Server Backup which restores partial functionality. Windows Small Business Server and Windows Essential Business Server both include this Exchange backup component. The POP3 service has been removed from Internet Information Services 7.0. The SMTP (Simple Mail Transfer Protocol) service is not available as a server role in IIS 7.0, it is a server feature managed through IIS 6.0. NNTP (Network News Transfer Protocol) is no longer part of Internet Information Services 7.0. ReadyBoost, which is available in Windows Vista, is not supported in Windows Server 2008. Support lifecycle Support for the RTM version of Windows Server 2008 ended on July 12, 2011, and users will not be able to receive further security updates for the operating system. As a component of Windows Vista, Windows Server 2008 will continue to be supported with security updates, lasting until January 14, 2020, the same respective end-of-life dates of Windows 7. Microsoft planned to end support for Windows Server 2008 on January 12, 2016. However, in order to give customers more time to migrate to newer Windows versions, particularly in developing or emerging markets, Microsoft decided to extend support until January 14, 2020. Microsoft announced that the Extended Security Updates (ESU) service will expire on January 10, 2023 (and on January 9, 2024, for Azure customers). Windows Server 2008 can be upgraded to Windows Server 2008 R2 on 64-bit systems only. Editions Most editions of Windows Server 2008 are available in x86-64 and IA-32 variants. These editions come in two DVDs: One for installing the IA-32 variant and the other for x64. Windows Server 2008 for Itanium-based Systems supports IA-64 processors. The IA-64 variant is optimized for high-workload scenarios like database servers and Line of Business (LOB) applications. As such, it is not optimized for use as a file server or media server. Windows Server 2008 is the last 32-bit Windows server operating system. Editions of Windows Server 2008 include: Windows Server 2008 Foundation (codenamed "Lima"; x86-64) for OEMs only Windows Server 2008 Standard (IA-32 and x86-64) Windows Server 2008 Enterprise (IA-32 and x86-64) Windows Server 2008 Datacenter (IA-32 and x86-64) Windows Server 2008 for Itanium-based Systems (IA-64) Windows Web Server 2008 (IA-32 and x86-64) Windows HPC Server 2008 (codenamed "Socrates"; replacing Windows Compute Cluster Server) Windows Storage Server 2008 (codenamed "Magni"; IA-32 and x86-64) Windows Small Business Server 2008 (codenamed "Cougar"; x86-64) for small businesses Windows Essential Business Server 2008 (codenamed "Centro"; x86-64) for medium-sized businesses - this edition was discontinued in 2010. The Microsoft Imagine program, known as DreamSpark at the time, used to provide verified students with the 32-bit variant of Windows Server 2008 Standard Edition, but the version has since then been removed. However, they still provide the R2 release. The Server Core feature is available in the Web, Standard, Enterprise and Datacenter editions. Windows Server 2008 Foundation Released on May 21, 2009. Updates Windows Server 2008 shares most of its updates with Windows Vista due to being based on that operating system's codebase. A workaround was found that allowed the installation of updates for Windows Server 2008 on Windows Vista, adding three years of security updates to that operating system (Support for Windows Vista ended on April 11, 2017, while support for Windows Server 2008 ended on January 14, 2020). Service Pack 2 Due to the operating system being based on the same codebase as Windows Vista and being released on the same day as the initial release of Windows Vista Service Pack 1, the RTM release of Windows Server 2008 already includes the updates and fixes of Service Pack 1. Service Pack 2 was initially announced on October 24, 2008 and released on May 26, 2009. Service Pack 2 added new features, such as Windows Search 4.0, support for Bluetooth 2.1, the ability to write to Blu-ray discs, and simpler Wi-Fi configuration. Windows Server 2008 specifically received the final release of Hyper-V 1.0, improved backwards compatibility with Terminal Server license keys and an approximate 10% reduction in power usage with this service pack. Windows Vista and Windows Server 2008 share the same service pack update binary because the codebases of the two operating systems are unified - Windows Vista and Windows Server 2008 are the first Microsoft client and server operating systems to share the same codebase since the release of Windows 2000. The predecessors to Windows Vista and Windows Server 2008, Windows XP and Windows Server 2003, had unique codebases that used their own updates and service packs. Platform Update On October 27, 2009, Microsoft released the Platform Update for Windows Server 2008 and Windows Vista. It backports several APIs and libraries introduced in Windows Server 2008 R2 and Windows 7 to Windows Server 2008 and Windows Vista, including the Ribbon API, DirectX 11, the XPS library, the Windows Automation API and the Portable Device Platform. A supplemental update was released in 2011 to provide improvements and bug fixes. Internet Explorer 9 Windows Server 2008 shipped with Internet Explorer 7, the same version that shipped with Windows Vista. The last supported version of Internet Explorer for Windows Server 2008 is Internet Explorer 9, released in 2011. Internet Explorer 9 was continually updated with cumulative monthly update rollups until support for Internet Explorer 9 on Windows Server 2008 ended on January 14, 2020. .NET Framework The latest supported version of the .NET Framework officially is version 4.6, released on October 15, 2015. TLS 1.1 and 1.2 support In July 2017, Microsoft released an update to add TLS 1.1 and 1.2 support to Windows Server 2008, however it is disabled by default after installing the update. SHA-2 signing support Starting in March 2019, Microsoft began transitioning to exclusively signing Windows updates with the SHA-3 algorithm. As a result of this Microsoft released several updates throughout 2019 to add SHA-2 signing support to Windows Server 2008. Monthly update rollups In June 2018, Microsoft announced that they would be moving Windows Server 2008 to a monthly update model beginning with updates released in September 2018 - two years after Microsoft switched the rest of their supported operating systems to that model. With the new update model, instead of updates being released as they became available, only two update packages were released on the second Tuesday of every month until Windows Server 2008 reached its end of life - one package containing security and quality updates, and a smaller package that contained only the security updates. Users could choose which package they wanted to install each month. Later in the month, another package would be released which was a preview of the next month's security and quality update rollup. Installing the preview rollup package released for Windows Server 2008 on March 19, 2019, or any later released rollup package, will update the operating system kernel's build number from version 6.0.6002 to 6.0.6003. This change was made so Microsoft could continue to service the operating system while avoiding “version-related issues”. The last free security update rollup packages were released on January 14, 2020. Extended Security Updates Windows Server 2008 is eligible for the Extended Security Updates program. This program allows volume license customers to purchase, in yearly installments, security updates for the operating system until at most January 10, 2023. The licenses are paid for on a per-machine basis. If a user purchases an Extended Security Updates license in a later year of the program, they must pay for any previous years of Extended Security Updates as well. Extended Security Updates are released only as they become available. Windows Server 2008 R2 A second release of Windows Server 2008, called the Windows 7-based Windows Server 2008 R2 was released to manufacturing on July 22, 2009 and became generally available on October 22, 2009. New features added in Windows Server 2008 R2 include new virtualization features, new Active Directory features, Internet Information Services 7.5 and support for up to 256 logical processors. It is the first server operating system by Microsoft to exclusively support 64-bit processors. A service pack for Windows 7 and Windows Server 2008 R2, formally designed Service Pack 1, was released in February 2011. System requirements System requirements for Windows Server 2008 are as follows: Scalability Windows Server 2008 supports the following maximum hardware specifications: See also BlueKeep (security vulnerability) Comparison of Microsoft Windows versions Comparison of operating systems History of Microsoft Windows List of operating systems Microsoft Servers Notes References Further reading External links Windows Server Performance Team Blog 2008 software IA-32 operating systems X86-64 operating systems

Operating System (OS)

System Information (Mac) System Information (previously known as System Profiler) is a software utility derived from field service diagnostics produced by Apple's Service Diagnostic Engineering team, at that time located in Apple satellite buildings in Campbell, California, that was bundled with the classic Mac OS since Mac OS 7.6 under the name Apple System Profiler. In Mac OS X 10.0, the first release of macOS, it was renamed System Profiler; with the release of Mac OS X 10.7 "Lion" it was again renamed to System Information. Other new features in Lion are the ability to look up support information for the user's hardware model as well. In OS X Mountain Lion and later versions of macOS users can also access System Information by holding down the option key and "System Information..." will replace "About This Mac" in the Apple Menu. It compiles technical information on all of the installed hardware, devices, drivers, applications, system settings, system software programs and kernel extensions installed on the host computer. It can export this information as plain text, RTF or in the plist XML format. This information is used to diagnose problems. System Profiler can be extremely useful if attempting to diagnose a hardware problem. A user can send the information directly to Apple if the user desires. It has support for scripting automation through AppleScript and some limited support in Automator. System information can also be accessed by using the "system_profiler" command through a Terminal application. For more information, execute man system_profiler or "system_profiler -h" in a macOS terminal application. References External links Apple's System Profiler Manual Page MacOS Macintosh operating systems

Operating System (OS)

SINIX SINIX is a discontinued variant of the Unix operating system from Siemens Nixdorf Informationssysteme. SINIX supersedes SIRM OS and Pyramid Technology's DC/OSx. Following X/Open's acceptance that its requirements for the use of the UNIX trademark were met, version 5.44 and subsequent releases were published as Reliant UNIX by Fujitsu Siemens Computers. Features In some versions of SINIX (5.2x) the user could emulate the behaviour of a number of different versions of Unix (known as universes). These included System V.3, System III or BSD. Each universe had its own command set, libraries and header files. Xenix-based SINIX The original SINIX was a modified version of Xenix and ran on Intel 80186 processors. For some years Siemens used the NSC-32x32 (up to Sinix 5.2x) and Intel 80486 CPUs (Sinix 5.4x - non MIPS) in their MX-Series. System V-based SINIX Later versions of SINIX based on System V were designed for the: SNI RM-200, RM-300, RM-400 and RM-600 servers running on the MIPS processor (SINIX-N, SINIX-O, SINIX-P, SINIX-Y) SNI PC-MX2, MX300-05/-10/-15/-30, Siemens MX500-75/-85 running NS320xx (SINIX-H) PC-MXi, MX300-45 on the Intel X86 processor (SINIX-L) SNI WX-200 and other IBM-compatible i386 PCs on the Intel 80386 and newer processors (SINIX-Z) The last release under the SINIX name was version 5.43 in 1995. Reliant UNIX The last Reliant UNIX versions were registered as UNIX 95 compliant (XPG4 hard branding). The last release of Reliant UNIX was version 5.45. See also BS2000 VM2000 External links Siemens Business Services - SINIX patches and support The SINIX operating system Sven Mascheck, SINIX V5.20 Universes MIPS operating systems UNIX System V

Operating System (OS)

Sailfish OS Sailfish OS is a Linux-based operating system based on free software, and open source projects such as Mer as well as including a closed source UI. The project is being developed by the Finnish company Jolla. The OS first shipped with the original Jolla Phone in 2013 (its sale stopped in 2016, but it was supplied with software updates until the end of 2020), then the Jolla Tablet in 2015 and from other vendors licensing the OS. The OS is ported by community enthusiasts to third-party mobile devices including smartphones and tablet computers. Sailfish OS can be used for many kinds of devices. History and development The OS is an evolved continuation of the Linux MeeGo OS previously developed by alliance of Nokia and Intel which itself relies on combined Maemo and Moblin. The MeeGo legacy is contained in the Mer core in about 80% of its code; the Mer name thus expands to MEego Reconstructed. This base is extended by Jolla with a custom user interface and default applications. Jolla and MERproject.org follow a meritocratic system to avoid the mistakes that led to the MeeGo project's then-unanticipated discontinuation. The main elements for include: Technically stronger OS core Improved Android application compatibility Support for ARM and Intel architectures, including the Intel Atom x3 processor, or any platform with kernel useable (settle-able) for MER core stack (also called middleware of Sailfish). Design to provide visibility in the UI for digital content providers and to enable OS level integration for mobile commerce Strong multitasking (one of the most important advantage of the OS and declared to be the best one on the market) Strong privacy and personalization features Enhanced user interface with new UI/UX features, including simpler swipe access to main functions, enhanced notifications and events views. Software architecture The and the Sailfish software development kit (SDK) are based on the Linux kernel and Mer. includes a multi-tasking graphical shell called "Lipstick" built with Qt by Jolla on top of the Wayland display server protocol. Jolla uses free and open-source graphics device drivers but the Hybris library allows use of proprietary drivers for Android. Jolla's stated goal is for Sailfish to be open source eventually. can run some Android applications through a proprietary compatibility layer. Targeted device classes Sailfish is targeted at mobile devices, but since it inherited around 80% of MeeGo code, Sailfish can be used as a complete general-purpose Linux OS on devices including in vehicle infotainment (IVI), navigation, smart TV, desktops and notebooks, yachts, automotive, e-commerce, home appliances, measuring and control equipment, smart building equipment, etc. See use cases of original MeeGo to compare, and the Devices section for devices that run the . Sailfish OS SDK The SDK was announced at the Slush Helsinki conference in 2012, and the alpha was published in February 2013. The SDK, installation and coding tutorials are available for free download from the website despite the overall license not being open source. Sailfish SDK uses Qt with VirtualBox for development, compiling and emulation purposes, in contrast to the simulation method. This technique allows compilation on the and full testing of developed software in the virtual machine, emulatingnot simulatingthe whole . This also separates development activities and side effects from everything else running on the host computer, leaving it undisturbed by developments and tests. According to Jolla, development with Sailfish SDK is development on itself; there are no differences between developed software appearance and behaviour in the SDK and on a device running . The availability of source code to the SDK allows shaping and rebuilding to companies' or developers' specific needs, creating a context-specific environment that is set once and needs no preparation when the device is booted. The SDK runs on the operating systems Android, 32- and 64-bit versions of Linux, 64-bit versions of OS X, and Microsoft Windows. It can be used for compiling software for devices from Linux sources. Its general console/terminal mode follows a commonly used standard. Compatible binaries or libraries can also be used. Application programming interfaces uses open source Qt APIs (Qt 5, QtQuick 2 etc.) and a closed source Sailfish Silica for the UI. Standard Linux APIs are provided by the Mer Core. Sailfish, Ubuntu and Plasma Active have been cooperating to share common APIs. When successful, this will make the platforms compatible on the API level. Sailfish Browser is the default web browser based on Gecko and using embedlite (also known as IPCLiteAPI), a lite-weight embedding API from Mozilla. Software overview UI supported human languages Officially Jolla declares supporting the following 14 languages for the user interface: Danish, German, English (UK), Spanish, French, Italian, Norwegian, Polish, Portuguese, Finnish, Swedish, Russian, Chinese (mainland), and Chinese (Hong Kong). For each of them, the OS has a dedicated keyboard. There are a few more languages which are unofficially supported by community freelancers not under control by Jolla, hence more than 20 languages are supported in total. Additional languages can be installed by skilled users due to the Linux architecture. Public "Early access" for beta testers and developers After positive experiences with pushing early updates to a small group of opt-in users for Sailfish Update 9 and for the connectivity hotfix, Jolla has allowed all interested parties to try a new version of about 1–2 weeks before official release, in a program called "Early access". It is expected to be useful for developers and technically minded users, and a step towards more community integration into the Sailfish release process, including improvement of quality by identifying critical issues which only show up in certain environments or device setups, before rolling the update out to the wider user audience. As an added bonus, it provides a window for developers to test their applications on new releases of . In the long term it will help Jolla to establish a developer program with early release candidate access for registered developers, and to have more community involvement in platform development. The first detail Jolla is hoping to learn from this is how it can gather feedback from a large audience in a reasonable way. Basic details about the early access update: The early release access is meant primarily for advanced users and developers. To sign up for the program there is a checkbox in the Jolla accounts profile page. Installed early-access release cannot be downgraded. The only way to downgrade from early access releases is to do a factory reset after removing the sign up check from the user's account profile. Early access releases should be considered "reasonably stable". Issues found during that period will either be fixed, or added to "known issues" on the release notes. Signing up for the early access releases will not void warranty. Version history has three naming conventions: version number, update number and version name. Sailfish OS 1.0 versions were named after Finnish lakes. Sailfish OS 2.0 supports the Jolla Tablet with x86 platforms and featured a reworked touch based UI. Releases were named after Finnish rivers. Sailfish OS 3.0 and 4.0 features a slightly reworked UI. Releases are named after Finnish national parks. Sailfish OS 4.1, 4.2 and 4.3 features 64 bit support on the Sony Xperia 10 II, plus a new sharing system. Releases are named after Finnish Unesco world heritage sites. Stop releases When updating an installed Sailfish OS from an earlier release, for example after device factory reset, there are several stop releases which must not be skipped and have to be installed before continuing on the path to subsequent releases. These releases provide new functionality that is not compatible with previous releases and have to be traversed in order not to put the Sailfish OS installation into an unstable state. Porting The Sailfish website publishes an online compendium of knowledge, links and instructions on porting issues. Using Android software running on In addition to its native applications, Sailfish can run some Android applications by installing them from an application store or directly through an APK file. Supported Android versions are 4.1.2 "Jelly Bean" on the original Jolla phone; 4.4.4 "Kit-Kat" on the Jolla C, Jolla tablet and Xperia X; 8.1.0 "Oreo", 9 "Pie" and 10 (depending on the Sailfish OS release) on Xperia XA2, Xperia 10 and Xperia 10 II. Problems can arise if these applications were built without following Android standards about controls, which might not display correctly and so become unusable. Sailfish OS uses Alien Dalvik, a proprietary Android compatibility layer. It does not emulate Android, but instead implements its APIs by adapting the Android Open Source Project (AOSP) code to run as an application. Android applications can thus run at native speed without any perceivable slow-down. Sailfish can run both native Sailfish and Android software simultaneously, with the user switching between them on the fly. Starting with Alien Dalvik 8.1 (also called "Android App Support" since then), it uses LXC to improve security by better isolation, in the same way the open source Android compatibility layer Anbox is doing. Hardware overview Advantages of the Mer standard can be used on any hardware with Linux-kernel support and compatible with the middleware utilising the Mer core. Community enthusiasts have ported to a number of devices this way. Instead of designation to a specific reference hardware platform, a VirtualBox implementation with the SDK is available for development on Linux, OS X and Windows operating systems. This virtual machine implementation contains the whole isolated from local resources and the local OS to enable convenient evaluation of the behaviour and performance of coded or ported software before deployment on real devices. Jolla devices Jolla C Jolla Tablet Jolla Phone Devices from other vendors licensing Manufacturers can provide mobile equipment with a licensed , or as open source, or combining both and including their own or the operator's modifications and branding for specific markets or purposes. Sony Xperia 10 II – via Sailfish X Sony Xperia 10 Plus – via Sailfish X Sony Xperia 10 – via Sailfish X Planet Computers Gemini PDA – via Sailfish X Sony Xperia XA2 Plus – via Sailfish X Sony Xperia XA2 Ultra – via Sailfish X Sony Xperia XA2 – via Sailfish X Sony Xperia X – via Sailfish X Community enthusiasts' ports to devices from other vendors Due to the relative ease of porting and the open source license, has also been unofficially ported to other 3rd-party devices. The Hardware Adaptation Development Kit for porters has been published and is free. These ports are mostly published on the Maemo and XDA Developers forums, and in the Mer wiki a list of the ports is compiled. Due to license restrictions, proprietary parts or extensions such as the Alien Dalvik compatibility layer for Android apps are not included. However they can be added, e.g. when a manufacturer or distributor turns it from the community version into an officially supported version for a particular device. From the originally more than 80 ports, there are about 19 ports that are still in active development – as of March 2019 – meaning they have been updated to Sailfish 3: Alcatel Idol 3 Fairphone 2 F(x)tec Pro1 HP TouchPad Motorola Moto Z Play Motorola Photon Q Motorola Moto X Force Motorola Moto X 2014 Motorola Moto G 2014 Motorola Moto G 2015 Motorola Moto G4 Plus OnePlus X OnePlus One OnePlus 3 OnePlus 3T OnePlus 5 OnePlus 5T PinePhone Samsung Galaxy A5 Sony Xperia X Compact Xiaomi Redmi 2 Xiaomi Redmi Note 3 Xiaomi Redmi Note 4 Xiaomi Redmi 5 Plus Xiaomi Redmi 4X To display the ease of porting to other devices, Jolla showed created ports and community ports at events like the Mobile World Congress, Slush and FOSDEM: Nokia N950 Nokia N9 Google Nexus 7 Google Nexus 4 Samsung Galaxy S3 Xiaomi Mi 2 TCL Idol X950 Google Nexus 5 Fairphone 2 Sony Xperia X Jolla Sailfish Watch Sony Xperia XA2 Planet Computers Gemini PDA a feature phone similar to the Nokia 3310 assumed to be the Chinese Kingsun EF33 OS development status is promoted by Jolla and supported by the open Sailfish Alliance established in 2011, a group established to unite OEM and ODM manufacturers, chipset providers, operators, application developers and retailers. On 16 August 2012, the user interface was reported to be ready for release. Jolla's CEO Jussi Hurmola stated in a ZDNet interview, " ... Our UI is ready now, we haven't released it yet, we will save it for the product launch and the platform is getting up now so the project looks pretty nice". The next day, Jolla's CEO Marc Dillon said on social networking website Twitter that the company had reached the first development target. Sailfish was debuted by the Jolla team, including a worldwide internet stream, as a demo of the OS, and the UI and SDK during the Slush event in Helsinki, Finland, on 21–22 November 2012. The alpha stage of SDK was published at the end of February 2013 and was made available for free download. On 16 September 2013, Jolla announced that its OS had been made compatible with Android applications and hardware. The first telephone to use it was launched on 27 November 2013 at a pop-up DNA Kauppa shop in Helsinki. The first 450 telephones were sold at this event, while the rest of the preordered devices were shipped shortly after. In August 2015, version 1.1.9 "Eineheminlampi" was released, which added the main elements of the revamped user interface. was launched with the Jolla Tablet, and existing devices, both smartphones and tablets, from Jolla's official distribution channels are supported with upgrade to and following updates. In May 2016 Jolla announced the Sailfish Community Device Program, supporting developers and members of community. Aurora OS Jolla staff met with members of the Russian technology community to break ground on the new software and promote , as part of Jolla's BRICS strategy. As a result of those efforts, on 18 May 2015 the Russian minister of communications Nikolai Nikiforov announced plans to replace Apple's iOS and Google's Android platforms with new software based on Sailfish. He intends it to cover 50% of Russian needs in this area during next ten years, in comparison to the 95% currently covered with western technology. The Russian version is currently being developed under the brand name Mobile OS "Aurora" (мобильная ОС «Аврора»), before 2019 as "Sailfish Mobile OS RUS". The Chinese multinational technology company Huawei was in talks with the Russian Ministry of Communications to install Aurora OS on tablets for Russia’s population census by August 2020. Jolla has cut business ties with Russia in 2021 Sailfish Alliance Sailfish Alliance is the open alliance established in 2011 by Jolla company to support the MeeGo ecosystem with new products, services and business opportunities around or using Sailfish OS, a Linux operating system combining Mer with proprietary components from Jolla and other parties, for various purposes and mobile devices. The alliance is seen as a competitor to other groups like Android's Open Handset Alliance. In 2011 some of the MeeGo team working at Nokia left, and were funded by Nokia though their "Bridge" program to fund spin-out projects by ex-employees. The Sailfish Alliance has sought to collaborate between the Finnish software developers, and overseas handset manufacturers, some of which are in China. The news media reports that a number of manufacturers in China and India want an alternative to Android. The Alliance aims to "unite OEM and ODM manufacturers, chipset providers, operators, application developers and retailers." Business strategy The aim of the Alliance is to offer unique differentiation opportunities and sustainable competitive advantage for OEM and ODM manufacturers, chipset providers, operators, application developers, retailers and other interested in sides. Sailfish Secure The Sailfish Secure is the first open and secure mobile phone platform, based on Sailfish OS. It was introduced publicly in Barcelona, Spain at Mobile World Congress on 2 March 2015 where plans for the Sailfish Secure were presented. It is based on a security-hardened version of the Sailfish OS and SSH's communication encryption and key management platform. Developed by Jolla (the Sailfish OS designer and developer) together with SSH Communications Security (the inventor of Secure Shell SSH protocol) in collaboration of Sailfish Alliance. The hardware platform independent approach of the Sailfish Secure allow concept adaptation to local needs, and also in collaboration with other security partners. End customers like governments or large corporations are able to adapt the solution to their preferred or used hardware platform, as it is not tied to a specific hardware or configuration. The aim is to answer increasing demand in privacy in mobile communications. Jolla and Sailfish OS has unique position to create and provide an alternative solution on markets dominated by Android or other non-EU based OSes. Target customers need a secure mobile solution, including government officials or corporations, but it is also to be the solution affordable for consumers. See also Comparison of mobile operating systems Hongmeng OS KaiOS Nokia Asha platform Nokia X platform References External links SailfishOSwiki, a site hosting documentation Building packages manually (including porting over existing applications that use a different build system) Jolla website OpenRepos.net Why Sailfish is better as a modern OS? Here is a comparison FlyingSheep on Sailfisha good reading for developers and porting from MeeGo Harmattan to ARM operating systems Embedded Linux distributions Finnish brands Free mobile software MeeGo Mobile Linux Mobile operating systems Smartphones Software that uses QML X86-64 Linux distributions X86-64 operating systems Linux distributions

Operating System (OS)

Criticism of Microsoft Windows The various versions of Microsoft's desktop operating system, Windows, have received many criticisms since Microsoft's inception. Patch time In 2010, Google engineer Tavis Ormandy criticized Microsoft for taking too long to patch (fix) a reported security vulnerability in the Windows virtual DOS machine (VDM), which was patched 7 months after Mr. Ormandy reported it to Microsoft. In 2004, Marc Maiffret, chief hacking officer for security research firm eEye Digital Security, had criticized Microsoft for providing a security patch for the Windows ASN.1 implementation only after 200 days. Digital rights management Right after the release of Windows Vista, computer scientist Peter Gutmann criticised the digital rights management (DRM) that had been included in Microsoft Windows to allow content providers to place restrictions on certain types of multimedia playback. He collected the criticism in a write-up he released in which he stated that: The DRM could inadvertently disable functionality. A hardware functionality scan requirement could potentially shut out open-source hardware. The hardware architecture made unified drivers impossible. Some drivers were buggy. If one driver was found to be leaking content, Microsoft could remotely shut that driver down for all computers that used it, leading to denial of service problems. The DRM decreased system reliability and increased hardware costs. Software makers had to license unnecessary third-party intellectual property, increasing the costs for their drivers. The DRM consumed too much CPU and device resources. The analysis drew responses from Microsoft, where Microsoft states some of the criticized DRM features were already present in Windows XP, and thus a new problem for customers and that these problematic features would only be activated when required by the content being played. Other responses came from George Ou of ZDNet and Ed Bott of ZDNet. Ed Bott also published a three-part rebuttal of Peter Gutmann's claims in which he details a number of factual errors in the analysis and criticizes Gutmann's reliance on questionable sources (personal blog postings, friends' anecdotal evidence, Google searches) for his analysis paper and that Gutmann never tested his theories himself. For Windows 7, allegations were also made about "draconian DRM" which spurred a debate and criticism on the website Slashdot. As with the claims about the overreaching Vista DRM, independent tech writers quickly dismissed the claims as faulty analysis. The actual problem which spurred the criticism turned out to be an unrelated problem experienced by a single user who tried to circumvent Adobe Creative Suite copy protection mechanisms by changing files. When it failed to work, the user concluded that it had to be the "draconian DRM" of Windows. Integration of Internet Explorer into Windows Windows is criticized for having the Internet Explorer web browser integrated into the Windows shell from Windows 98 onwards. Previously Internet Explorer was shipped as a separate application. One problem was that since the Explorer cannot be easily replaced with a product of another vendor, this undermines consumer choice. This issue precipitated concerns that Microsoft engages in monopolistic practices and resulted in the United States v. Microsoft Corp. court case, which was eventually settled out of court. Another issue with the integration was that security vulnerabilities in Internet Explorer also create security vulnerabilities in Windows, which could allow an attacker to exploit Windows with remote code execution. In January 2009, the European Commission started to investigate Microsoft's bundling of Internet Explorer into Windows; the Commission stated: "Microsoft's tying of Internet Explorer to the Windows operating system harms competition between web browsers, undermines product innovation and ultimately reduces consumer choice." The European Commission and Microsoft eventually agreed that Microsoft would include a web browser choice selection screen to Windows users in the European Economic Area, by means of BrowserChoice.eu. Windows 10 includes Internet Explorer, but switched to Microsoft Edge as the default browser. Windows 11 removes Internet Explorer, outside of Edge's Internet Explorer mode for legacy applications. Windows rot Google, a Microsoft competitor, has criticized Windows for becoming slower and less reliable over long term use. Adrian Kingsley-Hughes, writing for ZDNet, believes that the slow-down over time is due to loading too much software, loading duplicate software, installing too much free/trial/beta software, using old, outdated or incorrect drivers, installing new drivers without uninstalling the old ones and may also be due to malware and spyware. NSA backdoor allegations In 1999 Andrew Fernandez, chief scientist with Cryptonym of Morrisville, North Carolina found a cryptographic public key stored in the variable _KEY and a second key labeled NSAKEY. The discovery lead to a flurry of speculation and conspiracy theories; such as the second key could be owned by the United States National Security Agency (the NSA), and that it could allow the intelligence agency to subvert any Windows user's security. Also researcher Dr. Nicko van Someren discovered these cryptographic keys and a third key in the ADVAPI.DLL file which, at that time, existed in Windows 2000 before its release. Concerns were raised about CPUs with encrypted instruction sets which, if they existed during that time, would have made it impossible to discover the cryptographic keys. Microsoft denied the allegations, attributing the naming of the key to a technical review by the NSA pointing out a backup key was required to conform to regulations. No evidence other than the name of the key has ever been presented that the key enabled a backdoor. Cryptographer and computer security specialist Bruce Schneier has also argued against the conspiracy theory pointing out that if the NSA wanted a back door into Windows with Microsoft's consent, they would not need their own cryptographic key to do so. The cryptographic keys have been included in all versions of Windows from Windows 95 OSR2 onwards. Data collection Concerns were shown by advocates and other critics for Windows 10's privacy policies and its collection and use of customer data. Under the default "Express" settings, Windows 10 is configured to send various information to Microsoft and other parties, including the collection of user contacts, calendar data, and "associated input data" to personalize "speech, typing, and inking input", typing and inking data to improve recognition, allow apps to use a unique "advertising ID" for analytics and advertising personalization (functionality introduced by Windows 8.1) and allow apps to request the user's location data and send this data to Microsoft and "trusted partners" to improve location detection (Windows 8 had similar settings, except that location data collection did not include "trusted partners"). Users can opt out from most of this data collection, but telemetry data for error reporting and usage is also sent to Microsoft, and this cannot be disabled on non-Enterprise versions of Windows 10. The use of Cortana intelligent personal assistant also requires the collection of data "such as your device location, data from your calendar, the apps you use, data from your emails and text messages, who you call, your contacts and how often you interact with them on your device" to personalize its functionality. Rock Paper Shotgun writer Alec Meer argued that Microsoft's intent for this data collection lacked transparency, stating that "there is no world in which 45 pages of policy documents and opt-out settings split across 13 different Settings screens and an external website constitutes 'real transparency'." ExtremeTech pointed out that, whilst previously campaigning against Google for similar data collection strategies, "[Microsoft] now hoovers up your data in ways that would make Google jealous." However, it was also pointed out that the requirement for such vast usage of customer data had become a norm, citing the increased reliance on cloud computing and other forms of external processing, as well as similar data collection requirements for services on mobile devices such as Google Now and Siri. In August 2015, Russian politician Nikolai Levichev called for Windows 10 to be banned from use by the Russian government, as it sends user data to servers in the United States (a federal law requiring all online services to store the data of Russian users on servers within the country, or be blocked, has taken effect September 2016). Following the release of 10, allegations also surfaced that Microsoft had backported the operating system's increased data collection to Windows 7 and Windows 8 via "recommended" patches that added additional "telemetry" features. The updates' addition of a "Diagnostics Tracking Service" is connected specifically to Microsoft's existing Customer Experience Improvement Program (which is an opt-in program that sends additional diagnostic information to Microsoft for addressing issues), and the Application Insights service for third-party software. The data collection functionality is capable of transmitting personal information, browsing history, the contents of emails, chat, video calls, voice mail, photos, documents, personal files and keystrokes to Microsoft, for analysis, in accordance with the End User License Agreement. The terms of services agreement from Microsoft was updated to state the following: See also Criticism of Microsoft Criticism of Windows XP Criticism of Windows Vista Criticism of Windows 10 DLL Hell UEFI secure boot criticism References Microsoft Windows Microsoft Windows Windows

Operating System (OS)

Inferno (operating system) Inferno is a distributed operating system started at Bell Labs and now developed and maintained by Vita Nuova Holdings as free software under the MIT license. Inferno was based on the experience gained with Plan 9 from Bell Labs, and the further research of Bell Labs into operating systems, languages, on-the-fly compilers, graphics, security, networking and portability. The name of the operating system and many of its associated programs, as well as that of the current company, were inspired by Dante Alighieri's Divine Comedy. In Italian, Inferno means "hell" — of which there are nine circles in Dante's Divine Comedy. Design principles Inferno was created in 1995 by members of Bell Labs' Computer Science Research division to bring ideas of Plan 9 from Bell Labs to a wider range of devices and networks. Inferno is a distributed operating system based on three basic principles drawn from Plan 9: Resources as files: all resources are represented as files within a hierarchical file system Namespaces: a program's view of the network is a single, coherent namespace that appears as a hierarchical file system but may represent physically separated (locally or remotely) resources Standard communication protocol: a standard protocol, called Styx, is used to access all resources, both local and remote To handle the diversity of network environments it was intended to be used in, the designers decided a virtual machine was a necessary component of the system. This is the same conclusion of the Oak project that became Java, but arrived at independently. The Dis virtual machine is a register machine intended to closely match the architecture it runs on, as opposed to the stack machine of the Java Virtual Machine. An advantage of this approach is the relative simplicity of creating a just-in-time compiler for new architectures. The virtual machine provides memory management designed to be efficient on devices with as little as 1 MiB of memory and without memory-mapping hardware. Its garbage collector is a hybrid of reference counting and a real-time coloring collector that gathers cyclic data. The Inferno kernel contains the virtual machine, on-the-fly compiler, scheduler, devices, protocol stacks, and the name space evaluator for each process' file name space, and the root of the file system hierarchy. The kernel also includes some built-in modules that provide interfaces of the virtual operating system, such as system calls, graphics, security, and math modules. The Bell Labs Technical Journal paper introducing Inferno listed several dimensions of portability and versatility provided by the OS: Portability across processors: it currently runs on ARM, SGI MIPS, HP PA-RISC, IBM PowerPC, Sun SPARC, and Intel x86 architectures and is readily portable to others. Portability across environments: it runs as a stand-alone operating system on small terminals, and also as a user application under Bell Plan 9, MS Windows NT, Windows 95, and Unix (SGI Irix, Sun Solaris, FreeBSD, Apple Mac OS X, Linux, IBM AIX, HP-UX, Digital Tru64). In all of these environments, Inferno programs see an identical interface. Distributed design: the identical environment is established at the user's terminal and at the server, and each may import the resources (for example, the attached I/O devices or networks) of the other. Aided by the communications facilities of the run-time system, programs may be split easily (and even dynamically) between client and server. Minimal hardware requirements: it runs useful applications stand-alone on machines with as little as 1 MiB of memory, and does not require memory-mapping hardware. Portable programs: Inferno programs are written in the type-safe language Limbo and compiled to Dis bytecode, which can be run without modifications on all Inferno platforms. Dynamic adaptability: programs may, depending on the hardware or other resources available, load different program modules to perform a specific function. For example, a video player might use any of several different decoder modules. These design choices were directed to provide standard interfaces that free content and service providers from concern of the details of diverse hardware, software, and networks over which their content is delivered. Features Inferno programs are portable across a broad mix of hardware, networks, and environments. It defines a virtual machine, known as Dis, that can be implemented on any real machine, provides Limbo, a type-safe language that is compiled to portable byte code, and, more significantly, it includes a virtual operating system that supplies the same interfaces whether Inferno runs natively on hardware or runs as a user program on top of another operating system. A communications protocol called Styx is applied uniformly to access both local and remote resources, which programs use by calling standard file operations, open, read, write, and close. As of the fourth edition of Inferno, Styx is identical to Plan 9's newer version of its hallmark 9P protocol, 9P2000. Most of the Inferno commands are very similar to Unix commands with the same name. History Inferno is a descendant of Plan 9 from Bell Labs, and shares many design concepts and even source code in the kernel, particularly around devices and the Styx/9P2000 protocol. Inferno shares with Plan 9 the Unix heritage from Bell Labs and the Unix philosophy. Many of the command line tools in Inferno were Plan 9 tools that were translated to Limbo. In the mid-1990s, Plan 9 development was set aside in favor of Inferno. The new system's existence was leaked by Dennis Ritchie in early 1996, after less than a year of development on the system, and publicly presented later that year as a competitor to Java. At the same time, Bell Labs' parent company AT&T licensed Java technology from Sun Microsystems. In March–April 1997 IEEE Internet Computing included an advertisement for Inferno networking software. It claimed that various devices could communicate over "any network" including the Internet, telecommunications and LANs. The advertisement stated that video games could talk to computers,–a PlayStation was pictured–cell phones could access email and voice mail was available via TV. Lucent used Inferno in at least two internal products: the Lucent VPN Firewall Brick, and the Lucent Pathstar phone switch. They initially tried to sell source code licenses of Inferno but found few buyers. Lucent did little marketing and missed the importance of the Internet and Inferno's relation to it. During the same time Sun Microsystems was heavily marketing its own Java programming language, which was targeting a similar market, with analogous technology, that worked in web browsers and also filled the demand for object-oriented languages popular at that time. Lucent licensed Java from Sun, claiming that all Inferno devices would be made to run Java. A Java byte code to Dis byte code translator was written to facilitate that. However, Inferno still did not find customers. The Inferno Business Unit closed after three years, and was sold to Vita Nuova. Vita Nuova continued development and offered commercial licenses to the complete system, and free downloads and licenses (not GPL compatible) for all of the system except the kernel and VM. They ported the software to new hardware and focused on distributed applications. Eventually, Vita Nuova released the 4th edition under more common free software licenses, and in 2021 they relicensed all editions under mainly the MIT license. Ports Inferno runs directly on native hardware and also as an application providing a virtual operating system which runs on other platforms. Programs can be developed and run on all Inferno platforms without modification or recompilation. Native ports include these architectures: x86, MIPS, ARM, PowerPC, SPARC. Hosted or virtual OS ports include: Microsoft Windows, Linux, FreeBSD, Plan 9, Mac OS X, Solaris, IRIX, UnixWare. Inferno can also be hosted by a plugin to Internet Explorer. Vita Nuova said that plugins for other browsers were under development, but they were never released. Inferno has also been ported to Openmoko, Nintendo DS, SheevaPlug, and Android. Distribution Inferno 4th edition was released in early 2005 as free software. Specifically, it was dual-licensed under two structures. Users could either obtain it under a set of free software licenses, or they could obtain it under a proprietary license. In the case of the free software license scheme, different parts of the system were covered by different licenses, including the GNU General Public License, the GNU Lesser General Public License, the Lucent Public License, and the MIT License, excluding the fonts, which are sub-licensed from Bigelow and Holmes. In March 2021, all editions were relicensed under mainly the MIT license. See also Language-based system Singularity (operating system) Notes References Further reading describes the 3rd edition of the Inferno operating system, though it focuses more on the Limbo language and its interfaces to the Inferno system, than on the Inferno system itself. For example, it provides little information on Inferno's versatile command shell, which is understandable since it is a programming language textbook. , uses Inferno for examples of operating system design. was intended to provide an operating-system-centric point of view, but was never completed. External links Documentation papers for the latest inferno release. Inferno Fourth Edition Download, including source code. Mailing list and other resources. Ninetimes: News and articles about Inferno, Plan 9 and related technologies. Inferno programmer's notebook - A journal made by an Inferno developer. Try Inferno: free, in-browser access to a live Inferno system. Inferno OS to Raspberry Pi Labs: Porting Inferno OS to Raspberry Pi 1996 software ARM operating systems Distributed operating systems Embedded operating systems Real-time operating systems X86 operating systems PowerPC operating systems MIPS operating systems

Operating System (OS)

UXP/DS UXP/DS is a discontinued Unix operating system developed by Fujitsu for its line of workstations and network servers. UXP/DS is based on AT&T System V Release 4 (SVR4), and targets Fujitsu's DS/90 7000 series of computers, as well as some GP7000 series computers. History In 1991, Fujitsu announced the DS/90 7000 series of workstations and servers, powered by SPARC processors, and running the UXP/DS operating system. In 1998, Fujitsu's new GP7000 series (GRANPOWER 7000) was divided into three parts. Series "S" represented their previous systems running UXP/DS. Series "D" represented their new systems also running UXP/DS. Series "F" represented their new systems running Solaris operating system. GP7000F running Solaris became the basis for later lines of Fujitsu Unix servers. In 1999, UXP/DS on the DS/90 7000 series was one of the reference platforms for the Common Desktop Environment (CDE). In 2000, when Fujitsu released its new PRIMEPOWER line of Unix servers, only Solaris was available as an option for the operating system. See also EWS-UX Sony NEWS Fujitsu VP2000 optional running UXP/M for Mainframes as Vector and Parallel Processors References External links IPSJ Computer Museum: FUJITSU DS/90 7000 Series Fujitsu software UNIX System V

Operating System (OS)

OSS through Java OSS/J (a.k.a. OSS through Java) is a TM Forum technical program whose primary goal is to develop open interface standards (APIs) for the integration of Business Support Systems (BSS) & Operations Support System (OSS). OSS/J addresses the concerns of Frameworx implementation stakeholders by providing open standard APIs based on the NGOSS framework, particularly the Frameworx Shared Information/Data Model (SID). Work is underway to organize the OSS/J APIs against the NGOSS Telecom Application Map (TAM). The OSS/J APIs are multi-technology based and include Java, XML, and Web Services integration profiles. Each integration profile consists of specifications, a reference implementation, and a conformance test suite (TCK). The OSS/J APIs are developed under the Java Community Process and can be downloaded for free from the TM Forum OSS/J web site. See also Networked Help Desk References External links OSS/J Program web site Computer standards

Operating System (OS)

Mac OS nanokernel The Mac OS nanokernel is an operating system kernel serving as the basis of most PowerPC based system software versions 7 through 9 of the classic Mac OS, predating Mac OS X. The initial revision of this software is a single tasking system which delegates most tasks to an emulator running the Motorola 68000 series (68K) version of the operating system. The second major revision supports multitasking, multiprocessing, and message passing, and would be more properly called a microkernel. Unlike the 68K-derived Mac OS kernel running within it, the PowerPC kernel exists in a protected memory space and executes device drivers in user mode. The nanokernel is very different from the Copland OS microkernel, although they were created in succession with similar goals. System 7.1.2 – Mac OS 8.5.1 The original nanokernel, and the tightly integrated Mac 68k emulator, were written by emulation consultant Gary Davidian. Its main purpose is to allow the existing Motorola 68K version of the operating system to run on new hardware. As such, the normal state of the system is to be running 68K code. The operating system does little until activated by an interrupt, which is quickly mapped to its 68K equivalent within the virtual machine. Other tasks may include switching back to PowerPC mode, if necessary, upon completion of the interrupt handler, and mapping the Macintosh virtual memory system to the PowerPC hardware. However, as the software is little documented, these might instead be handled by the emulator running in user mode. This nanokernel is stored on the Mac OS ROM chip integrated into Old World ROM computers, or inside the Mac OS ROM file on disk on the New World ROM computers, rather than being installed in the familiar sense. Interim development Progress after 1994 demanded additional functionality. A forward-looking architecture was introduced for PCI card drivers in anticipation of the Copland microkernel called NuKernel, which supports memory protection. The Open Transport networking architecture introduced standardized PowerPC synchronization primitives. The DayStar Digital Genesis MP Macintosh clone requires kernel extensions to support multiprocessing. This evolution would later affect the overhaul to the nanokernel in Mac OS 8.6. Mac OS 8.6 and later Mac OS 8.6's nanokernel was rewritten by René A. Vega to add Multiprocessing Services 2.0 support. PowerMacInfo, distributed in the Multiprocessing SDK, is an application that displays statistics about the nanokernel's operation. References External links René A. Vega's explanation of basic Mac OS architecture supervisor mode Question from a non-programmer Nanokernels Classic Mac OS

Operating System (OS)

Software system A software system is a system of intercommunicating components based on software forming part of a computer system (a combination of hardware and software). It "consists of a number of separate programs, configuration files, which are used to set up these programs, system documentation, which describes the structure of the system, and user documentation, which explains how to use the system". The term "software system" should be distinguished from the terms "computer program" and "software". The term computer program generally refers to a set of instructions (source, or object code) that perform a specific task. However, a software system generally refers to a more encompassing concept with many more components such as specification, test results, end-user documentation, maintenance records, etc. The use of the term software system is at times related to the application of systems theory approaches in the context of software engineering. A software system consists of several separate computer programs and associated configuration files, documentation, etc., that operate together. The concept is used in the study of large and complex software, because it focuses on the major components of software and their interactions. It is also related to the field of software architecture. Software systems are an active area of research for groups interested in software engineering in particular and systems engineering in general. Academic journals like the Journal of Systems and Software (published by Elsevier) are dedicated to the subject. The ACM Software System Award is an annual award that honors people or an organization "for developing a system that has had a lasting influence, reflected in contributions to concepts, in commercial acceptance, or both". It has been awarded by the Association for Computing Machinery (ACM) since 1983, with a cash prize sponsored by IBM. The two types of are system software and application software Categories Major categories of software systems include those based on application software development, programming software, and system software although the distinction can sometimes be difficult. Examples of software systems include operating systems, computer reservations systems, air traffic control systems, military command and control systems, telecommunication networks, content management systems, database management systems, expert systems, embedded systems etc. See also ACM Software System Award Common layers in an information system logical architecture Computer program Computer program installation Experimental software engineering Failure assessment Software bug Software architecture System software Systems theory Systems Science Systems Engineering Software Engineering References Systems engineering Software engineering terminology

Operating System (OS)

Boot disk A boot disk is a removable digital data storage medium from which a computer can load and run (boot) an operating system or utility program. The computer must have a built-in program which will load and execute a program from a boot disk meeting certain standards. While almost all modern computers can boot from a hard drive containing the operating system and other software, they would not normally be called boot disks (because they are not removable media). CD-ROMs are the most common forms of media used, but other media, such as magnetic or paper tape drives, ZIP drives, and more recently USB flash drives can be used. The computer's BIOS must support booting from the device in question. One can make one's own boot disk (typically done to prepare for when the system won't start properly). Uses Boot disks are used for: Operating system installation Data recovery Data purging Hardware or software troubleshooting BIOS flashing Customizing an operating environment Software demonstration Running a temporary operating environment, such as when using a Live USB drive. Administrative access in case of lost password is possible with an appropriate boot disk with some operating systems Games (e.g. for Amiga home computers, running MS-DOS video games on modern computers by using a bootable MS-DOS or FreeDOS USB flash drive). Process The term boot comes from the idea of lifting oneself by one's own bootstraps: the computer contains a tiny program (bootstrap loader) which will load and run a program found on a boot device. This program may itself be a small program designed to load a larger and more capable program, i.e., the full operating system. To enable booting without the requirement either for a mass storage device or to write to the boot medium, it is usual for the boot program to use some system RAM as a RAM disk for temporary file storage. As an example, any computer compatible with the IBM PC is able with built-in software to load the contents of the first 512 bytes of a floppy and to execute it if it is a viable program; boot floppies have a very simple loader program in these bytes. The process is vulnerable to abuse; data floppies could have a virus written to their first sector which silently infects the host computer if switched on with the disk in the drive. Media Bootable floppy disks ("boot floppies") for PCs usually contain DOS or miniature versions of Linux. The most commonly available floppy disk can hold only 1.4 MB of data in its standard format, making it impractical for loading large operating systems. The use of boot floppies is in decline, due to the availability of other higher-capacity options, such as CD-ROMs or USB flash drives. Device selection A modern PC is configured to attempt to boot from various devices in a certain order. If a computer is not booting from the device desired, such as the floppy drive, the user may have to enter the BIOS Setup function by pressing a special key when the computer is first turned on (such as , , , or ), and then changing the boot order. More recent BIOSes permit the interruption of the final stage of the boot process and invoke the Boot Menu by pressing a function key (usually or ). This results in a list of bootable devices being presented, from which a selection may be made. Apple silicon Macs display the Boot Menu when the power button is pressed and held, the older Apple Macintosh computers with Intel processors will display the Boot Menu if user presses the or while the machine is starting. Requirements Different operating systems use different boot disk contents. All boot disks must be compatible with the computer they are designed for. MS-DOS/PC DOS/DR-DOS A valid boot sector in form of a volume boot record (VBR) IO.SYS or IBMBIO.COM MSDOS.SYS or IBMDOS.COM COMMAND.COM All files must be for the same version of the operating system. Complete boot disks can be prepared in one operation by an installed operating system; details vary. FreeDOS A valid boot sector on the disk COMMAND.COM KERNEL.SYS Linux A bootloader such as SYSLINUX or GRUB Linux kernel Initial ram disk (initrd) Windows Preinstallation Environment Windows Boot Manager BOOT.WIM See also Darik's Boot and Nuke Data recovery El Torito (CD-ROM standard) Live CD Protected Area Run Time Interface Extension Services (PARTIES) Self-loader References External links reboot.pro - Community forum dedicated to Boot Disks Boot Disk information, sources, and tools Bootable media

Operating System (OS)

Linux Mint Linux Mint is a community-driven Linux distribution based on Ubuntu (in turn based on Debian), bundled with a variety of free and open-source applications. It can provide full out-of-the-box multimedia support for those who choose to include proprietary software such as multimedia codecs. The Linux Mint project was created by Clément Lefèbvre and is actively maintained by the Linux Mint Team and community. History Linux Mint began in 2006 with a beta release, 1.0, code-named 'Ada', based on Kubuntu. Linux Mint 2.0 'Barbara' was the first version to use Ubuntu as its codebase. It had few users until the release of Linux Mint 3.0, 'Cassandra'. Linux Mint 2.0 was based on Ubuntu 6.10, using Ubuntu's package repositories and using it as a codebase. It then followed its own codebase, building each release from the previous one, but continuing to use the package repositories of the latest Ubuntu release. This made the two systems' bases almost identical, guaranteeing full compatibility between them, rather than requiring Mint to be a fork. In 2008, Linux Mint adopted the same release cycle as Ubuntu and dropped its minor version number before releasing version 5 'Elyssa'. The same year, in an effort to increase compatibility between the two systems, Linux Mint decided to abandon its codebase and changed the way it built its releases. Starting with Linux Mint 6 'Felicia', each release was based completely on the latest Ubuntu release, built directly from it, and made available approximately one month after the corresponding Ubuntu release (usually in May or November). In 2010, Linux Mint released Linux Mint Debian Edition (LMDE). Unlike the other Ubuntu-based editions (Ubuntu Mint), LMDE was originally a rolling release based directly on Debian and not tied to Ubuntu packages or its release schedule. It was announced on May 27, 2015 that the Linux Mint team would no longer support the original rolling release version of LMDE after January 1, 2016. LMDE 2 'Betsy' was a long term support release based on Debian Jessie. When LMDE 2 was released it was announced that all LMDE users would be automatically upgraded to new versions of MintTools software and new desktop environments before they were released into the main edition of Linux Mint. On February 20, 2016, the Linux Mint website was breached by unknown hackers who briefly replaced download links for a version of Linux Mint with a modified version containing malware. The hackers also breached the database of the website's user forum. Linux Mint immediately took its server offline and implemented enhanced security configuration for their website and forum. Releases Every version of Linux Mint is given a version number and code-named with a feminine first name ending in 'a' and beginning with a letter of the alphabet that increased with every major revision. Version 18 broke from the pattern with the name 'Sarah', though in English it retains the same final vowel sound as all of the other releases. Initially, there were two Linux Mint releases per year. Following the release of Linux Mint 5 in 2008, every fourth release was labeled a long-term support (LTS) version, indicating that it was supported (with updates) for longer than traditional releases. Versions 5 and 9 had three years of support, and all LTS versions following received five years of support. On May 31, 2014, with the release of Linux Mint 17, the Linux Mint team adopted a new release strategy. Starting with the release of Mint 17, all future versions were planned to use a LTS version of Ubuntu as a base, until 2016. Under this strategy, Mint 17.1 was released on November 29, 2014, Mint 17.2 was released on June 30, 2015, and Mint 17.3 was released on December 4, 2015. The 17.x releases are intended to be an easy, optional upgrade. All three versions included upgrades to the Cinnamon and MATE Desktop Environments and various Mint tools. In addition, Mint 17.2 and 17.3 included an upgrade to the LibreOffice suite. The 18.x series follows the pattern set by the 17.x series, by using Ubuntu 16.04 LTS as a base. Linux Mint does not communicate specific release dates as new versions are published 'when ready', meaning that they can be released early when the distribution is ahead of schedule or late when critical bugs are found. New releases are announced, with much other material, on the Linux Mint blog. On January 3, 2018, the Linux Mint Team released news of Linux Mint 19 'Tara'. The team stated that the 19.x releases would use GTK 3.22 and be based on Ubuntu 18.04 LTS, with support provided until 2023. On June 29, 2018, Linux Mint 19 'Tara' Cinnamon was released. Then, on December 24, 2019, Linux Mint 19.3, 'Tricia' was released, with security updates available until 2023. On June 27, 2020, Linux Mint 20 'Ulyana' was released. It is an LTS version with support until 2025. On January 8, 2021 Linux Mint 20.1 'Ulyssa' was released. On July 8, 2021 Linux Mint 20.2 'Uma' was released. Up to 2014 there had been two Linux Mint releases per year, about one month after the Ubuntu releases they were based on. Each release was given a new version number and a code name, using a female first name starting with the letter whose alphabetical index corresponds to the version number and ending with the letter "a" (e.g., "Elyssa" for version 5, "Felicia" for version 6). There is also an OEM version for ease of installation for hardware manufacturers. Releases were timed to be approximately one month after Ubuntu releases (which in turn are about one month after GNOME releases and two months after X Window System releases). Consequently, every Linux Mint release came with an updated version of both GNOME and X and features some of the improvements brought in the latest Ubuntu release. Support for most releases was discontinued two months after the next release, but since the mid-2008 v5 every fourth release has been labelled a long-term support (LTS) version, indicating that it is supported (with updates) for longer, three years for v5 and v9, and five years thereafter. Linux Mint 17 "Qiana" LTS was released on 31 May 2014, remaining current until the end of November 2014 and supported until April 2019. In mid-2014 the successor to 17 Qiana was announced to be 17.1 Rebecca; the development team said that from a technical point of view Linux Mint was no longer tied to the Ubuntu schedule, so it could be released at any time, although the six-month cycle provided rhythm, leading to a late November 2014 target. Linux Mint 17 LTS would be the first release of the 17.x series, and for two years applications would be backported to 17.x, with security updates until 2019. The latest release is Linux Mint 20.3 "Una", released on January 7, 2022. As an LTS release, it will be supported until 2025. Linux Mint Debian Edition, not compatible with Ubuntu, is based on Debian and updates are brought in continuously between major versions (of LMDE). Linux Mint Debian Edition release history Gallery Features Linux Mint primarily uses free and open-source software. Up to and including version 17.3, the installation process included some proprietary software, such as plug-ins and codecs that provide Adobe Flash, MP3, and DVD playback, by default. The installer for version 18 no longer included any proprietary software. Since version 18.1, the installer has provided an option to include third-party and proprietary software (graphics and Wi-Fi drivers, Flash, MP3 and other codecs). Linux Mint comes with a wide range of software installed, including LibreOffice, Firefox, Thunderbird, HexChat, Pidgin, Transmission, and VLC media player. Additional software that is not installed by default can be downloaded using the package manager, adding a PPA, or adding a source to the sources file in the etc directory. Linux Mint allows networking ports to be closed using its firewall, with customized port selection available. The default Linux Mint desktop environments, Cinnamon and MATE, support many languages. Linux Mint can also run many programs designed for Microsoft Windows (such as Microsoft Office), using the Wine Windows compatibility layer software for Linux, or virtualization software, including VMware Workstation and VirtualBox, or KVM (Kernel-based Virtual Machine, built into the Linux kernel) hypervisor using Virtual Machine Manager. Linux Mint is available with a number of desktop environments to choose from, including the default Cinnamon desktop, MATE and Xfce. Other desktop environments can be installed via APT, Synaptic, or via the custom Mint Software Manager. Linux Mint implements Mandatory Access Control with AppArmor to enhance security by default, and restricts the default network-facing processes. Linux Mint actively develops software for its operating system. Most of the development is done in Python and the source code is available on GitHub. Software by Linux Mint Cinnamon The Cinnamon desktop environment is a fork of GNOME Shell based on the innovations made in Mint Gnome Shell Extensions (MGSE). It was released as an add-on for Linux Mint 12 and has been available as a default desktop environment since Linux Mint 13. MintTools Software Manager (mintInstall): Designed to install software from the Ubuntu and Linux Mint software repositories, as well as Launchpad PPAs. Since Linux Mint 18.3, the Software Manager has also been able to install software from Flatpak remotes, and is configured with Flathub by default. It features an interface heavily inspired by GNOME Software, and is built upon GTK3. Update Manager (mintUpdate): Designed to prevent inexperienced users from installing updates that are unnecessary or require a certain level of knowledge to configure properly. It assigns updates a safety level (from 1 to 5), based on the stability and necessity of the update. Updates can be set to notify users (as is normal), be listed but not notify, or be hidden by default. In addition to including updates specifically for the Linux Mint distribution, the development team tests all package-wide updates. In newer versions of the operating system, this safety level mechanism is largely deactivated in favour of system snapshots created by the Timeshift tool. Main Menu (mintMenu): Created for the MATE desktop environment. It is a menu of options including filtering, installation, and removal of software, system and places links, favourites, session management, editable items, custom places and many configuration options. Backup Tool (mintBackup): Enables the user to back up and restore data. Data can be backed up before a fresh install of a newer release then restored. Upload Manager (mintUpload): Defines upload services for FTP, SFTP and SCP servers. Services are then available in the system tray and provide zones where they may be automatically uploaded to their corresponding destinations. As of Linux Mint 18.3, this software is no longer installed by default but is still available in the Linux Mint software repositories. Domain Blocker (mintNanny): A basic domain blocking parental control tool introduced with v6. Enables the user to manually add domains to be blocked system-wide. As of Linux Mint 18.3, this software is no longer installed by default but is still available in the Linux Mint software repositories. Desktop Settings (mintDesktop): A tool for configuration of the desktop. Welcome Screen (mintWelcome): Introduced in Linux Mint 7, an application that starts on the first login of any new account. It provides links to the Linux Mint website, user guide, and community website. USB Image Writer/USB Stick Formatter (mintStick): A tool for writing an image onto a USB drive or formatting a USB stick. System Reports (mintReport): Introduced in Linux Mint 18.3, the purpose of System Reports is to allow the user to view and manage automatically generated application crash reports. Installation Linux Mint can be booted and run from a USB flash drive on any PC capable of booting from a USB drive, with the option of saving settings to the flash drive. A USB creator program is available to install on Ubuntu (but not LMDE) Live Linux Mint on a USB drive. Alternatively, the Linux Mint ISO can be burned to a DVD to boot from. The Windows installer Mint4Win allows Linux Mint to be installed from within Microsoft Windows, much like the Wubi installer for Ubuntu. The operating system could then be removed, as with other Windows software, using the Windows Control Panel. This method requires no partitioning of the hard drive. It is only useful for Windows users, and is not meant for permanent installations because it incurs a slight performance loss. This installer was included on the Live DVD until Linux Mint 16 but removed in the Linux Mint 16 'Petra' release because the size of the Live DVD images would have exceeded what the software could reliably handle. Installation supports a Logical Volume Manager (LVM) with automatic partitioning only, and disk encryption since Linux Mint 15. UTF-8, the default character encoding, supports a variety of non-Roman scripts. Editions Linux Mint has multiple editions that are based on Ubuntu, with various desktop environments available. Linux Mint also has an edition based on Debian. Ubuntu-based editions As of Linux Mint 13, there are two main editions of Linux Mint developed by the core development team and using Ubuntu as a base. One includes Linux Mint's own Cinnamon as the desktop environment while the other uses MATE. Linux Mint also develops an additional version that features the Xfce desktop environment by default; since the release of version 19 (Tara) in June 2018, the three editions are released simultaneously. Beginning with the release of Linux Mint 19, the KDE edition was officially discontinued; however, the KDE 17.x and 18.x releases will continue to be supported until 2019 and 2021, respectively. Older releases, now also obsolete, included editions that featured the GNOME, LXDE, and Fluxbox desktop environments by default. Cinnamon (Edge) Edition In addition to its regular ISO images, Linux Mint sometimes provides an “edge” ISO image for its latest release. This image ships with newer components to be able to support the most modern hardware chipsets and devices. OEM version The distribution provided an OEM version for manufacturers to use; however, this version was discontinued with the release of v18 Sarah in order to reduce the number of ISO images that needed to be maintained. Manufacturers wanting to perform an OEM install now have the option to choose so in the live CD boot menu. No Codecs version The distribution provided a 'No Codecs' version for magazines, companies, and distributors in the United States, Japan, and countries where the legislation allows patents to apply to software and distribution of restricted technologies may require the acquisition of third-party licences; however, this version was discontinued with release of v18 Sarah. Users now have the option of whether or not to install multimedia codecs during the installation; additionally, multimedia codecs can also be installed via a link on the Mint Welcome Screen any time after installation. LMDE The Linux Mint Debian Edition (LMDE) uses Debian Stable as the software source base rather than Ubuntu. LMDE was originally based directly on Debian's Testing branch, but is designed to provide the same functionality and look and feel as the Ubuntu-based editions. LMDE has its own package repositories. LMDE claims certain advantages and disadvantages compared to 'Mint Main' (i.e., the Ubuntu-based editions): LMDE is faster and more responsive than Ubuntu-based editions. LMDE requires a deeper knowledge and experience with Linux and Debian package management. Debian is less user-friendly and desktop-ready than Ubuntu, with some rough edges. LMDE 1 The original LMDE (now often referred to as LMDE 1) had a semi-rolling release development model, which periodically introduced 'Update Packs' (tested snapshots of Debian Testing). Installing an Update Pack allowed the user to keep LMDE 1 current, without having to reinstall the system every six months as with Mint Main. As of May 17, 2015, it has an upgrade path to LMDE 2. LMDE 2 LMDE 2 (a.k.a. Betsy) was released on April 10, 2015. LMDE 2 is based on Debian Stable, but receives automatic updates to the latest versions of MintTools and the installed desktop environment before they are released into the Mint Main edition. LMDE 2 is available with both the MATE and Cinnamon desktop environments. Both image versions received an update in January 2017. As of the start of 2019, this version is no longer supported. LMDE 2 remains based on sysvinit but with a 'functional logind' from systemd. LMDE 3 LMDE 3 (a.k.a. Cindy) is 'very likely' to complete the switch to systemd from sysvinit. It is based on Debian Stretch, and was released on August 31, 2018, shipping as a single edition with Cinnamon. As of July 1, 2020, this version is no longer supported. LMDE 4 LMDE 4 (a.k.a. Debbie) is based on Debian Buster (version 10), and was released on March 20, 2020. It is the current version of LMDE. This version ships as a single edition using Cinnamon. LMDE 5 LMDE 5 (a.k.a. Elsie) will be based on Debian Bullseye (version 11). It will ship with a Cinnamon desktop environment and support both amd64 and i386 architectures. Development Individual users and companies using the operating system act as donors, sponsors and partners of the distribution. Linux Mint relies on user feedback to make decisions and orient its development. The official blog often features discussions where users are asked to voice their opinion about the latest features or decisions implemented for upcoming releases. Ideas can be submitted, commented upon and rated by users via the Linux Mint Community Website. The community of Linux Mint users use Launchpad to participate in the translation of the operating system and in reporting bugs. Most development is done in Python and organized online using GitHub, making it easy for developers to provide patches, implement additional features, and also fork Linux Mint sub-projects (for example the Linux Mint menu was ported to Fedora). With each release, features are added that are developed by the community. In Linux Mint 9, for instance, the ability to edit menu items is a feature that was contributed by a Linux Mint user. Reception In May 2013, David Hayward of TechRadar praised Linux Mint for focusing on desktop users. In a 2012 online poll at Lifehacker, Linux Mint was voted the second best Linux distribution, after Ubuntu, with almost 16% of the votes. In October 2012 (Issue 162), Linux Format named Linux Mint the best distro for 2012. In July 2013 (Issue 128), Linux User & Developer gave Linux Mint 15 'Olivia' a score of 5/5, stating 'We haven't found a single problem with the distro ... we're more than satisfied with the smooth, user-friendly experience that Linux Mint 15, and Cinnamon 1.8, provides for it to be our main distro for at least another 6 months'. Reviews of Linux Mint 18 'Sarah' were somewhat mixed, with several that were quite favourable and others critical of several specific new problems, with multiple reviews complaining about the lack of multimedia/codec support by default. Multimedia codecs that had previously been included in the standard Mint distribution were no longer included in 'Sarah', but could be loaded with a graphical application that one Ars Technica reviewer said should be obvious for new users. ZDNet Contributing Editor Steven J. Vaughan-Nichols reviewing Linux Mint 19 and LM 19.1 in articles 'The Linux Mint desktop continues to lead the rest' in July 2018 and 'The better-than-ever Linux desktop' in December 2018 noted quality, stability, security and user-friendliness of Linux Mint comparing to other popular distributions. In ZDNet review of Linux Mint 19.2, it was noted '... after looking at many Linux desktops year in and out, Linux Mint is the best of the breed. It's easy to learn (even if you've never used Linux before), powerful, and with its traditional windows, icons, menus, and pointers (WIMP) interface, it's simple to use'. Minimum hardware requirements For Linux Mint 20.2, either Cinnamon, MATE, or XFCE edition: 2 GB RAM (4 GB recommended) 20 GB of hard-drive space (100 GB recommended) Screen of 1024×768 resolution Either a CD/DVD drive or a USB port for the installation media Internet access is helpful Versions prior to Linux Mint 20 allowed booting from either i386 (32 bit) or amd64 (64 bit) architectures. Starting with Linux Mint 20 only the amd64 (64 bit) architecture will be supported. This is because Canonical decided to drop 32-bit support from Ubuntu 20.04, which is the base from which Linux Mint 20 is derived. LMDE still supports the x86 architecture. See also List of Ubuntu-based Linux distributions References Further reading External links Differences in Linux Mint desktop choices - Cinnamon, MATE, Xfce, or KDE Computer-related introductions in 2006 2006 software Ubuntu derivatives X86-64 Linux distributions Free software operating systems Linux distributions

Operating System (OS)

Open (system call) For most file systems, a program initializes access to a file in a file system using the open system call. This allocates resources associated to the file (the file descriptor), and returns a handle that the process will use to refer to that file. In some cases the open is performed by the first access. The same file may be opened simultaneously by several processes, and even by the same process, resulting in several file descriptors for the same file; depending on the file organization and filesystem. Operations on the descriptors such as moving the file pointer or closing it are independentthey do not affect other descriptors for the same file. Operations on the file, such as a write, can be seen by operations on the other descriptors: a later read can read the newly written data. During the open, the filesystem may allocate memory for buffers, or it may wait until the first operation. The absolute file path is resolved. This may include connecting to a remote host and notifying an operator that a removable medium is required. It may include the initialization of a communication device. At this point an error may be returned if the host or medium is not available. The first access to at least the directory within the filesystem is performed. An error will usually be returned if the higher level components of the path (directories) cannot be located or accessed. An error will be returned if the file is expected to exist and it does not or if the file should not already exist and it does. If the file is expected to exist and it does, the file access, as restricted by permission flags within the file meta data or access control list, is validated against the requested type of operations. This usually requires an additional filesystem access although in some filesystems meta-flags may be part of the directory structure. If the file is being created, the filesystem may allocate the default initial amount of storage or a specified amount depending on the file system capabilities. If this fails an error will be returned. Updating the directory with the new entry may be performed or it may be delayed until the close is performed. Various other errors which may occur during the open include directory update failures, un-permitted multiple connections, media failures, communication link failures and device failures. The return value must always be examined and an error specific action taken. In many cases programming language-specific run-time library opens may perform additional actions including initializing a run-time library structure related to the file. As soon as a file is no longer needed, the program should close it. This will cause run-time library and filesystem buffers to be updated to the physical media and permit other processes to access the data if exclusive use had been required. Some run-time libraries may close a file if the program calls the run-time exit. Some filesystems may perform the necessary operations if the program terminates. Neither of these is likely to take place in the event of a kernel or power failure. This can cause damaged filesystem structures requiring the running of privileged and lengthy filesystem utilities during which the entire filesystem may be inaccessible. open call arguments The pathname to the file, The kind of access requested on the file (read, write, append etc.), The initial file permission is requested using the third argument called mode. This argument is relevant only when a new file is being created. After using the file, the process should close the file using close call, which takes the file descriptor of the file to be closed. Some filesystems include a disposition to permit releasing the file. Some computer languages include run-time libraries which include additional functionality for particular filesystems. The open (or some auxiliary routine) may include specifications for key size, record size, connection speed. Some open routines include specification of the program code to be executed in the event of an error. Perl language form open FILEHANDLE,MODE[,EXPR] for example: open(my $fh, ">", "output.txt"); Perl also uses the tie function of the Tie::File module to associate an array with a file. The tie::AnyDBM_File function associates a hash with a file. C library POSIX definition The open call is standardized by the POSIX specification for C language: int open(const char *path, int oflag, .../*,mode_t mode */); int openat(int fd, const char *path, int oflag, ...); int creat(const char *path, mode_t mode); FILE *fopen(const char *restrict filename, const char *restrict mode); The value returned is a file descriptor which is a reference to a process specific structure which contains, among other things, a position pointer that indicates which place in the file will be acted upon by the next operation. Open may return −1 indicating a failure with errno detailing the error. The file system also updates a global table of all open files which is used for determining if a file is currently in use by any process. path The name of the file to open. It includes the file path defining where, in which file system, the file is found (or should be created). openat expects a relative path. oflag This argument formed by OR'ing together optional parameters and (from <fcntl.h>) one of: O_RDONLY, O_RDWR and O_WRONLY Option parameters include: O_APPEND data written will be appended to the end of the file. The file operations will always adjust the position pointer to the end of the file. O_CREAT Create the file if it does not exist; otherwise the open fails setting errno to ENOENT. O_EXCL Used with O_CREAT if the file already exists, then fail, setting errno to EEXIST. O_TRUNC If the file already exists then discard its previous contents, reducing it to an empty file. Not applicable for a device or named pipe. Additional flags and errors are defined in open call. creat() is implemented as: int creat(const char *path, mode_t mode) { return open(path, O_WRONLY|O_CREAT|O_TRUNC, mode); } fopen uses string flags such as r, w, a and + and returns a file pointer used with fgets, fputs and fclose. mode Optional and relevant only when creating a new file, defines the file permissions. These include read, write or execute the file by the owner, group or all users. The mode is masked by the calling process's umask: bits set in the umask are cleared in the mode. See also File descriptor – how it works and other functions related to open Notes References Advanced Programming in the UNIX Environment by W. Richard Stevens UNIX concept & application by Sumitabh Das C POSIX library System calls Articles with example C code

Operating System (OS)

Joli OS Joli OS was an Ubuntu-based Linux distribution created by Tariq Krim and Romain Huet co-founders of the French company Jolicloud (also the name of the operating system until version 1.2). Joli OS is now an open source project, with source code hosted on GitHub. On 22 November 2013, Tariq Krim decided to discontinue Joli OS, but keep the source code open. Jolicloud was discontinued on April 1, 2016. History The project was launched in 2008 by Netvibes founder Tariq Krim and Romain Huet. Krim originally wanted to build a laptop using environmentally friendly manufacturing methods, but the two co-founders refocused the effort on building an operating system. After purchasing a few netbooks and renewing their acquaintance with Linux, they rented office space in the Montorgueil area of Paris and were later joined by another developer, Tristan Groléat. Venture capital firms Atomico Ventures and Mangrove Capital Partners have provided $4.2 million in funding. Version 1.0 was released in July 2010 and version 1.1 was released on 7 December 2010. Version 1.2 was released on 9 March 2011. Design, hardware compatibility Joli OS was at the beginning built on top of Ubuntu Netbook Edition, and as with that Linux distribution, was tweaked for netbooks and other computers with limited disk storage, memory, and screen size. Joli OS is now built on top of Ubuntu with a customized kernel. Joli OS was designed for easy installation, with Wi-Fi, bluetooth, and 3G modem support all included. The operating system supports all the major netbooks, including models from Asus, Acer, Dell, HP, MSI, Samsung and Sony. Jolicloud claims the OS supports 98% of netbooks with out-of-the-box compatibility but also works on a very large number of other devices, up to 10 years old: laptops, desktops and tablets. Version 1.0 of the operating system incorporates a user interface built primarily with HTML5 that includes an application launcher, a library of compatible applications with one-click installation and removal, a display of all machines associated with a user account, and a social activity stream that enables users to compare installed applications. The launcher displays only those applications supported in the library, but the identical configuration can be viewed from any machine running Joli OS. Account management is available from any computer with an HTML5-compatible browser. Jolicloud's HTML5 implementation is through the Chromium web browser, which serves as middleware for Web rendering. Version 1.0 reviews, response Reviewers evaluating Joli OS differed in their appraisals, depending on whether they were writing for a user who is new to Linux or is more experienced with the operating system. Writing on a Condé Nast Traveler blog, Mike Haney called Joli OS "an easy, free OS that you don't have to be a code-monkey to install and does everything you need your netbook to do, quickly. I put it on a Lenovo netbook this weekend that was running like molasses under Windows 7, and I'm a convert". While Joli OS is not the first operating system designed from Linux targeted at the beginning netbooks, "it's the first that doesn't feel like you're using Linux: no funky install procedures, no code, no accessing special directories to find more apps." He compared Joli OS in look and function to iOS, the operating system used by the Apple iPad (as well as the iPhone and iPod Touch), though with the folders and files of a conventional computer". In Computerworld, Serdar Yegulalp wrote that Joli OS 1.0 "feels like a second beta, not a 1.0 release; it needs more work before it's truly useful instead of one step above a curiosity". Yegulalp reported problems launching some applications, including the Google Chrome browser and the VLC media player, an inability to do peer-to-peer mesh networking, the power button getting blocked by open windows, and no hibernation mode, even if the computer supports it. He noted comparable performance with Windows 7 but slightly faster boot times. But ZDNet reporter David Meyer disagreed with that performance assessment after running Jolicloud on a Nokia Booklet 3G in order to take advantage of that device's unusual 720p screen resolution. He wrote that the device's "lousy Atom Z530 processor...really struggles under Windows 7 Starter Edition [but] flies on Jolicloud....I'm struggling to think of a rival Linux distro that can be so easily picked up and run by an average user". In Ars Technica, Ryan Paul wrote that "there are a lot of good ideas on display in Jolicloud [now Joli OS] 1.0, but the nascent product still feels incomplete". He saw no reason for Linux users, particularly Ubuntu users, to switch. "Ubuntu's own Unity environment is more sophisticated and has much better integration between native applications and the underlying platform," though Joli OS might be a better choice for users interested in Web applications. Noting that Joli OS 1.0's foundation is Ubuntu 9.04, which is nearing the end of its support cycle by Canonical, Paul wrote that "the real challenge will be continuing to expand the scope of Joli OS's differentiating features while...ensuring that Jolicloud users will benefit from Ubuntu's steady stream of new features". Tariq Krim defended the decision to stay with Ubuntu 9.04 in Joli OS 1.0, arguing that later Ubuntu versions have been less stable and have required user-initiated software installations to be fully functional. Examples where Jolicloud developers did additional work to ensure out-of-the-box functionality include support for Poulsbo GMA500 drivers, touchscreens and 3G. He said the company was "moving away from Ubuntu to a solution that could fit our user needs better. We are looking closely at what Chrome OS is doing". Jolibook In November 2010, Jolicloud shipped a netbook computer, called Jolibook, that ran the operating system out of the box. The computer was manufactured by UK-based Vye Computers and featured a 10.1-inch screen, dual core 1.5 GHz Intel Atom N550, 1GB RAM and a 250GB hard drive. Artwork on the lid included the slogan "fast, fun, connected". The machine was only available in the United Kingdom, selling for £280 via Shop.VyePC.com and Amazon.co.uk, and is no longer manufactured. Version 1.1 Jolicloud released version 1.1 in December 2010. The new version was based on Ubuntu 10.04 LTS (Lucid), with future patches planned from 10.10 (Maverick). Among the improvements claimed by the company were faster boot times of 10–20 seconds on most devices tested, 15 percent battery life improvements (tested on a Clevo M1100 netbook with an Intel Atom N450 processor and a three-cell battery) and support for all PCs, not just netbooks. Version 1.2 Version 1.2 was announced in March 2011 and renamed Joli OS. The new version featured a new boot screen, auto and guest mode log-ins, a local file system integrated within the desktop, remote access to the desktop from any HTML5-capable browser, optional background updates, and support for the latest Chromium 10 browser and Flash 10.2. Version 1.2 also includes Dropbox integration, an app creation wizard, and a file browser to access local files, preview Dropbox files and edit using Google Docs. It uses 2.2 GB of disk space when installed. See also SUSE_Studio#Notable appliances List of Linux distributions#openSUSE-based Cloud Comparison of netbook-oriented Linux distributions EasyPeasy Google Chrome OS MeeGo References External links Chrome Web Store Help Center Das deutsche Jolicloud Forum Joli on the Mini Tariq Krim in Interview with 99FACES.tv Ubuntu derivatives Linux distributions used in appliances Cloud clients Computer-related introductions in 2008 Linux distributions

Operating System (OS)

TENEX (operating system) TENEX was an operating system developed in 1969 by BBN for the PDP-10, which later formed the basis for Digital Equipment Corporation's TOPS-20 operating system. Background In the 1960s, BBN was involved in a number of LISP-based artificial intelligence projects for DARPA, many of which had very large (for the era) memory requirements. One solution to this problem was to add paging software to the LISP language, allowing it to write out unused portions of memory to disk for later recall if needed. One such system had been developed for the PDP-1 at MIT by Daniel Murphy before he joined BBN. Early DEC machines were based on an 18-bit word, allowing addresses to encode for a 256 kiloword memory. The machines were based on expensive core memory and included nowhere near the required amount. The pager used the most significant bits of the address to index a table of blocks on a magnetic drum that acted as the pager's backing store. The software would fetch the pages if needed, and then resolve the address to the proper area of RAM. In 1964 DEC announced the PDP-6. DEC was still heavily involved with MIT's AI Lab, and many feature requests from the LISP hackers were moved into this machine. 36-bit computing was especially useful for LISP programming because with an 18-bit address space, a word of storage on these systems contained two addresses, a perfect match for the common LISP CAR and CDR operations. BBN became interested in buying one for their AI work when they became available, but wanted DEC to add a hardware version of Murphy's pager directly into the system. With such an addition, every program on the system would have paging support invisibly, making it much easier to do any sort of programming on the machine. DEC was initially interested, but soon (1966) announced they were in fact dropping the PDP-6 and concentrating solely on their smaller 18-bit and new 16-bit lines. The PDP-6 was expensive and complex, and had not sold well for these reasons. It was not long until it became clear that DEC was once again entering the 36-bit business with what would become the PDP-10. BBN started talks with DEC to get a paging subsystem in the new machine, then known by its CPU name, the KA-10. DEC was not terribly interested. However, one development of these talks was support for a second virtual memory segment, allowing half of the user address space to be mapped to a separate (potentially read-only) region of physical memory. Additionally, DEC was firm on keeping the cost of the machine as low as possible, such as supporting bare-bones systems with a minimum of 16K words of core, and omitting the fast semiconductor register option (substituting core), at the cost of a considerable performance decrease. BBN and PDP-10s BBN nevertheless went ahead with its purchase of several PDP-10s, and decided to build their own hardware pager. During this period a debate began on what operating system to run on the new machines. Strong arguments were made for the continued use of TOPS-10, in order to keep their existing software running with minimum effort. This would require a re-write of TOPS to support the paging system, and this seemed like a major problem. At the same time, TOPS did not support a number of features the developers wanted. In the end they decided to make a new system, but include an emulation library that would allow it to run existing TOPS-10 software with minor effort. The developer team—amongst them Daniel Murphy and Daniel G. Bobrow—chose the name TENEX (TEN-EXtended) for the new system. It included a full virtual memory system—that is, not only could programs access a full 18 bit address space of 262144 words of virtual memory, every program could do so at the same time. The pager system would handle mapping as it would always, copying data to and from the backing store as needed. The only change needed was for the pager to be able to hold several sets of mappings between RAM and store, one for each program using the system. The pager also held access time information in order to tune performance. The resulting pager was fairly complex, filling a full-height 19" rackmount chassis. One notable feature of TENEX was its user-oriented command line interpreter. Unlike typical systems of the era, TENEX deliberately used long command names and even included non-significant noise words to further expand the commands for clarity. For instance, Unix uses ls to print a list of files in a directory, whereas TENEX used DIRECTORY (OF FILES). "DIRECTORY" was the command word, "(OF FILES)" was noise added to make the purpose of the command clearer. To relieve users of the need to type these long commands, TENEX used a command completion system that understood unambiguously abbreviated command words, and expanded partial command words into complete words or phrases. For instance, the user could type DIR and the escape key, at which point TENEX would replace DIR with the full command. The completion feature also worked with file names, which took some effort on the part of the interpreter, and the system allowed for long file names with human-readable descriptions. TENEX also included a command recognition help system: typing a question mark (?), printed out a list of possible matching commands and then return the user to the command line with the question mark removed. The command line completion and help live on in current CLIs like tcsh. From TENEX to TOPS-20 TENEX became fairly popular in the small PDP-10 market, and the external pager hardware developed into a small business of its own. In early 1970 DEC started work on an upgrade to the PDP-10 processor, the KI-10. BBN once again attempted to get DEC to support a complex pager with indirect page tables, but instead DEC decided on a much simpler single-level page mapping system. This compromise impacted system sales; by this point TENEX was the most popular customer-written PDP-10 operating systems, but it would not run on the new, faster KI-10s. To correct this problem, the DEC PDP-10 sales manager purchased the rights to TENEX from BBN and set up a project to port it to the new machine. At around this time Murphy moved from BBN to DEC as well, helping on the porting project. Most of the work centered on emulating the BBN pager hardware in a combination of software and the KI-10's simpler hardware. The speed of the KI-10 compared to the PDP-6 made this possible. Additionally the porting effort required a number of new device drivers to support the newer backing store devices being used. Just as the new TENEX was shipping, DEC started work on the KL-10, intended to be a low-cost version of the KI-10. While this was going on, Stanford University AI programmers, many of them MIT alumni, were working on their own project to build a PDP-10 that was ten times faster than the original KA-10. The project evolved into the Foonly line of computers. DEC visited them and many of their ideas were then folded into the KL-10 project. The same year IBM also announced their own machine with virtual memory, making it a standard requirement for any computer. In the end the KL integrated a number of major changes to the system, but did not end up being any lower in cost. From the start, the new DECSYSTEM-20 would run a version of TENEX as its default operating system. Functional upgrades for the KL-10 processor architecture were limited. The most significant new feature (called extended addressing) was modified pager microcode running on a Model B hardware revision to enlarge the user virtual address space. Some effective address calculations by instructions located beyond the original 18-bit address space were performed to 30 significant bits, although only a 23-bit virtual address space was supported. Program code located in the original 18-bit address space had unchanged semantics, for backward compatibility. The first in-house code name for the operating system was VIROS (VIRtual memory Operating System); when customers started asking questions, the name was changed to SNARK so that DEC could truthfully deny that there was any project called VIROS. When the name SNARK became known, the name was briefly reversed to become KRANS; this was quickly abandoned when someone objected that "krans" meant "funeral wreath" in Swedish (though it simply means "wreath"; this part of the story may be apocryphal). Ultimately DEC picked TOPS-20 as the name of the operating system, and it was as TOPS-20 that it was marketed. The hacker community, mindful of its origins, quickly dubbed it TWENEX (a portmanteau of "twenty TENEX"), even though by this point very little of the original TENEX code remained (analogously to the differences between AT&T V7 Unix and BSD). DEC people cringed when they heard "TWENEX", but the term caught on nevertheless (the written abbreviation "20x" was also used). TWENEX was successful and very popular; in fact, there was a period in the early 1980s when it commanded as fervent a culture of partisans as Unix or ITS—but DEC's decision to scrap all the internal rivals to the VAX architecture and its VMS operating system killed the DEC-20 and put an end to TWENEX's brief period of popularity. DEC attempted to convince TOPS-20 users to convert to VMS, but instead, by the late 1980s, most of the TOPS-20 users had migrated to Unix. A loyal group of TOPS-20 enthusiasts kept working on various projects to preserve and extend TOPS-20, notably Mark Crispin and the Panda TOPS-20 distribution. See also Time-sharing system evolution References Some text in this article was taken from The Jargon File entry on "TWENEX", which is in the public domain. Further reading Daniel G. Bobrow, Jerry D. Burchfiel, Daniel L. Murphy, Raymond S. Tomlinson, "TENEX, A Paged Time Sharing System for the PDP-10", Communications of the ACM, Vol. 15, pages 135–143, March 1972. Discontinued operating systems Time-sharing operating systems 1969 software

Operating System (OS)

Paldo (operating system) paldo ("pure adaptable linux distribution") is a computer operating system built on top of the Linux kernel and using the GNU utilities. It was originally developed by Jürg Billeter and Raffaele Sandrini and released in 2004, mainly under the GNU GPL. Overview paldo was developed primarily for desktop computers using the IA-32 (i686) and x86-64 architectures to utilize applications that remain as close to their upstream source as possible. It has a history of frequent stable releases starting in 2004 (generally every 3 months) and a "rolling release" style of continual updating of the system and application packages. paldo has typically been offered in stable and unstable versions and is one of the relatively few independent distributions listed on DistroWatch. A stated intent of the paldo project is to only use selected programs in the distribution that satisfy a "just works" principle, with limited intervention needed by the user to compile or update, and minimal duplication of applications designed to accomplish the same task. Another principle is to minimize patching of paldo application packages, preserving adaptability for the end user to make changes or customize the system. Minimal customization of applications may also allow any required patches to be more easily available to the maintainers of the original packages. A customized installer application was developed, however, to simplify installation of live CD releases to the user's computer. In 2009, the version 7 release of the Swedish-based ExTiX Linux distribution was based on paldo version 1.18(stable), using Linux kernel 2.6.30 and Gnome desktop environment 2.26.1. In 2016, Jesse Smith reviewed paldo GNU/Linux 2015 in DistroWatch Weekly: Featured Applications paldo has primarily used the GNOME desktop in release snapshots available on the Live/Install CD. The default web browser is Epiphany, the default browser for the GNOME desktop environment, although other browsers are available or can be built using the native Upkg package manager. Typical applications found on the paldo Live/Install CD and in the repository have included: Epiphany Tomboy OpenOffice.org Totem Pidgin Gedit Subsequent to the 1.22 stable release, paldo adopted a rolling release format and by April 2011 paldo stable included GNOME 3.0, the Linux 2.6.38.3 kernel, and had already moved to systemd, a few weeks earlier than Fedora. Package management system paldo uses the Upkg package manager to update/upgrade the system and to install applications. Upkg was uniquely developed for the paldo project and is responsible for the distribution's character as a mixed source and binary based operating system. Written in C#, Upkg uses the Mono runtime to build packages from source, or to install pre-built binaries, using XML specifications that can be customized by the user. It relies on the command-line interface rather than a graphics-based user interface implementation commonly found in many desktop-oriented Linux distributions. Upkg provides dependency resolution, package indexing and automatic menu additions, although its processing time to upgrade the system and install packages, even those available through the online paldo repository, has been found to be relatively long. References External links Linux distributions 2004 software

Operating System (OS)

Porteus (operating system) Porteus (formerly Slax Remix) is a portable operating system based on Slackware. It does not require installation and can be run from fixed and removable media, such as a USB flash drive or compact disc. Porteus is available in 32-bit and 64-bit version. Development The Porteus project started out as "Slax Remix" at the beginning of 2010 and was started as a community project using the Zen kernel to improve and update the Slax OS. The community agreed on the new name of the project, Porteus, which was named after "'Portability' and 'Proteus'. 'Proteus' is a "Greek god of the sea, capable of changing his form at will," according to the naming announcement on the Porteus forum. The project leader commented on the name, "I find this name as a kind of synonym of 'flexibility.' We have portable (small) and flexible (modular) features included in one name: Porteus." Porteus 4.0 is available in seven desktop variants: Cinnamon, KDE Plasma 5, LXDE, LXQt, MATE, Openbox and Xfce. Features Porteus is based on a substantially modified and optimized version of the Linux Live Scripts. It can be run from a disk or USB stick (with changes saved onto the portable device) or installed on a hard drive. Porteus can even be installed within another system without the need to create a new partition. Porteus is preloaded with a variety of software that the user selects before installing. The system is downloaded only after selecting various options from a menu including one of four windows management systems, a browser and other features. Porteus uses a package manager utilizing slackware. Porteus Kiosk Porteus Kiosk is a specialized edition of the Porteus operating system, a minimalist Linux distribution for web-only terminals with Firefox (or Google Chrome, Chromium or Opera, set upon installation) as the sole application. Porteus Kiosk provides users with a locked down computing environment, designed to be deployed in schools, offices, public libraries, internet cafés or any other business establishment that provides Internet access to their clients. Porteus Kiosk can be installed to CD/DVD, USB flash drive, hard drive, or any other bootable storage media such as Compact Flash or SD/MMC memory cards. Prior to installation the system can be customized through the kiosk wizard utility which allows system and browser related tweaks. The Porteus Kiosk system is open source and available free-of-charge, although a number of commercial services such as custom builds, automatic updates and software upgrades are available. Until version 3.7.0 Porteus Kiosk was able to run on both 32-bit (i486 or greater) and 64-bit (x86_64) machines. As Google Chrome doesn't support 32-bit machines anymore, the developers of the distribution decided to follow that path. Hence with release 4.0.0 Porteus Kiosk supports only the x86_64 architecture. The system is lightweight in terms of size and resources used. The default image is about 80 MB while the size of the custom kiosk ISO will depend on the choice of added extra components such as Adobe Flash, Java, additional fonts and other factors. Reception In reviewing Porteus 1.0 in June 2011, Joe "Zonker" Brockmeier wrote, "Users who've missed KDE 3.5.x are in for a treat with Porteus, a portable Linux distribution that offers a 32-bit release with the Trinity fork of KDE 3.5.x, and a 64-bit release that offers KDE 4.6.4. While not a distribution that will appeal to everyone, it might be of interest to enthusiasts of live CD distributions and old-school KDE fans." He concluded "...Porteus looks like a nice portable Linux distribution, aimed at expert or at least experienced Linux users. It's not something that will appeal to the majority of Linux users, particularly users who prefer a slightly larger depth of available packages. But, for users who are nursing older hardware or prefer a portable distribution, Porteus is an interesting project." About the custom Live CD ISO creation, Linux magazine wrote in Issue 160/2014: "Build Your Own Portable Linux Distro with Porteus Building a customized Linux distribution can be a daunting proposition – unless you use Porteus Wizard. This clever and simple service lets you create a custom Live CD distro that fits a USB stick and loads in RAM." See also Lightweight Linux distribution List of Linux distributions that run from RAM List of live CDs Kiosk software References External links Reviews: DistroWatch Weekly, Issue 519, 5 August 2013 DistroWatch Weekly, Issue 575, 8 September 2014 A Not For The Everyday Linux User Review Of Porteus 3.1, Everyday Linux User With Porteus in Your Pocket, You're Good to Go | Reviews | LinuxInsider Best Linux Distro: Linux for old laptops, privacy and USB sticks | Trusted Reviews Review: Porteus 1.0 | Tux Machines Slackware-Based Porteus Linux 4.0 Officially Released with Seven Desktop Flavors, Softpedia News Best lightweight Linux distro of 2018 | TechRadar Das U-Blog by Prashanth: Review: Porteus 1.0 Light-weight Linux distributions Linux distributions Linux distributions without systemd Live USB Slackware

Operating System (OS)

NCOS NCOS is the graphical user interface-based operating system developed for use in Oracle Corporation's Network Computers, which are discontinued. It was adapted by Acorn Computers from its own , which was originally developed for their range of Archimedes desktop computers. It shares with the same 4 MB ROM size and suitability for use with TV displays. In 1999, Pace acquired the set-top box (STB) division of Acorn Computers, this being a component in the disposal of assets around the takeover of Acorn by MSDW Investment Holdings. This gave Pace the rights to use and develop NCOS. RISCOS Ltd later announced Embedded RISC OS, which was to have similarities with NCOS. Development NCOS originated in connection with the Network Computer project. It was used on various STB products. It branched from RISC OS 3.60 and was called RISC OS 3.61 before being named after Network Computer Operating System. It was merged back into the HEAD whilst at Pace, where it was known as and RO-STB. Features NCOS was designed in accord with the Network Computer Reference Profile and thus supports internet standards of the time. Being closely based on , it can also run many of that operating system's applications. See also Network operating system RISC OS character set References Acorn operating systems ARM operating systems

Operating System (OS)

Shepardson Microsystems Shepardson Microsystems, Inc. (SMI) was a small company producing operating systems and programming languages for CP/M, the Atari 8-bit family and Apple II computers. SMI is most noted for the original Apple II disk operating system, Atari BASIC, and Atari's disk operating system. Shepardson Microsystems was founded by Robert Shepardson in Saratoga Springs, New York. CP/M The company got its start in the microcomputer arena by producing a series of BASIC programming language interpreters for the burgeoning S-100 bus computer market. Their first product was Cromemco 16k BASIC, which, as the name implies, was intended to run on Cromemco Z-series Z80-based computers with 16 kB of RAM. As machines shipped with ever-increasing amounts of RAM, due largely to the replacement of SRAM with the much denser DRAM in the mid-1970s, SMI further expanded their version as the 26 kB Cromemco Structured BASIC, while a cut-down 12 kB version was released as CP/A Business BASIC. At the time they were written, Microsoft BASIC was widespread but not as universal as it would be by the early 1980s. SMI's BASICs were based on the concepts and syntax of Data General Business Basic (which was very similar to HP Time-Shared BASIC), as opposed to Digital's BASIC-PLUS that formed the basis for MS BASIC. As a result, SMI's BASICs incorporated a different way to handle strings and input/output, a difference that would be seen in their later languages for the Atari. Apple Computer On April 10, 1978, Shepardson Microsystems signed a contract with Apple. For $13,000 -- $5,200 up front, and $7,800 on delivery, and no additional royalties—Shepardson Microsystems would build Apple's first DOS—and hand it over just 35 days later. For its money, Apple would get a file manager, an interface for Integer BASIC and Applesoft BASIC, and utilities that would allow disk backup, disk recovery, and file copying. Apple provided detailed specifications, and early Apple employee Randy Wigginton worked closely with Shepardson's Paul Laughton as the latter wrote the operating system with punched cards and a minicomputer. That deal enabled release and sales of Apple's Disk II drive. Atari, Inc. Atari, Inc. planned to follow up its successful Atari VCS console with a more powerful home computer (the Atari 400 and 800), to be introduced at the January 1979 Consumer Electronics Show. This required a BASIC interpreter. A version of Microsoft BASIC for the MOS 6502 had been licensed for this purpose, but the task of retrofitting the code into an 8k cartridge proved too difficult. Atari turned to Shepardson Microsystems to help with the port, but after struggling with it themselves, they proposed developing a new BASIC instead of using Microsoft BASIC. Atari contracted with SMI not only for Atari BASIC, but the Atari Disk Operating System as well. SMI had their BASIC finished before the December 28, 1978 delivery of the contract, which included a $1000 bonus for early completion. In early 1981, SMI concluded that their BASIC and DOS products were not viable and permitted them, along with the Atari Assembler Editor, to be purchased by Bill Wilkinson and Mike Peters, who formed Optimized Systems Software. The new company enhanced the programs and sold them as third-party applications. References Wilkinson, Bill (1983). The Atari BASIC Source Book. Compute! Books. . Further reading Terdiman, Daniel, "Public at last: Apple II DOS code that launched an empire", CNET, November 12, 2013 External links Apple Computer The Early Days A Personal Perspective manuals The untold story behind Apple's $13,000 operating system Defunct software companies of the United States Apple II family Atari 8-bit family

Operating System (OS)

System configuration A system configuration (SC) in systems engineering defines the computers, processes, and devices that compose the system and its boundary. More generally, the system configuration is the specific definition of the elements that define and/or prescribe what a system is composed of. Alternatively, the term "system configuration" can be used to relate to a model (declarative) for abstract generalized systems. In this sense, the usage of the configuration information is not tailored to any specific usage, but stands alone as a data set. A properly-configured system avoids resource-conflict problems, and makes it easier to upgrade a system with new equipment..... Sample configuration The following is a basic SC XML System Configuration: Description: This provides information about a single "site" (MyHouse) and specifies that there is one host with user-setup and mysql-db components. The host must have an account on it for a user named mysql, with appropriate parameters. Notice that the configuration schema requires no XML tags that are Windows- or UNIX-specific. It simply presents data as standalone information – with no pretense for how the data is to be used. This is the hallmark for a good system configuration model. Further extensions The above model can be extended. For example, the user could have more attributes like "preferences" and "password". The components could depend on other components. Properties can be defined that are passed into sub-elements. The extensions can be endless (WATCHOUT: complexity) and must be managed and well-thought-out to prevent "breaking" the idea of the system configuration. Usage The usage for the model in practical terms falls into several categories: documentation, deployment & operations. Documentation One use of the configuration is to simply record what a system is. This documentation could in turn become quite extensive, thus complicating the data model. It is important to distinguish between configuration data and descriptive data. Of course comments can be applied at any level, even in most tools, however the bloating of the data can reduce its usefulness. For example, the system configuration is not a place to record historical changes, or descriptions of design and intent for the various elements. The configuration data is simply to be "what it is" or "what we want it to be". Deployment Deployment involves interpreting a configuration data set and acting on that data to realize the configure the system accordingly. This may simply be a validation of what's there to confirm that the configuration is in effect. Examples include a Perl library launched from the command line to read the configuration and begin launching processes on the local or remote hosts to install components. Also while the system is running, there may be a SystemConfiguration service that provides an interface (i.e. CORBA IDL interfaces) for other system applications to use to access the configuration data, and perform deployment-like actions. Operations When the system is in operation, there may be uses for the configuration data by specific kinds of services in the system. For example, a Secnager may access the configuration to acquire the MD5 passwords for the user accounts that are allowed to log into hosts remotely. A system monitor service (see: system monitoring) may use the data to determine "what to monitor" and "how to monitor" the system elements. A PresentationManager might use the data to access menu-items and views based on user access privileges. References <system_configuration> <site name="MyHouse" > <hosts> <host_ref name="host1"/> </hosts> </site> <group name="mysql" gid="500"/> <user name="mysql" uid="500"> <groups> <group_ref name="mysql"/> </groups> </user> <host name="host1" > <users> <user_ref name="mysql"> </users> <profiles> <profile_ref name="workstation"/> </profiles> </host> <profile name="workstation" > <components> <component_ref name="user-setup" > <component_ref name="mysql-db" > </components> </profile> <component name="user-setup"> </component> <component name="mysql-db"> </component> </system_configuration> Systems engineering

Operating System (OS)

Trisquel Trisquel (full name Trisquel GNU/Linux) is a computer operating system, a Linux distribution, derived from another distribution, Ubuntu. The project aims for a fully free software system without proprietary software or firmware and uses a version of Ubuntu's modified kernel, with the non-free code (binary blobs) removed. Trisquel relies on user donations. Its logo is a triskelion, a Celtic symbol. Trisquel is listed by the Free Software Foundation as a distribution that contains only free software. Overview Four basic versions are available. Trisquel The standard Trisquel distribution includes the MATE desktop environment and graphical user interface (GUI), and English, Spanish and 48 other localizations, 50 in total, on a 2.6 GB live DVD image. Other translations can be downloaded if an internet connection is present during installation. Trisquel Mini Trisquel Mini is an alternative to mainline Trisquel, designed to run well on netbooks and older hardware. It uses the low-resource environment LXDE and lightweight GTK+ and X Window System alternatives to GNOME and Qt-KDE applications. The LXDE desktop only includes English and Spanish localizations, and can install from a 1.2 GB live DVD image. Triskel Triskel is another alternative to mainline Trisquel using the KDE graphical interface, available as a 2.0 GB ISO DVD live image. Trisquel Sugar TOAST Sugar is a free and open source desktop environment designed with the goal of being used by children for interactive learning. Sugar replaces the standard MATE desktop environment available with Trisquel. Trisquel NetInstall NetInstall consists of a 25MB CD iso image with just the minimal amount of software to start the installation via a text based network installer and fetch the remaining packages over the Internet. Internationalization The full installation includes 51 languages (Albanian, Arabic, Aranese, Asturian, Basque, Bulgarian, Catalan, Central Khmer, Simplified Chinese, Traditional Chinese, Croatian, Czech, Danish, Dutch, English, Esperanto, Estonian, Finnish, French, Galician, German, Greek, Hebrew, Hindi, Hungarian, Indonesian, Irish, Italian, Japanese, Korean, Latvian, Lithuanian, Low German, Norwegian Bokmål, Norwegian Nynorsk, Occitan, Punjabi, Polish, Portuguese, Romanian, Russian, Serbian, Slovak, Slovenian, Spanish, Swedish, Tamil, Thai, Turkish, Valencian and Vietnamese) pre-installed in a downloadable 1.2-gigabyte DVD image. Source code for the full Trisquel installation is also available in a downloadable 3-gigabyte DVD image. History The project began in 2004 with sponsorship of the University of Vigo for Galician language support in education software and was officially presented in April 2005 with Richard Stallman, founder of the GNU Project, as a special guest. According to project director Rubén Rodríguez, the support for Galician has created interest in South American and Mexican communities of emigrants from the Province of Ourense. By December 2008, Trisquel was included by the Free Software Foundation (FSF) in its list of Linux distributions endorsed by the Free Software Foundation. Release history The releases that use GNOME 3.x use GNOME Classic/Flashback, rather than the default GNOME Shell. All Trisquel releases starting with version 6 are only based on Ubuntu LTS releases. Current versions include this common software: Abrowser, a rebranded version of Firefox that never suggests non-free add-ons, and includes no trademarked art or names. It features privacy enhancing modifications such as not starting network connections on its own. It is rebranded because the Mozilla Trademark Policy forbids modifications that include their trademark without consent. Gnash, a SWF viewer, instead of Adobe Flash Player, which is proprietary software. Prior editions: Trisquel Pro was business-oriented and small. It was part of the Trisquel 2.0 LTS Robur (2008), but no other release followed. Trisquel Edu was education-oriented, for schools and universities. Like Trisquel Pro, no other release followed Trisquel 2.0 Robur (2008). Trisquel on Sugar was education-oriented, based on the Sugar desktop environment for interactive learning for children. It was released at the same time as Trisquel 7. Trisquel Gamer was an independent edition maintained by David Zaragoza. It included 55 free software games and could boot from a live DVD or USB drive. It was released with Trisquel 3.5 (2010), which is no longer supported. Reception Jesse Smith of DistroWatch reviewed the 4.0 release, Taranis, and described it as refined and dependable. He portrayed difficulty with removing software as his main problem with the release. He complimented it as an operating system that showcased utility instead of mere compliance with free software criteria. Jesse Smith also reviewed Trisquel 7.0 in 2014, writing "Whenever I boot up Trisquel I find myself wondering whether the free software only distribution will be able to hold its own when it comes to hardware drivers, multimedia support and productivity software. The answer I came to when running Trisquel 7.0 is that, yes, the distribution appears to be nearly as capable as operating systems that do not stick to the FSF's definition of free software. Some people who use hardware that requires binary blobs or non-free drivers may face problems and Flash support isn't perfect when using the free Gnash player, but otherwise Trisquel appears to be every bit as functional as other mainstream Linux distributions. The software Trisquel ships with appears to be stable, functional and user friendly. The distribution is easy to install, I found it pleasant to use and I didn't encounter any problems. People who value or wish to promote free software should definitely try running Trisquel, it's an excellent example of what can be accomplished with free software." Jim Lynch of Desktop Linux Reviews reviewed the 5.5 release, Brigantia, and described it as "well-ordered and well developed" and recommended it to users whether they care about only using free software or not. Lynch stated that the release was suitable for beginners and advanced users. Chris Fisher and Matt Hartley of The Linux Action Show! praised the design, ease of use, and hardware support of Trisquel 5.5 and Trisquel 5.5 Mini, but found that the Linux-libre kernel found in Trisquel impedes functionality of proprietary wireless devices. They argued that the distribution was targeting power users and that new users should use a different distribution. Richard Stallman announced in January 2015 that he is using Trisquel on a Thinkpad X60 instead of his former computer the Lemote Yeeloong. Hardware IA-32 and x86-64 CPU architectures are supported since Trisquel 5.5, which includes free software compatible chipsets. See also PureOS Parabola GNU/Linux-libre Comparison of Linux distributions List of Linux distributions based on Ubuntu References External links 2007 software Free software only Linux distributions Spanish-language Linux distributions Ubuntu derivatives Linux distributions

Operating System (OS)

Windows 10 version history Windows 10 is a series of operating systems developed by Microsoft. Microsoft described Windows 10 as an "operating system as a service" that would receive ongoing updates to its features and functionality, augmented with the ability for enterprise environments to receive non-critical updates at a slower pace or use long-term support milestones that will only receive critical updates, such as security patches, over their five-year lifespan of mainstream support. It was first released in July 2015. Channels Windows 10 Insider Preview builds are delivered to Insiders in three different channels (previously "rings"). Insiders in the Dev Channel (previously Fast Ring) receive updates prior to those in the Beta Channel (previously Slow Ring), but might experience more bugs and other issues. Insiders in the Release Preview Channel (previously Release Preview Ring) do not receive updates until the version is almost available to the public, but are comparatively more stable. PC version history Mainstream builds of Windows 10 are labeled "YYMM", with YY representing the two-digit year and MM representing the month of planned release (for example, version 1507 refers to builds which initially released in July 2015). Starting with version 20H2, Windows 10 release nomenclature changed from the year and month pattern to a year and half-year pattern (YYH1, YYH2). Version 1507 Version 1511 (November Update) The second stable build of Windows10 is version 1511 (build number 10586), known as the November Update. It was codenamed "Threshold 2" (TH2) during development. This version was distributed via Windows Update on November 12, 2015. It contains various improvements to the operating system, its user interface, bundled services, as well as the introduction of Skype-based universal messaging apps, and the Windows Store for Business and Windows Update for Business features. On November 21, 2015, the November Update was temporarily pulled from public distribution. The upgrade was re-instated on November 24, 2015, with Microsoft stating that the removal was due to a bug that caused privacy and data collection settings to be reset to defaults when installing the upgrade. Version 1607 (Anniversary Update) The third stable build of Windows 10 is called version 1607, known as the Anniversary Update. It was codenamed "Redstone 1" (RS1) during development. This version was released on August 2, 2016, a little over one year after the first stable release of Windows 10. The Anniversary Update was originally thought to have been set aside for two feature updates. While both were originally to be released in 2016, the second was moved into 2017 so that it would be released in concert with that year's wave of Microsoft first-party devices. The Anniversary Update introduces new features such as the Windows Ink platform, which eases the ability to add stylus input support to Universal Windows Platform apps and provides a new "Ink Workspace" area with links to pen-oriented apps and features, enhancements to Cortana's proactive functionality, a dark user interface theme mode, a new version of Skype designed to work with the Universal Windows Platform, improvements to Universal Windows Platform intended for video games, and offline scanning using Windows Defender. The Anniversary Update also supports Windows Subsystem for Linux, a new component that provides an environment for running Linux-compatible binary software in an Ubuntu-based user mode environment. On new installations of Windows 10 on systems with Secure Boot enabled, all kernel-mode drivers issued after July 29, 2015 must be digitally signed with an Extended Validation Certificate issued by Microsoft. This version is the basis for "LTSB 2016", the first upgrade to the LTSB since Windows 10's release. The first LTSB release, based on RTM (version 1507), has been retroactively named "LTSB 2015". Version 1703 (Creators Update) The fourth stable build of Windows 10 is called version 1703, known as the Creators Update. It was codenamed "Redstone 2" (RS2) during development. This version was announced on October 26, 2016, and was released for general availability on April 11, 2017, and for manual installation via Windows 10 Upgrade Assistant and Media Creation Tool tools on April 5, 2017. This update primarily focuses on content creation, productivity, and gaming features—with a particular focus on virtual and augmented reality (including HoloLens and virtual reality headsets) and on aiding the generation of three-dimensional content. It supports a new virtual reality workspace designed for use with headsets; Microsoft announced that several OEMs planned to release VR headsets designed for use with the Creators Update. Controls for the Game Bar and Game DVR feature have moved to the Settings app, while a new "Game Mode" option allows resources to be prioritized towards games. Integration with Microsoft acquisition Mixer (formerly Beam) was added for live streaming. The themes manager moved to Settings app, and custom accent colors are now possible. The new app Paint 3D allows users to produce artwork using 3D models; the app is designed to make 3D creation more accessible to mainstream users. Windows 10's privacy settings have more detailed explanations of data that the operating system may collect. Additionally, the "enhanced" level of telemetry collection was removed. Windows Update notifications may now be "snoozed" for a period of time, the "active hours" during which Windows will not try to install updates may now extend up to 18 hours in length, and updates may be paused for up to seven days. Windows Defender has been replaced by the universal app Windows Defender Security Center. Devices may optionally be configured to prevent use of software from outside of Microsoft Store, or warn before installation of apps from outside of Microsoft Store. "Dynamic Lock" allows a device to automatically lock if it is outside of the proximity of a designated Bluetooth device, such as a smartphone. A "Night Light" feature was added, which allows the user to change the color temperature of the display to the red part of the spectrum at specific times of day (similarly to the third-party software f.lux). Version 1709 (Fall Creators Update) The fifth stable build of Windows 10 is called version 1709, known as the Fall Creators Update. It was codenamed "Redstone 3" (RS3) during development. This version was released on October 17, 2017. Version 1709 introduces a new feature known as "My People", where shortcuts to "important" contacts can be displayed on the taskbar. Notifications involving these contacts appear above their respective pictures, and users can communicate with the contact via either Skype, e-mail, or text messaging (integrating with Android and Windows 10 Mobile devices). Support for additional services, including Xbox, Skype for Business, and third-party integration, are to be added in the future. Files can also be dragged directly to the contact's picture to share them. My People was originally announced for Creators Update, but was ultimately held over to the next release, and made its first public appearance in Build 16184 in late April 2017. A new "Files-on-Demand" feature for OneDrive serves as a partial replacement for the previous "placeholders" function. It also introduces a new security feature known as "controlled folder access", which can restrict the applications allowed to access specific folders. This feature is designed mainly to defend against file-encrypting ransomware. Version 1803 (April 2018 Update) The sixth stable build of Windows 10 is called version 1803, known as the April 2018 Update. It was codenamed "Redstone 4" (RS4) during development. This version was released as a manual download on April 30, 2018, with a broad rollout on May 8, 2018. This update was originally meant to be released on April 10, but was delayed because of a bug which could increase chances of a "Blue Screen of Death" (Stop error). The most significant feature of this build is Timeline, which is displayed within Task View. It allows users to view a list of recently-used documents and websites from supported applications ("activities"). When users consent to Microsoft data collection via Microsoft Graph, activities can also be synchronized from supported Android and iOS devices. Version 1809 (October 2018 Update) The seventh stable build of Windows 10 is called version 1809, known as the October 2018 Update. It was codenamed "Redstone 5" (RS5) during development. This version was released on October 2, 2018. Highlighted features on this build include updates to the clipboard function (including support for clipboard history and syncing with other devices), SwiftKey virtual keyboard, Snip & Sketch, and File Explorer supporting the dark color scheme mode. On October 6, 2018, the build was pulled by Microsoft following isolated reports of the update process deleting files from user directories. It was re-released to Windows Insider channel on October 9, with Microsoft citing a bug in OneDrive's Known Folder Redirection function as the culprit. On November 13, 2018, Microsoft resumed the rollout of 1809 for a small percentage of users. The long term servicing release, Windows 10 Enterprise 2019 LTSC, is based on this version and is equivalent in terms of features. Version 1903 (May 2019 Update) The eighth stable build of Windows 10, version 1903, codenamed "19H1", was released for general availability on May 21, 2019 after being on the Insider Release Preview branch since April 8, 2019. Because of new practices introduced after the problems affecting the 1809 update, Microsoft used an intentionally slower Windows Update rollout process. New features in the update include a redesigned search tool—separated from Cortana and oriented towards textual queries, a new "Light" theme (set as default on Windows 10 Home) using a white-colored taskbar with dark icons, the addition of symbols and kaomoji to the emoji input menu, the ability to "pause" system updates, automated "Recommended troubleshooting", integration with Google Chrome on Timeline via an extension, support for SMS-based authentication on accounts linked to Microsoft accounts, and the ability to run Windows desktop applications within the Windows Mixed Reality environment (previously restricted to universal apps and SteamVR only). A new feature on Pro, Education, and Enterprise known as Windows Sandbox allows users to run applications within a secured Hyper-V environment. A revamped version of Game Bar was released alongside 1903, which redesigns it into a larger overlay with a performance display, Xbox friends list and social functionality, and audio and streaming settings. Version 1909 (November 2019 Update) The ninth stable build of Windows 10, version 1909, codenamed "19H2", was released to the public on November 12, 2019 after being on the Insider Release Preview branch since August 26, 2019. Unlike previous updates, this one was released as a minor service update without major new features. Version 2004 (May 2020 Update) The tenth stable build of Windows 10, version 2004, codenamed "20H1", was released to the public on May 27, 2020 after being on the Insider Release Preview branch since April 16, 2020. New features included faster and easier access to Bluetooth settings and pairing, improved Kaomojis, renamable virtual desktops, DirectX12 Ultimate, a chat-based UI for Cortana, greater integration with Android phones on the Your Phone app, Windows Subsystem for Linux 2 (WSL 2), and WSL 2 version includes a custom Linux kernel, unlike older WSL, the ability to use Windows Hello without the need for a password, improved Windows Search with integration with File Explorer, a cloud download option to reset Windows, accessibility improvements, and the ability to view disk drive type and discrete graphics card temperatures in Task Manager. Version 20H2 (October 2020 Update) The eleventh stable build of Windows 10, version 20H2, was released to the public on October 20, 2020 after being on the Beta Channel since June 16, 2020. New features include new theme-aware tiles in the Start Menu, new features and improvements to Microsoft Edge (such as a price comparison tool, integration for tab switching, and easy access to pinned tabs), a new out-of-box experience with more personalization for the taskbar, notifications improvements, improvements to tablet mode, improvements to Modern Device Management, and the move of the System tab in Control Panel to the About page in Settings. This is the first version of Windows 10 to include the new Chromium-based Edge browser by default. Version 21H1 (May 2021 Update) The Windows 10 May 2021 Update (codenamed "21H1") is the eleventh update to Windows 10 as the cumulative update to the October 2020 Update. It carries the build number 10.0.19043. The first preview was released to Insiders who opted in to Beta Channel on February 17, 2021. The update began rolling out on May 18, 2021. Notable changes in the May 2021 Update include: Added multi-camera support for Windows Hello New "News and Interests" feature on the taskbar Performance improvements to Windows Defender Application Guard and WMI Group Policy Service Version 21H2 (November 2021 Update) The Windows 10 November 2021 Update (codenamed "21H2") is the twelfth and current major update to Windows 10 as the cumulative update to the May 2021 Update. It carries the build number 10.0.19044. The first preview was released on July 15, 2021 to Insiders who opted in to Release Preview Channel that failed to meet minimum system requirements for Windows 11. The update began rolling out on November 16, 2021. Notable changes in the November 2021 Update include: Support for Wi-Fi 6E GPU compute support in the Windows Subsystem for Linux (WSL) and Azure IoT Edge for Linux on Windows (EFLOW) deployments New simplified passwordless deployment models for Windows Hello for Business Support for WPA3 Hash-to-Element (H2E) standards Fast Ring / Dev Channel Fast Ring On December 16, 2019, Microsoft announced that Windows Insiders in the Fast Ring will receive builds directly from the RS_PRERELEASE branch, which are not matched to a specific Windows 10 release. The first build released under the new strategy, build 19536, was made available to Insiders on the same day. The MN_RELEASE branch was available from May 13, 2020 to June 17, 2020. The branch was mandatory for Insiders in the Fast Ring. Dev Channel As of June 15, 2020, Microsoft has introduced the "channels" model to its Windows Insider Program, succeeding its "ring" model. All future builds starting from build 10.0.20150, therefore, would be released to Windows Insiders in the Dev Channel. The FE_RELEASE branch was available from October 29, 2020 to January 6, 2021. The branch was mandatory for Insiders until December 10. Afterward, Insiders could choose to move back to the RS_PRERELEASE branch. The CO_RELEASE branch was available from April 5 to June 14, 2021. The branch was mandatory for Insiders. As of June 28, 2021, the Dev Channel has transitioned to Windows 11. Mobile version history See also Windows Server 2016 version history Windows Server 2019 version history Windows Phone version history Windows 10 Mobile version history Xbox OS version history Windows 11 version history References External links Windows release health Flight Hub History of Microsoft Software version histories Tablet operating systems

Operating System (OS)

Windows 8.1 Windows 8.1 is a release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on August 27, 2013, and broadly released for retail sale on October 17, 2013, about a year after the retail release of its predecessor, and succeeded by Windows 10 on July 29, 2015. Windows 8.1 was made available for download via MSDN and Technet and available as a free upgrade for retail copies of Windows 8 and Windows RT users via the Windows Store. A server counterpart was released on October 18, 2013, entitled Windows Server 2012 R2. Microsoft ended mainstream support for Windows 8.1 on January 9, 2018, and extended support will end on January 10, 2023. Windows 8.1 aimed to address complaints of Windows 8 users and reviewers on launch. Visible enhancements include an improved Start screen, additional snap views, additional bundled apps, tighter OneDrive (formerly SkyDrive) integration, Internet Explorer 11 (IE11), a Bing-powered unified search system, restoration of a visible Start button on the start menu, and the ability to restore the previous behavior of opening the user's desktop on login instead of the Start screen. IE11 was also included with the release of its successor, Windows 10, on July 29, 2015, but Microsoft Edge is the default browser in this version of Windows, and there, Internet Explorer is configured to run websites based on legacy HTML technologies. Windows 8.1 also added support for such emerging technologies as high-resolution displays, 3D printing, Wi-Fi Direct, and Miracast streaming, as well as the ReFS file system. After January 12, 2016, Microsoft announced that Windows 8 users would need to upgrade to Windows 8.1 or Windows 10 for continued support. Windows 8.1 received more positive reception than Windows 8, with critics praising the expanded functionality available to apps in comparison to Windows 8, its OneDrive integration, its user interface tweaks, and the addition of expanded tutorials for operating the Windows 8 interface. Despite these improvements, Windows 8.1 was still criticized for not addressing all issues of Windows 8 (such as poor integration between Metro-style apps and the desktop interface), and the potential privacy implications of the expanded use of online services. , 2.94% of traditional PCs running Windows were running Windows 8.1, making it 4th most popular Windows since Windows 11 surpassed it. History In February 2013, ZDNet writer Mary Jo Foley disclosed potential rumors about "Blue", the codename for a wave of planned updates across several Microsoft products and services, including Windows 8, Windows Phone 8, Outlook.com, and SkyDrive. In particular, the report detailed that Microsoft was planning to shift to a more "continuous" development model, which would see major revisions to its main software platforms released on a consistent yearly cycle to keep up with market demands. Lending credibility to the reports, Foley noted that a Microsoft staff member had listed experience with "Windows Blue" on his LinkedIn profile, and listed it as a separate operating system from 8. A post-RTM build of Windows 8, build 9364, was leaked in March 2013. The build, which was believed to be of "Windows Blue", revealed a number of enhancements across Windows 8's interface, including additional size options for tiles, expanded color options on the Start screen, the expansion of PC Settings to include more options that were previously exclusive to the desktop Control Panel, the ability for apps to snap to half of the screen, the ability to take screenshots from the Share charm, additional stock apps, increased SkyDrive integration (such as automatic device backups) and Internet Explorer 11. Shortly afterward on March 26, 2013, corporate vice president of corporate communications Frank X. Shaw officially acknowledged the "Blue" project, stating that continuous development would be "the new normal" at Microsoft, and that "our product groups are also taking a unified planning approach so people get what they want—all of their devices, apps and services working together wherever they are and for whatever they are doing." In early May, press reports announcing the upcoming version in Financial Times and The Economist negatively compared Windows 8 to New Coke. The theme was then echoed and debated in the computer press. Shaw rejected this criticism as "extreme", adding that he saw a comparison with Diet Coke as more appropriate. On May 14, 2013, Microsoft announced that "Blue" was officially unveiled as Windows 8.1. Following a keynote presentation focusing on this version, the public beta of Windows 8.1 was released on June 26, 2013, during Build. Build 9600 of Windows 8.1 was released to OEM hardware partners on August 27, 2013, and became generally available on October 17, 2013. Unlike past releases of Windows and its service packs, volume license customers and subscribers to MSDN Plus and TechNet Plus were unable to obtain the RTM version upon its release; a spokesperson stated that the change in policy was to allow Microsoft to work with OEMs "to ensure a quality experience at general availability." Microsoft stated that Windows 8.1 would be released to the general public on October 17, 2013. However, after criticism, Microsoft reversed its decision and released the RTM build on MSDN and TechNet on September 9, 2013. Microsoft announced that Windows 8.1, along with Windows Server 2012 R2, was released to manufacturing on August 27, 2013. Prior to the release of Windows 8.1, Microsoft premiered a new television commercial in late-September 2013 that focused on its changes as part of the "Windows Everywhere" campaign. Shortly after its release, Windows RT 8.1 was temporarily recalled by Microsoft following reports that some users had encountered a rare bug which corrupted the operating system's Boot Configuration Data during installation, resulting in an error on startup. On October 21, 2013, Microsoft confirmed that the bug was limited to the original Surface tablet, and only affected 1 in 1000 installations. The company released recovery media and instructions which could be used to repair the device, and restored access to Windows RT 8.1 the next day. It was also found that changes to screen resolution handling on Windows 8.1 resulted in mouse input lag in certain video games that do not use the DirectInput API's—particularly first-person shooter games, including Deus Ex: Human Revolution, Hitman: Absolution, and Metro 2033. Users also found the issues to be more pronounced when using gaming mice with high resolution and/or polling rates. Microsoft released a patch to fix the bug on certain games in November 2013, and acknowledged that it was caused by "changes to mouse-input processing for low-latency interaction scenarios". Update On April 8, 2014, Microsoft released the Windows 8.1 Update, which included all past updates plus new features. It was unveiled by Microsoft vice president Joe Belfiore at Mobile World Congress on February 23, 2014, and detailed in full at Microsoft's Build conference on April 2. Belfiore noted that the update would lower the minimum system requirements for Windows, so it can be installed on devices with as little as 1 GB of RAM and 16 GB of storage. Unlike Windows 8.1 itself, this cumulative update is distributed through Windows Update, and must be installed in order to receive any further patches for Windows 8.1. At the 2014 Build conference, during April, Microsoft's Terry Myerson unveiled further user interface changes for Windows 8.1, including the ability to run Metro-style apps inside desktop windows, and a revised Start menu, which creates a compromise between the Start menu design used by Windows 7 and the Start screen, by combining the application listing in the first column with a second that can be used to display app tiles, whereas Windows 8.0 used a screen hotspot ("hot corner"). Myerson stated that these changes would occur in a future update, but did not elaborate further. A distinction is the removal of the tooltip with the preview thumbnail of the Start screen. Microsoft also unveiled a concept known as "Universal Windows apps", in which a Windows Runtime app can be ported to Windows Phone 8.1 and Xbox One while sharing a common codebase. While it does not entirely unify Windows' app ecosystem with that of Windows Phone, it will allow developers to synchronize data between versions of their app on each platform, and bundle access to Windows, Windows Phone, and Xbox One versions of an app in a single purchase. Microsoft originally announced that users who did not install the update would not receive any other updates after May 13, 2014. However, meeting this deadline proved challenging: The ability to deploy Windows 8.1 Update through Windows Server Update Services (WSUS) was disabled shortly after its release following the discovery of a bug which affects the ability to use WSUS as a whole in certain server configurations. Microsoft later fixed the issue but users continued to report that the update may fail to install. Microsoft's attempt to fix the problem was ineffective, to the point that Microsoft pushed the support deadline further to June 30, 2014. On 16 May, Microsoft released additional updates to fix a problem of BSOD in the update. Distribution Microsoft markets Windows 8.1 as an "update" for Windows 8, avoiding the term "upgrade." Microsoft's support lifecycle policy treats Windows 8.1 similar to previous service packs of Windows: It is part of Windows 8's support lifecycle, and upgrading to Windows 8.1 is required to maintain access to support and Windows updates after January 12, 2016. Retail and OEM copies of Windows 8, Windows 8 Pro, and Windows RT can be upgraded through Windows Store free of charge. However, volume license customers, TechNet or MSDN subscribers and users of Windows 8 Enterprise must acquire standalone installation media for Windows 8.1 and install through the traditional Windows setup process, either as an in-place upgrade or clean install. This requires a Windows 8.1-specific product key. Upgrading through Windows Store requires each machine to download an upgrade package as big as 2–3.6 GB. Unlike the traditional Windows service packs, the standalone installer, which could be downloaded once and installed as many times as needed, requires a Windows 8.1-specific product key. On July 1, 2014, acknowledging difficulties users may have had through the Windows Store update method, Microsoft began to phase in an automatic download process for Windows 8.1. Windows 8 was re-issued at retail as Windows 8.1 alongside the online upgrade for those who did not currently own a Windows 8 license. Retail copies of Windows 8.1 contain "Full" licenses that can be installed on any computer, regardless of their existing operating system, unlike Windows 8 retail copies, which were only available at retail with upgrade licenses. Microsoft stated that the change was in response to customer feedback, and to allow more flexibility for users. Pricing for the retail copies of Windows 8.1 remained the same. Windows 8.1 with Bing is a reduced-cost SKU of Windows 8.1 that was introduced by Microsoft in May 2014 in an effort to further encourage the production of low-cost Windows devices, whilst "driving end-user usage of Microsoft Services such as Bing and OneDrive". It is subsidized by Microsoft's Bing search engine, which is set as the default within Internet Explorer and cannot be changed by OEMs. However, this restriction does not apply to end-users, who can still change the default search engine freely. It is otherwise and functionally identical to the base edition of Windows 8.1. New and changed features Many of the changes on Windows 8.1, particularly to the user interface, were made in response to criticisms from early adopters and other critics after the release of Windows 8. User interface and desktop The Start screen received several enhancements on Windows 8.1, including an extended "All Apps" view with sort modes (accessed by clicking a new down arrow button or swiping upward), small and extra-large sizes for tiles, and colored tiles for desktop program shortcuts. Additional customization options were also added, such as expanded color options, new backgrounds (some of which incorporate animated elements), and the ability for the Start screen to use the desktop background instead. Applications were no longer added to the Start screen automatically when installed, and all applications now have colored tiles (desktop programs were previously shown in a single color). The app snapping system was also extended; up to four apps can be snapped onto a single display depending on screen size, apps can be snapped to fill half the screen, and can also be used on any display in a multi-monitor configuration. Apps can also launch other apps in a snapped view to display content; for example, the Mail app can open a photo attachment in a picture viewer snapped to another half of the screen. Improved support is also provided by apps for using devices in a portrait (vertical) orientation. The lock screen offers the ability to use a photo slideshow as its backdrop, and a shortcut to the Camera app by swiping up. The on-screen keyboard has an improved autocomplete mechanism which displays multiple word suggestions, and allows users to select from them by sliding on the spacebar. The autocomplete dictionary is also automatically updated using data from Bing, allowing it to recognize and suggest words relating to current trends and events. Similarly to Windows Phone, certain apps now display a narrow bar with three dots on it to indicate the presence of a pop-up menu accessible by swiping, clicking on the dots, or right-clicking. To improve the usability of the desktop interface, a visible Start button was restored to the taskbar for opening the Start screen, and the Quick Links menu (accessed by right-clicking the Start button or pressing ) now contains shutdown and sign-out options. Users can also modify certain user interface behaviors, such as disabling the upper hot corners for using the charms and recent apps list, going to the desktop instead of the Start screen on login or after closing all apps on a screen, automatically opening the "All Apps" view on the Start screen when opened, and prioritizing desktop programs on the "Category" sort mode on "All Apps". To assist users in learning the Windows 8 user interface, an interactive tutorial was also offered, along with a new Help + Tips app for additional information. In contrast, Windows RT 8.1 downplays the desktop interface further by not displaying the Desktop tile on its default Start screen at all (however, it can still be manually added to the Start screen). Windows manager Chaitanya Sareen stated that the restoration of the visible Start button was intended to be a "warm blanket" for users who had become confused by the removal of the button on 8; the Start button was originally removed to reflect Windows 8's treatment of the desktop as an "app" rather than the main interface. Further interface behavior changes are made on the April 2014 "Windows 8.1 Update", which are oriented towards non-touch environments (such as desktop and laptop PCs) that use a keyboard and mouse, and improve integration between Windows Store apps and the desktop. When a mouse is in use, the Desktop is shown on startup by default, the Start screen uses context menus instead of a toolbar across the bottom of the screen for manipulating tiles, an autohiding title bar with minimize and close buttons is displayed within apps at the top of the screen, the taskbar can display and pin apps alongside desktop programs and be accessed from within apps, and visible search and power buttons are added to the Start screen. In non-touch environments, the default image viewer and media player programs were changed back to Windows Photo Viewer and Windows Media Player in lieu of the Xbox Video and Photos apps. Apps The suite of pre-loaded apps bundled with Windows 8 were changed in Windows 8.1; PC Settings was expanded to include options that were previously exclusive to the desktop Control Panel, Windows Store was updated with an improved interface for browsing apps and automatic updates, the Mail app includes an updated interface and additional features, the Camera app integrates Photosynth for creating panoramas, and additional editing tools were added to the Photos app (while integration with Flickr and Facebook was completely removed). A number of additional stock apps were also added, including Calculator, Food and Drink, Health and Fitness, Sound Recorder, Reading List (which can be used to collect and sync content from apps through OneDrive), Scan, and Help + Tips. For Windows RT users, Windows 8.1 also adds a version of Microsoft Outlook to the included Office 2013 RT suite. However, it does not support data loss protection, Group Policy, Lync integration, or creating emails with information rights management. Windows Store is enabled by default within Windows To Go environments. On January 31, 2020, Microsoft released the new Microsoft Edge web browser for Windows 8.1. Online services and functionality Windows 8.1 adds tighter integration with several Microsoft-owned services. OneDrive (formerly SkyDrive) is integrated at the system level to sync user settings and files. Files are automatically downloaded in the background when they are accessed from the user's OneDrive folder, unless they are marked to be available offline. By default, only file metadata and thumbnails are stored locally, and reparse points are used to give the appearance of a normal directory structure to provide backwards compatibility. The OneDrive app was updated to include a local file manager. OneDrive use on Windows 8.1 requires that a user's Windows account be linked to a Microsoft account; the previous SkyDrive desktop client (which did not have this requirement) is not supported on Windows 8.1. A Bing-based unified search system was added; it can analyze a user's search habits to return results featuring relevant local and online content. Full-screen "hero" displays aggregate news articles, Wikipedia entries, multimedia, and other content related to a search query; for instance, searching for a music performer would return photos of the performer, a biography, and their available songs and albums on Xbox Music. The messaging app from Windows 8 has been replaced by Skype, which also allows users to accept calls directly from the lock screen. Windows 8.1 also includes Internet Explorer 11, which adds support for SPDY and WebGL, and expanded developer tools. The Metro-style variant of IE11 also adds tab syncing, the ability to open an unlimited number of tabs, and Reading List integration. Due to Facebook Connect service changes, Facebook support is disabled in all bundled apps effective June 8, 2015. Security and hardware compatibility On compatible hardware, Windows 8.1 also features a transparent "device encryption" system based on BitLocker. Encryption begins as soon as a user begins using the system; the recovery key is stored to either the user's Microsoft account or an Active Directory login, allowing it to be retrieved from any computer. While device encryption is offered on all editions of Windows 8.1 unlike BitLocker (which is exclusive to the Pro and Enterprise editions), device encryption requires that the device meet the Connected Standby specification and have a Trusted Platform Module (TPM) 2.0 chip. Windows 8.1 also introduces improved fingerprint recognition APIs, which allows user login, User Account Control, Windows Store and Windows Store apps to use enrolled fingerprints as an authentication method. A new kiosk mode known as "Assigned Access" was also added, allowing a device to be configured to use a single app in a restricted environment. Additionally, Windows Defender includes an intrusion detection system which can scan network activity for signs of malware. Windows 8.1 also allows third-party VPN clients to automatically trigger connections. For enterprise device management, Windows 8.1 adds support for the Workplace Join feature of Windows Server 2012 R2, which allows users to enroll their own device into corporate networks with finer control over access to resources and security requirements. Windows 8.1 also supports the OMA Device Management specifications. Remote Data Control can be used to remotely wipe specific "corporate" data from Windows 8.1 devices. The 64-bit variants of Windows 8.1 no longer support processors which do not implement the double-width compare and exchange (CMPXCHG16B) CPU instruction (which the installer reports as a lack of support for "CompareExchange128"). A Microsoft spokesperson noted that the change primarily affects systems with older AMD 64-bit processors, and that "the number of affected processors are extremely small since this instruction has been supported for greater than 10 years." It mostly concerns Socket 754 and Socket 939 Athlon 64 from 2004 and 2005; the Socket AM2 CPUs should all have the instruction. Brad Chacos of PC World also reported a case in which Windows 8.1 rejected Intel Core 2 Quad Q9300 and a Q9550S despite their support for this instruction, because the associated Intel DP35DP motherboard did not. These changes do not affect the 32-bit variants of Windows 8.1. Hardware functionality Windows 8.1 adds support for 3D printing, pairing with printers using NFC tags, Wi-Fi Direct, Miracast media streaming, tethering, and NVMe. In response to the increasing pixel density in displays, Windows 8.1 can scale text and GUI elements up to 200% (whereas Windows 8 supported only 150%) and set scaling settings independently on each display in multi-monitor configurations. Removed features Backup and Restore, the backup component of Windows that had been deprecated but was available in Windows 8 through a Control Panel applet called "Windows 7 File Recovery", was removed. Windows 8.1 also removes the graphical user interface for the Windows System Assessment Tool, meaning that the Windows Experience Index is no longer displayed. The command line variant of the tool remains available on the system. Microsoft reportedly removed the graphical Windows Experience Index in order to promote the idea that all kinds of hardware run Windows 8 equally well. Windows 8.1 removed the ability of several Universal Windows Platform apps to act as "hubs" connecting similar services within a single interface: The Photos app lost the ability to view photos from Facebook, Flickr or SkyDrive (branded as OneDrive since February 2014). Instead, each service provider is expected to create its own app; The Messaging app, which was interoperable with Windows Live Messenger and Facebook Chat, was deprecated in favor of a Skype app that is not compatible with Facebook Chat; The Calendar app can only connect to Microsoft services such as Outlook.com and Microsoft Exchange, with support for Google Calendar removed. Since October 2016, all future patches are cumulative as with Windows 10; individual patches can no longer be downloaded. Reception Windows 8.1 received more positive reviews than Windows 8. Tom Warren of The Verge still considered the platform to be a "work in progress" due to the number of apps available, the impaired level of capabilities that apps have in comparison to desktop programs, and because he felt that mouse and keyboard navigation was still "awkward". However, he touted many of the major changes on Windows 8.1, such as the expanded snapping functionality, increased Start screen customization, SkyDrive and Bing integration, improvements to stock apps, and particularly he considered the Mail app to be "lightyears ahead" of the original version from 8. He concluded that "Microsoft has achieved a lot within 12 months, even a lot of the additions feel like they should have been there from the very start with Windows 8." Joel Hruska of ExtremeTech criticized continuing integration problems between the Desktop and apps on Windows 8.1, pointing out examples such as the Photos app, which "still refuses to acknowledge that users might have previous photo directories", and that the Mail app "still can’t talk to the desktop—if you try to send an email from the Desktop without another mail client installed, Windows will tell you there’s no mail client capable of performing that action." However, he praised the improvements to other apps, such as People and News (pointing out UI improvements, and the News app using proper links when sharing stories, rather than non-standard links that can only be recognized by the app). Although praising the more flexible snapping system, he still pointed out flaws, such as an inability to maintain snap configurations in certain situations. Windows 8.1's search functionality was met with mixed reviews; while noting the Bing integration and updated design, the system was panned for arbitrarily leaving out secondary storage devices from the "Everything" mode. Peter Bright of Ars Technica praised many of the improvements on Windows 8.1, such as its more "complete" touch interface, the "reasonable" tutorial content, the new autocomplete tools on the on-screen keyboard, software improvements, and the deep SkyDrive integration. However, he felt that the transition between the desktop and apps "still tends to feel a bit disjointed and disconnected" (even though the option to use the desktop wallpaper on the Start screen made it feel more integrated with the desktop interface rather than dissimilar), and that the restoration of the Start button made the two interfaces feel even more inconsistent because of how different it operates between the desktop and apps. Certain aspects of Windows 8.1 were also cause for concern because of their privacy implications. In his review of Windows 8.1, Joel Hruska noted that Microsoft had deliberately made it harder for users to create a "Local" account that is not tied to a Microsoft account for syncing, as it "[makes] clear that the company really, really, wants you to share everything you do with it, and that’s not something an increasing number of people and businesses are comfortable doing." Woody Leonhard of InfoWorld noted that by default Windows 8.1's "Smart Search" system sends search queries and other information to Microsoft, which could be used for targeted advertising. Leonhard considered this to be ironic, given that Microsoft had criticized Google's use of similar tactics with its "Scroogled" advertising campaign. Market share According to Net Applications, the adoption rate in March 2015 for Windows 8.1 was at 10.55%, three times that of the original Windows 8 at 3.52%. Windows 8.1 reached a peak adoption rate of 13.12% in June 2015 compared with Windows 8 peak adoption rate of 8.02% in September 2013. End-of-life In May 2019, Microsoft announced that it will end support for Windows 8.1 on January 10, 2023. See also Comparison of operating systems History of operating systems List of operating systems Microsoft Windows version history References Further reading External links Windows 8.1 Update (KB 2919355) Windows 8.1 update history Introducing Windows 8.1 for IT Professionals - Technical Overview Bott, Ed. (2013) 2013 software IA-32 operating systems Windows 8 8.1 X86-64 operating systems Tablet operating systems

Operating System (OS)

Support programs for OS/360 and successors This article discusses support programs included in or available for OS/360 and successors. IBM categorizes some of these programs as utilities and others as service aids; the boundaries are not always consistent or obvious. Many, but not all, of these programs match the types in utility software. The following lists describe programs associated with OS/360 and successors. No DOS, TPF or VM utilities are included. History/Common JCL Many of these programs were designed by IBM users, through the group SHARE, and then modified or extended by IBM from versions originally written by a user. These programs are usually invoked via Job Control Language (JCL). They tend to use common JCL DD identifiers (in the OS, now z/OS operating systems) for their data sets: Dataset utilities IDCAMS IDCAMS ("Access Method Services") generates and modifies Virtual Storage Access Method (VSAM) and Non-VSAM datasets. IDCAMS was introduced along with VSAM in OS/VS; the "Access Method" reference derives from the initial "VSAM replaces all other access methods" mindset of OS/VS. IDCAMS probably has the most functionality of all the utility programs, performing many functions, for both VSAM and non-VSAM files. The following example illustrates the use of IDCAMS to copy a dataset to disk. The dataset has 80-byte records, and the system will choose the block size for the output: //XXXXXXXW JOB XXXXXXX,AAAA,CLASS=G,MSGCLASS=1,NOTIFY=&SYSUID //STEP001 EXEC PGM=IDCAMS //SYSIN DD * REPRO INFILE(FILE01) OUTFILE(FILE02) /* //FILE01 DD DSN=PROD.FILE1.INPUT,disp=shr ..... //FILE02 DD DSN=PROD.FILE2.OUTPUT, // DISP=(NEW,CATLG,DELETE), // UNIT=DASD, // SPACE=(TRK,(100,10),RLSE), // DCB=(RECFM=FB,BLKSIZE=0,LRECL=80) //SYSPRINT DD SYSOUT=* //SYSOUT DD SYSOUT=* //SYSUDUMP DD SYSOUT=* //* In the example above, SYSIN control cards are coming from an in-stream file, but you can instead point to any sequential file or a PDS member containing control cards or a temporary data-set, if you wish. Example of using SYSIN files would be something like this: //SYSIN DD DSN=PROD.MYFILE.REPRO,DISP=SHR or this: //SYSIN DD DSN=PROD.MYLIB.CNTLLIB(REPRO), // DISP=SHR IEBCOMPR IEBCOMPR compares records in sequential or partitioned data sets. The IEBCOMPR utility is used to compare two sequential or partitioned datasets. This data set comparison is performed at the logical record level. Therefore, IEBCOMPR is commonly used to verify that a backup copy of a data set is correct (exact match to the original). During processing, IEBCOMPR compares each record from each data set, one by one. If the records are unequal, IEBCOMPR lists the following information in the SYSOUT: The record and block numbers in question. The names of the DD statements in which the inconsistency occurred. The unequal records. When comparing sequential data sets, IEBCOMPR considers the data sets equal if the following conditions are met: The data sets contain the same number of records. The corresponding records and keys are identical. For partitioned data sets, IEBCOMPR considers the data sets equal if the following conditions are met: The directory entries for the two partitioned data sets match - that is, the names are the same, and the number of entries are equal. The corresponding members contain the same number of records. The corresponding records and keys are identical. If ten unequal comparisons are encountered during processing, IECOMPR terminates with the appropriate message. //XXXXXXXW JOB XXXXXXX,AAAA.A.A,CLASS=G,MSGCLASS=1,NOTIFY=XXXXX //STEP01 EXEC PGM=IEBCOMPR,ACCT=PJ00000000 // INCLUDE MEMBER=@BATCHS //*SYSIN DD DUMMY //SYSIN DD * COMPARE TYPORG=PO /* //SYSUT1 DD DSN=XXXXXXX.OLDFILE,UNIT=DASD,DISP=SHR //SYSUT2 DD DSN=XXXXXXX.NEWFILE,UNIT=DASD,DISP=SHR //SYSUT# DD Note: IEBCOMPR is not a very flexible or user-friendly compare program. It can't restrict the comparison to only certain columns, it can't ignore differences in white space, it doesn't tell you where in the record the difference occurs, and it halts after 10 differences. On the other hand, it is fast, and it is present on all IBM mainframes. So it is very useful when an exact match is expected, such as comparing load modules that have not been reblocked, or checking that a copy worked properly. For comparisons of programs or reports, the ISPF SuperC (ISRSUPC) compare program is often used instead. IEBCOPY IEBCOPY copies, compresses and merges partitioned data sets. It can also select or exclude specified members during the copy operation, and rename or replace members. Some of the tasks that IEBCOPY can perform include the following: Creating an unload of a partitioned data set (PDS) to a PS dataset, for backup or transmission. Copying a PDS in place to reclaim the unused space from deleted members; also called compressing a PDS. Copying selected members to another PDS. Renaming selected members of a PDS. Merging multiple partitioned data sets into a single PDS. Altering, copying and reblocking load modules. Members that are already present in another PDS will not get replaced unless the R option is specified. For the IEBCOPY utility, the required job control statements for a copy are as follows: //stepname EXEC PGM=IEBCOPY //SYSPRINT DD SYSOUT=class //MYDD1 DD DSN=xxxx.ppp.psps,DISP=SHR //MYDD2 DD DSN=xxxx.ppp.pssp,DISP=SHR //SYSIN DD * COPY INDD=MYDD1,OUTDD=MYDD2 SELECT MEMBER=(MEM1,MEM2,MEM3)/ EXCLUDE MEMBER=(SF,DF,SA) The MYDD1 and MYDD2 DD statements are names chosen by the user for the partitioned input and output data sets, respectively; The defaults are SYSUT1 and SYSUT2. You can use any valid DDNAME for these two DD statements. These DDNAMEs are specified in the utility control statements to tell IEBCOPY the name of the input and output data sets. You only need one DD statement for a PDS to be compressed. IEBDG IEBDG ('Data Generator') creates test datasets consisting of patterned data. Control statements define the fields of the records to be created, including position, length, format, and initialization to be performed. IEBDG can use an existing dataset as input and change fields as specified in the control statements, for example replacing a name field by random alphabetic text. The contents of each field may be varied for each record, for example by rotating the characters in an alphanumeric field left or right for each subsequent record. Example: //XXXXXXXW JOB XXXXXXX,AAAA,CLASS=G,MSGCLASS=1,NOTIFY=&SYSUID //********************************************************************** //* CREATION OF A DATASET To BE USED LATER ON //********************************************************************** //CRSTEP EXEC PGM=IEFBR14 //DDCREA DD DSN=&SYSUID..MVSUT.SEQOUT,DISP=(NEW,CATLG) //********************************************************************** //* CREATION OF THE TESTDATA //********************************************************************** //STEP1 EXEC PGM=IEBDG //SYSPRINT DD SYSOUT=* //SEQOUT DD DSN=&SYSUID..MVSUT.SEQOUT,DISP=OLD //SYSIN DD DATA DSD OUTPUT=(SEQOUT) FD NAME=FIELD1,LENGTH=30,STARTLOC=1,FORMAT=AL,ACTION=TL FD NAME=FIELD2,LENGTH=30,STARTLOC=31,FORMAT=AL,ACTION=TR FD NAME=FIELD3,LENGTH=10,STARTLOC=71,PICTURE=10, X P'1234567890',INDEX=1 CREATE QUANTITY=500,NAME=(FIELD1,FIELD2,FIELD3),FILL=X'FF' END /* //********************************************************************** //* PRINTING THE TEST DATA TO SYSOUT //********************************************************************** //STEP2 EXEC PGM=IEBGENER //SYSPRINT DD SYSOUT=* //SYSUT1 DD DSN=*.STEP1.SEQOUT,DISP=SHR //SYSIN DD DUMMY //SYSUT2 DD SYSOUT=* //********************************************************************** //* DELETE THE CREATED DATASET, EVEN IF PREVIOUS STEPS ABENDED //********************************************************************** //DLSTEP EXEC PGM=IEFBR14,COND=EVEN //DDDEL DD DSN=&SYSUID..MVSUT.SEQOUT,DISP=(OLD,DELETE,DELETE) // IEBEDIT IEBEDIT selectively copies portions of JCL. An example of an IEBEDIT program: //IEBEDITJ JOB ACCT,'',CLASS=P,MSGCLASS=T,MSGLEVEL=(1,1),NOTIFY=&SYSUID //STEP0001 EXEC PGM=IEBEDIT //SYSPRINT DD SYSOUT=* //SYSUT1 DD DSN=xxxxx.yyyyy.zzzzz,DISP=SHR //SYSUT2 DD SYSOUT=(*,INTRDR) //SYSIN DD * EDIT TYPE=INCLUDE,STEPNAME=(STEP10,STEP5,STEP15) /* // In this example, data set xxxxx.yyyyy.zzzzz should contain job(s) (which should include steps named STEP5, STEP10, and STEP15). This IEBEDIT routine copies the selected steps of the job onto the SYSUT2 output file (in this example, the internal reader). The syntax of the EDIT statement is: [label] EDIT [START=jobname] [,TYPE={POSITION|INCLUDE|EXCLUDE}] [,STEPNAME=(namelist)] [,NOPRINT] START=jobname specifies the name of the input job to which the EDIT statement applies. Each EDIT statement must apply to a separate job. If START is specified without TYPE and STEPNAME, the JOB statement and all job steps for the specified job are included in the output. Default: If START is omitted and only one EDIT statement is provided, the first job encountered in the input data set is processed. If START is omitted from an EDIT statement other than the first statement, processing continues with the next JOB statement found in the input data set. TYPE={POSITION|INCLUDE|EXCLUDE} specifies the contents of the output data set. These values can be coded: POSITION specifies that the output is to consist of a JOB statement, the job step specified in the STEPNAME parameter, and all steps that follow that job step. All job steps preceding the specified step are omitted from the operation. POSITION is the default. INCLUDE specifies that the output data set is to contain a JOB statement and all job steps specified in the STEPNAME parameter. EXCLUDE specifies that the output data set is to contain a JOB statement and all job steps belonging to the job except those steps specified in the STEPNAME parameter. STEPNAME=(namelist) specifies the names of the job steps that you want to process. namelist can be a single job step name, a list of step names separated by commas, or a sequential range of steps separated by a hyphen (for example, STEPA-STEPE). Any combination of these may be used in one namelist. If more than one step name is specified, the entire namelist must be enclosed in parentheses. When coded with TYPE=POSITION, STEPNAME specifies the first job step to be placed in the output data set. Job steps preceding this step are not copied to the output data set. When coded with TYPE=INCLUDE or TYPE=EXCLUDE, STEPNAME specifies the names of job steps that are to be included in or excluded from the operation. For example, STEPNAME=(STEPA,STEPF-STEPL,STEPZ) indicates that job steps STEPA, STEPF through STEPL, and STEPZ are to be included in or excluded from the operation. If STEPNAME is omitted, the entire input job whose name is specified on the EDIT statement is copied. If no job name is specified, the first job encountered is processed. NOPRINT specifies that the message data set is not to include a listing of the output data set. Default: The resultant output is listed in the message data set. See here for more info: IEBGENER IEBGENER copies records from a sequential dataset, or creates a partitioned dataset. Some of the tasks that IEBGENER can perform include the following: Creating a backup of a sequential data set or a member of a PDS. Changing the physical block size or logical record length of a sequential data set. Creating an edited data set. Printing a sequential data set or a member of a PDS. Creating partitioned output data set from sequential input data set. An example of an IEBGENER program to copy one dataset to another: //IEBGENER JOB ACCT,'DATA COPY',MSGCLASS=J,CLASS=A //STEP010 EXEC PGM=IEBGENER //SYSUT1 DD DSN=xxxxx.yyyyy.zzzzz,DISP=SHR //SYSUT2 DD DSN=aaaaa.bbbbb.ccccc,DISP=(,CATLG), // UNIT=SYSDA,SPACE=(TRK,(5,5),RLSE), // DCB=(RECFM=FB,LRECL=1440) //SYSPRINT DD SYSOUT=* //SYSIN DD DUMMY For straight copy tasks, the sort program can often do these faster than IEBGENER. Thus many mainframe shops make use of an option that automatically routes such tasks to the sort ICEGENER program instead of IEBGENER. On some systems it is possible to send email from a batch job by directing the output to the "SMTP" external writer. On such systems, the technique is as follows: //IEBGENER JOB ACCT,'DATA COPY',MSGCLASS=J,CLASS=A //NORMRC EXEC PGM=IEBGENER //SYSPRINT DD SYSOUT=* //SYSUT1 DD *,LRECL=80 HELO <SYSTEMID> MAIL FROM:<USERID@SYSTEMID> RCPT TO:<USERID@SYSTEMID> DATA From: <USERID@SYSTEMID> To: <USERID@SYSTEMID> Subject: Test Mail TEST MAIL FROM MAINFRAME . QUIT /* //SYSUT2 DD SYSOUT=(B,SMTP),LRECL=80 //SYSIN DD DUMMY It is also possible to attach files while sending the email from Mainframe. IEBIMAGE IEBIMAGE manipulates several types of definitions (AKA images) for the IBM 3800 laser printing subsystem and the IBM 4248 printer. Common uses are for forms control buffers (FCBs), character arrangement tables, character definitions and images of forms to be printed on the output along with the text, for company logos to be printed on the page, or just to print 'graybar' pages (alternating gray & white horizontal backgrounds, to match the previous greenbar paper). With this utility, many different forms or logos could be stored as images, and printed when needed, all using the same standard blank paper, thus eliminating the need to stock many preprinted forms, and the need for operators to stop the printer and change paper. IEBISAM IEBISAM unloads, loads, copies and prints ISAM datasets. Extracted from IBM manual SC26-7414-08 z/OS DFSMSdfp Utilities: The IEBISAM program is no longer distributed. Starting in z/OS V1R7, ISAM data sets can no longer be processed (created, opened, copied or dumped). ISAM data sets that are still in use must be converted to VSAM key-sequenced data sets. Prior to z/OS V1R7, you could use access method services to allocate a VSAM key-sequenced data set and copy an ISAM data set into it. IEBPTPCH IEBPTPCH ("PrinT and PunCH") prints or punches records from a sequential or partitioned dataset. Some of the tasks that IEBPTPCH can perform include the following: Printing or punching an entire data set, sequential or partitioned (PDS). Printing or punching selected PDS members. Printing or punching selected records from a sequential or partitioned data set. Printing or punching a PDS directory. Printing or punching an edited version of a sequential data set or PDS. Check for empty dataset //IEBPTPCH JOB // EXEC PGM=IEBPTPCH //SYSIN DD * PRINT MAXFLDS=2 TITLE ITEM=('Name',22), ITEM=('GPA',50) TITLE ITEM=(' ',1) RECORD FIELD=(25,1,,22), FIELD=(4,51,,50) /* //SYSPRINT DD SYSOUT=* //SYSUT1 DD * Person 1 307 C Meshel Hall 3.89 Second person 123 Williamson Hall 2.48 3rd person 321 Maag Library 1.52 /* //SYSUT2 DD SYSOUT=* // Empty dataset check: If dataset to be checked is empty then RC=4 else 0. //IEBPTPCH JOB // EXEC PGM=IEBPTPCH //SYSUT1 DD DSN=<filename>,DISP=SHR //SYSUT2 DD DUMMY, // DCB=(BLKSIZE=<block size>,RECFM=FA) //SYSIN DD * PRINT TYPORG=PS /* //SYSPRINT DD SYSOUT=* // IEBTCRIN Read records from a 2495 Tape Cartridge Reader. IEBUPDAT Changes records in a sequential dataset or in a member of a partitioned dataset, replaced by, but not compatible with, IEBUPDTE. IEBUPDTE IEBUPDTE ("UPDaTE") incorporates changes to sequential or partitioned datasets. The UNIX patch utility is a similar program, but uses different input format markers (e..g, "./ INSERT ..." in MVS becomes "@@..." in Unix Patch). Some programmers pronounce it "I.E.B. up-ditty". The IEBUPDTE utility is used to maintain source libraries. Some of the functions that IEBUPDTE can perform include the following: Creating and updating libraries Modifying sequential data sets or PDS members Changing the organization of a data set from sequential to partitioned or from partitioned to sequential. IEBUPDTE is commonly used to distribute source libraries from tape to DASD. IEBUPDTE uses the same job control statements required by most IEB-type utilities. The only exceptions are as follow: IEBUPDTE accepts a PARM parameter coded on the EXEC statement, NEW or MOD. NEW indicates that the utility control statements and the input data are contained in the SYSIN DD statement, so no SYSUT1 DD statement is needed. MOD indicates that the SYSIN DD statement contains only utility control statements, without input data. Therefore, the SYSUT1 DD statement is required to define the input data set. IEBUPDTE reads the input data set from either the SYSUT1 DD statement or from the SYSIN DD statement. The job control used by IEUPDTE are as follows: //stepname EXEC PGM=IEUPDTE,PARM=NEW //SYSPRINT DD SYSOUT=class //SYSUT1 DD ... //SYSUT2 DD ... //SYSIN DD ... Scheduler utilities IEFBR14 IEFBR14 is a dummy program, normally inserted in JCL when the only desired action is allocation or deletion of datasets. An example of an IEFBR14 step: //IEFBR14 JOB ACCT,'DELETE DATASET' //STEP01 EXEC PGM=IEFBR14 //DELDD DD DSN=xxxxx.yyyyy.zzzzz, // DISP=(MOD,DELETE,DELETE),UNIT=DASD The calling sequence for OS/360 contained the return address in Register 14. A branch to Register 14 would thus immediately exit the program. However, before and after executing this program, the operating system would allocate & deallocate datasets as specified in the DD statements, so it is commonly used as a quick way to set up or remove datasets. It consisted initially as a single instruction a "Branch to Register" 14. The mnemonic used in the IBM Assembler was BR and hence the name: IEF BR 14. IEF is, of course, the "prefix" of OS/360's "job management" subsystem. This single instruction program had an error in it — it didn't set the return code. Hence a second instruction had to be added to clear the return code so that it would exit with the correct status. There was an additional error reported and fixed by IBM on this now two instruction program. This error was due to the IEFBR14 program not being link-edited as reenterable (simultaneously usable by more than one caller). Some hackers have taken IEFBR14 and changed the BR 14 instruction to BR 15, thereby creating "the shortest loop in the world", as register 15 contains the address of the IEFBR14 module itself, and a BR 15 instruction would simply re-invoke the module, forever. System utilities These utilities are normally used by systems programmers in maintaining the operation of the system, rather than by programmers in doing application work on the system. ICKDSF ICKDSF ("Device Support Facility") installs, initializes and maintains DASD, either under an operating system, or standalone. IEHATLAS Assign alternate tracks to defective tracks. IEHDASDR IEHDASDR can performs several operations for direct access storage devices (DASD) Initialize a DASD volume, with optional surface checking Assign alternate tracks to defective tracks Print tracks on a DASD Create a backup of a DASD volume on tape Restore DASD volumes from backup tapes. IBM eventually stopped adding support for new device types to IEHDASDR and directed customers to the free DSF for initializing volumes and to the chargeable DASDR (5740-UT1) and Data Facility/Data Set Services (5740-UT3, DF/DSS) for dump/restore. IBM removed IEHDASDR in MVS/XA. IEHINITT IEHINITT ("INITialize Tape") initializes tapes by writing tape labels. Multiple tapes may be labeled in one run of the utility. IBM standard or ASCII labels may be written. An example of an IEHINITT program: //IEHINITT JOB ACCT,'LABEL TAPES',MSGCLASS=J,CLASS=A //STEP0001 EXEC PGM=IEHINITT,REGION=8M //SYSPRINT DD SYSOUT=A //LABEL DD DCB=DEN=2,UNIT=(3490,1,DEFER) //SYSIN DD * LABEL INITT SER=123450,NUMBTAPE=3 /* This example will label 3 tapes on a 3490 magnetic tape unit. Each tape will receive an IBM standard label. The VOLSER will be incremented by one for each tape labeled. Each tape will be rewound and unloaded after being labeled. IEHIOSUP Update TTR links for type IV Supervisor Call (SVC) routines in SYS1.SVCLIB. Not applicable to OS/VS2 or later. IEHLIST IEHLIST is a utility used to list entries in a Partitioned Dataset (PDS) directory or to list the contents of a Volume Table of Contents (VTOC). The IEHLIST utility is used to list the entries contained in any one of the following: PDS directory VTOC Catalog (OS CVOL) An example of an IEHLIST program: //IEHLIST JOB ACCT,'LIST PDS',MSGCLASS=J,CLASS=A //STEP0001 EXEC PGM=IEHLIST,REGION=8M //SYSPRINT DD SYSOUT=A //PDS1 DD DSN=xxxx.yyyy.zzzz,DISP=OLD //SYSIN DD * LISTPDS DSNAME=xxxx.yyyy.zzzz,FORMAT /* This job will produce a formatted listing of the PDS directory of the PDS named xxxx.yyyy.zzzz. An example of an IEHLIST program to list a VTOC is very similar: //IEHLIST JOB ACCT,'LIST VTOC',MSGCLASS=J,CLASS=A //STEP0001 EXEC PGM=IEHLIST,REGION=8M //SYSPRINT DD SYSOUT=A //VOL1 DD VOL=SER=vvvvvv,DISP=OLD //SYSIN DD * LISTVTOC VOL=SER=vvvvvv,FORMAT /* IEHMOVE IEHMOVE moves or copies collections of data. However, DFSMS (System Managed Storage) environments are now common, and IBM does not recommend using the IEHMOVE utility in those. A move differs from a copy in that following a move the original data set is deleted, or scratched. Some of the tasks that IEHMOVE can perform include the following: Moving or copying sequential and partitioned data sets Moving or copying multi- volume data sets Moving an entire volume of data sets On the surface, IEHMOVE may seen redundant to the IEBGENER and IEBCOPY utilities. However, IEHMOVE is more powerful. The main advantage of using IEHMOVE is that you do not need to specify space or DCB information for the new data sets. This is because IEHMOVE allocates this information based on the existing data sets. Another advantage of IEHMOVE is that you can copy or move groups of data sets as well as entire volumes of data. Because of the ease in moving groups of data sets or volumes, the IEHMOVE utility is generally favored by systems programmers. A sample IEHMOVE job: //stepname EXEC PGM=IEHMOVE,PARM='LINECNT=xx,POWER=n' //SYSPRINT DD SYSOUT=class //SYSUT1 DD UNIT=aaaa,VOL=SER=bbbbbb,DISP=OLD //anyname1 DD UNIT=cccc,VOL=SER=dddddd,DISP=OLD //anyname2 DD UNIT=eeee,VOL=SER=ffffff,DISP=OLD //SYSIN DD ... The DD statements for IEHMOVE, other than SYSPRINT and SYSIN, refer to DASD or magnetic tape volumes instead of individual data sets. However, referencing volumes can pose a problem, since specifying DISP=OLD gains exclusive access to a volume. Therefore, while your IEHMOVE job runs, that entire volume (and all datasets on it) is unavailable to other users. This is acceptable for private volumes, such as tape or mountable DASD volumes, but unacceptable public volumes. The SYSUT1 DD statement specifies a DASD volume where three work data set required by IEHMOVE are allocated. You must specify unit and volume information for this DD statement. IEHMOVE was one of the first systems to be developed in PL/S. In this example, three sequential data sets (SEQSET1, SEQSET2, and SEQSET3) are moved from one disk volume to three separate disk volumes. Each of the three receiving volumes is mounted when it is required by IEHMOVE. The source data sets are not cataloged. Space is allocated by IEHMOVE. //MOVEDS JOB ... //STEP1 EXEC PGM=IEHMOVE //SYSPRINT DD SYSOUT=A //SYSUT1 DD UNIT=disk,VOLUME=SER=333333,DISP=OLD //DD1 DD UNIT=(disk,,DEFER),DISP=OLD, // VOLUME=(PRIVATE,,SER=(222222)) //DD2 DD UNIT=(disk,,DEFER),DISP=OLD, // VOLUME=(PRIVATE,,SER=(222333)) //DD3 DD UNIT=(disk,,DEFER),DISP=OLD, // VOLUME=(PRIVATE,,SER=(222444)) //DD4 DD VOLUME=(PRIVATE,RETAIN,SER=(444444)), // UNIT=disk,DISP=OLD //SYSIN DD * MOVE DSNAME=SEQSET1,TO=disk=222222,FROM=disk=444444 MOVE DSNAME=SEQSET2,TO=disk=222333,FROM=disk=444444 MOVE DSNAME=SEQSET3,TO=disk=222444,FROM=disk=444444 /* IEHPROGM IEHPROGM builds and maintains system control data. It is also used for renaming and scratching (deleting) a data set. Some of the tasks that IEHPROGM can perform include the following: Deleting (scratching) a data set or PDS member Renaming a data set or PDS member Cataloging or uncataloging a data set Maintaining data set passwords in the system PASSWORD dataset For cataloging: //SYSIN DD * CATLG DSNNAME=data-set-name, VOL=device-name=volume-number /* // IFHSTATR Select and format SMF records for tape errors. Independent Utilities These programs do not run under the control of an operating system IBCDASD Format direct access volumes and assign alternate tracks. IBCDMPRS Dump and restore direct access volumes. IBCRCVRP Assign alternate tracks, recover and replace data. ICAPRTBL Load Forms Control Buffer (FCB) and Universal Character Set (UCS) buffer on printer. Service Aids These are utility program that IBM documents in service aids or diagnosis manuals. The original OS/360 Service aids had names beginning with IFC and IM*, but IBM changed the naming convention to HM* for OS/VS1 and to AM* for OS/VS2. IBM did not change the IFC convention. IFCDIP00 Initializes the SYS1.LOGREC data set. IFCEREP0 Summarizes and prints records from the SYS1.LOGREC error recording data set. GTF (Generalized Trace Facility) Traces selected system events such as SVC and I/O interruptions. IMAPTFLE Generates JCL needed to apply to a PTF and/or applies the PTF. The functions of this program have been subsumed by SMP. IMASPZAP Verifies and/or replaces instructions and/or data in a load module or program object IMBLIST Formats and prints object modules, load modules, program objects and CSECT identification records. IMBMDMAP Maps load modules. The functions of this program have been subsumed by IMBLIST. IMCJQDMP Stand-alone program to format and print the system job queue. Not applicable to MVS. IMCOSJQD Format and print the system job queue. Not applicable to MVS. IMDPRDMP Formats and prints dumps, TSO swap data set, and GTF trace data. IMDSADMP Stand-alone program to produce a high-speed or low-speed dump of main storage. Miscellaneous supporting programs SORT The Sort/Merge utility is a program which sorts records in a file into a specified order, or merge pre-sorted files. It is very frequently used; often the most commonly used application program in a mainframe shop. Modern sort/merge programs also can select or omit certain records, summarize records, remove duplicates, reformat records, and produce simple reports. Sort/merge is important enough that there are multiple companies each selling their own sort/merge package for IBM mainframes. IBM's original OS/360 sort/merge program, 360S-SM-023, program name IERRCO00 (alias SORT), supported only IBM's first-generation direct-access storage devices (DASD) and tapes (2400). Support for second-generation disk drives was provided by IBM program products such as 5734-SM1 and the later 5740-SM1 (DFSORT, alias ICEMAN, also SORT). SORT is frequently executed as a stand-alone program, where it normally reads input from a file identified by DD SORTIN and writes sorted output to a file identified by DD SORTOUT. It is also often called from another application, via the COBOL SORT verb or calls to PL/I PLISRTx routines, where it may use either SORTIN or SORTOUT files or be passed records to be sorted by the caller and/or pass sorted records back to the caller one at a time. The operation of SORT is directed by control statements, which are largely compatible among various IBM and third-party sort programs. The SORT or MERGE statement defines the sort keys— the fields on which the data is to be sorted or merged. This statement identifies the position, length, and data type of each key. The RECORD statement describes the format and length of the records in the input file. Other statements allow the user to specify which records should be included or excluded from the sort and specify other transformations to be performed on the data. Keys can be any combination of EBCDIC or ASCII character data, zoned or packed-decimal, signed or unsigned fixed-point binary, or hexadecimal floating-point. Keys can be located anywhere in the record and do not have to be contiguous. Sorting can be specified on any combination of ascending and descending sequence by key. The OS/360 sort program, IERRCO00, operates by dividing the input data into sections, sorting each section in main memory, and writing the sorted section to intermediate datasets on either direct-access storage devices (DASD) or magnetic tape. Final merge phases then merge the sections to produce the sorted output. SORT uses one of a number of techniques for distributing the sections among secondary storage devices. Usually SORT can choose the optimal technique, but this can be overridden by the user. SORT has three techniques that can be used if the intermediate storage is tape, and two if disk. The tape techniques are: Balanced (BALN) - more efficient if more tape drives are available for intermediate storage. Polyphase (POLY) - used if fewer tape drives are available for intermediate storage. Oscillating (OSCL) - uses more main storage. The size of the input dataset must be known or closely approximated. The disk techniques are: Balanced Direct Access (BALN) - uses three to six intermediate storage datasets. Crisscross Direct Access (CRCX) - uses six to seventeen intermediate storage datasets, requires twice the main storage of the Balanced Direct Access technique. Linkers OS/360 had only the Linkage editor, available in several configurations. DFSMSdfp added the Binder as an alternatives for load modules, and as the only option for program objects. Linkage Editor The Linkage editor creates and replaces load modules in a partitioned data set from a combination of control cards, object modules other load modules. It can rename or replace a control section (CSECT) and perform several other miscellaneous functions. It was originally available in several configurations depending on storage requirement, but the E level Linkage Editor is no longer available and the F level Linkage Editor is now known simply as the Linkage Editor. In z/OS the Linkage Editor is only present for compatibility. Binder The binder performs the same functions as the Linkage Editor. In addition, it supports a new format, the program object, which is the functional equivalent of a load module in Partitioned Data Set Extended (PDSE), with many additional capabilities. Compilers Each programming language used in a computer shop will have one or more associated compilers that translate a source program into a machine-language object module. Then the object module from the compiler must be processed by the linkage editor, IEWL, to create an executable load module. IGYCRCTL is a common example of a compiler; it is the compiler for the current IBM Enterprise COBOL for z/OS product. (There have been several previous IBM COBOL compilers over the years, with different names.) There are many other compilers for various other programming languages. IETASM Assembler (E) was intended for OS/360 running in very small machines. IEUASM Assembler (F) was intended for normal OS/360 installations. IFOX00 Assembler (XF) was the system assembler for OS/VS1 and OS/VS2, replacing Assembler (E) and (F), although it was not fully compatible with them. IBM soon made Assembler (XF) the system assembler for DOS and VM as well. IEV90 Assembler (H) and Assembler (H) Version 2 are program product assemblers that are generally faster than Assemblers E, F, and XF, although not fully compatible with any of them. ASMA90 IBM High Level Assembler (HLASM) is essentially a new version of Assembler (H) Version 2 and is the only assembler that IBM supports on z/OS and z/VM. It replaces all of the older assemblers, although it is not fully compatible with them. System Modification Program (SMP) System Modification Program (SMP) is the vehicle for installing service on OS/360 and successors, replacing, e.g., stand-alone assembly, link edit and IMAPTFLE jobs. Originally an optional facility, it is mandatory for MVS/SP and later, and the program product version, SMP/E, is included in the more recent systems, e.g., z/OS. Notes References See also Syncsort Easytrieve External links DFSMSdfp Utilities DFSMS Access Method Services for Catalogs DFSMSdss Storage Administration Guide MVS UTILITIES Mainframe utility programs Utility software

Operating System (OS)

Operational technology Operational Technology (OT) is hardware and software that detects or causes a change, through the direct monitoring and/or control of industrial equipment, assets, processes and events. The term has become established to demonstrate the technological and functional differences between traditional IT systems and Industrial Control Systems environment, the so-called "IT in the non-carpeted areas". Examples of operational technology include: programmable logic controllers (PLCs) Supervisory control and data acquisition systems (SCADA) Distributed control systems (DCS) Computer Numerical Control (CNC) systems, including computerized machine tools Scientific equipment (e.g. digital oscilloscopes) Building Management and Building Automation Systems, (BMS)/(BAS) Lighting controls both for internal and external applications Energy monitoring, security and safety systems for the built environment Transportation systems for the built environment Technology Usually environments containing Industrial Control Systems (ICS), such as supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), Remote terminal units (RTU) and programmable logic controllers (PLC), as well as dedicated networks and organization units. The built environment, whether commercial or domestic, is increasingly controlled and monitored via 10's, 100's, and 1,000s of Internet of Things (IoT) devices. In this application space, these IoT devices are both interconnected via converged technology edge IoT platforms and or via "cloud" based applications. Embedded Systems are also included in the sphere of operational technology (e.g. SMART instrumentation), along with a large subset of scientific data acquisition, control, and computing devices. An OT device could be as small as the ECU of a car or as large as the distributed control network for a national electricity grid. Systems Systems that process operational data (including electronic, telecommunications, computer systems and technical components) are included under the term operational technology. OT systems can be required to control valves, engines, conveyors and other machines to regulate various process values, such as temperature, pressure, flow, and to monitor them to prevent hazardous conditions. OT systems use various technologies for hardware design and communications protocols, that are unknown in IT. Common problems include supporting legacy systems & devices and numerous vendor architectures and standards. Since OT systems often supervise industrial processes, most of the time availability must be sustained. This often means that real time (or near-real time) processing is required, with high rates of reliability and availability. Laboratory systems (heterogenous Instruments with embedded computer systems or often non standardized technical components used in their computer systems) are commonly a borderline case between IT and OT since they mostly clearly don't fit into standard IT scope but also are often not part of OT core definitions. This kind of environment may also be referred to as Industrial Information Technology (IIT). Protocols Historical OT networks utilized proprietary protocols optimized for the required functions, some of which have become adopted as 'standard' industrial communications protocols (e.g. DNP3, Modbus, Profibus, LonWorks, DALI, BACnet, KNX, EnOcean). More recently IT-standard network protocols are being implemented in OT devices and systems to reduce complexity and increase compatibility with more traditional IT hardware (e.g. TCP/IP); this however has had a demonstrable reduction in security for OT systems, which in the past have relied on air gaps and the inability to run PC-based malware (see Stuxnet for a well-known example of this change) Origins The term Operational Technology as applied to industrial control systems was first published in a research paper from Gartner in May 2006 (Steenstrup, Sumic, Spiers, Williams) and presented publicly in September 2006 at the Gartner Energy and Utilities IT Summit. Initially the term was applied to power utility control systems, but over time was adopted by other industrial sectors and used in combination with IoT. A principal driver of the adoption of the term was that the nature of operational technology platforms had evolved from bespoke proprietary systems to complex software portfolios that rely on IT infrastructure. This change was termed IT OT convergence. The concept of aligning and integrating the IT and OT systems of industrial companies gained importance as companies realized that physical assets and infrastructure was both managed by OT systems but also generated data for the IT systems running the business. In May 2009 a paper was presented at the 4th World Congress on Engineering Asset Management Athens, Greece outlining the importance of this in the area of asset management Industrial technology companies such as GE, Hitachi, Honeywell, Siemens, ABB and Rockwell are the main providers of OT platforms and systems either embedded in equipment or added to them for control, management and monitoring. These industrial technology companies have needed to evolve into software companies rather than being strictly machine providers. This change impacts their business models which are still evolving Security From the very beginning security of Operational Technology has relied almost entirely on the standalone nature of OT installations, security by obscurity. At least since 2005 OT systems have become linked to IT systems with the corporate goal of widening an organization's ability to monitor and adjust its OT systems, which has introduced massive challenges in securing them. Approaches known from regular IT are usually replaced or redesigned to align with the OT environment. OT has different priorities and a different infrastructure to protect when compared with IT; typically IT systems are designed around 'Confidentiality, Integrity, Availability' (i.e. keep information safe and correct before allowing a user to access it) whereas OT systems require 'Realtime control and functionality change flexibility, Availability, Integrity, Confidentiality' to operate effectively (i.e. present the user with information wherever possible and worry about correctness or confidentiality after). Other challenges affecting the security of OT systems include: OT components are often built without basic IT security requirements being factored in, aiming instead at achieving functional goals. These components may be insecure by design and vulnerable to cyber-attacks. Vendor dependency: Due to the general lack of knowledge related to industrial automation, most companies are heavily dependent on their OT vendors. This leads to vendor lock-in, eroding the ability to implement security fixes. Critical Assets: Because of OT's role in monitoring and controlling critical industrial process, OT systems are very often part of National Critical Infrastructure. As such they may require enhanced security features as a result. Critical Infrastructure Operational Technology is widely used in refineries, power plants, nuclear plants, etc. and as such has become a common, crucial element of critical infrastructure systems. Depending on the country there are increasing legal obligations for Critical Infrastructure operators with regards to the implementation of OT systems. In addition certainly since 2000, 100,000's of buildings have had IoT building management, automation and smart lighting control solutions fitted These solutions have either no proper security or very inadequate security capabilities either designed in or applied. This has recently led to bad actors exploiting such solutions' vulnerabilities with ransomware attacks causing system lock outs, operational failures exposing businesses operating in such buildings to the immense risks to health and safety, operations, brand reputation and financial damage Governance There is a strong focus put on subjects like IT/OT cooperation or IT/OT alignment in the modern industrial setting. It is crucial for the companies to build close cooperation between IT and OT departments, resulting in increased effectiveness in many areas of OT and IT systems alike (such as change management, incident management and security standards) A typical restriction is the refusal to allow OT systems to perform safety functions (particularly in the nuclear environment), instead relying on hard-wired control systems to perform such functions; this decision stems from the widely recognized issue with substantiating software (e.g. code may perform marginally differently once compiled). The Stuxnet malware is one example of this, highlighting the potential for disaster should a safety system become infected with malware (whether targeted at that system or accidentally infected). Sectors Operational Technology is utilized in many sectors and environments, such as: Oil & Gas Power and Utilities Chemicals manufacturing Water treatment Waste management Transportation Scientific experimentation Critical Manufacturing Building Management and Automation Building lighting controls and automation References PCBA manufacturer Control engineering

Operating System (OS)

Yellow Dog Linux Yellow Dog Linux (YDL) is a discontinued free and open-source operating system for high-performance computing on multi-core processor computer architectures, focusing on GPU systems and computers using the POWER7 processor. The original developer was Terra Soft Solutions, which was acquired by Fixstars in October 2008. Yellow Dog Linux was first released in the spring of 1999 for Apple Macintosh PowerPC-based computers. The most recent version, Yellow Dog Linux 7, was released on August 6, 2012. Yellow Dog Linux lent its name to the popular YUM Linux software updater, derived from YDL's YUP (Yellowdog UPdater) and thus called Yellowdog Updater, Modified. Features Yellow Dog Linux is based on Red Hat Enterprise Linux/CentOS and relies on the RPM Package Manager. Its software includes applications such as Ekiga (a voice-over-IP and videoconferencing application), GIMP (a raster graphics editor), Gnash (a free Adobe Flash player), gThumb (an image viewer), the Mozilla Firefox Web browser, the Mozilla Thunderbird e-mail and news client, the OpenOffice.org productivity suite, Pidgin (an instant messaging and IRC client), the Rhythmbox music player, and the KDE Noatun and Totem media players. Starting with YDL version 5.0 'Phoenix', Enlightenment is the Yellow Dog Linux default desktop environment, although GNOME and KDE are also included. Like other Linux distributions, Yellow Dog Linux supports software development with GCC (compiled with support for C, C++, Java, and Fortran), the GNU C Library, GDB, GLib, the GTK+ toolkit, Python, the Qt toolkit, Ruby and Tcl. Standard text editors such as Vim and Emacs are complemented with IDEs such as Eclipse and KDevelop, as well as by graphical debuggers such as KDbg. Standard document preparation tools such as TeX and LaTeX are also included. Yellow Dog Linux includes software for running a Web server (such as Apache/httpd, Perl, and PHP), database server (such as MySQL and PostgreSQL), and network server (NFS and Webmin). Additional software is also included for running an enterprise server or a compute server or cluster, although two separate products from Terra Soft Solutions, called Yellow Dog Enterprise Linux (for enterprise servers) and Y-HPC (for compute servers/clusters), were specifically targeted toward those applications. Although several other Linux distributions support the Power ISA, Yellow Dog Linux was distinguished for its focus on supporting the Apple Macintosh platform before the Mac transition to Intel processors. Before this transition, Terra Soft Solutions held the unique distinction of being the only company licensed by Apple to resell Apple computers with Linux pre-installed (or for that matter, with any operating system other than Mac OS X). Full support for AirPort (Apple's implementation of the IEEE 802.11b-1999 wireless networking standard), and partial support for AirPort Extreme, are also built into Yellow Dog Linux, as are support for Bluetooth and support for accessing the Internet over cellular phones. Following the Mac transition to Intel processors, Yellow Dog Linux retargeted Fedora Core 5.0 and later to support the Sony PlayStation 3 and IBM pSeries platforms extensively, while retaining its longstanding support for PowerPC-based Apple hardware. Distribution Yellow Dog Linux was sold by Terra Soft Solutions (later Fixstars), who also marketed PlayStation 3 consoles, IBM workstations, and servers with Yellow Dog Linux pre-installed. As is the case with most other Linux distribution vendors, a portion of the revenue from the sale of those boxed distributions went toward development of the operating system and applications, which are made available as source code under various free and open-source licenses. Notable implementations Gaurav Khanna, a professor in the Physics Department at the University of Massachusetts, Dartmouth, built a message-passing based cluster using YDL and 16 PlayStation 3s. This cluster was the first such to generate published scientific results. Dubbed the "PS3 Gravity Grid", it performs astrophysical simulations of large supermassive black holes capturing smaller compact objects. Khanna claims that the cluster's performance exceeds that of a 100+ Intel Xeon core based traditional Linux cluster on his simulations. The PS3 Gravity Grid gathered significant media attention through 2007, 2008, 2009 and 2010. Release history References External links Yellow Dog Linux on PS3 Yellow Dog Linux home page penguinppc.org – Linux on PowerPC site Yellow Dog Linux archive Reviews "Software Review: Yellow Dog Linux 5 for PlayStation 3" – BlogCritics Magazine review of YDL version 5.0 "Yellow Dog Linux 5.0 Hands-on" – IGN.com review of YDL version 5.0 "Yellow Dog Linux 4.0: Some Install Notes" – ppcnerds.org review of YDL version 4.0 Cell BE architecture Discontinued Linux distributions Platform-specific Linux distributions PlayStation 3 software PowerPC operating systems Linux distributions

Operating System (OS)

LOCUS LOCUS is a discontinued distributed operating system developed at UCLA during the 1980s. It was notable for providing an early implementation of the single-system image idea, where a cluster of machines appeared to be one larger machine. A desire to commercialize the technologies developed for LOCUS inspired the creation of the Locus Computing Corporation which went on to include ideas from LOCUS in various products, including OSF/1 AD and, finally, the SCO–Tandem UnixWare NonStop Clusters product. Description The LOCUS system was created at UCLA between 1980 and 1983, initial implementation was on a cluster of PDP-11/45s using 1 and 10 megabit ring networks, by 1983 the system was running on 17 VAX-11/750s using a 10 megabit Ethernet. The system was Unix compatible and provided both a single root view of the file system and a unified process space across all nodes. The development of LOCUS was supported by an ARPA research contract, DSS-MDA-903-82-C-0189. File system In order to allow reliable and rapid access to the cluster wide filesystem LOCUS used replication, the data of files could be stored on more than one node and LOCUS would keep the various copies up to date. This provided particularly good access times for files that were read more often than they were written, the normal case for directories for example. In order to ensure that all access was made to the most recent version of any file LOCUS would nominate one node as the "current synchronization site" (CSS) for a particular file system. All accesses to files a file system would need to be coordinated with the appropriate CSS. Node dependent files As with other SSI systems LOCUS sometimes found it necessary to break the illusion of a single system, notably to allow some files to be different on a per-node basis. For example, it was possible to build a LOCUS cluster containing both PDP-11/45 and VAX 750 machines, but instruction sets used were not identical, so two versions of each object program would be needed The solution was to replace the files that needed to be different on a per node basis by special hidden directories. These directories would then contain the different versions of the file. When a user accessed one of these hidden directories the system would check the user's context and open the appropriate file. For example, if the user was running on one of the PDP-11/45's and typed the command /bin/who then the system would find that /bin/who was actually a hidden directory and run the command /bin/who/45. Another user on a VAX node who typed /bin/who would run the command /bin/who/vax. Devices LOCUS provided remote access to I/O devices. Processes LOCUS provided a single process space. Processes could be created on any node on the system. Both the Unix fork and exec calls would examine an advice list which determined on which node the process would be run. LOCUS was designed to work with heterogeneous nodes, (e.g., a mix of VAX 750s and PDP 11/45s) and could decide to execute a process on a different node if it needed a particular instruction set. As an optimization a run call was added which was equivalent to a combined fork and exec, thus avoiding the overhead of copying the process memory image to another node before overwriting it by the new image. Pipes Processes could use pipes for inter node communication, including named pipes, Partitioning The LOCUS system was designed to be able to cope with network partitioning - one or more nodes becoming disconnected from the rest of the system. As the file system was replicated the disconnected nodes could continue to access files. When the nodes were reconnected any files modified by the disconnected nodes would be merged back into the system. For some file types (for example mailboxes) the system would perform the merge automatically, for others the user would be informed (by mail) and tools were provided to allow access to the different versions of the file. Notes References Proprietary operating systems Cluster computing Distributed operating systems

Operating System (OS)

ONOS The ONOS (Open Network Operating System) project is an open source community hosted by The Linux Foundation. The goal of the project is to create a software-defined networking (SDN) operating system for communications service providers that is designed for scalability, high performance and high availability. History On December 5, 2014, the Open Networking Lab (ON.Lab) along with other industry partners including AT&T and NTT Communications released the ONOS source code to start the open source community. On October 14, 2015, the Linux Foundation announced that ONOS had joined the organization as one of its collaborative projects. The project was started around October 2012 under the leadership of Pankaj Berde, an architect at ON.Lab. The name ONOS was coined around end of 2012 by Berde. Early prototype was shown on April, 2013 at Open Networking Summit (ONS) and journey of initial iterations featured at ONS 2014. Technology overview The software is written in Java and provides a distributed SDN applications platform atop Apache Karaf OSGi container. The system is designed to operate as a cluster of nodes that are identical in terms of their software stack and can withstand failure of individual nodes without causing disruptions in its ability to control the network operation. While ONOS leans heavily on standard protocols and models, e.g. OpenFlow, NETCONF, OpenConfig, its system architecture is not directly tied to them. Instead, ONOS provides its own set of high-level abstractions and models, which it exposes to the application programmers. These models can be extended by the applications at run-time. To prevent the system from becoming tied to a specific configuration or control protocol, any software in direct contact with protocol-specific libraries and engaging in direct interactions with network environment is deliberately isolated into its own tier referred to as a provider or a driver. Likewise, any software in direct contact with intra-cluster communication protocols is deliberately isolated into its own tier referred to as a store. The platform provides applications with a number of high-level abstractions, through which the applications can learn about the state of the network and through which they can control the flow of traffic through the network. The network graph abstraction provides information about the structure and topology of the network. The flow objective is a device-centric abstraction that allows applications to direct flow of traffic through a specific device without the need to be aware of the device table pipeline. Similarly, the intent is a network-centric abstraction that gives application programmers the ability to control network by specifying what they wish to accomplish rather than specifying how they want to accomplish it. This simplifies application development and at the same time provides the platform with added degrees of freedom to resolve what would normally be considered conflicting requests. Applications (core extensions) can be loaded and unloaded dynamically, via REST API or GUI, and without the need to restart the cluster or its individual nodes. ONOS application management subsystem assumes the responsibility for distributing the application artifacts throughout the cluster to assure that all nodes are running the same application software. ONOS base distribution contains over 175 applications, which fall into numerous categories, e.g. traffic steering apps, device drivers, ready-to-use YANG models, utilities, monitoring apps. The system provides REST API, CLI and an extensible, dynamic web-based GUI. gRPC interfaces for ONOS are under active development. Use cases The ONOS software has been used as a platform that applications have been written on top of or has been integrated into other projects. A number of use cases demonstrate how the software is being used today—including global research networking deployments, multilayer network control, and central office re-designed as a datacenter. Releases The following lists the different ONOS releases that are all named after different types of birds in alphabetical order: Members There are two tiers of membership for ONOS: Partner and Collaborator, with varying levels of commitment. Partners AT&T China Unicom Ciena Cisco Comcast Deutsche Telekom Ericsson Fujitsu Google Huawei Intel NEC Nokia NTT Communications Radisys Samsung Electronics Türk Telekom Verizon Collaborators AARNET ADARA Networks Airhop Communications Akamai AmLight BlackDuck BTI Systems Beijing University of Posts and Telecommunications Cavium ClearPath Networks CNIT CREATE-NET Criterion Networks CSIRO ECI Telecom ETRI Consortium GARR GEANT Happiest Minds Internet2 INSPIRE group KAIST KREONET KISTI NAIM Networks NetCracker OpenFlow Korea OPLink Communications Open Networking Foundation Postech SRI International National Chiao-Tung University See also List of SDN controller software References External links Computer networking Linux Foundation projects

Operating System (OS)

LineageOS LineageOS is an operating system for smartphones, tablet computers, and set-top boxes, based on Android with mostly free and open-source software. It is the successor to the custom ROM CyanogenMod, from which it was forked in December 2016 when Cyanogen Inc. announced it was discontinuing development and shut down the infrastructure behind the project. Since Cyanogen Inc. retained the rights to the Cyanogen name, the project rebranded its fork as LineageOS. LineageOS was officially launched on 24 December 2016, with the source code available on both GitHub and GitLab. As with all versions of Android, operating system releases are specific to a single device model. Since its launch, LineageOS development builds are available for 109 phone models with over 2.8 million active installs, having doubled its user base in the months February–March 2017. Background CyanogenMod (often abbreviated "CM") was a popular open-source operating system for smartphones and tablet computers, based on the Android mobile platform. Although only a subset of total CyanogenMod users elected to report their use of the firmware, as of 23 March 2015, some reports indicated over 50 million people running CyanogenMod on their phones. In 2013, the founder, Stefanie Kondik, obtained venture funding under the name Cyanogen Inc. to allow commercialization of the project. In her view, the company did not capitalize on the project's success and in 2016 she either left or was forced out as part of a corporate restructure which involved a change of CEO, closure of offices and projects, and cessation of services. The code itself, being both open source and popular, was quickly forked under the new name LineageOS and efforts began to resume development as a community project. CyanogenMod offered a number of features and options not available in the official firmware distributed by most mobile device vendors. Features supported by CyanogenMod included native theme support, FLAC audio codec support, a large Access Point Name list, Privacy Guard (per-application permission management application), support for tethering over common interfaces, CPU overclocking, root access, soft buttons and other "tablet tweaks," toggles in the notification pull-down (such as Wi-Fi, Bluetooth and satellite navigation), and other interface and performance enhancements. Many of the features from CyanogenMod were later integrated into the official Android code base. CyanogenMod's developers said that it did not contain spyware or bloatware. CyanogenMod was also said to perform better and be more reliable than official firmware releases. Development Like CyanogenMod, the LineageOS project is developed by many device-specific maintainers and uses Gerrit for its code review process. It also retained the old versioning format (for example, Android 7.1 is LineageOS 14.1). Prior to the official launch of LineageOS, many developers from XDA had already developed unofficial versions of LineageOS from the source code. On 22 January 2017, the first 14.1 and 13.0 official builds started to be made available, following the official announcement in a blog post. On 11 February 2018, the 13.0 builds were stopped, while the source code remains available and security fixes are still accepted on Gerrit. On 26 February 2018, the first 15.1 official builds started to be available on certain devices, following official announcement in a blog post. The 14.1 versions of Lineage OS were to remain in active development, but without feature advancements. On 24 February 2019, the 14.1 builds were stopped and 15.1 builds moved to a weekly cadence On 1 March 2019, the first 16.0 official builds started to be available, following official announcement. The 15.1 branch remained in active development, but without feature advancements. On 28 February 2020, the 15.1 builds were stopped in preparation for the 17.1 release. On 1 April 2020, the first 17.1 builds were made available, following official announcement. The 16.0 builds are moved to a weekly cadence while the branch remains in active development, but without feature advancements. On 1 April 2021, the first 18.1 builds were made available, following official announcement. The 17.1 branch remains in active development, but without feature advancements. All the released builds are signed with LineageOS' private keys. Builds were released on a weekly basis until 12 November 2018, when the release cycle for devices has changed: the latest LineageOS branch is built daily, with devices receiving a "nightly" OTA update, while devices on the older branch were moved to a weekly release cycle. Community LineageOS allows the community to get involved with development in various ways. Gerrit is used for the code review process for both the operating system and the infrastructure. The wiki, containing information regarding installation, support, and development of LineageOS, is also open to contributions through Gerrit. Other Lineage platforms include Crowdin for managing translations, Gitlab Issues for bug tracking, and a stats page, which displays the number of active installations from users who opt in to report this statistic. There is also an IRC channel hosted on Libera.chat (#lineageos) and subreddit (r/lineageos). The XDA Developers forums have been used by members of the Lineage community since the software's inception. Many devices are left unsupported by official releases so community members develop their own unofficial ROMs allowing older phones to use Lineage. These unofficial releases are often bundled with software intended to aid the user's experience that would otherwise be unseen in an official release. They also come with known bugs and security issues that may not be seen in official releases. During August 2017 the LineageOS team held a Summer Survey in which they asked users for feedback to improve the development of the operating system. The results were published in October and, according to the team, they used the gathered data to improve the upcoming LineageOS 15 release. A second Summer Survey was conducted in August 2018. As a response to one of the main suggestions received during their first public survey, LineageOS launched a section on their blog titled "LineageOS Engineering Blog" where Lineage maintainers and developers can contribute articles discussing advanced technical information pertaining to Android development. LineageOS is also known for posting a "regularly irregular review" on its blog in which the active development of the work is discussed. Version history Preinstalled apps LineageOS includes many essential and useful apps, but like its predecessor, CyanogenMod, it is free from unnecessary software often pre-installed by a phone's manufacturer or carrier that is considered to be bloatware. Current AudioFX – Audio optimizer with presets to alter the listening experience. Browser – A lightweight browser that relies on the System Webview, for low-end devices, also known as Jelly. Calculator – Resembles a four-function calculator and offers some more advanced functions. Calendar – Calendar functionality with Day, Week, Month, Year or Agenda views. A modified version of Etar starting with version 17.1. Camera – Dependent on device specification will take video or photos, including panoramic. It can also be used to read QR codes. This app is also known as Snap. Clock – World clock, countdown timer, stopwatch and alarms. Contacts – Phonebook for numbers and email addresses. Email – Email client that handles POP3, IMAP and Exchange (removed in version 18.1). Files – A simple file manager to move, copy and rename files on internal storage or SD card. FlipFlap – An app for smart flip covers, only included on select devices. FM Radio – An app for listening to FM radio broadcasts, included on devices with an FM tuner. Gallery – Organize photos and videos into a timeline or albums for easy viewing. Messaging – An MMS/SMS messaging app. Music – A simple music player, also known as Eleven. Phone – Includes speed dial, phone number lookups and call blocking. Recorder – A sound recorder. In versions prior to 18.1 it could also record the screen. Terminal – A simple and standard terminal app. Hidden unless enabled in the developer settings. Trebuchet – A customizable launcher. Former CLock – A weather widget. Gello – A browser based on Chromium and developed by CyanogenMod. This app is now replaced by Jelly. Yahoo Weather Provider – A weather provider. WeatherUnderground Weather Provider – A weather provider. Themes – Originally an app by itself, now integrated into the settings app. Although they are not included in LineageOS as such due to legal issues, users can flash the normal Google apps, including the Google Play Store and Play Apps, with a Zip package, usually referred to as gapps, while installing Lineage OS. A side effect of using LineageOS and other custom roms is the impact on SafetyNet API. App developers can choose to enable a toggle in the app developer console to hide their app on the Play Store if a device doesn't pass SafetyNet tests, or can choose to check the SafetyNet status of a device to disable certain functionality. Notable examples would be Netflix, which is hidden on the Play Store, and Android Pay, which checks SafetyNet each time the app is used. Devices running Lineage may have a smaller selection of usable apps in the Play Store as a result of these checks. Unique features LineageOS offers several features that Android Open Source Project (AOSP) does not include. Some of these features are: Customization features Button customization – Set custom location for buttons on the navigation bar, or enable on-screen buttons for devices with hardware buttons. Custom Quick-Setting tiles – Quick Setting Tiles such as "Caffeine" preventing the device from sleeping, enabling/disabling Heads Up notifications, "Ambient Display" and "ADB over network" are present to easily toggle frequently accessed settings. LiveDisplay – Adjust color temperature for the time of day. Lock screen customization – The lock screen allows all sorts of customizations, including media cover art, a music visualizer, and double-tap to sleep. Styles – Set a global dark or light theme mode and customize accent colors. This functionality can also be managed automatically by the system based on wallpaper or time of day (in line with LiveDisplay). System Profiles – Enable or disable common settings based on the selected profile (For example, a "Home" profile and a "Work" profile). The profile can be selected either manually or through the use of a "trigger", such as upon connecting to a specific WiFi access point, connecting to a Bluetooth device, or tapping an NFC tag. Custom pattern sizes – In addition to Android's 3x3 pattern size, a 4x4, 5x5 or 6x6 size can be used. Security & privacy features PIN scramble – For users securing their device with a PIN, the layout can be scrambled each time the device locks to make it difficult for people to figure out your lock by looking over your shoulder. Privacy guard – Allow the user to fine-tune what permissions are granted to each application. For some permissions, it's possible to set a manual approval each time the permission is requested. It's also possible to find out how often apps use a specific permission. This feature was removed in the 17.1 branch in favor of an equivalent "permission controller" based on a hidden AOSP feature. Protected Apps – Hide specific apps behind a secure lock. This works hand-in-hand with Trebuchet; the app's icon is removed from the launcher, and "secure folders" can be created to easily access these applications. A pattern is used to lock these apps. Some "sensitive numbers", such as abuse support numbers, are not included in the call log for privacy. The phone application also includes a list of helpline numbers for the users to be able to easily reach them. Trust - helps to keep the device secure and protects privacy. Developers & power user features LineageSDK – a set of APIs for app developers to integrate their apps with LineageOS specific features such as System Profiles, Styles and Weather. Lineage Recovery - an AOSP-based recovery. (Optional) Root – Permit apps to function with root access to perform advanced tasks. This requires flashing from Recovery either LineageOS's root add-on (supported until version 16.0) or a third-party implementation such as Magisk or SuperSU. Telephone call recorder, not available in all countries, due to legal restrictions. Weather providers – Display the weather in widgets or apps using a weather provider. This functionality is not included by default; a weather provider must be downloaded from the LineageOS Downloads website. App developers can create both providers and consumers of weather data. Trust interface As LineageOS evolved through development, the Trust interface was introduced for all the LineageOS 15.1 builds released since 12 June 2018. The interface can be found on supported devices under Security and Privacy tab under the Settings option, and enables the user to "get an overview of the status of core security features and explanations on how to act to make sure the device is secure and the data is private". Additionally, while carrying out any action on the device, the trust icon is displayed, notifying the user that the action is safe. Supported devices The number of devices supported by LineageOS has increased over time, with 157 for 17.1 and 18.1 . Official builds on currently supported development branches are labeled as "nightly". For the first two months of the project, parallel experimental builds were also produced, allowing in-place upgrades from previous CyanogenMod installations and easing migration to LineageOS. Criticism and reception 2018 April Fools' prank LineageOS was criticized for a deceptive April Fool's prank included with some April 2018 builds. During the first week of April 2018 LineageOS released new builds with the "LOSGenuine" prank that informed unaware users of the software possibly being counterfeit via a persistent notification (which could not be disabled unless the user ran the following command in a root shell): setprop persist.lineage.nofool true When the notification was tapped, the software claimed that the device was "uncertified" and needed to mine "LOSCoins", which were a virtual currency and could not actually be spent. Affected builds also had a preinstalled "Wallet" app that showed the current balance of LOSCoins. Many users mistook the prank for actual malware, and others reportedly found it to be in "poor taste". It was especially criticized for being too "late" for an April Fool's joke, since many users didn't receive the update until days later, making the jest less obvious. On 10 April 2018, LineageOS team director ciwrl issued an official apology for the deceptive prank. Forks Replicant is a completely free software variant of LineageOS, with all kernel blobs and non-free drivers removed. As a response to the refusal for several reasons of support for signature spoofing in official builds, a LineageOS fork with microG services included, known as "LineageOS for microG", was created. The project ships custom builds of LineageOS with the required patch and native F-Droid support, bundled with the MicroG project's free re-implementation of proprietary Gapps. In other respects it follows upstream, shipping OTA updates every fourteen days. /e/ is a fork of LineageOS created by Gaël Duval that is intended to be "free from Google". It replaces Google Play Services with microG, a free and open-source implementation of Google APIs. See also Android rooting Comparison of mobile operating systems List of custom Android distributions postmarketOS List of free and open-source Android applications References External links 2016 software Android forks Custom Android firmware CyanogenMod Embedded Linux distributions Free mobile software Linux distributions Linux distributions without systemd Software forks

Operating System (OS)

Macintosh 128K/512K technical details The original Macintosh was a relatively simple machine, now of interest for its simplicity and for the fact that it was the first computer produced by Apple under the name Macintosh. The Macintosh used standard off-the-shelf components to the greatest extent possible, achieving a moderate price point by mixing complex LSI chips, readily customizable programmable array logic, and off-the-shelf components. Overall architecture The Macintosh used the Motorola 68000. The 68000's bus was wired directly to the other programmable components of the computer: the IWM floppy controller, the Zilog 8530 SCC, and the MOS Technology 6522. The bus also connected the 68000 to the 128 or 512 KiB of main memory (DRAM), which was shared between the processor and the multimedia circuits in a direct memory access (DMA) arrangement. Either the processor or the video/sound engine could access the memory, but not both, resulting in up to a 10% loss in performance; the DMA circuit also performed necessary maintenance on the RAM which would otherwise add overhead, a trick previously used in the Apple II. Precise timing information was relayed to the 68000 by interrupts. The 68000 provides three interrupt inputs, which in the Macintosh 128K/512K were connected to the 6522, the 8530, and a human input designed for programmers, in order of increasing priority. Thus typing on the keyboard (attached to the 6522) did not reduce serial data (8530) performance, yet the program controlling the serial bus could be debugged by the programmer. To further reduce the cost of manufacture, as compared with its predecessor the Lisa, Apple did not include an MMU. As a result the Macintosh did not support protected memory, and this feature remained absent from the OS until 2001 with the Mac OS X operating system. According to Andy Hertzfeld the Macintosh used for the introduction demo on January 24, 1984 was a prototype with 512k RAM, even though the first model offered for sale implemented just 128k of non-expandable memory. This prototype was used to provide adequate RAM to run the memory-intensive demo, which showcased speech synthesis software intended to impress the crowd. Components This is a comprehensive list of the integrated circuits in the original Macintosh: a Motorola MC68000 microprocessor at clock speed 7.8336 MHz 64 or 128 KB of ROM in two chips containing parts of the operating system 128 KB of RAM in 16 chips eight TTL chips implementing a video and sound DMA controller, plus two TTL chips providing a 16-bit video buffer (74166 type) one PAL chip generating video timing signals (LAG) two TTL chips providing an 8-bit Pulse-width modulation sound driver (74LS161 type) two analog chips providing sound amplification (MC14016 switch, LF353 op-amp) a Zilog 8530 chip controlling two RS-422 buses through two driver chips an Integrated Woz Machine 400 KB floppy disk controller plus support PAL (ASG) a 6522 VIA bridge chip connecting to the keyboard and clock an Apple real-time clock chip plus a 32.768 kHz quartz oscillator an Intel 8021 microcontroller in the keyboard bus control and extra logic including two PAL chips to activate the other chips (BMU0/1) two PAL chips to convert the 16 MHz clock to other timing signals (TSM, TSG) two TTL chips buffering the RAM to the 68000 (74LS244 type) some inverters (74LS04 type) This personal computer was implemented in four special-purpose LSI chips, six MSI PALs, 19 chips of standard SSI/MSI logic and analog circuits, plus memory. Most of the simpler chips would be consolidated into a few custom chips in the next generation, much reducing cost. Features The above components implemented the Macintosh GUI and networking as described below. Mouse The centerpiece of the new interface was mouse-driven control. The mouse contained only electromechanical components: a button, and two optical encoders. The button was connected to the 6522. The encoders' four outputs were connected two to the 8530 and two to the 6522. The optical encoders detected movement by quadrature. Each encoder had a wheel with radial stripes which would interrupt the light passing between an LED and a light-detecting photodiode, producing electrical pulses with mouse movement. Both the X and the Y encoders were turned by frictional contact with the mouse ball. Two pairs of emitters and detectors were used on each encoder. A first set of pulses is enough to detect the rate of rotation without indicating the direction of rotation, and a second set of synchronized but 90° out of phase pulses provides the direction of rotation. Therefore, two emitter-detector pairs were used for X and Y each. The motion detection signals connected to the 8530 chip using two non-essential pins used for obsolete modems. Originally these signaled modem connection or disconnection. When the mouse moved by a certain amount, the model connect/disconnect signal would change state and the 8530 would interrupt the processor. The operating system would then read the direction signals from the 6522 to differentiate left from right, and up from down, and move the mouse cursor. Cursor and video The mouse cursor was drawn on the screen by software, as were all other on-screen objects. To support real-time animation the screen timing PAL circuit would send a pulse to the 6522 once per vertical retrace. This was the basis for an operating system service called the VBL (vertical blanking) Manager. When the screen was to be redrawn, the cursor would be moved and games had an opportunity to update the display. It could sometimes be difficult to avoid a race condition between a game and the raster display. Flicker could result from the processor writing to the image while it was being sent to the CRT. Therefore, the Macintosh provided a choice of two images in memory, so one could be read while the other was written. The "page" was selected by a general-purpose I/O output connected from the 6522 to the video DMA. As two images added up to 42.75 KiB of precious RAM, however, this feature was unpopular. The DMA graphics controller operated independently and autonomously. One-bit pixels were fetched sixteen at a time over a 16-bit data bus and output at just less 16 MHz, necessitating almost one million fetches per second. Each fetch took one memory access cycle out of every two available during active parts of the display, implying a memory bandwidth for the CPU of about 2.56MB per second. Keyboard The 6522 provided a general-purpose serial bus. The keyboard contained an Intel 8021 microprocessor which transmitted user input to the 6522 over standard phone patch cable. A new keystroke resulted in a processor interrupt. Sound The sampled sound engine piggybacked on the video circuit. As the raster scan returned from the right side of the screen to the left, one byte of data was placed into a PWM generator instead of the screen. This provided 8-bit sampled monaural sound sampled at the 22.25 kHz horizontal blanking rate. General purpose 6522 outputs could mute the sampled sound, or set its volume to one of 8 levels of attenuation. A square wave generator was included on the 6522. One of its two timer circuits could be set to toggle the mute output periodically. This could produce frequencies higher than 11 kHz. This system was not compatible with the Lisa / Mac XL hardware, which in other respects could run Mac software with commonly available software/firmware modifications. Running programs on Lisas which made use of the Mac sound features would cause severe video problems and system crashes. Communication The Zilog 8530 SCC was clocked at around 3.7 MHz. At this speed each serial channel was half as fast as the main memory. The RS-422 protocol was implemented except for the connection-established line, which was used to support the mouse. Apple later changed to an 8-pin connector which dropped it entirely. Storage The Macintosh's persistent storage medium was Sony's floppy diskette drive. This drive replaced the Apple ]['s Shugart drive and the 871K FileWare/"Twiggy" floppy drive used in the original Lisa as the storage medium chosen for the original Macintosh. The single-sided 3.5 inch floppy stored 400 KB by spinning the disk slower when the outer edge was used. A separate microcontroller, the IWM (Integrated Woz Machine), was dedicated to disk control. The floppy operated by polled I/O so access was not seamless: loading and saving files were operations that stopped the entire machine. Twenty bytes of memory were included in the real-time clock counter chip. This data was retained using a 4.5 Volt alkaline battery and was used to store user preferences. Timekeeping The Macintosh featured a real-time clock counting seconds, and a countdown timer with near-microsecond resolution. The former was connected to the 6522 by a serial bus on three general-purpose I/O lines. It functioned much as a quartz watch when the machine was powered off. The latter was built into the 6522 itself. Either could generate interrupts. Memory Map RAM begins at $000000 and ends at $01FFFF (128K)/$07FFFF (512K) and is divided up into a series of different functional areas: System globals ($000000 - $000AFF) System heap ($000B00). SysZone points to start, ApplZone points to end + 1 Application heap (ApplZone; grows upwards. HeapEnd points to its end; ApplLimit sets maximum) Stack. Grows downwards from CurStackBase; SP = A7 points to top of stack. QuickDraw globals. (206 bytes) A5 points to boundary between QD globals and App globals (the "A5 world"). Application globals Application parameters (32 bytes) Jump table Alternate screen buffer, 21,888 bytes (BufPtr) 9344 bytes of undocumented space 740 bytes alternate sound buffer 796 bytes undocumented Screen buffer, 21,888 bytes (ScrnBase = $01A700 (128K)/$07A700 (512K)) System Error handler, 128 bytes Main sound buffer, 740 bytes 28 bytes undocumented, MemTop points to the end of RAM, +1 ROM ($400000 - $41FFFF) sccRBase - SCC read operations - $9FFFF8 sccWBase - SCC write operations - $BFFFF9 IWM (dBase) $DFE1FF VIA (vBase) $EFE1FE aVBufB - register B base - $EFE1FE aVBufA - register A base - $EFFFFE aVIFR - interrupt flag register - $EFFBFE aVIER - interrupt enable register - $EFFDFE The RAM map is organised so that the system globals, system and application heaps grow upwards from low memory, everything else grows downwards from MemTop, from high memory towards low memory. On the 512K Macintosh, the "extra" RAM thus appears as a wider gap between the application heap and the stack, where it is available for application use. References External links Macintosh Serial Ports: Serial Ports as Slots MacTech Volume 1, Issue 8 (July 1985) Macintosh 128K/Macintosh 512K Apple Computer Historical Information - Macintosh Hardware Description 128K

Operating System (OS)

Windows 11 Windows 11 is the latest major release of Microsoft's Windows NT operating system that was announced on June 24, 2021, and is the successor to Windows 10, which was released in 2015. Windows 11 was released to the public on October 5, 2021, as a free upgrade via Windows Update and Windows 11 Installation Assistant on eligible devices running Windows 10. Windows 11 features major changes to the Windows shell influenced by the canceled Windows 10X, including a redesigned Start menu, the replacement of its "live tiles" with a separate "Widgets" panel on the taskbar, the ability to create tiled sets of windows that can be minimized and restored from the taskbar as a group, and new gaming technologies inherited from Xbox Series X and Series S such as Auto HDR and DirectStorage on compatible hardware. Internet Explorer (IE) has been replaced by the Chromium-based Microsoft Edge as the default web browser like its predecessor, Windows 10, and Microsoft Teams is integrated into the Windows shell. Microsoft also announced plans to allow more flexibility in software that can be distributed via Microsoft Store, and to support Android apps on Windows 11 (including a partnership with Amazon to make its app store available for the function). Citing security considerations, the system requirements for Windows 11 were increased over Windows 10. Microsoft only officially supports the operating system on devices using an eighth-generation Intel Core CPU or newer (with some minor exceptions), AMD Ryzen CPU based on Zen+ microarchitecture or newer, or a Qualcomm Snapdragon 850 ARM system-on-chip or newer, with UEFI secure boot and Trusted Platform Module (TPM) 2.0 supported and enabled (although Microsoft may provide exceptions to the TPM 2.0 requirement for OEMs). While the OS can be installed on unsupported processors, Microsoft does not guarantee the availability of updates. Windows 11 removed support for 32-bit x86 CPUs and devices which use BIOS firmware. Windows 11 has received a mixed to positive reception; pre-release coverage of the operating system focused on its stricter hardware requirements, with discussions over whether they were legitimately intended to improve the security of Windows or a ploy to upsell users to newer devices, and over e-waste associated with the changes. Upon its release, Windows 11 received positive reviews for its improved visual design, window management, and a stronger focus on security, but was criticized for regressions and modifications to aspects of its user interface. Development At the 2015 Ignite conference, Microsoft employee Jerry Nixon stated that Windows 10 would be the "last version of Windows", a statement that Microsoft confirmed was "reflective" of its view. The operating system was considered to be a service, with new builds and updates to be released over time. In October 2019, Microsoft announced "Windows 10X", a future edition of Windows 10 designed exclusively for dual-touchscreen devices such as the then-upcoming Surface Neo. It featured a modified user interface designed around context-sensitive "postures" for different screen configurations and usage scenarios, and changes such as a centered taskbar and updated Start menu without Windows 10's "live tiles". Legacy Windows applications would also be required to run in "containers" to ensure performance and power optimization. Microsoft stated that it planned to release Windows 10X devices by the end of 2020. In May 2020, amid the COVID-19 pandemic, chief product officer for Microsoft Windows and Office Panos Panay stated that "as we continue to put customers' needs at the forefront, we need to focus on meeting customers where they are now", and therefore announced that Windows 10X would only launch on single-screen devices at first, and that Microsoft would "continue to look for the right moment, in conjunction with our OEM partners, to bring dual-screen devices to market". In January 2021, it was reported that a job listing referring to a "sweeping visual rejuvenation of Windows" had been posted by Microsoft. A visual refresh for Windows, developed under the codename "Sun Valley", was reportedly set to re-design the system's user interface. Microsoft began to implement and announce some of these visual changes and other new features on Windows 10 Insider Preview builds, such as new system icons (which also included the replacement of shell resources dating back as far as Windows 95), improvements to Task View to allow changing the wallpaper on each virtual desktop, emulation of x64 applications on ARM, and adding the Auto HDR feature from Xbox Series X. On May 18, 2021, Head of Windows Servicing and Delivery John Cable stated that Windows 10X had been canceled and that Microsoft would be "accelerating the integration of key foundational 10X technology into other parts of Windows and products at the company". Announcement At the Microsoft Build 2021 developer conference, CEO and chairman Satya Nadella teased about the existence of the next generation of Windows during his keynote speech. According to Nadella, he had been self-hosting it for several months. He also teased that an official announcement would come very soon. Just a week after Nadella's keynote, Microsoft started sending invitations for a dedicated Windows media event at 11 am ET on June 24, 2021. Microsoft also posted an 11-minute video of Windows start-up sounds to YouTube on June 10, 2021, with many people speculating both the time of the Microsoft event and the duration of the Windows start-up sound video to be a reference to the name of the operating system as Windows 11. On June 24, 2021, Windows 11 was officially announced at a virtual event hosted by Chief Product Officer Panos Panay. According to Nadella, Windows 11 is "a re-imagining of the operating system". Further details for developers such as updates to the Microsoft Store, the new Windows App SDK (code-named "Project Reunion"), new Fluent Design guidelines, and more were discussed during another developer-focused event on the same day. Release The Windows 11 name was accidentally released in an official Microsoft support document in June 2021. Leaked images of a purported beta build of Windows 11's desktop surfaced online later on June 15, 2021, which were followed by a leak of the aforementioned build on the same day. The screenshots and leaked build show an interface resembling that of the canceled Windows 10X, alongside a redesigned out-of-box experience (OOBE) and Windows 11 branding. Microsoft would later confirm the authenticity of the leaked beta, with Panay stating that it was an "early weird build". At the June 24 media event, Microsoft also announced that Windows 11 would be released in "Holiday 2021". Its release will be accompanied by a free upgrade for compatible Windows 10 devices through Windows Update. On June 28, Microsoft announced the release of the first preview build and SDK of Windows 11 to Windows Insiders. On August 31, 2021, Microsoft announced that Windows 11 was to be released on October 5, 2021. The release would be phased, with newer eligible devices to be offered the upgrade first. Since its predecessor Windows 10 was released on July 29, 2015, more than six years earlier, this is the longest time span between successive releases of Microsoft Windows operating systems, beating the time between Windows XP (released on October 25, 2001) and Windows Vista (released on January 30, 2007). Microsoft officially released Windows 11 on October 4, 2021, at 2:00 p.m. PT, which was October 5 in parts of the world. It can be obtained as an in-place upgrade via either the Windows 11 Installation Assistant application (the successor to the Media Creation Tool from Windows 10, which can also generate an ISO image or USB install media), or via Windows Update on eligible devices. Upgrades through Windows Update are a phased rollout, and are distributed on an opt-in basis: Microsoft stated that they "expect all eligible Windows 10 devices to be offered the upgrade to Windows 11 by mid-2022." Eligible devices also may present an option to download Windows 11 during the Windows 10 out-of-box experience (OOBE) on a new installation. In launch they partnered up with Mikey Likes It Ice Cream in NYC to make a flavor named "Bloomberry" based on the default "Bloom" wallpaper to promote Windows 11. The ice cream is blueberry with blueberry pie filling, pound cake & candy chocolate pieces. The Burj Khalifa was also lighted up to promote the operating system. The ice cream could be compared to Windows 7's launch using a 7-patty whopper and Windows 10's launch with a "10-scoop upgrade" for a ice cream parlor that did 8-scoop ice cream. Features Windows 11, the first major Windows release since 2015, builds upon its predecessor by revamping the user interface to follow Microsoft's new Fluent Design guidelines. The redesign, which focuses on ease of use and flexibility, comes alongside new productivity and social features and updates to security and accessibility, addressing some of the deficiencies of Windows 10. The Microsoft Store, which serves as a unified storefront for apps and other content, is also redesigned in Windows 11. Microsoft now allows developers to distribute Win32, progressive web applications, and other packaging technologies in the Microsoft Store, alongside Universal Windows Platform apps. Microsoft also announced plans to allow third-party application stores (such as Epic Games Store) to distribute their clients on Microsoft Store. Windows 11 supports x86-64 software emulation on ARM-based platforms. The collaboration platform Microsoft Teams is integrated into the Windows 11 user interface, and is accessible via the taskbar. Skype will no longer be bundled with the OS by default. Microsoft claims performance improvements such as smaller update sizes, faster web browsing in "any browser", faster wake time from sleep mode, and faster Windows Hello authentication. Windows 11 ships with the Chromium-based Microsoft Edge web browser (for compatibility with Google Chrome web browser), and does not include or support Internet Explorer. Its rendering engine MSHTML (Trident) is still included with the operating system for backwards compatibility reasons, and Edge can be configured with Group Policy to render whitelisted websites in "IE Mode" (which still uses IE's rendering engine MSHTML, instead of Blink layout engine). Windows 11 is the first version of Windows since the original retail release of Windows 95 to not ship with Internet Explorer. The updated Xbox app, along with the Auto HDR and DirectStorage technologies introduced by the Xbox Series X and Series S, will be integrated into Windows 11; the latter requiring a graphics card supporting DirectX 12 and an NVMe solid-state drive. User interface A redesigned user interface is present frequently throughout the operating system, building upon Fluent Design System; translucency, shadows, a new color palette, and rounded geometry are prevalent throughout the UI. A prevalent aspect of the design is an appearance known as "Mica", described as an "opaque, dynamic material that incorporates theme and desktop wallpaper to paint the background of long-lived windows such as apps and settings". Much of the interface and start menu takes heavy inspiration from the now-canceled Windows 10X. The Segoe UI font used since Windows Vista has been updated to a variable version, improving its ability to scale between different display resolutions. The taskbar's buttons are center-aligned by default, and it is permanently pinned to the bottom edge of the screen; it cannot be moved to the top, left, or right edges of the screen as in previous versions of Windows without manual changes to the registry. The notifications sidebar is now accessed by clicking the date and time, with other Quick Actions toggles, as well as volume, brightness, and media playback controls, moved to a new settings pop-up displayed by clicking on the system tray. The "Widgets" button on the taskbar displays a panel with Microsoft Start, a news aggregator with personalized stories and content (expanding upon the "news and interests" panel introduced in later builds of Windows 10). Microsoft Teams is similarly integrated with the taskbar, with a pop-up showing a list of recent conversations. The Start menu has been significantly redesigned, replacing the "live tiles" used by Windows 8.x and 10 with a grid of "pinned" applications, and a list of recent applications and documents. File Explorer was updated to replace its ribbon toolbar with a more traditional toolbar, while its context menus have been redesigned to move some tasks (such as copy and paste) to a toolbar along the top of the menu, and hide other operations under an overflow menu. Task View, a feature introduced in Windows 10, features a refreshed design, and supports giving separate wallpapers to each virtual desktop. The window snapping functionality has been enhanced with two additional features; hovering over a window's maximize button displays pre-determined "Snap Layouts" for tiling multiple windows onto a display, and tiled arrangement of windows can be minimized and restored from the taskbar as a "snap group". When a display is disconnected in a multi-monitor configuration, the windows that were previously on that display will be minimized rather than automatically moved to the main display. If the same display is reconnected, the windows are restored to their prior location. Windows Subsystem for Android On October 21, 2021, Windows Subsystem for Android (WSA) became available to Beta channel builds of Windows 11 for users in the United States, which allows users to install and run Android apps on their devices. Users can install Android apps through any source using the APK file format. An Amazon Appstore client for Microsoft Store will also be available. WSA is based on the Intel Bridge runtime compiler; Intel stated that the technology is not dependent on its CPUs, and will also be supported on x86-64 and ARM CPUs from other vendors. System security As part of the minimum system requirements, Windows 11 only runs on devices with a Trusted Platform Module 2.0 security coprocessor. According to Microsoft, the TPM 2.0 coprocessor is a "critical building block" for protection against firmware and hardware attacks. In addition, Microsoft now requires devices with Windows 11 to include virtualization-based security (VBS), hypervisor-protected code integrity (HVCI), and Secure Boot built-in and enabled by default. The operating system also features hardware-enforced stack protection for supported Intel and AMD processors for protection against zero-day exploits. Like its predecessor, Windows 11 also supports multi-factor authentication and biometric authentication through Windows Hello. Versions Windows 11 is available in two main editions; the Home edition, which is intended for consumer users, and the Pro edition, which contains additional networking and security features (such as BitLocker), as well as the ability to join a domain. Windows 11 Home may be restricted by default to verified software obtained from Microsoft Store ("S Mode"). Windows 11 Home requires an internet connection and a Microsoft account in order to complete first-time setup. In February 2022, it was announced that this restriction will also apply to Windows 11 Pro in the future. Windows 11 SE was announced on November 9, 2021, as an edition exclusively for low-end devices sold in the education market, and a successor to Windows 10 S. It is designed to be managed via Microsoft Intune, and has changed based on feedback from educators to simplify the user interface and reduce "distractions", such as Snap Layouts not containing layouts for more than two applications at once, all applications opening maximized by default, Widgets being completely removed, and Microsoft Edge is configured by default to allow extensions from the Chrome Web Store (primarily to target those migrating from Chrome OS). It is bundled with applications such as Microsoft Office for Microsoft 365, Minecraft Education Edition, and Flipgrid, while OneDrive is used to save files by default. Windows 11 SE does not include Microsoft Store; third-party software is provisioned or installed by administrators. The Windows Insider program carries over from Windows 10, with pre-release builds divided into "Dev" (unstable builds used to test features for future feature updates), "Beta" (test builds for the next feature update; relatively stable in comparison to Dev channel), and "Release Preview" (pre-release builds for final testing of upcoming feature updates) channels. Supported languages Before the launch of Windows 11, OEMs (as well as mobile operators) and businesses were offered two options for device imaging: Component-Based Servicing lp.cab files (for the languages to be preloaded on the first boot) and Local Experience Pack .appx files (for the languages available for download on supported PCs). The 38 fully-localized Language Pack (LP) languages were available as both lp.cab and .appx packages, while the remaining 72 partially-localized Language Interface Pack (LIP) languages were only available as .appx packages. With Windows 11, that process has changed. Five new LP languages were added — Catalan, Basque, Galician, Indonesian, and Vietnamese — bringing the total number of LP languages to 43. Furthermore, these 43 languages can only be imaged using lp.cab packages. This is to ensure a fully supported language-imaging and cumulative update experience. The remaining 67 LIP languages that are LXP-based will move to a self-service model, and can only be added by Windows users themselves via the Microsoft Store and Windows Settings apps, not during the Windows imaging process. Any user, not just admins, can now add both the display language and its features, which can help users in business environments, but these exact options for languages (both LP and LIP) still depend on the OEM and mobile operator. Available languages These languages are either preloaded or available for download, depending on the OEM, region of purchase, and mobile operator. For each of the manufacturers listed, Yes is displayed if the language is supported or available for download in at least one region, and No is displayed if it is not supported in any region. Notes Surface The following languages are available for download on all 2021 and newer Surface devices regardless of the region: Danish German English (Australia) English (Canada) English (United Kingdom) English (United States) Spanish (Spain) Spanish (Mexico) French (Canada) French (France) Italian Dutch Norwegian Polish Finnish Swedish Japanese These additional languages are available for download exclusively in their respective markets, in addition to the above languages: Americas: Portuguese (Brazil) EMEA: Czech, Estonian, Croatian, Latvian, Lithuanian, Hungarian, Portuguese (Portugal), Romanian, Slovak, Slovenian, Turkish, Greek, Bulgarian, Arabic Asia Pacific: Thai, Korean, Chinese (Simplified), Chinese (Traditional), Chinese (Hong Kong) System requirements The basic system requirements of Windows 11 differ significantly from Windows 10. Windows 11 only supports 64-bit systems such as those using an x86-64 or ARM64 processor; IA-32 processors are no longer supported. Thus, Windows 11 is the first consumer version of Windows not to support 32-bit processors (although Windows Server 2008 R2 was the first version of Windows NT to not support them). The minimum RAM and storage requirements were also increased; Windows 11 now requires at least 4GB of RAM and 64GB of storage. S mode is only supported for the Home edition of Windows 11. As of August 2021, the officially supported list of processors includes Intel Core 8th generation and later, AMD Zen+ and later (which include the "AF" revisions of Ryzen 1000 CPUs, which are underclocked versions of Zen+-based Ryzen 2000 parts that supplant Ryzen 1000 parts that could no longer be manufactured due to a change in process), and Qualcomm Snapdragon 850 and later. The compatibility list includes the Intel Core i7-7820HQ, a seventh-generation processor used by the Surface Studio 2, although only on devices that shipped with DCH-based drivers. Legacy BIOS is no longer supported; a UEFI system with Secure Boot and a Trusted Platform Module (TPM) 2.0 security coprocessor is now required. The TPM requirement in particular has led to confusion as many motherboards do not have TPM support, or require a compatible TPM to be physically installed onto the motherboard. Many newer CPUs also include a TPM implemented at the CPU level (with AMD referring to this "fTPM", and Intel referring to it as "Platform Trust Technology" [PTT]), which might be disabled by default and require changing settings in the computer's UEFI firmware, or an UEFI firmware update that is configured to automatically enable the firmware TPM upon installation. Original equipment manufacturers can still ship computers without a TPM 2.0 coprocessor upon Microsoft's approval. Devices with unsupported processors are not blocked from installing or running Windows 11; however, a clean install or upgrade using ISO installation media must be performed as Windows Update will not offer an upgrade from Windows 10. Additionally, users must also accept an on-screen disclaimer stating that they will not be entitled to receive updates, and that damage caused by using Windows 11 on an unsupported configuration are not covered by the manufacturer's warranty. Some third-party software may refuse to run on "unsupported" configurations of Windows 11. Reception Pre-release Reception of Windows 11 upon its reveal was positive, with critics praising the new design and productivity features. However, Microsoft was criticized for creating confusion over the minimum system requirements for Windows 11. The increased system requirements (compared to those of Windows 10) initially published by Microsoft meant that up to 60 percent of existing Windows 10 PCs were unable to upgrade to Windows 11, which has faced concerns that this will make the devices electronic waste. It has been theorized that these system requirements were a measure intended to encourage the purchase of new PCs, especially amid a downturn in PC sales and increased prices due to the global chip shortage. While Microsoft has not specifically acknowledged this when discussing the cutoff, it was also acknowledged that the sixth and seventh generation of Intel Core processors were prominently afflicted by CPU-level security vulnerabilities such as Meltdown and Spectre, and that newer CPUs manufactured since then had increased mitigations against the flaws. Research Vice President of Gartner Stephen Kleynhans felt that Microsoft was "looking at the entire stack from the hardware up through the applications and the user experience and trying to make the entire stack work better and more securely. Launch Andrew Cunningham of Ars Technica praised the improvements to its visual design (describing the new "Mica" appearance as reminiscent of the visual appearance of iOS and macOS, and arguing that Microsoft had "[made] a serious effort" at making the user-facing aspects of Windows 11 more consistent visually), window management, performance (assessed as being equivalent to if not better than Windows 10), other "beneficial tweaks", and its system requirements having brought greater public attention to hardware security features present on modern PCs. Criticism was raised towards Widgets' lack of support for third-party content (thus limiting it to Microsoft services only), regressions in taskbar functionality and customization, the inability to easily select default applications for common tasks such as web browsing (now requiring the user to select the browser application for each file type individually), and Microsoft's unclear justification for its processor compatibility criteria. Cunningham concluded that "as I've dug into [Windows 11] and learned its ins and outs for this review, I've warmed to it more", but argued that the OS was facing similar "public perception" issues to Windows Vista and Windows 8. However, he noted that 11 did not have as many performance issues or bugs as Vista had upon its release, nor was as "disjointed" as 8, and recommended that users who were unsure about the upgrade should stay on Windows 10 in anticipation of future updates to 11. Tom Warren of The Verge described Windows 11 as being akin to a house in the middle of renovations, but that "actually using Windows 11 for the past few months hasn't felt as controversial as I had expected"—praising its updated user interface as being more modern and reminiscent of iOS and Chrome OS, the new start menu for feeling less cluttered than the Windows 10 iteration, updates to some of its stock applications, and Snap Assist. Warren noted that he rarely used the Widgets panel or Microsoft Teams, citing that he preferred the weather display that later versions of Windows 10 offered, and didn't use Teams to communicate with his friends and family. He also acknowledged the expansion of Microsoft Store to include more "traditional" desktop applications. However, he felt that Windows 11 still felt like a work in progress, noting UI inconsistencies (such as dark mode and new context menu designs not being uniform across all dialogues and applications, and the modern Settings app still falling back upon legacy Control Panel applets for certain settings), regressions to the taskbar (including the inability to move it, drag files onto taskbar buttons to focus the corresponding application, and the clock only shown on the primary display in multi-monitor configurations), and promised features (such as dynamic refresh rate support and a universal microphone mute button) not being present on the initial release. Overall, he concluded that "I wouldn't rush out to upgrade to Windows 11, but I also wouldn't avoid it. After all, Windows 11 still feels familiar and underneath all the UI changes, it's the same Windows we've had for decades." PC World was more critical, arguing that Windows 11 "sacrifices productivity for personality, but without cohesion", commenting upon changes such as the inability to use local "offline" accounts on Windows 11 Home, regressions to the taskbar, a "functionally worse" start menu, Microsoft Teams integration having privacy implications and being a ploy to coerce users into switching to the service, File Explorer obscuring common functions under unclear icons, using "terribly sleazy" behaviors to discourage changing the default web browser from Microsoft Edge, and that the OS "anecdotally feels less responsive, slower, and heavier than Windows 10." It was concluded that Windows 11 "feels practical and productive, but less so than its predecessor in many aspects", while its best features were either "hidden deeper within", required specific hardware (DirectStorage, Auto HDR) or were not available on launch (Android app support). See also List of operating systems References External links Windows 11 release information from Microsoft 11 2021 software Android (operating system) ARM operating systems Computer-related introductions in 2021 Proprietary operating systems Tablet operating systems X86-64 operating systems

Operating System (OS)

Symbian Ltd. Symbian Ltd. was a software development and licensing consortium company, known for the Symbian operating system (OS), for smartphones and some related devices. Its headquarters were in Southwark, London, England, with other offices opened in Cambridge, Sweden, Silicon Valley, Japan, India, China, South Korea, and Australia. It was established on 24 June 1998 as a partnership between Psion, Nokia, Ericsson, Motorola, and Sony, to exploit the convergence between personal digital assistants (PDAs) and mobile phones, and a joint-effort to prevent Microsoft from extending its desktop computer monopoly into the mobile devices market. Ten years to the day after it was established, on 24 June 2008, Nokia announced that they intended to acquire the shares that they did not own already, at a cost of €264 million. On the same day the Symbian Foundation was announced, with the aim to "provide royalty-free software and accelerate innovation", and the pledged contribution of the Symbian OS and user interfaces. The acquisition of Symbian Ltd. by Nokia was completed on 2 December 2008, at which point all Symbian employees became Nokia employees. Transfer of relevant Symbian Software Ltd. leases, trademarks, and domain names from Nokia to the Symbian Foundation was completed in April 2009. On 18 July 2009, Nokia's Symbian professional services department, which was not transferred to the Symbian Foundation, was sold to the Accenture consulting company. Overview Symbian Ltd. was the brainchild of Psion's next generation mobile operating system project following the 32-bit version of EPOC. Psion approached the other four companies and decided to work together on a full software suite including kernel, device drivers, and user interface. Much of Symbian's initial intellectual property came from the software arm of Psion. Symbian Ltd developed and licensed Symbian OS, an operating system for advanced mobile phones and personal digital assistants (PDAs). Symbian Ltd wanted the system to have different user interface layers, unlike Microsoft's offerings. Psion originally created several interfaces or "reference designs", which would later end up as Pearl (smartphone), Quartz (Palm-like PDA), and Crystal (clamshell design PDA). One early design called Emerald also ended up in the market on the Ericsson R380. Nokia created the Series 60 (from Pearl), Series 80 and Series 90 platforms (both from Crystal), whilst UIQ Technology, which was a subsidiary of Symbian Ltd. at the time, created UIQ (from Quartz). Another interface was MOAP(S) from NTT Docomo. Despite being partners at Symbian Ltd, the different backers of each interface were effectively competing with each other's software. This became a prominent point in February 2004 when UIQ, which focuses on pen devices, announced its foray in traditional keyboard devices, competing head-on with Nokia's Series 60 offering whilst Nokia was in the process of acquiring Psion's remaining stake in Symbian Ltd. to take overall control of the company. Shareholding The company's founder shareholders were Psion, Nokia and Ericsson. Motorola joined the Symbian consortium shortly later, gaining the same 23.1% stake as Nokia and Ericsson in October 1998. Matsushita followed in May 1999 paying £22 million for an 8.8% stake. This was followed by Siemens taking 5% in April 2002 and Samsung also taking 5% in February 2003. Motorola sold its stake in the company to Psion and Nokia in September 2003. In February 2004, Psion, the originator of Symbian, intended to sell its 31.1% stake in the company to Nokia. This caused unease amongst other shareholders as Nokia would gain majority control of the company, with Sony Ericsson in particular being a vocal critic. The deal finalised with the stake shared between Nokia, Matsushita, Siemens and Sony Ericsson in July 2004, with Nokia holding a 47.9% share. Decline The decline of Symbian Ltd. has been tied to Nokia's fate. By 2007, it enjoyed a high level of success with its operating system running one of every two mobile phones bearing the Nokia logo so that it claimed 65 percent of the mobile market. Its Symbian OS continued to dominate the market until Nokia acquired the company in its entirety in 2008, creating it as an independent non-profit organization called Symbian Foundation. Nokia donated the assets of Symbian Ltd. as well as the Nokia's S60 platform to the new entity with the goal of developing an open-source and royalty-free mobile platform. Nokia, however, began to lose its market share with the emergence of Apple's iPhone and Google's Android. To address this, Nokia abandoned the Symbian OS in favor of Windows Phone OS for its mobile devices, shipping its last Symbian handset in 2013. Having lost its biggest supporter and caretaker, Symbian was absorbed by Accenture, which is supposed to maintain it until 2016. The prior Symbian Foundation has transitioned into a licensing entity with no permanent staff, claiming on its website that it is responsible for only specific licensing and legal frameworks put in place during the open sourcing of the platform. Licensees Licensees of Symbian's operating system were: Arima, BenQ, Fujitsu, Lenovo, Matsushita, Motorola, Nokia, Samsung, Sharp, Siemens and Sony Mobile. Key people Symbian Ltd's CEO at the time of acquisition was Nigel Clifford. Prior CEOs included David Levin, who left in 2005 to head United Business Media, and the founding CEO, Colly Myers, who left the company in 2002 to found IssueBits, the company behind text messaging Short Message Service (SMS) information service Any Question Answered (AQA). See also Symbian Foundation Symbian OS References Defunct companies based in London Ericsson Motorola Nokia assets Panasonic Samsung subsidiaries Siemens Software companies established in 1998 Software companies disestablished in 2008 Software companies of the United Kingdom Sony Mobile Symbian OS 1998 establishments in England 2008 establishments in England

Operating System (OS)

Operational display system Operational Display Systems refers to systems used for tracking the status of multiple objects in avionics. Operational Displays Systems are usually being developed by large countries' civil aviation authorities (such as the Federal Aviation Administration in the United States, or the main Service Providers in Europe, such as DFS, NATS, DSNA, AENA, MUAC, etc., coordinated by Eurocontrol in Europe), with inputs from technology companies and air traffic controllers associations. Air traffic control systems gradually evolved from the old sweeping radar to modern computer-driven systems showing maps, weather info, airplane routes and digitized radar tracks on an ergonomic console. Whereas in the past the information came only from a radar, current systems get inputs from a variety of sources. Radar is still used (multiple sources instead of just one), but is now complemented by transponder data (the aircraft sending out information regarding altitude and identifications) and soon satellite data (for more accurate positioning and overseas navigation). As most data is now digital, this opens the way for extra functionalities to be embedded in the modern Operational Display System, such as trajectory prediction, conflict warnings, traffic flow management, arrival optimisation, etc. Two separate competing systems are currently operating within the US, Common ARTS (Automated Radar Terminal System (Lockheed Martin)) and STARS (Raytheon), with Common ARTS operating at the busiest facilities (NY, Dallas, Atlanta, Southern California, Chicago, Washington DC area, Denver, St Louis, Minneapolis and San Francisco area) within the US. On the display side, the round radar is being replaced by computer-driven cathode ray tubes, which now are being replaced by modern LCD flat screens in en route systems. However a great many US Air Traffic TRACON facilities and Towers still use the older cathode ray tube technology. Most of the larger TRACONs employ a 20" x 20" Sony color tube display; Common ARTS uses the ARTS Color Display (ACD) and the Remote ARTS Color Display (R-ACD), while STARS uses the Terminal Control Workstation (TCW) and Tower Display Workstation (TDW). Towers are slowly replacing old DBrite (cathode ray type remote displays) with an LCD type manufactured by Barco. However these display replacements are currently installed only at the busiest facilities with lower density traffic facilities slated for retrofit later. Avionics

Operating System (OS)