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Windows Phone Windows Phone (WP) is a discontinued family of mobile operating systems developed by Microsoft for smartphones as the replacement successor to Windows Mobile and Zune. Windows Phone featured a new user interface derived from the Metro design language. Unlike Windows Mobile, it was primarily aimed at the consumer market rather than the enterprise market. It was first launched in October 2010 with Windows Phone 7. Windows Phone 8 succeeded it in 2012, replacing the Windows CE-based kernel of Windows Phone 7 with the Windows NT kernel used by the PC versions of Windows (and, in particular, a large amount of internal components from Windows 8). Due to these changes, the OS was incompatible with all existing Windows Phone 7 devices, although it still supported apps originally developed for Windows Phone 7. In 2014, Microsoft released the Windows Phone 8.1 update, which introduced the Cortana virtual assistant, and Windows Runtime platform support to create cross-platform apps between Windows PCs and Windows Phone. In 2015, Microsoft released Windows 10 Mobile, which promoted increased integration and unification with its PC counterpart, including the ability to connect devices to an external display or docking station to display a PC-like interface. Although Microsoft dropped the Windows Phone brand at this time in order to focus more on synergies with Windows 10 for PCs, it was still a continuation of the Windows Phone line from a technical standpoint, and updates were issued for selected Windows Phone 8.1 devices. While Microsoft's investments in the platform were headlined by a major partnership with Nokia (whose Lumia series of smartphones, including the Lumia 520 in particular, would represent the majority of Windows Phone devices sold by 2013) and Microsoft's eventual acquisition of the company's mobile device business for just over US$7 billion (which included Nokia's then-CEO Stephen Elop joining Microsoft to lead its in-house mobile division), the duopoly of Android and iPhone remained the dominant platforms for smartphones, and interest in Windows Phone from app developers began to diminish by mid-decade. Microsoft laid off the Microsoft Mobile staff in 2016, after having taken a write-off of $7.6 billion on the acquired Nokia hardware assets, while market share sunk to 1% that year. Microsoft began to prioritize software development and integrations with Android and iOS instead, and ceased active development of Windows 10 Mobile in 2017. History Development Work on a major Windows Mobile update may have begun as early as 2004 under the codename "Photon", but work moved slowly and the project was ultimately cancelled. In 2008, Microsoft reorganized the Windows Mobile group and started work on a new mobile operating system. The product was to be released in 2009 as Windows Phone, but several delays prompted Microsoft to develop Windows Mobile 6.5 as an interim release. Following this, Windows Phone was developed quickly. One result was that the new OS would not be compatible with Windows Mobile applications. Larry Lieberman, senior product manager for Microsoft's Mobile Developer Experience, told eWeek: "If we'd had more time and resources, we may have been able to do something in terms of backward compatibility." Lieberman said that Microsoft was attempting to look at the mobile phone market in a new way, with the end user in mind as well as the enterprise network. Terry Myerson, corporate VP of Windows Phone engineering, said, "With the move to capacitive touch screens, away from the stylus, and the moves to some of the hardware choices we made for the Windows Phone 7 experience, we had to break application compatibility with Windows Mobile 6.5." From the beginning of Windows Phone until at least 2015, Joe Belfiore was the head of development and the face of the platform's initiatives. Partnership with Nokia On February 11, 2011, at a press event in London, Microsoft CEO Steve Ballmer and Nokia CEO Stephen Elop announced a partnership between their companies in which Windows Phone would become the primary smartphone operating-system for Nokia, replacing Symbian. The event focused largely on setting up "a new global mobile ecosystem", suggesting competition with Android and iOS with the words "It is now a three horse race". Elop stated the reason for choosing Windows Phone over Android, saying: "the single most important word is 'differentiation'. Entering the Android environment late, we knew we would have a hard time differentiating." While Nokia would have had more long-term creative control with Android (note that MeeGo as used by Nokia resembles Android more than it does Windows Phone 7 as both Android and MeeGo are based on the Linux kernel), Elop enjoyed familiarity with his past company where he had been a top executive. The pair announced integration of Microsoft services with Nokia's own services; specifically: Bing would power search across Nokia devices integration of Nokia Maps with Bing Maps integration of Nokia's Ovi store with the Windows Phone Store The partnership involves "funds changing hands for royalties, marketing and ad-revenue sharing", which Microsoft later announced as "measured in billions of dollars." Jo Harlow, whom Elop tapped to run Nokia's smartphone business, rearranged her team to match the structure led by Microsoft's VP of Windows Phone, Terry Myerson. Myerson was quoted as saying, "I can trust her with what she tells me. She uses that same direct and genuine communication to motivate her team." The first Nokia Lumia Windows Phones, the Lumia 800 and Lumia 710, were announced in October 2011 at Nokia World 2011. At the Consumer Electronics Show in 2012 Nokia announced the Lumia 900, featuring a 4.3-inch AMOLED ClearBlack display, a 1.4 GHz processor and 16 GB of storage. The Lumia 900 was one of the first Windows Phones to support LTE and was released on AT&T on April 8. An international version launched in Q2 2012, with a UK launch in May 2012. The Lumia 610 was the first Nokia Windows Phone to run the Tango Variant (Windows Phone 7.5 Refresh) and was aimed at emerging markets. On September 2, 2013, Microsoft announced a deal to acquire Nokia's mobile phone division outright, retaining former CEO Stephen Elop as the head of Microsoft's devices operation. The merger was completed after regulatory approval in all major markets in April 2014. As a result, Nokia's hardware division became a subsidiary of Microsoft operating under the name Microsoft Mobile. In February 2014, Nokia released the Nokia X series of smartphones, (later discontinued) using a version of Android forked from the Android Open Source Project. The operating system was modified; Google's software was not included in favour of competing applications and services from Microsoft and Nokia, and with a user interface highly modified to resemble Windows Phone. Versions Windows Phone 7 Windows Phone 7 was announced at Mobile World Congress in Barcelona, Catalonia, Spain, on February 15, 2010, and released publicly on November 8, 2010 in the United States. In 2011, Microsoft released Windows Phone 7.5 Mango. The update included a mobile version of Internet Explorer 9 that supports the same web standards and graphical capability as the desktop version, multi-tasking of third-party apps, Twitter integration for the People Hub, and Windows Live SkyDrive access. A minor update released in 2012 known as "Tango", along with other bug fixes, lowered the hardware requirements to allow for devices with 800 MHz CPUs and 256 MB of RAM to run Windows Phone. Windows Phone 7 devices can not be upgraded to Windows Phone 8 due to hardware limitations. Windows Phone 7.8 was released as a stopgap update in 2013 to include some of the user interface features from Windows Phone 8. Windows Phone 8 On October 29, 2012, Microsoft released Windows Phone 8, a new generation of the operating system. Windows Phone 8 replaced its previously Windows CE-based architecture with one based on the Windows NT kernel with many components shared with Windows 8. Windows Phone 8.1 Windows Phone 8.1 was announced on April 2, 2014, after being released in preview form to developers on April 10, 2014. New features added include a notification center, support for the Internet Explorer 11 web browser, with tab syncing among Windows 8.1 devices, separate volume controls, and the option to skin and add a third column of live tiles to the Start Screen. Starting with this release, Microsoft dropped the requirement that all Windows Phone OEMs include a camera button and physical buttons for back, Start, and Search. Windows Phone 8.1 introduced Cortana, a voice assistant similar to Siri and Google Now. Cortana replaced the previous Bing search feature, and was released as a beta in the United States in the first half of 2014, before expanding to other countries in early 2015. Windows 10 Mobile Windows 10 Mobile was announced on January 21, 2015, as a mobile operating system for smartphones and tablets running on ARM architecture. Its primary focus is unification with Windows 10, its PC counterpart, in software and services; in accordance with this strategy, the Windows Phone name has been phased out in favor of branding the platform as an edition of Windows 10, although it is still a continuation of Windows Phone, and most Windows Phone 8.1 devices can be upgraded to the platform. Windows 10 Mobile emphasized software using the Universal Windows Platform (UWP), which allowed apps to be designed for use across multiple Windows 10-based product families with nearly identical code, functionality, and adaptations for available input methods. When connected to an external display, devices could also render a stripped-down desktop interface similar to Windows on PCs, with support for keyboard and mouse input. Windows 10 Mobile featured Skype message integration, updated Office Mobile apps, notification syncing with other Windows 10 devices, support for the Microsoft Edge web browser, and other user interface improvements. Microsoft developed a middleware known as Windows Bridge to allow iOS Objective-C and Android C++ or Java software to be ported to run on Windows 10 Mobile with limited changes to code. With the diminishing interest and application development for the platform, Microsoft discontinued active development of Windows 10 Mobile in 2017, and the platform was declared end of life on January 14, 2020. Features User interface Windows Phone features a user interface based on Microsoft's "Metro" design language, and was inspired by the user interface in the Zune HD. The home screen, called the "Start screen", is made up of "Live Tiles", which have been the inspiration for the Windows 8 live tiles. Tiles are links to applications, features, functions and individual items (such as contacts, web pages, applications or media items). Users can add, rearrange, or remove tiles. Tiles are dynamic and update in real time – for example, the tile for an email account would display the number of unread messages or a tile could display a live update of the weather. Since Windows Phone 8, live tiles can also be resized to either a small, medium, or large appearance. Several features of Windows Phone are organized into "hubs", which combine local and online content via Windows Phone's integration with popular social networks such as Facebook, Windows Live, and Twitter. For example, the Pictures hub shows photos captured with the device's camera and the user's Facebook photo albums, and the People hub shows contacts aggregated from multiple sources including Windows Live, Facebook, and Gmail. From the hub, users can directly comment and 'like' on social network updates. The other built-in hubs are Xbox Music and Video, Xbox Live Games, Windows Phone Store, and Microsoft Office. Windows Phone uses multi-touch technology. The default Windows Phone user interface has a dark theme that prolongs battery life on OLED screens as fully black pixels do not emit light. Alternatively, users may choose a light theme in their phone's settings menu. The user may also choose from several accent colors. User interface elements such as links, buttons and tiles are shown in the user's chosen accent color. Third-party applications can be automatically themed with these colors. Windows Phone 8.1 introduces transparent tiles and a customizable background image for the Start screen. The image is visible through the transparent area of the tiles and features a parallax effect when scrolling which gives an illusion of depth. If the user does not pick a background image the tiles render with the accent color of the theme. Text input Users input text by using an on-screen virtual keyboard, which has a dedicated key for inserting emoticons, and features spell checking and word prediction. App developers (both inhouse and ISV) may specify different versions of the virtual keyboard in order to limit users to certain character sets, such as numeric characters alone. Users may change a word after it has been typed by tapping the word, which will invoke a list of similar words. Pressing and holding certain keys will reveal similar characters. The keys are somewhat larger and spaced farther apart when in landscape mode. Phones may also be made with a hardware keyboard for text input. Users can also add accents to letters by holding on an individual letter. Windows Phone 8.1 introduces a new method of typing by swiping through the keyboard without lifting the finger, in a manner similar to Swype and SwiftKey. Web browser Internet Explorer on Windows Phone allows the user to maintain a list of favorite web pages and tiles linking to web pages on the Start screen. The browser supports up to 6 tabs, which can all load in parallel. Other features include multi-touch gestures, smooth zoom in/out animations, the ability to save pictures that are on web pages, share web pages via email, and support for inline search which allows the user to search for a word or phrase in a web page by typing it. Tabs are synced with Windows 8.1 devices using Internet Explorer 11. Contacts Contacts are organized via the "People hub", and can be manually entered into contacts or imported from Facebook, Windows Live Contacts, Twitter, LinkedIn, Google, and Outlook. A "What's New" section shows a user's Facebook news feed and a "Pictures" section show pictures from those social networks, while a "Me" section within the "People" hub shows a user's own social network status and wall and allows them to view social network updates. Contacts can also be pinned to the Start Screen. The contact's "Live Tile" displays their social network status and profile picture on the homescreen. Clicking on a contact's tile or accessing their card within the "People" hub will reveal their recent social network activity as well as the rest of their contact information. If a contact has information stored on multiple networks, users can link the two separate contact accounts, allowing the information to be viewed and accessed from a single card. As of Windows Phone 7.5, contacts can also be sorted into "Groups". Here, information from each of the contacts is combined into a single page which can be accessed directly from the Hub or pinned to the Start screen. Email Windows Phone supports Outlook.com, Exchange, Yahoo! Mail and Gmail natively and supports many other services via the POP and IMAP protocols. Updates added support for more services such as iCloud and IBM Notes Traveler. Contacts and calendars may be synced from these services as well. Users can also search through their email by searching in the subject, body, senders, and receivers. Emails are shown with threads, and multiple email inboxes can be combined into a single view (a feature commonly referred to as "combined inbox") or can viewed separately. Multimedia Xbox Music and Xbox Video are built-in multimedia hubs providing entertainment and synchronization capabilities between PC, Windows Phone, and other Microsoft products. The two hubs were previously combined until standalone apps were released in late 2013, shortly before Windows Phone 8.1 debuted. The hubs allow users to access music, videos, and podcasts stored on the device, and links directly to the "Xbox Music Store" to buy or rent music and the "Xbox Video Store" to purchase movies and TV episodes. Xbox Music also allows the user to stream music with an Xbox Music Pass. When browsing the music by a particular artist, users are able to view artist biographies and photos. The Xbox Music hub also integrates with many other apps that provide video and music services, including, but not limited to, iHeartRadio, YouTube, and Vevo. This hub also includes Smart DJ which compiles a playlist of songs stored on the phone similar to the song or artist selected. The Pictures hub displays the user's Facebook and OneDrive photo albums, as well as photos taken with the phone's built-in camera. Users can also upload photos to social networks, comment on photos uploaded by other people, and tag photos posted to social networks. Multi-touch gestures permit zooming in and out of photos. An official file manager app called Files, which is available for download from the Windows Phone Store, enables users to move and rearrange documents, videos, music and other files within their device's hard drive or to an external SD card. Media support Windows Phone supports WAV, MP3, WMA, AMR, AAC/MP4/M4A/M4B and 3GP/3G2 standards. The video file formats supported on WP include WMV, AVI, MP4/M4V, 3GP/3G2 and MOV (QuickTime) standards. These supported audio and video formats would be dependent on the codecs contained inside them. It has also been previously reported that the DivX and Xvid codecs within the AVI file format are also playable on WP devices. Note that Windows Phone does not support DRM protected media files that are obtained from services other than Xbox Music Pass. The image file formats that are supported include JPG/JPEG, PNG, GIF, TIF and Bitmap (BMP). Users can also add custom ringtones which are less than 1MB in size and less than 40 seconds long. DLNA streaming and stereoscopic 3D are also supported. Games The "Games hub" provides access to games on a phone along with Xbox Live functionality, including the ability for a user to interact with their avatar, view and edit their profile, see their achievements and view leaderboards, and send messages to friends on Xbox Live. The hub also features an area for managing invitations and turn notifications in turn-based multiplayer games. Games are downloaded from Windows Phone Store. Search Bing is the default search engine on Windows Phone handsets because its functions are deeply integrated in the OS (which also include the utilization of its map service for location-based searches and queries). However, Microsoft has stated that other search engine applications can be used. In the area of location-based searches, Bing Maps (which is powered by Nokia's location services) provides turn-by-turn navigation service to Windows Phone users, and Local Scout shows interest points such as attractions and restaurants in the nearby area. On Nokia devices, Nokia's Here Maps is preinstalled in place of Bing Maps. Furthermore, Bing Audio allows the user to match a song with its name, and Bing Vision allows the user to scan barcodes, QR codes, and other types of tags. Cortana Every Windows Phone has either a dedicated physical Search button or an on-screen Search button, which was previously reserved for a Bing Search app, but has been replaced on Windows Phone 8.1 devices and later in the United Kingdom and United States by Cortana, a digital personal assistant which can also double as an app for basic searches. Cortana allows users to do tasks such as set calendar reminders and alarms, and recognizes a user's natural voice, and can be used to answer questions (like current weather conditions, sports scores, and biographies). The app also keeps a "Notebook" to learn a user's behavior over time and tailor reminders for them. Users can edit the "Notebook" to keep information from Cortana or reveal more about themselves. Office suite All Windows Phones come preinstalled with Microsoft Office Mobile, which provides interoperability between Windows Phone and the desktop version of Microsoft Office. Word Mobile, Excel Mobile, PowerPoint Mobile, and SharePoint Workspace Mobile apps are accessible through a single "Office Hub," and allow most Microsoft Office file formats to be viewed and edited directly on a Windows Phone device. The "Office Hub" can access files from OneDrive and Office 365, as well as files which are stored locally on the device's hard drive. Although they are not preinstalled in Windows Phone's "Office Hub," OneNote Mobile, Lync Mobile, and OneDrive for Business can be downloaded separately as standalone applications from the Windows Phone Store. Multitasking Multitasking in Windows Phone is invoked through long pressing the "back" arrow, which is present on all Windows Phones. Windows Phone 7 uses a card-based task switcher, whereas later versions of Windows Phone utilize true background multitasking. Sync Windows Phone 7 Zune Software manages the contents on Windows Phone 7 devices and Windows Phone can wirelessly sync with Zune Software. Later versions Syncing content between Windows Phone 8 and 8.1 and Windows PCs or Macs is provided through the Windows Phone App, which is available for both Windows and Mac OS X. It is the official successor to Zune software only for Windows Phone 8 and Windows Phone 8.1, and allows users to transfer content such as music, videos, and documents. Users also have the ability to use a "Tap and Send" feature that allows for file transfer between Windows phones, and NFC-compatible devices through NFC. Updates Software updates are delivered to Windows Phone users via Microsoft Update, as is the case with other Windows operating systems. Microsoft initially had the intention to directly update any phone running Windows Phone instead of relying on OEMs or wireless carriers, but on January 6, 2012, Microsoft changed their policy to let carriers decide if an update will be delivered. While Windows Phone 7 users were required to attach their phones to a PC to install updates, starting with Windows Phone 8, all updates are done via over-the-air downloads. Since Windows Phone 8, Microsoft has also begun releasing minor updates that add features to a current OS release throughout the year. These updates were first labeled "General Distribution releases" (or GDRs), but were later rebranded simply as "Updates". All third-party applications can be updated automatically from the Windows Phone Store. Advertising platform Microsoft has also launched an advertising platform for the Windows Phone platform. Microsoft's General Manager for Strategy and Business Development, Kostas Mallios, said that Windows Phone will be an "ad-serving machine", pushing advertising and brand-related content to the user. The platform will feature advertising tiles near applications and toast notifications, which will bring updating advertising notifications. Mallios said that Windows Phone will be able to "preserve the brand experience by going directly from the web site right to the application", and that Windows Phone "enables advertisers to connect with consumers over time". Mallios continued: "you're now able to push information as an advertiser, and stay in touch with your customer. It's a dynamic relationship that is created and provides for an ongoing dialog with the consumer." Bluetooth Windows Phone supports the following Bluetooth profiles: Advanced Audio Distribution Profile (A2DP 1.2) Audio/Video Remote Control Profile (AVRCP 1.3) Hands Free Profile (HFP 1.5) Headset Profile (HSP 1.1) Phone Book Access Profile (PBAP 1.1) Bluetooth File Transfer (OBEX) (from Windows Phone 7.8) Windows Phone BTF support is available from Windows Phone 7.8, but is limited to the transferring of pictures, music and videos via a 'Bluetooth Share' app. Feature additions Microsoft keeps a site where people can submit and vote on features they would like to see added to Windows Phone. Store The Windows Phone Store was used to digitally distribute music, video content, podcasts, and third-party applications to Windows Phone handsets. The store was accessible using the Zune Software client or the Windows Phone Store hub on devices (though videos were not downloadable through the store hub and must be downloaded and synced through the Zune software). The Store was managed by Microsoft, which included an approval process. As of March 2012, the Windows Phone Store was available in 54 countries. Music and videos Xbox Music offered approximately 50 million songs up to 320 kbit/s in DRM-free MP3 format from the big four music groups (EMI, Warner Music Group, Sony BMG and Universal Music Group), as well as smaller music labels. Xbox Video offered HD movies from Paramount, Universal, Warner Brothers, and other studios and plus television shows from popular television networks. Microsoft offered the Xbox Music Pass music subscription service, which allowed subscribers to download an unlimited number of songs for as long as their subscription was active and play them on current Microsoft devices. Applications and games Development Third-party applications and games for Windows Phone can be based on XNA, a Windows Phone-specific version of Silverlight, the GUI-based Windows Phone App Studio, or the Windows Runtime, which allows developers to develop an app for both the Windows Store and Windows Phone Store simultaneously. App developers can develop apps using C# / Visual Basic.NET (.NET), C++ (CX) or HTML5/JavaScript. For Windows Phone apps to be designed and tested within Visual Studio or Visual Studio Express, Microsoft offers Windows Phone Developer Tools, which run only on Windows Vista SP2 and later, as an extension Microsoft also offers Expression Blend for Windows Phone for free. On November 29, 2009, Microsoft announced the Release-to-web (RTW) version of its Visual Basic .NET Developer Tool, to aid development of Windows Phone apps in Visual Basic. Later versions of Windows Phone support the running of managed code through a Common Language Runtime similar to that of the Windows operating system itself, as opposed to the .NET Compact Framework. This, along with support for native C and C++ libraries, allows some traditional Windows desktop programs to be easily ported to Windows Phone. Submission Registered Windows Phone and Xbox Live developers can submit and manage their third-party applications for the platforms through the App Hub web applications. The App Hub provides development tools and support for third-party application developers. The submitted applications undergo an approval process for verifications and validations to check if they qualify the applications standardization criteria set by Microsoft. The cost of the applications that are approved is up to the developer, but Microsoft will take 20% of the revenue (the other 80% goes to the developer). Microsoft will only pay developers once they reach a set sales figure, and will withhold 30% tax from non-US developers, unless they first register with the United States Government's Internal Revenue Service. Microsoft only pays developers from a list of thirty countries. A yearly fee is also payable for developers wishing to submit apps. In order to get an application to appear in the Windows Phone Store, the application must be submitted to Microsoft for approval. Microsoft has outlined the content that it will not allow in the applications, which includes content that, among other things, advocates discrimination or hate, promotes usage of drugs, alcohol or tobacco, or includes sexually suggestive material. Hardware Windows Phone 7 devices were first produced by HTC, LG and Samsung. These hardware partners were later joined by Acer, Alcatel, Fujitsu, Toshiba, Nokia, and Chinese OEM ZTE. Windows Phone 8 devices were being produced by HTC, Huawei, Nokia, and Samsung. At the 2014 Mobile World Congress, Microsoft announced that upcoming Windows Phone 8.1 devices would be manufactured by Celkon, Gionee, HTC, Huawei, JSR, Karbonn, LG, Lenovo, Longcheer, Micromax, Microsoft Mobile, Samsung, Xolo, and ZTE among others. Sony (under the Xperia or Vaio brand) had also stated its intention to produce Windows Phone devices in the near future. Yezz announced two smartphones in May, and at Computex 2014 BYD, Compal, Pegatron, Quanta and Wistron were also named as new Windows Phone OEMs. In August 2014, Huawei said it was dropping support for Windows Phone due to low sales. Reception User interface The Metro UI and overall interface of the OS were highly praised for their style, with ZDNet noting its originality and fresh clean look. Engadget and ZDNet applauded the integration of Facebook into the People Hub as well as other built-in capabilities, such as Windows Live, etc. However, in version 8.1 the once tight Facebook and Twitter integration was removed so that updates from those social media sites had to be accessed via their respective apps. Market share Windows Phone 7 (2010–2012) For the first months, market specialists were optimistic about its adoption with IDC forecasting that Windows Phone would surpass IPhone by 2015. According to Gartner, there were 1.6 million devices running Microsoft OS sold to customers in Q1 2011 worldwide. 1.7 million smartphones using a Microsoft mobile OS were sold in Q2 2011, for a 1.6% market share. In Q3 2011, Microsoft's worldwide market share dropped slightly to 1.5%. In Q4 2011 market share increased to 1.9%, and it stayed at 1.9% for Q1 2012. Reports for Q2, Q3 and Q4 of year 2011 include both Windows Phone and small part of Windows Mobile marketshare under the same "Microsoft mobile OS" banner, and do not make the distinction of separating the marketshare values of the two. According to Nielsen, Windows Phone had a 1.7% market share in Q1 2012, and then dropped back to 1.3% in Q2 2012. Windows Phone 8 (2012–2015) After the release of Windows Phone 8, Gartner reported that Windows Phone's marketshare jumped to 3% in Q4 2012, a 124% increase over the same time period in 2011. In mid-2012, IDC had suggested that Windows Phone might surpass the faltering BlackBerry platform and potentially even Apple iOS, because of Nokia dominance in emerging markets like Asia, Latin America, and Africa, as the iPhone was considered too expensive for most of these regions and BlackBerry OS possibly going to feature a similar fate as Symbian. IDC's projections were partially correct, as in Q1 2013 Windows Phone shipments surpassed BlackBerry shipment volume for the first time. IDC had to slash the Windows Phone predictions once again, to 7 percent of total market in 2018, because of the slow growth. As of the third quarter of 2013, Gartner reported that Windows Phone holds a worldwide market share of 3.6%, up 123% from the same period in 2012 and outpacing Android's rate of growth. According to Kantar's October 2013 report, Windows Phone accounted for 10.2% of all smartphone sales in Europe and 4.8% of all sales in the United States. Some analysts have attributed this spike in sales to both Windows Phone 8 and Nokia's successful push to market low and mid-range Windows Phones like the Lumia 520 and Lumia 620 to a younger audience. Gartner reported that Windows Phone market share finished 2013 at 3.2%, which while down from the third quarter of 2013 was still a 46.7% improvement from the same period in 2012. IDC reported that Windows Phone market share, having peaked in 2013 at 3.4%, had dropped to 2.5% by the second quarter of 2014. In August 2017, the New York Police Department ordered Apple iPhone products to replace its deployment of 36,000 Lumia 830 and Lumia 640 XL Windows Phone devices, partly citing Microsoft's end of support for Windows Phone 8.1 on July 11, 2017 and its minuscule market share. Developer interest Microsoft's developer initiative programs and marketing have gained attention from application developers. As of Q3 2013, an average of 21% of mobile developers use the Windows Phone platform, with another 35% stating they are interested in adopting it. Some reports have indicated that developers may be less interested in developing for Windows Phone because of lower ad revenue when compared to competing platforms. The main criticism of Windows Phone was the lack of applications when compared to iOS and Android. This also affected Microsoft's largest partner in the platform, Nokia, whose vice president showed his frustration at the lack of apps for the platform. A few developers refused to develop apps while preventing third-party alternatives. A well known example was Snapchat, which announced a crackdown on third-party apps of its service and its users in November 2014. Microsoft was forced to remove third-party Snapchat apps (including the popular 6snap) from the Windows Phone Store a month later, while Snapchat never developed an official app for those users. A petition from users requesting an official Snapchat app reached 43,000 signatures in 2015, but the company still decided not to build an app. In addition, Google twice blocked Microsoft's own YouTube app for violating its terms of service, objecting to the app's ability to download videos and prevent ads. The app returned in October 2013 but stripped of many features. By 2014, Windows Phone was losing share and relevance; between that year and 2015 it was reported that developers were backing out of the platform and retiring apps because of the low market share. Many high-profile apps were discontinued by 2015 such as American Airlines, NBC, Pinterest and others. In addition, Microsoft itself retired some of its own first-party apps. See also Comparison of mobile operating systems Microsoft Surface References External links Official website (Archive) Mobile phones introduced in 2010 Products and services discontinued in 2020 Discontinued Microsoft products Smartphones Microsoft franchises Cloud clients Mobile operating systems ARM operating systems C (programming language) software C++ software Discontinued Microsoft operating systems Discontinued versions of Microsoft Windows Defunct consumer brands

Operating System (OS)

Orchestration (computing) In system administration, orchestration is the automated configuration, coordination, and management of computer systems and software. A number of tools exist for automation of server configuration and management, including Ansible, Puppet, Salt, Terraform, and AWS CloudFormation. Usage Orchestration is often discussed in the context of service-oriented architecture, virtualization, provisioning, converged infrastructure and dynamic datacenter topics. Orchestration in this sense is about aligning the business request with the applications, data, and infrastructure. In the context of cloud computing, the main difference between workflow automation and orchestration is that workflows are processed and completed as processes within a single domain for automation purposes, whereas orchestration includes a workflow and provides a directed action towards larger goals and objectives. In this context, and with the overall aim to achieve specific goals and objectives (described through quality of service parameters), for example, meet application performance goals using minimized cost and maximize application performance within budget constraints, cloud management solutions also encompass frameworks for workflow mapping and management. See also References Enterprise application integration Business terms Computing terminology Orchestration software

Operating System (OS)

Macintosh clone A Macintosh clone, also known as a Clonintosh (a portmanteau of "Clone" and "Macintosh"), is a computer running the Mac OS operating system that was not produced by Apple Inc. The earliest Mac clones were based on emulators and reverse-engineered Macintosh ROMs. During Apple's short lived Mac OS 7 licensing program authorized Mac clone makers were able to either purchase 100% compatible motherboards or build their own hardware using licensed Mac reference designs. Since Apple's switch to the Intel platform, many non-Apple Wintel/PC computers are technologically so similar to Mac computers that they are able to boot the Mac operating system using a varying combination of community-developed patches and hacks. Such a Wintel/PC computer running macOS is more commonly referred to as a Hackintosh and the most popular community effort developing and sharing the requisite software patches is known as OSx86. Background The Apple II and IBM PC computer lines were "cloned" by other manufacturers who had reverse-engineered the minimal amount of firmware in the computers' ROM chips and subsequently legally produced computers that could run the same software. These clones were seen by Apple as a threat, as Apple II sales had presumably suffered from the competition provided by Franklin Computer Corporation and other clone manufacturers, both legal and illegal. At IBM, the threat proved to be real: most of the market eventually went to clone-makers, including Compaq, Leading Edge, Tandy, Kaypro, Packard Bell, Amstrad in Europe, and dozens of smaller companies, and in short order IBM found it had lost control over its own platform. Apple eventually licensed the Apple II ROMs to other companies, primarily to educational toy manufacturer Tiger Electronics in order to produce an inexpensive laptop with educational games and the AppleWorks software suite: the Tiger Learning Computer (TLC). The TLC lacked a built-in display. Its lid acted as a holster for the cartridges that stored the bundled software, as it had no floppy drive. Emulators Long before true clones were available, the Atari ST could emulate a Mac by adding the third-party Magic Sac emulator, released in 1985, and, later, the Spectre, Spectre GCR, and Aladin emulators. The first three of those emulators required that the user purchase a set of Mac ROMs sold as system upgrades to Macintosh users. Later, multiple emulators were released for the Amiga. Starting with the sales of PowerPC Macs, a CPU emulator to run 68000 applications was built into the Mac OS. By the time 68060 processors were available, PowerPC Macs became so powerful that they ran 68000 applications faster than any 68000-based computer, including any Amiga, Atari ST or Sharp X68000, making it unnecessary for Apple to release a 68060-equipped Mac. This means even a 68060-upgraded Atari ST clone or Amiga, which avoid CPU emulation, were always slower, on top of causing some programs not to work thanks to imperfect virtualization of the Mac system and remaining machine components. Connectix also released another 68k emulator for Macs, replacing the original, called Speed Doubler, supposedly reported to be even faster than Apple's. As the years went by, the emulator wasn't updated to work with later versions of the original Mac OS, however, supposedly because Apple's own 68k emulator eventually surpassed it in performance, and the OS itself relied further on native PowerPC code with each new Mac OS update. There was also a software emulator for x86 platforms running DOS/Windows and Linux called Executor, from ARDI. ARDI reverse-engineered the Mac ROM and built a 68000 CPU emulator, enabling Executor to run most (but not all) Macintosh software, from System 5 to System 7, with good speed. The migration from 68000 to PowerPC, and the added difficulties of emulating a PowerPC on x86 platforms, made targeting the later Mac OS versions impractical. Unlicensed clones Wary of repeating history and wanting to retain tight control of its product, Apple's Macintosh strategy included technical and legal measures that rendered production of Mac clones problematic. The original Macintosh system software contained a very large amount of complex code, which embodied the Mac's entire set of APIs, including the use of the GUI and file system. Through the 1980s and into the 1990s, much of the system software was included in the Macintosh's physical ROM chips. Therefore, any competitor attempting to create a Macintosh clone without infringing copyright would have to reverse-engineer the ROMs, which would have been an enormous and costly process without certainty of success. Only one company, Nutek, managed to produce "semi-Mac-compatible" computers in the early 1990s by partially re-implementing System 7 ROMs. This strategy, making the development of competitive Mac clones prohibitively expensive, successfully shut out manufacturers looking to create computers that would directly compete with Apple's product lines. However, companies like Outbound Systems, Dynamac and Colby Systems, were able to sidestep the Mac cloning process by targeting high-end, high-profit market segments without suitable product offerings from Apple and offering Mac conversions instead. In the early 1980s, Brazil's military dictatorship instituted trade restrictions that prohibited the importation of computers from overseas manufacturers, and these restrictions were not lifted until 1993. A Brazilian company called Unitron (which had previously produced Apple II clones) developed a Macintosh clone with specifications similar to the Mac 512K, and proposed to put it on sale. Although Unitron claimed to have legitimately reverse-engineered the ROMs and hardware, and Apple did not hold patents covering the computer in Brazil, Apple claimed the ROMs had simply been copied. Ultimately, under pressure from the US government and local manufacturers of PC clones the Brazilian Computer and Automation Council did not allow production to proceed. Hackintosh When Apple migrated to the PC-Intel platform in the mid 2000s, Apple hardware was more or less the same as generic PC hardware from a platform perspective. This theoretically allowed for installation of Mac OS X on non-Apple hardware. Hackintosh is the term appropriated by hobbyist programmers, who have collaborated on the Internet to install versions of Mac OS X v10.4 onwards dubbed Mac OSx86 to be used on generic PC hardware rather than on Apple's own hardware. Apple contends this is illegal under the DMCA, so in order to combat illegal usage of their operating system software, they continue to use methods to prevent Mac OS X (now macOS) from being installed on unofficial non-Apple hardware, with mixed success. At present, with proper knowledge and instruction, macOS installation is more or less straightforward. Several online communities have sprung up to support end-users who wish to install macOS on non-Apple hardware. Some representative examples of these are Dortania and InsanelyMac. Psystar Corporation In April 2008, Psystar Corporation based in Miami, Florida, announced the first commercially available OSx86, a Wintel/PC computer with Mac OS X Leopard pre-installed partially with software from the OSx86 community project. Apple immediately sued in July 2008 and a protracted legal battle followed, ending in November 2009 with a summary judgement against Psystar. In May 2012, the U.S. Supreme Court denied Psystar's appeal, closing the case for good. Licensed Macintosh clones In 1992, Macworld published an editorial stating that Apple clones were coming, and that the company should license its technology to others so it would benefit as the overall Macintosh market grew. By 1995, Apple Macintosh computers accounted for around 7% of the worldwide desktop computer market. Apple executives decided to launch an official clone program in order to expand Macintosh market penetration. Apple's Mac OS 7 licensing program entailed the licensing of the Macintosh ROMs and system software to other manufacturers, each of which agreed to pay a flat fee for a license, and a royalty (initially ) for each clone computer they sold. This generated quick revenues for Apple during a time of financial crisis. From early 1995 through mid-1997, it was possible to buy PowerPC-based clone computers running Mac OS, most notably from Power Computing and UMAX. However, by 1996 Apple executives were worried that high-end clones were cannibalizing sales of their own high-end computers, where profit margins were highest. A total of 75 distinct Macintosh clone models are known to have been introduced during the licensee era. The following companies produced licensed Mac clones: Jobs ends the official program Soon after Steve Jobs returned to Apple in 1997, he personally tried to renegotiate licensing deals more favorable to Apple five times over the course of three weeks and in his words each time was "basically told to pound sand". This response caused him to halt negotiations of upcoming licensing deals with OS licensees that Apple executives complained were still financially unfavorable. Because the clone makers' licenses were valid only for Apple's System 7 operating system, Apple's release of Mac OS 8 left the clone manufacturers without the ability to ship a current Mac OS version and effectively ended the cloning program. Apple bought Power Computing's Mac clone business for and gave their users free Mac OS 8 upgrade disks, ending the clone era. Only UMAX ever obtained a license to ship Mac OS 8 and get Mac OS 8 upgrade disks, which expired in July 1998 (Power Computing also got Mac OS 8 disks by their acquisition by Apple). All other manufacturers had their Macintosh clone contract terminated by late 1997 and either continued their brands as PC clones or discontinued them all together. Some of the clone manufacturers even went out of business. Reportedly, a heated telephone conversation between Jobs and Motorola CEO Christopher Galvin resulted in the contentious termination of Motorola's clone contract, and the long-favored Apple being demoted to "just another customer" mainly for PowerPC CPUs. In 1999, Jobs had discussions with Ben Rosen, Chairman and interim CEO of Compaq at the time, for the world's then-largest Wintel PC manufacturer to license Mac OS, which would have been a coup for Apple. However no agreement was reached, as Apple had second thoughts about licensing its "crown jewel", while Compaq did not want to offend Microsoft, which it had partnered with since its founding in 1982. By 2007, five years after Compaq merged with HP, Rosen told Jobs he had switched to being a Mac user. In 2001, Jobs reportedly had a meeting with Sony executives, saying he was "willing to make an exception" for Sony VAIO to run Mac OS X, although the negotiations later fell through. Since Apple transitioned the Macintosh to an Intel platform in 2006, and subsequent to a major increase in visibility and a gain in computer market share for Apple with the success of the iPod, large computer system manufacturers such as Dell have expressed renewed interest in creating Macintosh clones. While various industry executives, notably Michael Dell, have stated publicly that they would like to sell Macintosh-compatible computers, Apple VP Phil Schiller said the company does not plan to let people run Mac OS X (macOS) on other computer makers' hardware. "We will not allow running Mac OS X on anything other than an Apple Mac," he said. Macintosh conversion Unlike Mac clones that contain little or no original Apple hardware, a Mac conversion is an aftermarket enclosure kit that requires the core components of a previously purchased, genuine Apple Mac computer, such as the Macintosh ROM or the motherboard, in order to become a functional computer system. This business model is most commonly used in the car industry, with one of the most famous examples being the Shelby Mustang, a high performance variant of the Ford Mustang, and is protected in the U.S. by the First-sale doctrine and similar legal concepts in most other countries. While Mac clones traditionally aim to compete directly with Apple's solutions through lower prices, Mac conversions target market segments that lack dedicated solutions from Apple, and where the need for a Mac solution is high enough to justify the combined cost of the full price of the Mac donor computer plus the price of the conversion kit & labor. The following companies produced Mac conversions: See also IBM PC clone References External links Mac Clones and New O/S movie from archive.org Mac Clones by Manufacturer (at EveryMac.com) Macintosh clones (at LowEndMac.com) Infos on all macs and clones (incl. details on some mainboard PCBs / at MacInfo.de) Apple Squeezes Mac Clones Out of the Market (at LowEndMac.com)

Operating System (OS)

MacOS High Sierra macOS High Sierra (version 10.13) is the fourteenth major release of macOS, Apple Inc.'s desktop operating system for Macintosh computers. macOS High Sierra was announced at the WWDC 2017 on June 5, 2017 and was released on September 25, 2017. The name "High Sierra" refers to the High Sierra region in California. Following on from macOS Sierra, its iterative name also alludes to its status as a refinement of its predecessor, focused on performance improvements and technical updates rather than user features. This makes it similar to previous macOS releases Snow Leopard, Mountain Lion and El Capitan. Among the apps with notable changes are Photos and Safari. System requirements macOS High Sierra is supported on the following Macintosh computers: iMac: Late 2009 or later MacBook: Late 2009 or later MacBook Pro: Mid 2010 or later MacBook Air: Late 2010 or later Mac Mini: Mid 2010 or later Mac Pro: Mid 2010 or later macOS High Sierra requires at least 2 GB of RAM and 14.3 GB of available disk space. It is possible to install High Sierra on many older Macintosh computers that are not officially supported by Apple. This requires using a patch to modify the install image. Changes System Apple File System Apple File System (APFS) replaces HFS Plus as the default file system in macOS for the first time with High Sierra. It supports 64‑bit inode numbers, is designed for flash memory, and is designed to speed up common tasks like duplicating a file and finding the size of a folder's contents. It also has built‑in encryption, crash‑safe protections, and simplified data backup on the go. Metal 2 Metal, Apple's low-level graphics API, has been updated to Metal 2. It includes virtual-reality and machine-learning features, as well as support for external GPUs. The system's windowing system, Quartz Compositor, supports Metal 2. Media macOS High Sierra adds support for High Efficiency Video Coding (HEVC), with hardware acceleration where available, as well as support for High Efficiency Image File Format (HEIF). Macs with the Intel Kaby Lake processor offer hardware support for Main 10 profile 10-bit hardware decoding, those with the Intel Skylake processor support Main profile 8-bit hardware decoding, and those with AMD Radeon 400 series graphics also support full HEVC decoding. However, whenever an Intel IGP is present, the frameworks will only direct requests to Intel IGP. In addition, audio codecs FLAC and Opus are also supported, but not in iTunes. HEVC hardware acceleration requires a Mac with a sixth-generation Intel processor or newer (late 2015 27-inch iMac, mid 2017 21.5-inch iMac, early 2016 MacBook, late 2016 MacBook Pro or iMac Pro). Other Kernel extensions ("kexts") will require explicit approval by the user before being able to run. The Low Battery notification and its icon were replaced by a flatter modern look. The time service ntpd was replaced with timed for the time synchronization. The FTP and telnet command line programs were removed. Caching Server, File Sharing Server, and Time Machine Server, features that were previously part of macOS Server, are now provided as part of the OS. The screen can now be locked using the shortcut Cmd+Ctrl+Q. The ability to lock screen using a menu bar shortcut activated in Keychain Access preferences has now been removed. The 10.13.4 update added support for external graphics processors for Macs equipped with Thunderbolt 3 ports. The update discontinued support for external graphics processors in 2015 or older Macs, equipped with Thunderbolt 1 and 2 ports. Starting with 10.13.4, when a 32-bit app is opened, users get a one-time warning about its future incompatibility with the macOS operating system. Applications Final Cut Pro 7 Apple announced the original Final Cut Studio suite of programs will not work on High Sierra. Media professionals that depend on any of those programs were advised to create a double boot drive to their computer. Photos macOS High Sierra gives Photos an updated sidebar and new editing tools. Photos synchronizes tagged People with iOS 11. Mail Mail has improved Spotlight search with Top Hits. Mail also uses 35% less storage space due to optimizations, and Mail's compose window can now be used in split-screen mode. Safari macOS High Sierra includes Safari 11. Safari 11 has a new "Intelligent Tracking Prevention" feature that uses machine learning to block third parties from tracking the user's actions. Safari can also block auto playing videos from playing. The "Reader Mode" can be set to always-on. Safari 11 also supports WebAssembly. The last version of Safari that High Sierra supports is 13.1.2. This version has known security issues. Notes The Notes app includes the ability to add tables to notes, and notes can be pinned to the top of the list. The version number was incremented to 4.5. Siri Siri now uses a more natural and expressive voice. It also uses machine learning to understand the user better. Siri synchronizes information across iOS and Mac devices so the Siri experience is the same regardless of the product being used. Messages The release of macOS High Sierra 10.13.5 (and iOS 11.4) introduced support for Messages in iCloud. This feature allows messages to sync across all devices using the same iCloud account. When messages are deleted they are deleted on each device as well, and messages stored in the cloud do not take up local storage on the device anymore. In order to use the feature, the user has to enable two-factor authentication for their Apple ID. Other applications found on macOS 10.13 High Sierra AirPort Utility App Store Archive Utility Audio MIDI Setup Automator Bluetooth File Exchange Boot Camp Assistant Calculator Calendar Chess ColorSync Utility) Console Contacts Dictionary Digital Color Meter Disk Utility DVD Player FaceTime Font Book Game Center GarageBand (may not be pre-installed) Grab Grapher iBooks (now Apple Books) iMovie (may not be pre-installed) iTunes Image Capture Ink (can only be accessed by connecting a graphics tablet to your Mac) Keychain Access Keynote (may not be pre-installed) Migration Assistant Numbers (may not be pre-installed) Pages (may not be pre-installed) Photo Booth Preview QuickTime Player Reminders Script Editor Stickies System Information Terminal TextEdit Time Machine VoiceOver Utility X11/XQuartz (may not be pre-installed) Reception In his September 2017 review of High Sierra, Roman Loyola, the senior editor of Macworld, gave it a provisionally positive review, calling it an "incremental update worthy of your time, eventually." Loyola expressed that the product's most significant draw was its security features, and that beyond this, the most beneficial changes lay in its future potential, saying it "doesn't have a lot of new features that will widen your eyes in excitement. But a lot of the changes are in the background and under the hood, and they lay a foundation for better things to come." Problems macOS High Sierra 10.13.0 and 10.13.1 have a critical vulnerability that allowed an attacker to become a root user by entering "root" as a username, and not entering a password, when logging in. This was fixed in the Security Update 2017-001 for macOS High Sierra v10.13.1. When it was first launched, it was discovered that the WindowServer process had a memory leak, leading to much slower graphics performance and lagging animations, probably due to some last-minute changes in Metal 2. This was fixed in macOS 10.13.1. macOS High Sierra 10.13.4 had an error that caused DisplayLink to stop working for external monitors, allowing only one monitor to be extended. When using two external monitors, they could only be mirrored. Alban Rampon, the Senior Product Manager for DisplayLink, stated on December 24, 2018 that the company was working with Apple to resolve the issue. Release history References External links – official site macOS High Sierra download page at Apple 13 X86-64 operating systems 2017 software Computer-related introductions in 2017

Operating System (OS)

MEPIS MEPIS was a set of Linux distributions, distributed as Live CDs or DVDs that could be installed onto a hard disk drive. MEPIS was started by Warren Woodford and the eponymous company MEPIS LLC. The most popular MEPIS distribution was SimplyMEPIS, which was based primarily on Debian stable, with the last version of SimplyMEPIS being based on Debian 6. It could either be installed onto a hard drive or used as a Live DVD, which made it externally bootable for troubleshooting and repairing many operating systems. It included the KDE desktop environment. History MEPIS was designed as an alternative to SUSE Linux, Red Hat Linux, and Mandriva Linux (formerly Mandrake) which, in the creator Warren Woodford's opinion, were too difficult for the average user. MEPIS's first official release was on May 10, 2003. In 2006, MEPIS made a transition from using Debian packages to using Ubuntu packages. SimplyMEPIS 6.0, released in July 2006, was the first version of MEPIS to incorporate the Ubuntu packages and repositories. SimplyMEPIS 7.0 discontinued the use of Ubuntu binary packages in favor of a combination of MEPIS packaged binaries based on Debian and Ubuntu source code, combined with a Debian stable OS core and extra packages from Debian package pools. Major releases occurred about six months to one year apart until 2013, based mostly on Warren's availability to produce the next version. Variants SimplyMEPIS, designed for everyday desktop and laptop computing. The default desktop environment is KDE-based, although Gnome and/or other GUI-environments can be installed. SimplyMEPIS 11.0 is based on Debian 6 and includes Linux 2.6.36.4, KDE 4.5.1 and LibreOffice 3.3.2, with other applications available from Debian and the MEPIS Community. It was released on May 5, 2011. Development halted during beta testing of Mepis 12. antiX, a fast and lightweight distribution, was originally based on MEPIS for x86 systems in an environment suitable for old computers. It's now based on Debian Stable. MX Linux, a midweight distribution developed in collaboration between antiX and former MEPIS communities which is based on Debian Stable. Name According to Warren Woodford, the name MEPIS is pronounced like "Memphis", with the extra letters removed. Originally, the word "MEPIS" didn't mean anything in particular; it came about by mistake. When Woodford misunderstood a friend over the telephone, he decided to use the name because it was a simple five-letter word and there were no other companies or products with that name. References External links Community website Reviews April 2009 Review of SimplyMEPIS 8.0 Review of SimplyMEPIS 8.0 Beta 5 antiX M-7, The Fat-free Mepis MEPIS AntiX on 450Mhz K6-2, 256Mb Debian-based distributions KDE Operating system distributions bootable from read-only media X86-64 Linux distributions Linux distributions

Operating System (OS)

IPhone OS 2 iPhone OS 2 is the second major release of the iOS mobile operating system developed by Apple Inc., being the successor to iPhone OS 1. It was the first release of iOS to support third-party applications via the App Store. iPhone OS 2.2.1 was the final version of iPhone OS 2. It was succeeded by iPhone OS 3 on June 17, 2009. iPhone OS 2.0 became available on July 11, 2008 with the release of the iPhone 3G. Devices running iPhone OS 1 are upgradable to this version. This version of iOS introduces the App Store, making third-party applications available to the iPhone and iPod Touch. Prior to the public release of iPhone OS 2.0, Apple held a keynote event to announce the iPhone OS Software Development Kit ("SDK") to developers. Originally it was called 1.2. Apps Text YouTube Clock iTunes Calendar Stocks Calculator App Store Photos Maps Notes Camera Weather Settings Videos (iPod Touch exclusive) Dock Phone Mail Safari iPod History iPhone OS 2 was introduced at the Apple Worldwide Developers Conference keynote address on June 9, 2008. iPhone OS 2.0 was released on July 11, 2008. It was released along with the iPhone 3G, and ran on the first-generation iPhone as well. Updates Features App Store The most notable feature of iPhone OS 2 was the App Store. Before this feature was introduced, the only way to install custom applications on the device was via jailbreaking, which is strongly discouraged and unsupported by Apple. There were 500 applications available for download at the launch of the App Store, though this amount has grown dramatically since then. Now, the App Store has more than 4 million apps and games as of 2021. Mail The Mail app had a makeover, having push-emails that provide an always-on capability. It also supports Microsoft Office attachments, as well as iWork attachments. Other new features including support for BCC, multiple email delete, and the ability to select an outgoing email. Contacts The Contacts app now has a new home screen icon that is only available on iPod Touch. Along with the release is the ability to search contacts without being searched one-by-one, as well as SIM contacts import ability. Maps New features were added to the Maps app in the iPhone OS 2.2 software update. Among the features added are the inclusion of Google Street View, directions to public transit and while walking, and the ability to display the address of a dropped pin. Calculator When the device is in landscape mode, the calculator app displays a scientific calculator. Also, the app icon is updated. Settings Settings now had an ability to turn WiFi back on while in Airplane mode, as well as the ability to turn on/off the Location Services within the app. Reception Rene Ritchie at iMore said, "Overall, iPhone Firmware 2.0 is a stunning achievement that really puts the iPhone on par with the Apple II and Mac as one of the great revolutions in modern technology. It takes it beyond simple Phone + iPod, or even smartphone, and makes it the leading contender for the next great shift in computing." However, they criticized it for having stability issues and overall sluggishness. Macworld said, "The iPhone 2.0 software is full of the kind of refinements that you'd expect from a second-generation Apple product. The iPhone OS still isn't perfect, and we wish Apple has addressed some lingering shortcomings, but it's a welcome step-up for what was already arguably the best mobile platform on the market." iPod Touch price The update from iPhone OS 1.x to iPhone OS 2 cost $9.95 for iPod Touch users; it was free for iPhone users. Supported devices iPhone iPhone (1st generation) iPhone 3G iPod Touch iPod Touch (1st generation) iPod Touch (2nd generation) References External links 2008 software Mobile operating systems

Operating System (OS)

Sysinfo Sysinfo is a shareware program written completely in Assembler for the Motorola 68k equipped Amiga computers to benchmark system performance. Sysinfo shows which version of system software is present in ROM, which hardware is present, and which operating mode the hardware uses. Sample output SYSINFO V3.22 An Amiga System Information Program Written in Assembler Nic Wilsson Software P.O. Box 1164 Toowoomba Qld 4350 Australia SYSTEM SOFTWARE INSTALLED LIBRARIES INTERNAL HARDWARE MODES kickstart (512K) $00F80000 V37.350 Clock CLOCK NOT FOUND utility CHIP RAM $00000554 V37.3 DMA/Gfx ECS AGNUS - 2Meg graphics CHIP RAM $00002A68 V37.41 Mode NTSC:Hires keymap CHIP RAM $00006D68 V37.2 Display ECS DENISE layers CHIP RAM $000081D8 V37.9 CPU/MHz 68000 7.16 intuition CHIP RAM $00009984 V37.331 FPU NONE dos CHIP RAM $00011498 V37.45 MMU N/A VBR N/A SPEED COMPARISONS Comment What can I say! Dhrystones 519 You X Horiz KHz 15.72 A600 68000 7MHz 0.98 X EClock Hz 715909 B2000 68000 7MHz 0.74 X Ramsey rev N/A ICache N/A A1200 EC020 14MHz 0.42 XX Gary rev N/A DCache N/A A2500 68020 14MHz 0.25 XXX Card Slot YES IBurst N/A A3000 68030 25MHz 0.11 XXXXX Vert Hz 60 DBurst N/A A4000 68040 25MHz 0.02 XXXXXXXXXXXXXXX Supply Hz 60 CBack N/A CPU Mips 0.54 FPU MFlops N/A QUIT MEMORY BOARDS ICACHE IBURST CBACK Chip Speed vs A600 1.00 DRIVES SPEED PRINT DCACHE DBURST ALL SYSINFO V4.0 An Amiga System Information Program Written in Assembler Contact address SysInfo@d0.se web page http://sysinfo.d0.se SYSTEM SOFTWARE INSTALLED LIBRARIES INTERNAL HARDWARE MODES kickstart (512K) $00F80000 V37.175 Clock CLOCK FOUND utility CHIP RAM $000007CC V37.3 DMA/Gfx STD AGNUS - 512K graphics CHIP RAM $00004258 V37.35 Mode PAL keymap CHIP RAM $00008548 V37.2 Display STD DENISE layers CHIP RAM $000099B8 V37.7 CPU/MHz 68000 7.09 intuition CHIP RAM $00009E5C V37.318 FPU NONE dos CHIP RAM $00012470 V37.44 MMU N/A VBR N/A SPEED COMPARISONS Comment What can I say! Dhrystones 539 You X Horiz KHz 15.60 A600 68000 7MHz 1.00 X EClock Hz 709379 B2000 68000 7MHz 0.77 X Ramsey rev N/A ICache N/A A1200 EC020 14MHz 0.44 XX Gary rev N/A DCache N/A A2500 68020 14MHz 0.26 XXX Card Slot NO IBurst N/A A3000 68030 25MHz 0.11 XXXXX Vert Hz 50 DBurst N/A A4000 68040 25MHz 0.02 XXXXXXXXXXXXXXX Supply Hz 50 CBack N/A Mips 0.56 MFlops N/A QUIT MEMORY BOARDS ICACHE IBURST CBACK Chip Speed vs A600 1.03 DRIVES SPEED PRINT DCACHE DBURST ALL Version history 1990-08-04 v1.4 1990-12-17 v1.94 1991-01-12 v1.98 1991-11-19 v2.51 1991-12-11 v2.53 1991-12-31 v2.56 1991-06-21 v2.22 1991-10-25 v2.40 1992-03-10 v2.60 1992-03-21 v2.62 1992-04-12 v2.69 1992-09-01 v3.01 1993-01-14 v3.11 1993-03-27 v3.18 1993-11-07 v3.24 2012-11-07 v4.0 2019-07-13 v4.2 2019-09-27 v4.3 2020-11-11 v4.4 See also SysSpeed Dhrystone FLOPS Kickstart (Amiga) Intuition (Amiga) AmigaDOS Amiga models and variants Instructions per second (IPS) Amiga Chip RAM Amiga custom chips (OCS, ECS, Agnus, Denise, Ramsey, Gary, etc.) Motorola 68000 family References Benchmarks (computing) Amiga software

Operating System (OS)

System 2000 (software) System 2000 (S2K) is a hierarchical database management system (DBMS). Although not a relational database, S2K does have SQL support. In 2007 it was noted that, while still 'running on systems cranking away in back rooms across the U.S.' it has a problem: "there's little curriculum coverage anymore at universities teaching computer science." Overview System 2000 originated as software for the IBM mainframe environment. It could operate in batch processing mode or be used via CICS. It competed with Cincom's Total, Software AG's ADABAS, Applied Data Research's DATACOM/DB, Computer Corporation of America's Model 204, and IBM Information Management System (IMS) and DL/I. Unisys and CDC versions were subsequently released, as was an interface to SAS. Programmers could access its Data manipulation language (DML) via a precompiler; these existed for COBOL, FORTRAN, and ASSEMBLY Language. Statements written in S2K's Procedural Language could be intermixed with these languages: the 3 character code "*PL" (in columns 1-3) identified these statements as intended for the precompiler (also referred to as a preprocessor). History System 2000 was developed in 1970. SAS Institute acquired S2K from Intel in 1984, which had acquired it from MRI Systems Corporation in 1979. MRI was founded by Robert L. Brueck. References Database management systems High-level programming languages

Operating System (OS)

XFree86 XFree86 is an implementation of the X Window System. It was originally written for Unix-like operating systems on IBM PC compatibles and was available for many other operating systems and platforms. It is free and open source software under the XFree86 License version 1.1. It was developed by the XFree86 Project, Inc. The lead developer was David Dawes. The last released version was 4.8.0, released December 2008. The last XFree86 CVS commit was made on May 18, 2009; the project was confirmed dormant in December 2011. For most of the 1990s and early 2000s, the project was the source of most innovation in X and was the de facto steward of X development. Until early 2004, it was almost universal on Linux and the BSDs. In February 2004, with version 4.4.0, The XFree86 Project began distributing new code with a copyright license that the Free Software Foundation considered GPL incompatible. Most open source operating systems using XFree86 found this unacceptable and moved to a fork from before the license change. The first fork was the abortive Xouvert, but X.Org Server soon became dominant. Most XFree86 developers also moved to X.Org. Usage While XFree86 was widely used by most Unix-like computer operating systems before its license change with version 4.4.0, it has since then been superseded by X.org and is used rarely nowadays. The last remaining operating system distribution to use it was NetBSD, which shipped some platforms with 4.5.0 by default until removing it as obsolete in 2015. and later releases use X.org by default on various ports (including i386 and amd64), and X.org is available through NetBSD pkgsrc for architectures for which XFree86 remains the default because of better support. , the netbsd-7 branch and release were the last to potentially contain XFree86, and XFree86 was completely removed before netbsd-8 branch and release in 2018. Architecture The XFree86 server communicates with the host operating system's kernel to drive input and output devices, with the exception of graphics cards. These are generally managed directly by XFree86, so it includes its own drivers for all graphic cards a user might have. Some cards are supported by vendors themselves via binary-only drivers. Since version 4.0, XFree86 has supported certain accelerated 3D graphics cards via the GLX and DRI extensions. Also in the version 4.0, XFree86 moved to a new driver model, from one X server binary per driver to a unique X server capable of loading several drivers at a time. Because the server usually needs low level access to graphics hardware, on many configurations it needs to run as the superuser, or a user with UID 0. However, on some systems and configurations it is possible to run the server as a normal user. It is also possible to use XFree86 in a framebuffer device, which in turn uses a kernel graphics card driver. On a typical POSIX-system, the directory /etc/X11 includes the configuration files. The basic configuration file is /etc/X11/XF86Config (or XF86Config-4) that includes variables about the screen (monitor), keyboard and graphics card. The program xf86config is often used, although xf86cfg also comes with the XFree86 server and is certainly friendlier. Many Linux distributions used to include a configuration tool that was easier to use (such as Debian's debconf) or autodetected most (if not all) settings (Red Hat Linux and Fedora's Anaconda, SuSE's YaST and Mandrake Linux used to choose this path). History Early history and naming The project began in 1992 when David Wexelblat, Glenn Lai, David Dawes and Jim Tsillas joined forces addressing bugs in the source code of the X386 X display server (written by Thomas Roell), as contributed to X11R5. This version was initially called X386 1.2E. As newer versions of the (originally freeware) X386 were being sold under a proprietary software license by SGCS (of which Roell was a partner), confusion existed between the projects. After discussion, the project was renamed XFree86, as a pun (compare X-three-eighty-six to X-free-eighty-six). Roell has continued to sell proprietary X servers, most recently under the name Accelerated-X. Rise with Linux As Linux grew in popularity, XFree86 rose with it, as the main X project with drivers for PC video cards. By the late 1990s, official X development was moribund. Most technical advancement was happening in the XFree86 project. In 1999, XFree86 was sponsored onto X.Org (the official industry consortium) by various hardware companies interested in its use with Linux and its status as the most popular version of X. 2002: Growing dissent within the project By 2002, while Linux's popularity, and hence the installed base of X, surged, X.Org was all but inactive; active development was largely carried out by XFree86. However, there was considerable dissent within XFree86. XFree86 used to have a Core Team which was made up of experienced developers, selected by other Core Team members for their merits. Only the members of this Core Team were allowed to commit to CVS. This was perceived as far too cathedral-like in its development model: developers were unable to get commit rights quickly and vendors ended up maintaining extensive patches. A key event was Keith Packard losing his commit rights. Hours before the feature freeze window for XFree86 4.3.0 started, he committed the XFIXES extension (which he developed himself), without prior discussion or without review within the Core Team. The Core Team decided to remove Keith's commit access, but without removing him from the Core Team itself, and the XFIXES extension was backed out six weeks later. 2003: The fork and the disbanding of the Core Team In March 2003, the Core Team claimed that Packard had been trying to fork the XFree86 project by working inside the project while trying to attract core developers to a new X Server project of his own making. Packard denied this had been his aim, but some emails were provided as evidence otherwise. Keith Packard was subsequently expelled from the Core Team. A short time later, Packard created xwin.org, which mainly served as a meeting point for cultivating the XFree86 fork. The rest of the year, many of the developers that were still active at XFree86 went over to the project that was being set up at the freedesktop.org and X.org domains. By the end of the year, due to dwindling active membership and limited remaining development capacity, the XFree86 Core Team voted to disband itself. 2004: Licensing controversy Versions of XFree86 up to and including some release candidates for 4.4.0 were under the MIT License, a permissive, non-copyleft free software license. In February 2004, XFree86 4.4 was released with a change to the XFree86 license, by adding a credit clause, similar to that in the original BSD license, but broader in scope. The newer terms are referred to as the XFree86 License 1.1. Many projects relying on XFree86 found the new license unacceptable, and the Free Software Foundation considers it incompatible with the version 2 of the GNU General Public License, though compatible with version 3. The XFree86 Project states that the license is "as GPL compatible as any and all previous versions were", but does not mention which version or versions of the GPL this is valid for. Some projects made releases (notably OpenBSD 3.5 and 3.6, and Debian 3.1 "Sarge") based on XFree86 version 4.4 RC2, the last version under the old license. Most operating systems incorporating XFree86 (including later versions of OpenBSD and Debian) migrated to the X.Org Server. The last code commit was in 2009; the project was confirmed dormant in 2011 and the website was last updated in 2014, commemorating the-then 22th anniversary. Forks of XFree86 Xwin Shortly after he was expelled from the XFree86 Core Team, Keith Packard started setting up xwin.org. While this was claimed to be the fork of XFree86, Keith Packard later refined this to "a forum for community participation in X". Xwin saw a lot of activity in the first two months after the announcements, but most of the activity was happening behind the scenes, and Keith moved his own development to freedesktop.org. Xouvert Xouvert was later also hailed as the first XFree86 fork in August 2003. Even though releases were announced for October 2003 and April 2004, no releases were made. The last status change was made in March 2004 and it was communicated that there were delays in setting up a revision control system. X.Org The X.Org Server became the official reference implementation of X11. The first version, X11R6.7.0, was forked from XFree86 version 4.4 RC2 to avoid the XFree86 license changes, with X11R6.6 changes merged in. Version X11R6.8 added many new extensions, drivers and fixes. It is hosted by and works closely with corporate-sponsored freedesktop.org. Most of the open-source Unix-like operating systems have adopted the X.Org Server in place of XFree86, and most of the XFree86 developers have moved to X.Org. Release history See also DirectFB XFree86 logfile XFree86 Modeline XF86Config References Notes Announcing the release of XFree86 1.1 Announcing the release of XFree86 1.2 Announcing the release of XFree86 1.3 xfree86/CHANGELOG.R5?rev=1.1.1.1 X Marks the Spot: Looking back at X11 Developments of Past Year (Oscar Boykin, OSNews February 25, 2004) — the licensing controversy and forks The History of XFree86: Over a Decade of Development (Michael J. Hammel, Linux Magazine, December 2001) Some perspective from the cheap seats ... (David Wexelblat, March 20, 2003) — on why Keith Packard was sacked from the core team A Call For Open Governance Of X Development (Keith Packard, March 21, 2003) XFree86 dust-up questions X11 model (Andrew Orlowski, The Register, March 21, 2003) External links Project home page Free windowing systems X servers

Operating System (OS)

Windows XP editions Windows XP has been released in several editions since its original release in 2001. Windows XP is available in many languages. In addition, add-ons translating the user interface are also available for certain languages. Home and Professional The first two editions released by Microsoft are Windows XP Home Edition, designed for home users, and Windows XP Professional, designed for business and power users. Windows XP Professional offers a number of features unavailable in the Home Edition, including: The ability to become part of a Windows Server domain, a group of computers that are remotely managed by one or more central servers. An access control scheme that allows specific permissions on files to be granted to specific users under normal circumstances. However, users can use tools other than Windows Explorer (like cacls or File Manager), or restart to Safe Mode to modify access control lists. Remote Desktop server, which allows a PC to be operated by another Windows XP user over a local area network or the Internet. Offline Files and Folders, which allow the PC to automatically store a copy of files from another networked computer and work with them while disconnected from the network. Encrypting File System, which encrypts files stored on the computer's hard drive so they cannot be read by another user, even with physical access to the storage medium. Centralized administration features, including Group Policies, Automatic Software Installation and Maintenance, Roaming User Profiles, and Remote Installation Services (RIS). Internet Information Services (IIS), Microsoft's HTTP and FTP Server. Support for two physical central processing units (CPUs). (Because the number of CPU cores and hyper-threading capabilities on modern CPUs are considered to be part of a single physical processor, multicore CPUs are supported using XP Home Edition.) Windows Management Instrumentation Console (WMIC): WMIC is a command-line tool designed to ease WMI information retrieval about a system by using simple keywords (aliases). The ability to switch hard disk storage type from Basic to Dynamic and vice versa. Edition N In March 2004, the European Commission fined Microsoft €497 million (£395 million or $784 million) and ordered the company to provide a version of Windows without Windows Media Player. The Commission concluded that Microsoft "broke European Union competition law by leveraging its near monopoly in the market for PC operating systems onto the markets for work group server operating systems and for media players". After unsuccessful appeals in 2004 and 2005, Microsoft reached an agreement with the Commission where it would release a court-compliant version, Windows XP Edition N. This version does not include the company's Windows Media Player but instead encourages users to pick and download their own media player. Microsoft wanted to call this version Reduced Media Edition, but EU regulators objected and suggested the Edition N name, with the N signifying "not with Media Player" for both Home and Professional editions of Windows XP. Because it is sold at the same price as the version with Windows Media Player included, Dell, Hewlett-Packard, Lenovo and Fujitsu Siemens have chosen not to stock the product. However, Dell did offer the operating system for a short time. Consumer interest has been low, with roughly 1,500 units shipped to OEMs, and no reported sales to consumers. The N editions of Windows XP also do not include Windows Movie Maker, but Microsoft has made this available as a separate download. K & KN In December 2005, the Korean Fair Trade Commission ordered Microsoft to make available editions of Windows XP and Windows Server 2003 that do not contain Windows Media Player or Windows Messenger. Like the European Commission decision, this decision was based on the grounds that Microsoft had abused its dominant position in the market to push other products onto consumers. Unlike that decision, however, Microsoft was also forced to withdraw the non-compliant versions of Windows from the South Korean market. The K and KN editions of Windows XP Home Edition and Professional Edition were released in August 2006, and are only available in English and Korean. Both editions contain links to third-party instant messenger and media player software. Home Edition ULCPC This edition of Windows XP Home is intended for sale with certain "low-cost" netbooks and will appear labeled as "Windows XP Home Edition ULCPC" on the back of the netbook (with "ULCPC" standing for "ultra-low-cost personal computer"). This edition contains a regular license of Windows XP Home Edition with Service Pack 3 included. Professional Blade PC Edition This version comes preinstalled on OEM solutions providing desktops on Blade PC hardware. In addition to a copy of Windows XP Professional, it includes a Remote Desktop License. Starter edition Windows XP Starter is a lower-cost version of Windows XP available in Thailand, Vietnam, Turkey, Indonesia, India, Philippines, Russia, Colombia, Brazil, Argentina, Peru, Bolivia, Chile, Mexico, Ecuador, Uruguay, Malaysia, and Venezuela. It is similar to Windows XP Home, but is limited to low-end hardware, can only run 3 programs at a time, and has some other features either removed or disabled by default. According to a Microsoft press release, Windows XP Starter is "a low-cost introduction to the Microsoft Windows XP operating system designed for first-time desktop PC users in developing countries." Specialization The Starter edition includes some special features for certain markets where consumers may not be computer literate. Not found in the Home Edition, these include localised help features for those who may not speak English, a country-specific computer wallpaper and screensavers, and other default settings designed for easier use than typical Windows XP installations. The Malaysian version, for example, contains a desktop background of the Kuala Lumpur skyline. In addition, the Starter edition also has some unique limitations to prevent it from displacing more expensive versions of Windows XP. Only three applications can be run at once on the Starter edition, and each application may open a maximum of three windows. The maximum screen resolution is 1024×768, and there is no support for workgroup networking or domains. In addition, the Starter edition is licensed only for low-end processors like Intel's Celeron or AMD's Duron and Sempron. There is also a 512 MB limit on main memory and a 120 GB disk size limit. Microsoft has not made it clear, however, if this is for total disk space, per partition, or per disk. There are also fewer options for customizing the themes, desktop, and taskbar. Market adoption On October 9, 2006, Microsoft announced that they reached a milestone of 1 million units of Windows XP Starter sold. In the mass market, however, the Starter edition has not had much success. In many markets where it is available, pirated versions of higher end versions of Windows are more popular than their legal counterparts. In these markets, non-genuine copies of XP Professional can be obtained at a mall. These stores typically charge only for the amount of the CDs/DVDs taken up by the files, not the original retail value. Unlicensed copies of Windows XP Professional typically cost 70¢, since it only uses 1 CD, compared to around $30 for a properly licensed copy of XP Starter. Media Center Edition This edition, which was code-named "Freestyle" during its development, was first released in September 2002. The initial release was available solely in conjunction with computers that included media center capabilities, and could not be purchased separately. The first major update was released in 2004 and distributed by Tier 1 OEMs who had previously sold Windows XP Media Center Edition PC, and then updated again in 2005, which was the first edition available for System Builders. Many of the features of Windows XP Media Center Edition 2005 (including screen dancers, auto playlist DJ, and high end visual screen savers) were taken from the Windows XP Plus! packages. These were originally shipped as add-ons to Windows XP to enhance the users experience of their Windows XP machine. Releases A preview version of Windows XP Media Center Edition from Microsoft's eHome division, was shown as CES 2002, with the final version released in July 2002. Windows XP Media Center Edition ("Freestyle", July 2002) This was the original release. Updates to this release added features such as FM radio tuning. This release combined with updates is sometimes referred to as Windows XP Media Center Edition 2003. Windows XP Media Center Edition 2004 ("Harmony", September 2003) Windows XP Service Pack 2 upgrades earlier versions of MCE to this one. Windows XP Media Center Edition 2005 ("Symphony", October 2004) is the first edition of MCE available to non-Tier 1 system builders. Among other things it includes support for Media Center Extenders, and CD/DVD-Video burning support. Update Rollup 2 for Windows XP Media Center Edition 2005 ("Emerald", October 2005) is a major update to MCE 2005 (Symphony) and was a recommended download. It adds support for the Xbox 360 as a media center extender, DVB-T broadcasts, and support for two ATSC tuner cards. After the 2005 release, Microsoft focused their efforts on building new media center features into "Home Premium" and "Ultimate" editions of Windows Vista and Windows 7, which have Windows Media Center built-in and, unlike the releases of Windows XP Media Center Edition, were available for retail purchase without the necessary hardware. Features The most notable feature unique to this edition is the Windows Media Center, which provides a large-font, remotely accessible interface ("10-foot user interface") for television viewing on the computer as well as recording and playback, a TV guide, DVD playback, video playback, photo viewing, and music playback. Unlike competing commercial digital video recorder products, Microsoft does not charge a monthly subscription fee for its Media Center TV guide service. Due to strict hardware requirements, Microsoft did not sell Media Center Edition in retail markets alongside the Home and Professional editions. Microsoft only distributes it to MSDN subscribers and OEM System Builders in certain countries. Consumers generally purchase Media Center pre-installed on a new computer, or from a reseller that sells OEM versions of Microsoft software. Media Center Edition was the only consumer-oriented edition of Windows XP that was updated with new features on an annual basis during the five-year development of Windows Vista. The MCE 2005 release, for example, includes an update to Windows Movie Maker that supports burning DVDs, a new visual style called "Royale", support for Media Center Extenders, and SoundSpectrum's G-Force sound visualizations. Microsoft also released its own remote control, receiver and infrared blaster with MCE 2005. A new specially designed wireless computer keyboard for MCE 2005 was released September 2005. Using Media Center Extenders or the Xbox 360, Media Center Edition is also able to connect and stream recorded TV, music and pictures, over a network connection. Media Center Edition retains most of the features included in Windows XP Professional as it is simply an add-on to Professional, installed when provided with a valid MCE product key during setup. All Professional features have been left in, including Remote Desktop and the Encrypting File System, however the ability to join an Active Directory domain has been removed as it is marketed as a home product with no need for domain support. One value in the registry is all that is needed to circumvent this restriction; if the installation of MCE 2005 is an in-place upgrade from a previous version already joined to a domain, this ability is retained, unless a user uses a Windows Media Center Extender: in this case, such ability is lost and cannot be restored. Presumably, Microsoft introduced this limit because Media Center Extender devices, introduced in this version, rely on the Fast User Switching component, but this component must be disabled in order to join a domain. Hardware requirements Media Center has higher hardware requirements than other editions of Windows XP. MCE 2005 requires at least a 1.6 GHz processor, DirectX 9.0 hardware-accelerated GPU (ATI Radeon 9 series or nVidia GeForce FX series or higher), and 256 MB of system RAM. Some functionality, such as Media Center Extender support, use of multiple tuners, or HDTV playback/recording carries higher system requirements. Media Center is much more restricted in the range of hardware that it supports than most other software DVR solutions. Media Center tuners must have a standardized driver interface, and they (originally) required a hardware MPEG-2 encoder, closed caption support, and a number of other features. Media Center remote controls are standardized in terms of button labels and functionality, and, to a degree, general layout. Tablet PC Edition This edition is intended for specially designed notebook/laptop computers called tablet PCs. Windows XP Tablet PC Edition is compatible with a pen-sensitive screen, supporting handwritten notes and portrait-oriented screens. Except for MSDN and Volume License subscribers, Windows XP Tablet Edition could not be purchased separately. Tablet PC Edition is a superset of Windows XP Professional, the difference being tablet functionality, including alternate text input (Tablet PC Input Panel) and basic drivers for support of tablet PC specific hardware. Requirements to install Tablet PC Edition include a tablet digitizer or touchscreen device, and hardware control buttons including a Ctrl-Alt-Delete shortcut button, scrolling buttons, and at least one user-configurable application button. There have been two releases: Windows XP Tablet PC Edition – The original version released in November 2002. Windows XP Tablet PC Edition 2005 – The Tablet PC version released in August 2004 (codenamed Lonestar) as part of Windows XP Service Pack 2. The 2005 edition is available as a service pack upgrade, or as a new OEM version. Service Pack 2 for Windows XP includes Tablet PC Edition 2005 and is a free upgrade. This version brought improved handwriting recognition and improved the Input Panel, allowing it to be used in almost every application. The Input Panel was also revised to extend speech recognition services (input and correction) to other applications. Included software Windows XP Tablet PC Edition is based on Windows XP Professional and includes all the software features provided in it. In addition, it includes some of the following components: Tablet PC Input Panel Windows Journal Sticky Notes InkBall Energy Blue theme The following downloadable packs released by Microsoft add more functionality: Microsoft Experience Pack for Tablet PC Ink Art Ink Crossword Ink Desktop Media Transfer Snipping Tool 2.0 Microsoft Education Pack for Tablet PC Ink Flash Cards Equation Writer GoBinder Lite Hexic Deluxe Technology Windows XP Tablet PC Edition utilizes the Ink object as a means of data input and storage. This is a data type created as part of the Windows XP Tablet PC Edition API that allows users to manipulate and process handwritten data, including recognition results and, in some cases, the pressure information for each part of the stroke. Properties of Ink can be changed in much the same way as properties of other objects, and the data can be saved to allow future reference. Many applications referencing the Ink object also allow handwritten notes to be filtered and searched through, based on the recognition results stored when Ink is saved. Integrated with the operating system is a Tablet PC Input Panel (TIP) which allows handwriting to be converted into text for use in most non-full-screen applications. The integrated handwriting recognition in Windows XP Tablet PC Edition 2005 can recognize print, cursive, or mixed writing. Accuracy can be increased by configuring the recognizer to expect left-handed writing or right-handed writing. Recognition in a variety of languages is available with the install of a recognizer pack. The handwriting engine cannot be trained to recognize a particular handwriting style, so the user must modify their handwriting to be better recognized by the system in order to use this feature effectively. Speech recognition functionality is also incorporated into the Tablet Input Panel. Compared to previous versions, a substantially improved speech recognition engine version 6 (which also ships with Office 2003) and a tutorial, microphone wizard and training modules are included. It is possible to dictate text using speech in certain supported applications and control the Windows GUI and applications using speech, although the accuracy improvements further made in Windows Vista surpass these features. An update for Windows XP Tablet PC Edition containing Ink Analysis and StylusInput API support introduced in Windows Vista is also available. Subscription and pre-paid editions In 2006, Microsoft made available two additional editions of Windows XP Home Edition for hardware manufacturers that wanted to provide subscription-based or pay as you go-based models for selling computers. These editions, named Windows XP Home Edition for Subscription Computers, and Windows XP Home Edition for Prepaid Computers respectively, are part of the "Microsoft FlexGo" initiative, described in a company-issued press release as, "[making] PCs more accessible by dramatically reducing the entry cost and enabling customers to pay for their computer as they use it, through the purchase of prepaid cards. Market trials are starting first in emerging markets where inadequate access to consumer credit, unpredictable income and high entry costs prevent many consumers from purchasing a computer." These editions were targeted towards emerging markets such as India, Brazil, Hungary and Vietnam. Both editions contain additional components that enforce the subscription models via metering. The metering is typically enforced with a hardware component to prevent tampering. The installation of Windows operates in "normal mode", "Limited Access Mode", or "Hardware Locked Mode" depending on the state of the subscription. When a computer has a positive time balance, it operates in "normal mode" and functions as a regular Windows XP Home Edition machine. When the time balance expires, the machine will then operate in "Limited Access Mode" for an amount of time set by the hardware manufacturer (five hours by default) before entering "Hardware Locked Mode". In Limited Access Mode, the screen uses high-contrast and low-resolution display settings, and in Hardware Locked Mode, the operating system is disabled entirely, and a message is displayed on boot-up with instructions on how to re-enable the machine. 64-bit editions Two distinct editions of Windows XP were released to support 64-bit hardware. Windows XP 64-Bit Edition Windows XP 64-Bit Edition was designed to run on Intel Itanium family of microprocessors in their native IA-64 mode. Two versions of Windows XP 64-Bit Edition were released: Windows XP 64-Bit Edition for Itanium systems, Version 2002 – Based on Windows XP codebase, was released simultaneously alongside the 32-bit (IA-32) version of Windows XP on October 25, 2001. Windows XP 64-Bit Edition, Version 2003 – Based on Windows Server 2003 codebase (which added support for the Itanium 2 processor), was released on March 28, 2003. This edition was discontinued in January 2005, after Hewlett-Packard, the last distributor of Itanium-based workstations, stopped selling Itanium systems marketed as 'workstations'. As of July 2005, Windows XP 64-Bit Edition is no longer supported, and no further security updates were made available. Windows XP 64-Bit Edition was not marketed as the Itanium version of Microsoft's other Windows XP editions, but, instead, as a separate edition made solely for the Itanium processor and its 64-bit instructions. It is mostly analogous to Windows XP Professional, but numerous older technologies, such as DAO, Jet database, NTVDM, and Windows on Windows, are no longer present, so support for MS-DOS and Win16 applications is absent. The original version also lacks most media applications, such as Windows Media Player, NetMeeting, Windows Movie Maker, and integrated CD burning, although Windows Media Player and NetMeeting were added in the 2003 version. Similar to the ability of previous alternate architecture ports of Windows (Windows NT 4.0 for PowerPC, MIPS R4x00, and Alpha) to run 16-bit x86 code via Windows on Windows, Windows XP 64-Bit Edition can run standard x86 32-bit applications through its WOW64 (Windows-on-Windows 64-bit) emulation layer. While the original Itanium processor contains an on-chip IA-32 decoder, it was deemed far too slow for serious use (running at about 400 MHz), so Microsoft and Intel wrote a software 32 to 64-bit translator dubbed the IA-32 Execution Layer. It allows real time translation of x86 32-bit instructions into IA-64 instructions, allowing 32-bit applications to run (albeit significantly more slowly than native code). Windows XP Professional x64 Edition This edition supports the x86-64 extension of the Intel IA-32 architecture. x86-64 is implemented by AMD as "AMD64", found in AMD's Opteron, Athlon 64 chips (and in selected Sempron processors), and implemented by Intel as "Intel 64" (formerly known as IA-32e and EM64T), found in some of Intel's Pentium 4 and most of Intel's later chips. It was released on April 25, 2005. Windows XP Professional x64 Edition uses version 5.2.3790.1830 of core operating system binaries, the same version used by Windows Server 2003 SP1 as they were the latest versions during the operating system's development. Even service packs and updates for Windows XP x64 and Windows Server 2003 x64 are distributed in unified packages, much in the manner as Windows 2000 Professional and Server editions for x86. During the initial development phases (2003–2004), Windows XP Professional x64 Edition was named Windows XP 64-Bit Edition for x86 Extended Systems and later, Windows XP 64-Bit Edition for Extended Systems, as opposed to 64-Bit Edition for Itanium Systems. Service packs The RTM version of Windows XP Professional x64 Edition is based on Windows Server 2003 Service Pack 1 codebase. For the same reason, Service Pack 2 for Windows XP x64 Edition, released on the March 13, 2007, is not the same as Service Pack 2 for 32-bit versions of Windows XP. In fact, due to the earlier release date of the 32-bit version, many of the key features introduced by Service Pack 2 for 32-bit (x86) editions of Windows XP were already present in the RTM version of its 64-bit (x86-64) counterpart. Service Pack 2 is the first and last released service pack for Windows XP Professional x64 Edition. Software compatibility Windows XP Professional x64 Edition uses a technology named Windows-on-Windows 64-bit (WOW64), which permits the execution of 32-bit x86 applications. It was first employed in Windows XP 64-Bit Edition (for the Itanium), but then reused for the "x64 Editions" of Windows XP and Windows Server 2003. Since the x86-64 architecture includes hardware-level support for 32-bit instructions, WOW64 switches the processor between 32- and 64-bit modes. According to Microsoft, 32-bit software running under WOW64 has a similar performance when executing under 32-bit Windows, but with fewer threads possible and other overheads. All 32-bit processes are shown with *32 in the task manager, while 64-bit processes have no extra text present. Although 32-bit applications can be run transparently, the mixing of the two types of code within the same process is not allowed. A 64-bit application cannot link against a 32-bit library (DLL) and, similarly, a 32-bit application cannot link against a 64-bit library. This may lead to the need for library developers to provide both 32- and 64-bit binary versions of their libraries. Windows XP x64 Edition includes both 32- and 64-bit versions of Internet Explorer 6, in order to allow for the possibility that some third-party browser plugins or ActiveX controls may not yet be available in 64-bit versions. Older 32-bit drivers and services are not supported by 64-bit Windows, but video and audio codecs such as XviD or OggDS (which are 32-bit DLLs), are supported as long as the media player that uses them is 32-bit as well. 64-bit Windows does not include NTVDM or Windows on Windows, so there is no native support for the execution of MS-DOS or 16-bit Windows applications, such as those written for Windows 3.1. Advantages The primary benefit of moving to 64-bit is the increase in the maximum allocatable virtual memory. A single standard process on a 32-bit Windows operating system is limited to a total of 2,093,056 kilobytes (2GB minus one 4KB page), while large address aware 32-bit processes can allocate up to 4GB. Windows XP x64 can support much more memory; although the theoretical memory limit a 64-bit computer can address is about 16exabytes, Windows XP x64 is limited to 128GB of physical memory and 8 terabytes of virtual memory per process while the practical limit is usually the size of the pagefile. Windows XP Professional x64 Edition and Windows XP 64-bit Edition Version 2003 are the only releases of Windows XP to include Internet Information Services 6.0, which matches the version shipped with Windows Server 2003; other versions of XP include 5.1. 64-bit versions of Windows XP are also immune to certain types of viruses and malware that target 32-bit systems, since most system files are 64-bit. The extra registers of the x86-64 architecture can result in performance improvements in certain kinds of applications, but more often than not, will result in a slight decrease in performance when compared to the same application implemented in 32 bit x86 code running on Windows XP 32 bit editions. Editions for embedded systems Microsoft has released a number of editions of Windows XP that are targeted towards developers of embedded devices, for use in specific consumer electronics, set-top boxes, kiosks/ATMs, medical devices, arcade video games, point-of-sale terminals, and Voice over Internet Protocol (VoIP) components. These editions all belong to Windows Embedded subfamilies. Windows XP for Embedded Systems Windows XP for Embedded Systems is binary identical to Windows XP Professional, but is licensed only for embedded devices. Windows XP Embedded Windows XP Embedded, commonly abbreviated "XPe", is a componentized version of the Professional edition of Windows XP. An original equipment manufacturer is free to choose only the components needed thereby reducing operating system footprint and also reducing attack area as compared with XP Professional. Unlike Windows CE, Microsoft's operating system for portable devices and consumer electronics, XP Embedded provides the full Windows API, and support for the full range of applications and device drivers written for Microsoft Windows. The system requirements state that XPe can run on devices with at least 32 MB Compact Flash, 32 MB RAM and a P-200 microprocessor. XPe was released on November 28, 2001. As of October 2008, the newest release is Windows XP Embedded Service Pack 3. The devices targeted for XPe have included automatic teller machines, arcade games, slot machines, cash registers, industrial robotics, thin clients, set-top boxes, network attached storage (NAS), time clocks, navigation devices, railroad locomotives, etc. Custom versions of the OS can be deployed onto anything but a full-fledged PC; even though XPe supports the same hardware that XP Professional supports (x86 architecture), licensing restrictions prevent it from being deployed on to standard PCs. However, Microsoft has made some exceptions to this rule, allowing XPe alongside a standard OEM install of Windows. Some Dell notebooks contain an embedded XP installation as part of the MediaDirect 2.0 feature, and they were also found on some Acer ones as well as the Samsung Q1. Windows Embedded Standard 2009 succeeded XPe in the second half of 2008. Windows Embedded Standard 2009 is derived from Windows XP Embedded since Microsoft at the time of its development did not have a componentized version of Windows Vista. Windows Embedded Standard 2009 includes Silverlight, .NET Framework 3.5, Internet Explorer 7, Windows Media Player 11, RDP 6.1, Network Access Protection, Microsoft Baseline Security Analyzer and support for being managed by Windows Server Update Services and System Center Configuration Manager. It can be installed on top of Windows XP/Server 2003, Vista/Server 2008. Windows Embedded Standard 7 has succeeded Windows Embedded Standard 2009 in April 2010 and is a componentized version of Windows 7. Features Write filters XPe includes components known as write filters, which can be used to filter out disk writes. The volumes can be marked as read-only using these filters and all writes to it can be redirected. Applications in user mode are unaware of this write filtering. XPe ships with two write filters: Enhanced Write Filter (EWF): Protects a system at volume level. It redirects all disk writes to a protected drive, to RAM or a separate disk. EWF is extremely useful when used in thin clients that have flash memory as their primary boot source. File Based Write Filter (FBWF): Allows the configuration of individual files as read/write on a protected volume USB boot XPe adds a USB boot option to Windows. An XPe embedded device can be configured to boot from a USB drive. CD boot An XPe device can be configured to boot from a CD-ROM. This allows the device to boot without the requirement of having a physical hard disk drive as well as provides a "fresh boot" every time the image is booted (a property inherited by the fact that the operating system is being booted from read-only media). One drawback to this technology is updating or servicing the image requires the complete process of setting up the runtime image to be completed once again from start to end. Network boot An XPe device can be configured to boot from a properly configured network. Synonymous to CD boot, network boot removes the requirement of having the physical hard drive as well as providing the "fresh boot" behavior. One bonus to Network Boot though is the ability to service the already setup image. Once the image is updated the image is simply posted to the RIS Server and once clients are rebooted they will receive the updated image. Windows Embedded for Point of Service Windows Embedded for Point of Service (WEPOS) is a specialization of Windows XP Embedded. It was released on May 25, 2005, and focuses on the point of sale device market, such as fuel pumps, self checkout stations, automated teller machines and cash registers. It is not available for purchase directly from Microsoft, but is instead licensed to original equipment manufacturers. Windows Embedded POSReady 2009 succeeded WEPOS in January 2009. Windows Embedded POSReady 2009 is derived from WEPOS since Microsoft at the time of its development did not have a componentized version of Windows Vista. Windows Embedded POSReady 7 has succeeded Windows Embedded POSReady 2009 in July 2011 and is based on Windows 7 SP1. Windows Fundamentals for Legacy PCs In July 2006, Microsoft introduced a "thin-client" variant of Windows XP Embedded called Windows Fundamentals for Legacy PCs, which targets older machines (as early as the original Pentium). It is only available to Software Assurance customers. It is intended for those who would like to upgrade to Windows XP to take advantage of its security and management capabilities, but cannot afford to purchase new hardware. Windows Thin PC has succeeded Windows Fundamentals for Legacy PCs in June 2011 and is based on Windows Embedded Standard 7 SP1. References External links Windows XP Media Center Edition home page Windows XP Professional x64 Edition home page Embedded Windows team blog Windows XP Embedded Home Page Windows XP

Operating System (OS)

Acorn System 1 The Acorn System 1, initially called the Acorn Microcomputer (Micro-Computer), was an early 8-bit microcomputer for hobbyists, based on the MOS 6502 CPU, and produced by British company Acorn Computers from 1979. The main parts of the system were designed by then-Cambridge-undergraduate student Sophie Wilson, with a cassette interface design by Steve Furber. It was Acorn's first product, and was based on an automated cow feeder. It was a small machine built on two Eurocard-standard circuit boards and it could be purchased ready-built or in kit form. one card (shown right) with the I/O part of the computer: a LED seven segment display, a 25-key keypad (hex+function keys), and a cassette CUTS interface (the circuitry to the left of the keypad) the second card (the computer board - see below), which included the CPU, RAM/ROM memory, and support chips the two boards were interconnected by a semi-flexible, multi-conductor cable, known by its commercial name 'Spectra Strip' the whole assembly was held together by four 2.5mm × 20mm nylon screws and clear plastic spacing tubes for rigidity. Main Components (left to right) Top Row: INS8154 RAMIO Integrated Circuit (for keyboard and display), 6502 CPU, 2 × 2114 1024×4 RAM, 2 × 74S571 512×4 PROM, RAM/ROM expansion socket, second INS8154 for peripheral expansion (optional extra with the kit version). Bottom row: 1 MHz clock crystal, 4 × TTL logic chips providing address decoding for the memory and I/O expansion, 5V regulator. The smaller empty socket in the middle of the board was used to set the memory map of the RAM, ROM and I/O expansion by fitting or soldering wires between various positions according to the instructions in the Acorn System 1 Technical Manual. The three semi-circular legends on the bottom left of the board marked positions for optional push switches to trigger the board's RESET, IRQ (Interrupt ReQuest) and NMI (Non Maskable Interrupt) lines. Almost all CPU signals were accessible via the standard Eurocard connector on the right-hand side of the board. This connector was not fitted/supplied as standard with the kit version. The System 1 front board was used as the control panel for the fictional computer Slave in the 1981 series of the BBC science-fiction series Blake's 7. See also Acorn System 2, System 3, System 4, System 5 Acorn Atom References External links Comprehensive information on the System 1, including an emulator – Provided by Mike Cowlishaw Acorn System 1 manuals and schematics at ARCHIVE.ORG Early microcomputers System 1 6502-based home computers

Operating System (OS)

Windows NT 4.0 Windows NT 4.0 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. The direct successor to Windows NT 3.51, it was released to manufacturing on July 31, 1996, and was launched to retail on August 24, 1996. Windows NT 4.0 was and remains a primary business-oriented operating system, and three years after its introduction, it was followed by Windows 2000. Workstation, server and embedded editions were sold, and all editions feature a graphical user interface similar to that of Windows 95, which was superseded by Windows 98 and could still be directly upgraded by either Windows 2000 Professional or Windows Me. Microsoft ended mainstream support for Windows NT 4.0 Workstation on June 30, 2002, and ended extended support on June 30, 2004. Windows NT 4.0 Server mainstream support ended on December 31, 2002, then extended support on December 31, 2004. Windows NT 4.0 Embeddded mainstream support ended on June 30, 2003, followed by extended support on July 11, 2006. These editions were succeeded by Windows 2000 Professional, the Windows 2000 Server Family and Windows XP Embedded, respectively. Windows NT 4.0 is the last public release of Windows for the Alpha, MIPS, and PowerPC architectures. Overview The successor to Windows NT 3.51, Windows NT 4.0 introduced the user interface of Windows 95 to the Windows NT family, including the Windows shell, File Explorer (known as Windows NT Explorer at the time), and the use of "My" nomenclature for shell folders (e.g. My Computer). It also includes most components introduced with Windows 95. Internally, Windows NT 4.0 was known as the Shell Update Release (SUR). While many administrative tools, notably User Manager for Domains, Server Manager and Domain Name Service Manager still used the old graphical user interfaces, the Start menu in Windows NT 4.0 separated the per-user shortcuts and folders from the shared shortcuts and folders by a separator line. Windows NT 4.0 includes some enhancements from Microsoft Plus! for Windows 95 such as the Space Cadet pinball table, font smoothing, showing window contents while dragging, high-color icons and stretching the wallpaper to fit the screen. Windows Desktop Update could also be installed on Windows NT 4.0 to update the shell version and install Task Scheduler. Windows NT 4.0 Resource Kit included the Desktop Themes utility. Windows NT 4.0 is a preemptively multitasked, 32-bit operating system that is designed to work with either uniprocessor or symmetric multi-processor computers. Windows NT 4.0 is the last major release of Microsoft Windows to support the Alpha, MIPS or PowerPC CPU architectures as Windows 2000 runs solely on IA-32 only. It remained in use by businesses for a number of years, despite Microsoft's many efforts to get customers to upgrade to Windows 2000 and newer versions. It was also the last release in the Windows NT family to be branded as Windows NT although Windows 2000 carried the designation "Built on NT Technology". Features Although the chief enhancement has been the addition of the Windows 95 shell, there are several major performance, scalability and feature improvements to the core architecture, kernel, USER32, COM and MSRPC. Windows NT 4.0 also introduced the concept of system policies and the System Policy Editor. Other important features were: Crypto API Telephony API 2.0 with limited Unimodem support, which was the first release of TAPI on Windows NT DCOM and new OLE features Microsoft Transaction Server for network applications Microsoft Message Queuing (MSMQ), which improved interprocess communication Winsock 2 and the TCP/IP stack improvements File system defragmentation support The server editions of Windows NT 4.0 include Internet Information Services 2.0, Microsoft FrontPage 1.1, NetShow Services, Remote Access Service (which includes a PPTP server for VPN functionality) and Multi-Protocol Routing service. There are new administrative wizards and a lite version of the Network Monitor utility shipped with System Management Server. The Enterprise edition introduced Microsoft Cluster Server. One significant difference from previous versions of Windows NT is that the Graphics Device Interface (GDI) is moved into kernel mode rather than being in user mode in the CSRSS process. This eliminated a process-to-process context switch in calling GDI functions, resulting in a significant performance improvement over Windows NT 3.51, particularly in the graphical user interface. This, however, also mandated that graphics and printer drivers had to run in kernel mode as well, resulting in potential stability issues. Windows NT 4.0 was the first release of Microsoft Windows to include DirectX as standard—version 2 shipped with the initial release of Windows NT 4.0, and version 3 was included with the release of Service Pack 3 in mid-1997. However advanced hardware accelerated Direct3D and DirectSound multimedia features were never available on Windows NT 4.0. Later versions of DirectX were not released for Windows NT 4.0. However, OpenGL was supported; it was used by Quake 3 and Unreal Tournament. In early releases of 4.0, numerous stability issues did occur as graphics and printer vendors had to change their drivers to be compatible with the kernel mode interfaces exported by GDI. The change to move the GDI to run in the same process context as its caller was prompted by complaints from NT Workstation users about real-time graphics performance, but this change put a considerable onus on hardware manufacturers to update device drivers. Windows NT 4.0 also included a new Windows Task Manager utility. Previous versions of Windows NT included the Task List utility, but it only shows applications currently on the desktop. To monitor CPU and memory usage, users were forced to use Performance Monitor. The task manager offers a more convenient way of getting a snapshot of all the processes running on the system at any given time. Internet Explorer 2 was bundled with Windows NT 4. Windows NT 4.0 upgraded NTVDM's x86 emulation in the RISC versions from 286 to 486. Sysprep was introduced as a deployment tool with Windows NT 4.0. Comparison with Windows 95 Windows NT 4.0, like previous versions of Windows NT before it and versions after it, is a fully 32-bit OS, while Windows 95 is a 16/32-bit hybrid OS. While providing much greater stability than Windows 95, Windows NT 4.0 was less flexible from a desktop perspective. Much of the stability was gained through the use of protected memory and the hardware abstraction layer. Direct hardware access was disallowed and "misbehaving" programs were terminated without needing the computer to be restarted. The trade-off was that NT required much more memory (32 MB for normal desktop use, 128 MB or more for heavy 3D applications) in comparison to consumer targeted products such as Windows 95. While nearly all programs written for Windows 95 run on Windows NT, many 3D games would not, partly because of limited DirectX support for Windows NT 4.0. Third-party device drivers were an alternative to access the hardware directly, but poorly written drivers became a frequent source of the infamous error known as the Blue Screen of Death (BSoD) that would require the system to be restarted. In spite of shipping a year later than Windows 95, by default there is no Legacy Plug and Play support and no Device Manager on Windows NT 4.0, which greatly simplifies installation of hardware devices (although limited support could be installed later). Many basic DOS programs would run; however, graphical DOS programs would not run because of the way they accessed graphics hardware. Although Windows NT 4.0 introduced an application programming interface (API) for defragmentation, there was no built-in defragmentation utility, unlike Windows 95. Also, Windows NT 4.0 lacked USB support, a preliminary version of which would be added to OEM editions of Windows 95 in OSR 2.1. The difference between the NT family and 9x family would remain until the release of Windows XP in 2001. At that time, the APIs — such as OpenGL and DirectX — had matured sufficiently to be more efficient to write for common PC hardware, and the hardware itself had become powerful enough to handle the API processing overhead. The maximum amount of supported physical random-access memory (RAM) in Windows NT 4.0 is 4 GB, which is the maximum possible for a 32-bit operating system that does not support PAE. By comparison, Windows 95 fails to boot on computers with more than approximately 480 MB of memory. Like previous versions of NT, version 4.0 can run on multiple processor architectures. Windows 95, however, can only run on x86. Editions Windows NT 4.0 Server was included in versions 4.0 and 4.5 of BackOffice Small Business Server suite. Client Windows NT 4.0 Workstation was designed for use as the general business desktop operating system. Servers Windows NT 4.0 Server, released in 1996, was designed for small-scale business server systems. Windows NT 4.0 Server, Enterprise Edition, released in 1997, is the precursor to the Enterprise line of the Windows server family (Advanced Server in Windows 2000). Enterprise Server was designed for high-demand, high-traffic networks. Windows NT 4.0 Server, Enterprise Edition includes Service Pack 3. The Enterprise Edition saw the introduction of the boot flag, which changed the default virtual address space mapping from 2 GB kernel and 2 GB user space to 1 GB kernel and 3 GB userland. This version also sees the first introduction of cluster service. Windows NT 4.0 Terminal Server Edition, released in 1998, allows the users to log on remotely. The same functionality was called Terminal Services in Windows 2000 and later server releases, and also powers the Remote Desktop feature that first appeared in Windows XP and later on Windows Vista. Embedded Windows NT 4.0 Embedded (abbreviated NTe) is an edition of Windows NT 4.0 that was aimed at computer-powered major appliances, vending machines, ATMs and other devices that cannot be considered general-purpose computers per se. It is the same system as the standard Windows NT 4.0, but it comes packaged in a database of components and dependencies, from which a developer can choose individual components to build customized setup CDs and hard disk boot images. Windows NT 4.0 Embedded includes Service Pack 5. It was succeeded by Windows XP Embedded. Upgradeability An Option Pack was available as a free-bundled CD starting around 1998, which included IIS 4.0 with Active Server Pages, FrontPage Server Extensions, Certificate Server, MTS, MSMQ, CDONTS, Internet Authentication Service (IAS), Indexing Service, Microsoft Management Console 1.0, Microsoft Site Server, SMTP and NNTP services and other new software. Several features such as Distributed File System and Windows NT Load Balancing Service (WLBS) were delivered as addons for Windows NT Server 4.0. The Routing and Remote Access Service was also a downloadable feature which replaced Windows NT 4.0's separate RAS and Multi-Protocol Routing services. The last version of Microsoft Office to be compatible with Windows NT 4.0 is Office XP. Similarly, Windows Media Player 6.4 (which was released in April 1999) and DirectX 3.0a (which was released in December 1996) are the last versions of Windows Media Player and DirectX available for Windows NT 4.0, respectively. The last version of Internet Explorer supported on Windows NT 4.0 is Internet Explorer 6 with SP1, which was released in September 2002 (Service Pack 6a is required). Windows NT 4.0 could be directly upgraded to Windows 2000 or Windows XP Professional on IA-32-based systems only. Service packs Windows NT 4.0 received seven service packs during its lifecycle, as well as numerous service rollup packages and option packs. Only the first service pack was made available for the MIPS architecture, and Service Pack 2 was the final release for the PowerPC architecture. The last full service pack was Service Pack 6a (SP6a). Service Pack 7 was planned at one stage in early 2001, but this became the Post SP6a Security Rollup and not a full service pack, released on July 26, 2001, 16 months following the release of Windows 2000 and nearly three months prior to the release of Windows XP. In addition to bug fixes, the service packs also added a multitude of new features such as Ultra DMA mode for disk drives along with bus mastering, newer versions of Internet Information Services, user accounts and user profile improvements, smart card support, improved symmetric multiprocessing (SMP) scalability, clustering capabilities, COM support improvements, Event Log service, MS-CHAPv2 and NTLMv2, SMB packet signing, SYSKEY, boot improvements, WINS improvements, Routing and Remote Access Service (RRAS), PPTP, DCOM/HTTP tunneling improvements, IGMPv2, WMI, Active Accessibility and NTFS 3.0 support among others. Resource Kits Microsoft released five revisions of the Windows NT 4.0 Workstation and Server Resource Kit (original release plus four supplements) which contained a large number of tools and utilities, such as desktops.exe which allowed the user to have multiple desktops, as well as third-party software. Security Microsoft stopped providing security updates for Windows NT 4.0 Workstation on June 30, 2004, Windows NT 4.0 Server on December 31, 2004 and Windows NT 4.0 Embedded on July 11, 2006, due to major security flaws including Microsoft Security Bulletin MS03-010, which according to Microsoft could not be patched without significant changes to the core operating system. According to the security bulletin, "Due to the fundamental differences between Windows NT 4.0 and Windows 2000 and its successors, it is infeasible to rebuild the software for Windows NT 4.0 to eliminate the vulnerability. To do so would require re-architecting a very significant amount of the Windows NT 4.0 operating system, and there would be no assurance that applications designed to run on Windows NT 4.0 would continue to operate on the patched system." Between June 2003 and June 2007, 127 security flaws were identified and patched in Windows 2000 Server, many of which may also affect Windows NT 4.0 Server; however, Microsoft does not test security bulletins against unsupported software. References External links Guidebook: Windows NT 4.0 Gallery – A website dedicated to preserving and showcasing Graphical User Interfaces HPC:Factor Windows NT 4.0 Workstation Patches & Updates Guide HPC:Factor Windows NT 4.0 Server Patches & Updates Guide Josephn.net: Windows NT 4.0 Terminal Server Edition Tips & Updates MDGx: Windows NT 4.0 Essential Free Upgrades + Fixes 1996 software Products and services discontinued in 2006 4.0 IA-32 operating systems MIPS operating systems PowerPC operating systems

Operating System (OS)

Unix System Laboratories Unix System Laboratories (USL), sometimes written UNIX System Laboratories to follow relevant trademark guidelines of the time, was an American software laboratory and product development company that existed from 1989 through 1993. At first wholly, and then majority, owned by AT&T, it was responsible for the development and maintenance of one of the main branches of the Unix operating system, the UNIX System V Release 4 source code product. Through Univel, a partnership with Novell, it was also responsible for the development and production of the UnixWare packaged operating system for Intel architecture. In addition it developed Tuxedo, a transaction processing monitor, and was responsible for certain products related to the C++ programming language. USL was based in Summit, New Jersey, and its CEOs were Larry Dooling followed by Roel Pieper. Created from earlier AT&T entities, USL was, as industry writer Christopher Negus has observed, the culmination of AT&T's long involvement in Unix, "a jewel that couldn't quite find a home or a way to make a profit." USL was sold to Novell in 1993. Origins as subsidiary of AT&T AT&T announced the creation of the UNIX Software Operation (USO) – a separate and distinct AT&T business unit responsible for the development, marketing, and licensing of UNIX System V software – in January 1989. This was done, as a subsequent press release stated, "in order to separate AT&T's UNIX System source code business from its computer systems business," the latter a reference to AT&T Computer Systems. USO included the AT&T Data Systems Group organizations responsible for UNIX product planning and management, licensing, and marketing. Peter J. Weinberger was named chief scientist of USO while also retaining his job in the computing science research center at Bell Labs; no other Bell Labs assets were transferred to USO. The head of USO was Larry Dooling, who had been a vice-president in sales and marketing in the AT&T Data Systems Group. Unlike the original Unix work, which had been done in the Bell Labs facility in Murray Hill, USO and the commercialization work was done a few miles away in Summit, New Jersey, in a building located off a cloverleaf-like interchange among New Jersey Route 24, New Jersey Route 124, and John F. Kennedy Parkway and across from The Mall at Short Hills and near the Passaic River. This AT&T Bell Labs location was known as SF for Summit Facility. UNIX System Laboratories, Inc., came into being as a separate subsidiary of AT&T in November 1989 and was assigned all U.S.-based AT&T Unix and USO assets. However USO continued to operate as USO until June 1990, when the reincorporation of AT&T's European and Asian Unix business operations as wholly owned subsidiaries of USL was completed. At that point the UNIX Software Operation was publicly rebranded as UNIX System Laboratories. Again, a point of emphasis was to separate the Unix-based business from AT&T's hardware-based business. The subsidiaries were known as UNIX System Laboratories Europe, Ltd., sited near Ealing Broadway in London, and UNIX System Laboratories Pacific, Ltd., located in Shiba, Tokyo. Dooling was named the initial president of USL, continuing from his position at USO. These organizational changes were taking place in the context of the open systems movement and the ongoing Unix wars. In consequence, the pro-AT&T side Unix International (as opposed to the anti-AT&T side Open Software Foundation) declared that "In the last 18 months AT&T has made good on its commitment to treat UNIX System as the industry asset it is and to open the UNIX System V development process to the entire industry." Unix System V work One unit within USL, called the UNIX System V Software business unit and headed by Michael J. DeFazio, was responsible for the development of the UNIX System V base technology. DeFazio had held a similar role within USO. The USO/USL staff was heavily involved in the creation of UNIX System V Release 4, which shipped in 1989 and was a joint project with Sun Microsystems. This work incorporated technology from a variety of Unix-based efforts, including UNIX System V, BSD, and Xenix. There were additions and new innovations as well from both the AT&T and Sun sides. System V Release 4 debuted at the Unix Expo trade show in New York in November 1989, in the form of source code availability for it as well as demonstrations from Unix International of SVR4-based applications running on seventeen different vendor platforms. End-user versions of Release 4 became available during 1990. Next USL engaged in an especially arduous effort into trying to satisfy the requirements of the National Computer Security Center's Trusted Computer System Evaluation Criteria ("Orange Book") to the B2 level. This manifested itself in System V Release 4.1 ES (Enhanced Security), which also included generally useful features such as support for dynamic loading of kernel modules. Following that, USL worked on System V Release 4.2, which was released in June 1992. InfoWorld characterized this effort as "at the core of an assault on the enterprise networking market," with a modular architecture that stressed improved support for enterprise- and network-level administration, drivers for both Token Ring and Ethernet, and a greater ability to run on low-end machine configurations. Multiprocessing became the focus of the final USL-based OEM release of System V, which was Release 4.2MP, released in December 1993. USL continued the publication of an early Unix standard, the System V Interface Definition (SVID). Moreover, the SVID became one of the bases for the more important, vendor-independent POSIX standard for Unix, which System V Release 4 releases also conformed to, as well as the later Single UNIX Specification. USL produced many books documenting various aspects of Unix System V. USL also provided some training and consulting services for Unix systems. Chorus and Ouverture In 1991, USL forged an arrangement with the French company Chorus Systèmes SA to engage in cooperative work on the Chorus microkernel technology, with the idea of supporting SVR4 on a microkernel and thereby making it more scalable and better suited for parallel and distributed applications. As part of this, USL took a $1 million stake in Chorus Systèmes. Much of the USL Chorus work was done at the USL Europe facility in London. By 1993 the work was still ongoing, with questions of industry standardization of interfaces arising. Unisys was also part of the collaboration effort. Announcements made during 1993 promised an OEM release in 1994 and a general availability release in 1995. This was part of the larger Ouverture project, a $14 million effort that was itself part of the European Strategic Program on Research in Information Technology (ESPRIT), overseen by the European Commission. Other software work Another unit within USL, called the Open Solutions Software business unit and headed by Joel A. Appelbaum, was responsible for other system software that in some way worked in conjunction with Unix. The Tuxedo transaction processing middleware had also been transferred from elsewhere in AT&T to USL. It had originated as the Loop Maintenance Operations System (LMOS) followed by the Unix Transaction System (UNITS) and was used for projects internally within AT&T. It was then renamed by USL and, as Release 4.0 of what was now called Tuxedo, in 1989 was offered for the first time as a commercial product. USL also developed and marketed the OSI Communications Platform, which was an implementation of the OSI protocols for Unix-based networking. C++ language work There was also a languages department at Unix System Laboratories, which was responsible for the C language compiler and development tools used to build Unix. Moreover, it was responsible for commercial sales related to the C++ language, including development tools such as the Cfront compiler that had come from AT&T. Indeed, the paper describing one of the first implementations of automatic instantiation of C++ templates in a C++ compiler had as lead author an engineer associated with Unix System Laboratories. And Margaret A. Ellis, co-author with C++ creator Bjarne Stroustrup of The Annotated C++ Reference Manual, an important publication in the history of the language, was a USL software engineer. USL also continued the development of, and attempted to market, C++ Standard Components, an early instance of a C++ software foundation library that supported container classes and various other computer science-based functionality such as finite-state machines, graphs, and regular expressions. The Standard Components originated in conjunction with early developments in the C++ language in Bell Labs and became widely used internally within AT&T, by one estimate being used in hundreds of projects. They represented an effort among early library writers there to design reusable code using C++ idioms. Unlike its other offerings, which were sold to OEM vendors and resellers, here USL sold to end users. The initial release of USL C++ Standard Components to the general computing industry was labelled as Release 2.0 and occurred in 1991; it suffered from an awkward mechanism to get around the lack of templates in the container classes. That was followed by Release 3.0, which added support for templates, in 1992. Some within USL believed that C++ Standard Components could become a language standard as well as a significant source of revenue, but it had trouble gaining traction outside of AT&T. Stroustrup would later describe these goals as "a misguided belief". In any case, all such libraries were soon eclipsed by the radically different Standard Template Library (STL), which became the standardized foundation library for the C++ language. As it happens, one of the Standard Components, array_alg, was designed by the creator of STL, Alex Stepanov, and can be considered an early predecessor of STL. Partial spinoff from AT&T In April 1991, USL became partly independent of AT&T when about 22 percent of it, worth about $65 million, was sold to eleven outside computer vendors: Amdahl, Motorola, Novell, Sun, ICL, Olivetti, Fujitsu, NEC, OKI Electric, Toshiba, and the Institute for Information Industry. There was a stated goal to lessen the control AT&T had over Unix, which would lead to USL becoming a publicly owned company within three years. An AT&T executive said, "AT&T is convinced that the best way to nurture the growth of the open systems movement and to share into it ourselves is to establish an independent Unix Systems Laboratory with the technical guidance of Unix International and the business advice of investors who will ensure that USL is run properly and profitably." By this point USL had some 500 employees, 2400 customers, and annual revenue around the $100 million mark. AT&T said that USL had been profitable since its inception in 1989. USL got a new president and CEO in November 1991 when Dooling was replaced by the Dutchman Roel Pieper, formerly chief technical officer of Software AG. USL was aggressive in defending its perceived intellectual property rights, initiating as the plaintiff a lawsuit in 1992 against Berkeley Software Design makers of and the Regents of the University of California over copyrights and trademarks related to Unix. The case was known as UNIX System Laboratories, Inc. v. Berkeley Software Design, Inc. and in it USL asked the court for a preliminary injunction that would bar the Berkeley firm and the university from distributing their Net/2 operating system release, which was implied to be Unix, until the case was concluded. In response the university filed a countersuit against AT&T for alleged breaches in the licensing agreement the two parties had. (The case was settled out of court in January 1994.) Univel and UnixWare In December 1991, USL combined with Novell to form the Univel joint venture. The goal was to make the "Destiny" desktop for Intel commodity hardware, which would be USL's first shrink-wrapped binary product, with the necessary resources for sales, marketing, and distribution being moved into the new entity. Kanwal Rekhi, a Novell vice president who helped launch Univel, said the goal was to create a "Unix for the masses". A May 1992 InfoWorld interview with Pieper captured some of the ambitions of USL at the time, as Pieper said: "It is not just a new Unix version; rather it is the creation of an entire model change for Unix that says there are better ways to bring the benefits and features of Unix into a distributed PC environment. The earlier model did not allow Unix to play in the low-end market because of its size, complexity, and cost. The new model calls for business partnerships, such as the one with Novell, to deliver Unix to the commercial marketplace." In another interview around the same time, Pieper predicted that if the new Unix became a success, USL revenue could increase ten-fold to $1 billion within five years. Pieper acknowledged that similar Unix efforts had failed in the past, but said that the presence of Novell's PC presence and marketing experience as well as the interest of Intel would make the difference this time. Indeed, Pieper had aspirations to be another Bill Gates: "I want to be in the same position." UnixWare 1.0, which is what Destiny became a product as, was announced on October 12, 1992. It was based on the Unix System V release 4.2 kernel. The MoOLIT toolkit was used for the windowing system, allowing the user to choose between an OPEN LOOK or MOTIF-like look and feel at run time. In order to make the system more robust on commodity desktop hardware the Veritas VXFS journaling file system was used in place of the UFS file system used in SVR4. Networking support in UnixWare included both TCP/IP and interoperability with Novell's NetWare protocols of IPX/SPX. The former were the standard among Unix users at the time of development, while PC networking was much more commonly based on the highly successful NetWare product; indeed, the base level of the Personal Edition of UnixWare did not even have TCP/IP included, while the Application Server version did. Initial sales of UnixWare were underwhelming, with Unix facing a difficult time in the PC market. This was in part because Windows already had a stronghold there, in part because USL's third-party licensing payment obligations made low-cost sales uneconomical, and in part because of a lack of applications to run on UnixWare. Acquisition by Novell On December 21, 1992, it was announced that Novell would acquire Unix System Laboratories, and all of its Unix assets, including all copyrights, trademarks, and licensing contracts, for some $335 million in stock. The news led to large headlines of the "NOVELL BUYS UNIX" variety. The measure was intended to help Novell compete against Microsoft, which was on the verge of including networking as a built-in feature of Windows in conjunction with the Windows NT server. It was also an outgrowth of Novell chief Ray Noorda's theories about coopetition in a technology industry. The move seemed like a long shot to analysts, with a commentary piece in Computerworld outlining the obstacles to success and stating, "Saying this deal has the technical potential to counter Windows NT is very different from predicting that it will do so." There was negative reaction to the acquisition from USL shareholders, USL employees, and members of Unix International. Noorda had to emphasize that Novell had no plans to move USL operations from New Jersey to Utah, where Novell was based. And Noorda and Pieper had to travel to Japan to reassure USL shareholders and investors there. Nonetheless, the deal was finalized in June 1993. Novell created the Unix Systems Group to contain the new business, which also absorbed the Univel venture. Rekhi was named as the head of the Unix Systems Group. Pieper, who had been assigned under Rekhi with little role to play, soon departed, leaving Novell in August 1993. The USL Europe office in London was moved into Novell's facility in Bracknell, Berkshire. The Chorus work it was doing became the basis for the Novell "SuperNOS", a project to create a microkernel-based, UnixWare–NetWare hybrid, network operating system. Legacy The acquisition of USL never really worked out for Novell, and was followed by Novell's misguided acquisitions of WordPerfect and Quattro Pro in another attempt to compete head-to-head with Microsoft. In particular, the "SuperNOS" project never achieved fruition. Novell announced the sale of Unix to the Santa Cruz Operation, coincident with a licensing arrangement with Hewlett Packard, in September 1995. Following another change of ownership, the renamed The SCO Group and the Unix System V source base became elements of the SCO–Linux disputes. After The SCO Group went bankrupt, the SCO products using the Unix System V source base were purchased by UnXis, later renamed to Xinuos. Although it never took off within the industry, C++ Standard Components remained in the development kits for Novell UnixWare, later SCO UnixWare, into the 2000s. Tuxedo was acquired by BEA Systems in the 1990s, and then upon that firm being acquired became part of Oracle Fusion Middleware. In the view of writer Christopher Negus, "The UNIX Laboratory was considered a jewel that couldn't quite find a home or a way to make a profit. As it moved between Bell Laboratories and other areas of AT&T, its name changed several times. It is probably best remembered by the name it had as it began its spin-off from AT&T: UNIX System Laboratories (USL)." However Negus believes that in three crucial respects USL's actions – in continuing to release a source code product to its partners, in working to define industry standards such as POSIX, and in making decisions on the direction of Unix based on technical merit not corporate advantage – paved the way for the rise of a Unix-like entity such as the Linux operating system, and that this beneficial historical role has been obscured by the SCO–Linux controversies. See also History of Unix References External links History and Timeline from The Open Group 1989 establishments in New Jersey 1993 disestablishments in New Jersey 1993 mergers and acquisitions AT&T subsidiaries Bell Labs Defunct companies based in New Jersey Defunct software companies of the United States Novell Software companies established in 1989 Software companies disestablished in 1993 Summit, New Jersey Unix history

Operating System (OS)

Linux on embedded systems Operating systems based on the Linux kernel are used in embedded systems such as consumer electronics (i.e. set-top boxes, smart TVs, personal video recorders (PVRs), in-vehicle infotainment (IVI), networking equipment (such as routers, switches, wireless access points (WAPs) or wireless routers), machine control, industrial automation, navigation equipment, spacecraft flight software, and medical instruments in general). Because of their versatility, operating systems based on the Linux kernel can be also found in mobile devices that are actually touchscreen-based embedded devices, such as smartphones and tablets, together with personal digital assistants (PDAs) and portable media players that also include a touchscreen. This is a challenge for most learners because their computer experience is mainly based on GUI (Graphical user interface) based interaction with the machine and high-level programming on the one hand and low-level programming of small microcontrollers on the other hand while the concept of command line interfaces is widely unknown. History The Linux kernel has been ported to a variety of CPUs which are not only primarily used as the processor of a desktop or server computer, but also ARC, ARM, AVR32, ETRAX CRIS, FR-V, H8300, IP7000, m68k, MIPS, mn10300, PowerPC, SuperH, and Xtensa processors. Linux is also used as an alternative to using a proprietary operating system and its associated toolchain. Variants The Embeddable Linux Kernel Subset is a Linux distribution that fits on a floppy disk for outdated or low resource hardware. Devices coverage Due to its low cost (freely available source code) and ease of customization, Linux has been shipped in many consumer devices. Devices covering PDAs (like the Sharp Zaurus family), TomTom GPS navigation devices, residential gateways like the Linksys WRT54G series or smartphones such as the Motorola exz series, Openmoko handsets, devices running Sailfish OS developed by Jolla like Jolla C and Intex Aqua Fish and the Nokia N900 and Nokia N9. Android, a Linux-kernel-based operating system acquired and extended by Google and introduced in 2008, has become a highly competitive platform for smartphones and tablets. In July 2012, Android's smartphone market share in the United States was at 52%, reaching 82% worldwide in Q2 2015. Communities With the availability of consumer embedded devices, communities of users and developers were formed around these devices: replacement or enhancements of the Linux distribution shipped on the device has often been made possible thanks to availability of the source code and to the communities surrounding the devices. Due to the high number of devices, standardized build systems have appeared, including Yocto, OpenEmbedded, Buildroot, OpenWrt, and LTIB. Platform usage The advantages of embedded Linux over proprietary embedded operating systems include multiple suppliers for software, development and support; no royalties or licensing fees; a stable kernel; the ability to read, modify and redistribute the source code. The technical disadvantages include a comparatively large memory footprint (kernel and root filesystem); complexities of user mode and kernel mode memory access, and a complex device drivers framework. Limitations Not every embedded Linux distribution is required to or meets real-time requirements. This is particular relevant for safety critical applications and systems. Projects to develop real-time and safety-critical support are Real-Time Linux (PREEMPT_RT) and ELISA (under Linux Foundation). Real Time Linux project aims mainlining the PREEMPT_RT-version. See also Articles: Convergent Linux Platform Linux range of use Linux for mobile devices Products/Distributions: BusyBox Debian – used on Raspberry Pi Embeddable Linux Kernel Subset Emdebian Grip Familiar Linux Google's Android well-known type of embedded Linux, e.g. on smartphones Mobilinux OpenMoko OpenWrt RTLinux Tizen – embedded Linux for smartphones Ubuntu - Core and Server, on RPi, x86, ARM Vendors: Access Co. Canonical with Ubuntu Core and Ubuntu Server LynuxWorks Mentor Graphics MontaVista Software Wind River Systems TimeSys ENEA AB SUSE References Further reading See also Preemption (computing) Safety-critical system External links Embedded Linux course on youtube (Zedboard) Embedded Linux mailist list archive Embedded Debian Project (obsolete) VxWorks to Embedded Linux: a Success Story Embedded Linux Wiki: A centralized place for sharing Embedded Linux Knowledge Embedded operating systems

Operating System (OS)

One-instruction set computer A one-instruction set computer (OISC), sometimes called an ultimate reduced instruction set computer (URISC), is an abstract machine that uses only one instructionobviating the need for a machine language opcode. With a judicious choice for the single instruction and given infinite resources, an OISC is capable of being a universal computer in the same manner as traditional computers that have multiple instructions. OISCs have been recommended as aids in teaching computer architecture and have been used as computational models in structural computing research. The first carbon nanotube computer is a 1-bit one-instruction set computer (and has only 178 transistors). Machine architecture In a Turing-complete model, each memory location can store an arbitrary integer, anddepending on the modelthere may be arbitrarily many locations. The instructions themselves reside in memory as a sequence of such integers. There exists a class of universal computers with a single instruction based on bit manipulation such as bit copying or bit inversion. Since their memory model is finite, as is the memory structure used in real computers, those bit manipulation machines are equivalent to real computers rather than to Turing machines. Currently known OISCs can be roughly separated into three broad categories: Bit-manipulating machines Transport triggered architecture machines Arithmetic-based Turing-complete machines Bit-manipulating machines Bit-manipulating machines are the simplest class. FlipJump The FlipJump machine has 1 instruction, a;b - flips the bit a, then jumps to b. This is the most primitive OISC, but it's still useful. It can successfully do Math/Logic calculations, branching, pointers, and calling functions with the help of its standard library. BitBitJump A bit copying machine, called BitBitJump, copies one bit in memory and passes the execution unconditionally to the address specified by one of the operands of the instruction. This process turns out to be capable of universal computation (i.e. being able to execute any algorithm and to interpret any other universal machine) because copying bits can conditionally modify the code that will be subsequently executed. Toga computer Another machine, called the Toga Computer, inverts a bit and passes the execution conditionally depending on the result of inversion. The unique instruction is TOGA(a,b) which stands for TOGgle a And branch to b if the result of the toggle operation is true. Multi-bit copying machine Similar to BitBitJump, a multi-bit copying machine copies several bits at the same time. The problem of computational universality is solved in this case by keeping predefined jump tables in the memory. Transport triggered architecture Transport triggered architecture (TTA) is a design in which computation is a side effect of data transport. Usually, some memory registers (triggering ports) within common address space perform an assigned operation when the instruction references them. For example, in an OISC using a single memory-to-memory copy instruction, this is done by triggering ports that perform arithmetic and instruction pointer jumps when written to. Arithmetic-based Turing-complete machines Arithmetic-based Turing-complete machines use an arithmetic operation and a conditional jump. Like the two previous universal computers, this class is also Turing-complete. The instruction operates on integers which may also be addresses in memory. Currently there are several known OISCs of this class, based on different arithmetic operations: addition (addleq, add and branch if less than or equal to zero) decrement (DJN, Decrement and branch (Jump) if Nonzero) increment (P1eq, Plus 1 and branch if equal to another value) subtraction (subleq, subtract and branch if less than or equal to zero) positive subtraction when possible, else branch (Arithmetic machine) Instruction types Common choices for the single instruction are: Subtract and branch if less than or equal to zero Subtract and branch if negative Subtract if positive else branch Reverse subtract and skip if borrow Move (used as part of a transport triggered architecture) Subtract and branch if non zero (SBNZ a, b, c, destination) Cryptoleq (heterogeneous encrypted and unencrypted computation) Only one of these instructions is used in a given implementation. Hence, there is no need for an opcode to identify which instruction to execute; the choice of instruction is inherent in the design of the machine, and an OISC is typically named after the instruction it uses (e.g., an SBN OISC, the SUBLEQ language, etc.). Each of the above instructions can be used to construct a Turing-complete OISC. This article presents only subtraction-based instructions among those that are not transport triggered. However, it is possible to construct Turing complete machines using an instruction based on other arithmetic operations, e.g., addition. For example, one variation known as DLN (Decrement and jump if not zero) has only two operands and uses decrement as the base operation. For more information see Subleq derivative languages . Subtract and branch if not equal to zero The SBNZ a, b, c, d instruction ("subtract and branch if not equal to zero") subtracts the contents at address a from the contents at address b, stores the result at address c, and then, if the result is not 0, transfers control to address d (if the result is equal to zero, execution proceeds to the next instruction in sequence). Subtract and branch if less than or equal to zero The instruction ("subtract and branch if less than or equal to zero") subtracts the contents at address from the contents at address , stores the result at address , and then, if the result is not positive, transfers control to address (if the result is positive, execution proceeds to the next instruction in sequence). Pseudocode: Instruction subleq a, b, c Mem[b] = Mem[b] - Mem[a] if (Mem[b] ≤ 0) goto c Conditional branching can be suppressed by setting the third operand equal to the address of the next instruction in sequence. If the third operand is not written, this suppression is implied. A variant is also possible with two operands and an internal accumulator, where the accumulator is subtracted from the memory location specified by the first operand. The result is stored in both the accumulator and the memory location, and the second operand specifies the branch address: Instruction subleq2 a, b Mem[a] = Mem[a] - ACCUM ACCUM = Mem[a] if (Mem[a] ≤ 0) goto b Although this uses only two (instead of three) operands per instruction, correspondingly more instructions are then needed to effect various logical operations. Synthesized instructions It is possible to synthesize many types of higher-order instructions using only the instruction. Unconditional branch: subleq Z, Z, c Addition can be performed by repeated subtraction, with no conditional branching; e.g., the following instructions result in the content at location being added to the content at location : subleq a, Z subleq Z, b subleq Z, Z The first instruction subtracts the content at location from the content at location (which is 0) and stores the result (which is the negative of the content at ) in location . The second instruction subtracts this result from , storing in this difference (which is now the sum of the contents originally at and ); the third instruction restores the value 0 to . A copy instruction can be implemented similarly; e.g., the following instructions result in the content at location getting replaced by the content at location , again assuming the content at location is maintained as 0: subleq b, b subleq a, Z subleq Z, b subleq Z, Z Any desired arithmetic test can be built. For example, a branch-if-zero condition can be assembled from the following instructions: subleq b, Z, L1 subleq Z, Z, OUT L1: subleq Z, Z subleq Z, b, c OUT: ... Subleq2 can also be used to synthesize higher-order instructions, although it generally requires more operations for a given task. For example, no fewer than 10 subleq2 instructions are required to flip all the bits in a given byte: subleq2 tmp ; tmp = 0 (tmp = temporary register) subleq2 tmp subleq2 one ; acc = -1 subleq2 a ; a' = a + 1 subleq2 Z ; Z = - a - 1 subleq2 tmp ; tmp = a + 1 subleq2 a ; a' = 0 subleq2 tmp ; load tmp into acc subleq2 a ; a' = - a - 1 ( = ~a ) subleq2 Z ; set Z back to 0 Emulation The following program (written in pseudocode) emulates the execution of a -based OISC: int memory[], program_counter, a, b, c program_counter = 0 while (program_counter >= 0): a = memory[program_counter] b = memory[program_counter+1] c = memory[program_counter+2] if (a < 0 or b < 0): program_counter = -1 else: memory[b] = memory[b] - memory[a] if (memory[b] > 0): program_counter += 3 else: program_counter = c This program assumes that is indexed by nonnegative integers. Consequently, for a instruction (, , ), the program interprets , , or an executed branch to as a halting condition. Similar interpreters written in a -based language (i.e., self-interpreters, which may use self-modifying code as allowed by the nature of the instruction) can be found in the external links below. Compilation There is a compiler called Higher Subleq written by Oleg Mazonka that compiles a simplified C program into code. Subtract and branch if negative The instruction ("subtract and branch if negative"), also called , is defined similarly to : Instruction subneg a, b, c Mem[b] = Mem[b] - Mem[a] if (Mem[b] < 0) goto c Conditional branching can be suppressed by setting the third operand equal to the address of the next instruction in sequence. If the third operand is not written, this suppression is implied. Synthesized instructions It is possible to synthesize many types of higher-order instructions using only the instruction. For simplicity, only one synthesized instruction is shown here to illustrate the difference between and . Unconditional branch: subneg POS, Z, c where and are locations previously set to contain 0 and a positive integer, respectively; Unconditional branching is assured only if initially contains 0 (or a value less than the integer stored in ). A follow-up instruction is required to clear after the branching, assuming that the content of must be maintained as 0. subneg4 A variant is also possible with four operands – subneg4. The reversal of minuend and subtrahend eases implementation in hardware. The non-destructive result simplifies the synthetic instructions. Instruction subneg s, m, r, j (* subtrahend, minuend, result and jump addresses *) Mem[r] = Mem[m] - Mem[s] if (Mem[r] < 0) goto j Arithmetic machine In an attempt to make Turing machine more intuitive, Z. A. Melzac consider the task of computing with positive numbers. The machine has an infinite abacus, an infinite number of counters (pebbles, tally sticks) initially at a special location S. The machine is able to do one operation: Take from location X as many counters as there are in location Y and transfer them to location Z and proceed to next instruction. If this operation is not possible because there is not enough counters in Y, then leave the abacus as it is and proceed to instruction T. This essentially a subneg where the test is done before rather than after the subtraction, in order to keep all numbers positive and mimic a human operator computing on a real world abacus. Pseudocode: Instruction melzac X, Y, Z, T if (Mem[Y] < Mem[X]) goto T Mem[Z] = Mem[Y] - Mem[X] After giving a few programs: multiplication, gcd, computing the n-th prime number, representation in base b of an arbitrary number, sorting in order of magnitude, Melzac shows explicitly how to simulate an arbitrary Turing machine on his arithmetic machine. He mentions that it can easily be shown using the elements of recursive functions that every number calculable on the arithmetic machine is computable. A proof of which was given by Lambek on an equivalent two instruction machine : X+ (increment X) and X− else T (decrement X if it not empty, else jump to T). Reverse subtract and skip if borrow In a reverse subtract and skip if borrow (RSSB) instruction, the accumulator is subtracted from the memory location and the next instruction is skipped if there was a borrow (memory location was smaller than the accumulator). The result is stored in both the accumulator and the memory location. The program counter is mapped to memory location 0. The accumulator is mapped to memory location 1. Instruction rssb x ACCUM = Mem[x] - ACCUM Mem[x] = ACCUM if (ACCUM < 0) goto PC + 2 Example To set x to the value of y minus z: # First, move z to the destination location x. RSSB temp # Three instructions required to clear acc, temp [See Note 1] RSSB temp RSSB temp RSSB x # Two instructions clear acc, x, since acc is already clear RSSB x RSSB y # Load y into acc: no borrow RSSB temp # Store -y into acc, temp: always borrow and skip RSSB temp # Skipped RSSB x # Store y into x, acc # Second, perform the operation. RSSB temp # Three instructions required to clear acc, temp RSSB temp RSSB temp RSSB z # Load z RSSB x # x = y - z [See Note 2] [Note 1] If the value stored at "temp" is initially a negative value and the instruction that executed right before the first "RSSB temp" in this routine borrowed, then four "RSSB temp" instructions will be required for the routine to work. [Note 2] If the value stored at "z" is initially a negative value then the final "RSSB x" will be skipped and thus the routine will not work. Transport triggered architecture A transport triggered architecture uses only the move instruction, hence it was originally called a "move machine". This instruction moves the contents of one memory location to another memory location combining with the current content of the new location: Instruction movx a, b (also written a -> b) OP = GetOperation(Mem[b]) Mem[b] := OP(Mem[a], Mem[b]) The operation performed is defined by the destination memory cell. Some cells are specialized in addition, some other in multiplication, etc. So memory cells are not simple store but coupled with an arithmetic logic unit (ALU) setup to perform only one sort of operation with the current value of the cell. Some of the cells are control flow instructions to alter the program execution with jumps, conditional execution, subroutines, if-then-else, for-loop, etc... A commercial transport triggered architecture microcontroller has been produced called MAXQ, which hides the apparent inconvenience of an OISC by using a "transfer map" that represents all possible destinations for the move instructions. Cryptoleq Cryptoleq is a language consisting of one eponymous instruction, is capable of performing general-purpose computation on encrypted programs and is a close relative to Subleq. Cryptoleq works on continuous cells of memory using direct and indirect addressing, and performs two operations and on three values A, B, and C: Instruction cryptoleq a, b, c Mem[b] = O1(Mem[a], Mem[b]) if O2(Mem[b]) ≤ 0 IP = c else IP = IP + 3 where a, b and c are addressed by the instruction pointer, IP, with the value of IP addressing a, IP + 1 point to b and IP + 2 to c. In Cryptoleq operations and are defined as follows: The main difference with Subleq is that in Subleq, simply subtracts from and equals to . Cryptoleq is also homomorphic to Subleq, modular inversion and multiplication is homomorphic to subtraction and the operation of corresponds the Subleq test if the values were unencrypted. A program written in Subleq can run on a Cryptoleq machine, meaning backwards compatibility. Cryptoleq though, implements fully homomorphic calculations and since the model is be able to do multiplications. Multiplication on an encrypted domain is assisted by a unique function G that is assumed to be difficult to reverse engineer and allows re-encryption of a value based on the operation: where is the re-encrypted value of and is encrypted zero. is the encrypted value of a variable, let it be , and equals . The multiplication algorithm is based on addition and subtraction, uses the function G and does not have conditional jumps nor branches. Cryptoleq encryption is based on Paillier cryptosystem. See also FRACTRAN Register machine Turing tarpit Zero instruction set computer References External links Subleq on the esoteric programming languages wiki – interpreters, compilers, examples and derivative languages by Christopher Domas Laboratory subleq computer – FPGA implementation using VHDL The Retrocomputing Museum – SBN emulator and sample programs Laboratory SBN computer – implemented with 7400 series integrated circuits RSSB on the esoteric programming languages wiki – interpreters and examples Dr. Dobb's 32-bit OISC implementation – transport triggered architecture (TTA) on an FPGA using Verilog Introduction to the MAXQ Architecture – includes transfer map diagram OISC-Emulator – graphical version TrapCC (recent Intel x86 MMUs are actually Turing-complete OISCs.) SBN simulator – simulator and design inspired by CARDboard Illustrative Aid to Computation One-bit Computing at 60 Hertz – intermediate between a computer and a state machine The NOR Machineinfo on building a CPU with only one Instruction CryptoleqCryptoleq resources repository CAAMPComputer Architecture A Minimalist Perspective DawnOS – an operating system for the SUBLEQ architecture Unileq – a variant of SUBLEQ using unsigned integers Models of computation Esoteric programming languages

Operating System (OS)

ARX (operating system) ARX was an unreleased Mach-like operating system written in Modula-2+ developed by Acorn Computers Ltd in the Acorn Research Centre (ARC) United Kingdom (UK) and later by Olivetti - which purchased Acorn - for Acorn's new Archimedes personal computers based on the ARM architecture reduced instruction set computer (RISC) central processing unit (CPUs). Overview According to the project Application Manager Richard Cownie, during the project, while Acorn was developing the kernel, it used the C and Acorn Modula Execution Library (CAMEL) in the Acorn Extended Modula-2 (AEM2) compiler (ported from Modula-2 ETH Zurich (ETH) using Econet hardware). Though never released externally, CAMEL was ported to use on Sun Microsystems Unix computers. In an effort to port Sun's workstations Sun NeWS to the Archimedes, David Chase developed a compiler based on AEM2 for the programming language Modula-3. ARX was a preemptive multitasking, multithreading, multi-user operating system. Much of the OS ran in user mode and as a result suffered performance problems due to switches into kernel mode to perform mutexes, which led to the introduction of the SWP instruction to the instruction set of the ARM3 version of the ARM processor. It had support of a file system for optical (write once read many (WORM)) disks and featured a window system, a window toolkit (and a direct manipulation user interface (UI) editor) and an Interscript-based text editor, for enriched documents written in Interpress (a HTML precursor). The OS had to be fitted in a 512 KB read-only memory (ROM) ROM image. This suggests that ARX had a microkernel-type design. It was not finished in time to be used in the Acorn Archimedes range of computers, which shipped in 1987 with an operating system named Arthur, later renamed RISC OS, derived from the earlier Machine Operating System (MOS) from Acorn's earlier 8-bit BBC Micro range. Confusion persisted about the nature of ARX amongst the wider public and press, with some believing that ARX was Acorn's own Unix variant, with this view being refined in time to accommodate ARX as Acorn's own attempt to deliver a "UNIX look-alike" whose development had been abandoned in favour of a traditional Unix version for the Archimedes, which ultimately emerged as RISC iX. The Acorn Research Centre was acquired by Olivetti. See also RISC iX References External links ARX features History of the addition of the SWP instruction to the ARM3 instruction set Acorn operating systems ARM operating systems Discontinued operating systems Microkernel-based operating systems Microkernels

Operating System (OS)

Windows Live Windows Live is a discontinued brand name for a set of web services and software products developed by Microsoft as part of its software-as-a-service platform. Chief components under the brand name included web services (all of which were exposed through corresponding web applications), several computer programs that interact with the services, and specialized web services for mobile devices. According to Microsoft, Windows Live "is a way to extend the Windows user experience". As such, Windows Vista's welcome screen provides a link to download Windows Live Messenger or to subscribe to Windows Live OneCare. Also, Windows Mail, Windows Photo Gallery and Windows Movie Maker were not offered with Windows 7 and became an exclusive part of Windows Live. Microsoft announced that Windows 8 would see Windows Live apps included right out-of-the-box, and would include built-in synchronization technologies powered by OneDrive (then SkyDrive). The Windows Live brand was phased out during August 2012, when Microsoft released Windows 8 to manufacturing. Active Windows Live services remained active but were gradually renamed. The "live.com" domain, however, continues to be used in the URLs for Outlook and OneDrive. History Windows Live was first announced on November 1, 2005. In its initial release, several Windows Live properties were rebranded and enhanced from Microsoft's MSN set of products and services. However, MSN still exists alongside Windows Live as a means of delivering content (as opposed to customized content and communications). In May 2012 Microsoft began renaming Windows Live services, partly in anticipation of Windows 8, which integrates many of the Windows Live products and services into the operating system. Services Online services The following services were once part of Windows Live but are still online. Outlook.com and OneDrive still use the "Live" branding in the URL even though the brand name is dropped. Mobile services Windows Phone My Windows Phone is a free online companion service for Windows Phone mobile devices that provides users with a free mobile phone back-up solution by wirelessly synchronizing contacts, calendar appointments, photos, and OneNote notebooks with a password-protected online portal. Users can access and manage their information stored on their Windows Phone devices via the online portal using their Microsoft account, as well as accessing a set of features for remotely ringing, locking, mapping, and erasing their lost phones. This service integrates tightly with other Windows Live services including Outlook.com People and Calendar, and SkyDrive. iOS Microsoft released a Windows Live Messenger application on the iOS App Store, which allows users on mobile devices running the iOS to communicate with their contacts via the Microsoft Messenger service. In addition to the instant messaging functionalities, the application also allows users to view their Messenger social feed, view their friends' Profile's, and integrate with Hotmail and Photos. Feature phone Windows Live also provides customised services specifically created for feature phones. It is offered via three channels — through Client-based (for Windows Mobile and other supported mobile devices such as Nokia phones), Web-based (for WAP or GPRS-enabled mobile web browsers), or SMS-based services. Search services Bing, a replacement of the search engine Live Search, was originally named Windows Live Search (and MSN Search prior to that) and was once part of the Windows Live family of services. Windows Live Search once occupied the homepage of Live.com, the domain for all Windows Live services. However, on March 21, 2007, Microsoft decided to separate its search developments from its Windows Live services family, forming part of the Live Search and Ad Platform. As part of this reorganization, the new search brand, Live Search, was consolidated with Microsoft adCenter, a part of Microsoft's Platform and Systems division. However, Microsoft recognised that there was a brand issue as the word "Live" continued to remain in the brand. As an effort to create a new identity for Microsoft's search services, on June 3, 2009, Live Search was officially rebranded as Bing. Developer services Live Connect is a collection of APIs and common controls that allow developers to have a deeper control and offers access to the core Windows Live services and data through open and easily accessible application programming interfaces (APIs). Live Connect is built on standard web technologies such as OAuth 2.0, Representational State Transfer (REST), and JavaScript Object Notation (JSON), and is designed to work with any technology or device. Live Connect unites the previously separate APIs of Windows Live into a single API that is based on industry standards and specifications. Discontinued services Software Microsoft has released several computer programs with "Windows Live" brand, a summary of which is included below. All except Windows Live OneCare are freeware and published in a software suite called Windows Essentials (formerly Windows Live Essentials). Essentials programs are designed to integrate well with each other, within Windows, and with other Windows Live services such as OneDrive and Outlook.com. Windows Live OneCare on the other hand, was a commercial consumers utility marketed with a software as a service licensing model. Windows Live Butterfly The Windows Live Butterfly awards program (formerly the MSN Butterfly program) was a program whose members were given the benefit of new Microsoft software to test before the beta releases went public and they were in direct contact with the program managers for Windows Live products. Microsoft had initiated the Windows Live Butterfly program in order to recognize the contributions made by exemplary beta testers. Prospective 'butterflies' were selected by the Windows Live product team and were nominated for a term of one year, after which they could be renominated. The Windows Live Butterfly program was closed in June 2009. User interface All Windows Live websites sport a common theme. Different themes have been used on the sites with each phase of product release, called "Waves". Each Wave has a set of online services and desktop programs (Windows Essentials). The web services are labelled by each Wave, for example, Hotmail Wave 4. The programs from Windows Essentials are usually called by a year number, for example, Windows Live Messenger 2011. Blue Vapor/Flair/Wave 1 Most original Windows Live applications and services used a visual theme known as Blue Vapor or Flair. Wave 2 With the public beta release of the Windows Live Wave 2 Suite, a new visual theme was released to enable the Aero transparency effect in Windows Vista. Wave 3 Microsoft released a set of new themes for their Windows Live Wave 3 services, which allows users to customize their pages on Windows Live using a set of pre-selected background pictures. Several of these themes are dynamic and change according to the time of day and the current weather condition of the user. Wave 4 In addition to the themes provided in Windows Live Wave 3, the release of Windows Live Wave 4 provided additional themes for users to customise their pages on Windows Live, with several dynamic themes that changes according to the time of day and weather conditions at the user's location. Several of these newly added themes are similar to wallpapers originating from Windows 7. In addition, the Windows Live Wave 4 header features a reorganised dynamic navigation menu that displays the number of the user's current online contacts and the number of unread e-mails, as well as an in-built Windows Live Web Messenger service allowing users to connect to the Microsoft Messenger service and Facebook chat service to chat with their online contacts while browsing any Windows Live properties using a web browser. See also In addition to Windows Live, which is mainly aimed at individuals, Microsoft brands other properties as "Live", including: Xbox Live (a multiplayer gaming and content-delivery system for Xbox) Games for Windows – Live (multiplayer gaming service for Microsoft Windows) Office Live. Office Live merged into Windows Live during the Wave 4 update. Microsoft merged Office Live into the Windows Live team in January 2009. References Microsoft websites MSN Web service providers Companies based in Palo Alto, California Computer-related introductions in 2005 Products and services discontinued in 2012

Operating System (OS)

UNIX Review UNIX Review was an American magazine covering technical aspects of the UNIX operating system and C programming. Recognized for its in-depth technical analysis, the journal also reported on industry confabs and included some lighter fare. History and profile It was founded in 1983. In 1985 it was acquired by Miller Freeman. The journal was renamed to UNIX Review's Performance Computing (UR/PC) Magazine with the April 1998 issue, and ceased publication in 2000. The online publication ceased in 2007. It was published by REVIEW Publications of Renton, Washington. The rights to the title passwd to United Business Media (formerly CMP Media), which was absorbed by Informa in 2018. Regular contributors Andrew Binstock, (editor in chief from 1991–1997), wrote "Word Wrap from the Editor" John Chisholm (1992-1995), wrote "Currents" column Stan Kelly-Bootle, writer of the "Devil's Advocate" column Ken Arnold, writer of "The C Advisor" column Rich Morin, writer of "The Human Factor" and "The Internet Notebook" columns Joe "Zonker" Brockmeier, writer of the "Tool of the Month" column Ed Schaefer, writer of the "Shell Corner" column Dinah McNutt, writer of the "Daemons and Dragons" column Cameron Laird, regular contributor Emmett Dulaney, regular contributor Marcel Gagné, regular contributor Eric Foster-Johnson, regular contributor References External links UNIX Review at the Wayback Machine internet archive 1983 establishments in Washington (state) 2000 disestablishments in Washington (state) Defunct computer magazines published in the United States Magazines established in 1983 Magazines disestablished in 2000 Magazines published in Washington (state) Unix history

Operating System (OS)

Das U-Boot Das U-Boot (subtitled "the Universal Boot Loader" and often shortened to U-Boot; see History for more about the name) is an open-source, primary boot loader used in embedded devices to package the instructions to boot the device's operating system kernel. It is available for a number of computer architectures, including 68k, ARM, Blackfin, MicroBlaze, MIPS, Nios, SuperH, PPC, RISC-V and x86. Functionality U-Boot is both a first-stage and second-stage bootloader. It is loaded by the system's ROM (e.g. onchip ROM of the ARM CPU) from a supported boot device, such as an SD card, SATA drive, NOR flash (e.g. using SPI or I²C), or NAND flash. If there are size constraints, U-Boot may be split into stages: the platform would load a small SPL (Secondary Program Loader), which is a stripped-down version of U-Boot, and the SPL would do initial hardware configuration and load the larger, fully featured version of U-Boot. Regardless of whether the SPL is used, U-Boot performs both first-stage (e.g., configuring memory controllers and SDRAM) and second-stage booting (performing multiple steps to load a modern operating system from a variety of devices that must be configured, presenting a menu for users to interact with and control the boot process, etc.). U-Boot implements a subset of the UEFI specification as defined in the Embedded Base Boot Requirements (EBBR) specification. UEFI binaries like GRUB or the Linux kernel can be booted via the boot manager or from the command-line interface. U-Boot runs a command-line interface on a console or a serial port. Using the CLI, users can load and boot a kernel, possibly changing parameters from the default. There are also commands to read device information, read and write flash memory, download files (kernels, boot images, etc.) from the serial port or network, manipulate device trees, and work with environment variables (which can be written to persistent storage, and are used to control U-Boot behavior such as the default boot command and timeout before auto-booting, as well as hardware data such as the Ethernet MAC address). Unlike PC bootloaders which obscure or automatically choose the memory locations of the kernel and other boot data, U-Boot requires its boot commands to explicitly specify the physical memory addresses as destinations for copying data (kernel, ramdisk, device tree, etc.) and for jumping to the kernel and as arguments for the kernel. Because U-Boot's commands are fairly low-level, it takes several steps to boot a kernel, but this also makes U-Boot more flexible than other bootloaders, since the same commands can be used for more general tasks. It's even possible to upgrade U-Boot using U-Boot, simply by reading the new bootloader from somewhere (local storage, or from the serial port or network) into memory, and writing that data to persistent storage where the bootloader belongs. U-Boot has support for USB, so it can use a USB keyboard to operate the console (in addition to input from the serial port), and it can access and boot from USB Mass Storage devices such as SD card readers. Data storage and boot sources U-Boot boots an operating system by reading the kernel and any other required data (e.g. device tree or ramdisk image) into memory, and then executing the kernel with the appropriate arguments. U-Boot's commands are actually generalized commands which can be used to read or write any arbitrary data. Using these commands, data can be read from or written to any storage system that U-Boot supports, which include: (Note: These are boot sources from which U-Boot is capable of loading data (e.g. a kernel or ramdisk image) into memory. U-Boot itself must be booted by the platform, and that must be done from a device that the platform's ROM or BIOS is capable of booting from, which naturally depends on the platform.) Onboard or attached storage SD card SATA SCSI I²C (e.g. EEPROMs or NOR flash) SPI (e.g. NOR or NAND flash) ONFI (raw NAND flash) eMMC (managed NOR or NAND flash) NVMe USB mass storage device Serial port (file transfer) Kermit S-Record YMODEM Network boot (optionally using DHCP, BOOTP, or RARP) TFTP NFS Compatible file systems U-Boot does not need to be able to read a filesystem in order for the kernel to use it as a root filesystem or initial ramdisk; U-Boot simply provides an appropriate parameter to the kernel, and/or copies the data to memory without understanding its contents. However, U-Boot can also read from (and in some cases, write to) filesystems. This way, rather than requiring the data that U-Boot will load to be stored at a fixed location on the storage device, U-Boot can read the filesystem to search for and load the kernel, device tree, etc., by pathname. U-Boot includes support for these filesystems: btrfs CBFS (coreboot file system) Cramfs ext2 ext3 ext4 FAT FDOS JFFS2 ReiserFS Squashfs UBIFS ZFS Device tree Device tree is a data structure for describing hardware layout. Using Device tree, a vendor might be able to use an unmodified mainline U-Boot on otherwise special purpose hardware. As also adopted by the Linux kernel, Device tree is intended to ameliorate the situation in the embedded industry, where a vast number of product specific forks (of U-Boot and Linux) exist. The ability to run mainline software practically gives customers indemnity against lack of vendor updates. History The project's origin is a 8xx PowerPC bootloader called 8xxROM written by Magnus Damm. In October 1999 Wolfgang Denk moved the project to SourceForge.net and renamed it to PPCBoot, because SF.net did not allow project names starting with digits. Version 0.4.1 of PPCBoot was first publicly released July 19, 2000. In 2002 a previous version of the source code was briefly forked into a product called ARMBoot, but was merged back into the PPCBoot project shortly thereafter. On October 31, 2002 PPCBoot−2.0.0 was released. This marked the last release under the PPCBoot name, as it was renamed to reflect its ability to work on other architectures besides the PPC ISA. PPCBoot−2.0.0 became U−Boot−0.1.0 in November 2002, expanded to work on the x86 processor architecture. Additional architecture capabilities were added in the following months: MIPS32 in March 2003, MIPS64 in April, Nios II in October, ColdFire in December, and MicroBlaze in April 2004. The May 2004 release of U-Boot-1.1.2 worked on the products of 216 board manufacturers across the various architectures. The current name Das U-Boot adds a German definite article, to create a bilingual pun on the classic 1981 German submarine film Das Boot, which takes place on a World War II German U-boat. It is free software released under the terms of the GNU General Public License. It can be built on an x86 PC for any of its intended architectures using a cross development GNU toolchain, for example crosstool, the Embedded Linux Development Kit (ELDK) or OSELAS.Toolchain. The importance of U-Boot in embedded Linux systems is quite succinctly stated in the book Building Embedded Linux Systems, by Karim Yaghmour, whose text about U-Boot begins, "Though there are quite a few other bootloaders, 'Das U-Boot', the universal bootloader, is arguably the richest, most flexible, and most actively developed open source bootloader available." Usages The ARM-based Chromebooks ship with U-Boot. The Celeron- and i5-based Chromebooks use it as payload for coreboot. The PowerPC based series of AmigaOne computers running AmigaOS use U-Boot, in particular the Sam440ep and Sam460ex by ACube Systems Srl, and the AmigaOne X5000 by A-Eon, the successor of the AmigaOne X1000. Ubiquiti Networks devices use U-Boot Amazon Kindle & Kobo eReader devices use U-Boot as their bootloader. TP-Link and several other OpenWRT/LEDE compatible MIPS based wireless routers use U-Boot for bootloading. Teltonika cellular routers use bootloader based on U-Boot. SpaceX's Falcon and Dragon both use U-Boot See also Comparison of boot loaders RedBoot Coreboot Barebox Notes References External links Barebox (formerly known as U-Boot-V2) Firmware Free boot loaders Free software programmed in C High-priority free software projects Software related to embedded Linux

Operating System (OS)

Mac OS X 10.1 Mac OS X 10.1 (code named Puma) is the second major release of macOS, Apple's desktop and server operating system. It superseded Mac OS X 10.0 and preceded Mac OS X 10.2. Version 10.1 was released on September 25, 2001 as a free update for Mac OS X 10.0 users. The operating system was handed out for no charge by Apple employees after Steve Jobs' keynote speech at the Seybold publishing conference in San Francisco. It was subsequently distributed to Mac users on October 25, 2001 at Apple Stores and other retail stores that carried Apple products. System requirements Supported computers: Power Mac G3 Power Mac G4 Power Mac G4 Cube iMac G3 eMac PowerBook G3, except for the original PowerBook G3 PowerBook G4 iBook RAM: 128 megabytes (MB) (unofficially 64 MB minimum) Hard Drive Space: 1.5 gigabytes (GB) Features Apple introduced many features that were missing from the previous version, as well as improving overall system performance. This system release brought some major new features to the Mac OS X platform: Performance enhancements — Mac OS X 10.1 introduced large performance increases throughout the system. Easier CD and DVD burning — better support in Finder as well as in iTunes DVD playback support — DVDs can be played in Apple DVD Player More printer support (200 printers supported out of the box) — One of the main complaints of version 10.0 users was the lack of printer drivers, and Apple attempted to remedy the situation by including more drivers, although many critics complained that there were still not enough. Faster 3D (OpenGL performs 20% faster) — The OpenGL drivers and handling were vastly improved in this version of Mac OS X, which created a large performance gap for 3D elements in the interface, and 3D applications. Improved AppleScript — The scripting interface now allows scripting access to many more system components, such as the Printer Center, and Terminal, thus improving the customizability of the interface. As well, Apple introduced AppleScript Studio, which allows a user to create full AppleScript applications in a simple graphical interface. Improved filehandling - The Finder was enhanced to optionally hide file extensions on a per-file basis. The Cocoa API was enhanced to allow developers to set traditional Mac type and creator information directly without relying on Carbon to do it. ColorSync 4.0, the color management system and API. Image Capture, for acquiring images from digital cameras and scanners. Menu Extras, a set of items the user can add to the system menu, replacing the supplied Dock Extras from Mac OS X 10.0 Cheetah. Apple switched to using Mac OS X as the default on all then-new Macs with the 10.1.2 release. Applications found on Mac OS X 10.1 Puma Address Book AppleScript Calculator Chess Clock CPU Monitor DVD Player Image Capture iMovie Internet Connect Internet Explorer for Mac iTunes Mail Preview Process Viewer (now Activity Monitor) QuickTime Player Sherlock Stickies System Preferences StuffIt Expander TextEdit Terminal Release history References External links Mac OS X v10.1 review at Ars Technica from apple.com from apple.com 1 PowerPC operating systems 2001 software Computer-related introductions in 2001

Operating System (OS)

Windows Mobile Windows Mobile is a discontinued family of mobile operating systems developed by Microsoft for smartphones and personal digital assistants. Its origin dated back to Windows CE in 1996, though Windows Mobile itself first appeared in 2000 as Pocket PC 2000 which ran on Pocket PC PDAs. It was renamed "Windows Mobile" in 2003, at which point it came in several versions (similar to the desktop versions of Windows) and was aimed at business and enterprise consumers. When initially released in the mid-2000s, it was to be the portable equivalent of what Windows desktop OS was: a major force in the then-emerging mobile/portable areas. Following the rise of newer smartphone OSs (iOS and Android) Windows Mobile never equalled the success and faded rapidly in the following years. By February 2010, Microsoft announced Windows Phone to supersede Windows Mobile with a more modern take on the industry. As a result, Windows Mobile has been deprecated. Windows Phone is incompatible with Windows Mobile devices and software. The last version of Windows Mobile, released after the announcement of Windows Phone, was 6.5.5. After this, Microsoft ceased development on Windows Mobile in order to concentrate on Windows Phone. Features Most versions of Windows Mobile have a standard set of features, such as multitasking and the ability to navigate a file system similar to that of Windows 9x and Windows NT, including support for many of the same file types. Similarly to its desktop counterpart, it comes bundled with a set of applications that perform basic tasks. Internet Explorer Mobile is the default web browser, and Windows Media Player is the default media player used for playing digital media. The mobile version of Microsoft Office is the default office suite. Internet Connection Sharing, supported on compatible devices, allows the phone to share its Internet connection with computers via USB and Bluetooth. Windows Mobile supports virtual private networking over PPTP protocol. Most devices with mobile connectivity also have a Radio Interface Layer. The Radio Interface Layer provides the system interface between the Cell Core layer within the Windows Mobile OS and the radio protocol stack used by the wireless modem hardware. This allows OEMs to integrate a variety of modems into their equipment. The user interface changed dramatically between versions, only retaining similar functionality. The Today Screen, later called the Home Screen, shows the current date, owner information, upcoming appointments, e-mails, and tasks. The taskbar displays the current time as well as the volume level. Devices with a cellular radio also show the signal strength on said taskbar. History Windows Mobile is based on the Windows CE kernel and first appeared as the Pocket PC 2000 operating system. It includes a suite of basic applications developed with the Microsoft Windows API, and is designed to have features and appearance somewhat similar to desktop versions of Windows. It allowed third party developers to develop software for Windows Mobile with no restrictions imposed by Microsoft. Software applications were purchasable from Windows Marketplace for Mobile during the service's lifespan. Most early Windows Mobile devices came with a stylus, which can be used to enter commands by tapping it on the screen. The primary touch input technology behind most devices were resistive touchscreens which often required a stylus for input. Later devices used capacitive sensing which does not require a stylus. Along with touchscreens, a large variety of form factors existed for the platform. Some devices featured slideout keyboards, while others featured minimal face buttons. Windows CE Microsoft's work on handheld portable devices began with research projects in 1990, with the work on Windows CE beginning in 1992. Initially, the OS and the user interface were developed separately. With Windows CE being based on Windows 95 code and a separate team handing the user interface which was codenamed WinPad (later Microsoft At Work for Handhelds). Windows 95 had strong pen support making porting easy; with some saying "At this time, Windows 95 offers outstanding pen support. It is treating pens right for the first time." WinPad was delayed due to price and performance issues, before being scrapped in early 1995 due to touchscreen driver problems relating to WriteTouch technology, made by NCR Microelectronic Products. Although WinPad was never released as a consumer product, Alpha builds were released showcasing many interface elements. During development of WinPad a separate team worked on a project called Pulsar; designed to be a mobile communications version of WinPad, described as a "pager on Steroids". This project was also canceled around the same time as WinPad. The two disbanded groups would form the Pegasus project in 1995. Pegasus would work on the hardware side of the Windows CE OS, attempting to create a form factor similar to a PC-esque PDA like WinPad, with communications functionality like Pulsar. Under the name Handheld PC, a hardware reference guide was created and devices began shipping in 1996, although most of these device bore little resemblance to the goal of a pen-based touchscreen handheld device. A specification for a smaller form factor under the name Palm-size PC was released in 1998. Pocket PC 2000 Pocket PC 2000, originally codenamed "Rapier", was released on April 19, 2000, and was based on the Windows CE 3.0 kernel. It was the debut of what was later dubbed the Windows Mobile operating system, and meant to be a successor to the operating system aboard Palm-size PCs. It retained backwards compatibility with such Palm-size PC applications. Pocket PC 2000 was intended mainly for Pocket PC devices; however, several Palm-size PC devices had the ability to be updated also. While, several Pocket PC 2000 phones were released, Microsoft's smartphone hardware platform was not yet created. The only resolution supported by this release was 240×320 (QVGA). Removable storage card formats that were supported were CompactFlash and MultiMediaCard. At this time Pocket PC devices had not been standardized with a specific CPU architecture. As a result, Pocket PC 2000 was released on multiple CPU architectures; SH-3, MIPS, and ARM. Infrared (IR) File beaming capability was among the original hardware features. The original Pocket PC operating system had similar appearance to Windows 98, Windows Me, and Windows 2000 operating systems. Crucially, unlike the interface on predecessing Palm-size PC, the Pocket PC had a less cluttered interface more suitable for a mobile device. Pocket PC 2000 is unsupported as of September 10, 2007. This initial release had multiple built-in applications, many of them similarly branded to match their desktop counterparts; such as Microsoft Reader, Microsoft Money, Pocket Internet Explorer and Windows Media Player. A version of Microsoft Office called Pocket Office was also bundled and included Pocket Word, Pocket Excel and Pocket Outlook. Notes, a note-taking app saw its first release and would be supported by most later versions of Windows Mobile. Intelligent character recognition support allowed Notes to distinguish styles of handwriting to be learned by the OS during processing to improve accuracy and recognition levels. Pocket PC 2002 Pocket PC 2002, originally codenamed "Merlin", was released in October 2001, and like Pocket PC 2000, was based on the Windows CE 3.0 kernel. Although targeted mainly for 240×320 (QVGA) Pocket PC devices, Pocket PC 2002 was also used for Pocket PC phones, and for the first time, smartphones. These Pocket PC 2002 Smartphones were mainly GSM devices. With future releases, the Pocket PC and Smartphone lines would increasingly collide as the licensing terms were relaxed allowing OEMs to take advantage of more innovative, individual design ideas. Aesthetically, Pocket PC 2002 was meant to be similar in design to the then newly released Windows XP. Newly added or updated programs include Windows Media Player 8 with streaming capability; MSN Messenger, and Microsoft Reader 2, with Digital rights management support. Upgrades to the bundled version of Office Mobile include a spell checker and word count tool in Pocket Word and improved Pocket Outlook. Connectivity was improved with file beaming on non-Microsoft devices such as Palm OS, the inclusion of Terminal Services and Virtual private networking support, and the ability to synchronize folders. Other upgrades include an enhanced UI with theme support and savable downloads and WAP in Pocket Internet Explorer. Windows Mobile 2003 Originally called Pocket PC 2003 but later renamed Windows Mobile 2003, originally codenamed "Ozone", was released on June 23, 2003, was based on the Windows CE 4.x kernel, and was the first release under the Windows Mobile banner. It came in four editions: "Windows Mobile 2003 for Pocket PC Premium Edition", "Windows Mobile 2003 for Pocket PC Professional Edition", "Windows Mobile 2003 for Smartphone" and "Windows Mobile 2003 for Pocket PC Phone Edition". The last was designed especially for Pocket PCs which include phone functionalities. The Professional Edition was used in Pocket PC budget models. It lacked a number of features that were in the Premium Edition, such as a client for L2TP/IPsec VPNs. Windows Mobile 2003 was powered by Windows CE 4.20. Communications interface were enhanced with Bluetooth device management, which allowed for Bluetooth file beaming support, Bluetooth headset support and support for Bluetooth add-on keyboards. A pictures application with viewing, cropping, e-mail, and beaming support was added. Multimedia improvements included MIDI file support as ringtones in Phone Edition and Windows Media Player 9.0 with streaming optimization. A puzzle game titled Jawbreaker is among the preinstalled programs. GAPI was included with this release to facilitate the development of games for the platform. Other features/built-in applications included the following: enhanced Pocket Outlook with vCard and vCal support, improved Pocket Internet Explorer and SMS reply options for Phone Edition. Windows Mobile 2003 SE Windows Mobile 2003 Second Edition, also known as "Windows Mobile 2003 SE", was released on March 24, 2004, was based on the Windows CE 4.x kernel, and first offered on the Dell Axim x30. This was the last version which allowed users to back up and restore an entire device through ActiveSync. This upgrade allows users to switch between portrait and landscape modes and introduces a single-column layout in Pocket Internet Explorer. It includes support for Wi-Fi Protected Access (WPA) and new screen resolutions: 640×480 (VGA), 240×240, and 480×480. Windows Mobile 5 Windows Mobile 5.0, originally codenamed "Magneto", was released at Microsoft's Mobile and Embedded Developers Conference 2005 in Las Vegas, May 9–12, 2005, and was based on the Windows CE 5.0 kernel. Microsoft offered mainstream support for Windows Mobile 5 through October 12, 2010, and extended support through October 13, 2015. It was first offered on the Dell Axim x51. It used the .NET Compact Framework 1.0 SP3, an environment for programs based on .NET. Windows Mobile 5.0 included Microsoft Exchange Server "push" functionality improvements that worked with Exchange 2003 SP2. The "push" functionality also required vendor/device support. With AKU2 software upgrades all WM 5.0 devices supported DirectPush. Other features included an enhanced battery-saving capability called persistent storage capability. Previously up to 50% (enough for 72 hours of storage) of battery power was reserved just to maintain data in volatile RAM. This continued the trend of Windows-based devices moving from using RAM as their primary storage medium to the use of a combination of RAM and flash memory (in use, no distinction between the two is obvious to users). Programs and frequently accessed data run in RAM, while most storage is in the flash memory. The OS seamlessly moves data between the two as needed. Everything is backed up in the flash memory, so unlike prior devices, WM5 devices lose no data if power is lost. New to 5.0, OS updates were released as adaptation kit upgrades, with AKU 3.5 being the final released. Windows Mobile 5 comes with Microsoft Office Mobile which includes PowerPoint Mobile, Excel Mobile with graphing capability and Word Mobile with the ability to insert tables and graphics. Media management and playback was enhanced with Picture and Video package, which converged the management of videos and pictures and Windows Media Player 10 Mobile. Among new hardware features were enhanced Bluetooth support, default QWERTY keyboard-support and a management interface for Global Positioning System (GPS). Improvements were made to ActiveSync 4.2 with 15% increased synchronization speed. Business customers benefited from a new error reporting facility similar to that present in desktop and server Windows systems. Caller ID now supports photos so a user can apply an image to each contact to show when a call is received. DirectShow was also natively added. This release was the first to include DirectDraw with hardware acceleration, replacing the deprecated graphics component of GAPI. Windows Mobile 5.0 requires at least 64 MB of ROM (it's advisable to have 64 MB of RAM), and the device must run an ARM compatible processor such as the Intel XScale or the Samsung and Texas Instruments ARM compatibles. Windows Mobile 6 Windows Mobile 6, formerly codenamed "Crossbow", was released on February 12, 2007 at the 3GSM World Congress 2007and was based on the Windows CE 5.2 kernel. It comes in three different versions: "Windows Mobile 6 Standard" for Smartphones (phones without touchscreens), "Windows Mobile 6 Professional" for Pocket PCs with phone functionality, and "Windows Mobile 6 Classic" for Pocket PCs without cellular radios. Windows Mobile 6 is powered by Windows CE 5.0 (version 5.2) and is strongly linked to the then newly introduced Windows Live and Exchange 2007 products. Windows Mobile 6 Standard was first offered on the Orange's SPV E650, while Windows Mobile 6 Professional was first offered on the O2's Xda Terra. Aesthetically, Windows Mobile 6 was meant to be similar in design to the then newly released Windows Vista. Functionally, it works much like Windows Mobile 5, but with much better stability. Along with the announcement of Office Mobile 6.1 with support for Office 2007 document formats (pptx, docx, xlsx); OneNote Mobile, a companion to Microsoft Office OneNote was added to the already installed version. In addition to the newly included programs with Office Mobile improvements were made to existing applications. Such as HTML email support in Outlook Mobile. A large number of Windows Mobile users are enterprise users business environments were targeted. With Server Search on Microsoft Exchange 2007, Out of Office Replies with Microsoft Exchange 2007, and search ability for contacts in an Exchange Server Address Book being implemented. To aid development for programmers, .NET Compact Framework v2 SP2 is now preinstalled with the OS. Developers and users also have access to Microsoft SQL Server 2005 Compact Edition for storage and retrieval of information. AJAX, JavaScript, and XMLDOM support were added to Internet Explorer Mobile along with improved devicewide Internet Sharing. Communication abilities were further enhanced with a new Microsoft Bluetooth Stack and VoIP (Internet calling) support with AEC (Acoustic Echo Cancelling) and MSRT audio codec. To improve security Microsoft added Storage Card Encryption so that encryption keys are lost if device is cold-booted. Further updates both, security and feature, can now also be provided using Operating System Live Update. Among other improvements: 320×320 and 800×480 (WVGA) screen resolutiopport (The S01SH or "Em One" by Sharp was the first and only device to have an 800×480 screen on WM5), Improved Remote Desktop access (available for only certain Pocket PCs), Customer Feedback option, Smartfilter for searching within programs and Unlicensed Mobile Access (UMA) support for select operators. Windows Mobile 6.1 Windows Mobile 6.1 was announced April 1, 2008, and was based on the Windows CE 5.x kernel. It is a minor upgrade to the Windows Mobile 6 platform with various performance enhancements and a redesigned Home screen featuring horizontal tiles that expand on clicking to display more information, although this new home screen is featured only on Windows Mobile Standard edition. This was not supported in the Professional edition. Several other changes such as threaded SMS, full page zooming in Internet Explorer and 'Domain Enroll' were also added, along with a "mobile" version of the Microsoft OneNote program and an interactive "Getting Started" wizard. Domain Enroll is functionality to connect the device to System Center Mobile Device Manager 2008, a product to manage mobile devices. Windows Mobile 6.1 also had improved bandwidth efficiency in its push-email protocol ActiveSync up to 40%; this considerably improved battery life in many devices. Aside from the visual and feature distinctions, the underlying CE versions can be used to differentiate WM 6.0 from WM 6.1. The version of Windows CE in WM 6.0 is 5.2.*, where the third and final number being a four-digit build ID (e.g. 5.2.1622 on HTC Wing). In WM 6.1, the CE version is 5.2.* with a five-digit build number (e.g. 5.2.19216 on Palm Treo 800w). Windows Mobile 6.5 Windows Mobile 6.5 is a stopgap update to Windows Mobile 6.1, based on the Windows CE 5.x kernel, intended to bridge the gap between version 6.1 and the then yet-to-be released Windows Mobile 7 (Later canceled in favor of Windows Phone 7), that arrived in 2010. It was never part of Microsoft's mobile phone roadmap, and has been described by its chief executive, Steve Ballmer, as "not the full release Microsoft wanted" until the multi-touch-enabled Windows Mobile 7 (now replaced by Windows Phone) arrived in 2010. Ballmer also indicated that the company "screwed up with Windows Mobile", he lamented that Windows Mobile 7 was not yet available and that the Windows Mobile team needed to try to recoup losses. Microsoft unveiled this version at the 2009 Mobile World Congress in February, and several devices were supplied with it. It was released to manufacturers on May 11, 2009; the first devices running the operating system appeared in late October 2009. Several phones that officially shipped with Windows Mobile 6.1 can be officially updated to Windows Mobile 6.5. This update includes some significant new added features, such as a revamped GUI, a new Today screen resembling that of Microsoft's Zune player with vertically scrollable labels (called 'Titanium') in terms of functionality with a styling similar to that of Windows 7. WM 6.5 also includes the new Internet Explorer Mobile 6 browser, with improved interface. Along with Windows Mobile 6.5, Microsoft announced several cloud computing services codenamed "SkyBox", "SkyLine", "SkyMarket". "SkyBox" has been confirmed as My Phone, while "SkyMarket" has been confirmed as Windows Marketplace for Mobile. This version was designed mainly for easier finger usage. Some reviewers have noted interface inconsistencies, with some applications having small buttons making them harder to operate using only a finger. Whilst this version of Windows Mobile does not natively support capacitive screens, mobile manufacturers have been able to use them on their devices. In the months following this release, development shifted from Windows Mobile to its successor Windows Phone. As such no major upgrades were planned or released, although three minor updates; 6.5.1, 6.5.3 and 6.5.5; were made to satisfy consumers during the transition period. 6.5.1 brings larger user interface elements, including icon based soft buttons (rather than text based), an updated contacts app, native support for A-GPS, improved threaded text messaging, and performance improvements. It was unofficially ported to several Windows Mobile phones. The second minor update was announced on February 2, 2010, along with the Sony Ericsson Aspen which was the first phone to use this version. 6.5.3 continues the trend of attempting to provide a more finger-friendly user interface with several new usability features such as native support for multitouch; although device maker HTC Corporation created proprietary work-arounds to allow multi-touch to work on some applications it installed on its HD2 handset (However, Microsoft applications on this handset, such as the Internet Explorer web browser, did not support multi-touch.) and drag-and-drop start menu icons. Touchable tiles replaced soft keys." Internet Explorer Mobile 6 has also received some major updates including decreased page load time, improved memory management and gesture smoothing. As with other updates it was unofficially ported to some other devices. Additional features include threaded email and Office Mobile 2010. The last minor update and the last released version is 6.5.5. It first leaked in January 2010, and was unofficially ported to some Windows Mobile phones. The name Windows Mobile 6.5.5 has been applied to these newer builds, although this name remained unconfirmed by Microsoft. Although Microsoft released a similarly-named Windows 10 Mobile in 2015, this operating system is unrelated to the former Windows Mobile operating systems. Hardware There are three main versions of Windows Mobile for various hardware devices: Windows Mobile Professional runs on smartphones with touchscreens, Windows Mobile Standard runs on mobile phones without touchscreens, Windows Mobile Classic which runs on personal digital assistant or Pocket PCs. Windows Mobile for Automotive and Windows Mobile software for Portable Media Centers are among some specialty versions of the platform. Microsoft had over 50 handset partners, when Windows Mobile was still being shipped on new devices. 80% of the 50 million Windows Mobile devices that were made from launch to February 2009 were built by one contract manufacturing group, HTC, which makes handsets for several major companies under their brands, and under its own brand. Embedded Handheld On January 10, 2011, Microsoft announced Windows Embedded Handheld 6.5. The operating system has compatibility with Windows Mobile 6.5 and is presented as an enterprise handheld device, targeting retailers, delivery companies, and other companies that rely on handheld computing. Unlike Windows Phone, Windows Embedded Handheld retains backward compatibility with legacy Windows Mobile applications. Pocket PCs Pocket PCs and personal digital assistants were originally the intended platform for Windows Mobile. These were grouped into two main categories: devices that lacked mobile phone capabilities, and those that included it. Beginning with version 6 devices with this functionality ran "Windows Mobile 6 Professional" and those that lacked it ran "Windows Mobile 6 Classic". Microsoft had described these devices as "a handheld device that enables you to store and retrieve e-mail, contacts, appointments, play multimedia files, games, exchange text messages with MSN Messenger, browse the Web, and more". From a technical standpoint Microsoft also specified various hardware and software requirements such as the inclusion of a touchscreen and a directional pad or touchpad. Smartphones Smartphones were the second hardware platform after Pocket PC to run Windows Mobile, and debuted with the release of Pocket PC 2002. Although in the broad sense of the term "Smartphone", both Pocket PC phones and Microsoft branded Smartphones each fit into this category. Microsoft's use of the term "Smartphone" includes only more specific hardware devices that differ from Pocket PC phones. Such Smartphones were originally designed without touchscreens, intended to be operated more efficiently with only one hand, and typically had lower display resolution than Pocket PCs. Microsoft's focus for the Smartphone platform was to create a device that functioned well as a phone and data device in a more integrated manner. Market share Windows Mobile's share of the smartphone market grew from its inception while new devices were being released. After peaking in 2007, it saw decline year-on-year. In Q1 2003, Windows Mobile was the third largest operating system in the smart handheld market, behind Symbian and Palm OS. In Q1 2004, Windows Mobile accounted for 23% of worldwide smartphone sales. Windows Mobile was projected in 2005 to overtake Symbian to become the leading mobile OS by 2010. In Q3 2004, Windows Mobile (CE) surpassed Palm OS to become the largest PDA operating system. In Q4 2005 Microsoft shipped 2.2 million PDAs, which increased to 3.5 million in the same quarter the following year. Windows Mobile saw year over year growth between 2005 and 2006 of 38.8% which according to Gartner "helped Windows Mobile to solidify its stronghold on the market". But by 2008, its share had dropped to 14%. Microsoft licensed Windows Mobile to four out of the world's five largest mobile phone manufacturers, with Nokia being the exception. Gartner research data showed that while the total smartphone industry grew 27% between 2008 and 2009, Windows Mobile's share of the smartphone market fell 2.7% in that same period. It also decreased by 20% in Q3 2009. At one time Windows Mobile was the most popular handset for business use, but by 2009 this was no longer the case; 24% of planned business deployments of mobile application in the United States were for Windows Mobile, putting it in 3rd place, behind BlackBerry (61%) and iPhone OS (27%); In February 2009, Microsoft signed a deal with the third largest mobile phone maker, LG Electronics, to license Windows Mobile OS on 50 upcoming LG smartphone models. But in September 2009, Palm, Inc. announced it would drop Windows Mobile from its smartphone line-up. Gartner estimated that by the third quarter of 2009 Windows Mobile's share of worldwide smartphone sales was 7.9%. By August 2010, it was the least popular smartphone operating system, with a 5% share of the worldwide smartphone market (after Symbian, BlackBerry OS, Android and iOS). An October 2009 report in DigiTimes said that Acer will shift its focus from Windows Mobile to Google Android. The New York Times reported in 2009 that Windows Mobile "is foundering", as cellphone makers desert it in favor of Google's Android phone platform. It cited the difficulties in Microsoft's business model, which involves charging handset manufacturers up to $25 for each copy of Windows Mobile, while rival Google gives away Android for free. From late 2009 analysts and media reports began to express concerns about the future viability of the Windows Mobile platform, and whether Microsoft would keep supporting it into the future. Samsung announced in November 2009 that it would phase out the Windows Mobile platform, to concentrate on its own Bada operating system, Google's Android, and Microsoft's Windows Phone. Software development Software could be developed by third parties for the Windows Mobile operating system. Developers had several options for deploying mobile applications. These included writing native code with Visual C++, managed code that worked with the .NET Compact Framework, writing code in Tcl-Tk with eTcl, GCC using CeGCC, Python using PythonCE or server-side code that could be deployed using Internet Explorer Mobile or a mobile client on a user's device. The .NET Compact Framework was a subset of the .NET Framework and hence shared many components with software development on desktop clients, application servers, and web servers which had the .NET Framework installed, thus integrating networked computing space. To aid developers Microsoft released software development kits (SDKs) that worked in conjunction with their Visual Studio development environment. These SDKs included emulator images for developers to test and debug their applications while writing them. Software could be tested on a client machine directly or be downloaded to a device. Microsoft also distributed Visual Studio 2008 / 2005 Professional Editions, and server/database counterparts to students as downloads free of charge via its DreamSpark program. Third party integrated development environments could also be used to write software such as Lazarus, Resco MobileForms Toolkit, Lexico, NS Basic and Basic4ppc. Some third party development environments allowed coding to be done on the device itself without the need for a computer. Developer communities have used the SDK to port later versions of Windows Mobile OS to older devices and making the OS images available for free, thus providing the devices with newer feature sets. Microsoft had tolerated this procedure for some time but decided in February 2007 to ask developers to take their OS images off the net, which in turn raised discussions. At the same time Microsoft offered upgrades to Windows Mobile 6 versions to manufacturers for free. On July 5, 2009, Microsoft opened a third-party application distribution service called Windows Marketplace for Mobile. In 2011, Windows Marketplace for Mobile stopped accepting new admissions. and then fully closed on May 9, 2012. Connectivity In the early years of Windows Mobile devices were able to be managed and synced from a remote computer using ActiveSync; a data synchronization technology and protocol developed by Microsoft, originally released in 1996. This allowed servers running Microsoft Exchange Server, or other third party variants, to act as a personal information manager and share information such as email, calendar appointments, contacts or internet favorites. With the release of Windows Vista, ActiveSync was replaced with Windows Mobile Device Center. Device Center is included with Vista and Windows 7 and provides many front end enhancements, allowing a home user to sync PIM information with Microsoft Outlook 2003 and later, photos from Windows Photo Gallery, videos or music from Windows Media Player and favorites with Internet Explorer; without the need for a server back end. Devices at this time also included a base driver compatible with Mobile Device Center so a user can connect to a computer without a need for any configuration. See also List of defunct consumer brands References External links Windows Mobile Team Blog Windows CE Microsoft franchises Mobile operating systems Defunct consumer brands Discontinued products ARM operating systems Discontinued Microsoft operating systems Discontinued versions of Microsoft Windows

Operating System (OS)

MVS (disambiguation) MVS is an IBM mainframe computer operating system, commonly known as Multiple Virtual Storage. The acronym MVS may also refer to: Maritime Volunteer Service A UK Charity supplying Maritime Training and Support Marquez Valdes-Scantling, NFL wide receiver Metal vapor synthesis a technique in chemistry Mezinárodní všeodborový svaz, a Czechoslovak trade union federation Microsoft Visual Studio Minimum variance set - the set of attainable investment portfolios which minimise risk Ministry of Internal Affairs of Ukraine (Ministerstvo Vnutrishnikh Sprav - ) Mobile Video Streaming Mobile Visual Search Mucuri Airport, in Buenos Aires (IATA code MVS) MVS Comunicaciones, a Mexican media company Neo Geo MVS arcade game system from SNK

Operating System (OS)

Label (Mac OS) In Apple's Macintosh operating systems, labels are a type of seven distinct colored and named parameters of metadata that can be attributed to items (files, folders and disks) in the filesystem. Labels were introduced in Macintosh System 7, released in 1991, and they were an improvement of the ability to colorize items in earlier versions of the Finder. Labels remained a feature of the Macintosh operating system through the end of Mac OS 9 in late 2001, but they were omitted from Mac OS X versions 10.0 to 10.2, before being reintroduced in version 10.3 in 2003, though not without criticism. During the short time period when Mac OS X lacked labels, third-party software replicated the feature. In classic Mac OS In classic Mac OS versions 7 through 9, applying a label to an item causes the item's icon to be tinted in that color when using a color computer monitor (as opposed to the black-and-white monitors of early Macs), and labels can be used as a search and sorting criterion. There is a choice of seven colors because three bits are reserved for the label color: 001 through 111, and 000 for no label. The names of the colors can be changed to represent categories assigned to the label colors. Both label colors and names can be customized in the classic Mac OS systems; however, Mac OS 8 and 9 provided this functionality through the Labels tab in the Finder Preferences dialog, while System 7 provided a separate Labels control panel. Labels in Mac OS 9 and earlier, once customized, were specific to an individual install; booting into another install, be it on another Mac or different disk would show different colors and names unless set identically. A colorless label could be produced by changing a label's color to black or white. In Mac OS X and later Mac OS X versions 10.3 to 10.8 apply the label color to the background of item names, except when an item is selected in column view, which changes the item name to the standard highlight color except for a label-colored dot after the name. Beginning in OS X 10.9, the label-colored background of item names is replaced with a small label-colored dot, and becomes a kind of tag. Relation to tags The Mac operating system has allowed users to assign multiple arbitrary tags as extended file attributes to any item ever since OS X 10.9 was released in 2013. These tags coexist with the legacy label system for backward compatibility, so that multiple colored (or colorless) tags can be added to a single item, but only the last colored tag applied to an item will set the legacy label that will be seen when viewing the item in the older operating systems. Labeled items that were created in the older operating systems will superficially seem to be tagged in OS X 10.9 and later even though they are only labeled and lack the newer tag extended file attributes (until they are edited in the new system). Since label colors can be changed in classic Mac OS but are standardized and unchangeable in the newer operating systems, someone who wants to synchronize the label colors between a classic and modern system can change the label colors in classic Mac OS to match the newer system. See also References MacOS

Operating System (OS)

IBM System/360 Model 44 The IBM System/360 Model 44 is a specialized member of the IBM System/360 family, with a variant of the System/360 computer architecture, designed for scientific computing, real-time computing, process control and numerical control (NC). The Model 44 was announced August 16, 1965 and withdrawn September 24, 1973. Architecture The base Model 44 lacks the storage-to-storage character and decimal instruction sets of a standard System/360, however an "extended instruction set" feature was available to provide the missing instructions. The machine features four unique instructions: Change Priority Mask (CHPM), Load PSW Special (LPSX), Read Direct Word (RDDW), and Write Direct Word (WRDW). The system comes with four memory sizes: E (32 KiB), F (64 KiB), G (128 KiB), and H (256 KiB), with an access time of 1 μs, which puts it closer to the Model 65 (.75 μs) than the Model 50 (2.0 μs). Storage protection is an optional feature. General purpose registers are normally located in a non-addressable portion of 1 μs core storage termed "bump storage". For added speed, the general purpose registers can be implemented in Solid Logic Technology (SLT) circuitry with an access time of .25 μs. A unique feature of the Model 44 is "variable-length precision floating point arithmetic". It has the same short floating-point instructions and long floating-point instructions as the other models in the System/360 line, but it also has a rotary switch on the front panel which can be used to set the precision of long floating-point numbers. The mantissa portion of long floating-point numbers can be chosen as 32, 40, 48, or 56 bits, with 56 bits being the standard value. Whatever the setting, long floating-point numbers still occupy 64 bits in memory (the first eight bits are the sign and the exponent); the setting only leads, when it was less than 56 bits, to long floating-point operations ignoring some of the least significant bits of these numbers. This provides an improvement in speed when greater precision is not needed. An optional feature provides six external interrupt lines. The direct word feature allows the transfer of a full 32-bit word of information between an external device and main storage. This differs from the standard System/360 direct control feature which transfers a single byte. The Write Direct Word instruction places the contents of a word in memory as static signals on the 32 direct-out lines and uses the I2 field of the instruction as up to eight timing pulses. The Read Direct Word reads the 32 direct-in lines into memory and sends the I2 field as timing pulses. Write Direct Word ('B4'x): WRDW D1(B1),I2 Read Direct Word  ('B5'x): RDDW D1(B1),I2 The direct data channel feature provides a fast, simple data transfer capability. Controlled by standard System/360 I/O instructions and commands, it allows the connection of external devices that perform word-by-word data transfers with the Model 44 CPU at transfer rates up to 4 MiB/s. The priority interrupt feature adds thirty-two interrupt levels to the standard five. This uses locations '800'x to '9FF'x for the old and new program status word locations. An eight bit interrupt description from the interrupting device is stored in bit positions 24 to 31 of the corresponding old PSW. Bits 16-23 of the new PSW are used as a mask which is XORed with the interrupt description to modify the address from the new PSW, effectively allowing indexing into a jump table for the interrupt according to data sent by the device. The interrupts are numbered from 0 (highest priority) to 31 (lowest); a higher priority interrupt can interrupt processing of a lower priority. A 32 bit Priority Mask Register, set by the Change Priority Mask instruction, can be used to selectively mask interrupts to keep them in pending status until the mask is reset. The instruction can enable levels tagged by 1 bits, disable levels tagged by 0 bits cancel levels tagged by 1 bits, or cancel and enable levels tagged by 1 bits depending on the value of the I2 field. The Load PSW Special instruction is used to exit an interrupt routine resume the next highest priority routine or non-interrupt code. Load PSW Special ('B2'x): LPSX D1(B1),I2 I2 is reserved and should be zero. Change Priority Mask ('B3'x): CHPM D1(B1),I2 The high order two bits of the I2 field are called the mask bit and the cancel bit.The remainder of the I2 field is reserved and should be zero. (mask bit) (cancel bit) Function 1 0 Enable levels tagged by 1 bits 0 0 Disable levels tagged by 0 bits 0 1 Cancel levels tagged by 1 bits 1 1 Cancel and enable levels tagged by 1 bits Peripherals The Model 44 can support up to one standard and two high-speed System/360 multiplexer channels in addition to integrated adapters for the single disk storage and the console 1052 printer/keyboard. A unique feature of the Model 44 is its integrated single disk storage drive which uses the IBM 2315 cartridge and provides 1,171,200 bytes of removable disk storage built right into the CPU. A second integrated drive is available as an option. The Model 44 Programming System (M44PS) uses this drive as a systems residence device. Software The Model 44 Programming System software includes a supervisor, utility programs, assembler, FORTRAN IV compiler, and a library of scientific subroutines. Notes References System/360 Model 44

Operating System (OS)

MacOS Server macOS Server, formerly Mac OS X Server and OS X Server, is a series of Unix-like server operating systems developed by Apple Inc., based on macOS and later add-on software packages for the latter. macOS Server adds server functionality and system administration tools to macOS and provides tools to manage both macOS-based computers and iOS-based devices. Versions of Mac OS X Server prior to version 10.7 “Lion” were sold as complete, standalone server operating systems; starting with Mac OS X 10.7 “Lion,” Mac OS X Server (and its successors OS X Server and macOS Server) have been offered as add-on software packages, sold through the Mac App Store, that are installed on top of a corresponding macOS installation. macOS Server at one point provided network services such as a mail transfer agent, AFP and SMB servers, an LDAP server, and a domain name server, as well as server applications including a Web server, database, and calendar server. The latest version of macOS server only includes functionality related to user and group management, Xsan, and mobile device management through profiles. Overview Mac OS X Server was provided as the operating system for Xserve computers, rack mounted server computers designed by Apple. Also, it was optionally pre-installed on the Mac Mini and Mac Pro and was sold separately for use on any Macintosh computer meeting its minimum requirements. macOS Server versions prior to Lion are based on an open source foundation called Darwin and use open industry standards and protocols. Versions Mac OS X Server 1.0 (Rhapsody) The first version of Mac OS X was Mac OS X Server 1.0. Mac OS X Server 1.0 was based on Rhapsody, a hybrid of OPENSTEP from NeXT Computer and Mac OS 8.5.1. The GUI looked like a mixture of Mac OS 8's Platinum appearance with OPENSTEP's NeXT-based interface. It included a runtime layer called Blue Box for running legacy Mac OS-based applications within a separate window. There was discussion of implementing a 'transparent blue box' which would intermix Mac OS applications with those written for Rhapsody's Yellow Box environment, but this would not happen until Mac OS X's Classic environment. Apple File Services, Macintosh Manager, QuickTime Streaming Server, WebObjects, and NetBoot were included with Mac OS X Server 1.0. It could not use FireWire devices. The last release is Mac OS X Server 1.2v3. Mac OS X Server 10.0 (Cheetah) Released: May 21, 2001 Mac OS X Server 10.0 included the new Aqua user interface, Apache, PHP, MySQL, Tomcat, WebDAV support, Macintosh Manager, and NetBoot. Mac OS X Server 10.1 (Puma) Released: September 25, 2001 Mac OS X Server 10.1 featured improved performance, increased system stability, and decreased file transfer times compared to Mac OS X Server 10.0. Support was added for RAID 0 and RAID 1 storage configurations, and Mac OS 9.2.1 in NetBoot. Mac OS X Server 10.2 (Jaguar) Released: August 23, 2002 The 10.2 Mac OS X Server release includes updated Open Directory user and file management, which with this release is based on LDAP, beginning the deprecation of the NeXT-originated NetInfo architecture. The new Workgroup Manager interface improved configuration significantly. The release also saw major updates to NetBoot and NetInstall. Many common network services are provided such as NTP, SNMP, web server (Apache), mail server (Postfix and Cyrus), LDAP (OpenLDAP), AFP, and print server. The inclusion of Samba version 3 allows tight integration with Windows clients and servers. MySQL v4.0.16 and PHP v4.3.7 are also included. Mac OS X Server 10.3 (Panther) Released: October 24, 2003 The 10.3 Mac OS X Server release includes updated Open Directory user and file management, which with this release is based on LDAP, beginning the deprecation of the NeXT-originated NetInfo architecture. The new Workgroup Manager interface improved configuration significantly. Many common network services are provided such as NTP, SNMP, web server (Apache), mail server (Postfix and Cyrus), LDAP (OpenLDAP), AFP, and print server. The inclusion of Samba version 3 allows tight integration with Windows clients and servers. MySQL v4.0.16 and PHP v4.3.7 are also included. Mac OS X Server 10.4 (Tiger) Released: April 29, 2005 The 10.4 release adds 64-bit application support, Access Control Lists, Xgrid, link aggregation, e-mail spam filtering (SpamAssassin), virus detection (ClamAV), Gateway Setup Assistant, and servers for Software Update, iChat Server using XMPP, Boot Camp Assistant, Dashboard, and weblogs. On August 10, 2006, Apple announced the first Universal Binary release of Mac OS X Server, version 10.4.7, supporting both PowerPC and Intel processors. At the same time Apple announced the release of the Intel-based Mac Pro and Xserve systems. Mac OS X Server 10.5 (Leopard Server) Released: October 26, 2007. Leopard Server sold for $999 for an unlimited-client license. Mac OS X Server version 10.5.x ‘Leopard’ was the last major version of Mac OS X Server to support PowerPC-based servers and workstations such as the Apple Xserve G5 and Power Mac G5. Features RADIUS Server. Leopard Server includes FreeRADIUS for network authentication. It ships with support for wireless access stations however can be modified into a fully functioning FreeRADIUS server. Ruby on Rails. Mac OS X Server version 10.5 ‘Leopard’ was the first version to ship with Ruby on Rails, the server-side Web application framework used by sites such as GitHub. Mac OS X Server 10.6 (Snow Leopard Server) Released: August 28, 2009 Snow Leopard Server sold for $499 and included unlimited client licenses. New Features: Full 64-bit operating system. On appropriate systems with 4 GB of RAM or more, Snow Leopard Server uses a 64-bit kernel to address up to a theoretical 16 TB of RAM. iCal Server 2 with improved CalDAV support, a new web calendaring application, push notifications and the ability to send email invitations to non-iCal users. Address Book Server provides a central location for users to store and access personal contacts across multiple Macs and synchronized iPhones. Based on the CardDAV protocol standard. Wiki Server 2, with server side Quick Look and the ability to view wiki content on iPhone. A new Mail server engine that supports push email so users receive immediate access to new messages. However, Apple's implementation of push email is not supported for Apple's iPhone. Podcast Producer 2 with dual-source video support. Also includes a new Podcast Composer application to automate the production process, making it simple to create podcasts with a customized, consistent look and feel. Podcast Composer creates a workflow to add titles, transitions and effects, save to a desired format and share to wikis, blogs, iTunes, iTunes U, Final Cut Server or Podcast Library. Mobile Access Server enables iPhone and Mac users to access secured network services, including corporate websites, online business applications, email, calendars and contacts. Without requiring additional software, Mobile Access Server acts as a reverse proxy server and provides SSL encryption and authentication between the user's iPhone or Mac and a private network. Mac OS X 10.7 (Lion Server) Released: July 20, 2011 In releasing the developer preview of Mac OS X Lion in February 2011, Apple indicated that beginning with Lion, Mac OS X Server would be bundled with the operating system and would not be marketed as a separate product. However, a few months later, the company said it would instead sell the server components as a US$49.99 add-on to Lion, distributed through the Mac App Store (as well as Lion itself). The combined cost of an upgrade to Lion and the purchase of the OS X Server add-on, which costs approximately US$50, was nonetheless significantly lower than the retail cost of Snow Leopard Server (US$499). Lion Server came with unlimited client licenses as did Snow Leopard Server. Lion Server includes new versions of iCal Server, Wiki Server, and Mail Server. More significantly, Lion Server can be used for iOS mobile device management. Starting with Apple Mac OS X Server Version 10.7 “Lion,” PostgreSQL replaces MySQL as the database provided with Mac OS X Server, coinciding with Oracle Corporation’s acquisition of Sun Microsystems and Oracle’s subsequent attempts to tighten MySQL’s licensing restrictions and to exert influence on MySQL’s previously open and independent development model. OS X 10.8 (Mountain Lion Server) Released: July 25, 2012. Like Lion, Mountain Lion had no separate server edition. An OS X Server package was available for Mountain Lion from the Mac App Store for US$19.99, which included a server management application called Server, as well as other additional administrative tools to manage client profiles and Xsan. Mountain Lion Server, like Lion Server, was provided with unlimited client licenses, and once purchased could be run on an unlimited number of systems. OS X 10.9 (Mavericks Server) Released: October 22, 2013. There is no separate server edition of Mavericks, just as there was no separate server edition of Mountain Lion. There is a package, available from the Mac App Store for $19.99, that includes a server management app called Server, as well as other additional administrative tools to manage client profiles and Xsan, and once purchased can be run on an unlimited number of machines. Those enrolled in the Mac or iOS developer programs are given a code to download OS X Server for free. OS X 10.10 (Yosemite Server 4.0) Released: October 16, 2014. There is no separate server edition of Yosemite, just as there was no separate server edition of Mavericks. There is a package, available from the Mac App Store for $19.99, that includes a server management app called Server, as well as other additional administrative tools to manage client profiles and Xsan, and once purchased can be run on an unlimited number of machines. Those enrolled in the Mac or iOS developer programs are given a code to download OS X Server for free. OS X 10.11 (Server 5.0) Released: September 16, 2015. Version 5.0.3 of OS X Server operates with either OS X Yosemite 10.10.5 and OS X El Capitan 10.11. OS X 10.11 (Server 5.1) Released: March 21, 2016. OS X Server 5.1 requires 10.11.4 El Capitan, as previous versions of OS X Server won't work on 10.11.4 El Capitan. macOS 10.12 (Server 5.2) Released: September 20, 2016. Version 5.2 of macOS Server operates with either OS X El Capitan 10.11 or macOS Sierra 10.12. macOS 10.12 (Server 5.3) Released: March 17, 2017. Version 5.3 of macOS Server only operates on macOS Sierra (10.12.4) and later. For macOS Server 5.3.1: macOS 10.13 (Server 5.4) Released: September 25, 2017. Version 5.4 of macOS Server only operates on macOS High Sierra (10.13) and later. macOS 10.13.3 (Server 5.5) Released: January 23, 2018. Version 5.5 of macOS Server only operates on macOS High Sierra (10.13.3) and later. macOS 10.13.5 (Server 5.6) Released: April 24, 2018. Version 5.6 of macOS Server only operates on macOS High Sierra (10.13.5) and later. macOS 10.14 (Server 5.7) Released: September 28, 2018. Version 5.7 of macOS Server only operates on macOS Mojave (10.14) and later. With this version Apple stopped bundling open source services such as Calendar Server, Contacts Server, the Mail Server, DNS, DHCP, VPN Server, and Websites with macOS Server. Included services are now limited to Profile Manager, Open Directory and Xsan. macOS 10.14 (Server 5.8) Released: March 25, 2019. Version 5.8 of macOS Server only operates on macOS Mojave (10.14.4) and later. Profile Manager supports new restrictions, payloads, and commands. macOS 10.15 (Server 5.9) Released: October 8, 2019. Version 5.9 of macOS Server only operates on macOS Catalina (10.15) and later. macOS 10.15 (Server 5.10) Released: April 1, 2020. Version 5.10 of macOS Server only operates on macOS Catalina (10.15) and later. macOS 11 (Server 5.11) Released: December 15, 2020. Version 5.11 of macOS Server only operates on macOS Big Sur (11) and later. macOS 11 (Server 5.11.1) Released: May ??, 2021. Version 5.11.1 of macOS Server only operates on macOS Big Sur (11) and later. macOS 12 (Server 5.12) Released: December 8, 2021. Version 5.12 of macOS Server only operates on macOS Monterey (12) and later. Server administrator tools Beginning with the release of OS X 10.8 – Mountain Lion – there is only one Administrative tool – "Server.app". This application is purchased and downloaded via the Mac App Store. This application is updated independently of macOS, also via the Mac App Store. This Server tool is used to configure, maintain and monitor one or more macOS Server installations. One purchase allows it to be installed on any licensed macOS installation. The following information applies only to versions of Mac OS X Server prior to Mountain Lion (10.8) Mac OS X Server comes with a variety of configuration tools that can be installed on non-server Macs as well: Server Admin Server Preferences (application) Server Assistant Server Monitor System Image Utility Workgroup Manager Xgrid Admin System requirements Technical specifications File and print services Mac (AFP, AppleTalk PAP, IPP) Windows (SMB/CIFS: Apple SMBX in Lion Server — previously Samba 2, IPP) Unix-like systems (NFS, LPR/LPD, IPP) Internet (FTP, WebDAV) Directory services and authentication Open Directory (OpenLDAP, Kerberos, SASL) Windows NT Domain Services (removed in Lion Server, previously Samba 2) Backup Domain Controller (BDC) LDAP directory connector Active Directory connector BSD configuration files (/etc) RADIUS Mail services SMTP (Postfix) POP and IMAP (Dovecot) SSL/TLS encryption (OpenSSL) Mailing lists (Mailman) Webmail (RoundCube) Junk mail filtering (SpamAssassin) Virus detection (ClamAV) Calendaring iCal Server (CalDAV, iTIP, iMIP) Web hosting Apache Web server (2.2 and 1.3) SSL/TLS (OpenSSL) WebDAV Perl (5.8.8), PHP (5.2), Ruby (1.8.6), Rails (1.2.3) MySQL 5 (replaced by PostgreSQL in Lion Server) Capistrano, Mongrel Collaboration services Wiki Server (RSS) iChat Server 3 (XMPP) Application servers Apache Tomcat (6) Java SE virtual machine WebObjects deployment (5.4) Apache Axis (SOAP) Media streaming QuickTime Streaming Server 6 (removed in Lion Server) QuickTime Broadcaster 1.5 Client management Managed Preferences NetBoot NetInstall Software Update Server Portable home directories Profile Manager (new in Lion Server) Networking and VPN DNS server (BIND 9) DHCP server NAT server VPN server (L2TP/IPSec, PPTP) Firewall (IPFW2) NTP Distributed computing Xgrid 2 High-availability features Automatic recovery File system journaling IP failover (dropped in OS X 10.7 and later) Software RAID Disk space monitor File systems HFS+ (journaled, case sensitive and case insensitive) FAT NTFS (write support only available on Mac OS X Snow Leopard Server) UFS (read-only) Management features Server Assistant Server Admin Server Preferences Server Status widget Workgroup Manager System Image Utility Secure Shell (SSH2) Server Monitor RAID Utility SNMPv3 (Net-SNMP) References External links Apple – macOS Server Official feedback page Apple Introduces Mac OS X Server – Apple press release Major Mac OS X Server v10.1 Update Now Available – Apple press release Apple Announces Mac OS X Server “Jaguar”, World’s Easiest-to-Manage UNIX-Based Server Software – Apple press release Apple Announces Mac OS X Server “Panther” – Apple press release Apple Announces Mac OS X Server “Tiger” – Apple press release Apple Announces New Mac OS X Server "Leopard" Features – Apple press release Apple Introduces Mac OS X Server Snow Leopard – Apple press release Server Software version histories Mobile device management

Operating System (OS)

Merge (software) Merge is a software system which allows a user to run DOS/Windows 3.1 on SCO UNIX, in an 8086 virtual machine. History Merge was originally developed to run DOS under UNIX System V Release 2 on an AT&T 6300 Plus personal computer. Development of the virtual machine began in late 1984, and AT&T announced the availability of the machine on 9 October 1985, referring to the bundled Merge software as Simultask. (The PC 6300 Plus shipped with MS-DOS in 1985 though, because its Unix System V distribution was not ready until the end March 1986.) Merge was developed by engineers at Locus Computing Corporation, with collaboration from AT&T hardware and software engineers, particularly on aspects of the system that were specific to the 6300 Plus (in contrast to a standard IBM PC/AT). The AT&T 6300 Plus contained an Intel 80286 processor, which did not include the support for 8086 virtual machines (virtual 8086 mode) found in the 80386 and later processors in the x86 family. On the 80286, the DOS program had to run in realmode. The 6300 Plus was designed with special hardware on the bus that would suppress and capture bus cycles from the DOS program if they were directed toward addresses not assigned for direct access by the DOS virtual machine. Various system registers, such as the programmable interrupt controller (PIC), and the video controller, had to be emulated in software for the DOS process, and a watchdog timer was implemented to recover from DOS programs that would clear the interrupt flag and then hang for too long. The hardware used the non-maskable interrupt (NMI) to take control back to the emulation code. Later, Merge was enhanced to make use of the virtual 8086 mode provided by the 80386 processor; that version was offered with Microport SVR3 starting in 1987, and subsequently with SCO Unix. There was also a Merge/286 version that ran on an unmodified PC/AT (without any special I/O trapping hardware); it ran as long as the PC program was reasonably well-behaved, though a malicious or crashing program could take the unprotected UNIX kernel down on those machines. Even so, the notoriously ill-behaved Microsoft Flight Simulator would run on the PC/AT simultaneously with Unix. These later versions were marketed directly by Locus as well as through some OEM and ISV channels. A product-evaluation version with user manual appeared in January 1987, with retail Version 1.0 of Merge/386 shipping in October of that year. In the late 1980s, the main commercial competitor of Merge was VP/IX developed by Interactive Systems Corporation and Phoenix Technologies. AT&T's Simultask 2.0 was based on VP/IX. In 1992, Univel UnixWare 1.0 Personal Edition came with DOS Merge 3.0 and Novell's DR DOS 6.0. Locus eventually joined the Microsoft WISE program which gave them access to Microsoft Windows source code, which allowed later versions of Merge to run Windows shrink wrapped applications without a copy of Windows. On 12 April 1995, Platinum Technology announced an agreement in principle to acquire Locus Computing Corporation for approximately  million, about 1/4 of which was attributed to the Merge technology and product. The acquisition went through, and Platinum went on to develop the SCO Merge 4 version with Windows 95 support, which was released in 1998. The Merge technology was bought by a company called DASCOM in 1999, which was in turn bought by IBM. A company called TreLOS was spun off in 2000 that continued the development of the virtual machine software and created Win4Lin. TreLOS later merged into NeTraverse, Inc. The SCO Group distributes NeTraverse Merge 5.3, which supports their current products SCO OpenServer 5.x and UnixWare 7. See also Popek and Goldberg virtualization requirements (Dr. Popek was one of the founders of Locus) Windows Interface Source Environment (WISE) References External links Virtualization software

Operating System (OS)

Motorola 68000 The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector. The design implements a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus. The address bus is 24 bits and does not use memory segmentation, which made it easier to program for. Internally, it uses a 16-bit data arithmetic logic unit (ALU) and two more 16-bit ALUs used mostly for addresses, and has a 16-bit external data bus. For this reason, Motorola termed it a 16/32-bit processor. As one of the first widely available processors with a 32-bit instruction set, and running at relatively high speeds for the era, the 68k was a popular design through the 1980s. It was widely used in a new generation of personal computers with graphical user interfaces, including the Macintosh, Amiga, Atari ST, and X68000. The 1988 Mega Drive console is also powered by a 68000. The 68k was soon expanded with more family members, implementing full 32-bit ALUs as part of the growing Motorola 68000 series. The original 68k is generally software forward-compatible with the rest of the line despite being limited to a 16-bit wide external bus. After in production, the 68000 architecture is still in use. History Motorola's first widely-produced CPU was the Motorola 6800. Although a capable design, it was eclipsed by more powerful designs, such as the Zilog Z80, and less expensive designs, such as the MOS Technology 6502 (MOS 6502). As the sales prospects of the 6800 dimmed, Motorola began a new design to replace it. This became the Motorola Advanced Computer System on Silicon project, or MACSS, begun in 1976. The MACSS aimed to develop an entirely new architecture without backward compatibility with the 6800. It ultimately does retain a bus protocol compatibility mode for existing 6800 peripheral devices, and a version with an 8-bit data bus was produced. However, the designers mainly focused on the future, or forward compatibility, which gives the 68000 design a head start against later 32-bit instruction set architectures (ISAs). For instance, the CPU registers are 32 bits wide, though few self-contained structures in the processor itself operate on 32 bits at a time. The MACSS team drew heavily on the influence of minicomputer processor design, such as the PDP-11 and VAX systems, which are similarly microcode-based. In the mid 1970s, the 8-bit microprocessor manufacturers raced to introduce the 16-bit generation. National Semiconductor had been first with its IMP-16 and PACE processors in 1973–1975, but these had issues with speed. Intel had worked on their advanced 16/32-bit Intel iAPX 432 (alias 8800) since 1975 and their Intel 8086 since 1976 (it was introduced in 1978 but became widespread in the form of the almost identical 8088 in the IBM PC a few years later). Arriving late to the 16-bit arena affords the new processor more transistors (roughly 40,000 active versus 20,000 active in the 8086), 32-bit macroinstructions, and acclaimed general ease of use. The original MC68000 was fabricated using an HMOS process with a 3.5 µm feature size. Formally introduced in September 1979, initial samples were released in February 1980, with production chips available over the counter in November. Initial speed grades are 4, 6, and 8 MHz. 10 MHz chips became available during 1981, and 12.5 MHz chips by June 1982. The 16.67 MHz "12F" version of the MC68000, the fastest version of the original HMOS chip, was not produced until the late 1980s. IBM considered the 68000 for the IBM PC but chose the Intel 8088 because the 68000 was not ready; Walden C. Rhines wrote that thus "Motorola, with its superior technology, lost the single most important design contest of the last 50 years". (IBM Instruments briefly sold the 68000-based IBM System 9000 laboratory computer systems.) The 68k instruction set is particularly well suited to implement Unix, and the 68000 and its successors became the dominant CPUs for Unix-based workstations including Sun workstations and Apollo/Domain workstations. The 68000 also is used for mass-market computers such as the Apple Lisa, Macintosh, Amiga, and Atari ST. The 68000 is used in Microsoft Xenix systems, as well as an early NetWare Unix-based Server. The 68000 is used in the first generation of desktop laser printers, including the original Apple Inc. LaserWriter and the HP LaserJet. In 1981, Motorola introduced the Motorola 68000 Educational Computer Board, a single-board computer for educational and training purposes which in addition to the 68000 itself contained memory, I/O devices, programmable timer and wire-wrap area for custom circuitry. The board remained in use in US colleges as a tool for learning assembly programming until the early 1990s. In 1982, the 68000 received a minor update to its instruction set architecture (ISA) to support virtual memory and to conform to the Popek and Goldberg virtualization requirements. The updated chip is called the 68010. It also adds a new "loop mode" which speeds up small loops, and increases overall performance by about 10% at the same clock speeds. A further extended version, which exposes 31 bits of the address bus, was also produced in small quantities as the 68012. To support lower-cost systems and control applications with smaller memory sizes, Motorola introduced the 8-bit compatible MC68008, also in 1982. This is a 68000 with an 8-bit data bus and a smaller (20-bit) address bus. After 1982, Motorola devoted more attention to the 68020 and 88000 projects. Second-sourcing Several other companies were second-source manufacturers of the HMOS 68000. These included Hitachi (HD68000), who shrank the feature size to 2.7 µm for their 12.5 MHz version, Mostek (MK68000), Rockwell (R68000), Signetics (SCN68000), Thomson/SGS-Thomson (originally EF68000 and later TS68000), and Toshiba (TMP68000). Toshiba was also a second-source maker of the CMOS 68HC000 (TMP68HC000). Encrypted variants of the 68000, being the Hitachi FD1089 and FD1094, store decryption keys for opcodes and opcode data in battery-backed memory and were used in certain Sega arcade systems including System 16 to prevent piracy and illegal bootleg games. CMOS versions The 68HC000, the first CMOS version of the 68000, was designed by Hitachi and jointly introduced in 1985. Motorola's version is called the MC68HC000, while Hitachi's is the HD68HC000. The 68HC000 offers speeds of 8–20 MHz. Except for using CMOS circuitry, it behaved identically to the HMOS MC68000, but the change to CMOS greatly reduced its power consumption. The original HMOS MC68000 consumed around 1.35 watts at an ambient temperature of 25 °C, regardless of clock speed, while the MC68HC000 consumed only 0.13 watts at 8 MHz and 0.38 watts at 20 MHz. (Unlike CMOS circuits, HMOS still draws power when idle, so power consumption varies little with clock rate.) Apple selected the 68HC000 for use in the Macintosh Portable. Motorola replaced the MC68008 with the MC68HC001 in 1990. This chip resembles the 68HC000 in most respects, but its data bus can operate in either 16-bit or 8-bit mode, depending on the value of an input pin at reset. Thus, like the 68008, it can be used in systems with cheaper 8-bit memories. The later evolution of the 68000 focused on more modern embedded control applications and on-chip peripherals. The 68EC000 chip and SCM68000 core remove the M6800 peripheral bus, and exclude the MOVE from SR instruction from user mode programs, making the 68EC000 and 68SEC000 the only 68000 CPUs not 100% object code compatible with previous 68000 CPUs when run in User Mode. When run in Supervisor Mode, there is no difference. In 1996, Motorola updated the standalone core with fully static circuitry, drawing only 2 µW in low-power mode, calling it the MC68SEC000. Motorola ceased production of the HMOS MC68000 and MC68008 in 1996, but its spin-off company Freescale Semiconductor was still producing the MC68HC000, MC68HC001, MC68EC000, and MC68SEC000, as well as the MC68302 and MC68306 microcontrollers and later versions of the DragonBall family. The 68000's architectural descendants, the 680x0, CPU32, and Coldfire families, were also still in production. More recently, with the Sendai fab closure, all 68HC000, 68020, 68030, and 68882 parts have been discontinued, leaving only the 68SEC000 in production. As a microcontroller core Since being succeeded by "true" 32-bit microprocessors, the 68000 is used as the core of many microcontrollers. In 1989, Motorola introduced the MC68302 communications processor. Applications At its introduction, the 68000 was first used in high-priced systems, including multiuser microcomputers like the WICAT 150, early Alpha Microsystems computers, Sage II / IV, Tandy 6000 / TRS-80 Model 16, and Fortune 32:16; single-user workstations such as Hewlett-Packard's HP 9000 Series 200 systems, the first Apollo/Domain systems, Sun Microsystems' Sun-1, and the Corvus Concept; and graphics terminals like Digital Equipment Corporation's VAXstation 100 and Silicon Graphics' IRIS 1000 and 1200. Unix systems rapidly moved to the more capable later generations of the 68k line, which remained popular in that market throughout the 1980s. By the mid-1980s, falling production cost made the 68000 viable for use in personal and home computers, starting with the Apple Lisa and Macintosh, and followed by the Commodore Amiga, Atari ST, and Sharp X68000. On the other hand, the Sinclair QL microcomputer was the most commercially important utilisation of the 68008, along with its derivatives, such as the ICL One Per Desk business terminal. Helix Systems (in Missouri, United States) designed an extension to the SWTPC SS-50 bus, the SS-64, and produced systems built around the 68008 processor. While the adoption of RISC and x86 displaced the 68000 series as desktop/workstation CPU, the processor found substantial use in embedded applications. By the early 1990s, quantities of 68000 CPUs could be purchased for less than 30 USD per part. Video game manufacturers used the 68000 as the backbone of many arcade games and home game consoles: Atari's Food Fight, from 1982, was one of the first 68000-based arcade games. Others included Sega's System 16, Capcom's CP System and CPS-2, and SNK's Neo Geo. By the late 1980s, the 68000 was inexpensive enough to power home game consoles, such as Sega's Mega Drive/Genesis console and also the Mega CD attachment for it (A Mega CD system has three CPUs, two of them 68000s). The 1993 multi-processor Atari Jaguar console used a 68000 as a support chip, although some developers used it as the primary processor due to familiarity. The 1994 multi-processor Sega Saturn console used the 68000 as a sound co-processor (much as the Mega Drive/Genesis uses the Z80 as a co-processor for sound and/or other purposes). By 1995 the 68000 had made it into a handheld game console, Sega's Genesis Nomad, as its main CPU. Certain arcade games (such as Steel Gunner and others based on Namco System 2) use a dual 68000 CPU configuration, and systems with a triple 68000 CPU configuration also exist (such as Galaxy Force and others based on the Sega Y Board), along with a quad 68000 CPU configuration, which has been used by Jaleco (one 68000 for sound has a lower clock rate compared to the other 68000 CPUs) for games such as Big Run and Cisco Heat; another, fifth 68000 (at a different clock rate than the other 68000 CPUs) was used in the Jaleco arcade game Wild Pilot for input/output (I/O) processing. The 68000 also saw great success as an embedded controller. As early as 1981, laser printers such as the Imagen Imprint-10 were controlled by external boards equipped with the 68000. The first HP LaserJet, introduced in 1984, came with a built-in 8 MHz 68000. Other printer manufacturers adopted the 68000, including Apple with its introduction of the LaserWriter in 1985, the first PostScript laser printer. The 68000 continued to be widely used in printers throughout the rest of the 1980s, persisting well into the 1990s in low-end printers. The 68000 also saw success in the field of industrial control systems. Among the systems benefited from having a 68000 or derivative as their microprocessor were families of programmable logic controllers (PLCs) manufactured by Allen-Bradley, Texas Instruments and subsequently, following the acquisition of that division of TI, by Siemens. Users of such systems do not accept product obsolescence at the same rate as domestic users, and it is entirely likely that despite having been installed over 20 years ago, many 68000-based controllers will continue in reliable service well into the 21st century. In a number of digital oscilloscopes from the 80s, the 68000 has been used as a waveform display processor; some models including the LeCroy 9400/9400A also use the 68000 as a waveform math processor (including addition, subtraction, multiplication, and division of two waveforms/references/waveform memories), and some digital oscilloscopes using the 68000 (including the 9400/9400A) can also perform fast Fourier transform functions on a waveform. The 683XX microcontrollers, based on the 68000 architecture, are used in networking and telecom equipment, television set-top boxes, laboratory and medical instruments, and even handheld calculators. The MC68302 and its derivatives have been used in many telecom products from Cisco, 3com, Ascend, Marconi, Cyclades and others. Past models of the Palm PDAs and the Handspring Visor used the DragonBall, a derivative of the 68000. AlphaSmart used the DragonBall family in later versions of its portable word processors. Texas Instruments used the 68000 in its high-end graphing calculators, the TI-89 and TI-92 series and Voyage 200. A modified version of the 68000 formed the basis of the IBM XT/370 hardware emulator of the System 370 processor. Architecture Address bus The 68000 has a 24-bit external address bus and two byte-select signals "replaced" A0. These 24 lines can therefore address 16 MB of physical memory with byte resolution. Address storage and computation uses 32 bits internally; however, the 8 high-order address bits are ignored due to the physical lack of device pins. This allows it to run software written for a logically flat 32-bit address space, while accessing only a 24-bit physical address space. Motorola's intent with the internal 32-bit address space was forward compatibility, making it feasible to write 68000 software that would take full advantage of later 32-bit implementations of the 68000 instruction set. However, this did not prevent programmers from writing forward incompatible software. "24-bit" software that discarded the upper address byte, or used it for purposes other than addressing, could fail on 32-bit 68000 implementations. For example, early (pre-7.0) versions of Apple's Mac OS used the high byte of memory-block master pointers to hold flags such as locked and purgeable. Later versions of the OS moved the flags to a nearby location, and Apple began shipping computers which had "32-bit clean" ROMs beginning with the release of the 1989 Mac IIci. The 68000 family stores multi-byte integers in memory in big-endian order. Internal registers The CPU has eight 32-bit general-purpose data registers (D0-D7), and eight address registers (A0-A7). The last address register is the stack pointer, and assemblers accept the label SP as equivalent to A7. This was a good number of registers at the time in many ways. It was small enough to allow the 68000 to respond quickly to interrupts (even in the worst case where all 8 data registers D0–D7 and 7 address registers A0–A6 needed to be saved, 15 registers in total), and yet large enough to make most calculations fast, because they could be done entirely within the processor without keeping any partial results in memory. (Note that an exception routine in supervisor mode can also save the user stack pointer A7, which would total 8 address registers. However, the dual stack pointer (A7 and supervisor-mode A7') design of the 68000 makes this normally unnecessary, except when a task switch is performed in a multitasking system.) Having the two types of registers allows one 32-bit address and one 16-bit data calculation to take place at the one time. This results in reduced instruction execution time as addresses and data can be processed in parallel. Status register The 68000 has a 16-bit status register. The upper 8 bits is the system byte, and modification of it is privileged. The lower 8 bits is the user byte, also known as the condition code register (CCR), and modification of it is not privileged. The 68000 comparison, arithmetic, and logic operations modify condition codes to record their results for use by later conditional jumps. The condition code bits are "zero" (Z), "carry" (C), "overflow" (V), "extend" (X), and "negative" (N). The "extend" (X) flag deserves special mention, because it is separate from the carry flag. This permits the extra bit from arithmetic, logic, and shift operations to be separated from the carry for flow-of-control and linkage. Instruction set The designers attempted to make the assembly language orthogonal. That is, instructions are divided into operations and address modes, and almost all address modes are available for almost all instructions. There are 56 instructions and a minimum instruction size of 16 bits. Many instructions and addressing modes are longer to include more address or mode bits. Privilege levels The CPU, and later the whole family, implements two levels of privilege. User mode gives access to everything except privileged instructions such as interrupt level controls. Supervisor privilege gives access to everything. An interrupt always becomes supervisory. The supervisor bit is stored in the status register, and is visible to user programs. An advantage of this system is that the supervisor level has a separate stack pointer. This permits a multitasking system to use very small stacks for tasks, because the designers do not have to allocate the memory required to hold the stack frames of a maximum stack-up of interrupts. Interrupts The CPU recognizes seven interrupt levels. Levels 1 through 5 are strictly prioritized. That is, a higher-numbered interrupt can always interrupt a lower-numbered interrupt. In the status register, a privileged instruction allows setting the current minimum interrupt level, blocking lower or equal priority interrupts. For example, if the interrupt level in the status register is set to 3, higher levels from 4 to 7 can cause an exception. Level 7 is a level triggered non-maskable interrupt (NMI). Level 1 can be interrupted by any higher level. Level 0 means no interrupt. The level is stored in the status register, and is visible to user-level programs. Hardware interrupts are signalled to the CPU using three inputs that encode the highest pending interrupt priority. A separate encoder is usually required to encode the interrupts, though for systems that do not require more than three hardware interrupts it is possible to connect the interrupt signals directly to the encoded inputs at the cost of more software complexity. The interrupt controller can be as simple as a 74LS148 priority encoder, or may be part of a very large-scale integration (VLSI) peripheral chip such as the MC68901 Multi-Function Peripheral (used in the Atari ST range of computers and Sharp X68000), which also provides a UART, timer, and parallel I/O. The "exception table" (interrupt vector table interrupt vector addresses) is fixed at addresses 0 through 1023, permitting 256 32-bit vectors. The first vector (RESET) consists of two vectors, namely the starting stack address, and the starting code address. Vectors 3 through 15 are used to report various errors: bus error, address error, illegal instruction, zero division, CHK and CHK2 vector, privilege violation (to block privilege escalation), and some reserved vectors that became line 1010 emulator, line 1111 emulator, and hardware breakpoint. Vector 24 starts the real interrupts: spurious interrupt (no hardware acknowledgement), and level 1 through level 7 autovectors, then the 16 TRAP vectors, then some more reserved vectors, then the user defined vectors. Since the starting code address vector must always be valid on reset, systems commonly included some nonvolatile memory (e.g. ROM) starting at address zero to contain the vectors and bootstrap code. However, for a general purpose system it is desirable for the operating system to be able to change the vectors at runtime. This was often accomplished by either pointing the vectors in ROM to a jump table in RAM, or through use of bank switching to allow the ROM to be replaced by RAM at runtime. The 68000 does not meet the Popek and Goldberg virtualization requirements for full processor virtualization because it has a single unprivileged instruction, "MOVE from SR", which allows user-mode software read-only access to a small amount of privileged state. The 68EC000 and 68SEC000, which are later derivatives of the 68000, do meet the requirements as the "MOVE from SR" instruction is privileged. The same change was introduced on the 68010 and later CPUs. The 68000 is also unable to easily support virtual memory, which requires the ability to trap and recover from a failed memory access. The 68000 does provide a bus error exception which can be used to trap, but it does not save enough processor state to resume the faulted instruction once the operating system has handled the exception. Several companies did succeed in making 68000-based Unix workstations with virtual memory that worked by using two 68000 chips running in parallel on different phased clocks. When the "leading" 68000 encountered a bad memory access, extra hardware would interrupt the "main" 68000 to prevent it from also encountering the bad memory access. This interrupt routine would handle the virtual memory functions and restart the "leading" 68000 in the correct state to continue properly synchronized operation when the "main" 68000 returned from the interrupt. These problems were fixed in the next major revision of the 68k architecture with the release of the MC68010. The Bus Error and Address Error exceptions push a large amount of internal state onto the supervisor stack in order to facilitate recovery, and the "MOVE from SR" instruction was made privileged. A new unprivileged "MOVE from CCR" instruction is provided for use in its place by user mode software; an operating system can trap and emulate user mode "MOVE from SR" instructions if desired. Instruction set details The standard addressing modes are: Register direct data register, e.g. "D0" address register, e.g. "A0" Register indirect Simple address, e.g. (A0) Address with post-increment, e.g. (A0)+ Address with pre-decrement, e.g. −(A0) Address with a 16-bit signed offset, e.g. 16(A0) Register indirect with index register & 8-bit signed offset e.g. 8(A0,D0) or 8(A0,A1) Note that for (A0)+ and −(A0), the actual increment or decrement value is dependent on the operand size: a byte access adjusts the address register by 1, a word by 2, and a long by 4. PC (program counter) relative with displacement Relative 16-bit signed offset, e.g. 16(PC). This mode was very useful for position-independent code. Relative with 8-bit signed offset with index, e.g. 8(PC,D2) Absolute memory location Either a number, e.g. "$4000", or a symbolic name translated by the assembler Most 68000 assemblers used the "$" symbol for hexadecimal, instead of "0x" or a trailing H. There were 16 and 32-bit versions of this addressing mode Immediate mode Data stored in the instruction, e.g. "#400" Quick immediate mode 3-bit unsigned (or 8-bit signed with moveq) with value stored in opcode In addq and subq, 0 is the equivalent to 8 e.g. moveq #0,d0 was quicker than clr.l d0 (though both made D0 equal to 0) Plus: access to the status register, and, in later models, other special registers. Most instructions have dot-letter suffixes, permitting operations to occur on 8-bit bytes (".b"), 16-bit words (".w"), and 32-bit longs (".l"). Like many CPUs of its era the cycle timing of some instructions varied depending on the source operand(s). For example, the unsigned multiply instruction takes (38+2n) clock cycles to complete where 'n' is equal to the number of bits set in the operand. To create a function that took a fixed cycle count required the addition of extra code after the multiply instruction. This would typically consume extra cycles for each bit that wasn't set in the original multiplication operand. Most instructions are dyadic, that is, the operation has a source, and a destination, and the destination is changed. Notable instructions were: Arithmetic: ADD, SUB, MULU (unsigned multiply), MULS (signed multiply), DIVU, DIVS, NEG (additive negation), and CMP (a sort of comparison done by subtracting the arguments and setting the status bits, but did not store the result) Binary-coded decimal arithmetic: ABCD, NBCD, and SBCD Logic: EOR (exclusive or), AND, NOT (logical not), OR (inclusive or) Shifting: (logical, i.e. right shifts put zero in the most-significant bit) LSL, LSR, (arithmetic shifts, i.e. sign-extend the most-significant bit) ASR, ASL, (rotates through eXtend and not) ROXL, ROXR, ROL, ROR Bit test and manipulation in memory or data register: BSET (set to 1), BCLR (clear to 0), BCHG (invert) and BTST (no change). All of these instructions first test the destination bit and set (clear) the CCR Z bit if the destination bit is 0 (1), respectively. Multiprocessing control: TAS, test-and-set, performed an indivisible bus operation, permitting semaphores to be used to synchronize several processors sharing a single memory Flow of control: JMP (jump), JSR (jump to subroutine), BSR (relative address jump to subroutine), RTS (return from subroutine), RTE (return from exception, i.e. an interrupt), TRAP (trigger a software exception similar to software interrupt), CHK (a conditional software exception) Branch: Bcc (where the "cc" specified one of 14 tests of the condition codes in the status register: equal, greater than, less-than, carry, and most combinations and logical inversions, available from the status register). The remaining two possible conditions (always true and always false) have separate instruction mnemonics, BRA (branch always), and BSR (branch to subroutine). Decrement-and-branch: DBcc (where "cc" was as for the branch instructions), which, provided the condition was false, decremented the low word of a D-register and, if the result was not -1 ($FFFF), branched to a destination. This use of −1 instead of 0 as the terminating value allowed the easy coding of loops that had to do nothing if the count was 0 to start with, with no need for another check before entering the loop. This also facilitated nesting of DBcc. 68EC000 The 68EC000 is a low-cost version of the 68000 with a slightly different pinout, designed for embedded controller applications. The 68EC000 can have either a 8-bit or 16-bit data bus, switchable at reset. The processors are available in a variety of speeds including 8 and 16 MHz configurations, producing 2,100 and 4,376 Dhrystones each. These processors have no floating-point unit, and it is difficult to implement an FPU coprocessor (MC68881/2) with one because the EC series lacks necessary coprocessor instructions. The 68EC000 was used as a controller in many audio applications, including Ensoniq musical instruments and sound cards, where it was part of the MIDI synthesizer. On Ensoniq sound boards, the controller provided several advantages compared to competitors without a CPU on board. The processor allowed the board to be configured to perform various audio tasks, such as MPU-401 MIDI synthesis or MT-32 emulation, without the use of a terminate-and-stay-resident program. This improved software compatibility, lowered CPU usage, and eliminated host system memory usage. The Motorola 68EC000 core was later used in the m68k-based DragonBall processors from Motorola/Freescale. It also was used as a sound controller in the Sega Saturn game console and as a controller for the HP JetDirect Ethernet controller boards for the mid-1990s HP LaserJet printers. Example code The 68000 assembly code below is for a subroutine named , which copies a null-terminated string of 8-bit characters to a destination string, converting all alphabetic characters to lower case. The subroutine establishes a call frame using register A6 as the frame pointer. This kind of calling convention supports reentrant and recursive code and is typically used by languages like C and C++. The subroutine then retrieves the parameters passed to it ( and ) from the stack. It then loops, reading an ASCII character (one byte) from the string, checking whether it is a capital alphabetic character, and if so, converting it into a lower-case character, otherwise leaving it as it is, then writing the character into the string. Finally, it checks whether the character was a null character; if not, it repeats the loop, otherwise it restores the previous stack frame (and A6 register) and returns. Note that the string pointers (registers A0 and A1) are auto-incremented in each iteration of the loop. In contrast, the code below is for a stand-alone function, even on the most restrictive version of AMS for the TI-89 series of calculators, being kernel-independent, with no values looked up in tables, files or libraries when executing, no system calls, no exception processing, minimal registers to be used, nor the need to save any. It is valid for historical Julian dates from 1 March 1 AD, or for Gregorian ones. In less than two dozen operations it calculates a day number compatible with ISO 8601 when called with three inputs stored at their corresponding LOCATIONS: ; ; WDN, an address - for storing result d0 ; FLAG, 0 or 2 - to choose between Julian or Gregorian, respectively ; DATE, year0mda - date stamp as binary word&byte&byte in basic ISO-format ;(YEAR, year ~ YEAR=DATE due to big-endianness) ; ; ; Apply step 1 - Lachman's congruence ; ; Apply step 2 - Finding spqr as the year of the Julian leap day preceding DATE ; ; (Apply step 0 - Gregorian adjustment) ; ; ; ; Days of the week correspond to day numbers of the week as: ; Sun=0 Mon=1 Tue=2 Wed=3 Thu=4 Fri=5 Sat=6 ; See also Motorola 68000 series Motorola 6800 – an 8-bit predecessor DTACK Grounded – an early 68000 newsletter References Further reading Datasheets and manuals M68000 Microprocessor Users Manual (Rev 8); Motorola (Freescale); 224 pages; 1994. M68000 Microprocessors User's Manual (9th Edition); NXP; 189 pages; 1993. Addendum to M68000 User Manual (Rev 0); Motorola (Freescale); 26 pages; 1997. M68000 Family Programmer's Reference Manual; Motorola (Freescale); 646 pages; 1991; . Books 68000, 68010, 68020 Primer; 1st Ed; Stan Kelly-Bootle and Bob Fowler; Howard Sams & Co; 370 pages; 1985; . (archive) Mastering The 68000 Microprocessor; 1st Ed; Phillip Robinson; Tab Books; 244 pages; 1985; . (archive) Pocket Guide Assembly Language for the 68000 Series; 1st Ed; Robert Erskine; Pitman Publishing; 70 pages; 1984; . (archive) Motorola M68000 die schematics 68000 Machine Code Programming (68000, 68008, 68010, & 68020 Processors); 1st Ed; David Barrow; Collins Professional and Technical Books; 234 pages; 1985; . External links comp.sys.m68k FAQ Descriptions of assembler instructions 68000 images and descriptions at cpu-collection.de EASy68K, an open-source 68k assembler for Windows the 68k and m88k resource – with information on Motorola's VME based 68k boards 68k microprocessors Instruction set architectures Computer-related introductions in 1979 32-bit microprocessors

Operating System (OS)

TurboDOS TurboDOS is a multi user CP/M like operating system for the Z80 and 8086 CPUs developed by Software 2000 Inc. It was released around 1982 for S100 bus based systems such as the NorthStar Horizon and the Commercial Systems line of the multiprocessor systems including the CSI-50, CSI-75, SCI-100 and CSI-150. The multiprocessor nature of TurboDOS is its most unusual feature. Unlike other operating systems of its time where networking of processors was either an afterthought, or which only support a file transfer protocol, TurboDOS was designed from the ground up as a multiprocessor operating system. It is modular in construction, with the operating system generation based on a relocating, linking, loader program. This makes the incorporation of different hardware driver modules quite easy, particularly for bus-oriented machines, such as the IEEE-696 (S-100) bus which was commonly used for TurboDOS systems. Architecture TurboDOS is highly modular, consisting of more than forty separate functional modules distributed in relocatable form. These modules are "building blocks" that you can combine in various ways to produce a family of compatible operating systems. This section describes the modules in detail, and describes how to combine them in various configurations. Possible TurboDOS configurations include: single-user without spooling single-user with spooling network server simple network user (no local disks) complex network user (with local disks) Numerous subtle variations are possible in each of these categories. Module hierarchy The architecture of TurboDOS can be viewed as a three-level hierarchy. The highest level of the hierarchy is the process level. TurboDOS can support many concurrent processes at this level. The intermediate level of the hierarchy is the kernel level. The kernel supports the 93 C-functions and T-functions, and controls the sharing of computer resources such as processor time, memory, peripheral devices, and disk files. Processes make requests of the kernel through the entrypoint module OSNTRY, which decodes each C-function and T-function by number and invokes the appropriate kernel module. The C functions include the CP/M BDOS functions and selected MP/M functions. The lowest level of the hierarchy is the driver level, and contains all the device-dependent drivers necessary to interface TurboDOS to the particular hardware being used. Drivers must be provided for all peripherals, including console, printers, disks, communications channels, and network interface. Drivers are also required for the real-time clock (or other periodic interrupt source), and for bank-switched memory (if applicable). TurboDOS is designed to interface with almost any kind of peripheral hardware. It operates most efficiently with interrupt-driven, DMA-type interfaces, but can also work fine using polled and programmed-I/O devices. TurboDOS loader The TurboDOS loader OSLOAD.COM is a program containing an abbreviated version of the kernel and drivers. Its purpose is to load the full TurboDOS operating system from a disk file (OSSERVER.SYS) into memory at each system cold-start. System generation The functional modules are distributed in relocatable format (.REL) and the GEN command is a specialized linker which builds an executable version of the system. Commands TurboDOS has no "resident" commands. All commands are executable files. The standard commands are: External links The TurboDOS Museum TUG Newsletters Z80 Implementors Guide (pdf) The TurboDOS Operating System CP/M Microcomputer software Disk operating systems

Operating System (OS)

Mac OS X Leopard Mac OS X Leopard (version 10.5) is the sixth major release of macOS, Apple's desktop and server operating system for Macintosh computers. Leopard was released on October 26, 2007 as the successor of Mac OS X 10.4 Tiger, and is available in two editions: a desktop version suitable for personal computers, and a server version, Mac OS X Server. It retailed for $129 for the desktop version and $499 for Server. Leopard was superseded by Snow Leopard (version 10.6) in 2009. Leopard is the final version of macOS to support the PowerPC architecture as Snow Leopard functions solely on Intel based Macs. According to Apple, Leopard contains over 300 changes and enhancements compared to its predecessor, Mac OS X Tiger, covering core operating system components as well as included applications and developer tools. Leopard introduces a significantly revised desktop, with a redesigned Dock, Stacks, a semitransparent menu bar, and an updated Finder that incorporates the Cover Flow visual navigation interface first seen in iTunes. Other notable features include support for writing 64-bit graphical user interface applications, an automated backup utility called Time Machine, support for Spotlight searches across multiple machines, and the inclusion of Front Row and Photo Booth, which were previously included with only some Mac models. Apple missed Leopard's release time frame as originally announced by Apple's CEO Steve Jobs. When first discussed in June 2005, Jobs had stated that Apple intended to release Leopard at the end of 2006 or early 2007. A year later, this was amended to Spring 2007; however, on April 12, 2007, Apple issued a statement that its release would be delayed until October 2007 because of the development of the iPhone. New and changed features End-user features Apple advertised that Mac OS X Leopard has 300+ new features, including: A new and improved Automator, with easy starting points to easily start a workflow. It also can quickly create or edit workflows with new interface improvements. Now it can use a new action called "Watch Me Do" that lets you record a user action (like pressing a button or controlling an application without built-in Automator support) and replay as an action in a workflow. It can create more useful Automator workflows with actions for RSS feeds, iSight camera video snapshots, PDF manipulation, and much more. Back to My Mac, a feature for MobileMe users that allows users to access files on their home computer while away from home via the internet. Boot Camp, a software assistant allowing for the installation of other operating systems, such as Windows XP (SP2 or later) or Windows Vista, on a separate partition (or separate internal drive) on Intel-based Macs. Dashboard enhancements, including Web Clip, a feature that allows users to turn a part of any Web page displayed in Safari into a live Dashboard widget, and Dashcode to help developers code widgets. New Desktop, comprises a redesigned 3-D dock with a new grouping feature called Stacks, which displays files in either a "fan" style, "grid" style, or (since 10.5.2) a "list" style. Rory Prior, on the ThinkMac blog, criticized the shelf-like Dock along with a number of other changes to the user interface. Dictionary can now search Wikipedia, and a dictionary of Apple terminology as well. Also included is the Japanese-language dictionary Daijisen, Progressive E-J and Progressive J-E dictionaries, and the 25,000-word thesaurus , all of which are provided by the Japanese publisher Shogakukan. A redesigned Finder, with features similar to those seen in iTunes 7, including Cover Flow and a Source list-like sidebar. Front Row has been reworked to closely resemble the interface of the original Apple TV. iCal calendar sharing and group scheduling as well as syncing event invitations from Mail. The icon also reflects the current date even when the application is not running. In previous versions of Mac OS X, the icon would show July 17 in the icon any time the application was not running but the current date when the application was running. iChat enhancements, including multiple logins, invisibility, animated icons, and tabbed chats, similar to features present in Pidgin, Adium and the iChat plugin Chax; iChat Theater, allowing users to incorporate images from iPhoto, presentations from Keynote, videos from QuickTime, and other Quick Look features into video chats; and Backdrops, which are similar to chroma keys, but use a real-time difference matte technique which does not require a green or blue screen. iChat also implements screen sharing, a feature previously available with Apple Remote Desktop. Mail enhancements including the additions of RSS feeds, Stationery, Notes, and to-dos. To-dos use a system-wide service that is available to all applications. Network file sharing improvements include more granular control over permissions, consolidation of AFP, FTP and SMB sharing into one control panel, and the ability to share individual folders, a feature that had not been available since Mac OS 9. Parental controls now include the ability to place restrictions on use of the Internet and to set parental controls from anywhere using remote setup. Photo Booth enhancements, including video recording with real-time filters and blue/green-screen technology. Podcast Capture, an application allowing users to record and distribute podcasts. It requires access to a computer running Mac OS X Server with Podcast Producer. Preview adds support for annotation, graphics, extraction, search, markup, Instant Alpha and size adjustment tools. Quick Look, a framework allowing documents to be viewed without opening them in an external application and can preview it in full screen. Plug-ins are available for Quick Look so that you can also view other files, such as Installer Packages. Safari 3, which includes Web Clip. Spaces, an implementation of virtual desktops (individually called "Spaces"), allows multiple desktops per user, with certain applications and windows in each desktop. Users can organize certain Spaces for certain applications (e.g., one for work-related tasks and one for entertainment) and switch between them. Exposé works inside Spaces, allowing the user to see at a glance all desktops on one screen.) Users can create and control up to 16 spaces, and applications can be switched between each one, creating a very large workspace. The auto-switching feature in Spaces has annoyed some of its users. Apple added a new preference in 10.5.2 which disabled this feature, but there were still bugs found while switching windows. In 10.5.3, this problem was addressed and was no longer an issue. Spotlight incorporates additional search capabilities such as Boolean operators, as well as the ability to search other computers (with appropriate permissions). Time Machine, an automated backup utility which allows the user to restore files that have been deleted or replaced by another version of a file. Though generally lauded in the press as a step forward for data recovery, Time Machine has been criticized in multiple publications for lacking the capabilities of third-party backup software. Analyzing the feature for TidBITS, Joe Kissell pointed out that Time Machine does not create bootable copies of backed-up volumes, does not back up to AirPort Disk hard drives and will not back up FileVault encrypted home directories until the user logs out, concluding that the feature is "pretty good at what it does" but he will only use it as part of a "broader backup strategy". One of these issues has been resolved, however; On March 19, 2008, updates were released for AirPort and Time Machine, allowing for Time Machine to use a USB hard disk which has been connected to an AirPort Extreme Base Station. Universal Access enhancements: significant improvements to applications including VoiceOver, along with increased support for Braille, closed captioning and a new high‐quality Speech synthesis voice. Many changes to the user interface, such as a transparent menu bar, new icons, and a 3D Dock. As well as this, the Apple icon is now black instead of blue. R.L. Prior, on the ThinkMac blog, criticized a number of changes to Leopard's user interface, including the transparent menu bar and the new folder icons. Decreased transparency of the menu bar, along with the ability to disable the menu bar transparency were added with the 10.5.2 release on February 11, 2008. Russian language support, bringing the total to 18 languages. Leopard removes support for Classic applications. Introduced the Alex voice to VoiceOver. Developer technologies Native support by many libraries and frameworks for 64-bit applications, allowing 64-bit Cocoa applications. Existing 32-bit applications using those libraries and frameworks should continue to run without the need for emulation or translation. Leopard offers the Objective-C 2.0 runtime, which includes new features such as garbage collection. Xcode 3.0 supports the updated language and was itself rewritten with it. A new framework, Core Animation, allows a developer to create complex animations while specifying only a "start" and a "goal" space. The main goal of Core Animation is to enable the creation of complex animations with small amounts of program code. Apple integrates DTrace from the OpenSolaris project and adds a graphical interface called Instruments (previously Xray). DTrace provides tools that users, administrators and developers can use to tune the performance of the operating system and the applications that run on it. The new Scripting Bridge allows programmers to use Python 2.5 and Ruby 1.8.6 to interface with the Cocoa frameworks. Ruby on Rails is included in the default install. Leopard’s OpenGL stack has been updated to version 2.1, and uses LLVM to increase its vertex processing speed. Apple has been working to get LLVM integrated into GCC; LLVM’s use within other operating system facilities has not been announced. The Graphics and Media State of the Union address confirmed many other features are possible because of Core Animation, such as live desktops, improvements to Quartz Composer with custom patches, a new PDF Kit for developers, and improvements to QuickTime APIs. The FSEvents framework allows applications to register for notifications of changes to a given directory tree. Leopard includes a read-only implementation of the ZFS file system. In mid-December 2006, a pre-release version of Leopard appeared to include support for Sun’s ZFS. Jonathan Schwartz, CEO and President of Sun Microsystems, boasted on June 6, 2007, that ZFS had become "the file system" for Leopard. However, the senior project marketing director for Mac OS X stated on June 11, 2007, that the existing HFS+, not ZFS, would be used in Leopard. Apple later clarified that a read-only version of ZFS would be included. Leopard includes drivers for UDF 2.5, necessary for reading HD DVD and Blu-ray discs using third-party drives, but the included DVD Player software can only play HD DVDs authored by DVD Studio Pro. Leopard includes a framework implementing latent semantic mapping for classifying (e.g. textual) data. Leopard is the first operating system with open source BSD code to be certified as fully UNIX-compliant. Certification means that software following the Single UNIX Specification can be compiled and run on Leopard without the need for any code modification. The certification only applies to Leopard when run on Intel processors. Leopard includes J2SE 5.0. Security enhancements New security features intend to provide better internal resiliency to successful attacks, in addition to preventing attacks from being successful in the first place. Library Randomization Leopard implements library randomization, which randomizes the locations of some libraries in memory. Vulnerabilities that corrupt program memory often rely on known addresses for these library routines, which allow injected code to launch processes or change files. Library randomization is presumably a stepping-stone to a more complete implementation of address space layout randomization at a later date. Application Layer Firewall Leopard ships with two firewall engines: the original BSD IPFW, which was present in earlier releases of Mac OS X, and the new Leopard Application Layer Firewall. Unlike IPFW, which intercepts and filters IP datagrams before the kernel performs significant processing, the Application Layer Firewall operates at the socket layer, bound to individual processes. The Application Layer Firewall can therefore make filtering decisions on a per-application basis. Of the two firewall engines, only the Application Layer Firewall is fully exposed in the Leopard user interface. The new firewall offers less control over individual packet decisions (users can decide to allow or deny connections system-wide or to individual applications, but must use IPFW to set fine-grained TCP/IP header-level policies). It also makes several policy exceptions for system processes: neither mDNSResponder nor programs running with superuser privileges are filtered. Sandboxes Leopard includes kernel-level support for role-based access control (RBAC). RBAC is intended to prevent, for example, an application like Mail from editing the password database. Application Signing Leopard provides a framework to use public key signatures for code signing to verify, in some circumstances, that code has not been tampered with. Signatures can also be used to ensure that one program replacing another is truly an "update", and carry any special security privileges across to the new version. This reduces the number of user security prompts, and the likelihood of the user being trained to simply clicking "OK" to everything. Secure Guest Account Guests can be given access to a Leopard system with an account that the system erases and resets at logout. Security features in Leopard have been criticized as weak or ineffective, with the publisher Heise Security documenting that the Leopard installer downgraded firewall protection and exposed services to attack even when the firewall was re-enabled. Several researchers noted that the Library Randomization feature added to Leopard was ineffective compared to mature implementations on other platforms, and that the new "secure Guest account" could be abused by Guests to retain access to the system even after the Leopard log out process erased their home directory. System requirements Apple states the following basic Leopard system requirements, although, for some specific applications and features (such as iChat backdrops) an Intel processor is required: Processor: any Intel processor, or PowerPC G5 or G4 (867 MHz and faster) processor Optical drive: internal or external DVD drive (for installation of the operating system) Memory: minimum 512 MB of RAM (additional RAM (1 GB) is recommended for development purposes) Hard drive capacity: Minimum 9 GB of disk space available. Leopard’s retail version was not released in separate versions for each type of processor, but instead consisted of one universal release that could run on both PowerPC and Intel processors. However, the install discs that ship with Intel-based Macs only contain Intel binaries. Processor type and speed are checked during installation and installation halted if insufficient; however, Leopard will run on slower G4 processor machines (e.g., a 733 MHz Quicksilver) if the installation is performed on a supported Mac and its hard drive then moved to a slower/unsupported one (the drive may either be an internal mechanism or a Firewire external). Supported machines Leopard can run on the later flat-panel iMac G4s, the iMac G5, iMac Intel Core Duo and iMac Intel Core 2 Duo, PowerBook G4, Power Mac G4, Power Mac G5, iBook G4, MacBook, MacBook Pro, MacBook Air, Mac Pro, Mac Mini, Xserve, Xserve G5, Xserve RAID, Macintosh Server G4, and later eMac models. Leopard can run on older hardware as long as they have a G4 upgrade installed running at the 867 MHz or faster, have at least 9 GB free of hard drive space, 512 MB RAM and have a DVD drive. Leopard however will not run on the 900 MHz iBook G3 models even though they exceed the minimum 867 MHz requirement. This is due to the lack of AltiVec support in the G3 line of processors. Leopard can be "hacked" (see below) to install on these G3 and pre-867 MHz G4 machines but the system may behave erratically and many of the programs, features, and functions may not work properly or at all. As of mid-2010, some Apple computers have firmware factory installed which will no longer allow installation of Mac OS X Leopard. These computers only allow installation of Mac OS X Snow Leopard. However, some computers (such as the 2011 model of the Mac mini) can have Leopard installed on them without hacking. Usage on unsupported hardware Some ways of running Leopard on certain unsupported hardware, primarily PowerPC G4 computers with CPU speeds lower than the official requirement of 867 MHz, have been discovered. A common way is use of the program LeopardAssist, which is a bootloader similar in some respects to XPostFacto (used for installing earlier releases of Mac OS X on unsupported G3 and pre-G3 Macs) that uses the Mac’s Open Firmware to tell Leopard that the machine does have a CPU meeting the 867 MHz minimum requirement that the Installer checks for before installation is allowed to commence, when in reality the CPU is slower. Currently, LeopardAssist only runs on slower G4s and many people have installed Leopard successfully on these older machines. Users who have access to supported hardware have installed Leopard on the supported machine then simply moved the hard drive to the unsupported machine. Alternatively, the Leopard Installation DVD was booted on a supported Mac, then installed on an unsupported Mac via Firewire Target Disk Mode. Leopard is only compiled for AltiVec-enabled PowerPC processors (G4 and G5) though, as well as Intel, so both of these methods will only work on Macs with G4 or later CPUs. While some of the earlier beta releases were made to run on some later G3 machines (mostly later 800–900 MHz iBooks), no success with the retail version has been officially reported on G3 Macs except for some later iMacs and "Pismo" PowerBook G3s with G4 processor upgrades installed. For a number of months after Leopard's release it appeared that the only G3 Macs on which Leopard could be run were those with both an aftermarket G4 processor and an AGP graphics card, as failures with the OS partially booting before crashing were reported on older Macs such as the original tray-loading iMacs and the Beige and Blue & White Power Mac G3 (all with G4 upgrades as Leopard will not even begin to load without one) whereas it would boot fine on newer Macs where the Installer restriction had been circumvented. However, more recently it has been reported that with some more work and use of kernel extensions from XPostFacto, Tiger and beta builds of Leopard, the OS can be made to run on G4-upgraded Macs as old as the Power Macintosh 9500, despite the lack of AGP-based graphics. While Leopard can be run on any Mac with a G4 or later processor, some functionality such as Front Row or Time Machine fails to work without a Quartz Extreme-capable graphics card, which many of the earlier G4s did not include in their factory specification. Since Apple moved to using Intel processors in their computers, the OSx86 community has developed and now also allows Mac OS X Tiger and later releases to be installed and run successfully on non-Apple x86-based computers, albeit in violation of Apple's licensing agreement for Mac OS X. Packaging The retail packaging for Leopard is significantly smaller than that of previous versions of Mac OS X (although later copies of Tiger also came in the new smaller box). It also includes a lenticular cover, making the X appear to float above a purple galaxy, somewhat resembling the default Leopard desktop wallpaper. Release history Compatibility After Leopard’s release, there were widely reported incidents of new Leopard installs hanging during boot on the blue screen that appears just before the login process starts. Apple attributed these problems to an outdated version of an unsupported add-on extension called Application Enhancer (APE), from Unsanity which had been incompatible with Leopard. Some users were unaware that APE had been silently installed during installation of Logitech mouse drivers. However, only the users who did not have the latest version of APE installed (2.0.3 at that time) were affected. Apple published a knowledge base article on how to solve this problem. Google announced that the Chrome browser will be dropping support for Leopard starting with Chrome 21. By that time Chrome will no longer auto-update, and new Chrome installations are not allowed. Their rationale for removal of support is that Leopard is an "OS X version also no longer being updated by Apple." Firefox also dropped support for Leopard after it shipped Firefox 16 in October 2012. TenFourFox is a port of Firefox for the PPC architecture, released after Firefox dropped support for Leopard. References External links 2006 WWDC keynote presentation at Apple.com 2007 WWDC keynote presentation at Apple.com Mac OS X Leopard review at Ars Technica 5 IA-32 operating systems X86-64 operating systems PowerPC operating systems 2007 software Computer-related introductions in 2007

Operating System (OS)

Mobile User Objective System The Mobile User Objective System (MUOS) is an United States narrowband military communications satellite system that supports a worldwide, multi-service population of users in the ultra high frequency (UHF) band. The system provides increased communications capabilities to newer, smaller terminals while still supporting interoperability with legacy terminals. MUOS is designed to support users who require greater mobility, higher bit rates and improved operational availability. The MUOS was declared fully operational for use in 2019. Overview The Mobile User Objective System (MUOS), through a constellation of five satellites (four operational satellites and one on-orbit spare), provides global narrowband connectivity to terminals, platforms, tactical operators and operations centers. The system replaces the slower and less mobile 1990s-era Ultra High Frequency Follow-On (UFO) satellite communication system. MUOS primarily serves the United States Department of Defense (DoD) and international allies use is under consideration. Primarily for mobile users (e.g. aerial and maritime platforms, ground vehicles, and dismounted soldiers), MUOS extend users' voice, data, and video communications beyond their lines-of-sight at data rates up to 384 kbit/s. The U.S. Navy's Communications Satellite Program Office (PMW 146) of the Program Executive Office (PEO) for Space Systems in San Diego, is lead developer for the MUOS program. Lockheed Martin Space is the prime system contractor and satellite designer for MUOS under U.S. Navy Contract N00039-04-C-2009, which was announced on 24 September 2004. Key subcontractors include General Dynamics Mission Systems (Ground Transport architecture), Boeing (Legacy UFO and portions of the WCDMA payload) and Harris (deployable mesh reflectors). The program delivered five satellites, four ground stations, and a terrestrial transport network at a cost of US$7.34 billion. Each satellite in the MUOS constellation carries two payloads: a legacy communications payload to maintain Department of Defense narrowband communications during the transition to MUOS, and the advanced MUOS Wideband Code Division Multiple Access (WCDMA) capability, according to NAVWAR. WCDMA system MUOS WCDMA radios can transmit simultaneous voice, video and mission data on an Internet Protocol-based system connected to military networks. MUOS radios operate from anywhere around the world at speeds comparable 3G smartphones. MUOS radios can also work under dense cover, such as jungle canopies and urban settings. The MUOS operates as a global cellular service provider to support the warfighter with modern cell phone-like capabilities, such as multimedia. It converts a commercial third generation (3G) Wideband Code Division Multiple Access (WCDMA) cellular phone system to a military UHF SATCOM radio system using geosynchronous satellites in place of cell towers. By operating in the Ultra high frequency (UHF) frequency band, a lower frequency band than that used by conventional terrestrial cellular networks, the MUOS provides warfighters with the tactical ability to communicate in "disadvantaged" environments, such as heavily forested regions where higher frequency signals would be unacceptably attenuated by the forest canopy. Connections may be set up on demand by users in the field, within seconds, and then released just as easily, freeing resources for other users. In alignment with more traditional military communications methods, pre-planned networks can also be established either permanently or per specific schedule using the MUOS' ground-based Network Management Center. Legacy payload In addition to the cellular MUOS WCDMA payload, a fully capable and separate UFO legacy payload is incorporated into each satellite. The "legacy" payload extends the useful life of legacy UHF SATCOM terminals and enables a smoother transition to MUOS. Launches MUOS-1, after several weather delays, was launched into space successfully on 24 February 2012, at 22:15:00 UTC, carried by an Atlas V launch vehicle flying in its 551 configuration. MUOS-2 was launched on schedule on 19 July 2013, at 13:00:00 UTC aboard an Atlas V 551 (AV-040). MUOS-3 was launched on board an United Launch Alliance (ULA) Atlas V launch vehicle on 20 January 2015, from Cape Canaveral Air Force Station (CCAFS), Florida. MUOS-4 arrived at Cape Canaveral on 31 July 2015. Weather conditions pushed back the launch, which was originally scheduled for on 31 August 2015, at 10:07 UTC. The launch took place on 2 September 2015, at 10:18:00 UTC. MUOS-5 arrived at Cape Canaveral on 9 March 2016. Launch was originally scheduled for on 5 May 2016, but due to an internal investigation into an Atlas V fuel system problem during the Cygnus OA-6 launch on 22 March 2016, the scheduled date was pushed back. The launch took place on 24 June 2016, at 14:30:00 UTC. An "anomaly" aboard the satellite occurred a few days later, however, when it was still in a Geostationary Transfer Orbit (GTO), leaving it "Reconfigured into Safe Intermediate Orbit", or stranded in GTO. Amateur observers tracked it in an orbit of approximately since 3 July 2016. On 3 November 2016, the Navy announced that the satellite has finally reached operational orbit. MUOS operational positions The four currently operational MUOS satellites are stationed at longitude 100° West (MUOS-1); 177° West (MUOS-2); 15° West (MUOS-3); and 75° East (MUOS-4). MUOS-5 is at 103.8° West spare. They have a 5° orbital inclination. In the first few months after launch, the satellites were temporarily parked in a check-out position at longitude 172° West. MUOS ground stations The MUOS includes four ground station facilities. Site selections were completed in 2007 with the signing of a Memorandum of Agreement (MOA) between the U.S. Navy and the Australian Department of Defence. The four ground stations, each of which serves one of the four active satellites of the MUOS constellation will be located at: the Australian Defence Satellite Communications Station at Kojarena, Western Australia about 30 km east of Geraldton, Western Australia; Naval Radio Transmitter Facility (NRTF) Niscemi about 60 km from Naval Air Station Sigonella, Sicily, Italy; Naval SATCOM Facility, Northwest Chesapeake, Southeast Virginia at ; and the Naval Computer and Telecommunications Area Master Station Pacific, Hawaii. Controversy Construction of the ground station in Italy was halted for nearly half of 2012 by protesters concerned with health risks and environmental damage by radio waves. One scientific study "point[s] to serious risks to people and the environment, such as to prevent its realization in densely populated areas, like the one adjacent to the town of Niscemi". In spite of the controversy, the site at Niscemi was completed in anticipation of the launch of MUOS-4. Radio terminals The MUOS waveform with complete red/black operational capability was released in 2012. Until the Joint Tactical Radio System (JTRS) program cancellation in 2011, the JTRS program would provide the DoD terminals that can communicate with the MUOS WCDMA waveform with a series of form-factor models. The JTRS Handheld, Manpack and Small Form Fit (HMS) AN/PRC-155 manpack built by General Dynamics Mission Systems survived the wider JTRS program cancellation and has shipped several low rate of initial production (LRIP) units. Rockwell Collins AN/ARC-210 airborne terminal and Harris Corporation AN/PRC-117G. Manpack have also been certified for operation on the MUOS system. Arctic and Antarctic capabilities Lockheed Martin and an industry team of radio vendors demonstrated extensive Arctic communications reach near the North Pole, believed to be the most northerly successful call to a geosynchronous satellite. WCDMA calls to the far north will be increasingly important where there has been an increase in shipping, resource exploration and tourism without much improvement in secure satellite communications access. Based on these and continued tests, full coverage of the Northwest Passage and Northeast Passage shipping lanes is expected. Several follow-on tests with high quality voice and data including streaming video have occurred in both the Arctic and Antarctic, including a 2015 demonstration from McMurdo Station. See also Global Information Grid Network-centric warfare References External links MUOS 1, 2, 3, 4, 5 MUOS-1 Mission page & launch images, 02/24/2012 MUOS-2 Mission page & launch images, 07/19/2013 MUOS-3 Mission page & launch images, 01/20/2015 MUOS-4 Mission page & launch images, 08/31/2015 MUOS-5 Mission page & launch images, 06/24/2016 G Military space program of the United States Lockheed Martin General Dynamics Mission Systems United States Navy MUOS

Operating System (OS)

TempleOS TempleOS (formerly J Operating System, LoseThos, and SparrowOS) is a biblical-themed lightweight operating system (OS) designed to be the Third Temple prophesied in the Bible. It was created by American programmer Terry A. Davis, who developed it alone over the course of a decade after a series of manic episodes that he later described as a revelation from God. The system was characterized as a modern x86-64 Commodore 64, using an interface similar to a mixture of DOS and Turbo C. Davis proclaimed that the system's features, such as its 640x480 resolution, 16-color display, and single-voice audio, were designed according to explicit instructions from God. It was programmed with an original variation of C (named HolyC) in place of BASIC, and included an original flight simulator, compiler and kernel. TempleOS was released as J Operating System in 2005 and as TempleOS in 2013, and was last updated in 2017. Background Terry A. Davis (1969–2018) began experiencing regular manic episodes in 1996, leading him to numerous stays at mental hospitals. Initially diagnosed with bipolar disorder, he was later declared schizophrenic and remained unemployed for the rest of his life. He suffered from delusions of space aliens and government agents that left him briefly hospitalized for his mental health issues. After experiencing a self-described "revelation", he proclaimed that he was in direct communication with God, and that God told him the operating system was for God's third temple. Davis began developing TempleOS circa 2003. One of its early names was the "J Operating System" before renaming it to "LoseThos", a reference to a scene from the 1986 film Platoon. In 2008, Davis wrote that LoseThos was "primarily for making video games. It has no networking or Internet support. As far as I'm concerned, that would be reinventing the wheel". Another name he used was "SparrowOS" before settling on "TempleOS". In mid-2013, his website announced: "God's temple is finished. Now, God kills CIA until it spreads ." Davis died after being hit by a train on August 11, 2018. System overview TempleOS is a 64-bit, non-preemptive multi-tasking, multi-cored, public domain, open source, ring-0-only, single address space, non-networked, PC operating system for recreational programming. The OS runs 8-bit ASCII with graphics in source code and has a 2D and 3D graphics library, which run at 640x480 VGA with 16 colors. Like most modern operating systems, it has keyboard and mouse support. It supports ISO 9660, FAT32 and RedSea file systems (the latter created by Davis) with support for file compression. According to Davis, many of these specifications—such as the 640x480 resolution, 16-color display and single audio voice—were instructed to him by God. He explained that the limited resolution was to make it easier for children to draw illustrations for God. The operating system includes an original flight simulator, compiler, and kernel. One bundled program, "After Egypt", is a game in which the player travels to a burning bush to use a "high-speed stopwatch". The stopwatch is meant to act as an oracle that generates pseudo-random text, something Davis likened to a Ouija board and glossolalia. An example of generated text follows: TempleOS was written in a programming language developed by Davis as a middle ground between C and C++, originally called "C+" (C Plus), later renamed to "HolyC". It doubles as the shell language, enabling the writing and execution of entire applications from within the shell. The IDE that comes with TempleOS supports several features, such as embedding images in code. It uses a non-standard text format (known as DolDoc) which has support for hypertext links, images, and 3D meshes to be embedded into what are otherwise standard ASCII files; for example, a file can have a spinning 3D model of a tank as a comment in source code. Most code in the OS is JIT-compiled, and it is generally encouraged to use JIT compilation as opposed to creating binaries. Davis ultimately wrote over 100,000 lines of code for the OS. Critical reception TempleOS received mostly "sympathetic" reviews. Tech journalist David Cassel opined that "programming websites tried to find the necessary patience and understanding to accommodate Davis". TechRepublic and OSNews published positive articles on Davis's work, even though Davis was banned from the latter for hostile comments targeting its readers and staff. In his review for TechRepublic, James Sanders concluded that "TempleOS is a testament to the dedication and passion of one man displaying his technological prowess. It doesn't need to be anything more." OSNews editor Kroc Camen wrote that the OS "shows that computing can still be a hobby; why is everybody so serious these days? If I want to code an OS that uses interpretive dance as the input method, I should be allowed to do so, companies like Apple be damned." In 2017, the OS was shown as a part of an outsider art exhibition in Bourogne, France. Legacy After Davis's death, OSNews editor Thom Holwerda wrote: "Davis was clearly a gifted programmer – writing an entire operating system is no small feat – and it was sad to see him affected by his mental illness". One fan described Davis as a "programming legend", while another, a computer engineer, compared the development of TempleOS to a one-man-built skyscraper. He added that it "actually boggles my mind that one man wrote all that" and that it was "hard for a layperson to understand what a phenomenal achievement" it is to write an entire operating system alone. TempleOS is in the public domain. Davis's family has wished for fans to donate to the National Alliance for Mental Illness and other organizations "working to ease the pain and suffering caused by mental illness". See also Creativity and mental health Biblical software Religion and video games SerenityOS References External links TempleOS Website Comprehensive archive of TempleOS and Terry A. Davis material Archive of the TempleOS website and operating system Archive of the TempleOS bootable ISO images TempleOS source code 2013 software Outsider art Free software operating systems Hobbyist operating systems Public-domain software with source code x86-64 operating systems Christian software

Operating System (OS)

HAL (software) HAL (Hardware Abstraction Layer or rather Hardware Annotation Library) is a software subsystem for UNIX-like operating systems providing hardware abstraction. HAL is now deprecated on most Linux distributions and on FreeBSD. Functionality is being merged into udev on Linux as of 2008–2010 and devd on FreeBSD. Previously, HAL was built on top of udev. Some other OS-es which don't have an alternative like udev or devd still use HAL. The purpose of the hardware abstraction layer was to allow desktop applications to discover and use the hardware of the host system through a simple, portable and abstract API, regardless of the type of the underlying hardware. HAL for Linux OS was originally envisioned by Havoc Pennington. It became a freedesktop.org project, and was a key part of the software stack of the GNOME and KDE desktop environments. It is free software, dual-licensed under both the GNU General Public License and the Academic Free License. HAL is unrelated to the concept of Windows NT kernel HALs, which handle some platform-specific core functionality within the kernel, such as interrupt routing. Rationale Traditionally, the operating system kernel was responsible for providing an abstract interface to the hardware the system ran on. Applications used the system call interface, or performed file I/O on device nodes in order to communicate with hardware through these abstractions. This sufficed for the simple hardware of early desktop computing. Computer hardware, however, has increased in complexity and the abstractions provided by Unix kernels have not kept pace with the proliferating number of device and peripheral types now common on both server and desktop computers. Most modern buses have also become hotplug-capable and can have non-trivial topologies. As a result, devices are discovered or change state in ways which can be difficult to track through the system call interface or Unix IPC. The complexity of doing so forces application authors to re-implement hardware support logic. Some devices also require privileged helper programs to prepare them for use. These must often be invoked in ways that can be awkward to express with the Unix permissions model (for example, allowing users to join wireless networks only if they are logged into the video console). Application authors resort to using setuid binaries or run service daemons to provide their own access control and privilege separation, potentially introducing security holes each time. Design HAL is a single daemon responsible for discovering, enumerating and mediating access to most of the hardware on the host computer. Applications communicate with HAL through the D-Bus IPC mechanism, which abstracts the hardware behind an object-based RPC mechanism. Each logical hardware device is represented as a D-Bus object, and its bus address is used as a unique identifier. Devices include abstractions like disk partitions and visible wireless networks. The device's functionality is exposed through D-Bus interfaces, and its state accessed through properties, a set of key-value pairs. HAL broadcasts hardware events as signals on these objects; applications can listen for signals and react to the hardware events that they signify — events such as a digital camera being plugged in, an optical disc spinning up or a laptop computer closing its lid. Implementations and obsolescence On Linux, HAL uses /sys (a virtual file system for Linux systems) to discover hardware and listen for kernel hotplug events. Some Linux distributions also provide a udev rule to allow the udev daemon to notify HAL whenever new device nodes appear. Deprecated , Linux distributions such as Ubuntu, Debian, and Fedora and on FreeBSD, and projects such as KDE, GNOME and X.org are in the process of deprecating HAL as it has "become a large monolithic unmaintainable mess". The process is largely complete, but some use of HAL remains – Debian squeeze (Feb 2011) and Ubuntu version 10.04 remove HAL from the basic system and boot process. In Linux, it is in the process of being merged into udev (main udev, libudev, and udev-extras) and existing udev and kernel functionality. The replacement for non-Linux systems such as FreeBSD is devd. Initially a new daemon DeviceKit was planned to replace certain aspects of HAL, but in March 2009, DeviceKit was deprecated in favor of adding the same code to udev as package , and some functions have now moved to proper. See also devfsd eudev udev UPower References External links HAL - Hardware Abstraction Layer Applications using D-Bus Free system software Freedesktop.org Human–computer interaction Software using the Academic Free License User interfaces

Operating System (OS)

RSX-11 RSX-11 is a discontinued family of multi-user real-time operating systems for PDP-11 computers created by Digital Equipment Corporation. In widespread use through the late 1970s and early 1980s, RSX-11 was influential in the development of later operating systems such as VMS and Windows NT. As the original Real-Time System Executive name suggests, RSX was designed (and commonly used) for real time use, with process control a major use, thereof. It was also popular for program development and general computing. History Name and origins RSX-11 began as a port to the PDP-11 architecture of the earlier RSX-15 operating system for the PDP-15 minicomputer, first released in 1971. The main architect for RSX-15 (later renamed XVM/RSX) was Dennis “Dan” Brevik. Commenting on the RSX acronym, Brevik says: RSX-11D and IAS The porting effort first produced small paper tape based real-time executives (RSX-11A, RSX-11C) which later gained limited support for disks (RSX-11B). RSX-11B then evolved into the fully fledged RSX-11D disk-based operating system, which first appeared on the PDP-11/40 and PDP-11/45 in early 1973. The project leader for RSX-11D up to version 4 was Henry Krejci. While RSX-11D was being completed, Digital set out to adapt it for a small memory footprint giving birth to RSX-11M, first released in 1973. From 1971 to 1976 the RSX-11M project was spearheaded by noted operating system designer Dave Cutler, then at his first project. Principles first tried in RSX-11M appear also in later designs led by Cutler, DEC's VMS and Microsoft's Windows NT. Under the direction of Ron McLean a derivative of RSX-11M, called RSX-20F, was developed to run on the PDP-11/40 front-end processor for the KL10 PDP-10 CPU. Meanwhile, RSX-11D saw further developments: under the direction of Garth Wolfendale (project leader 1972–1976) the system was redesigned and saw its first commercial release. Support for the 22-bit PDP-11/70 system was added. Wolfendale, originally from the UK, also set up the team that designed and prototyped the Interactive Application System (IAS) operating system in the UK; IAS was a variant of RSX-11D more suitable for time sharing. Later development and release of IAS was led by Andy Wilson, in Digital's UK facilities. Release dates Below are estimated release dates for RSX-11 and IAS. Data is taken from the printing date of the associated documentation. General availability date is expected to come closely after. When manuals have different printing dates, the latest date is used. RSX-11S is a proper subset of RSX-11M, so release dates are always assumed to be the same as the corresponding version of RSX-11M. On the other side, RSX-11M Plus is an enhanced version of RSX-11M, so it is expected to be later than the corresponding version of RSX-11M. Legal ownership, development model and availability RSX-11 is proprietary software. Copyright is asserted in binary files, source code and documentation alike. It was entirely developed internally by Digital. Therefore, no part of it is open source. However a copy of the kernel source is present in every RSX distribution, because it was used during the system generation process. The notable exception to this rule is Micro-RSX, which came with a pre-generated autoconfiguring binary kernel. Full sources was available as a separate product to those who already had a binary license, for reference purposes. Ownership of RSX-11S, RSX-11M, RSX-11M Plus and Micro/RSX was transferred from Digital to Mentec Inc. in March 1994 as part of a broader agreement. Mentec Inc. was the US subsidiary of Mentec Limited, an Irish firm specializing in PDP-11 hardware and software support. In 2006 Mentec Inc. was declared bankrupt while Mentec Ltd. was acquired by Irish firm Calyx in December 2006,. The PDP-11 software, which was owned by Mentec Inc. was then bought by XX2247 LLC, which is the owner of the software today. It is unclear if new commercial licenses are possible to buy at this time. Hobbyists can run RSX-11M (version 4.3 or earlier) and RSX-11M Plus (version 3.0 or earlier) on the SIMH emulator thanks to a free license granted in May 1998 by Mentec Inc. Legal ownership of RSX-11A, RSX-11B, RSX-11C, RSX-11D, and IAS never changed hands; therefore it passed to Compaq when it acquired Digital in 1998 and then to Hewlett-Packard in 2002. In late 2015 Hewlett-Packard split into two separate companies (HP Inc. and Hewlett Packard Enterprise), so the current owner cannot be firmly established. No new commercial licenses have been issued since at least October 1979 (RSX-11A, RSX-11B, RSX-11C) or 1990 (IAS), and none of these operating systems have ever been licensed for hobbyist use. Versions Main versions RSX-11A, C – small paper tape real time executives RSX-11B – small real time executive based on RSX-11C with support for disk I/O. To start up the system, first DOS-11 was booted, and then RSX-11B was started. RSX-11B programs used DOS-11 macros to perform disk I/O. RSX-11D – a multiuser disk-based system, later evolved into IAS IAS – a timesharing-oriented variant of RSX-11D released at about the same time as the PDP-11/70. The first version of RSX to include DCL (Digital Command Language), which in IAS is known by its original name, PDS (Program Development System). RSX-11M – a multiuser version that was popular on all PDP-11s RSX-11S – a memory-resident version of RSX-11M used in embedded real-time applications. RSX-11S applications were developed under RSX-11M. RSX-11M-Plus – a much extended version of RSX-11M, originally designed to support the multi-processor PDP-11/74, a computer that was never released, but RSX-11M-Plus was then used widely as a standard operating system on the PDP-11/70. Hardware-specific variants RSX-20F – Customized version of RSX-11M, to be run on PDP-11/40 front end processor operating system for the DEC KL10 processor Micro/RSX – a pre-generated full version of RSX-11M-Plus with hardware autoconfiguration, implemented specifically for the Micro/PDP-11s, a low-cost multi-user system in a box, featuring ease of installation, no system generation, and a special documentation set. Later superseded by RSX-11M Plus. P/OS – A version of RSX-11M-Plus that was targeted to the DEC Professional line of PDP-11-based personal computers Clones in the USSR and other Eastern Bloc countries In 1968, the Soviet Government decided that manufacturing copies of IBM mainframes and DEC minicomputers, in cooperation with other COMECON countries, was more practical than pursuing original designs. Cloning of DEC designs began in 1974, under the name of SM EVM (Cyrillic:СМ ЭВМ). СМ ЭВМ is an acronym for 'Система Малых электронно-вычислительных машин' which is Russian for 'System of Small electronic computing machines'. As happened with ES EVM mainframes based on the System/360 architecture, the Russians and their allies sometimes significantly modified Western designs, and therefore not every SM EVM machine is compatible with DEC offerings of the time. DOS/RV, , ОСРВM – Three names for an unauthorised clone of RSX-11M produced in the Socialist bloc. The name ОСРВ is an acronym for 'Операционная Система Реального Времени', which is Russian for 'Real-time Operating System'. This system appears to be an exact duplicate of RSX-11M except a different header in binary files. Differences between RSX and ОСРВ are due to hardware differences between SM and PDP computers and to bug-fixing done by Soviet engineers. However, the original RSX-11M was more used than its Russian clone ОСРВ, because the programmers modifying the original RSX-11M code were doing a better job, and patched RSX was more stable than ОСРВ. Other benefits included a faster update cycle for drivers and a larger choice of patches, made possible by a wider user community. A clone of the RSX-11M operating system ran on the Romanian-made CORAL family of computers (such as CORAL 2030, a clone of PDP-11). Operation RSX-11 was often used for general-purpose timeshare computing, even though this was the target market for the competing RSTS/E operating system. RSX-11 provided features to ensure better than a maximum necessary response time to peripheral device input (i.e. real-time processing), its original intended use. These features included the ability to lock a process (called a task under RSX) into memory as part of system boot up and to assign a process a higher priority so that it would execute before any processes with a lower priority. In order to support large programs within the PDP-11's relatively small virtual address space of 64 KB, a sophisticated semi-automatic overlay system was used; for any given program, this overlay scheme was produced by RSX's taskbuilder program (called TKB). If the overlay scheme was especially complex, taskbuilding could take a rather long time (hours to days). The standard RSX prompt is ">" or "MCR>", (for the "Monitor Console Routine". All commands can be shortened to their first three characters when entered and correspondingly all commands are unique in their first three characters. Only the login command of "HELLO" can be executed by a user not yet logged in. "HELLO" was chosen as the login command because only the first three characters, "HEL", are relevant and this allows a non-logged in user to execute a "HELP" command. When run on certain PDP-11 processors, each DEC operating system displays a characteristic light pattern on the processor console panel when the system is idle. These patterns are created by an idle task running at the lowest level. The RSX-11M light pattern is two sets of lights that sweep outwards to the left and right from the center of the console (inwards if the IND indirect command file processor program was currently running on older versions of RSX). By contrast, the IAS light pattern was a single bar of lights that swept leftwards. Correspondingly, a jumbled light pattern (reflecting memory fetches) is a visible indication that the computer is under load (and the idle task is not being executed). Other PDP-11 operating systems such as RSTS/E have their own distinctive patterns in the console lights. See also QIO AST Event flag RSTS/E RT-11 References External links Dan Brevik posted a history of precursors to RSX-11 in alt.sys.pdp11. - contains documents which trace RSX-11 back through RSX-15 and the real time executive written by John Neblett in the late 1950s for the RW-300 process control computer by TRW Al Kossow posted some further notes on RSX-11 in alt.sys.pdp11. DEC operating systems Real-time operating systems PDP-11 1972 software Discontinued operating systems

Operating System (OS)

User profiles in Microsoft Windows Microsoft Windows profile refers to the user profile that is used by the Microsoft Windows operating system to represent the characteristics of the user. Windows XP Profile creation Establishing a user account on the computer (or on its parent domain) does not create a profile for that user. The profile is created the first time the user interactively logs on at the computer. Logging on across a network to access shared folders does not create a profile. At first logon, a folder will typically be created under "Documents and Settings" (standard folder on English version of Windows 2000, XP and Windows Server 2003) matching the logon name of the user. Should a folder of that name already exist, the profile-creation process will create a new one, typically named username.computername, on workgroup computers, or username.domainname on Active Directory member computers. Once a profile folder has been created, Windows will never automatically rename that folder. Thus if the username itself is subsequently changed, the profile folder will remain as is, and the profile will no longer match the username, which could lead to confusion. For this reason, the administrator might want to avoid renaming user accounts if at all possible, or rename the folder manually and edit the registry to reflect the changes. The new profile is created by making a copy of a special profile named Default User. It is permissible to modify this Default User profile (within certain guidelines) so as to provide a customized working environment for each new user. Modification of the Default User profile should ideally be done prior to any users logging-on to the computer. If a user has already logged on once or more, the Default Profile has no effect whatsoever for that user. Profile contents NTUSER.DAT Within the root of the profile, a file named NTUSER.DAT contains the user's personalized settings for the majority of software installed on the computer; including Windows itself. When the user logs on, NTUSER.DAT becomes merged with the computer's registry, such that it appears as the HKEY_CURRENT_USER branch of the registry tree. NTUSER.DAT is held open for writing (i.e., "locked") whenever the user is logged on. My Documents This folder is intended to contain the user's work, and in Windows XP-aware programs, dialog boxes will typically prompt the user to store documents here. "My Documents" as a shortcut also appears on the desktop, and in My Computer. It is here that these shortcuts point. Favorites, Cookies, and History These folders are used by Microsoft's Internet Explorer web browser to store surfing data. They are not used by alternative browsers such as Firefox or Opera, which typically store their data under "Application Data." Nethood, Printhood These folders contain the network shares and printers discovered by the user with the My Network Places applet, in the form of shortcuts. Start Menu This folder contains the shortcuts present on the same-named Desktop feature. Desktop This folder contains files and shortcuts present on the user's desktop. Application Data Provided mainly for the use of programmers, as a place to store data that is related to specific software, but which does not fall into the category of documents that a user might open directly. This folder was made necessary by Windows' best practices programming guidelines, which now prohibit the storage of temporary data of any kind in the Program Files folder. Local Settings Functionally similar to "Application Data", and contains a second subfolder of that name. It also contains the temporary files generated by Windows programs themselves, and as a result of Internet Explorer's online activities. For standalone computers the two folders are functionally similar, but on networks employing Roaming profiles, the "Local Settings" folder is not included in the profile synchronization process. Thus, data in the "Local Settings" folder will not be copied between computers when the user roams. Note Some of these subfolders are hidden from the users view in Windows Explorer. To see them you must uncheck "Hide System Folders" in the folder options. Special profiles "Default User" - Plays a role in the profile-creation process, see above. "All Users" - This profile is present mainly to answer an issue related to software installation. It provides a way for setup programs to create desktop or start-menu shortcuts which will be visible to all users of the computer, not just the user running the setup program. The Application Data section may also contain program-data common to all users. "All Users" acts purely as an information-store, it is never loaded as an active profile. "Administrator" - All versions of NT-based Windows have an administrator account and corresponding profile, although on XP this account may only be visible on the logon screen if the computer is started in safe mode. In Windows Vista, it is disabled by default. History and origin Historically, the Windows 95-98 product line did not employ user-profiling as standard, with all users sharing the same settings, although that feature could be activated in Control Panel. The user-profiling scheme in force today owes its origins to Windows NT, which stored its profiles within the system folder itself, typically under C:\WINNT\Profiles\. Windows 2000 saw the change to a separate "Documents and Settings" folder for profiles, and in this respect is virtually identical to Windows XP and Windows Server 2003. Recent developments Windows Vista's profiles are functionally similar to those of Windows XP, but with some differences. Perhaps the key difference is that they are stored in a "C:\Users" folder, instead of "C:\Documents and Settings." Therefore, to cater for programs which are not Vista-ready, a symbolic link is also provided under the name of "Documents and Settings" which invisibly redirects any attempted access of the latter to "C:\Users." The fact that the profile root folder appears twice in any folder listing has adverse implications for any backup program. Backup software needs to be aware of this Vista idiosyncrasy, or else it is possible to double the size of the backup by copying what appear to be two separate folders, both potentially containing the bulk of the data on the computer. A second change in Vista is that the media-specific "My Pictures" and "My Music" folders are now outside of the "My Documents" folder, instead of being subfolders (as well as removing the "My" Prefix - so My Documents becomes Documents, for example). See also User profile Roaming user profile References Vista Profile Guide Microsoft on User Profiles Changing the Windows User Profiles Directory via the registry User Profile Structure Windows administration

Operating System (OS)

WAITS WAITS was a heavily modified variant of Digital Equipment Corporation's Monitor operating system (later renamed to, and better known as, "TOPS-10") for the PDP-6 and PDP-10 mainframe computers, used at the Stanford Artificial Intelligence Laboratory (SAIL) from the mid-1960s up until 1991; the mainframe computer it ran on also went by the name of "SAIL". Overview There was never an "official" expansion of WAITS, but a common variant was "West-coast Alternative to ITS"; another variant was "Worst Acronym Invented for a Timesharing System". The name was endorsed by the SAIL community in a public vote choosing among alternatives. Two of the other contenders were SAINTS ("Stanford AI New Timesharing System") and SINNERS ("Stanford Incompatible Non-New Extensively Rewritten System"), proposed by the systems programmers. Though WAITS was less visible than ITS, there was frequent exchange of people and ideas between the two communities, and innovations pioneered at WAITS exerted enormous indirect influence. WAITS alumni at Xerox PARC and elsewhere also played major roles in the developments that led to the Xerox Star, the Apple Macintosh, and the SUN workstation (later sold by Sun Microsystems). The early screen modes of Emacs, for example, were directly inspired by WAITS' "E" editor -- one of a family of editors that were the first to do real-time editing, in which the editing commands were invisible and where one typed text at the point of insertion/overwriting. The modern style of multi-region windowing is said to have originated there. The system also featured an unusual level of support for what is now called multimedia computing, allowing analog audio and video signals (including TV and radio) to be switched to programming terminals. This switching capability for terminal video even allowed users in separate offices to view and type on the same virtual terminal, or a single user to instantly switch among multiple full virtual terminals. Also invented there were "bucky bits" - thus, the "Alt" key on every IBM PC is a WAITS legacy. One WAITS feature very notable in pre-Web days was a news-wire search engine called NS (for News Service) that allowed WAITS hackers to instantly find, store and be notified about selected AP and New York Times news-wire stories by doing searches using arbitrary combinations of words. News story retrieval by such search was instantaneous because each story was automatically indexed by all its words when it came in over the wire. References External links The autobiography of SAIL FOLDOC description SAILDART archive Time-sharing operating systems 1967 software

Operating System (OS)

Boot image control A boot image control strategy is a common way to reduce total cost of ownership in organizations with large numbers of similar computers being used by users with common needs, e.g. a large corporation or government agency. This is considered part of enterprise application integration in larger shops that use that term since applications are part of the boot image, and modify the boot image, in most desktop OS. Windows Vista includes tools for boot image control, displacing third-party tools. Mac OS has always had more flexible handling of boot drives, simplifying control and reducing the need to move boot images around between drives. Increasingly, boot image control is a network operating system function. Economics Very often a large computer vendor is required to explain in a bid in response to an RFP how they intend to simplify the purchaser's boot image control problems and the attendant service costs: The total cost of ownership correlates strongly to the total number of different images, not the total number of computers, so this is a major cost concern. Three basic strategies are commonly advised: a single base boot image for each type of computer in the organization, customized by each user with no central control a thin client strategy where the smallest possible boot image is used, typically one that does not include a full operating system a departmental boot image strategy where a base boot image is customized with applications to fit each group of users, but, the users do not have the ability to upgrade or alter the configurations Thin client strategies Organizations that do not closely track, control and set common standards for, acquisition of new computer hardware, typically can only practice a thin client strategy. Which strategy will reduce total cost of operations the most depends on several factors: whether the capabilities of a full operating system are required, or just those of a thin client whether applications with inflexible software licenses are in use that must be paid for not only if they are used, but even if they are only installed whether poorly-behaved applications that interact badly are in use LAN or removable disk limits that make it easy or difficult to do re-imaging on demand More complex departmental boot images While the departmental boot image strategy seems to be the most flexible, the complexity of creating and managing several large boot images, and determining when a department needs to upgrade its applications, can easily outweigh these. Especially if users object and try to subvert the discipline of waiting for a regular boot turn to upgrade all machines at once. If each user is allowed to do this on their own, then, the discipline soon degrades into effectively a bunch of home computer whose issues are not really diagnosable nor comparable to each other. In which situation thin clients may become the only practical answer: Many organizations use thin clients for applications which require high security, involve unreliable users or repurpose older machines for continued use. This much simplifies boot image control by facilitating centralized management of computers, and has many advantages: since servers manage clients and the local environment is highly restricted (and often stateless), providing protection from malware, support costs are reduced since no application data typically resides on the thin client (it is entirely rendered), it is securely stored on network drives upon its creation since disk, application memory, and processors are minimal in thin client hardware, they go obsolete slowly and cost much less since they are not as useful as ordinary computers they are of less interest to thieves While control of the images is simpler, there are disadvantages. Thin clients: require more network bandwidth require more host computer power and must typically be served by much larger host boxes typically cannot run arbitrary Windows, Linux or Mac software perform poorly in multimedia applications or games - an advantage in many business environments Many organizations try to gain the advantages of thin clients without the disadvantages by treating many very standard machines as if they were terminals, but with very much greater capabilities. As they buy new computers, they put the demanding applications on those. Boot turns and re-imaging Administrators perform a regular (often bi-annual) boot turn that re-images many older, off-spec machines at once so that new hardware can be deployed for higher-end use. This procedure is called cascading: the oldest hardware is repurposed with simpler software to let it continue in use for some less demanding or more access-controlled applications, but subjects it to much more rigorous control to minimize the number of images. The total cost of operations correlates strongly to the total number of different images, not the total number of computers. To minimize the number of images requires additional discipline: Specify the computer hardware to minimize unneeded machine diversity and minimize the resultant number of boot images. Upgrade new machine specifications at low additional cost so they remain useful longer, reduce the incursion of off-spec machines later in the life-cycle, improve standardization, reduce support costs, minimize e-waste with longer lifecycles Organize the network so that boot images can be efficiently supported and swapped, independent of data. Data must not be dependent on boot devices - use networks to store data on secure servers so that data recovery is literally never required even in a disaster recovery situation Confirm, by hardware acceptance testing on each new machine, that it runs the standard boot image Any machine that does not must be considered to be dead on arrival A strict installation regime to ensure that only supportable standardized boot images are used and any machines that connect to the network for the first time with a nonstandard image are detected and rejected Diagnostics and troubleshooting so that help desk and other technical support staff can employ standardized tests to identify the source of problems: boot, software, or hardware Ideally, backups on hand of the boot image, or even spare identical computers that can quickly be booted up from the boot device in question to determine if it is a hard disk, computer or software/image problem. Common desktop system recovery tools and procedures for failed desktop units, typically using backup copies of a boot image created with utilities Rapid network recovery procedures that replace a backup boot image in a few minutes or less, with considerable cost savings over using DVD, CD or floppy disk media which require human attention Ensure computer accessibility features are on every departmental boot image that require them, or in the thin client hardware and software itself, to accommodate these users in a manner that is ubiquitous and cost effective. Support telework and secure off-site system access procedures in the standard boot image Encourage teleworkers to buy identical machines to those in the office or use thin clients exclusively Facilitate worker transfer by changing boots or authorizations instead of moving the actual computer Install thin clients on all off-spec machines to eliminate the need for special boot images for them, and subsequent diagnostic problems and data risks. Open configuration and semantic services Desktop computing is increasingly relying on web services, making the thin client approach more viable. Departmental boot images may remain but simply instantiate part of a semantic service-oriented architecture, especially in larger organizations. A service component architecture would further simplify the implementation of control mechanisms, especially if a single application language like Java was used for all custom applications in the enterprise. More importantly, shift to software as a service by most large vendors means that applications are not tied to machines, so the number of variant boot images required (with the applications installed) is reduced. Other open configuration technologies such as Bitfrost, OpenID and even XMPP would also simplify configuration of boot images, as authentication would no longer be dealt with on the desktop/laptop device. Vendor support Large system vendors increasingly provide DVDs with the boot image standard for the machine as shipped to the customer, which usually includes tools to diagnose changes to the machine and download drivers. Booting Disk images Enterprise application integration

Operating System (OS)

Software appliance A software appliance is a software application combined with just enough operating system (JeOS) to run optimally on industry-standard hardware (typically a server) or in a virtual machine. It is a software distribution or firmware that implements a computer appliance. Virtual appliances are a subset of software appliances. The main distinction is the packaging format and the specificity of the target platform. A virtual appliance is a virtual machine image designed to run on a specific virtualization platform, while a software appliance is often packaged in more generally applicable image format (e.g., Live CD) that supports installations to physical machines and multiple types of virtual machines. Installing a software appliance to a virtual machine and packaging that into an image, creates a virtual appliance. Benefits Software appliances have several benefits over traditional software applications that are installed on top of an operating system: Simplified deployment: A software appliance encapsulates an application's dependencies in a pre-integrated, self-contained unit. This can dramatically simplify software deployment by freeing users from having to worry about resolving potentially complex OS compatibility issues, library dependencies or undesirable interactions with other applications. This is known as a "toaster." Improved isolation: software appliances are typically used to run applications in isolation from one another. If the security of an appliance is compromised, or if the appliance crashes, other isolated appliances will not be affected. Improved performance: A software appliance does not embed any unused operating system services, applications or any form of bloatware hence it does not have to share the hardware resources (CPU, memory, storage space, ...) usually consumed by these on a generic OS setup. This naturally leads to faster boot time and application execution speed. In the case where multiple software appliances share and run simultaneously on the same hardware (on a virtualization platform for example) this will not hold true as running n instances of a software appliance (OS + software application) will consume more hardware resources than running n instances of a software application on 1 instance of an operating system due to the overhead of running n - 1 more instances of operating system. Types of software appliances Virtual appliance A software appliance can be packaged in a virtual machine format as a virtual appliance, allowing it to be run within a virtual machine container. A virtual appliance could be built using either a standard virtual machine format such as Open Virtualization Format (OVF), or a format specific to a particular virtual machine container (for example, VMware, VirtualBox, or Amazon EC2). Live CD appliance A software appliance can be packaged as a Live CD image, allowing it to run on real hardware in addition to most types of virtual machines. This allows developers to avoid the complexities involved in supporting multiple incompatible virtual machine image formats and focus on the lowest common denominator instead (i.e., ISO images are supported by most Virtual Machine platforms). Commercial software appliances Commercial software appliances are typically sold as a subscription service (pay-as-you-go) and are an alternative approach to software as a service. Customers can receive all service and maintenance from the application vendor, eliminating the requirement to manage multiple maintenance streams, licenses, and service contracts. In some cases, the application vendor may install the software appliance on a piece of hardware prior to delivery to the customer, thereby creating a computer appliance. In both cases, the primary value to the customer remains the simplicity of purchase, deployment, and maintenance. See also Portable application Virtual appliance BitNami TurnKey Linux Virtual Appliance Library AMAX Information Technologies - builds x86 turnkey software appliances for ISVs SUSE Studio - builds software appliances Windows To Go References Software distribution Operating system distributions bootable from read-only media

Operating System (OS)

MikroSim MikroSim is an educational software computer program for hardware-non-specific explanation of the general functioning and behaviour of a virtual processor, running on the Microsoft Windows operating system. Devices like miniaturized calculators, microcontroller, microprocessors, and computer can be explained on custom-developed instruction code on a register transfer level controlled by sequences of micro instructions (microcode). Based on this it is possible to develop an instruction set to control a virtual application board at higher level of abstraction. General Initially MikroSim was developed to be a processor simulation software to be widely available in educational areas. Since MikroSim operability starts on the basis of microcode development, defined as a sequence of micro instructions (microcoding) for a virtual control unit, the software's intention is on first approach a microcode simulator with various levels of abstractions including the ability of CPU simulators and instruction set emulators. In the current software revision it is feasible for a microcode controlled virtual application to operate on own coded instruction sets. With MikroSim typical and well-known concepts in the area of computer engineering like computer architecture and instruction set architecture are non-specifically treated, which have been established since the early days of the information era and being still valid. In this fashion the simulation software gains a timeless, free didactical benefit without being restricted on special developments of the past and in the future. The detailed documentation and the bilingual application's graphical user interface (GUI) in German and English, as well as the software's upward compatibility given to some extent by Microsoft's operating system Windows, are reasons for being a well-established, valuable e-learning tool in the field of computer engineering since 1992 for educational use. History of development The software is based on a version written under Turbo Pascal compiled for MS-DOS operating systems which has been used for educational purposes in computer engineering and computer science at the Philipps-University Marburg (Germany) until 1992. The concept was picked up by Martin Perner during his study of physics (1990–95) in summer 1992, revised, and converted into a windows application compiled with Microsoft Visual Basic and running on Windows 3.1x. In doing so, at this time a simulator with huge conceptual improvements arose by exploiting the novel functionality and utilisation of MS Windows’ GUI for supporting the composition of microcode and the traceability of its instructional influence. The enhancements of the e-learning tool under Windows has been supported and promoted by the Fachbereich Mathematik/Informatik of the University of Marburg by Heinz-Peter Gumm until end 1995. The Simulator has been awarded with the ‘’European Academic Software Award 1994’’ in the computer science category in Heidelberg (Germany) in November 1994. In March 1995 the simulator was presented at the computer exhibition CeBIT’95 in Hannover at the exhibit of the ‘’Hessischen Hochschulen’’. Between 1995 and 2000 the simulator was published as ‘’Mikrocodesimulator MikroSim 1.2’’ without any significant improvements. At this time the tool received an award of 1000 ECU from the European Union in conjunction with the ‘’European Year of Livelong Learning 1996’’. In 1997, the software was presented at the contest ‘’Multimedia Transfer’97’’ in connection to the exhibition ‘’LearnTec’97’’. In its penultimate revision, the simulator has been published under ‘’Mikrocodesimulator MikroSim2000’’, optimized for MS Windows 95’s 32-bit operation. Between 2008 and 2009, the simulator concept has been revised, reworked, and thoughtful extended. So it has received wide-ranging improvements and extensions without touching the successful conceptual aspects of the microcode simulation abilities in the core. For this purpose, advantage is taken of today’s computing system’s performance determined by operating system and underlying computational power to extend MikroSim’s simulation possibilities up to the stage of a virtual application board. MikroSim is compiled and optimized for sake of unrestricted compatibility and for widest distribution possible for MS Windows XP as a 32-bit version. The program runs on all 32- and 64-bit operating systems of MS Windows Vista and MS Windows 7. Thereby, no special XP compatibility mode is needed. Since January 2010, the simulator is distributed as ‘’Mikrocodesimulator MikroSim 2010’’ by 0/1-SimWare. Functionality The windows application allows for the gradual establishment of a virtual application that is predetermined and such unchangeable in its functionality. In exploration mode, the operating principle and control of newly added components influenced by one microcode instruction within a cycle can be evaluated. The width of MikroSim’s micro instructions is 49 bits. A single micro instruction is executed in three phases of a 3-phase clock. The partial phases are referred to as “GET”, “CALCULATE” and “PUT” phase, causing to fetch some register value, to execute a 32-bit calculation, and to store the calculation result into a CPU's internal register, finally. In simulation mode, seamlessly executed micro instructions control the central processing unit of the simulator in subsequent cycles. Therefore, the intrinsic ability of one micro instruction is utilized to address the next micro instruction in the control store. The control store holding the micro instruction set (commonly referred as "microcode") comprises 1024 micro instructions words each 49-bit wide. Using structuring opportunities of the control store for addressable scheduling of the microcode and the implementation of a cyclically operating machine code interpreter, that is programmed in microcode as well allows the implementation of individual micro-operation sequences, known as machine instructions. The microcode can be regarded as firmware for MikroSim, that can be modified, and stored in and reloaded from a microcode-ROM-file. Within a micro instruction execution cycle, the CPU as well as an input / output controller is connected to an external 16 kByte huge random access memory device (RAM). Via the input-output controller device, communication with virtual input and output devices is supported by Direct Memory Access mode (DMA), Inter-Integrated Circuit Connection (I2C), and Interrupt request functionality (IRQ). A output port, a display, a timer, an event trigger, a digital-analog converter, a keyboard and data input / output channel is provided as virtual IC device for explaining didactically the communication with external devices. The microcode simulator uses eight freely usable register each 32-bit wide connected with a 32-bit arithmetic logic unit (ALU). The register content can be regarded as signed or unsigned integer values, or as 32-bit floating point numbers. The register content can be easily viewed, interpreted, and modified bitwise an integrated system number editor. The 32-bit ALU is the key unit of the central processing unit. It supports 128 different basic arithmetic operations for integer operation, interrupt control, and for floating point arithmetic. The didactical approach to floating point calculations, which has been introduced in a comparable manner already in the early 1940s by Konrad Zuse, is introduced by using elemental sublevel operations for exponent and mantissa involved in the key operations of addition/subtraction and multiplication/division. A set of powerful 32-bit floating point arithmetic commands in mantissa and exponent for the basic operations and elementary analytical functions are provided, as they are realized in today's mathematical coprocessors. Here, in the simulation with MikroSim it is ideally assumed that the execution of each supported ALU arithmetic operation requires only a distinct computing duration independent of circuit complexity realistically needed in practice. The execution of micro instructions can be operated on various simulation levels with different temporal resolution: In the lowest simulation level, the simulator supports the phased wise execution of GET, CALCULATE, and PUT phase. The processing of the partial phases is possible with an adjustable delay for better traceability. In next upper level, the current micro instruction is executed in a complete three-phase clock without time delay. A continuous execution of several 3-phase clock cycles is supported within a so-called “Load Increment Execute” (LIE) cycle. The LIE cycle regarded as an interpreter written in microcode has the function to load machine instructions coded as byte value from the external RAM and to let branch the micro instruction sequence to the referenced microcode subroutine for execution given by the opcode and returning to the LIE back to retrieve the next machine instruction. One execution level higher, a sequence of several machine instructions are executable until a user-defined break point is reached, which is placed in the machine code sequence. It is possible to measure run times between break points. So it is possible to benchmark execution performance on machine and microcode level. In the top most simulation level the microcode simulator continuously executes micro instructions without interrupt. In this level, machine instruction by machine instruction is loaded. So, it is possible to focus on the interaction of the CPU with external devices. With various additional options, visual CPU activities can be suppressed for the benefit of increasing the processing speed when the control of the application by machine programming is put forward. The performance index monitor provided with the simulator enables the user to benchmark the processing performance of MikroSim and setting it into relation with computing power of the simulator's hardware, measurable in floating-point operations per second (FLOPS) and instructions per second (IPS). With the so-called ’’Basic Assembler Tool for MikroSim’’ MikroBAT, simple programs can be developed in assembler programming language. Here, all supported mnemonics of the assembler programming language are determined by the user's self-created machine's instruction set on micro instruction level. The add-on tool is able to translate the assembly language program into machine code and data and transferring the binary code into the external RAM for subsequent simulations. Together with MikroBAT the microcode simulator MikroSim supports the didactical introduction of teaching aspects in technical computer science from a switch-controlled calculating machine to an assembler programmable application. See also Computer architecture simulator Cycle Accurate Simulator Educational programming language Full system simulator Instruction set simulator Instrumentation (computer programming) von Neumann architecture Literature . References External links Educational abstract machines Simulation software

Operating System (OS)

Windowing system In computing, a windowing system (or window system) is software that manages separately different parts of display screens. It is a type of graphical user interface (GUI) which implements the WIMP (windows, icons, menus, pointer) paradigm for a user interface. Each currently running application is assigned a usually resizable and usually rectangular surface of the display to present its GUI to the user; these windows may overlap each other, as opposed to a tiling interface where they are not allowed to overlap. Usually a window decoration is drawn around each window. The programming of both the window decoration and of available widgets inside of the window, which are graphical elements for direct user interaction, such as sliders, buttons, etc., is eased and simplified through the use of widget toolkits. Technical details The main component of any windowing system is usually called the display server, although alternative denominations such as window server or compositor are also in use. Any application that runs and presents its GUI in a window, is a client of the display server. The display server and its clients communicate with each other over a communications protocol, which is usually called display server protocol, the display server being the mediator between the clients and the user. It receives all the input from the kernel, that the kernel receives from all attached input devices, such as keyboard, pointing devices, or touchscreen and transmits it to the correct client. The display server is also responsible for the output of the clients to the computer monitor. The output of sound is usually not managed by the display server, but the sound volume is usually handled through GUI applets and it is the display server who decides which applications are on top. A windowing system enables the computer user to work with several programs at the same time. Each program presents its GUI in its own window, which is generally a rectangular area of the screen. From a programmer's point of view, a windowing system implements graphical primitives. For example: rendering fonts or drawing a line on the screen. It provides an abstraction of the graphics hardware for use by higher-level elements of the graphical interface such as a window manager. A display server protocol can be network capable or even network transparent, facilitating the implementation of thin clients. Display server A display server or window server is a program whose primary task is to coordinate the input and output of its clients to and from the rest of the operating system, the hardware, and each other. The display server communicates with its clients over the display server protocol, a communications protocol, which can be network-transparent or simply network-capable. The display server is a key component in any graphical user interface, specifically the windowing system. Display server communications protocols X11 One example of a display server is the X.Org Server, which runs on top of the kernel (usually a Unix-like kernel, such as Linux or BSD). It receives user input data (e.g. from evdev on Linux) and passes it to one of its clients. The display server also receives data from its clients; it processes the data, it does the compositing and on Linux it passes the data to one of three kernel components – DRM, gem or KMS driver. The component writes the data into the framebuffer and content of the framebuffer is transmitted to the connected screen and displayed. X relies on GLX. One of the implementations of display server concept is X Window System, in particular its actually used version – X.Org Server and Xlib and XCB client libraries. The X.Org Server is a display server, but in its current implementation it relies on a second program, the compositing window manager, to do the compositing. Examples are Mutter or KWin. Notable examples of display servers implementing the X11 display server protocol are X.Org Server, XFree86, XQuartz and Cygwin/X, while client libraries implementing the X11 display server protocol are Xlib and XCB. Wayland Display servers that implement the Wayland display server protocol, are called Wayland compositors. Like any display server, a Wayland compositor is responsible for handling input and output for its clients and – in contrast to X11 – additionally for the compositing. Examples are Weston, Mutter, KWin or Enlightenment. Wayland compositors communicate with Wayland clients over the Wayland display server protocol. This protocol defines that clients can directly write data into the framebuffer using the EGL rendering API. The display server still gets to decide which window is on top and thus visible to the user and also still is responsible for passing data regarding to input devices from evdev to its clients. Wayland is used to a certain degree in some Linux desktop distributions, such as Fedora. It is also well suited for mobile computing and has been adopted, for example, by the smartphone- and tablet-focused projects Tizen, Sailfish OS and AsteroidOS. An implementation of Wayland is available under the MIT License, the libwayland-client and libwayland-server libraries. There is an ongoing effort to add Wayland support to Chrome OS. Mir The Mir display server comes with its own Mir display server protocol which is different from those used by X11 and Wayland. Mir additionally supports the X11 protocol. It was developed by Canonical and was intended to be the display server of choice for Ubuntu. As of 2017, it has been replaced with the Wayland display server for desktop editions of Ubuntu. There are implementations of the Mir display server, the libmir-server and the libmir-client libraries available under the GPLv3. SurfaceFlinger Google developed a display server called SurfaceFlinger for Android (another Linux kernel-based operating system primarily for mobile devices): Everything in Android is rendered to a "surface"; "surfaces" are produced by applications and placed into a queue that is managed by SurfaceFlinger. Yet another Android-specific solution is "Gralloc". Gralloc handles device memory i.e. it does allocation, arbitration, it handles synchronization via Android/Linux fence file descriptors. Gralloc competes with other solutions like e.g. Mesa's Generic Buffer Management (GBM) or Nvidia's EGLStreams. The Gralloc hardware abstraction layer (HAL) is used to allocate the buffers that underlie "surfaces". For compositing in Android, Surfaces are sent to SurfaceFlinger, which uses OpenGL ES to do the compositing. Hardware Composer HAL (HWC) was introduced in Android 3.0 and has evolved steadily over the years. Its primary purpose is to determine the most efficient way to composite buffers with the available hardware. As a HAL, its implementation is device-specific and usually done by the display hardware OEM. Quartz Compositor For Apple's macOS family of operating systems, Quartz Compositor fulfils the tasks of a display server and of a window manager in the windowing system. Desktop Window Manager For Microsoft Windows, from Windows Vista onward, Desktop Window Manager enables the use of hardware acceleration to render the graphical user interface. It was originally created to enable portions of the new "Windows Aero" user experience, which allowed for effects such as transparency, 3D window switching and more. It is also included with Windows Server 2008, but requires the "Desktop Experience" feature and compatible graphics drivers to be installed. List of windowing systems For Unix-like operating systems 8½ and rio for Plan 9 FramebufferUI in-kernel windowing system HP Windows/9000 (on early versions of HP-UX) Sapphire for the PERQ ManaGeR (MGR) Metisse Mir NeWS / OpenWindows NeXT DPS Orbital (Redox) Qt Extended Quartz Compositor (Mac OS X) SunView Twin (Text WINdows) W Window System Wayland X Window System XFast Xynth For Windows NT-family operating systems Desktop Window Manager (DWM) in Microsoft Windows (Vista and later) ReactOS Explorer Classic Shell Pokki RetroUI Talisman Desktop Web windowing systems Dojo ExtJS TIBCO General Interface Web Window Manager Other DM GEM Intuition Microwindows MiniGUI OOHG Visi On VWS (VAX Workstation Software) Commercial systems such as Microsoft Windows (XP, 9x and earlier), the classic Mac OS (version 9 and earlier), and Palm OS, contain a windowing system which is integrated with the OS. See also List of display servers History of the graphical user interface Widget toolkit Desktop environment References

Operating System (OS)

Windows Driver Model In computing, the Windows Driver Model (WDM) also known at one point as the Win32 Driver Model is a framework for device drivers that was introduced with Windows 98 and Windows 2000 to replace VxD, which was used on older versions of Windows such as Windows 95 and Windows 3.1, as well as the Windows NT Driver Model. Overview WDM drivers are layered in a stack and communicate with each other via I/O request packets (IRPs). The Microsoft Windows Driver Model unified driver models for the Windows 9x and Windows NT product lines by standardizing requirements and reducing the amount of code that needed to be written. WDM drivers will not run on operating systems earlier than Windows 98 or Windows 2000, such as Windows 95 (before the OSR2 update that sideloads the WDM model), Windows NT 4.0 and Windows 3.1. By conforming to WDM, drivers can be binary compatible and source-compatible across Windows 98, Windows 98 Second Edition, Windows Me, Windows 2000, Windows XP, Windows Server 2003 and Windows Vista (for backwards compatibility) on x86-based computers. WDM drivers are designed to be forward-compatible so that a WDM driver can run on a version of Windows newer than what the driver was initially written for, but doing that would mean that the driver cannot take advantage of any new features introduced with the new version. WDM is generally not backward-compatible, that is, a WDM driver is not guaranteed to run on any older version of Windows. For example, Windows XP can use a driver written for Windows 2000 but will not make use of any of the new WDM features that were introduced in Windows XP. However, a driver written for Windows XP may or may not load on Windows 2000. WDM exists in the intermediary layer of Windows 2000 kernel-mode drivers and was introduced to increase the functionality and ease of writing drivers for Windows. Although WDM was mainly designed to be binary and source compatible between Windows 98 and Windows 2000, this may not always be desired and so specific drivers can be developed for either operating system. Device kernel-mode drivers With the Windows Drivers Model (WDM) for devices Microsoft implements an approach to kernel mode drivers that is unique to Windows operating systems. WDM implements a layered architecture for device drivers, and every device of a computer is served by a stack of drivers. However, every driver in that stack can chain isolate hardware-independent features from the driver above and beneath it. So drivers in the stack do not need to interact directly with one another. WDM defines architecture and device procedures for a range of devices, such as display and the network card, known as Network Driver Interface Specification (NDIS). In the NDIS architecture the layered network drivers include lower-level drivers that manage the hardware and upper-level drivers that implement network data transport, such as the Transmission Control Protocol (TCP). While WDM defines three types of device drivers, not all driver stacks for a given device contain all types of device drivers. The three WDM device driver types are: Bus driver: For every bus on the mainboard there is a one bus driver, with the primary responsibility for the identification of all devices connected to that bus and responding to plug and play events. Microsoft will provide bus drivers as part of the operating system, such as PCI, PnPISA, SCSI, USB and FireWire. Function driver: this is the principal driver for a device and it provides the operational interface for a device by handling read and write operations. Function drivers are written by the device vendors, and for their interaction with the hardware they depend on a specific bus driver being present in the Windows operating system. Filter driver: This driver is optional, and can modify the behaviour of a device, such as input and output requests. These drivers can be implemented as lower-level and upper-level filter drivers. Object-oriented driver stack Function drivers and bus drivers are often implemented as driver/minidriver pairs, which in practice is either a class or miniclass, or a port or miniport pair. Bus drivers for devices attached to a bus are implemented as class drivers and are hardware-agnostic. They will support the operations of a certain type of device. Windows operating systems include a number of class drivers, such as the kbdclass.sys driver for keyboards. Miniclass drivers on the other hand are supplied by the vendor of a device, and only support device specific operations, for a particular device of a given class. Port drivers support general input/output (I/O) operations for a peripheral hardware interface. The core functionality of port drivers is mandated by the operating system, and Windows operating systems integrate a variety of port drivers. For example, the i8042prt.sys port driver for the 8042 microcontroller connects PS/2 keyboards to the mainboard peripheral bus. The miniport drivers, like the miniclass drivers, are supplied by the hardware vendors and support only device specific operations of peripheral hardware that is connected to a port on the mainboard. Each driver that processes an I/O request for a device has a corresponding object, which is loaded into main memory. A device object is created by the Windows operating system from the associated device class. Device objects contain structures of type DEVICE_OBJECT, which store pointers to their driver. At run time these pointers are used to locate a driver's dispatch routine and member functions. In the WDM driver stack, the filter driver device object, known as the upper filter, will receive an I/O request packet (IRP) for a device from the I/O manager. If the upper filter driver can not serve the request, it will locate the object of the driver one step down in the driver stack. The IRP is passed down the driver stack by calling the function IoCallDrive(), and processed by the function driver device object, also known as functional device object. The function driver device object in turn may pass the IRP to the lower filter, another filter device object. Then the IRP may be passed down to the bus driver, which operates as the physical device object. The bus driver object is at the bottom of the driver stack, and interacts with the hardware abstraction layer, which is part of the Windows operating system kernel and allows Windows operating systems to run on a variety of processors, different memory management unit architectures, and a variety of computer systems with different I/O bus architectures. The execution of an IRP is finished when any of the driver objects in the stack returns the request back to the I/O manager, with the result and a status flag. Device drivers for different Windows operating systems The WDM framework was developed by Microsoft to simplify the communication between the operating system and drivers inside the kernel. In Windows operating systems, drivers are implemented as Dynamic Link Libraries .DLL or .SYS files. WDM compliant drivers must follow rules of design, initialisation, plug-and-play, power management and memory allocation. In practice WDM driver programmers reuse large pieces of code when building new object-oriented drivers. This means that drivers in the WDM stack may contain residual functionality, which is not documented in specifications. Drivers that have passed the Microsoft quality test are digitally signed by Microsoft. The Microsoft Hardware Compatibility Tests and the Driver Development Kit include reliability and stress tests. A device driver that is not designed for a specific hardware component may allow another device to function. This is because the basic functionality of a hardware device class is similar. The functionality of the video card class, for example, allows the Microsoft Basic Display Adapter driver to work with a wide variety of video cards. However, installing the wrong driver for a device will mean that the full functionality of the device can not be used, and may result in poor performance and the destabilization of the Windows operating system. Hardware device vendors may release updated device drivers for particular Windows operating systems, to improve performance, add functionality or fix bugs. If a device is not working as expected the latest device drivers should be downloaded from the vendor website and installed. Device drivers are designed for particular Windows operating system versions, and device drivers for a previous version of Windows may not work correctly or at all with other versions. Because many device drivers run in kernel mode installing drivers for a previous operating system version may destabilise the Windows operating system. Migrating a computer to a higher version of a Windows operating system therefore requires that new device drivers are installed for all hardware components. Finding up to date device drivers and installing them for Windows 10 has introduced complications into the migration process. Common device driver compatibility issues include: a 32-bit device driver is required for a 32-bit Windows operating system, and a 64-bit device driver is required for a 64-bit Windows operating system. 64-bit device drivers must be signed by Microsoft, because they run in kernel mode and have unrestricted access to the computer hardware. For operating systems prior to Windows 10 Microsoft allowed vendors to sign their 64-bit drivers themselves, assuming vendors had undertaken compatibility tests. However, Windows 10 64-bit drivers now need to be signed by Microsoft. Therefore, device vendors have to submit their drivers to Microsoft for testing and approval. The driver installation package includes all files in the .inf directory, and all files in the package need to be installed, otherwise the installation of the device driver may fail. For operating system versions before Windows 10 not all files necessary for the driver installation were included in the package, as this requirement was not consistently enforced. Some device driver installers have a user interface GUI, often requiring user configuration input. The absence of a user interface does not mean that the installation of the device driver is not successful. Besides, Windows 10 device drivers are not allowed to include a user interface. The Network Driver Interface Specification (NDIS) 10.x is used for network devices by the Windows 10 operating system. Network device drivers for Windows XP use NDIS 5.x and may work with subsequent Windows operating systems, but for performance reasons network device drivers should implement NDIS 6.0 or higher. Similarly, WDDM is the driver model for Windows Vista and up, which replaces XPDM used in graphics drivers. Device Manager The Device Manager is a Control Panel applet in Microsoft Windows operating systems. It allows users to view and control the hardware attached to the computer. It allows users to view and modify hardware device properties, and is also the primary tool to manage device drivers. Criticism The Windows Driver Model, while a significant improvement over the VxD and Windows NT Driver Model used before it, has been criticised by driver software developers, most significantly for the following: Interactions with power management events and plug and play are difficult. This can lead to situations where Windows machines cannot enter or exit sleep modes correctly due to bugs in driver code. I/O cancellation is difficult to get right. Complex boilerplate support code is required for every driver. There is no support for writing pure user-mode drivers. There were also a number of concerns about the quality of documentation and samples that Microsoft provided. Because of these issues, Microsoft has released a new set of frameworks on top of WDM, called the Windows Driver Frameworks (WDF; formerly Windows Driver Foundation), which includes Kernel-Mode Driver Framework (KMDF) and User-Mode Driver Framework (UMDF). Windows Vista supports both pure WDM and the newer WDF. KMDF is also available for download for Windows XP and even Windows 2000, while UMDF is available for Windows XP and above. See also Windows Driver Frameworks (WDF) Kernel-Mode Driver Framework (KMDF) User-Mode Driver Framework (UMDF) Windows Display Driver Model (WDDM) References Finnel, Lynn (2000). MCSE Exam 70-215, Microsoft Windows 2000 Server. Microsoft Press. . Oney, Walter (2003). Programming the Windows Driver Model, Microsoft Press, . External links WDM Input Output Concepts - This article gives a high level overview of the I/O concepts as defined in the Windows Driver Model. Windows driver API basics - This article informs you about the basics behind sound card drivers such as WDM, ASIO, MME, DirectX, etc. Channel 9 Video - Interview with the Device Management and Installation team at Microsoft, primarily covering Plug-and-play. - Free lecture notes book fragment detailing basic creation of Windows Drivers, Kernel Mode programming, and Memory management Device drivers Driver Model Windows 98

Operating System (OS)

History of IBM mainframe operating systems The history of IBM mainframe operating systems is significant within the history of mainframe operating systems, because of IBM's long-standing position as the world's largest hardware supplier of mainframe computers. IBM mainframes run operating systems supplied by IBM and by third parties. The operating systems on early IBM mainframes have seldom been very innovative, except for TSS/360 and the virtual machine systems beginning with CP-67. But the company's well-known reputation for preferring proven technology has generally given potential users the confidence to adopt new IBM systems fairly quickly. IBM's current mainframe operating systems, z/OS, z/VM, z/VSE, and z/TPF, are backward compatible successors to those introduced in the 1960s. Before System/360 IBM was slow to introduce operating systems. General Motors produced General Motors OS in 1955 and GM-NAA I/O in 1956 for use on its own IBM computers; and in 1962 Burroughs Corporation released MCP and General Electric introduced GECOS, in both cases for use by their customers. The first operating systems for IBM computers were written in the mid-1950s by IBM customers with very expensive machines at , which had sat idle while operators set up jobs manually, and so they wanted a mechanism for maintaining a queue of jobs. These operating systems run only on a few processor models and are suitable only for scientific and engineering calculations. Other IBM computers or other applications function without operating systems. But one of IBM's smaller computers, the IBM 650, introduced a feature which later became part of OS/360, where if processing is interrupted by a "random processing error" (hardware glitch), the machine automatically resumes from the last checkpoint instead of requiring the operators to restart the job manually from the beginning. From General Motors GM-NAA I/O to IBSYS General Motors Research division produced GM-NAA I/O for its IBM 701 in 1956 (from a prototype, GM Operating System, developed in 1955), and updated it for the 701's successor. In 1960 the IBM user association SHARE took it over and produced an updated version, SHARE Operating System. Finally IBM took over the project and supplied an enhanced version called IBSYS with the IBM 7090 and IBM 7094 computers. IBSYS required 8 tape drivesfewer if one or more disk drives are present. Its main components are: a card-based Job Control language, which is the main user interface; compilers for FORTRAN and COBOL; an assembler; and various utilities including a sort program. In 1958, the University of Michigan Executive System adapted GM-NAA I/O to produce UMES, which was better suited to the large number of small jobs created by students. UMES was used until 1967 when it was replaced by the MTS timesharing system. BESYS Bell Labs produced BESYS (sometimes referred to as BELLMON) and used it until the mid-1960s. Bell also made it available to others without charge or formal technical support. FORTRAN Monitor System Before IBSYS, IBM produced for its IBM 709, 7090 and 7094 computers a tape-based operating system whose sole purpose was to compile FORTRAN programs—in fact FMS and the FORTRAN compiler were on the same tape. Early time-sharing and virtual machine systems MIT's Fernando Corbató produced the first experimental time-sharing systems, such as CTSS, from 1957 to the early 1960s, using slightly modified IBM 709, IBM 7090, and IBM 7094 mainframes; these systems were based on a proposal by John McCarthy. In the 1960s IBM's own laboratories created experimental time-sharing systems, using standard mainframes with hardware and microcode modifications to support virtual memory: IBM M44/44X in the early 1960s; CP-40 from 1964 to 1967; CP-67 from 1967 to 1972. The company even released CP-67 without warranty or technical support to several large customers from 1968 to 1972. CP-40 and CP-67 used modified System/360 CPUs, but the M44/44X was based on the IBM 7044, an earlier generation of CPU which was very different internally. These experimental systems were too late to be incorporated into the System/360 series which IBM announced in 1964 but encouraged the company to add virtual memory and virtual machine capabilities to its System/370 mainframes and their operating systems in 1972: The M44/44X showed that a partial approach to virtual machines was not good enough and that thrashing could severely reduce the speed of virtual memory systems. Thrashing is a condition in which the system runs very slowly because it spends a lot of its time shuffling virtual memory pages between physical memory and disk files. IBM learned from CP-40 and CP-67: how to make the thrashing problem manageable; that its other virtual memory and virtual machine technologies were sufficiently fast and reliable to be used in the high-volume commercial systems which were its core business. In particular, IBM's David Sayre convinced the company that automated virtual memory management could consistently perform at least as well as the best programmer-designed overlay schemes. In 1968 a consulting firm called Computer Software Systems used the released version of CP-67 to set up a commercial time-sharing service. The company's technical team included 2 recruits from MIT (see CTSS above), Dick Orenstein and Harold Feinleib. As it grew, the company renamed itself National CSS and modified the software to increase the number of paying users it could support until the system was sufficiently different that it warranted a new name, VP/CSS. VP/CSS was the delivery mechanism for National CSS' services until the early 1980s, when it switched to IBM's VM/370 (see below). Universities produced three other S/360 time-sharing operating systems in the late 1960s: The Michigan Terminal System (MTS) was developed in 1967 by a consortium of universities led by the University of Michigan. All versions ran on IBM's mainframes which had virtual memory capability, starting with the S/360-67. MTS remained in use until 1999. McGill University in Montreal started developing MUSIC (McGill University System for Interactive Computing) in 1969. MUSIC was enhanced several times and eventually supported text searches, web publishing and email as well as software development. MUSIC was marketed by IBM mainly to educational institutions as a cost-effective operating system for its hardware, and eventually became an IBM Systems Product (MUSIC/SP or Multi-User System for Interactive Computing / System Product) in 1985. The last official version was released in 1999. ORVYL and WYLBUR were developed by Stanford University in 1967-68 for the IBM S/360-67. They provided some of the first time-sharing capabilities on IBM S/360 computers. System/360 operating systems Up to the early 1960s, IBM's low-end and high-end systems were incompatible, so programs could not easily be transferred from one to another, and the systems often used completely different peripherals such as disk drives. IBM concluded that these factors were increasing its design and production costs for both hardware and software to a level that was unsustainable, and were reducing sales by deterring customers from upgrading. So in 1964, the company announced System/360, a new range of computers which all used the same peripherals and most of which could run the same programs. IBM originally intended that System/360 should have only one batch-oriented operating system, OS/360. There are at least two accounts of why IBM later decided it should also produce a simpler batch-oriented operating system, DOS/360: because it found that OS/360 would not fit into the limited memory available on the smaller System/360 models; or because it realized that the development of OS/360 would take much longer than expected, and introduced DOS/360 as one of a series of stop-gaps to prevent System/360 hardware sales from collapsingthe others were BOS/360 (Basic Operating System, for the smallest machines) and TOS/360 (Tape Operating System, for machines with only tape drives). System/360's operating systems were more complex than previous IBM operating systems for several reasons, including: They had to support multiprogrammingswitching to run another in-progress application when the current application was blocked waiting for I/O operations (such as disk reads) to complete. Without multiprogramming, the faster CPUs in the range would have spent most of their time idle, waiting for slow I/O operations. Hence, the operating systems had to be the real masters of the systems, to provide whatever services the applications validly requested, and to handle crashes or misbehavior in one application without stopping others that were running at the same time. They had to support a much wider range of machine sizes. Memory ranged from 16 KB to 1 MB and processor speeds from a few thousand instructions per second to 500,000. They had to support a wide range of application requirements. For example, some applications only needed to read through sequential files from start to finish; others needed fast, direct access to specific records in very large files; and a few applications spent nearly all their time doing calculations, with very little reading or writing of files. This made the development of OS/360 and other System/360 software one of the largest software projects anyone had attempted, and IBM soon ran into trouble, with huge time and cost overruns and large numbers of bugs. These problems were only magnified because to develop and test System/360 operating systems on real hardware, IBM first had to develop Basic Programming Support/360 (BPS/360). BPS was used to develop the tools needed to develop DOS/360 and OS/360, as well as the first versions of tools it would supply with these operating systemscompilers for FORTRAN and COBOL, utilities including Sort, and above all the assembler it needed to build all the other software. IBM's competitors took advantage of the delays in OS/360 and the System/360 to announce systems aimed at what they thought were the most vulnerable parts of IBM's market. To prevent sales of System/360 from collapsing, IBM released four stop-gap operating systems: Basic Operating System/360 (BOS/360), which loaded from a disk drive or tape drive and supported tape drives and a few disks. This system was supplied to beta test customers and may have been an early version of DOS/360. TOS/360, which was designed to provide an upgrade path for customers who had IBM 1401 computers with tape drives and no disks. DOS/360, which was built by the developers of BOS/360 and TOS/360 (IBM's small business computers division) and went on to become a mainstream operating system whose descendant z/VSE is still widely used. Operating System/360 (OS/360) with only the Primary Control Program (PCP) option, which didn't support multiprogramming. When IBM announced the S/360-67 it also announced a timesharing operating system, TSS/360, that would use the new virtual memory capabilities of the 360/67. TSS/360 was late and early releases were slow and unreliable. By this time the alternative operating system CP-67, developed by IBM's Cambridge Scientific Center, was running well enough for IBM to offer it "without warranty" as a timesharing facility for a few large customers. CP-67 would go on to become VM/370 and eventually z/VM. IBM ultimately offered three releases of a TSS/370 PRPQ as a migration path for its TSS/360 customers, and then dropped it. The traumas of producing the System/360 operating systems gave a boost to the emerging discipline of software engineering, the attempt to apply scientific principles to the development of software, and the management of software projects. Frederick P. Brooks, who was a senior project manager for the whole System/360 project and then was given specific responsibility for OS/360 (which was already long overdue), wrote an acclaimed book, The Mythical Man-Month, based on the problems encountered and lessons learned during the project, two of which were: Throwing additional resources (especially staff) at a struggling project quickly becomes unproductive or even counter-productive because of communication difficulties. This is the "Mythical Man-Month" syndrome which gave the book its title. The successor to a successful system often runs into difficulties because it gets overloaded with all the features people wished had been in the earlier system. Brooks called this the "second-system effect", and cited OS/360 as a very comprehensive example. DOS/360 While OS/360 was the preferred operating system for the higher-end System/360 machines, DOS/360 was the usual operating system for the less powerful machines. It provided a set of utility programs, a macro assembler, and compilers for FORTRAN and COBOL. Support for RPG came later, and eventually a PL/I subset. And it supported a useful range of file organizations with access methods to help in using them: Sequential data sets were normally read one record at a time from beginning to end. In indexed (ISAM) files a specified section of each record was defined as a key that could be used to look up specific records. In direct access (BDAM) files, the application program had to specify the physical location on the disk of the data it wanted to access. BDAM programming was not easy and most customers never used it themselves, but it was the fastest way to access data on disks and many software companies used it in their products, especially database management systems such as ADABAS, IDMS and IBM's DL/I. Sequential and ISAM files could store either fixed-length or variable-length records, and all types could occupy more than one disk volume. DOS/360 also offered BTAM, a data communications facility that was primitive and hard to use by today's standards. But BTAM could communicate with almost any type of terminal, which was a big advantage at a time when there was hardly any standardization of communications protocols. But DOS/360 had significant limitations compared with OS/360, which was used to control most larger System/360 machines: The first version could run only one program at a time. A later enhancement allowed 3 at the same time, in one of 3 "partitions" whose size was set by each customer when DOS/360 was installed. The JCL it used for submitting jobs was designed to be easy for the low-end machines to process, and as a result, programmers did not find it easy to read or write. There was no spooling sub-system to improve the efficiency of punched card and printer use. In the late 1960s, an independent software company started selling a spooler called GRASP. DOS/360 had no relocating loader, so users had to link edit a separate executable version of each program for each partition in which the program was likely to be run. Executable programs were stored in the Core Image Library, which did not reclaim space when programs were deleted or replaced by newer versions. When the Core Image Library became full, it had to be compressed by one of the utility programs, and this could halt development work for as much as half a day. Its application programming interface was different from that of OS/360. DOS/360 programs written in high level languages such as COBOL needed small modifications before they could be used with OS/360 and assembly language programs needed larger changes. IBM expected that DOS/360 users would soon upgrade to OS/360, but despite its limitations, DOS/360 became the world's most widely used operating system because: System/360 hardware sold very well Over 90% of the 360 systems sold were Models 20, 30 & 40 Most of these cheaper models had far less core memory than required by OS/360. DOS/360 ran well on the System/360 processors which medium-sized organizations could afford, and it was better than the "operating systems" these customers had before. As a result, its descendant z/VSE is still widely used today, as of 2005. OS/360 OS/360 included multiple levels of support, a single API, and much shared code. PCP was a stop-gap version that could run only one program at a time, but MFT ("Multiprogramming with a Fixed number of Tasks") and MVT ("Multiprogramming with a Variable number of Tasks") were used until at least the late 1970s, a good five years after their successors had been launched. It is unclear whether the divisions among PCP, MFT and MVT arose because MVT required too much memory to be usable on mid-range machines or because IBM needed to release a multiprogramming version of OS (MFT) as soon as possible. PCP, MFT, and MVT had different approaches to managing memory (see below), but provided very similar facilities: The same application programming interface (API), so application programs could be transferred among PCP, MFT, and MVT without even needing re-compilation. The same JCL, which was more flexible and easier to use than that of DOS/360. The same facilities (access methods) as DOS/360 for reading and writing files (sequential, indexed, and direct) and for data communications (BTAM). An additional file structure, partitioned, and access method (BPAM), which was mainly used for managing program libraries. Although partitioned files needed to be compressed to reclaim free space, this seldom halted development work as it did with DOS/360's Core Image Library, because PCP, MFT, and MVT allowed an indefinite number of partitioned files, and each project generally had at least one. A file naming system allowing files to be managed as hierarchies, such as PROJECT.USER.FILENAME. A spooling facility (which DOS/360 lacked). Applications could create sub-tasks, which allowed multiprogramming within the one job. Experience indicated that it was not advisable to install OS/360 on systems with less than 256 KB of memory, which was a common limitation in the 1960s. MFT When installing MFT, customers would specify up to four partitions of memory with fixed boundaries, in which application programs could be run simultaneously. MFT Version II (MFT-II) raised the limit to 52. MVT MVT was considerably larger and more complex than MFT and therefore was used on the most powerful System/360 CPUs. It treated all memory not used by the operating system as a single pool from which contiguous "regions" could be allocated as required by an indefinite number of simultaneous application programs. This scheme was more flexible than MFT's and in principle used memory more efficiently, but was liable to fragmentationafter a while one could find that, although there was enough spare memory in total to run a program, it was divided into separate chunks none of which was large enough. In 1971 the Time Sharing Option (TSO) for use with MVT was added. TSO became widely used for program development because it provided: an editor, debuggers for some of the programming languages used on System/360, and the ability to submit batch jobs, be notified of their completion, and view the results without waiting for printed reports. TSO communicated with terminals by using TCAM (Telecommunications Access Method), which eventually replaced the earlier Queued Telecommunications Access Method (QTAM). TCAM's name suggests that IBM hoped it would become the standard access method for data communications, but in fact, TCAM was used almost entirely for TSO and was largely superseded by VTAM from the late 1970s onwards. TP monitors System/360's hardware and operating systems were designed for processing batch jobs which in extreme cases might run for hours. As a result, they were unsuitable for transaction processing, in which there are thousands of units of work per day and each takes between 30 seconds and a very few minutes. In 1968 IBM released IMS to handle transaction processing, and in 1969 it released CICS, a simpler transaction processing system which a group of IBM's staff had developed for a customer. IMS was only available for OS/360 and its successors, but CICS was also available for DOS/360 and its successors. For many years this type of product was known as a "TP (teleprocessing) monitor". Strictly speaking TP monitors were not operating system components but application programs which managed other application programs. In the 1970s and 1980s, several third-party TP monitors competed with CICS (notably Taskmaster, COM-PLETE, Shadow, and Intercomm), but IBM gradually improved CICS to the point where most customers abandoned the alternatives. Special systems for airlines In the 1950s airlines were expanding rapidly but this growth was held back by the difficulty of handling thousands of bookings manually (using card files). In 1957 IBM signed a development contract with American Airlines for the development of a computerized reservations system, which became known as SABRE. The first experimental system went live in 1960 and the system took over all booking functions in 1964in both cases using IBM 7090 mainframes. In the early 1960s IBM undertook similar projects for other airlines and soon decided to produce a single standard booking system, PARS, to run on System/360 computers. In SABRE and early versions of PARS there was no separation between the application and operating system components of the software, but in 1968 IBM divided it into PARS (application) and ACP (operating system). Later versions of ACP were named ACP / TPF and then TPF (Transaction Processing Facility) as non-airline businesses adopted this operating system for handling large volumes of online transactions. The latest version is z/TPF. IBM developed ACP and its successors because: in the mid-1960s IBM's standard operating systems (DOS/360 and OS/360) were batch-oriented and could not handle large numbers of short transactions quickly enough; even its transaction monitors IMS and CICS, which run under the control of standard general-purpose operating systems, are not fast enough for handling reservations on hundreds of flights from thousands of travel agents. The last "public domain" version of ACP, hence its last "free" version, was ACP 9.2, which was distributed on a single mini-reel with an accompanying manual set (about two dozen manuals, which occupied perhaps 48 lineal inches of shelf space) and which could be restored to IBM 3340 disk drives and which would, thereby, provide a fully functional ACP system. ACP 9.2 was intended, primarily, for bank cards like MasterCard and other financial applications, but it could also be utilized for airline reservation systems, too, as by this time ACP had become a more general-purpose OS. ACP had by then incorporated a hypervisor module (CHYR) which supported a virtual OS (usually VS1, but possibly also VS2) as a guest, with which program development or file maintenance could be accomplished concurrently with the online functions. In some instances, production work was run under VS2 under the hypervisor, including, possibly, IMS DB. System/360 Model 20 The Model 20 was labeled as part of the System/360 range because it could be connected to some of the same peripherals, but it was a 16-bit machine and not entirely program-compatible with other members of the System/360 range. Three operating systems were developed by IBM's labs in Germany, for different 360/20 configurations; DPS—with disks (minimum memory required: 12 KB); TPS—no disk but with tapes (minimum memory required: 8 KB); and CPS—punched-card-based (minimum memory required: 4 KB). These had no direct successors since IBM introduced the System/3 range of small business computers in 1969 and System/3 had a different internal design from the 360/20 and different peripherals from IBM's mainframes. System/360 Model 44 This was another processor that used the System/360 peripherals but had a modified instruction set. The 360/44 was designed for scientific computation using floating point numbers, such as geological or meteorological analyses. Because of the internal differences and the specialized type of work for which it was designed, the 360/44 had its own operating system, PS/44. An optional feature allows a System/360 emulator to run in hidden storage and implement the missing instructions in order to run OS/360. The 360/44 and PS/44 had no direct successors. System/370 and virtual memory operating systems When System/370 was announced in 1970 it offered essentially the same facilities as System/360 but with about 4 times the processor speeds of similarly-priced System/360 CPUs. Then in 1972 IBM announced "System/370 Advanced Functions", of which the main item was that future sales of System/370 would include virtual memory capability and this could also be retro-fitted to existing System/370 CPUs. Hence IBM also committed to delivering enhanced operating systems which could support the use of virtual memory. Most of the new operating systems were distinguished from their predecessors by the presence of "/VS" in their names. "VS" stands for "Virtual Storage"IBM avoided the term "virtual memory", allegedly because the word "memory" might be interpreted to imply that IBM computers could forget things. All of today's IBM mainframe operating systems except z/TPF are descendants of those included in the "System/370 Advanced Functions" announcementz/TPF is a descendant of ACP, the system which IBM initially developed to support high-volume airline reservations applications. DOS/VS DOS/VS was the successor to DOS/360, and offered similar facilities, with the addition of virtual memory. In addition to virtual memory DOS/VS provided other enhancements: Five memory partitions instead of three. Later releases increased this to seven. A relocating loader, so that it was no longer necessary to link-edit a separate copy of each program for each partition in which it was to run. An improved spooling component, POWER/VS. DOS/VS was followed by significant upgrades: DOS/VSE and VSE/SP (1980s), VSE/ESA (1991), and z/VSE (2005). OS/VS1 OS/VS1 was the successor to MFT, and offered similar facilities, with the addition of virtual memory. IBM released fairly minor enhancements of OS/VS1 until 1983, and in 1984 announced that there would be no more. OS/VS1 and TSS/370 are the only IBM System/370 operating systems that do not have modern descendants. The Special Real Time Operating System (SRTOS), Programming RPQ Z06751, was a variant of OS/VS1 extended to support real-time computing. It was targeted at such industries as electric utility energy management and oil refinery applications. OS/VS2 and MVS OS/VS2 Release 1 (SVS) was a replacement for MVT with virtual memory; while there were many changes it retained the overall structure. But in 1974 IBM released what it described as OS/VS2 Release 2 but which was a major rewrite that was upwards-compatible with the earlier OS/VS2 SVS. The new system's most noticeable feature was that it supported multiple virtual address spacesdifferent applications thought they were using the same range of virtual addresses, but the new system's virtual memory facilities mapped these to different ranges of real memory addresses. As a result, the new system rapidly became known as "MVS" (Multiple Virtual Storages), the original OS/VS2 became known as "SVS" (Single Virtual Storage). IBM itself accepted this terminology and labelled MVS's successors "MVS/...". The other distinctive features of MVS were: its main catalog had to be a VSAM catalog; it supported "tightly-coupled multiprocessing" (2 or more CPUs share the same memory and copy of the operating system); it included a System Resources Manager (renamed Workload Manager in later versions) which allowed users to load additional work on to the system without reducing the performance of high-priority jobs. IBM has released several MVS upgrades: MVS/SE, MVS/SP Version 1, MVS/XA (1981), MVS/ESA (1985), OS/390 (1996) and currently z/OS (2001). VM/370 VM/370 combined a virtual machine facility with a single-user system called Conversational Monitor System (CMS); this combination provided time-sharing by allowing each user to run a copy of CMS on his / her own virtual machine. This combination was a direct descendant of CP/CMS. The virtual machine facility was often used for testing new software while normal production work continued on another virtual machine, and the CMS timesharing system was widely used for program development. VM/370 was followed by a series of upgrades: VM/SEPP ("Systems Extensions Program Product"), VM/BSEPP ("Basic Systems Extensions Program Product"), VM/SP (System Product), VM/SP HPO ("High Performance Option"), VM/XA MA ("Extended Architecture Migration Aid"), VM/XA SF ("Extended Architecture System Facility"), VM/XA SP ("Extended Architecture System Product"), VM/ESA ("Enterprise Systems Architecture"), and z/VM. IBM also produced optional microcode assists for VM and successors, to speed up the hypervisor's emulation of privileged instructions (those which only operating systems can use) on behalf of "guest" operating systems. As part of 370/Extended Architecture, IBM added the Start Interpretive Execution (SIE) instruction to allow a further speedup of the CP hypervisor. Technical notes Time-sharing Time-sharing (or timesharing) is based on the idea that computers are much faster than humans, so while one human user is reading what a computer has just displayed on a screen the computer can do some useful work for another user. Large time-sharing systems can have hundreds or even thousands of simultaneous users, and the memory required by their programs and data generally adds up to much more than the physical memory attached to the computer. Time-sharing systems solve this problem by various combinations of: virtual memory, described below. swapping: when the OS is waiting for a response from one user, a time slice has ended or the OS is trying to free up real storage, it may save a user's programs and data on a disk or drum and read them back into memory when the user sends a response, resources free up or another user is swapped out due to time slice end. Swapping does not require virtual memory; it was implemented on OS/360 without virtual memory. It transfers all of a user's programs and data between memory and disk/drum and is mainly driven by the user's responses to information displayed by the system. Virtual memory Virtual memory is a memory management technique by which programs are made to work as if they have more memory available to them than is actually attached to the computer. Running programs' code and data may be scattered over several areas of physical memory or even placed on a disk/drum until needed. The main components of an IBM virtual memory system are: Virtual memory, consisting of all memory addresses accessible by the CPU hardware. Virtual memory is an abstraction, so systems can easily have more virtual than real memory. Pages, fixed-size blocks into which all virtual memory is divided. Most IBM operating systems use 4 KB (4,096-byte) pages, although some older systems ran quite well with 2 KB (2,048-byte) pages. Newer IBM System z systems also support 1 MB large pages in addition to the normal 4 KB pages. Real memory, random-access memory (RAM) attached to the computing system. Page frames, realized by dividing all real memory into pieces equal to the system's page size. Virtual-memory pages must be placed into real-memory page frames before they can be used by the CPU and I/O channels. Page Tables track the location of every virtual-memory page, whether in a real-memory page frame or on disk/drum, in a paging file. Critical to memory management, Page Table entries also record the last time each page was accessed. Dynamic Address Translation hardware (sometimes called a "DAT box" in early systems because of its separate enclosure) is integrated into the CPU itself and participates in every memory reference. If the Page Table shows the page in a real-memory page frame, DAT translates the virtual address to a real one and allows the memory access to complete. If, on the other hand, the referenced page is not in real memory, the DAT hardware generates an interrupt (internal signal) which calls the Paging Supervisor into action. The Paging Supervisor (part of the operating system) manages all memory, both real and virtual, moving pages between real memory and disk/drum as needed, keeping the Page Table updated, servicing memory allocation requests, and cleaning up after itself. As the load on the system increases, a page can be referenced when all page frames are in use. When this happens, the paging supervisor typically identifies the page that has not been read or written for the longest interval of time (least-recently-used), copies the page to the paging file (on disk or drum), updates the Page Table, and uses the newly available page frame to satisfy the memory request. When functioning properly, the virtual memory system keeps active pages in real memory, inactive ones on disk/drum, and allows more efficient execution of the system's workload. Virtual machine Virtual machine techniques enable several operating systems ("guest" operating systems) or other software to run on the same computer so that each thinks it has a whole computer to itself, and each of these simulated whole computers is called a "virtual machine". The operating system which really controls the computer is usually called a hypervisor. Two of the major components of the hypervisor are: Virtual memory management. Each virtual machine appears to have a complete range of addresses from 0 to some large number, and virtual memory techniques prevent different virtual machines from confusing each other. Simulating "privileged" functions on behalf of the "guest" operating systems. "Privileged" functions are those which enable programs to take over all or at least large parts of the computer, and usually operating systems immediately terminate any other program which tries to use them. But "guest" operating systems think they are entitled to use these functions, so the hypervisor detects their attempts to do so and runs the privileged functions on their behalf, using virtual memory techniques to prevent them from corrupting memory areas used by other "guest" operating systems. See also IBM mainframe History of operating systems Timeline of operating systems Notes References Further reading Brooks, Jr., Frederick P. (1975). "The Mythical Man-Month: Essays on Software Engineering", Addison-Wesley. . (Reprinted with corrections, January 1982) IBM mainframe operating systems: Timeline and Brief Explanation For the IBM System/360 and Beyond, Dave Morton. A wiki dedicated to IBM Mainframe Computers IBM mainframe operating systems

Operating System (OS)

Open Platform Management Architecture Open Platform Management Architecture (OPMA) is an open, royalty free standard for connecting a modular, platform hardware management subsystem (an "mCard") to a computer motherboard. Platform hardware management generally refers to the remote monitoring of platform hardware variables such as fan speed, voltages, CPU and enclosure temperatures along with a wide range of other sensors. It also implies the ability to remotely control the power state of the platform and to reset the system back into an operational state should it "hang". A significant advantage of OPMA over previous generation management subsystem attachment methods is that OPMA does not consume a PCI socket. OPMA cards are also smaller and lower cost than their PCI predecessors. The OPMA specification, which can be freely downloaded from the web, specifies a signal list, connector and pin out, power requirements, mechanical form factor, BIOS and management controller firmware interfaces, and a detailed division of management subsystem resources between the motherboard and the mCard. OPMA enables a wide variety of mCards to individually interface to a given motherboard. It also enables a single mCard to individually interface to multiple motherboard models. OPMA is mainly targeted at server platforms where the cost of a card based management subsystem is more easily borne, but high end workstations may also leverage the specification to handle cases where remote workstation platform management is required. The OPMA interface is flexible enough to handle multiple mCard price points and capabilities ranging from basic IPMI based management to those that support KVMoIP, remote virtual media, and newer external interface standards that require a larger on-card resource footprint such as WS-Management. OPMA supports two basic management subsystem connection paradigms. The first is where virtually the entire management subsystem resides on the mCard. Using this paradigm, the platform contains no basic management controller of any sort and relies on the presence of an OPMA card for all remote hardware management capabilities. In the second paradigm, the basic management module is soldered to the motherboard and the OPMA connector is used as an upgrade path for advanced platform management features. In this case, which is known as "upgrade kit mode", the OPMA card is able to access all sensors supported by the soldered down management controller using an SMBus link over which the Intelligent Platform Management Bus (IPMB) protocol is employed. OPMA also leverages the Intelligent Platform Management Interface (IPMI) specification in order to provide a basic plug and play capability. Using IPMI-defined OEM command extensions, the system and the mCard exchange basic information during system boot such as mCard/motherboard make and model, specification version compliance, and optional capabilities defined by the OPMA specification. History OPMA was created as a joint technology development effort between AMD and various platform management subsystem technology companies such as Agilent, AMI, Avocent, and Raritan Embedded Solutions (formerly called Peppercon). When OPMA was first released in February 2005, platform hardware management was being treated as a value added feature by OEMs. This resulted in a constant redesign of the management card infrastructure such that no two motherboard manufacturers could use the same card. Lack of standards and constant redesign resulted in higher end user costs. While PCI based management cards were available which could be plugged into a variety of platforms, the PCI bus did not provide direct access to all of the sensors needed to manage the hardware aspects of a platform. To gain full sensor access, custom headers had to be added to motherboards. Custom cables then linked these sideband signals between the card and the motherboard. PCI based platform management cards also consume a PCI slot which is a premium resource for many servers. This is especially true of those using the 1U rack format and those which need PCI slots for RAID interface cards that enhance system hard disk throughput. AMD engineering teams were internally tasked with building server reference designs to support Opteron server processor evaluation by customers. During these early internal server design efforts it was determined that a standard management card subsystem that was reusable across many platforms would decrease time to market while saving design and support costs for AMD reference design platforms in the field. Such an interface would also allow AMD to outsource the design and test of the management card to industry experts. AMD reasoned that external audiences would derive these same benefits as its internal engineering teams and so OPMA was documented and released. Adoption According to AMD's press releases, there has been significant interest in OPMA by the server industry platform and infrastructure providers. Some of the motherboards may be seen using links in the external links section. To date, no tier one computer OEMs have offered OPMA enabled motherboards for sale. External links OPMA enabled channel motherboards http://www.tyan.com/product_board_spec.aspx?pid=157 OPMA mcards http://www.ami.com/news/meganews/mn6-08.pdf http://www.raritan.com/_downloads/pdfs/products/sa_opma-m3-g4_02en_datasheet.pdf http://www.aten.com/products/productItem.php?pcid=20061106173036003&psid=20061106173448002&pid=2006110617367007&layerid=subClass7 http://www.arima.com.tw/server/Product/ViewProduct.asp?View=Arima%20Aquarius http://www.arima.com.tw/server/Product/ViewProduct.asp?View=Arima%20Scorpio2 http://www.coreipm.com: coreIPM Project: Free & Open Source firmware for OPMA mcards Standards http://www.intel.com/design/servers/ipmi http://www.intel.com/technology/manage/downloads/ws_management.pdf SIG http://www.opma-sig.org Computer hardware standards System administration Out-of-band management

Operating System (OS)

MenuetOS MenuetOS is an operating system with a monolithic preemptive, real-time kernel written in FASM assembly language. The system also includes video drivers. It runs on 64-bit and 32-bit x86 architecture computers. Its author is Ville M. Turjanmaa. It has a graphical desktop, games, and networking abilities (TCP/IP stack). One distinctive feature is that it fits on one floppy disk. On an Intel Pentium MMX it has been known to boot in . History 32 bit MenuetOS was originally written for 32-bit x86 architectures and released under the GPL-2.0-only license, thus many of its applications are distributed under the GPL. 64 bit The 64-bit MenuetOS often referred to as Menuet 64, remains a platform for learning 64-bit assembly language programming. The 64-bit Menuet is distributed without charge for personal and educational use only, but without the source code, and the license includes a clause that prohibits disassembly. Multi-core support was added on 24 Feb 2010. Features MenuetOS development has focused on fast, simple, efficient implementation. MenuetOS has networking abilities, and a working TCP/IP stack. Most of the networking code is written by Mike Hibbett. The main focus of Menuet has been on making an environment for easy assembly programming, but it is still possible to run software written in high-level programming languages on the assembler core. The biggest single effort towards high-level language support is Jarek Pelczar's work in porting C libraries to Menuet. The GUI at version 0.99 supports display resolutions up to (16 million colours) with window transparency. The OS has support for several classes of USB 2.0 peripherals. MenuetOS ships with the shareware versions of Quake and Doom. For disk access, MenuetOS supports the FAT32 file system. Write support is only possible to USB connected devices. Distributions 32-bit Menuet32 GridWorks "EZ" distribution (comprehensive 32-bit archive packages) (CD/HD Boots) 64-bit The 64-bit main distribution is now proprietary. Several distributions of the 32-bit GPL MenuetOS still exist, including translations in Russian, Chinese, Czech, and Serbian. Menuet64 See also KolibriOS - A free fork of MenuetOS 32-bit References David Chisnall (Jun 22, 2007) A Roundup of Free Operating Systems. MenuetOS, informIT MenuetOS - 32bit-Betriebssystem auf einer Floppy, Der Standard, 12 May 2003 Eugenia Loli-Queru (5 Sep 2001) Interview With Ville Turjanmaa, the Creator of MenuetOS, OSNews Ville M. Turjanmaa (December 1, 2001) The Menuet Operating System. Packing a lot of punch into a small package, Dr. Dobb's External links MenuetOS homepage (Menuet64 oriented) MenuetOS C Library MenuetOS compared to AtheOS and SkyOS (2002) an interview with Ville Turjanmaa and Madis Kalme, two of the MenuetOS developers (2009) Floppy disk-based operating systems X86-64 operating systems Assembly language software Proprietary operating systems Hobbyist operating systems

Operating System (OS)

UniFLEX UniFLEX is a Unix-like operating system developed by Technical Systems Consultants (TSC) for the Motorola 6809 family which allowed multitasking and multiprocessing. It was released for DMA-capable 8" floppy, extended memory addressing hardware (software controlled 4KiB paging of up to 768 KiB RAM), Motorola 6809 based computers. Examples included machines from SWTPC, GIMIX and Goupil (France). On SWTPC machines, UniFLEX also supported a 20 MB, 14" hard drive (OEM'd from Century Data Systems) in 1979. Later on, it also supported larger 14" drives (up to 80 MB), 8" hard drives, and 5-1/4" floppies. In 1982 other machines also supported the first widely available 5-1/4" hard disks using the ST506 interface such as the 5 MB BASF 6182 and the removable SyQuest SQ306RD of the same capacity. Due to the limited address space of the 6809 (64 kB) and hardware limitations, the main memory space for the UniFLEX kernel as well as for any running process had to be smaller than 56 kB (code + data)(processes could be up to 64K minus 512 bytes). This was achieved by writing the kernel and most user space code entirely in assembly language, and by removing a few classic Unix features, such as group permissions for files. Otherwise, UniFLEX was very similar to Unix Version 7, though some command names were slightly different. There was no technical reason for the renaming apart from achieving some level of command-level compatibility with its single-user sibling FLEX. By simply restoring the Unix style names, a considerable degree of "Unix Look & Feel" could be established, though due to memory limitations the command line interpreter (shell) was less capable than the Bourne Shell known from Unix Version 7. Memory management included swapping to a dedicated portion of the system disk (even on floppies) but only whole processes could be swapped in and out, not individual pages. This caused swapping to be a very big hit on system responsiveness, so memory had to be sized appropriately. However UniFLEX was an extremely memory-efficient operating system. Machines with less than a megabyte of RAM serving a dozen asynchronous terminals were not uncommon and worked surprisingly well. TSC never bundled a C compiler with UniFLEX for the 6809, though they produced one. But in the early 1980s a C language implementation became available as a 3rd party products (the "McCosh" and "Introl" compilers). Using such a C compiler could establish source-level compatibility with Unix Version 7, i.e., a number of Unix tools and applications could be ported to UniFLEX - if size allowed: Unix on a PDP-11 limited executables to 64 kB of code and another 64 kB of data, while the UniFLEX limitation was approximately 56 kB for both, code and data together. Not much application software was available for UniFLEX. Ports of the Dynacalc spreadsheet and the Stylograph word processor from the FLEX operating system existed but only very few copies were sold. In the mid 1980s a successor version for the Motorola 68000 was announced. Though it removed the pressing space limitations, it was not commercially successful because it had to compete with source-code ports of original Unix. The source code for UniFLEX and supporting software is available on the Internet. In the Netherlands, UniFLEX users ported a fair number of Unix utilities to UniFLEX. Also they modified some kernel code that give foreground processes preference over background processes accessing disk and that gave a major improvement in user experience. One of the TSC guys, Dan Vanada, later started his company "Scintillex Software". Its products were, for example, utilities that allowed transfer of data between UniFLEX and MS-DOS and vice versa, as well DOS format utilities, and a code patch utility. See also OS-9 References External links The Missing 6809 UniFLEX Archive A UniFLEX compatible system on Eurocards Unix variants Assembly language software Discontinued operating systems

Operating System (OS)

Operations execution system An operations execution system (OES, also called manufacturing process management and collaborative manufacturing) is a suite of manufacturing systems designed to execute operations tasks, such as production, maintenance or inventory tracking. Manufacturing execution systems (MES) are a subset of an operations execution system, as they are typically concerned with executing tasks within just the production line. Other systems which might be included within an OES might include warehouse management system (WMS), supply chain management systems (SCM) or computerized maintenance management system (CMMS). Large, global enterprises invoking a quality management program impacting operations systems seek integrated systems to ease the deployment of such a program. For one reason, quality assurance programs cover many areas of manufacturing, including the processes that intersect each of these activities. By collaborating across operations processes, between different functions and departments, a higher performance operations model emerges, one that optimizes manufacturing output, leading to better quality products produced more cost effectively, so as to better compete globally. See also ANSI/ISA-95 about "Manufacturing Operations Management". This standard also extend the MES reference beyond Production activities to cover also Quality, Maintenance and Inventory. See also Manufacturing operations management Manufacturing

Operating System (OS)

System administrator A system administrator, or sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as servers. The system administrator seeks to ensure that the uptime, performance, resources, and security of the computers they manage meet the needs of the users, without exceeding a set budget when doing so. To meet these needs, a system administrator may acquire, install, or upgrade computer components and software; provide routine automation; maintain security policies; troubleshoot; train or supervise staff; or offer technical support for projects. Related fields Many organizations staff offer jobs related to system administration. In a larger company, these may all be separate positions within a computer support or Information Services (IS) department. In a smaller group they may be shared by a few sysadmins, or even a single person. A database administrator (DBA) maintains a database system, and is responsible for the integrity of the data and the efficiency and performance of the system. A network administrator maintains network infrastructure such as switches and routers, and diagnoses problems with these or with the behavior of network-attached computers. A security administrator is a specialist in computer and network security, including the administration of security devices such as firewalls, as well as consulting on general security measures. A web administrator maintains web server services (such as Apache or IIS) that allow for internal or external access to web sites. Tasks include managing multiple sites, administering security, and configuring necessary components and software. Responsibilities may also include software change management. A computer operator performs routine maintenance and upkeep, such as changing backup tapes or replacing failed drives in a redundant array of independent disks (RAID). Such tasks usually require physical presence in the room with the computer, and while less skilled than sysadmin tasks, may require a similar level of trust, since the operator has access to possibly sensitive data. An SRE Site Reliability Engineer - takes a software engineering or programmatic approach to managing systems. Training Most employers require a bachelor's degree in a related field, such as computer science, information technology, electronics engineering, or computer engineering. Some schools also offer undergraduate degrees and graduate programs in system administration. In addition, because of the practical nature of system administration and the easy availability of open-source server software, many system administrators enter the field self-taught. Generally, a prospective employee will be required to have experience with the computer system they are expected to manage. In most cases, candidates are expected to possess industry certifications such as the Microsoft MCSA, MCSE, MCITP, Red Hat RHCE, Novell CNA, CNE, Cisco CCNA or CompTIA's A+ or Network+, Sun Certified SCNA, Linux Professional Institute, Linux Foundation Certified Engineer or Linux Foundation Certified System Administrator, among others. Sometimes, almost exclusively in smaller sites, the role of system administrator may be given to a skilled user in addition to or in replacement of his or her duties. Skills The subject matter of system administration includes computer systems and the ways people use them in an organization. This entails a knowledge of operating systems and applications, as well as hardware and software troubleshooting, but also knowledge of the purposes for which people in the organization use the computers. Perhaps the most important skill for a system administrator is problem solving—frequently under various sorts of constraints and stress. The sysadmin is on call when a computer system goes down or malfunctions, and must be able to quickly and correctly diagnose what is wrong and how best to fix it. They may also need to have teamwork and communication skills; as well as being able to install and configure hardware and software. Sysadmins must understand the behavior of software in order to deploy it and to troubleshoot problems, and generally know several programming languages used for scripting or automation of routine tasks. A typical sysadmin's role is not to design or write new application software but when they are responsible for automating system or application configuration with various configuration management tools, the lines somewhat blur. Depending on the sysadmin's role and skillset they may be expected to understand equivalent key/core concepts a software engineer understands. That said, system administrators are not software engineers or developers, in the job title sense. Particularly when dealing with Internet-facing or business-critical systems, a sysadmin must have a strong grasp of computer security. This includes not merely deploying software patches, but also preventing break-ins and other security problems with preventive measures. In some organizations, computer security administration is a separate role responsible for overall security and the upkeep of firewalls and intrusion detection systems, but all sysadmins are generally responsible for the security of computer systems. Duties A system administrator's responsibilities might include: Analyzing system logs and identifying potential issues with computer systems. Applying operating system updates, patches, and configuration changes. Installing and configuring new hardware and software. Adding, removing, or updating user account information, resetting passwords, etc. Answering technical queries and assisting users. Responsibility for security. Responsibility for documenting the configuration of the system. Troubleshooting any reported problems. System performance tuning. Ensuring that the network infrastructure is up and running. Configuring, adding, and deleting file systems. Ensuring parity between dev, test and production environments. Training users Plan and manage the machine room environment In larger organizations, some of the tasks above may be divided among different system administrators or members of different organizational groups. For example, a dedicated individual(s) may apply all system upgrades, a Quality Assurance (QA) team may perform testing and validation, and one or more technical writers may be responsible for all technical documentation written for a company. System administrators, in larger organizations, tend not to be systems architects, systems engineers, or systems designers. In smaller organizations, the system administrator might also act as technical support, Database Administrator, Network Administrator, Storage (SAN) Administrator or application analyst. See also Application service management Bastard Operator From Hell (BOFH) DevOps Forum administrator Information technology operations League of Professional System Administrators LISA (organization) Professional certification (computer technology) Superuser Sysop System Administrator Appreciation Day References Further reading Essential Linux Administration: A Comprehensive Guide for Beginners, by Chuck Easttom (Cengage Press, 2011) Essential System Administration (O'Reilly), 3rd Edition, 2001, by Æleen Frisch The Practice of System and Network Administration (Addison-Wesley), 2nd Edition 5 Jul. 2007, by Thomas A. Limoncelli, Christine Hogan and Strata R. Chalup The Practice of System and Network Administration Volume 1: DevOps and other Best Practices for Enterprise IT (Addison-Wesley), 3rd Edition. 4 Nov. 2016, by Thomas A. Limoncelli, Christine Hogan, Strata R. Chalup The Practice of Cloud System Administration: Designing and Operating Large Distributed Systems, Volume 2 (Addison-Wesley), 2 Sep. 2014, by Thomas A. Limoncelli, Christine Hogan, Strata R. Chalup Principles of Network and System Administration (J. Wiley & Sons), 2000, 2003 (2nd ed.), by Mark Burgess Time Management for System Administrators (O'Reilly), 2005, by Thomas A. Limoncelli UNIX and Linux System Administration Handbook (Prentice Hall), 5th edition, 8 Aug. 2017, by Trent R. Hein, Ben Whaley, Dan Mackin, Sandeep Negi "The blue collar workers of the 21st century", Minnesota Public Radio, 27 January 2004 External links Communication Workers of America Computer occupations Computer systems

Operating System (OS)

IDEDOS IDEDOS is a ROM-based disk operating system written in 6502/65816 assembly language for the Commodore 64, 128 and SuperCPU. Its main purpose is to control ATA(PI) devices connected to an IDE64 cartridge and present them like normal Commodore drives. Additionally it supports networked drives (PCLink) and has a built-in machine code monitor and file manager. Architecture The C64 KERNAL uses a vector table at page 3 to allow redirection of common kernal file handling and basic functions. This feature is used by IDEDOS to hook into the C64 kernal. The operating system itself is divided into four pages of 16 KiB which are mapped in when required. The mapping is temporarily switched off while interrupts are running for increased compatibility, however this causes a ≈40 μs latency. Additional RAM for buffers and internal data are also mapped in from either the IDE64 cartridge (28 KiB) or the additional RAM of the SuperCPU is used. The standard kernal memory locations at page zero and page two are handled in a kernal-compatible way; temporarily used memory is restored after the routines are finished. Beyond the kernal table IDEDOS has two new calls for bulk data handling (read/write) which allows much faster data transfer rates than the character-based I/O. The native file system is non-CBM style at the low level to allow partitions greater than 16 MiB. High-level features like the 16-character filenames or filetypes are retained. Due to complexity and memory requirements, the filesystem creation and consistency check is not part of the operating system, unlike CBM DOS or CMD DOS. Additional filesystems like ISO 9660 or FAT are abstracted internally and mostly use the same routines for handling, thereby little difference is noticeable to user programs, except if some features are not fully implemented. The device handling is done by additional device numbers assigned to the new devices. The device numbers for IDEDOS devices are configurable and is normally in the range of 10–14. Over the years many programs assumed that there is only device 8 and do not allow selecting anything else; this can be worked around by temporary changing the used IDEDOS device number to 8. For standard devices, the original kernal routines are used, while IDEDOS devices use custom routines which closely imitate the results and behavior of kernal calls for floppy devices. Kernal calls not going through the vector table (most notably IEC bus-specific calls) present an incompatibility with those programs using them. Special features (like CD-ROM audio handling) are implemented by new channel 15 commands, while features not found on floppy drives follow the CMD style commands to allow programs to easily support a wider range of devices. Unlike intelligent external devices which have a separate processor (like 1541 with CBMDOS), IDEDOS runs on the host computer, thereby all disk routines block until finished. This rules out the use of "IRQ loaders" which are commonly used to speed up operation of serial bus peripherals. Interrupts are generally allowed while IDEDOS is running (they are disabled on rare time-critical operations), however the system was written to be non-reentrant, just like the original kernal. Short history In 1996 IDEDOS was born, as there was a need for a system to run the IDE64 1.1 card. It was created by Josef Souček (main code) and Tomáš Přibyl (File manager, Final cartridge monitor adaptation). Additional code came by Jan Vorlíček (BASIC extension), Jan Hlaváček (Duart PCLink). In 2000 Kajtár Zsolt added CDROM support, new setup code and lot of fixes. Due to limitations of the design the development of a completely rewritten version (0.90) was started by Kajtár Zsolt, which was not ready for general use before 2005. Meanwhile, the old version reached 0.898b in June 2004. In 2009 the 64 KiB limit for the system started to get tight, and the IDEDOS 0.91 beta was started to refactor the code to gain more space and internal flexibility. IDEDOS 0.898b This was the last version of the old IDEDOS series. Device support 2 ATA(PI) devices: hard disk, CompactFlash, CDROM, DVD Duart RS-232 card for PCLink SuperCPU v1/v2 Filesystem Custom filesystem called OFS 0.02 Up to 8 GiB, CHS addressing only, covers the whole disk 16 character filenames. Fixed file types of SEQ, PRG, USR. Directories are supported. Time stamping supported. Files up to 4 GiB, sequential access only ISO 9660 filesystem support Fastload Built in fast loader supported devices: 1541 as device 8 Fast load can be switched off in setup in case of incompatibility (non-1541 as device 8). Minimum interleave is 7, fast saver is only supported in manager, and uses an interleave of 8. PAL/NTSC compatible timing. PCLink Custom protocol, sequential access only. Supported devices: PC64 parallel cable Duart RS-232 Setup screen Includes clock with calendar, ability to set drive numbers, screen colours, auto boot, floppy fast loader, basic clock (TI$), power management, write retry, read-ahead and write cache drive settings, CDROM slow down option. BASIC extensions The BASIC extension includes disk handling commands (limited to IDEDOS devices), and adds some new error messages. Commands: CD – change working directory CDOPEN – open CDROM tray CDCLOSE – close CDROM tray CHANGE – change HDD device number DATE – print date and time DIR – normal directory listing HDINIT – re-detect IDE devices. INIT – initialize memory KILL – disable cartridge LL – long directory listing with timestamps, and file size in bytes. MAN – start file manager MKDIR – create directory RM – remove file or directory File manager It can be used to navigate around directories, start programs, copy/rename/delete files, create directories, and execute plugins to operate on files. Recursive file copy was only added in 0.898b, and in rare cases it does not work. Monitor The monitor is almost exactly the Final cartridge monitor in IDEDOS 0.89. Only standard 6502 opcodes are available. The commands are: A – Assemble instructions B – Bank switch C – Compare memory areas D – Disassemble from address EC – Edit char ES – Edit sprite F – Fill memory area G – Start execution at address H – Search pattern I – PETSCII display from address L – Load memory area M – Memory list O – Bank switch P – Print R – Show registers S – Save memory area T – Transfer memory area X – Exit monitor @ – Disk command # – Convert to hexadecimal $ – Convert to decimal *r – Read block from floppy drive *w – Write block to floppy drive Miscellaneous features Auto boot – can load and start a file on reset or power on. Custom screen colours – the default blue screen colours can be changed. Set the TI$ BASIC variable to the correct time on reset. Displays the start and end address for load. Special extension for bulk reading and writing of file data IDEDOS 0.90 This is the current stable, the latest version is 20100509 (patch 45). Most notable differences to 0.89 are: CFS 0.11 filesystem allows seekable and relative files, LBA support and partitioning. CMD compatible syntax for path handling and channel 15 commands Better PCLink protocol to allow the use of ethernet and USB Monitor which works like a freezer and is much faster More powerful file manager supporting CMD devices DOS wedge commands Programmable function keys BASIC extension support for non-IDEDOS devices Additional device support up to 4 ATA(PI) drives, ZIP and LS-120 support Support of V4.1 cartridge, linear read/write transfers for additional speed The battery on the IDE64 cartridge can be replaced with a supercap now. Device support 4 ATA(PI) devices: hard disk, CompactFlash, CDROM, DVD, LS-120, ZIP-drive Duart/SwiftLink/Turbo232/SilverSurfer RS-232, RR-Net/ETFE/ETH64 ethernet, FT245 USB cards for PCLink SuperCPU v2 Additional support for JiffyDOS/DolphinDOS drives Filesystem Custom filesystem called CFS 0.11 Up to 128 GiB, CHS/LBA addressing, up to 16 partitions 16 character file names. Customizable 3 character file types. Directories and soft links are supported. Relative files supported. Time stamping supported. Files up to 4 GiB, seekable ISO 9660 filesystem, partial OFS 0.02 support FAT12/16/32 slow read-only short filename support with DOS style partition tables Fastload Supported devices: CBM 1541/1571/1581 Any drive with JiffyDOS protocol (CMD FD) Additional support for DolphinDOS Device support is automatically detected, but can be disabled manually if needed. PAL/NTSC compatible timing. Fast saver only in the file manager. PCLink Custom protocol, sequential access only. Supported devices: IEC serial bus PC64 parallel cable Duart, SwiftLink, Turbo232 RS-232 RR-Net, ETFE, ETH64 ethernet FT245 USB Setup screen Clock with calendar Device number configuration and remapping Screen, manager and monitor colours Miscellaneous settings(auto boot, floppy fast loader, basic clock (TI$)) ATA(PI) device settings (power management, write retry, read-ahead and write cache, maximal linear read/write) DOS wedge Mostly the well known standard DOS wedge commands. @ – DOS command @$ – Directory @# – Select device / – Load BASIC program % – Load assembly program ' – Verify assembly program ↑ – Load BASIC program and execute ← – Save BASIC program £ – Load and execute assembly program . – Change directory # – Execute shell BASIC extensions The BASIC extension adds disk handling commands, which can be used with any device because they use CMD style commands. CD – change working directory CDOPEN – open CDROM tray CDCLOSE – close CDROM tray CHANGE – change device number DATE – print date and time DEF – redefine function keys DIR – normal directory listing HDINIT – re-detect IDE devices. INIT – initialize memory KILL – disable cartridge KILLNEW – re-new LL – long directory listing with timestamps, and file size in bytes. MAN – start file manager MKDIR – create directory RM – remove file RMDIR – remove directory File manager The file managers inspiration comes from 0.89, though it was rewritten from scratch. The goal was to have a file manager which not only supports IDEDOS devices, but also works well with CMD and other drives. Monitor The monitor was rewritten from scratch, the main inspiration was the CCS64 emulator's monitor, but some command ideas came from FC3/AR7/Vice monitors. The goal was to have freezer style (all registers including I/O editable) and fast machine code monitor which supports illegal 6502 and SuperCPU emulation mode opcodes. Commands: @ – Disk command, status and directory A – Assemble B – Memory configuration, select RAM/ROM BT – Backtrace C – Compare memory D – Disassemble , – Write hex data to memory and disassemble EC – Edit char (binary) [ – Write binary data to memory ES – Edit sprite (binary) ] – Write binary sprite data to memory F – Fill memory with byte G – Execute at address H – Search hex/any/text I – Dump memory in PETSCII ' – Write PETSCII data to memory IO – Dump I/O registers - – Write hex data to I/O memory IV – Restore I/O vectors J – Dump memory in screen code . – Write screen code data to memory K – Defreeze memory L – Load program LB – Load binary M – Dump memory in hex and PETSCII : – Write hex or PETSCII data to memory N – Number conversion and calculator O – Select work drive R – Show registers ; – Change registers S – Freeze memory/save program SB – Save binary T – Copy memory V – Verify program VB – Verify binary X – Continue program Q – Exit to BASIC warm start ←/↑ – Push and pop address(es) to stack. Miscellaneous features Auto boot - can load and start a file on reset or power on. Custom screen, monitor and manager colours - the default colours can be changed. Set the TI$ BASIC variable to the correct time on reset. Displays the start and end address for load/save. Special extension for bulk reading and writing of file data C128 keyboard support in C64 mode Special commands for handling CDROM drives Raw directory read CMD style long directory lists with timestamps IDEDOS 0.91 beta This is still in development. Most notable differences to 0.90 are: OFS 0.02 support removed Protected BASIC, serial and PCLink routines F-keys work with interrupts Read ($DEF4) works below I/O Auto starting programs work from IEC devices now PCLink load below I/O SilverSurfer PCLink support, PCLink optional FAT filesystem read ($DEF4) and load Combined CFS and FAT partitions, per partition filesystem support Partition list for FAT and ISO9660 Dynamic drive enumeration, PCLink detection Read ($DEF4) and write ($DEF1) support on modifiable files Timestamp update only if modified Seeking, modifiable and appendable files on PCLink PCLink protocol changes PCLink activity LED Relative file support has been lost References IDEDOS 0.91 beta http://singularcrew.hu/idedos/beta/ IDEDOS 0.90 http://singularcrew.hu/idedos/IDE64_users_guide.pdf IDEDOS 0.89 http://www.volny.cz/dundera/manual.html External links The webpage of IDEDOS The webpage of the IDE64 cartridge Disk operating systems Commodore 64 software

Operating System (OS)

Initialization Initialization may refer to: Booting, a process that starts computer operating systems Initialism, an abbreviation formed using the initial letters of words or word parts In computing, formatting a storage medium like a hard disk or memory. Also, making sure a device is available to the operating system. Initialization (programming)

Operating System (OS)

UTS UTS may refer to: Computing Unicode Technical Standard Universal Time-Sharing System, an operating system for XDS Sigma computers Amdahl UTS, a Unix operating system for IBM-compatible mainframes Science and mechanical Ultimate tensile strength of a material Unified Thread Standard for screws Untriseptium, an unsynthesized chemical element Education Unification Theological Seminary of the Unification Church, New York, US Union Theological Seminary (Philippines), Protestant seminary Union Theological Seminary in the City of New York, US University of Technology Sydney, Australia University of Toronto Schools, Canada University Transit Service of the University of Virginia, US Other uses Uts (river), a river in Belarus Huntsville Regional Airport in Huntsville, Texas (FAA ID) Underground Ticketing System, as used in London Underground ticketing Uner Tan syndrome Ultimate Tennis Showdown

Operating System (OS)

Debian Debian (), also known as Debian GNU/Linux, is a GNU/Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of Debian (0.01) was released on September 15, 1993, and its first stable version (1.1) was released on June 17, 1996. The Debian Stable branch is the most popular edition for personal computers and servers. Debian is also the basis for many other distributions, most notably Ubuntu. Debian is one of the oldest operating systems based on the Linux kernel. The project is coordinated over the Internet by a team of volunteers guided by the Debian Project Leader and three foundational documents: the Debian Social Contract, the Debian Constitution, and the Debian Free Software Guidelines. New distributions are updated continually, and the next candidate is released after a time-based freeze. Since its founding, Debian has been developed openly and distributed freely according to the principles of the GNU Project. Because of this, the Free Software Foundation sponsored the project from November 1994 to November 1995. When the sponsorship ended, the Debian Project formed the nonprofit organization Software in the Public Interest to continue financially supporting development. History Debian version history Debian distribution codenames are based on the names of characters from the Toy Story films. Debian's unstable trunk is named after Sid, a character who regularly destroyed his toys. Founding (1993–1998) Debian was first announced on August 16, 1993, by Ian Murdock, who initially called the system "the Debian Linux Release". The word "Debian" was formed as a portmanteau of the first name of his then-girlfriend (later ex-wife) Debra Lynn and his own first name. Before Debian's release, the Softlanding Linux System (SLS) had been a popular Linux distribution and the basis for Slackware. The perceived poor maintenance and prevalence of bugs in SLS motivated Murdock to launch a new distribution. Debian 0.01, released on September 15, 1993, was the first of several internal releases. Version 0.90 was the first public release, providing support through mailing lists hosted at Pixar. The release included the Debian Linux Manifesto, outlining Murdock's view for the new operating system. In it he called for the creation of a distribution to be maintained openly, in the spirit of Linux and GNU. The Debian project released the 0.9x versions in 1994 and 1995. During this time it was sponsored by the Free Software Foundation for one year. Ian Murdock delegated the base system, the core packages of Debian, to Bruce Perens and Murdock focused on the management of the growing project. The first ports to non-IA-32 architectures began in 1995, and Debian 1.1 was released in 1996. By that time and thanks to Ian Jackson, the dpkg package manager was already an essential part of Debian. In 1996, Bruce Perens assumed the project leadership. Perens was a controversial leader, regarded as authoritarian and strongly attached to Debian. He drafted a social contract and edited suggestions from a month-long discussion into the Debian Social Contract and the Debian Free Software Guidelines. After the FSF withdrew their sponsorship in the midst of the free software vs. open source debate, Perens initiated the creation of the legal umbrella organization Software in the Public Interest instead of seeking renewed involvement with the FSF. He led the conversion of the project from a.out to ELF. He created the BusyBox program to make it possible to run a Debian installer on a single floppy, and wrote a new installer. By the time Debian 1.2 was released, the project had grown to nearly two hundred volunteers. Perens left the project in 1998. Ian Jackson became the leader in 1998. Debian 2.0 introduced the second official port, m68k. During this time the first port to a non-Linux kernel, Debian GNU/Hurd, was started. On December 2, the first Debian Constitution was ratified. Leader election (1999–2005) From 1999, the project leader was elected yearly. The Advanced Packaging Tool was deployed with Debian 2.1. The number of applicants was overwhelming and the project established the new member process. The first Debian derivatives, namely Libranet, Corel Linux and Stormix's Storm Linux, were started in 1999. The 2.2 release in 2000 was dedicated to Joel Klecker, a developer who died of Duchenne muscular dystrophy. In late 2000, the project reorganized the archive with new package "pools" and created the Testing distribution, made up of packages considered stable, to reduce the freeze for the next release. In the same year, developers began holding an annual conference called DebConf with talks and workshops for developers and technical users. In May 2001, Hewlett-Packard announced plans to base its Linux development on Debian. In July 2002, the project released version 3.0, code-named Woody, the first release to include cryptographic software, a free licensed KDE and internationalization. During these last release cycles, the Debian project drew considerable criticism from the free software community because of the long time between stable releases. Some events disturbed the project while working on Sarge, as Debian servers were attacked by fire and hackers. One of the most memorable was the Vancouver prospectus. After a meeting held in Vancouver, release manager Steve Langasek announced a plan to reduce the number of supported ports to four in order to shorten future release cycles. There was a large reaction because the proposal looked more like a decision and because such a drop would damage Debian's aim to be "the universal operating system". The first version of the Debian-based Ubuntu, named "4.10 Warty Warthog", was released on October 20, 2004. Because it was distributed as a free download, it became one of the most popular and successful operating systems with more than "40 million users" according to Canonical Ltd. However, Murdock was critical of the differences between Ubuntu packages and Debian, stating that it leads to incompatibilities. Sarge and later releases (2005–present) The 3.1 Sarge release was made in June 2005. This release updated 73% of the software and included over 9,000 new packages. A new installer with a modular design, Debian-Installer, allowed installations with RAID, XFS and LVM support, improved hardware detection, made installations easier for novice users, and was translated into almost forty languages. An installation manual and release notes were in ten and fifteen languages respectively. The efforts of Skolelinux, Debian-Med and Debian-Accessibility raised the number of packages that were educational, had a medical affiliation, and ones made for people with disabilities. In 2006, as a result of a much-publicized dispute, Mozilla software was rebranded in Debian, with Firefox forked as Iceweasel and Thunderbird as Icedove. The Mozilla Corporation stated that software with unapproved modifications could not be distributed under the Firefox trademark. Two reasons that Debian modifies the Firefox software are to change the non-free artwork and to provide security patches. In February 2016, it was announced that Mozilla and Debian had reached an agreement and Iceweasel would revert to the name Firefox; similar agreement was anticipated for Icedove/Thunderbird. A fund-raising experiment, Dunc-Tank, was created to solve the release cycle problem and release managers were paid to work full-time; in response, unpaid developers slowed down their work and the release was delayed. Debian 4.0 (Etch) was released in April 2007, featuring the x86-64 port and a graphical installer. Debian 5.0 (Lenny) was released in February 2009, supporting Marvell's Orion platform and netbooks such as the Asus Eee PC. The release was dedicated to Thiemo Seufer, a developer who died in a car crash. In July 2009, the policy of time-based development freezes on a two-year cycle was announced. Time-based freezes are intended to blend the predictability of time based releases with Debian's policy of feature based releases, and to reduce overall freeze time. The Squeeze cycle was going to be especially short; however, this initial schedule was abandoned. In September 2010, the backports service became official, providing more recent versions of some software for the stable release. Debian 6.0 (Squeeze) was released in February 2011, featuring Debian GNU/kFreeBSD as a technology preview, along with adding a dependency-based boot system, and moving problematic firmware to the non-free section. Debian 7.0 (Wheezy) was released in May 2013, featuring multiarch support. Debian 8.0 (Jessie) was released in April 2015, using systemd as the new init system. Debian 9.0 (Stretch) was released in June 2017, with nftables as a replacement for iptables, support for Flatpak apps, and MariaDB as the replacement for MySQL. Debian 10.0 (Buster) was released in July 2019, adding support for Secure Boot and enabling AppArmor by default. Debian 11.0 (Bullseye) was released in August 2021, enabling persistency in the system journal, adding support for driverless scanning, and containing kernel-level support for exFAT filesystems. Debian is still in development and new packages are uploaded to unstable every day. Debian used to be released as a very large set of CDs for each architecture, but with the release of Debian 9 (Stretch) in 2017, these have been dropped. Throughout Debian's lifetime, both the Debian distribution and its website have won various awards from different organizations, including Server Distribution of the Year 2011, The best Linux distro of 2011, and a Best of the Net award for October 1998. On December 2, 2015, Microsoft announced that they would offer Debian GNU/Linux as an endorsed distribution on the Azure cloud platform. Microsoft has also added a user environment to their Windows 10 desktop operating system called Windows Subsystem for Linux that offers a Debian subset. Features Debian has access to online repositories that contain over 51,000 packages. Debian officially contains only free software, but non-free software can be downloaded and installed from the Debian repositories. Debian includes popular free programs such as LibreOffice, Firefox web browser, Evolution mail, K3b disc burner, VLC media player, GIMP image editor, and Evince document viewer. Debian is a popular choice for servers, for example as the operating system component of a LAMP stack. Kernels Several flavors of the Linux kernel exist for each port. For example, the i386 port has flavors for IA-32 PCs supporting Physical Address Extension and real-time computing, for older PCs, and for x86-64 PCs. The Linux kernel does not officially contain firmware without sources, although such firmware is available in non-free packages and alternative installation media. Desktop environments Debian offers CD and DVD images specifically built for XFCE, GNOME, KDE, MATE, Cinnamon, LXDE, and LXQT. MATE is officially supported, while Cinnamon support was added with Debian 8.0 Jessie. Less common window managers such as Enlightenment, Openbox, Fluxbox, IceWM, Window Maker and others are available. The default desktop environment of version 7.0 Wheezy was temporarily switched to Xfce, because GNOME 3 did not fit on the first CD of the set. The default for the version 8.0 Jessie was changed again to Xfce in November 2013, and back to GNOME in September 2014. Localization Several parts of Debian are translated into languages other than American English, including package descriptions, configuration messages, documentation and the website. The level of software localization depends on the language, ranging from the highly supported German and French to the barely translated Creek and Samoan. The Debian 10 installer is available in 76 languages. Multimedia support Multimedia support has been problematic in Debian regarding codecs threatened by possible patent infringements, without sources or under too restrictive licenses. Even though packages with problems related to their distribution could go into the non-free area, software such as libdvdcss is not hosted at Debian. A notable third party repository exists, formerly named debian-multimedia.org, providing software not present in Debian such as Windows codecs, libdvdcss and the Adobe Flash Player. Even though this repository is maintained by Christian Marillat, a Debian developer, it is not part of the project and is not hosted on a Debian server. The repository provides packages already included in Debian, interfering with the official maintenance. Eventually, project leader Stefano Zacchiroli asked Marillat to either settle an agreement about the packaging or to stop using the "Debian" name. Marillat chose the latter and renamed the repository to deb-multimedia.org. The repository was so popular that the switchover was announced by the official blog of the Debian project. Distribution Debian offers DVD and CD images for installation that can be downloaded using BitTorrent or jigdo. Physical discs can also be bought from retailers. The full sets are made up of several discs (the amd64 port consists of 13 DVDs or 84 CDs), but only the first disc is required for installation, as the installer can retrieve software not contained in the first disc image from online repositories. Debian offers different network installation methods. A minimal install of Debian is available via the netinst CD, whereby Debian is installed with just a base and later added software can be downloaded from the Internet. Another option is to boot the installer from the network. The default bootstrap loader is GNU GRUB version 2, though the package name is simply grub, while version 1 was renamed to grub-legacy. This conflicts with (e.g., Fedora Linux), where grub version 2 is named grub2. The default desktop may be chosen from the DVD boot menu among GNOME, KDE Plasma, Xfce and LXDE, and from special disc 1 CDs. Debian releases live install images for CDs, DVDs and USB thumb drives, for IA-32 and x86-64 architectures, and with a choice of desktop environments. These Debian Live images allow users to boot from removable media and run Debian without affecting the contents of their computer. A full install of Debian to the computer's hard drive can be initiated from the live image environment. Personalized images can be built with the live-build tool for discs, USB drives and for network booting purposes. Installation images are hybrid on some architectures and can be used to create a bootable USB drive (Live USB). Packages Package management operations can be performed with different tools available on Debian, from the lowest level command dpkg to graphical front-ends like Synaptic. The recommended standard for administering packages on a Debian system is the apt toolset. dpkg provides the low-level infrastructure for package management. The dpkg database contains the list of installed software on the current system. The dpkg command tool does not know about repositories. The command can work with local .deb package files, and information from the dpkg database. APT tools An Advanced Packaging Tool (APT) allows administering an installed Debian system to retrieve and resolve package dependencies from repositories. APT share dependency information and cached packages. The apt command itself is intended as an end user interface and enables some options better suited for interactive usage by default compared to more specialized APT like apt-get and apt-cache explained below. apt-get and apt-cache are command tools of the standard apt package. apt-get installs and removes packages, and apt-cache is used for searching packages and displaying package information. Aptitude is a command line tool that also offers a text-based user interface. The program comes with enhancements such as better search on package metadata. GDebi and other front-ends GDebi is an APT tool which can be used in command-line and on the GUI. GDebi can install a local .deb file via the command line like the dpkg command, but with access to repositories to resolve dependencies. Other graphical front-ends for APT include Software Center, Synaptic and Apper. GNOME Software is a graphical front-end for PackageKit, which itself can work on top of various software packaging systems. Repositories The Debian Free Software Guidelines (DFSG) define the distinctive meaning of the word "free" as in "free and open-source software". Packages that comply with these guidelines, usually under the GNU General Public License, Modified BSD License or Artistic License, are included inside the main area; otherwise, they are included inside the non-free and contrib areas. These last two areas are not distributed within the official installation media, but they can be adopted manually. Non-free includes packages that do not comply with the DFSG, such as documentation with invariant sections and proprietary software, and legally questionable packages. Contrib includes packages which do comply with the DFSG but fail other requirements. For example, they may depend on packages which are in non-free or requires such for building them. Richard Stallman and the Free Software Foundation have criticized the Debian project for hosting the non-free repository and because the contrib and non-free areas are easily accessible, an opinion echoed by some in Debian including the former project leader Wichert Akkerman. The internal dissent in the Debian project regarding the non-free section has persisted, but the last time it came to a vote in 2004, the majority decided to keep it. Cross-distribution package manager The most popular optional Linux cross-distribution package manager are graphical (front-ends) package managers. They are available within the official Debian Repository. But not installed by default. They are widely popular with both Debian users and Debian software developers who are interested in installing the most recent versions of application or using the cross-distribution package manager built-in sandbox environment. While at the same time remaining in control of the security. Three most popular cross-distribution package managers. Sorted in alphabetical order: Flatpak software code is owned and maintain by the not for profit Flatpak Team. With an open source LGPL-2.1-only license. Homebrew software code is owned and maintain by its original author Max Howell. With an open source BSD 2-Clause License license. Snap software code is owned and maintain by the for profit Canonical Group Limited. With an open source GNU General Public License, version 3.0 license. Branches Three branches of Debian (also called releases, distributions or suites) are regularly maintained: Stable is the current release and targets stable and well-tested software needs. Stable is made by freezing Testing for a few months where bugs are fixed and packages with too many bugs are removed; then the resulting system is released as stable. It is updated only if major security or usability fixes are incorporated. This branch has an optional backports service that provides more recent versions of some software. Stables CDs and DVDs can be found in the Debian website. Testing is the preview branch that will eventually become the next major release. The packages included in this branch have had some testing in unstable but they may not be fit for release yet. It contains newer packages than stable but older than unstable. This branch is updated continually until it is frozen. Testings CDs and DVDs can be found on the Debian website. Unstable, always codenamed sid, is the trunk. Packages are accepted without checking the distribution as a whole. This branch is usually run by software developers who participate in a project and need the latest libraries available, and by those who prefer bleeding-edge software. Debian does not provide full Sid installation discs, but rather a minimal ISO that can be used to install over a network connection. Additionally, this branch can be installed through a system upgrade from stable or testing. Other branches in Debian: Oldstable is the prior stable release. It is supported by the Debian Security Team until one year after a new stable is released, and since the release of Debian 6, for another 2 years through the Long Term Support project. Eventually, oldstable is moved to a repository for archived releases. Debian 10 is the current Oldstable release. Oldoldstable is the prior oldstable release. It is supported by the Long Term Support community. Eventually, oldoldstable is moved to a repository for archived releases. Debian 9 is the current Oldoldstable release. Experimental is a temporary staging area of highly experimental software that is likely to break the system. It is not a full distribution and missing dependencies are commonly found in unstable, where new software without the damage chance is normally uploaded. The snapshot archive provides older versions of the branches. They may be used to install a specific older version of some software. Numbering scheme Stable and oldstable get minor updates, called point releases; , the stable release is version 11.0, released on , and the oldstable release is version 10.10. The numbering scheme for the point releases up to Debian 4.0 was to include the letter r (for revision) after the main version number and then the number of the point release; for example, the latest point release of version 4.0 is 4.0r9. This scheme was chosen because a new dotted version would make the old one look obsolete and vendors would have trouble selling their CDs. From Debian 5.0, the numbering scheme of point releases was changed, conforming to the GNU version numbering standard; the first point release of Debian 5.0 was 5.0.1 instead of 5.0r1. The numbering scheme was once again changed for the first Debian 7 update, which was version 7.1. The r scheme is no longer in use, but point release announcements include a note about not throwing away old CDs. Derivatives and flavors Debian is one of the most popular Linux distributions, and many other distributions have been created from the Debian codebase. , DistroWatch lists 121 active Debian derivatives. The Debian project provides its derivatives with guidelines for best practices and encourages derivatives to merge their work back into Debian. Debian Pure Blends are subsets of a Debian release configured out-of-the-box for users with particular skills and interests. For example, Debian Jr. is made for children, while Debian Science is for researchers and scientists. The complete Debian distribution includes all available Debian Pure Blends. "Debian Blend" (without "Pure") is a term for a Debian-based distribution that strives to become part of mainstream Debian, and have its extra features included in future releases. Debian GNU/kFreeBSD is a discontinued Debian flavor. It used the FreeBSD kernel and GNU userland. The majority of software in Debian GNU/kFreeBSD was built from the same sources as Debian, with some kernel packages from FreeBSD. The k in kFreeBSD is an abbreviation for kernel, which refers to the FreeBSD kernel. Before discontinuing the project, Debian maintained i386 and amd64 ports. The last version of Debian kFreeBSD was Debian 8 (Jessie) RC3. Debian GNU/kFreeBSD was created in 2002. It was included in Debian 6.0 (Squeeze) as a technology preview, and in Debian 7.0 (Wheezy) as an official port. Debian GNU/kFreeBSD was discontinued as an officially supported platform as of Debian 8.0. Debian developers cited OSS, pf, jails, NDIS, and ZFS as reasons for being interested in the FreeBSD kernel. It has not been updated since Debian 8. As of July 2019, however, the operating system continues to be maintained unofficially. Debian GNU/Hurd is a flavor based on the Hurd microkernel, instead of Linux. Debian GNU/Hurd has been in development since 1998, and made a formal release in May 2013, with 78% of the software packaged for Debian GNU/Linux ported to the GNU Hurd. Hurd is not yet an official Debian release, and is maintained and developed as an unofficial port. Debian GNU/Hurd is distributed as an installer CD (running the official Debian installer) or ready-to-run virtual disk image (Live CD, Live USB). The CD uses the IA-32 architecture, making it compatible with IA-32 and x86-64 PCs. The current version of Debian GNU/Hurd is 2021, published in August 2021. Branding The Debian "swirl" logo was designed by Raul Silva in 1999 as part of a contest to replace the semi-official logo that had been used. The winner of the contest received an @debian.org email address, and a set of Debian 2.1 install CDs for the architecture of their choice. There has been no official statement from the Debian project on the logo's meaning, but at the time of the logo's selection, it was suggested that the logo represented the magic smoke ( or the genie ) that made computers work. One theory about the origin of the Debian logo is that Buzz Lightyear, the chosen character for the first named Debian release, has a swirl in his chin. Stefano Zacchiroli also suggested that this swirl is the Debian one. Buzz Lightyear's swirl is a more likely candidate as the codenames for Debian are names of Toy Story characters. The former Debian project leader Bruce Perens used to work for Pixar and is credited as a studio tools engineer on Toy Story 2 (1999). Hardware Hardware requirements are at least those of the kernel and the GNU toolsets. Debian's recommended system requirements depend on the level of installation, which corresponds to increased numbers of installed components: The real minimum memory requirements depend on the architecture and may be much less than the numbers listed in this table. It is possible to install Debian with 170 MB of RAM for x86-64; the installer will run in low memory mode and it is recommended to create a swap partition. The installer for z/Architecture requires about 20 MB of RAM, but relies on network hardware. Similarly, disk space requirements, which depend on the packages to be installed, can be reduced by manually selecting the packages needed. , no Pure Blend exists that would lower the hardware requirements easily. It is possible to run graphical user interfaces on older or low-end systems, but the installation of window managers instead of desktop environments is recommended, as desktop environments are more resource intensive. Requirements for individual software vary widely and must be considered, with those of the base operating environment. Architectures , the official ports are: amd64: x86-64 architecture with 64-bit userland and supporting 32-bit software arm64: ARMv8-A architecture armel: Little-endian ARM architecture (ARMv4T instruction set) on various embedded systems (embedded application binary interface (EABI)), although support has ended after Buster armhf: ARM hard-float architecture (ARMv7 instruction set) requiring hardware with a floating-point unit i386: IA-32 architecture with 32-bit userland, compatible with x86-64 machines mips64el: Little-endian 64-bit MIPS mipsel: Little-endian 32-bit MIPS ppc64el: Little-endian PowerPC architecture supporting POWER7+ and POWER8 CPUs s390x: z/Architecture with 64-bit userland, intended to replace s390 Unofficial ports are available as part of the unstable distribution: alpha: DEC Alpha architecture hppa: HP PA-RISC architecture hurd-i386: GNU Hurd kernel on IA-32 architecture ia64: Intel Itanium kfreebsd-amd64: Kernel of FreeBSD on x86-64 architecture kfreebsd-i386: Kernel of FreeBSD on IA-32 architecture m68k: Motorola 68k architecture on Amiga, Atari, Macintosh and various embedded VME systems powerpc: 32-bit PowerPC ppc64: PowerPC64 architecture supporting 64-bit PowerPC CPUs with VMX riscv64: 64-bit RISC-V sh4: Hitachi SuperH architecture sparc64: Sun SPARC architecture with 64-bit userland x32: x32 ABI userland for x86-64 Debian supports a variety of ARM-based NAS devices. The NSLU2 was supported by the installer in Debian 4.0 and 5.0, and Martin Michlmayr is providing installation tarballs since version 6.0. Other supported NAS devices are the Buffalo Kurobox Pro, GLAN Tank, Thecus N2100 and QNAP Turbo Stations. Devices based on the Kirkwood system on a chip (SoC) are supported too, such as the SheevaPlug plug computer and OpenRD products. There are efforts to run Debian on mobile devices, but this is not a project goal yet since the Debian Linux kernel maintainers would not apply the needed patches. Nevertheless, there are packages for resource-limited systems. There are efforts to support Debian on wireless access points. Debian is known to run on set-top boxes. Work is ongoing to support the AM335x processor, which is used in electronic point of service solutions. Debian may be customized to run on cash machines. BeagleBoard, a low-power open-source hardware single-board computer (made by Texas Instruments) has switched to Debian Linux preloaded on its Beaglebone Black board's flash. Roqos Core, manufactured by Roqos, is a x86-64 based IPS firewall router running Debian Linux. Organization Debian's policies and team efforts focus on collaborative software development and testing processes. As a result, a new major release tends to occur every two years with revision releases that fix security issues and important problems. The Debian project is a volunteer organization with three foundational documents: The Debian Social Contract defines a set of basic principles by which the project and its developers conduct affairs. The Debian Free Software Guidelines define the criteria for "free software" and thus what software is permissible in the distribution. These guidelines have been adopted as the basis of the Open Source Definition. Although this document can be considered separate, it formally is part of the Social Contract. The Debian Constitution describes the organizational structure for formal decision-making within the project, and enumerates the powers and responsibilities of the Project Leader, the Secretary and other roles. Debian developers are organized in a web of trust. There are about one thousand active Debian developers, but it is possible to contribute to the project without being an official developer. The project maintains official mailing lists and conferences for communication and coordination between developers. For issues with single packages and other tasks, a public bug tracking system is used by developers and end users. Internet Relay Chat is also used for communication among developers and to provide real time help. Debian is supported by donations made to organizations authorized by the leader. The largest supporter is Software in the Public Interest, the owner of the Debian trademark, manager of the monetary donations and umbrella organization for various other community free software projects. A Project Leader is elected once per year by the developers. The leader has special powers, but they are not absolute, and appoints delegates to perform specialized tasks. Delegates make decisions as they think is best, taking into account technical criteria and consensus. By way of a General Resolution, the developers may recall the leader, reverse a decision made by the leader or a delegate, amend foundational documents and make other binding decisions. The voting method is based on the Schulze method (Cloneproof Schwartz Sequential Dropping). Project leadership is distributed occasionally. Branden Robinson was helped by the Project Scud, a team of developers that assisted the leader, but there were concerns that such leadership would split Debian into two developer classes. Anthony Towns created a supplemental position, Second In Charge (2IC), that shared some powers of the leader. Steve McIntyre was 2IC and had a 2IC himself. One important role in Debian's leadership is that of a release manager. The release team sets goals for the next release, supervises the processes and decides when to release. The team is led by the next release managers and stable release managers. Release assistants were introduced in 2003. Developers The Debian Project has an influx of applicants wishing to become developers. These applicants must undergo a vetting process which establishes their identity, motivation, understanding of the project's principles, and technical competence. This process has become much harder throughout the years. Debian developers join the project for many reasons. Some that have been cited include: Debian is their main operating system and they want to promote Debian To improve the support for their favorite technology They are involved with a Debian derivative A desire to contribute back to the free-software community To make their Debian maintenance work easier Debian developers may resign their positions at any time or, when deemed necessary, they can be expelled. Those who follow the retiring protocol are granted the "emeritus" status and they may regain their membership through a shortened new member process. Development Flowchart of the life cycle of a Debian package Each software package has a maintainer that may be either one person or a team of Debian developers and non-developer maintainers. The maintainer keeps track of upstream releases, and ensures that the package coheres with the rest of the distribution and meets the standards of quality of Debian. Packages may include modifications introduced by Debian to achieve compliance with Debian Policy, even to fix non-Debian specific bugs, although coordination with upstream developers is advised. The maintainer releases a new version by uploading the package to the "incoming" system, which verifies the integrity of the packages and their digital signatures. If the package is found to be valid, it is installed in the package archive into an area called the "pool" and distributed every day to hundreds of mirrors worldwide. The upload must be signed using OpenPGP-compatible software. All Debian developers have individual cryptographic key pairs. Developers are responsible for any package they upload even if the packaging was prepared by another contributor. Initially, an accepted package is only available in the unstable branch. For a package to become a candidate for the next release, it must migrate to the Testing branch by meeting the following: It has been in unstable for a certain length of time that depends on the urgency of the changes. It does not have "release-critical" bugs, except for the ones already present in Testing. Release-critical bugs are those considered serious enough that they make the package unsuitable for release. There are no outdated versions in unstable for any release ports. The migration does not break any packages in Testing. Its dependencies can be satisfied by packages already in Testing or by packages being migrated at the same time. The migration is not blocked by a freeze. Thus, a release-critical bug in a new version of a shared library on which many packages depend may prevent those packages from entering Testing, because the updated library must meet the requirements too. From the branch viewpoint, the migration process happens twice per day, rendering Testing in perpetual beta. Periodically, the release team publishes guidelines to the developers in order to ready the release. A new release occurs after a freeze, when all important software is reasonably up-to-date in the Testing branch and any other significant issues are solved. At that time, all packages in the testing branch become the new stable branch. Although freeze dates are time-based, release dates are not, which are announced by the release managers a couple of weeks beforehand. A version of a package can belong to more than one branch, usually testing and unstable. It is possible for a package to keep the same version between stable releases and be part of oldstable, stable, testing and unstable at the same time. Each branch can be seen as a collection of pointers into the package "pool" mentioned above. One optional resolution to the challenge with release-critical bug in an application new version is the use of optional package managers. Which allow software developers, to use sandbox environments. While at the same time remaining in controle of the security. Another benefit of cross-distribution package manager is that they allows application developers to directly provide updates to users without going through distributions, and without having to package and test the application separately for each distribution. Release cycle A new stable branch of Debian gets released approximately every 2 years. It will receive official support for about 3 years with update for major security or usability fixes. Point releases will be available every several months as determined by Stable Release Managers (SRM). Debian also launched its Long Term Support (LTS) project since Debian 6 (Debian Squeeze). For each Debian release, it will receive two years of extra security updates provided by LTS Team after its End Of Life (EOL). However, no point releases will be made. Now each Debian release can receive 5 years of security support in total. Security The Debian project handles security through public disclosure. Debian security advisories are compatible with the Common Vulnerabilities and Exposures dictionary, are usually coordinated with other free software vendors and are published the same day a vulnerability is made public. There used to be a security audit project that focused on packages in the stable release looking for security bugs; Steve Kemp, who started the project, retired in 2011 but resumed his activities and applied to rejoin in 2014. The stable branch is supported by the Debian security team; oldstable is supported for one year. Although Squeeze is not officially supported, Debian is coordinating an effort to provide long-term support (LTS) until February 2016, five years after the initial release, but only for the IA-32 and x86-64 platforms. Testing is supported by the testing security team, but does not receive updates in as timely a manner as stable. Unstables security is left for the package maintainers. The Debian project offers documentation and tools to harden a Debian installation both manually and automatically. AppArmor support is available and enabled by default since Buster. Debian provides an optional hardening wrapper, and does not harden all of its software by default using gcc features such as PIE and buffer overflow protection, unlike operating systems such as OpenBSD, but tries to build as many packages as possible with hardening flags. In May 2008, a Debian developer discovered that the OpenSSL package distributed with Debian and derivatives such as Ubuntu made a variety of security keys vulnerable to a random number generator attack, since only 32,767 different keys were generated. The security weakness was caused by changes made in 2006 by another Debian developer in response to memory debugger warnings. The complete resolution procedure was cumbersome because patching the security hole was not enough; it involved regenerating all affected keys and certificates. Value The cost of developing all of the packages included in Debian 5.0 Lenny (323 million lines of code) has been estimated to be about , using one method based on the COCOMO model. , Black Duck Open Hub estimates that the current codebase (74 million lines of code) would cost about to develop, using a different method based on the same model. Forks and derivatives A large number of forks and derivatives have been built upon Debian over the years. Among the more notable are Ubuntu, developed by Canonical Ltd. and first released in 2004, which has surpassed Debian in popularity with desktop users; Knoppix, first released in the year 2000 and one of the first distributions optimized to boot from external storage; and Devuan, which gained attention in 2014 when it forked in disagreement over Debian's adoption of the systemd software suite, and has been mirroring Debian releases since 2017. See also Comparison of Linux distributions Debian version history List of Debian project leaders Notes References Further reading External links Debian vs Arch Linux at TechiWiki 1993 software ARM Linux distributions Free software culture and documents IA-32 Linux distributions LXQt Operating system distributions bootable from read-only media Power ISA Linux distributions PowerPC Linux distributions X86-64 Linux distributions Linux distributions

Operating System (OS)

Formatted File System The Formatted File System (FFS) is the name of a series of Database Management Systems (DBMS) developed for military use and designed to run on IBM mainframe computers. The period from 1964 to 1968 saw the transition from isolated DBMS development efforts to the development of DBMS families. The Formatted File System is one such family. Others included General Electric's IDS family, and the Mark IV series developed by Informatics Inc. (later acquired by Sterling Software). These families were developed across organizations and branches of government, spreading and evolving with their primary developers. Beginning around 1968, industry DBMS development became increasingly proprietary. Family Members IRS(DTMB), 1958, IBM 704 Information Retrieval System (David Taylor Model Basin) TUFF/TUG(DTMB), 1959, IBM 704/9 Tape Update for Formatted Files / Tape Updater and Generator (David Taylor Model Basin) FFS(SAC), 1961, IBM 7090 Formatted File System (Strategic Air Command) FFS(IDHS), 1963, IBM 1401 Formatted File System (Intelligence Data-Handling System) FFS(FICEUR), 1963, IBM 1410 Formatted File System (Naval Fleet Intelligence Center in Europe) FFS(DIA-IDHS), 1965, IBM 1410 Formatted File System (Defense Intelligence Agency - Intelligence Data-Handling System) GIS, 1965, IBM SYSTEM/360 Generalized Information System NIPS, 1965, IBM 1410 NMCS (National Military Command System) Information Processing System NIPS, 1968, IBM SYSTEM/360 NMCS (National Military Command System) Information Processing System CDMS, 1968, IBM SYSTEM/360 Cobol Data Management System References Proprietary database management systems IBM mainframe software

Operating System (OS)

FlexOS FlexOS is a discontinued modular real-time multiuser multitasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business Unit in Monterey, California, in 1985, the system was considered to become a successor of Digital Research's earlier Concurrent DOS, but with a new, modular, and considerably different system architecture and portability across various processor families. Still named Concurrent DOS 68K and Concurrent DOS 286, it was renamed into FlexOS on 1 October 1986 to better differentiate the target audiences. FlexOS was licensed by several OEMs who selected it as the basis for their own operating systems like 4680 OS, 4690 OS, S5-DOS/MT and others. Unrelated to FlexOS, the original Concurrent DOS system architecture found a continuation in successors like Concurrent DOS XM and Concurrent DOS 386 as well. Overview Concurrent DOS 286, Concurrent DOS 68K and FlexOS were designed by Francis "Frank" R. Holsworth (using siglum FRH). Like Portable CP/M, Concurrent DOS 286, Concurrent DOS 68K and Concurrent DOS V60, FlexOS was written in C for higher portability across hardware platforms, and it featured very low interrupt latency and fast context switching. It is supported by popular SSL/TLS libraries such as wolfSSL. The original protected mode FlexOS 286 version 1.3 was designed for host machines equipped with 286 CPUs, and with adaptations for NEC V60, NEC V70 and Motorola 68000 processors planned. FlexOS 286 executables using the system's native INT DCh (INT 220) application program interface had the filename extension .286. A CP/M API front-end (FE) was available as well, using the extension .CMD for executables. (A filename extension of .68K was reserved for FlexOS 68K, a file extension derived from Concurrent DOS 68K as of 1986.) In May 1987, FlexOS version 1.31 was released for 80286 machines. The developer version required an IBM PC/AT-compatible machine with 640 KB of conventional and 512 KB of extended memory, and either a (monochrome) CGA or an EGA graphics adapter. FlexOS supported a concept of dynamically loadable and unloadable subdrivers, and it came with driver prototypes for floppies, hard disks, printers, serial interfaces, RAM disks, mice and console drivers. During boot, the FLEX286.SYS kernel would load the resource managers and device drivers specified in the CONFIG.SYS binary file (not to be mixed up with the similarly named CONFIG.SYS configuration file under DOS), and its shell (COMMAND.286) would execute a CONFIG.BAT startup batch job instead of the common AUTOEXEC.BAT. FlexOS's optional DOS emulator provided limited PC DOS 2.1 compatibility for DOS .COM and .EXE programs. Certain restrictions applied since these programs were executed in the processor's protected mode. Due to bugs in earlier steppings of the Intel 80286, the FlexOS 286 DOS front-end required at least the 80286 E2 stepping to function properly (see LOADALL). These problems had already caused delays in the delivery of Concurrent DOS 286 earlier. The system optionally supported a multitasking GEM VDI for graphical applications. FlexOS 1.31 could be linked with none, either or both of these two modules. FlexOS 1.31 also supported FlexNet. By June 1987 there were also versions 1.0 of FlexOS 386 (for hosts) and FlexOS 186 (for remote cell controllers). FlexOS 386 provided a windowing feature, and offered PC DOS 3.2 and GEM compatibility. FlexOS 286 and FlexOS 386 versions 2.0 were registered on 3 July 1989. Among the major FlexOS customers in 1990/1991 were FANUC, IBM, ICL, Nixdorf, Siemens, TEC, Thorn EMI Software and Micrologic. Novell bought Digital Research for  million in July 1991. X/GEM for FlexOS release 1.0 (a.k.a. X/GEM FlexOS 286 and 386) and FlexNet were registered on 21 December 1992. FlexOS was used as the primary test platform for the new Novell Embedded Systems Technology (NEST). When Novell decided to abandon further development of the various Digital Research operating systems such as Multiuser DOS (a successor to Concurrent DOS) and Novell DOS (a successor to DR DOS), they sold FlexOS off to the Santa Clara, California-based Integrated Systems, Inc. (ISI) for  million in July 1994. The deal comprised a direct payment of half this sum as well as shares representing 2% of the company. The company already had pSOS+, another modular real-time multitasking operating system for embedded systems, but they continued to maintain FlexOS as well. FlexOS version 2.33 was current as of May 1998 and with FlexOS 2.34 to be released soon after with added support for faster CPUs, 64 MB of memory, EIDE and ATAPI CDROM drives. Integrated Systems was bought by their competitor Wind River Systems in February 2000. Commands The following list of commands is supported by FlexOS: ASSIGN BACK BACKUP BREAK CANCEL CHDIR CHKDSK COMMAND COMP CONFIG COPY CTTY DATE DEFINE DIR DISKCOMP DISKCOPY DISKSET ERASE EXIT FDISK FIND FORMAT FSET LIST LOGOFF LOGON MKDIR MORE ORDER PASSWORD PATH PRINT PROCESS PROMPT RECDIR RECFILE RENAME RESTORE RMDIR SECURITY SORT SYS TIME TREE TYPE VER VOL Versions Known FlexOS versions include: Motorola 68000 / Freescale/NXP ColdFire MCF5251 platform: Concurrent DOS 68K 1.0 (1985) Concurrent DOS 68K 1.1 Concurrent DOS 68K 1.20 (April 1986, 1986-05-27) Concurrent DOS 68K 1.21 (1986) FlexOS 68K 1.x? Intel 80286 platform: MP/M-286 (1982) Concurrent CP/M-286 (1985) Concurrent DOS 286 preview (1985-01) Concurrent DOS 286 1.0 (1985-08-06) Concurrent DOS 286 1.0.01 (1985-08-18/1985-08-21) Concurrent DOS 286 1.0.02 (1985-08-22/1985-09-12) Concurrent DOS 286 1.0.03 (1985-09-10/1985-09-12) Concurrent DOS 286 1.0.04 (1985-09-17) Concurrent DOS 286 1.0.05 (1985-11-01) Concurrent DOS 286 1.0.06 (1985-12-10) Concurrent DOS 286 1.1 (1986-01-07) Concurrent DOS 286 1.2 (1986) Concurrent DOS 286 1.2.00 (1986-04-10/1986-04-24) Concurrent DOS 286 1.2.01 (1986-04-16/1986-05-19) Concurrent DOS 286 1.2.02 (1986-08-18) FlexOS 286 1.3 (November 1986) FlexOS 286 1.31 (May 1987) FlexOS 286 1.5 (1988-02-29) FlexOS 286 2.0.00 (1988-03-31) FlexOS 286 2.0 (July 1989) FlexOS 286 2.32 (July 1993) Intel 80186/NEC V20/V30 platform: FlexOS 186 (1986-09-04 forked) FlexOS 186 1.0 (June 1987) Intel 80386 platform: FlexOS 386 1.0 (June 1987) FlexOS 386 2.0 (July 1989) FlexOS 386 2.30? FlexOS 386 2.31? FlexOS 386 2.32 (July 1993) FlexOS 386 2.33 (May 1998) FlexOS 386 2.34 (planned for 1999) NEC V60 platform: Concurrent DOS V60? Adaptations IBM 4680 OS Named IBM 4680 OS Version 1, IBM originally chose DR Concurrent DOS 286 as the basis of their IBM 4680 computer for IBM Plant System products and Point-of-Sale terminals in 1986. The last release of the IBM 4680 OS has been Version 4, before it was replaced by IBM 4690 Version 1. Versions: IBM 4680 Operating System Version 1 Release 1 IBM 4680 Operating System Version 1 Release 2 IBM 4680 Operating System Version 1 Release 3 IBM 4680 Operating System Version 2 Release 1 IBM 4680 Operating System Version 3 Release 1 IBM 4680 Operating System Version 4 Release 1 IBM and Toshiba 4690 OS In July 1993, IBM announced the adoption of FlexOS version 2.32 as the basis of their IBM 4690 OS Version 1, to be pre-released on 24 September 1993 and generally made available from 25 March 1994. FlexOS 2.32 supported 286 and 386 modes, had more efficient memory management, better console and pipe systems, and brought overall quality and performance improvements compared to the version that came with IBM 4680 OS Version 4. Further, it removed limits on the number of applications running concurrently due to its more efficient use of KOSPOOL. In order to support Java IBM 4690 OS Version 2 brought support for long filenames by means of a virtual filesystem (VFS) architecture and it introduced FAT32 volumes. According to "The Year of the Store?", IHL Consulting Group/RIS News, IBM 4690 OS still had a market share of 12% in the POS register/client market in June 2005, when IBM was starting to phase it out in favour to IBM Retail Environment for SUSE (IRES). IBM continued to maintain 4690 OS up to April 2015, with the most recent version released by IBM in May 2012 being IBM 4690 OS Version 6 Release 3. Toshiba released Toshiba 4690 OS Version 6 Release 4 in January 2014 and Version 6 Release 5 in January 2016. Siemens S5-DOS/MT Siemens used and still maintains FlexOS in their factory automation equipment as well. For example, their Simatic S5 STEP-5 operating system S5-DOS/MT is based on FlexOS 386 with X/GEM, FlexNet and Btrieve, whereas the smaller S5-DOS system, also present on these systems, is a variant of Digital Research's Personal CP/M-86. Siemens industrial systems like COROS LS-B/FlexOS, COROS OS-B/FlexOS, GRACIS/FlexOS, OS-525 were FlexOS and X/GEM-based. Computers such as the PC 16-20 and the PC 32 series were available with FlexOS as well. CTM The Japanese post office shared terminals III and CTM IV were based on FlexOS. See also Concurrent DOS 286 GEM IBM 4683 IBM 4690 OS IBM 4694 pSOS Distributed Data Management Architecture (DDM) Electronic point of sale (EPOS) References Further reading Concurrent DOS 286, FlexOS, IBM 4690 CP/M variants Disk operating systems DOS variants Digital Research operating systems Novell operating systems Microcomputer software Real-time operating systems Embedded operating systems Discontinued operating systems C (programming language) software

Operating System (OS)

Lenovo System x System x is a line of x86 servers produced by IBM – and later by Lenovo – as a sub-brand of IBM's System brand, alongside IBM Power Systems, IBM System z and IBM System Storage. In addition, IBM System x was the main component of the IBM System Cluster 1350 solution. In January 2014, IBM announced the sale of its x86 server business to Lenovo for $2.3 billion, in a sale completed October 1, 2014. History Starting out with the PS/2 Server, then the IBM PC Server, rebranded Netfinity, then eServer xSeries and finally System x, these servers are distinguished by being based on off-the-shelf x86 CPUs; IBM positioned them as their "low end" or "entry" offering compared to their POWER and Mainframe products. Previously IBM servers based on AMD Opteron CPUs did not share the xSeries brand; instead they fell directly under the eServer umbrella. However, later AMD Opteron-based servers did fall under the System x brand. Predecessors IBM PS/2 Server IBM PS/2 Server 85 (Type 9585), 1992 IBM PS/2 Server 95 (Types 8595, 9595, 9595A), 1990–1992 IBM PS/2 Server 195, 1993 IBM PS/2 Server 295, 1992 IBM PC Server PC Server range IBM PC Server 300, 1994 IBM PC Server 310 (PCI/ISA), 1996 IBM PC Server 315 (PCI/ISA), 1996 IBM PC Server 320 (PCI/EISA), 1996 IBM PC Server 325 (PCI/EISA), 1996 IBM PC Server 330 (PCI/EISA), 1997 IBM PC Server 500 (MCA), 1994 IBM PC Server 520 (PCI/EISA or PCI/MCA), 1995-1996 IBM PC Server 704 (PCI/EISA), 1996 IBM PC Server 720 (PCI/MCA), 1995-1996 Numbering scheme 300 range for high-volume, entry level servers 500 range for midrange 700 range for high-end. IBM Netfinity 1998–2001 server line; Not to be confused with a software IBM product with a similar name, NetFinity (notice the capital F). Netfinity range IBM Netfinity 1000 IBM Netfinity 3000, 3500 IBM Netfinity 4000R, 4500R IBM Netfinity 5000, 5100, 5500, 5500-M10, 5500-M20, 5600 IBM Netfinity 6000R IBM Netfinity 7000, 7000-M10, 7100, 7600 IBM Netfinity 8500R Numbering scheme The numbering scheme started off similar to that of the IBM PC Servers, but additional ranges were added, like the entry-level 1000 model later on. Models ending with an R, are rack-mount. KVM cabling scheme Some Netfinity servers used IBM's C2T cabling scheme for Keyboard/Video/Mouse. IBM eServer IBM eServer range IBM eServer was a marketing effort to put all of the diverse IBM server platforms under one header. The AS/400 became the IBM eServer iSeries, the RS/6000 became the IBM eServer pSeries, the S/390 mainframe became the IBM eServer zSeries and the Intel processor based IBM Netfinity servers became the IBM eServer xSeries. A few exceptions were however made IBM eServer 325, 326, 326m IBM eServer BladeCenter, BladeCenter T, BladeCenter H, BladeCenter HT Numbering scheme For marketing reasons the AMD processor based e325, e326 and e326m and the BladeCenter which supports non-Intel processor products were not branded xSeries, but were instead placed directly under the eServer brand. The xSeries brand was limited to only Intel-based server products. From a numbering perspective the AMD servers did fit into the xSeries range, under the similar x335 and x336 Intel processor products. These numbers were not re-used in the xSeries range to prevent confusion. IBM eServer xSeries While most servers used Intel x86 (IA32) processors, the x380, x382, x450 and x455 used the Intel Itanium (IA64) processor. xSeries range IBM eServer xSeries 100, 130, 135, 150 IBM eServer xSeries 200, 205, 206, 206m, 220, 225, 226, 230, 232, 235, 236, 240, 250, 255, 260 IBM eServer xSeries 300, 305, 306, 306m, 330, 335, 336, 340, 342, 345, 346, 350, 360, 365, 366, 370, 380, 382 IBM eServer xSeries 440, 445, 450, 455, 460 Numbering scheme 100 series are entry-level tower servers 200 series are tower servers 300 series are rack-mount servers 400 series are rack-mount scalable servers KVM cabling scheme Many xSeries servers used IBM's C2T cabling scheme for Keyboard/Video/Mouse. System x IBM System x range IBM System x3105, x3100, x3100 M3, x3100 M4, x3100 M5 IBM System x3200, x3200 M2, x3200 M3, x3250, x3250 M2, x3250 M3, x3250 M4, x3250 M5, x3250 M6 IBM System x3300 M3, x3300 M4 IBM System x3350 IBM System x3400, x3400 M2, x3400 M3, x3450, x3455 IBM System x3500, x3500 M2, x3500 M3, x3500 M4 IBM System x3530 M3, x3530 M4 IBM System x3550, x3550 M2, x3550 M3, x3550 M4, x3550 M5 IBM System x3620 M3 IBM System x3630 M3, x3630 M4 IBM System x3650, x3650T, x3655, x3650 M2, x3650 M3, x3650 M4, x3650 M4 HD, x3650 M4 BD, 3650 M5 IBM System x3690 X5 IBM System x3750 M4 IBM System x3755, x3755 M3 IBM System x3800, x3850, x3850 M2, x3850 X5, x3850 X6 IBM System x3950, x3950 M2, x3950 X5, x3950 X6 Lenovo System x range These systems are effectively the same as the previous IBM branded models, but with a Lenovo badge. Lenovo System x3100 M5 Lenovo System x3250 M5, x3250 M6 Lenovo System x3500 M5 Lenovo System x3550 M4, x3550 M5 Lenovo System x3650 M4, x3650 M5 Lenovo System x3850 X6 Lenovo System x3950 X6 Lenovo NextScale Lenovo FlexSystem Lenovo also had its own ThinkServer family of Intel servers. This family is technically less advanced than System x. At the time of this writing, System x is being discontinued and replaced by the Lenovo ThinkSystem family of Intel servers. Enterprise eX5 architecture Enterprise X4 architecture Numbering scheme 2nd digit increments to show capability 3rd digit is a 0 for tower models, and 5 for rack-mount 4th digit is a 0 for Intel processors, and 5 for AMD Opteron. Models with a T at the end are meant for Telco purposes. IBM iDataPlex IBM System x iDataPlex, introduced in 2008, was used by many TOP500 supercomputers (as part of IBM Intelligent Cluster), including SuperMUC, Yellowstone and Stampede. Other smaller installations included SciNet Consortium's General Purpose Cluster It is an unusual form-factor in that you have two columns of 19" rack servers side-by-side in a single rack. This rack, unlike traditional racks, however was very shallow which is where the space saving came from for large installations. As such it only supports specially designed shallow servers. It was typically deployed in combination with a Rear Door Heat Exchanger (RDHx) to cool the exhaust heat with water. It was replaced with IBM NeXtScale in 2014. Components iDataPlex could be ordered as preconfigured rack tower (System x iDataPlex Rack with optional Rack management appliance), or as independent nodes. Rack iDataPlex 100U rack — compact dual rack ((1200x600mm footprint — instead of standard 1280x1050 (2x 42U rack)) Chassis System x iDataPlex 2U Flex chassis System x iDataPlex 3U Flex chassis — same as 2U with another coolers and additional storage. Chassis also compatible with standard racks (with another rails). Nodes 1U blade servers. System x iDataPlex dx320 — 20?? System x iDataPlex dx340 — 20?? System x iDataPlex dx360 M1 — 2008, System x iDataPlex dx360 M2 — 2009, System x iDataPlex dx360 M3 — 201?, System x iDataPlex dx360 M4 — 2013, See also List of IBM products iDataCool — watercooled version of iDataPlex References System x Divested IBM products System x

Operating System (OS)

Windows 7 editions Windows 7, a major release of the Microsoft Windows operating system, has been released in several editions since its original release in 2009. Only Home Premium, Professional, and Ultimate were widely available at retailers. The other editions focus on other markets, such as the software development world or enterprise use. All editions support 32-bit IA-32 CPUs and all editions except Starter support 64-bit x64 CPUs. 64-bit installation media are not included in Home-Basic edition packages, but can be obtained separately from Microsoft. According to Microsoft, the features for all editions of Windows 7 are stored on the machine, regardless of which edition is in use. Users who wish to upgrade to an edition of Windows 7 with more features were able to use Windows Anytime Upgrade to purchase the upgrade and to unlock the features of those editions, until it was discontinued in 2015. Microsoft announced Windows 7 pricing information for some editions on June 25, 2009, and Windows Anytime Upgrade and Family Pack pricing on July 31, 2009. Main editions Mainstream support for all Windows 7 editions ended on January 13, 2015, and extended support ended on January 14, 2020. Professional and Enterprise volume licensed editions have paid Extended Security Updates (ESU) available until at most January 10, 2023. Since October 31, 2013, Windows 7 is no longer available in retail, except for remaining stocks of the preinstalled Professional edition, which was officially discontinued on October 31, 2016. Windows 7 Starter is the edition of Windows 7 that contains the fewest features. It is only available in a 32-bit version and does not include the Windows Aero theme. The desktop wallpaper and visual styles (Windows 7 Basic) are not user-changeable. In the release candidate versions of Windows 7, Microsoft intended to restrict users of this edition to running three simultaneous programs, but this limitation was dropped in the final release. This edition does not support more than 2 GB of RAM. This edition was available pre-installed on computers, especially netbooks or Windows Tablets, through system integrators or computer manufacturers using OEM licenses. Windows 7 Home Basic was available in "emerging markets", in 141 different countries. Some Windows Aero options are excluded along with several new features. This edition is available in both 32-bit and 64-bit versions and supports up to 8 GB of RAM. Home Basic, along with other editions sold in emerging markets, includes geographical activation restriction, which requires users to activate Windows within a certain region or country. This edition contains features aimed at the home market segment, such as Windows Media Center, Windows Aero and multi-touch support. It was available in both 32-bit and 64-bit versions. This edition is targeted towards enthusiasts, small-business users, and schools. It includes all the features of Windows 7 Home Premium, and adds the ability to participate in a Windows Server domain. Additional features include support for up to 192 GB of RAM (increased from 16 GB), operating as a Remote Desktop server, location aware printing, backup to a network location, Encrypting File System, Presentation Mode, Software Restriction Policies (but not the extra management features of AppLocker) and Windows XP Mode. It was available in both 32-bit and 64-bit versions. This edition targeted the enterprise segment of the market and was sold through volume licensing to companies which have a Software Assurance (SA) contract with Microsoft. Additional features include support for Multilingual User Interface (MUI) packages, BitLocker Drive Encryption, and UNIX application support. Not available through retail or OEM channels, this edition is distributed through SA. As a result it includes several SA-only benefits, including a license allowing the operating of diskless nodes (diskless PCs) and activation via Volume License Key (VLK). Windows 7 Ultimate contains the same features as Windows 7 Enterprise, but this edition was available to home users on an individual license basis. For a while, Windows 7 Home Premium and Windows 7 Professional users were able to upgrade to Windows 7 Ultimate for a fee using Windows Anytime Upgrade if they wished to do so, but this service was stopped in 2015. Unlike Windows Vista Ultimate, the Windows 7 Ultimate does not include the Windows Ultimate Extras feature or any exclusive features as Microsoft had stated. Special-purpose editions The main editions also can take the form of one of the following special editions: The features in the N and KN Editions are the same as their equivalent full versions, but do not include Windows Media Player or other Windows Media-related technologies, such as Windows Media Center and Windows DVD Maker due to limitations set by the European Union and South Korea, respectively. The cost of the N and KN Editions are the same as the full versions, as the Media Feature Pack for Windows 7 N or Windows 7 KN can be downloaded without charge from Microsoft. Upgrade editions In-place upgrade from Windows Vista with Service Pack 1 to Windows 7 is supported if the processor architecture and the language are the same and their editions match (see below). In-place upgrade is not supported for earlier versions of Windows; moving to Windows 7 on these machines requires a clean installation, i.e. removal of the old operating system, installing Windows 7 and reinstalling all previously installed programs. Windows Easy Transfer can assist in this process. Microsoft made upgrade SKUs of Windows 7 for selected editions of Windows XP and Windows Vista. The difference between these SKUs and full SKUs of Windows 7 is their lower price and proof of license ownership of a qualifying previous version of Windows. Same restrictions on in-place upgrading applies to these SKUs as well. In addition, Windows 7 is available as a Family Pack upgrade edition in certain markets, to upgrade to Windows 7 Home Premium only. It gives licenses to upgrade three machines from Vista or Windows XP to the Windows 7 Home Premium edition. These are not full versions, so each machine to be upgraded must have one of these qualifying previous versions of Windows for them to work. In the United States, this offer expired in early December 2009. In October 2010, to commemorate the anniversary of Windows 7, Microsoft once again made Windows 7 Home Premium Family Pack available for a limited time, while supplies lasted. Upgrade compatibility There are two possible ways to upgrade to Windows 7 from an earlier version of Windows: An in-place install (labelled "Upgrade" in the installer), where settings and programs are preserved from an older version of Windows. This option is only sometimes available, depending on the editions of Windows being used, and is not available at all unless upgrading from Windows Vista. A clean install (labelled "Custom" in the installer), where all settings including but not limited to user accounts, applications, user settings, music, photos, and programs are erased entirely and the current operating system is erased and replaced with Windows 7. This option is always available and is required for all versions of Windows XP. The table below lists which upgrade paths allow for an in-place install. Note that in-place upgrades can only be performed when the previous version of Windows is of the same architecture. If upgrading from a 32-bit installation to a 64-bit installation or downgrading from 64-bit installation to 32-bit installation, a clean install is mandatory regardless of the editions being used. Anytime Upgrade editions Until the year 2015, Microsoft also supported in-place upgrades from a lower edition of Windows 7 to a higher one, using the Windows Anytime Upgrade tool. There are currently three retail options available (though it is currently unclear whether they can be used with previous installations of the N versions). There are no family pack versions of the Anytime Upgrade editions. It was possible to use the Product Key from a Standard upgrade edition to accomplish an in-place upgrade (e.g. Home Premium to Ultimate). Starter to Home Premium Starter to Professional1 Starter to Ultimate1 Home Premium to Professional Home Premium to Ultimate Professional to Ultimate1 1 Available in retail, and at the Microsoft Store Derivatives On February 9, 2011, Microsoft announced Windows Thin PC, a branded derivative of Windows Embedded Standard 7 with Service Pack 1, designed as a lightweight version of Windows 7 for installation on low performance PCs as an alternative to using a dedicated thin client device. It succeeded Windows Fundamentals for Legacy PCs, which was based on Windows XP Embedded. Windows Thin PC was released on June 6, 2011. Windows 7 is also currently available in two forms of Windows Embedded, named as Windows Embedded Standard 7 (known as Windows Embedded Standard 2011 prior to release, the newest being Windows Embedded Standard 7 with Service Pack 1) and Windows Embedded POSReady 7. Both versions are eligible for Extended Security Updates (ESU) for up to three years after their end of extended support dates. Comparison chart See also Windows 2000 editions Windows XP editions Windows Vista editions Windows 8 editions Windows 10 editions Notes References Further reading Windows 7

Operating System (OS)

RTLinux RTLinux is a hard realtime real-time operating system (RTOS) microkernel that runs the entire Linux operating system as a fully preemptive process. The hard real-time property makes it possible to control robots, data acquisition systems, manufacturing plants, and other time-sensitive instruments and machines from RTLinux applications. The design was patented. Despite the similar name, it is not related to the Real-Time Linux project of the Linux Foundation. which is for soft real-time. RTLinux was developed by Victor Yodaiken, Michael Barabanov, Cort Dougan and others at the New Mexico Institute of Mining and Technology and then as a commercial product at FSMLabs. Wind River Systems acquired FSMLabs embedded technology in February 2007 and made a version available as Wind River Real-Time Core for Wind River Linux. As of August 2011, Wind River has discontinued the Wind River Real-Time Core product line, effectively ending commercial support for the RTLinux product. Background The key RTLinux design objective was to add hard real-time capabilities to a commodity operating system to facilitate the development of complex control programs with both capabilities. For example, one might want to develop a real-time motor controller that used a commodity database and exported a web operator interface. Instead of attempting to build a single operating system that could support real-time and non-real-time capabilities, RTLinux was designed to share a computing device between a real-time and non-real-time operating system so that (1) the real-time operating system could never be blocked from execution by the non-real-time operating system and (2) components running in the two different environments could easily share data. As the name implies RTLinux was originally designed to use Linux as the non-real-time system but it eventually evolved so that the RTCore real-time kernel could run with either Linux or Berkeley Software Distribution (BSD) Unix. Multi-Environment Real-Time (MERT) was the first example of a real-time operating system coexisting with a Unix system. MERT relied on traditional virtualization techniques: the real-time kernel was the host operating system (or hypervisor) and Bell Systems Unix was the guest. RTLinux was an attempt to update the MERT concept to the PC era and commodity hardware. It was also an attempt to also overcome the performance limits of MERT, particularly the overhead introduced by virtualization. Instead of encapsulating the guest OS in a virtual machine, RTLinux virtualized only the guest interrupt control. This method allowed the real-time kernel to convert the guest operating system into a system that was completely preemptible but that could still directly control, for example, storage devices. In particular, standard drivers for the guest worked without source modification although they needed to be recompiled to use the virtualization "hooks". See also paravirtualization. The Unix pipe was adapted to permit real-time and non-real-time programs to communicate, although other methods such as shared memory were also added. From the programmer's point of view, RTLinux originally looked like a small threaded environment for real-time tasks plus the standard Linux environment for everything else. The real-time operating system was implemented as a loadable kernel module which began by virtualizing guest interrupt control and then started a real-time scheduler. Tasks were assigned static priorities and scheduling was originally purely priority driven. The guest operating system was incorporated as the lowest priority task and essentially acted as the idle task for the real-time system. Real-time tasks ran in kernel mode. Later development of RTLinux adopted the Portable Operating System Interface (POSIX) POSIX threads application programming interface (API) and then permitted creation of threads in user mode with real-time threads running inside guest processes. In multiprocessor environments threads were locked to processor cores and it was possible to prevent the guest thread from running on designated core (effectively reserving cores for only real-time processing). Implementation RTLinux provides the ability to run special real-time tasks and interrupt handlers on the same machine as standard Linux. These tasks and handlers execute when they need to execute no matter what Linux is doing. The worst case time between the moment a hardware interrupt is detected by the processor and the moment an interrupt handler starts to execute is under 15 microseconds on RTLinux running on a generic x86 (circa 2000). A RTLinux periodic task runs within 35 microseconds of its scheduled time on the same hardware. These times are hardware limited, and as hardware improves RTLinux will also improve. Standard Linux has excellent average performance and can even provide millisecond level scheduling precision for tasks using the POSIX soft real-time capabilities. Standard Linux is not, however, designed to provide sub-millisecond precision and reliable timing guarantees. RTLinux was based on a lightweight virtual machine where the Linux "guest" was given a virtualized interrupt controller and timer, and all other hardware access was direct. From the point of view of the real-time "host", the Linux kernel is a thread. Interrupts needed for deterministic processing are processed by the real-time core, while other interrupts are forwarded to Linux, which runs at a lower priority than real-time threads. Linux drivers handled almost all I/O. First-In-First-Out pipes (FIFO) or shared memory can be used to share data between the operating system and RTLinux. Objective The key RTLinux design objective is that the system should be transparent, modular, and extensible . Transparency means that there are no unopenable black boxes and the cost of any operation should be determinable. Modularity means that it is possible to omit functionality and the expense of that functionality if it is not needed. And extensibility means that programmers should be able to add modules and tailor the system to their requirements. The base RTLinux system supports high speed interrupt handling and no more. It has simple priority scheduler that can be easily replaced by schedulers more suited to the needs of some specific application. When developing RTLinux, it was designed to maximize the advantage we get from having Linux and its powerful capabilities available. Core components RTLinux is structured as a small core component and a set of optional components. The core component permits installation of very low latency interrupt handlers that cannot be delayed or preempted by Linux itself and some low level synchronization and interrupt control routines. This core component has been extended to support SMP and at the same time it has been simplified by removing some functionality that can be provided outside the core. Functions Most RTLinux functions are in a set of loadable kernel modules that provide optional services and levels of abstraction. These modules include: rtl sched - a priority scheduler that supports both a "lite POSIX" interface described below and the original V1 RTLinux API. rtl time - which controls the processor clocks and exports an abstract interface for connecting handlers to clocks. rtl posixio - supports POSIX style read/write/open interface to device drivers. rtl fifo - connects RT tasks and interrupt handlers to Linux processes through a device layer so that Linux processes can read/write to RT components. semaphore - a contributed package by Jerry Epplin which gives RT tasks blocking semaphores. POSIX mutex support is planned to be available in the next minor version update of RTLinux. mbuff is a contributed package written by Tomasz Motylewski for providing shared memory between RT components and Linux processes. Realtime tasks RTLinux realtime tasks get implemented as kernel modules similar to the type of module that Linux uses for drivers, file systems, and so on. Realtime tasks have direct access to the hardware and do not use virtual memory. On initialization, a realtime task (module) informs the RTLinux kernel of its deadline, period, and release-time constraints. Threads RT-Linux implements a POSIX API for a thread's manipulation. A thread is created by calling the pthread_create function. The third parameter of pthread_create is a function which contains the code executed by the thread. It is necessary to set thread priorities in RTLinux. Threads with higher priorities can preempt threads with lower priorities. For example, we can have a thread controlling a stepper motor. In order to move the motor fluently, it is necessary to start this thread in strictly regular intervals. This can be guaranteed by assigning a high priority to this thread. The example threads2.c sets different thread priorities. Setting of thread priority is done by code shown below: int init_module(void) { pthread_attr_t attr; struct sched_param param; pthread_attr_init(&attr); param.sched_priority = 1; pthread_attr_setschedparam(&attr, &param); pthread_create(&t1, &attr, &thread_code, "this is thread 1"); rtl_printf("Thread 1 started\n"); ... } The output the program is as follows. Thread 1 started Thread 2 started Thread 3 started Message: this is thread 1 Message: this is thread 2 Message: this is thread 2 Message: this is thread 2 Message: this is thread 1 Message: this is thread 1 Message: this is thread 3 Message: this is thread 3 Message: this is thread 3 The thread 2 has the highest priority and the thread 3 has the lowest priority. The first message is printed by the middle priority thread 1 because it is started a short time before the thread 2. See also RTAI. RTAI began as a variant of RTLinux called "MyRTlinux" and in later releases was claimed by its authors not to use the patented RTLinux virtualization technique. RMX (operating system) SCHED_DEADLINE Xenomai Preemption (computing) Linux on embedded systems Real-time testing References Sources Dougan, Cort (2004), "Precision and predictability for Linux and RTLinuxPro", Dr. Dobbs Journal, February 1, 2004 Yodaiken,Victor (1997), US Patent 5,995,745 External links Article about RTLinux synchronization A Real-Time Linux. Victor Yodaiken and Michael Barabanov, New Mexico Institute of Technology Linux kernel variant Real-time operating systems

Operating System (OS)

TOPS (file server) TOPS (Transcendental OPerating System) is a peer-to-peer LAN-based file sharing system best known in its Macintosh implementation, but also available for DOS and able to interoperate with Unix's NFS. Originally written by Centram Systems West, the company was purchased by Sun Microsystems as part of Sun's development of the NFS ecosystem. The Centram company was renamed to TOPS after its acquisition by Sun. Sales of TOPS dried up after the introduction of System 7, which featured a similar file sharing system built-in, and Sun spun off their NFS developments to Sitka. Early versions TOPS was implemented in the 1980s, an era where each computer system featured its own networking protocol and were generally unable to talk to each other. At the time Apple was in the midst of the Macintosh Office effort, and was working with two external companies to develop the Apple Filing Protocol (AFP), built on top of AppleTalk. The Macintosh Office effort ultimately failed, and one of the two companies, Centram, decided to implement a similar system on their own. This became the first version of TOPS. When TOPS was originally released there was no peer-to-peer file sharing solution on the Mac. According to PC Magazine, connecting a Mac to an Apple LaserWriter printer was the initial intended function of AppleTalk. Apple's own file sharing solution, AppleShare, was not released until later, and unlike TOPS it required a dedicated server machine to run on, at least a Mac Plus. For smaller offices TOPS was an attractive low-cost solution, and saw relatively widespread use. Even after the introduction of AppleShare, TOPS managed to hold on to an estimated 600,000 client installs. TOPS was initially a protocol using a custom set of remote procedure calls and able to talk only between TOPS clients. PCs generally lacked networking of any sort, and Centram addressed this problem by introducing a line of LocalTalk cards for the PC, along with a TOPS client. Files could be exchanged between the two computers, with filename conversion as required. FlashTalk Centram later introduced the "FlashTalk" networking system that used external clocking to improve LocalTalk performance. The Zilog SCC powering the serial ports on the Mac used an internal 3.6864 MHz clock that could then be divided down to provide different standard bit rates. The fastest rate available internally was 230.4 kbit/s, used by LocalTalk. However, the system also allowed the clock to be read from a pin in the serial port, giving rise to the possibility of faster speeds with the right external equipment. FlashTalk combined a conventional LocalTalk-like dongle with a clocking source and an external power supply. Using these connectors, and the associated software, TOPS could run at 770 kbit/s. This was not only a fairly dramatic improvement over LocalTalk, but also relatively speedy overall in an era when 1 Mbit/s networks were still common. TCP/IP Support After the Sun purchase, TOPS was given the problem of making a client that could also access Sun file shares using NFS. Centram solved this problem by porting their file sharing protocol to TCP/IP. This was not trivial; neither Mac OS nor Windows supported TCP/IP "out of the box", so what was now the TOPS Division of Sun had to write a complete IP stack for the Mac and Windows. Centram had already written such a stack for their "TOPS Terminal", a freeware (but not open source) Telnet terminal for the Mac. Additionally, the majority of Macintosh systems used LocalTalk (or PhoneNet) for connectivity, and could not be directly connected to the Ethernet-based Unix LANs. They worked around this problem by supporting an emerging LocalTalk-to-Ethernet bridging standard known as "KIP", short for Kinetics Internet Protocol. KIP encapsulated TCP/IP packets inside AppleTalk packets, allowing them to be sent over existing LocalTalk connections. Dedicated KIP-supporting network bridges were available that stripped off the AppleTalk packaging, re-formed the IP packets inside, and sent them out over Ethernet. One limitation of the TCP stack was that it did not support DNS, requiring users to type in IP addresses of the peers they wanted to communicate with. In a network of mostly Macs or Windows PCs this was not an issue, as DNS was not widely used with these systems at that time. KIP also reduced the need for DNS, as it allowed a Mac's existing Address Resolution Protocol (AARP) code within AppleTalk to look up the AppleTalk address of the remote peer, and then communicate with the TOPS stack on that machine to find the corresponding IP address. TOPS also added the new "InBox Personal Connection" e-mail system, first developed by Symantec. Decline TOPS' attractiveness was seriously eroded with the introduction of System 7 in 1991. TOPS had initially competed against the dedicated-server AppleShare, but System 7 included a file sharing server built-in, one that proved to be much faster than then-current versions of TOPS. TOPS sales dwindled and Sun spun off the division as Sitka, before closing it entirely in 1993. See also MacServe Macintosh Office References Network file systems Sun Microsystems software Macintosh platform 1986 software Computer-related introductions in 1986

Operating System (OS)

CDC Kronos Kronos is an operating system with time-sharing capabilities, written by Control Data Corporation in the 1970s. Kronos ran on the 60-bit CDC 6000 series mainframe computers and their successors. CDC replaced Kronos with the NOS operating system in the late 1970s, which were succeeded by the NOS/VE operating system in the mid-1980s. The MACE operating system and APEX were forerunners to KRONOS. It was written by Control Data systems programmer Greg Mansfield, Dave Cahlander, Bob Tate and three others. See also CDC SCOPE (software) References KRONOS Discontinued operating systems Time-sharing operating systems

Operating System (OS)

STOS STOS may refer to: STOS BASIC, a programming language for the Atari ST computer stos, an opcode mnemonic in X86 assembly language Secure Trusted Operating System Consortium Štós, a village in Slovakia See also ST:TOS, an abbreviation for Star Trek: The Original Series (ST:OS) STO (disambiguation) for the singular of STOs

Operating System (OS)

Process state In a multitasking computer system, processes may occupy a variety of states. These distinct states may not be recognized as such by the operating system kernel. However, they are a useful abstraction for the understanding of processes. Primary process states The following typical process states are possible on computer systems of all kinds. In most of these states, processes are "stored" on main memory. Created When a process is first created, it occupies the "created" or "new" state. In this state, the process awaits admission to the "ready" state. Admission will be approved or delayed by a long-term, or admission, scheduler. Typically in most desktop computer systems, this admission will be approved automatically. However, for real-time operating systems this admission may be delayed. In a realtime system, admitting too many processes to the "ready" state may lead to oversaturation and overcontention of the system's resources, leading to an inability to meet process deadlines. Ready A "ready" or "waiting" process has been loaded into main memory and is awaiting execution on a CPU (to be context switched onto the CPU by the dispatcher, or short-term scheduler). There may be many "ready" processes at any one point of the system's execution—for example, in a one-processor system, only one process can be executing at any one time, and all other "concurrently executing" processes will be waiting for execution. A ready queue or run queue is used in computer scheduling. Modern computers are capable of running many different programs or processes at the same time. However, the CPU is only capable of handling one process at a time. Processes that are ready for the CPU are kept in a queue for "ready" processes. Other processes that are waiting for an event to occur, such as loading information from a hard drive or waiting on an internet connection, are not in the ready queue. Running A process moves into the running state when it is chosen for execution. The process's instructions are executed by one of the CPUs (or cores) of the system. There is at most one running process per CPU or core. A process can run in either of the two modes, namely kernel mode or user mode. Kernel mode Processes in kernel mode can access both: kernel and user addresses. Kernel mode allows unrestricted access to hardware including execution of privileged instructions. Various instructions (such as I/O instructions and halt instructions) are privileged and can be executed only in kernel mode. A system call from a user program leads to a switch to kernel mode. User mode Processes in user mode can access their own instructions and data but not kernel instructions and data (or those of other processes). When the computer system is executing on behalf of a user application, the system is in user mode. However, when a user application requests a service from the operating system (via a system call), the system must transition from user to kernel mode to fulfill the request. User mode avoids various catastrophic failures: There is an isolated virtual address space for each process in user mode. User mode ensures isolated execution of each process so that it does not affect other processes as such. No direct access to any hardware device is allowed. Blocked A process transitions to a blocked state when it cannot carry on without an external change in state or event occurring. For example, a process may block on a call to an I/O device such as a printer, if the printer is not available. Processes also commonly block when they require user input, or require access to a critical section which must be executed atomically. Such critical sections are protected using a synchronization object such as a semaphore or mutex. Terminated A process may be terminated, either from the "running" state by completing its execution or by explicitly being killed. In either of these cases, the process moves to the "terminated" state. The underlying program is no longer executing, but the process remains in the process table as a zombie process until its parent process calls the wait system call to read its exit status, at which point the process is removed from the process table, finally ending the process's lifetime. If the parent fails to call wait, this continues to consume the process table entry (concretely the process identifier or PID), and causes a resource leak. Additional process states Two additional states are available for processes in systems that support virtual memory. In both of these states, processes are "stored" on secondary memory (typically a hard disk). Swapped out and waiting (Also called suspended and waiting.) In systems that support virtual memory, a process may be swapped out, that is, removed from main memory and placed on external storage by the scheduler. From here the process may be swapped back into the waiting state. Swapped out and blocked (Also called suspended and blocked.) Processes that are blocked may also be swapped out. In this event the process is both swapped out and blocked, and may be swapped back in again under the same circumstances as a swapped out and waiting process (although in this case, the process will move to the blocked state, and may still be waiting for a resource to become available). See also ps (Unix) References Particularly chapter 3, section 3.2, "process states", including figure 3.9 "process state transition with suspend states" Process (computing)

Operating System (OS)

OCS Inventory Open Computer and Software Inventory Next Generation (OCS inventory NG) is free software that enables users to inventory IT assets. OCS-NG collects information about the hardware and software of networked machines running the OCS client program ("OCS Inventory Agent"). OCS can visualize the inventory through a web interface. Furthermore, OCS includes the capability of deploying applications on computers according to search criteria. Agent-side IpDiscover makes it possible to discover the entirety of networked computers and devices. History The open-source OCS Inventory NG project started in late 2005 and produced its first release version of OCS Inventory in early 2007. Since version 1.0rc3, most of OCS Inventory functionality can be adapted or extended via a module system. Operation The dialogue between OCS client machines and the server depends on the Hypertext Transfer Protocol (HTTP). The software formats data in XML. The management server uses Apache, MySQL and Perl. OCS runs on multiple platforms: under Unixes and under Microsoft Windows (95 or later). A web-interface written in PHP offers consultation of the inventory, user-rights management, and technical support features. Agents In order to collect detailed information, one can install agents on the client machines in the inventory. Developers have made client agents available for: Microsoft Windows Linux Mac OS X Sun Solaris IBM AIX FreeBSD, NetBSD, OpenBSD HP-UX Android Relation to other software OCS Inventory can be used to feed the manager of GLPI and thus offers part of an ITAM solution. Samanage is a cloud-based, commercial ITAM, that has used modified OCS-NG agent as a data source. License OCS Inventory consists of free software published under GNU GPL v2. The developers own the copyright. References External links The official site of OCS Inventory GLPI Project OCS and BPM Free software programmed in Perl

Operating System (OS)

Astra Linux Astra Linux is a Russian Linux-based computer operating system (OS) developed to meet the needs of the Russian army, other armed forces and intelligence agencies. It provides data protection up to the level of "top secret" in Russian classified information grade by featuring mandatory access control. It has been officially certified by Russian Defense Ministry, Federal Service for Technical and Export Control and Federal Security Service. Specifications The creator of the OS is the Scientific/Manufacturing Enterprise Rusbitech which is applying solutions according to Russian Government decree No.2299-р of 17/10/2010 that orders federal authorities and budget institutions to implement Free Software use. The OS releases are named after Hero Cities in Russia and Commonwealth of Independent States (CIS). There is one release for general purpose code named Oryol aimed at "achieving small and mid-business goals". Other releases are marked "special purpose" – the Smolensk for x86-64 PCs, Tula for networking hardware, Novorossiysk for ARM mobile devices and Murmansk for IBM System Z mainframe computers. Rusbitech also manufactures a "soft/hardware trusted boot control module" MAKSIM-M1 ("М643М1") with PCI bus. It prevents unauthorized access and offers some other raised digital security features. The module, besides Astra Linux, also supports OSes with Linux kernel 2.6.x up to 5.x.x, as well as several Microsoft Windows OSes. It is declared the Astra Linux licenses correspond with Russian and international laws and "don't contradict with the spirit and demands of GPL license". The system uses .deb packages. Astra Linux is a recognized Debian derivative. Rusbitech has partnership relations with The Linux Foundation. It was part of the advisory board of The Document Foundation, but was suspended at 26th Feb. 2022 because of the Ukraine crisis. Use The Special Edition version (paid) is used in many Russian state-related organizations. Particularly, it is used in the Russian National Center for Defence Control. There are talks to deploy mass use of Astra Linux in many state institutions of the Republic of Crimea – legitimate use of other popular OSes is questionable because of international sanctions during the Ukrainian crisis. Also there are plans on cooperation of Rusbitech and Huawei. In January 2018, it was announced that Astra Linux was going to be deployed to all Russian Army computers, and Microsoft Windows will be dropped. In February 2018, Rusbitech announced it has ported Astra Linux to Russian-made Elbrus microprocessors. In February 2019, Astra Linux was announced to be implemented at Tianwan Nuclear Power Plant in China. Since 2019 "super-protected" tablet computers branded MIG are available with Astra Linux, smartphones are expected. In 2019 Gazprom national gas/oil holding announced Astra Linux implementation, in 2020 nuclear corporation Rosatom, in early 2021 Russian Railways was reported to do so. In 2020, Astra Linux sold more than a million copies in licenses and generated 2 billion rubles in sales. In 2021, several Russian nuclear power plants and subsidiaries of Rosatom are planned to switch to Astra Linux, with a total of 15000 users. Version history References X86-64 Linux distributions Debian-based distributions Linux distributions Russian-language Linux distributions State-sponsored Linux distributions

Operating System (OS)

Open architecture Open architecture is a type of computer architecture or software architecture intended to make adding, upgrading, and swapping components with other computers easy. For example, the IBM PC, Amiga 500 and Apple IIe have an open architecture supporting plug-in cards, whereas the Apple IIc computer has a closed architecture. Open architecture systems may use a standardized system bus such as S-100, PCI or ISA or they may incorporate a proprietary bus standard such as that used on the Apple II, with up to a dozen slots that allow multiple hardware manufacturers to produce add-ons, and for the user to freely install them. By contrast, closed architectures, if they are expandable at all, have one or two "expansion ports" using a proprietary connector design that may require a license fee from the manufacturer, or enhancements may only be installable by technicians with specialized tools or training. Computer platforms may include systems with both open and closed architectures. The Mac mini and Compact Macintosh are closed; the Macintosh II and Power Macintosh G5 are open. Most desktop PCs are open architecture. Similarly, an open software architecture is one in which additional software modules can be added to the basic framework provided by the architecture. Open APIs (Application Programming Interfaces) to major software products are the way in which the basic functionality of such products can be modified or extended. The Google APIs are examples. A second type of open software architecture consists of the messages that can flow between computer systems. These messages have a standard structure that can be modified or extended per agreements between the computer systems. An example is IBM's Distributed Data Management Architecture. Open architecture allows potential users to see inside all or parts of the architecture without any proprietary constraints. Typically, an open architecture publishes all or parts of its architecture that the developer or integrator wants to share. The open business processes involved with an open architecture may require some license agreements between entities sharing the architecture information. Open architectures have been successfully implemented in many diverse fields, including the US Navy. See also Open network architecture for equal-access requirements in telecommunications Open-source software for software that can be modified and rebuilt Open-source hardware Open platform Open standards References Computer architecture Software architecture Open-source hardware

Operating System (OS)

Amoeba (operating system) Amoeba is a distributed operating system developed by Andrew S. Tanenbaum and others at the Vrije Universiteit Amsterdam. The aim of the Amoeba project was to build a timesharing system that makes an entire network of computers appear to the user as a single machine. Development at the Vrije Universiteit was stopped: the source code of the latest version (5.3) was last modified on 30 July 1996. The Python programming language was originally developed for this platform. Overview The goal of the Amoeba project was to construct an operating system for networks of computers that would present the network to the user as if it were a single machine. An Amoeba network consists of a number of workstations connected to a "pool" of processors, and executing a program from a terminal causes it to run on any of the available processors, with the operating system providing load balancing. Unlike the contemporary Sprite, Amoeba does not support process migration. The workstations would typically function as networked terminals only. Aside from workstations and processors, additional machines operate as servers for files, directory services, TCP/IP communications etc. Amoeba is a microkernel-based operating system. It offers multithreaded programs and a remote procedure call (RPC) mechanism for communication between threads, potentially across the network; even kernel-threads use this RPC mechanism for communication. Each thread is assigned a 48-bit number called its "port", which serves as its unique, network-wide "address" for communication. The user interface and APIs of Amoeba were modeled after Unix and compliance with the POSIX standard was partially implemented; some of the Unix emulation code consists of utilities ported over from Tanenbaum's other operating system, MINIX. Early versions used a "homebrew" window system, which the Amoeba authors considered "faster ... in our view, cleaner ... smaller and much easier to understand", but version 4.0 uses the X Window System (and allows X terminals as terminals). The system uses FLIP as a network protocol. See also Distributed computing Multikernel Plan 9 from Bell Labs References External links Amoeba home page FSD-Amoeba page at Sourceforge Microkernel-based operating systems Distributed computing architecture Distributed operating systems Computer science in the Netherlands Information technology in the Netherlands Microkernels

Operating System (OS)

List of DOS commands This article presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list. In DOS, many standard system commands were provided for common tasks such as listing files on a disk or moving files. Some commands were built into the command interpreter, others existed as external commands on disk. Over the several generations of DOS, commands were added for the additional functions of the operating system. In the current Microsoft Windows operating system, a text-mode command prompt window, cmd.exe, can still be used. Command processing The command interpreter for DOS runs when no application programs are running. When an application exits, if the transient portion of the command interpreter in memory was overwritten, DOS will reload it from disk. Some commands are internal—built into COMMAND.COM; others are external commands stored on disk. When the user types a line of text at the operating system command prompt, COMMAND.COM will parse the line and attempt to match a command name to a built-in command or to the name of an executable program file or batch file on disk. If no match is found, an error message is printed, and the command prompt is refreshed. External commands were too large to keep in the command processor, or were less frequently used. Such utility programs would be stored on disk and loaded just like regular application programs but were distributed with the operating system. Copies of these utility command programs had to be on an accessible disk, either on the current drive or on the command path set in the command interpreter. In the list below, commands that can accept more than one file name, or a filename including wildcards (* and ?), are said to accept a filespec (file specification) parameter. Commands that can accept only a single file name are said to accept a filename parameter. Additionally, command line switches, or other parameter strings, can be supplied on the command line. Spaces and symbols such as a "/" or a "-" may be used to allow the command processor to parse the command line into filenames, file specifications, and other options. The command interpreter preserves the case of whatever parameters are passed to commands, but the command names themselves and file names are case-insensitive. Many commands are the same across many DOS systems, but some differ in command syntax or name. DOS commands A partial list of the most common commands for MS-DOS and IBM PC DOS follows below. APPEND Sets the path to be searched for data files or displays the current search path. The APPEND command is similar to the PATH command that tells DOS where to search for program files (files with a .COM, . EXE, or .BAT file name extension). The command is available in MS-DOS versions 3.2 and later. ASSIGN The command redirects requests for disk operations on one drive to a different drive. It can also display drive assignments or reset all drive letters to their original assignments. The command is available in MS-DOS versions 3 through 5 and IBM PC DOS releases 2 through 5. ATTRIB Attrib changes or views the attributes of one or more files. It defaults to display the attributes of all files in the current directory. The file attributes available include read-only, archive, system, and hidden attributes. The command has the capability to process whole folders and subfolders of files and also process all files. The command is available in MS-DOS versions 3 and later. BACKUP and RESTORE These are commands to backup and restore files from an external disk. These appeared in version 2, and continued to PC DOS 5 and MS-DOS 6 (PC DOS 7 had a deversioned check). In DOS 6, these were replaced by commercial programs (CPBACKUP, MSBACKUP), which allowed files to be restored to different locations. BASIC and BASICA An implementation of the BASIC programming language for PCs. Implementing BASIC in this way was very common in operating systems on 8- and 16-bit machines made in the 1980s. IBM computers had BASIC 1.1 in ROM, and IBM's versions of BASIC used code in this ROM-BASIC, which allowed for extra memory in the code area. BASICA last appeared in IBM PC DOS 5.02, and in OS/2 (2.0 and later), the version had ROM-BASIC moved into the program code. Microsoft released GW-BASIC for machines with no ROM-BASIC. Some OEM releases had basic.com and basica.com as loaders for GW-BASIC.EXE. BASIC was dropped after MS-DOS 4, and PC DOS 5.02. OS/2 (which uses PC DOS 5), has it, while MS-DOS 5 does not. BREAK This command is used to instruct DOS to check whether the and keys have been pressed before carrying out a program request. The command is available in MS-DOS versions 2 and later. CALL Starts a batch file from within another batch file and returns when that one ends. The command is available in MS-DOS versions 3.3 and later. CD and CHDIR The CHDIR (or the alternative name CD) command either displays or changes the current working directory. The command is available in MS-DOS versions 2 and later. CHCP The command either displays or changes the active code page used to display character glyphs in a console window. Similar functionality can be achieved with MODE CON: CP SELECT=. The command is available in MS-DOS versions 3.3 and later. CHKDSK CHKDSK verifies a storage volume (for example, a hard disk, disk partition or floppy disk) for file system integrity. The command has the ability to fix errors on a volume and recover information from defective disk sectors of a volume. The command is available in MS-DOS versions 1 and later. CHOICE The CHOICE command is used in batch files to prompt the user to select one item from a set of single-character choices. Choice was introduced as an external command with MS-DOS 6.0; Novell DOS 7 and PC DOS 7.0. Earlier versions of DR-DOS supported this function with the built-in switch command (for numeric choices) or by beginning a command with a question mark. This command was formerly called ync (yes-no-cancel). CLS The CLS or CLRSCR command clears the terminal screen. The command is available in MS-DOS versions 2 and later. COMMAND Start a new instance of the command interpreter. The command is available in MS-DOS versions 1 and later. COMP Show differences between any two files, or any two sets of files. The command is available in MS-DOS versions 3.3 through 5 and IBM PC DOS releases 1 through 5. COPY Makes copies of existing files. The command is available in MS-DOS versions 1 and later. CTTY Defines the terminal device (for example, COM1) to use for input and output. The command is available in MS-DOS versions 2 and later. DATE Displays the system date and prompts the user to enter a new date. Complements the TIME command. The command is available in MS-DOS versions 1 and later. DBLBOOT (Not a command: This is a batch file added to DOS 6.X Supplemental Disks to help create DoubleSpace boot floppies.) DBLSPACE A disk compression utility supplied with MS-DOS version 6.0 (released in 1993) and version 6.2. DEBUG A very primitive assembler and disassembler. DEFRAG The command has the ability to analyze the file fragmentation on a disk drive or to defragment a drive. This command is called DEFRAG in MS-DOS/PC DOS and diskopt in DR-DOS. The command is available in MS-DOS versions 6 and later. DEL and ERASE DEL (or the alternative form ERASE) is used to delete one or more files. The command is available in MS-DOS versions 1 and later. DELTREE Deletes a directory along with all of the files and subdirectories that it contains. Normally, it will ask for confirmation of the potentially dangerous action. Since the RD (RMDIR) command can not delete a directory if the directory is not empty (except in Windows NT & 10), the DELTREE command can be used to delete the whole directory. The deltree command is included in certain versions of Microsoft Windows and MS-DOS operating systems. It is specifically available only in versions of MS-DOS 6.0 and higher, and in Microsoft Windows 9x. In Windows NT, the functionality provided exists but is handled by the command or which has slightly different syntax. This command is not present in Windows 7 and 8. In Windows 10, the command switch is or . DIR The DIR command displays the contents of a directory. The contents comprise the disk's volume label and serial number; one directory or filename per line, including the filename extension, the file size in bytes, and the date and time the file was last modified; and the total number of files listed, their cumulative size, and the free space (in bytes) remaining on the disk. The command is one of the few commands that exist from the first versions of DOS. The command can display files in subdirectories. The resulting directory listing can be sorted by various criteria and filenames can be displayed in a chosen format. DISKCOMP A command for comparing the complete contents of a floppy disk to another one. The command is available in MS-DOS versions 3.2 and later and IBM PC DOS releases 1 and later. DISKCOPY A command for copying the complete contents of a diskette to another diskette. The command is available in MS-DOS versions 2 and later. DOSKEY A command that adds command history, macro functionality, and improved editing features to the command-line interpreter. The command is available in MS-DOS versions 5 and later. DOSSIZE Displays how much memory various DOS components occupy. DRVSPACE A disk compression utility supplied with MS-DOS version 6.22. ECHO The ECHO command prints its own arguments back out to the DOS equivalent of the standard output stream. (Hence the name, ECHO) Usually, this means directly to the screen, but the output of echo can be redirected, like any other command, to files or devices. Often used in batch files to print text out to the user. Another important use of the echo command is to toggle echoing of commands on and off in batch files. Traditionally batch files begin with the @echo off statement. This says to the interpreter that echoing of commands should be off during the whole execution of the batch file, thus resulting in a "tidier" output (the @ symbol declares that this particular command (echo off) should also be executed without echo.) The command is available in MS-DOS versions 2 and later. EDIT EDIT is a full-screen text editor, included with MS-DOS versions 5 and 6, OS/2 and Windows NT to 4.0 The corresponding program in Windows 95 and later, and Windows 2000 and later is Edit v2.0. PC DOS 6 and later use the DOS E Editor and DR-DOS used editor up to version 7. EDLIN DOS line-editor. It can be used with a script file, like debug, this makes it of some use even today. The absence of a console editor in MS-DOS/PC DOS 1–4 created an after-market for third-party editors. In DOS 5, an extra command "?" was added to give the user much-needed help. DOS 6 was the last version to contain EDLIN; for MS-DOS 6, it's on the supplemental disks, while PC DOS 6 had it in the base install. Windows NT 32-bit, and OS/2 have Edlin. EMM386 The EMM386 command enables or disables EMM386 expanded-memory support on a computer with an 80386 or higher processor. The command is available in MS-DOS versions 5 and later. ERASE See: DEL and ERASE EXE2BIN Converts an executable (.exe) file into a binary file with the extension .com, which is a memory image of the program. The size of the resident code and data sections combined in the input .exe file must be less than 64 KB. The file must also have no stack segment. The command is available in MS-DOS versions 1 through 5. It is available separately for version 6 on the Supplemental Disk. EXIT Exits the current command processor. If the exit is used at the primary command, it has no effect unless in a DOS window under Microsoft Windows, in which case the window is closed and the user returns to the desktop. The command is available in MS-DOS versions 2 and later. EXPAND The Microsoft File Expansion Utility is used to uncompress one or more compressed cabinet files (.CAB). The command dates back to 1990 and was supplied on floppy disc for MS-DOS versions 5 and later. FAKEMOUS FAKEMOUS is an IBM PS/2 mouse utility used with AccessDOS. It is included on the MS-DOS 6 Supplemental Disk. AccessDOS assists persons with disabilities. FASTHELP Provides information for MS-DOS commands. FASTOPEN A command that provides accelerated access to frequently-used files and directories. The command is available in MS-DOS versions 3.3 and later. FC Show differences between any two files, or any two sets of files. The command is available in MS-DOS versions 2 and later – primarily non-IBM releases. FDISK The FDISK command manipulates hard disk partition tables. The name derives from IBM's habit of calling hard drives fixed disks. FDISK has the ability to display information about, create, and delete DOS partitions or logical DOS drive. It can also install a standard master boot record on the hard drive. The command is available in MS-DOS versions 3.2 and later and IBM PC DOS 2.0 releases and later. FIND The FIND command is a filter to find lines in the input data stream that contain or don't contain a specified string and send these to the output data stream. It may also be used as a pipe. The command is available in MS-DOS versions 2 and later. FINDSTR The FINDSTR command is a GREP-oriented FIND-like utility. Among its uses is the logical-OR lacking in FIND. would find all TXT files with one or more of the above-listed words YES, NO, MAYBE. FOR Iteration: repeats a command for each out of a specified set of files. The FOR loop can be used to parse a file or the output of a command. The command is available in MS-DOS versions 2 and later. FORMAT Deletes the FAT entries and the root directory of the drive/partition, and reformats it for MS-DOS. In most cases, this should only be used on floppy drives or other removable media. This command can potentially erase everything on a computer's drive. The command is available in MS-DOS versions 1 and later. GOTO The Goto command transfers execution to a specified label. Labels are specified at the beginning of a line, with a colon (). The command is available in MS-DOS versions 2 and later. Used in Batch files. GRAFTABL The GRAFTABL command enables the display of an extended character set in graphics mode. The command is available in MS-DOS versions 3 through 5. GRAPHICS A TSR program to enable the sending of graphical screen dump to printer by pressing <Print Screen>. The command is available in MS-DOS versions 3.2 and later and IBM PC DOS releases 2 and later. HELP Gives help about DOS commands. The command is available in MS-DOS versions 5 thru Windows XP. Full-screen command help is available in MS-DOS versions 6 and later. Beginning with Windows XP, the command processor "DOS" offers builtin-help for commands by using (e.g. ) IF IF is a conditional statement, that allows branching of the program execution. It evaluates the specified condition, and only if it is true, then it executes the remainder of the command line. Otherwise, it skips the remainder of the line and continues with next command line. Used in Batch files. The command is available in MS-DOS versions 2 and later. INTERSVR and INTERLNK In MS-DOS; filelink in DR-DOS. Network PCs using a null modem cable or LapLink cable. The server-side version of InterLnk, it also immobilizes the machine it's running on as it is an active app (As opposed to a TSR app) which must be running for any transfer to take place. DR-DOS' filelink is executed on both the client and server. New in PC DOS 5.02, MS-DOS 6.0. JOIN The JOIN command attaches a drive letter to a specified directory on another drive. The opposite can be achieved via the SUBST command. The command is available in MS-DOS versions 3 through 5. It is available separately for versions 6.2 and later on the Supplemental Disk. KEYB The KEYB command is used to select a keyboard layout. The command is available in MS-DOS versions 3.3 and later. From DOS 3.0 through 3.21, there are instead per-country commands, namely KEYBFR, KEYBGR, KEYBIT, KEYBSP and KEYBUK. LABEL Changes the label on a logical drive, such as a hard disk partition or a floppy disk. The command is available in MS-DOS versions 3.1 and later and IBM PC DOS releases 3 and later. LINK4 Microsoft 8086 Object Linker LOADFIX Loads a program above the first 64K of memory, and runs the program. The command is available in MS-DOS versions 5 and later. It is included only in MS-DOS/PC DOS. DR-DOS used memmax, which opened or closed lower, upper, and video memory access, to block the lower 64K of memory. LOADHIGH and LH A command that loads a program into the upper memory area. The command is available in MS-DOS versions 5 and later. It is called hiload in DR-DOS. MD or MKDIR Makes a new directory. The parent of the directory specified will be created if it does not already exist. The command is available in MS-DOS versions 2 and later. MEM Displays memory usage. It is capable of displaying program size and status, memory in use, and internal drivers. It is an external command. The command is available in MS-DOS versions 4 and later. MEMMAKER Starting with version 6, MS-DOS included the external program MemMaker which was used to free system memory (especially Conventional memory) by automatically reconfiguring the AUTOEXEC.BAT and CONFIG.SYS files. This was usually done by moving TSR programs and device drivers to the upper memory. The whole process required two system restarts. Before the first restart the user was asked whether to enable EMS Memory, since use of expanded memory required a reserved 64KiB region in upper memory. The first restart inserted the SIZER.EXE program which gauged the memory needed by each TSR or Driver. MemMaker would then calculate the optimal Driver and TSR placement in upper memory and modify the AUTOEXEC.BAT and CONFIG.SYS accordingly, and reboot the second time. MEMMAKER.EXE and SIZER.EXE were developed for Microsoft by Helix Software Company and were eliminated starting in MS-DOS 7 (Windows 95); however, they could be obtained from Microsoft's FTP server as part of the OLDDOS.EXE package, alongside other tools. PC DOS uses another program called RamBoost to optimize memory, working either with PC DOS's HIMEM/EMM386 or a third-party memory manager. RamBoost was licensed to IBM by Central Point Software. MIRROR The MIRROR command saves disk storage information that can be used to recover accidentally erased files. The command is available in MS-DOS version 5. It is available separately for versions 6.2 and later on Supplemental Disk. MODE Configures system devices. Changes graphics modes, adjusts keyboard settings, prepares code pages, and sets up port redirection. The command is available in MS-DOS versions 3.2 and later and IBM PC DOS releases 1 and later. MORE The MORE command paginates text, so that one can view files containing more than one screen of text. More may also be used as a filter. While viewing MORE text, the return key displays the next line, the space bar displays the next page. The command is available in MS-DOS versions 2 and later. MOVE Moves files or renames directories. The command is available in MS-DOS versions 6 and later. DR-DOS used a separate command for renaming directories, rendir. MSAV A command that scans the computer for known viruses. The command is available in MS-DOS versions 6 and later. MSBACKUP The MSBACKUP command is used to backup or restore one or more files from one disk to another. The New York Times said that MSBACKUP "is much better and faster than the old BACKUP command used in earlier versions of DOS, but it does lack some of the advanced features found in backup software packages that are sold separately. There is another offering, named MWBACKUP, that is GUI-oriented. It was introduced for Windows for Workgroups (3.11). The MSBACKUP command is available in MS-DOS versions 6 and later. MSCDEX MSCDEX is a driver executable which allows DOS programs to recognize, read, and control CD-ROMs. The command is available in MS-DOS versions 6 and later. MSD The MSD command provides detailed technical information about the computer's hardware and software. MSD was new in MS-DOS 6; the PC DOS version of this command is QCONFIG. The command appeared first in Word2, and then in Windows 3.10. MSHERC The MSHERC.COM (also QBHERC.COM) was a TSR (Terminate and Stay Resident) graphics driver supplied with Microsoft QuickC, QuickBASIC, and the C Compiler, to allow use of the Hercules adapter high-resolution graphics capability (720 x 348, 2 colors). NLSFUNC Loads extended Nationalization and Localization Support from COUNTRY.SYS, and changed the codepage of drivers and system modules resident in RAM. In later versions of DR-DOS 6, NLSFUNC relocated itself into the HiMem area, thereby freeing a portion of the nearly invaluable lower 640KiB that constituted the ”conventional” memory available to software. The command is available in MS-DOS versions 3.3 and later. PATH Displays or sets a search path for executable files. The command is available in MS-DOS versions 2 and later. PAUSE Suspends processing of a batch program and displays the message , if not given other text to display. The command is available in MS-DOS versions 1 and later. PING Allows the user to test the availability of a network connection to a specified host. Hostnames are usually resolved to IP addresses. It is not included in many DOS versions; typically ones with network stacks will have it as a diagnostic tool. POWER The POWER command is used to turn power management on and off, report the status of power management, and set levels of power conservation. It is an external command implemented as POWER.EXE. The command is available in MS-DOS versions 6 and later. PRINT The PRINT command adds or removes files in the print queue. This command was introduced in MS-DOS version 2. Before that there was no built-in support for background printing files. The user would usually use the copy command to copy files to LPT1. PRINTFIX PROMPT The command allows the user to change the prompt in the command screen. The default prompt is (i.e. ), which displays the drive and current path as the prompt, but can be changed to anything. , displays the current system date as the prompt. Type in the cmd screen for help on this function. The command is available in MS-DOS versions 2 and later and IBM PC DOS releases 2.1 and later. PS A utility inspired by the UNIX/XENIX ps command. It also provides a full-screen mode, similar to the top utility on UNIX systems. QBASIC An integrated development environment and BASIC interpreter. The command is available in MS-DOS versions 5 and later. RD or RMDIR Remove a directory (delete a directory); by default the directories must be empty of files for the command to succeed. The command is available in MS-DOS versions 2 and later. The deltree command in some versions of MS-DOS and all versions of Windows 9x removes non-empty directories. RECOVER A primitive filesystem error recovery utility included in MS-DOS / IBM PC DOS. The command is available in MS-DOS versions 2 through 5. REM Remark (comment) command, normally used within a batch file, and for DR-DOS, PC/MS-DOS 6 and above, in CONFIG.SYS. This command is processed by the command processor. Thus, its output can be redirected to create a zero-byte file. REM is useful in logged sessions or screen-captures. One might add comments by way of labels, usually starting with double-colon (::). These are not processed by the command processor. REN The REN command renames a file. Unlike the move command, this command cannot be used to rename subdirectories, or rename files across drives. Mass renames can be accomplished by the use of the wildcards characters asterisk (*) and question mark (?). The command is available in MS-DOS versions 1 and later. REPLACE A command that is used to replace one or more existing computer files or add new files to a target directory. The command is available in MS-DOS versions 3.2 and later. RESTORE See: BACKUP and RESTORE SCANDISK Disk diagnostic utility. Scandisk was a replacement for the chkdsk utility, starting with MS-DOS version 6.2 and later. Its primary advantages over chkdsk is that it is more reliable and has the ability to run a surface scan which finds and marks bad clusters on the disk. It also provided mouse point-and-click TUI, allowing for interactive session to complement command-line batch run. chkdsk had surface scan and bad cluster detection functionality included, and was used again on Windows NT-based operating systems. SELECT The SELECT command formats a disk and installs country-specific information and keyboard codes. It was initially only available with IBM PC DOS. The version included with PC DOS 3.0 and 3.1 is hard-coded to transfer the operating system from A: to B:, while from PC DOS 3.2 onward you can specify the source and destination, and can be used to install DOS to the harddisk. The version included with MS-DOS 4 and PC-DOS 4 is no longer a simple command-line utility, but a full-fledged installer. The command is available in MS-DOS versions 3.3 and 4 and IBM PC DOS releases 3 through 4. This command is no longer included in DOS Version 5 and later, where it has been replaced by SETUP. SET Sets environment variables. The command is available in MS-DOS versions 2 and later. cmd.exe in Windows NT 2000, 4DOS, 4OS2, 4NT, and a number of third-party solutions allow direct entry of environment variables from the command prompt. From at least Windows 2000, the set command allows for the evaluation of strings into variables, thus providing inter alia a means of performing integer arithmetic. SETUP The command is available in MS-DOS versions 5 and later. This command does a computer setup. With all computers running DOS versions 5 and later, it runs the computer setup, such as Windows 95 setup and Windows 98 setup. SETVER SetVer is a TSR program designed to return a different value to the version of DOS that is running. This allows programs that look for a specific version of DOS to run under a different DOS. The command is available in MS-DOS versions 5 and later. SHARE Installs support for file sharing and locking capabilities. The command is available in MS-DOS versions 3 and later. SHIFT The SHIFT command increases number of replaceable parameters to more than the standard ten for use in batch files. This is done by changing the position of replaceable parameters. It replaces each of the replacement parameters with the subsequent one (e.g. with , with , etc.). The command is available in MS-DOS versions 2 and later. SIZER The external command SIZER.EXE is not intended to be started directly from the command prompt. Is used by MemMaker during the memory-optimization process. SMARTDRV The command is available in MS-DOS versions 6 and later. SORT A filter to sort lines in the input data stream and send them to the output data stream. Similar to the Unix command sort. Handles files up to 64k. This sort is always case insensitive. The command is available in MS-DOS versions 2 and later. SUBST A utility to map a subdirectory to a drive letter. The opposite can be achieved via the JOIN command. The command is available in MS-DOS versions 3.1 and later. SYS A utility to make a volume bootable. Sys rewrites the Volume Boot Code (the first sector of the partition that SYS is acting on) so that the code, when executed, will look for IO.SYS. SYS also copies the core DOS system files, IO.SYS, MSDOS.SYS, and COMMAND.COM, to the volume. SYS does not rewrite the Master Boot Record, contrary to widely held belief. The command is available in MS-DOS versions 1 and later. TELNET The Telnet Client is a tool for developers and administrators to help manage and test network connectivity. TIME Display the system time and waits for the user to enter a new time. Complements the DATE command. The command is available in MS-DOS versions 1 and later. TITLE Enables a user to change the title of their MS-DOS window. TREE It is an external command, graphically displays the path of each directory and sub-directories on the specified drive. The command is available in MS-DOS versions 3.2 and later and IBM PC DOS releases 2 and later. TRUENAME Internal command that expands the name of a file, directory, or drive, and display its absolute pathname as the result. It will expand relative pathnames, SUBST drives, and JOIN directories, to find the actual directory. For example, in DOS 7.1, if the current directory is C:\WINDOWS\SYSTEM, then The argument does not need to refer to an existing file or directory: TRUENAME will output the absolute pathname as if it did. Also TRUENAME does not search in the PATH. For example, in DOS 5, if the current directory is C:\TEMP, then TRUENAME command.com will display C:\TEMP\COMMAND.COM (which does not exist), not C:\DOS\COMMAND.COM (which does and is in the PATH). This command displays the UNC pathnames of mapped network or local CD drives. This command is an undocumented DOS command. The help switch "/?" defines it as a "Reserved command name". It is available in MS-DOS version 5.00 and later, including the DOS 7 and 8 in Windows 95/98/ME. The C library function realpath performs this function. The Microsoft Windows NT command processors do not support this command, including the versions of command.com for NT. TYPE Displays a file. The more command is frequently used in conjunction with this command, e.g. type long-text-file | more. TYPE can be used to concatenate files (); however this won't work for large files—use copy command instead. The command is available in MS-DOS versions 1 and later. UNDELETE Restores file previously deleted with del. By default all recoverable files in the working directory are restored; options are used to change this behavior. If the MS-DOS mirror TSR program is used, then deletion tracking files are created and can be used by undelete. The command is available in MS-DOS versions 5 and later. UNFORMAT The UNFORMAT command is used to undo the effects of formatting a disk. The command is available in MS-DOS versions 5 and later. VER An internal DOS command, that reports the DOS version presently running, and since MS-DOS 5, whether DOS is loaded high. The command is available in MS-DOS versions 2 and later. VERIFY Enables or disables the feature to determine if files have been correctly written to disk. If no parameter is provided, the command will display the current setting. The command is available in MS-DOS versions 2 and later. VOL An internal command that displays the disk volume label and serial number. The command is available in MS-DOS versions 2 and later. VSAFE A TSR program that continuously monitors the computer for viruses. The command is available in MS-DOS versions 6 and later. XCOPY Copy entire directory trees. Xcopy is a version of the copy command that can move files and directories from one location to another. XCOPY usage and attributes can be obtained by typing in the DOS Command line. The command is available in MS-DOS versions 3.2 and later. See also :Category:Windows commands Command-line interface List of CONFIG.SYS directives Timeline of DOS operating systems References Further reading External links Command-Line Reference : Microsoft TechNet Database "Command-Line Reference" The MS-DOS 6 Technical Reference on TechNet contains the official Microsoft MS-DOS 6 command reference documention. DR-DOS 7.03 online manual MDGx MS-DOS Undocumented + Hidden Secrets There are several guides to DOS commands available that are licensed under the GNU Free Documentation License: The FreeDOS Spec at SourceForge is a plaintext specification, written in 1999, for how DOS commands should work in FreeDOS MS-DOS commands Reference for windows commands with examples A Collection of Undocumented and Obscure Features in Various MS-DOS Versions DOS commands DOS commands

Operating System (OS)

Features new to Windows XP As the next version of Windows NT after Windows 2000, as well as the successor to Windows Me, Windows XP introduced many new features but it also removed some others. User interface and appearance Graphics With the introduction of Windows XP, the C++ based software-only GDI+ subsystem was introduced to replace certain GDI functions. GDI+ adds anti-aliased 2D graphics, textures, floating point coordinates, gradient shading, more complex path management, bicubic filtering, intrinsic support for modern graphics-file formats like JPEG and PNG, and support for composition of affine transformations in the 2D view pipeline. GDI+ uses ARGB values to represent color. Use of these features is apparent in Windows XP's user interface (transparent desktop icon labels, drop shadows for icon labels on the desktop, shadows under menus, translucent blue selection rectangle in Windows Explorer, sliding task panes and taskbar buttons), and several of its applications such as Microsoft Paint, Windows Picture and Fax Viewer, Photo Printing Wizard, My Pictures Slideshow screensaver, and their presence in the basic graphics layer greatly simplifies implementations of vector-graphics systems such as Flash or SVG. The GDI+ dynamic library can be shipped with an application and used under older versions of Windows. The total number of GDI handles per session is also raised in Windows XP from 16,384 to 65,536 (configurable through the registry). Windows XP shipped with DirectX 8.1, which brings major new features to DirectX Graphics besides DirectX Audio (both DirectSound and DirectMusic), DirectPlay, DirectInput and DirectShow. Direct3D introduced programmability in the form of vertex and pixel shaders, enabling developers to write code without worrying about superfluous hardware state, and fog, bump mapping and texture mapping. DirectX 9 was released in 2003, which also sees major revisions to Direct3D, DirectSound, DirectMusic and DirectShow. Direct3D 9 added a new version of the High Level Shader Language, support for floating-point texture formats, Multiple Render Targets, and texture lookups in the vertex shader. Windows XP can be upgraded to DirectX 9.0c (Shader Model 3.0). ClearType Windows XP includes ClearType subpixel rendering, which makes onscreen fonts smoother and more readable on liquid crystal display (LCD) screens. Although ClearType has an effect on CRT monitors, its primary use is for LCD/TFT-based (laptop, notebook and modern 'flatscreen') displays. ClearType in Windows XP currently supports the RGB and BGR sub pixel structures. There are other parameters such as contrast that can be set via a ClearType Tuner powertoy that Microsoft makes available as a free download from its Typography website. Start menu With Windows XP, the Start button has been updated to support Fitts's law. To help the user access a wider range of common destinations more easily from a single location, the Start menu was expanded to two columns; the left column focuses on the user's installed applications, while the right column provides access to the user's documents, and system links which were previously located on the desktop. Links to the My Documents, My Pictures and other special folders are brought to the fore. The My Computer and My Network Places (Network Neighborhood in Windows 95 and 98) icons were also moved off the Desktop and into the Start menu, making it easier to access these icons while a number of applications are open and so that the desktop remains clean. Moreover, these links can be configured to expand as a cascading menu. Frequently used programs are automatically displayed in the left column, newly installed programs are highlighted, and the user may opt to "pin" programs to the start menu so that they are always accessible without having to navigate through the Programs folders. The default internet browser and default email program are pinned to the Start menu. The Start menu is fully customizable, links can be added or removed; the number of frequently used programs to display can be set. The All Programs menu expands like the classic Start menu to utilize the entire screen but can be set to scroll programs. The user's name and user's account picture are also shown on the Start menu. Taskbar The taskbar buttons for running applications and Quick Launch have also been updated for Fitt's law. Locking the taskbar not only prevents it from being accidentally resized or moved but elements such as Quick launch and other DeskBands are also locked from being accidentally moved. The Taskbar grouping feature combines multiple buttons of the same application into a single button, which when clicked, pops up a menu listing all the grouped windows and their number. Advanced taskbar grouping options can be configured from the registry. The user can choose to always show, always hide or hide some or all notification area icons if inactive for some time. A button allows the user to reveal all the icons. The Taskbar, if set to a thicker height also displays the day and date in the notification area. Windows Explorer There are significant changes made to Windows Explorer in Windows XP, both visually and functionally. Microsoft focused especially on making Windows Explorer more discoverable and task-based, as well as adding a number of features to reflect the growing use of a computer as a "digital hub". Task pane The task pane is displayed on the left side of the window instead of the traditional folder tree view when the navigation pane is turned off. It presents the user with a list of common actions and destinations that are relevant to the current directory or file(s) selected. For instance, when in a directory containing mostly pictures, a set of "Picture tasks" is shown, offering the options to display these pictures as a slide show, to print them, or to go online to order prints. Conversely, a folder containing music files would offer options to play those files in a media player, or to go online to purchase music. Every folder also has "File and Folder Tasks", offering options to create new folders, share a folder on the local network, publish files or folders to a web site using the Web Publishing Wizard, and other common tasks like copying, renaming, moving, and deleting files or folders. File types that have identified themselves as being printable also have an option listed to print the file. Underneath "File and Folder Tasks" is "Other Places", which always lists the parent folder of the folder being viewed and includes additional links to other common locations such as "My Computer", "Control Panel", and "My Documents" or previously navigated locations. These change depending on what folder the user was in. Underneath "Other Places" is a "Details" area which gives additional information when a file or folder is selected – typically the file type, file size and date modified, but depending on the file type, author, image dimensions, attributes, or other details. If the file type has a Thumbnail image handler installed, its preview also appears in the "Details" task pane. For music files, it might show the artist, album title, and the length of the song. The same information is also shown horizontally on the status bar. Navigation pane The "Folders" button on the Windows Explorer toolbar toggles between the traditional navigation pane containing the tree view of folders, and the task pane. Users can also close the navigation pane by clicking the Close button in its right corner as well as turn off the task pane from Folder Options. The navigation pane has been enhanced in Windows XP to support "simple folder view" which when turned on hides the dotted lines that connect folders and subfolders and makes folders browsable with single click while still keeping double clicking on in the right pane. Single clicking in simple folder view auto expands the folder and clicking another folder automatically expands that folder and collapses the previous one. Grouping and sorting Windows XP introduced a large number of metadata properties which are shown as columns in the "Details" view of Explorer, in the new Tiles view in Explorer, on the Summary tab in a file's properties, in a file's tooltip and on the Explorer status bar when a single file is selected. Users also gain the ability to sort by any property which is turned on in "Details" view. Developers can write column handler shell extensions to further define their own properties by which files can be sorted. The column by which items are sorted is highlighted. Sorting files and folders can be in Ascending order or Descending order in all views, not just Details view. To reverse the order, the user simply can perform the sort by the same property again. The sort order has also been made more intuitive compared to the one in Windows 2000. For file names containing numbers Windows Explorer now tries to sort based on numerical value rather than just comparing each number digit by digit for every character position in the file name. For instance, files containing "1", "2".."10" will be intuitively sorted with "10" appearing after "9" instead of appearing between "1" and "2". The right pane of Windows Explorer has a "Show in Groups" feature which allows Explorer to separate its contents by headings based on any field which is used to sort the items. Items can thus be grouped by any detail which is turned on. "Show in Groups" is available in Thumbnails, Tiles, Icons and Details views. Search Microsoft introduced animated "Search Companions" in an attempt to make searching more engaging and friendly; the default character is a puppy named Rover, with three other characters (Merlin the magician, Earl the surfer, and Courtney) also available. These search companions powered by Microsoft Agent technology, bear a great deal of similarity to Microsoft Office's Office Assistants, even incorporating "tricks" and sound effects. If the user wishes, they can also turn off the animated character entirely. The search capability itself is fairly similar to Windows Me and Windows 2000, with some important additions. The Indexing Service can extract Exif properties, as well as some metadata for ASF, WMV and MP3 files under Windows XP via the IPropertyStorage interface using built-in Null Filter. Search can also be instructed to search only files that are categorically "Documents" or "Pictures, music and video" (searching by perceived type); this feature is noteworthy largely because of how Windows determines what types of files can be classified under these categories. Another important addition is that the "Look in" field accepts and expands environment variables for abbreviated entry of long paths. Also, users can configure whether or not Windows XP searches for system and/or hidden files and folders. Using Tweak UI, the search user interface can be restored to the one used by Windows 2000. Image handling in Explorer Windows XP improves image preview by offering a Filmstrip view which shows images in a single horizontal row and a large preview of the currently selected image above it. "Back" and "Previous" buttons facilitate navigation through the pictures, and a pair of "Rotate" buttons offer 90-degree clockwise and counter-clockwise rotation of images. Filmstrip view like any other view can be turned on per folder. This view will be available if the new "Common Tasks" folder view is selected, not with "Windows Classic" folder view. Aside from the Filmstrip view mode, there is a 'Thumbnails' view, which displays thumbnail-sized images in the folder and also displays images a subfolder may be containing (4 by default) overlaid on a large folder icon. A folder's thumbnail view can be customized from the Customize tab accessible from its Properties, where users can also change the folder's icon and specify a template type (pictures, music, videos, documents) for that folder and optionally all its subfolders. The size and quality of thumbnails in "Thumbnails" view can be adjusted using Tweak UI or the registry. Exif metadata stored in the image is also shown in the file's Properties -> Summary tab, in "Details" view and in any view on the status bar. Windows XP optionally caches the thumbnails in a "Thumbs.db" file in the same folder as the pictures so that thumbnails are generated faster the next time. Thumbnails can be forced to regenerate by right-clicking the image in Thumbnail or Filmstrip views and selecting "Refresh thumbnail". AutoPlay AutoPlay examines newly discovered removable media and devices and, based on content such as pictures, music or video files, launches an appropriate application to play or display the content. AutoPlay (not to be confused with AutoRun) was created in order to simplify the use of peripheral devices – MP3 players, memory cards, USB storage devices and others – by automatically starting the software needed to access and view the content on these devices. AutoPlay can be enhanced by AutoPlay-compatible software and hardware. It can be configured by the user to associate favourite applications with AutoPlay events and actions. These actions are called AutoPlay Handlers and there are sets of Handlers associated with various types of content. New AutoPlay handlers can get added to the system when additional software is installed. The user can edit, delete or create AutoPlay handlers using TweakUI. AutoPlay settings can be configured per-device in Windows XP from the device's properties. When a user inserts an optical disc into a drive or attaches a USB camera, Windows detects the arrival and starts a process of examining the device or searching the medium. It is looking for properties of the device or content on the medium so that AutoPlay can present a set of meaningful options to the user. When the user makes a particular choice, they also have the option to make that selection automatic the next time Windows sees that content or device. The content types available vary with the type of drive selected. Other shell and UI improvements Windows XP introduced the notion of Perceived Types, making it easier for applications and shell extensions to register themselves with file types, even if the default program and its associated ProgID changes. Perceived Types also made it easier for end users to search files without specifying individual file extensions. Per-user Recycle Bin for NTFS volumes. In earlier versions of Windows NT, one user could see the other user's deleted files located in the Recycle Bin. Folder options to restore previously open folder windows at logon (restoring Explorer sessions) Customizable infotips on a per-file-class (file type) basis without writing shell extensions Windows Explorer is content-dependent, that is, it attempts to detect the dominant type of files in a folder and then selects the most appropriate view for the user automatically unless the user manually sets the view. To prevent applications from taking over the file associations already registered with the default program explicitly set by the user, Windows XP prevents programmatic file associations if the Open With dialog or File Types tab is used by users to override the default. A "Tiles" view was added, which displays the file's icon in a larger size (48 × 48), and places the file name, descriptive type, and additional information by which the items are sorted (typically the file size for data files, and the publisher name for applications) to the right. The toolbars can be locked to prevent them from being accidentally moved. This same capability was also added to Internet Explorer's toolbars. The "Line up icons" feature in the context menu has been replaced by an "Align to grid" feature which when turned on always lines up icons. For unknown/undefined file types which inexperienced users may get confused when double clicked, Windows XP can contact a web service which shows additional information about that file type and what program created or can open that file type. If an image named "Folder.jpg" is placed inside a folder, that image will be used as the thumbnail for that folder and as Album Art for media files in Windows Media Player. EFS-encrypted files can be shown in an alternate color (green by default) beginning with Windows XP. File and folder size information is shown in tooltips upon mouse hover. For folders, size and partial folder contents are shown. When opening more than 15 files in a single operation, i.e. by selecting multiple files and pressing enter, Windows XP warns the user that Windows Explorer may become unresponsive, but still allows the user to do so. Windows Explorer supports a very basic form of mass renaming items. Marquee-style progress bars. A hyperlink control in system supplied common controls. Windows Picture and Fax Viewer Windows XP includes Windows Picture and Fax Viewer which is based on GDI+ and is capable of viewing image formats supported by GDI+, namely, JPEG, BMP, PNG, GIF (including animated GIFs), ICO, WMF, EMF and TIFF format files. It supersedes part of the functions of Imaging for Windows in previous versions of Windows. The Windows Picture and Fax Viewer is integrated with Windows Explorer for functions like slideshow, email, printing etc. and quickly starts up when an image is double clicked in Windows Explorer. It supports full file management from within the viewer itself, that is, right clicking the image shows the same context menu as the one shown when an image is right clicked in Windows Explorer. Images can be set as the desktop wallpaper from the context menu. It supports successive viewing of all images in current folder and looping through images, that is, after viewing the last image in a directory, it again shows the first image and vice versa. By default, images smaller than the user's display resolution are shown at their actual size. If an image is larger than the display resolution, it is scaled to fit the screen (Best Fit). Images can be zoomed in or out depending on the viewing area. When this is done, scroll bars allow for viewing of all areas of the image. It has Standard toolbar buttons for Delete, Print, Copy to and Open with. The Copy to button converts an image to a different format supported in GDI+, that is, JPEG, BMP, GIF, TIFF or PNG. The Print button starts the Photo Printing Wizard which allows printing images with picture titles using various page layouts such as full page prints, wallet prints, contact/index sheets or certain fixed dimensions with the images cropped or rotated to fit the page. The wizard shows a preview of what the printed page will look like with the currently specified options. Windows Picture and Fax Viewer can also rotate images clockwise or anti-clockwise, start a slideshow of all or selected images in the folder, or e-mail them by selecting the "Send To Mail Recipient" option. Further options allow the image to be mailed full size, or in pixel dimensions of: 640 x 480, 800 x 600, and 1024 x 768. Using Tweak UI, the time between images during a slideshow can be adjusted. Windows Picture and Fax Viewer recognizes embedded ICC V2 color profiles in JPG and TIFF files. GIF files are shown with full animation, even when zoomed. TIFF files can be annotated using the Annotation Toolbar which appears at the bottom of the screen. Lines can be drawn on the TIFF image and text added to it. Areas of the image can be selected and concealed. The Windows Picture and Fax Viewer is also capable of viewing multi-page TIFF files. However TIFF images with JPEG compression are not fully supported. The last button on the standard toolbar opens the image for editing; by default, in Microsoft Paint; however any editing application can be registered for this button in the viewer. Windows Picture and Fax Viewer saves and remembers its window position and size and supports keyboard shortcuts for all of its operations. Raw image formats, which are the preferred formats in professional photography are not supported, however, Microsoft released a later update called RAW Image Thumbnailer and Viewer for Windows XP for viewing certain raw image files. Customization and usability improvements Windows XP includes a new set of visual styles, known by its codename, "Luna". Available in three color schemes, the interface is more task-based than the basic one included since Windows 95, with options available in Explorer windows to interact with each file. The user can however choose to fully revert to the pre-Windows XP "classic" user interface. Developers can take advantage of visual styles through the use of Comctl32.dll v6.0 in their programs. Windows XP's Display Properties allows users to save their customizations as Themes. This feature was previously a part of Microsoft Plus!. Icon and cursor support for 24-bit color depth with an 8-bit alpha channel. Microsoft contracted The Iconfactory which created over 100 colorful icons for Microsoft to be included in Windows XP. The 10-icon resource limit has also been increased. For high DPI displays, Windows XP supports larger cursor sizes. Use of bullets instead of asterisks in password fields of a TextBox control, i.e., "•••" instead of "***". Several informational, critical and warning messages in Windows XP are shown as balloon notifications which automatically fade away after predefined interval and condition, instead of showing them as dialog boxes which require interaction from the user. New configurable sound events for Device Connect, Device Disconnect, Device Failed to Connect, Print Complete, New fax, Fax Error, System Notification, Windows Logon and Windows Logoff. A rich set of live orchestral recordings for the Windows XP tour theme music and system sounds was composed by composer Bill Brown. The famous music that plays during the Out-of-box experience, the setup at first launch where the user could connect to the internet, choose whether to have automatic updates, and choose their username, is located at C:\Windows\system32\oobe\images\title.wma. The piece is named "Velkommen" and was composed by Stan LePard. However, many users did not hear the music as most sound card drivers would be installed after this setup process. This piece was also used in the tour for Internet Explorer 3 Starter Kit. Window ghosting that allows the user to minimize, move or close the main window even if the application is not responding. Text Services Framework The Text Services Framework (TSF), is a COM framework and API introduced in Windows XP that supports advanced text input and text processing. The Text Services Framework is designed to offer advanced language and word processing features to applications. It supports features such as multilingual support, keyboard drivers, handwriting recognition, speech recognition, as well as spell checking and other text and natural language processing functions. It is also downloadable for older Windows operating systems. The Language Bar is the core user interface for Text Services Framework. The language bar enables text services to add UI elements to the toolbar and enables these elements when an application has focus. From the Language Bar, users can select the input language, and control keyboard input, handwriting recognition and speech recognition. The language bar also provides a direct means to switch between installed languages, even when a non-TSF-enabled application has focus. Performance and kernel improvements The Windows XP kernel is completely different from the kernel of the Windows 9x/Me line of operating systems. Although an upgrade of the Windows 2000 kernel, there are major scalability, stability and performance improvements, albeit transparent to the end user. Processor support Windows XP includes simultaneous multithreading (hyperthreading) support. Simultaneous multithreading is a processor's ability to process more than one data thread at a time. Memory management Windows XP supports a larger system virtual address space –— 1.3 GB, of which the contiguous virtual address space that can be used by device drivers is 960 MB. The Windows XP Memory Manager is redesigned to consume less paged pool, allowing for more caching and greater availability of paged pool for any component that needs it. The total size of memory-mapped files in Windows 2000 was limited because the memory manager allocated the Prototype Page Table entries (PPTEs) for the entire file, even if an application created mapped views to only parts of the file. In Windows XP, the Prototype PTEs are only allocated when required by an application, allowing larger mapped files. A benefit of this, for example, is in case of making backups of large files on low memory systems. The paged pool limit of 470 MB has been lifted from the Memory Manager in Windows XP, with unmapped views dynamically reusable by the memory manager depending on pool usage. Memory pages in working sets are trimmed more efficiently for multiprocessor systems depending on how recently they were accessed. Lock contention is reduced, as a number of unnecessary locks used in resource synchronizations (RAM allocation and mapping through Address Windowing Extensions, system page table entries, charging non-paged/paged pool quotas, charging commitment of pages) have been removed. The dispatcher lock contention has been reduced and the Page Frame Number (PFN) lock has been optimized for increased parallelism and granularity. Windows XP uses push locks on the event synchronization object if there is no contention as they support shared and exclusive acquisition. Push locks protect handle table entries in the Executive, and in the Object Manager (to protect data structures and security descriptors) and Memory Manager (to protect AWE-related locks). Windows XP uses the SYSENTER/SYSEXIT mechanisms which require fewer clock cycles to transition to and from user mode to kernel mode to speed up system calls. The kernel page write protection limit in Windows XP is enabled on systems up to 256 MB of RAM beyond which large pages are enabled for increased address translation performance. Windows XP introduces the CreateMemoryResourceNotification function which can notify user mode processes of high or low memory availability so applications can allocate more memory or free up memory as necessary. Registry In versions of Windows prior to Windows XP, the registry size was limited to 80% of the paged pool size. In Windows XP, the registry is reimplemented outside of the paged pool; the registry hives are memory mapped by the Cache Manager into the system cache, eliminating the registry size limit. The registry size is now limited only by the available disk space. The System hive still has a maximum size, but it has been raised from 12 MB to 200 MB, eliminating the issue previous Windows versions faced of being unable to boot because of a large or fragmented System hive. The Configuration Manager has been updated to minimize the registry's memory footprint and lock contention, reduce fragmentation and thus page faults when accessing the registry, and improved algorithms to speed up registry query processing. An in-memory security cache eliminates redundant security descriptors. Debugging Windows XP supports cross user session debugging, attaching the debugger to a non-crashing user-mode program, dumping the process memory space using the dump command, and then detaching the debugger without terminating it. Debugging can be done over a FireWire port and on a local system. The debug heap can be disabled and the standard heap be used when debugging. Vectored Exception Handling Windows XP introduces support for Vectored Exception Handling. Vectored Exception Handling is made available to Windows programmers using languages such as C++ and Visual Basic. VEH does not replace Structured Exception Handling (SEH), rather VEH and SEH coexist with VEH handlers having priority over SEH handlers. Compared with SEH, VEH works more like a traditional notification callback scheme. Applications can intercept an exception by calling the AddVectoredExceptionHandler API to watch or handle all exceptions. Vectored handlers can be chained in order in a linked list and they aren't tied to the stack frame, so they can be added anywhere in the call stack unlike SEH's try/catch blocks. Heap Heap leak detection can be enabled when processes exit and a debugger extension can be used to investigate leaks. Also introduced is a new heap performance-monitoring counter. Windows XP introduces a new low fragmentation heap policy (disabled by default) which allocates memory in distinct sizes for blocks less than 16KB to reduce heap fragmentation. The Low Fragmentation Heap can be enabled by default for all heaps using the LFH Heap Enabler utility. I/O There are new APIs for IRP cancellation and registering file system filter callbacks to intercept the OS fast I/O functions. In low memory conditions, "must succeed" calls are denied, causing a slowdown but preventing a bug check. I/O is throttled to fetch only one memory page at a time increasing overall scalability. File System Windows XP includes NTFS 3.1, which expands the Master File Table (MFT) entries with a redundant MFT record number, useful for recovering damaged MFT files. The NTFS conversion utility, Convert.exe, supports a new /CvtArea switch so that the NTFS metadata files can be written to a contiguous placeholder file, resulting in a less fragmented file system after conversion. NTFS 3.1 also supports symbolic links although there are no tools or drivers shipped with Windows XP to create symbolic links. Windows XP introduces the ability to mount NTFS read-only volumes. There are new APIs to preserve original short file names, to retrieve a list of mount points (drive letters and mounted folder paths) for the specified volume, and to enable applications to create very large files quickly by setting the valid data length on files without force-writing data with zeroes up to the VDL (SetFileValidData function). For instance, this function can be used to quickly create a fixed size virtual machine hard disk. The default access control lists for newly created files are read-only for the Users group and write permissions are given only to the Administrators group, the System account and the owner. Faster boot and application launch The ability to boot in 30 seconds was a design goal for Windows XP, and Microsoft's developers made efforts to streamline the system as much as possible; The Logical Prefetcher is a significant part of this; it monitors what files are loaded during boot, optimizes the locations of these files on disk so that less time is spent waiting for the hard drive's heads to move and issues large asynchronous I/O requests that can be overlapped with device detection and initialization that occurs during boot. The prefetcher works by tracing frequently accessed paged data which is then used by the Task Scheduler to create a prefetch-instructions file at %WinDir%\Prefetch. Upon system boot or the launch of an application, any data and code in the trace that is not already in memory is prefetched from the disk. The previous prefetching results determine which scenario benefited more and what should be prefetched at the next boot or launch. The prefetcher also uses the same algorithms to reduce application startup times. To reduce disk seeking even further, the Disk Defragmenter is called in at idle time to optimize the layout of these specific files and metadata in a contiguous area. Boot and resume operations can be traced and analyzed using Bootvis.exe. Logon and logoff changes Windows XP includes a Fast Logon Optimization feature that performs logon asynchronously without waiting for the network to be fully initialized if roaming user profiles are not set up. Use of cached credentials avoids delays when logging on to a domain. Group Policy is applied in the background, and startup or logon scripts execute asynchronously by default. Windows XP reconciles local and roaming user profiles using a copy of the contents of the registry. The user is no longer made to wait as in Windows 2000 until the profile is unloaded. Windows XP saves locked registry hives with open keys after 60 seconds so that roaming profile changes can be saved back to the server. The problem left is that the computer cannot recover the memory the profile uses until it can be unloaded. To make sure the user profiles are completely reconciled correctly during logoff, Microsoft has released the User Profile Hive Cleanup service for Windows XP, which they later included in Windows Vista. User data and settings management Roaming user profiles Windows XP offers enhancements for usability, resilience against corruption and performance of roaming user profiles. There are new Group Policies to prevent propagation of roaming user profile changes to the server, give administrators control over users' profile folders and preventing the use of roaming user profiles on specific computers. To accommodate the scenario where an older profile would overwrite a newer server profile due to Windows XP's Fast Logon feature, Windows XP ensures in such a situation that the user registry hive is copied from the server to the local profile. Deletion of profiles marked for deletion at the next logoff does not fail for locked profiles. For workgroup computers, Windows XP no longer deletes the profiles of users belonging to the Guests group. Offline Files Windows XP includes some changes to the behavior of Offline Files. The Offline Files Client-Side Cache can now be encrypted with Encrypting File System. Shared folders from DFS namespaces can be made available offline. Also, roaming user profiles can be synchronized with the server even if Offline Files has marked the server as unavailable. Folder Redirection Beginning with Windows XP, folders redirected to the network are automatically made available offline using Offline Files, although this can optionally be disabled through Group Policy. For older Windows NT 4.0 and earlier systems with legacy directory structure, Windows XP allows redirecting the My Documents folder to their home directory. Reliability improvements System Restore In Windows XP, there are some improvements made to System Restore compared to Windows Me. System Restore uses a copy-on-write file system filter driver for taking snapshots. In Windows XP, System Restore is configurable per volume and the data stores are also stored per volume. On NTFS volumes, the Restore Points are stored using NTFS compression and protected using ACLs. A Disk Cleanup handler allows deleting all but the most recent Restore Point. Besides the Registry hives and system files, COM+ and WMI databases and the IIS metabase can also be restored. System Restore supports Group Policy. System Restore in Windows XP also works without issues with EFS-encrypted files. Automated System Recovery Automated System Recovery is a feature that provides the ability to save and restore Windows and installed applications, the system state, and critical boot and system files from a special backup instead of a plain reinstall. ASR consists of two components - backup and restore. The Backup portion located in NTBackup backs up the system state (Windows Registry, COM+ class registration database, Active Directory and the SYSVOL directory share), and the volumes associated with operating system components required to start Windows after restore as well as their configuration (basic or dynamic). The Restore portion of ASR is accessed by pressing F2 from Windows XP Text mode Setup. Automated System Recovery can even restore programs and device drivers if they are added to the ASR Setup information disk. ASR does not restore data files. Side-by-side (SxS) assemblies and Application isolation A common issue in previous versions of Windows was that users frequently suffered from DLL hell, where more than one version of the same dynamically linked library (DLL) was installed on the computer. As software relies on DLLs, using the wrong version could result in non-functional applications, or worse. Windows 98 Second Edition and Windows 2000 partially solved this problem for native code by introducing side-by-side component sharing and DLL/COM redirection. These operating systems allowed loading a private version of the DLL if it was placed in the application's folder by the developer, instead of the system directory and must be registered properly with the system. Windows XP improves upon this by introducing side-by-side assemblies for COM+ 2.0, .NET, COM classic, and Win32 components (C Runtime, GDI+, Common Controls). The technology keeps multiple digitally signed versions of a shared DLL in a centralized WinSxS folder and runs them on demand to the appropriate application keeping applications isolated from each other and not using common dependencies. Manifests and the assembly version number are used by the OS loader to determine the correct binding of assembly versions to applications instead of globally registering these components. To achieve this, Windows XP introduces a new mode of COM object registration called Registration-free COM (or RegFree COM). It allows Component Object Model (COM) components to store activation metadata and CLSID (Class ID) for the component without using the registry. Instead, the metadata and CLSIDs of the classes implemented in the component are declared in an assembly manifest (described using XML), stored either as a resource in the executable or as a separate file installed with the component. This allows multiple versions of the same component to be installed in different directories, described by their own manifests, as well as XCOPY deployment. During application loading, the Windows loader searches for the manifest. If it is present, the loader adds information from it to the activation context When the COM class factory tries to instantiate a class, the activation context is first checked to see if an implementation for the CLSID can be found. Only if the lookup fails is the registry scanned. Windows Error Reporting Windows Error Reporting collects and offers to send post-error debug information (a memory dump) using the internet to the developer of an application that crashes or stops responding on a user's desktop. No data is sent without the user's consent. When a dump (or other error signature information) reaches the Microsoft server, it is analyzed and a solution is sent back to the user if one is available. Windows Error Reporting runs as a Windows service and can optionally be entirely disabled. Software and hardware manufacturers may access their error reports using Microsoft's Winqual program. Software and hardware manufacturers can also close the loop with their customers by linking error signatures to Windows Error Reporting Responses. This allows distributing solutions as well as collecting extra information from customers (such as reproducing the steps they took before the crash) and providing them with support links. Device Driver Rollback On old versions of Windows, when users upgrade a device driver, there is a chance the new driver is less stable, efficient or functional than the original. Reinstalling the old driver can be a major hassle and to avoid this quandary, Windows XP keeps a copy of an old driver when a new version is installed. If the new driver has problems, the user can return to the previous version. This feature does not work with printer drivers. Other driver enhancements Windows Driver Protection blocks known problematic drivers from installing or loading The Driver Verifier introduced in Windows 2000 is a tool that replaces the default operating system subroutines with ones that are specifically developed to catch device driver bugs. Once enabled, it monitors and stresses drivers to detect illegal function calls or actions that may be causing system corruption. In Windows XP, new verification options have been added for DMA, I/O, SCSI and deadlock detection to Driver Verifier. Driver Verifier Manager, a GUI is introduced for Driver Verifier and includes the ability to automatically verify unsigned drivers. Last Known Good Configuration in Windows 2000 restored the hardware configuration in the registry control set indicated by the LastKnownGood key instead of the default. In Windows XP, it is extended to support restoring the device drivers too of the last working configuration, should a newly installed device driver make Windows unbootable. Application compatibility As Windows XP merged the consumer and enterprise versions of Windows, it needed to support applications developed for the popular and consumer-oriented Windows 9x platform on the Windows NT kernel. Microsoft addressed this by improving compatibility with application-specific tweaks and shims and by providing tools such as the Application Compatibility Toolkit (AppCompat or ACT) to allow users to apply and automate these tweaks and shims on their own applications. Users can script the Compatibility Layer using batch files. Windows XP Setup also includes a compatibility checker that warns users - before setup begins - of incompatible applications and device drivers or of applications that may need reinstallation. Media features Windows Media Player Windows XP RTM includes Windows Media Player version 8 (officially called Windows Media Player for Windows XP) and Windows Media 8 codecs. Windows Media Player for Windows XP introduced ID3 support for MP3s, editing media information from within the Library, adding lyrics for MP3 or WMA tracks, file name customization when ripping, new visualizations, support for HDCDs, ability to lock down the player in a corporate environment and DVD playback support (when appropriate codecs are installed separately). Windows Media Player also incorporates newer hardware support for portable devices by means of the Media Transfer Protocol and the User-Mode Driver Framework-based Windows Portable Devices API. Windows Movie Maker The original RTM release of Windows XP included Windows Movie Maker 1.1 which added non-compressed DV AVI recording of digital video sources. Windows Movie Maker 2 introduced numerous new transitions, effects, titles and credits, a task pane, resizable preview window with dimensions, improved capture and export options, an AutoMovie feature, saving the final video back to tape and custom WMV export profiles. Windows XP Media Center Edition 2005 includes Windows Movie Maker 2.5 which includes DVD burning. TV and video capture technologies Windows XP includes advances in Broadcast Driver Architecture for receiving and capturing analog and digital TV broadcasts complete with signal demodulation, tuning, software de-multiplexing, electronic program guide store, IP data broadcasting etc. In addition, Windows XP Media Center Edition introduced Windows Media Center, an application for PVR-like recording and playback features for TV content. Windows XP includes improved FireWire (IEEE 1394) support (DVCPRO25 - 525-60 and 625-50) for digital video cameras and audio video devices. It introduces MSTape, a WDM driver for D-VHS and MPEG camcorder devices. Video playback DirectShow 8 introduces the Video Mixing Renderer-7 (VMR-7) filter which uses DirectDraw 7 for video rendering, replacing the Overlay Mixer. VMR-7 can mix multiple streams and graphics with alpha blending, allowing applications to draw text (such as closed captions) and graphics (such as channel logos or UI buttons) over the video without flickering, and support compositing to implement custom effects and transitions. VMR-7 also supports source color keying, overlay surface management, frame-stepping and improved multiple-monitor support. VMR-7 features a "windowless mode" for applications to easily host video playback within any window and a "renderless playback mode" for applications to access the composited image before it is rendered. DirectX 9 introduced the VMR-9 which uses Direct3D 9 instead of DirectDraw, allowing developers to transform video images using the Direct3D pixel shaders. DirectShow 8 includes AVStream, a multimedia class driver for video-only and audio-video kernel streaming. Other media features Windows Media Encoder 9 Series allows encoding Windows Media 9-based content. Installing Windows Media Connect or Windows Media Player 11 adds a UPnP-based streaming media server. Device support improvements Windows XP provides new and/or improved drivers and user interfaces for devices compared to Windows Me and 98. USB 2.0 support Beginning with Windows XP Service Pack 1, generic USB 2.0 Enhanced Host Controller Interface drivers are included. Windows XP also adds support for USB device classes such as Bluetooth, USB video device class, imaging (still image capture device class) and Media Transfer Protocol with Windows Media Player 10. For mass storage devices, Windows XP introduces hardware descriptors to distinguish between various storage types so that the operating system can set an appropriate default write caching policy. For example, for USB devices, it disables write caching by default so that surprise removal of these devices do not cause data loss. Device Manager provides a configuration setting whether to optimize devices for quick removal or for performance. Windows Image Acquisition Windows XP supports both TWAIN as well as Windows Image Acquisition-based scanners. Windows Image Acquisition in Windows XP adds support for Automatic document feeder scanners, scroll-fed scanners without preview capabilities and multi-page TIFF generation. For WIA video, a Snapshot filter driver is introduced which allows still frames to be captured from the video stream. Windows XP SP1 and later support the downloadable WIA Library v2.0 which provides access to WIA functionality through programming languages and scripting environments that support OLE Automation. The Scanner and Camera Wizard based on Windows Image Acquisition and other common dialogs for WIA devices have been improved in Windows XP to show the media information and metadata, rotate images as necessary, categorize them into subfolders, capture images and video in case of a still or video camera, crop and scan images to a single or multi-page TIFF in case of a scanner. The Picture Transfer Protocol (PTP) implementation has been updated to support all mandatory and optional commands in the PTP standard, and object tree support which allows secondary files associated with a parent file to be grouped and transferred concurrently. Windows Media Player 10 also adds the Media Transfer Protocol for transferring media content from portable devices. Thus, for digital cameras, Windows XP supports acquiring photos using any of either WIA, PTP, USB Mass Storage Class or MTP protocols depending on what the camera manufacturer supports. CD burning Windows XP includes technology from Roxio which allows users to directly burn files to a compact disc through Windows Explorer. Previously, end users had to install CD burning software. In Windows XP, CD and DVD-RAM (FAT32 only for DVD-RAM) burning has been directly integrated into the Windows interface. Data discs are created using the Joliet and ISO 9660 file systems and audio CDs using the Redbook standard. To prevent buffer underrun errors, Windows XP premasters a complete image of files to be burnt and then streams it to the disc burner. Users can burn files to a CD in the same way they write files to a floppy disk or to the hard drive via standard copy-paste or drag and drop methods. The burning functionality is also exposed as an API called the Image Mastering API. Windows XP's CD burning support does not do disk-to-disk copying or disk images, although the API can be used programmatically to do these tasks. Creation of audio CDs is integrated into Windows Media Player. Audio CDs are burnt using track-at-once mode. CD-RW discs can be quick erased. API support can be added to Windows XP for burning DVDs and Blu-ray Discs (Mastered-style burning and UDF) on write-once and rewritable DVD and Blu-ray media by installing the Windows Feature Pack for Storage which upgrades IMAPI to version 2. Note that this does not add DVD or Blu-ray burning features to Windows Explorer but third-party applications can use the APIs to support DVD and Blu-ray burning. Power management Support for the Simple Boot Flag (SBF) specification which tells the BIOS to bypass or minimize startup checks if the operating system is Plug and Play capable. Wake-on-Battery support so that the system has time to power off or hibernate CardBus Wake-on-LAN support Wake on LAN can be configured to limit wake up packets to just magic packets from the Power management tab of the NIC property page in Device Manager. LCD dimming when on battery power Processor power and performance control including C-state (run in lower power state when idle) and throttling USB selective suspend feature Significantly noticeable fast boot and resume from hibernation compared to previous Windows versions owing to the boot loader caching file and directory metadata sequentially and in large chunks in a most recently used manner, overlapping device and network initialization, faster boot disk enumeration and class drivers being initialized asynchronously. Hibernation is faster as memory pages are compressed using an improved algorithm, compression is overlapped with disk writes, unused memory pages are freed and DMA transfers are used during I/O. Faster resume from standby as the algorithm used by the Power Manager for notifying hardware and software of power state changes by dispatching power IRPs has been rewritten to maximize parallelism, important system drivers (PCMCIA, keyboard, mouse) have been rewritten to eliminate blocking interactions, and worker thread stacks are locked in memory to prevent interruptions with power operations. Improved ACPI processor performance states for multi-core processors beginning with Windows XP Service Pack 2. Built-in support for processor power management technologies such as Intel SpeedStep and AMD PowerNow!. Audio hardware support Support for audio devices based on the Intel High Definition Audio specification by means of a Universal Audio Architecture (UAA) class driver. Multichannel audio output and playback of additional audio formats. Volume can be set for each speaker in a multichannel configuration. KMixer audio sampling rate supports a maximum of 200 kHz beginning with Windows XP SP1 compared to earlier versions of Windows. Restriction on number of MME/WinMM device interfaces (waveIn, waveOut, midiIn, midiOut, mixer, and aux) is raised from 10 to 32. Hardware acceleration of DirectSound capture effects These include Acoustic Echo Cancellation for USB microphones, noise suppression and array microphone support. USB audio devices support GFX (Global Effects Filters). Sound Blaster 2.0 emulation support in NTVDM Windows XP sets the volume levels on wave, CD Audio and MIDI sliders to 0 dB of attenuation. This prevents signal resolution degradation. FireWire (IEEE 1394) support Windows XP includes FireWire 800 support (1394b) beginning with Service Pack 1. As mentioned in the above section, Windows XP includes improved support for FireWire cameras and audio video devices. S/PDIF audio and MPEG-2 video streams are supported across FireWire from audio video receivers or set-top boxes, DVD or D-VHS, speakers, or TV transmissions. Windows XP supports the AV/C (IEC 61883 protocol for isochronous real-time data transfer for audio-video applications. Windows XP also allows non-FireWire devices to be exposed as virtual FireWire devices. Direct memory access over the 1394 bus from the host to the target allows kernel debugging over FireWire. Finally, there is support for TCP/IP networking and Internet Connection Sharing over the IEEE 1394 bus. Other hardware and driver improvements Details tab in Device Manager which displays various device identification strings such as device instance ID, hardware ID, service name, filters, firmware revision, power state mappings and capabilities etc. Windows XP's user interface for Plug and Play changed with all messages being shown in the notification area as balloon tips. The read-only attribute of files and folders is automatically removed when copying files from optical media using Windows Explorer. Improved mouse pointer ballistics. DualView for multi-monitor setups. DualView allows two monitors to host the Windows desktop, while being driven off of a single display adapter. Support for reading UDF 2.01 upgradeable to UDF 2.50 by installing Windows Feature Pack for Storage. 48-bit LBA support for ATA/ATAPI disk drives beginning with Windows XP SP1. and generic drivers for UltraDMA Mode 5 and 6 support Executing user applications directly from ROM. Support for the exFAT file system can be added by installing KB955704. Support for Secure Digital I/O host controllers and SD/MMC storage devices compliant with SDIO 1.0 beginning with Windows XP SP2 through a Microsoft-supplied bus driver. Later hotfixes and Windows XP SP3 include support for SDHC cards, including those larger than 4 GB but up to 32 GB. Supports VESA display if vendor-specific video driver not installed, or in the safe mode. System administration Windows Script Host 5.6 Windows XP includes Windows Script Host 5.6, a major update to the WSH environment, which includes an improved object model to reduce boilerplate code, stronger security and several other improvements. A new XML-based file format, the Windows Script File format (.WSF) has been introduced besides .VBS and .JS which can store in an XML node in the same file, extra information besides script code, such as digital signature blocks, runtime directives or instructions to import external code. The WSF schema can include jobs wrapped each by a unique <job> tag and an outer <package> tag. Tags in a WSF file allow including external files, importing constants from a TLB, or storing the usage syntax in the <Runtime> element and displaying it using the new ShowUsage method, or when invoked by the /? switch. The WSF format also supports hosting multiple WSH scripting languages, including cross function-calls. The WshShell object now supports a 'CurrentDirectory' read-write method. Scripts can now be digitally signed as well as verified programmatically using the Scripting.Signer object in a script itself, provided a valid certificate is present on the system. Alternatively, the signcode tool from the Platform SDK, which has been extended to support WSH filetypes, may be used at the command line. The VerifyFile method can be used to authenticate the embedded signature's validity and check the script for modifications after signing. WSH can thus decide whether or not to execute the script after verification. Code stored in an in-memory string can also be signed by using the Sign method. The signature block is stored in a commented section in the script file for backward compatibility with older WSH versions. By using Software Restriction Policies supported in Windows XP and later, a system may also be configured to execute only those scripts which have been digitally signed, thus preventing the execution of untrusted scripts. Local scripts can also run on a remote machine with the new WScript.WshController object, which is powered by DCOM. Remote WSH can be enabled through a Group Policy Administrative Template or registry. Remote scripts always run through wscript and are loaded into the remote machine's Server process so they run non-interactively by default, but can be configured using DCOMCNFG to run in a security context that allows them to display the user interface. When the WSH automation server loads, an instance of the WshRemote object is created but the script runs only after calling the Execute method. Any external files called by the remote script must be located on the remote machine in the directory path specified by the Exec method. The remote script can be monitored by using the Status property. WSH 5.6 introduces the Exec method for the WshShell object to execute command-line console applications and has access to the standard I/O streams (StdIn, StdOut, and StdErr) of the spawned process. In earlier versions of Windows Script, to use arguments, one had to access the WshArguments collection object which could not be created externally and required that the person running the script know the order of the arguments, and their syntax and values. WSH 5.6 introduces named arguments on the command line which follow a /string:value or boolean convention defined in 'Runtime' tag and are recognized irrespective of their order on the command line. Named arguments are grouped in the Named collection object and have the usual methods like Item, Count, Length as well as an Exists method. The 'ShowUsage' method for the WshArguments object mentioned earlier shows the argument information in a message box. Windows XP includes a ScriptPW.Password COM automation object, implemented in the scriptpw.dll file which can be used to mask sensitive information like passwords from command line scripts. Remote Desktop Users can log into Windows XP Professional remotely through the Remote Desktop service. It is built on Terminal Services technology (RDP), and is similar to "Remote Assistance", but allows remote users to access local resources such as printers. Any Terminal Services client, a special "Remote Desktop Connection" client, or a web-based client using an ActiveX control may be used to connect to the Remote Desktop. (Remote Desktop clients for earlier versions of Windows, Windows 95, Windows 98 and 98 Second Edition, Windows Me, Windows NT 4.0, or Windows 2000 have been made available by Microsoft. This permits earlier versions of Windows to connect to a Windows XP system running Remote Desktop, but not vice versa.) There are several resources that users can redirect from the remote server machine to the local client, depending upon the capabilities of the client software used. For instance, "File System Redirection" allows users to use their local files on a remote desktop within the terminal session, while "Printer Redirection" allows users to use their local printer within the terminal session as they would with a locally or network shared printer. "Port Redirection" allows applications running within the terminal session to access local serial and parallel ports directly, and "Audio" allows users to run an audio program on the remote desktop and have the sound redirected to their local computer. The clipboard can also be shared between the remote computer and the local computer. The RDP client in Windows XP can be upgraded to 7.0. The Remote Desktop Web Connection component of Internet Information Services 5.1 also allows remote desktop functionality over the web through an ActiveX control for Internet Explorer. Remote Assistance Remote Assistance allows a Windows XP user to temporarily take over a remote Windows XP computer over a network or the Internet to resolve issues. As it can be a hassle for system administrators to personally visit the affected computer, Remote Assistance allows them to diagnose and possibly even repair problems with a computer without ever personally visiting it. Remote Assistance allows sending invitations to the support person by email, Windows Messenger or saving the invitation as a file. The computer can be controlled by both, the support person connecting remotely as well as the one sending the invitation. Chat, audio-video conversations and file transfer are available. Fast user switching and Welcome Screen Windows XP introduces Fast User Switching and a more end user friendly Welcome Screen with a user account picture which replaces the Classic logon prompt. Fast user switching allows another user to log in and use the system without having to log out the previous user and quit his or her applications. Previously (on both Windows Me and Windows 2000) only one user at a time could be logged in (except through Terminal Services), which was a serious drawback to multi-user activity. Fast User Switching, like Terminal Services, requires more system resources than having only a single user logged in at a time and although more than one user can be logged in, only one user can be actively using their account at a time. This feature is not available when the Welcome Screen is turned off, such as when joined to a Windows Server Domain or with Novell Client installed. Even when the Welcome screen is enabled, users can switch to the Classic logon by pressing Ctrl+Alt+Del twice at the Welcome screen. Windows Installer Windows XP introduced Windows Installer (MSI) 2.0. Windows Installer 2.0 brought major improvements such as installation and management of side by side and CLR assemblies, sandboxing MSI custom actions, improved event logging and hiding sensitive information in log files, per-user program isolation, digital signatures, improved patching (more robust patch conflict resolution and reduced unnecessary unversioned file copying and source prompts), Terminal Server support and integration with System Restore and Software Restriction Policies. Windows XP Service Pack 2 includes Windows Installer 3.0 which also adds numerous improvements to patching such as patch uninstallation support through Add or Remove Programs, binary delta patches, patch sequencing to install patches in the correct order, installing multiple patches for different products in one transaction, eliminating source media requests for delta compression patches, patch elevation for limited user accounts, MSI source location list and inventory management APIs, and fixing numerous bugs. Windows XP can be updated to Windows Installer 4.5. Disk Defragmenter Windows Disk Defragmenter was updated to alleviate several restrictions. It no longer relies on the Windows NT Cache Manager, which prevented the defragmenter from moving pieces of a file that cross a 256KB boundary within the file. All parts of a stream including the cluster boundary for non-compressed files, reparse points, bitmaps, and attribute_lists, NTFS metadata files, EFS-encrypted files and the NTFS Master File Table can be defragmented. The defragmenter supports NTFS volumes with cluster sizes larger than 4 kilobytes. A command-line tool, defrag.exe, has been included, providing access to the defragmenter from cmd.exe and Task Scheduler. Users who are members of the Power Users group can schedule defragmentation. Windows Task Manager Windows Task Manager incorporates a number of improvements in Windows XP. It has been updated to display process names longer than 15 characters in length on the Processes tab, which used to be truncated in Windows 2000. Session ID and User name columns have been added on the Processes tab. The Delete key can also be used to terminate processes on the Processes tab. A new Networking tab shows statistics relating to each of the network adapters present in the computer. By default the adapter name, percentage of network utilization, link speed and state of the network adapter are shown, along with a chart of recent activity. More options can be shown by choosing Select columns... from the View menu. The Users tab shows all users that currently have a session on the computer. On server computers there may be several users connected to the computer using Terminal Services. There may also be multiple users logged onto the computer at one time using Fast User Switching. Users can be disconnected or logged off from this tab. A Shutdown menu has been introduced that allows access to Standby, Hibernate, Turn off, Restart, Log Off and Switch User. Holding down Ctrl while clicking New Task opens a command prompt. WMI Windows XP introduces WMIC.exe, the Windows Management Instrumentation console utility Beginning with Windows XP, WMI resides in a shared service host process called Wmiprvse.exe which can spawn multiple instances under different accounts: LocalSystem, NetworkService, or LocalService. Previously, WMI providers were loaded in-process with the WMI Service and a single WMI provider crashing led to the restart of the WMI core service, WinMgmt.exe. In Windows XP, MOF files are used to describe system ETW events. WMI Filters for Group Policy were introduced. Command-line tools Windows XP includes new command-line tools and WMI-based scripts: schtasks.exe (Windows Task Scheduler) shutdown.exe (Shutdown commands) Sc.exe (Service Control Manager) gpupdate.exe and gpresult.exe (Group Policy) logman.exe, relog.exe, typeperf.exe and tracerpt.exe (Performance Monitor) Eventquery.vbs, eventcreate.exe, EventTriggers.exe (Event log) DSquery.exe, dsget.exe, dsadd.exe, dsmod.exe, dsmove.exe, dsrm.exe (Active Directory) diskpart.exe, Defrag.exe and fsutil.exe (Disk management, Defragmentation and file system management) bootcfg.exe (Boot.ini) openfiles.exe (Networking) powercfg.exe (Power management) tasklist.exe, taskkill.exe, getmac.exe, systeminfo.exe, driverquery.exe, reg.exe, regini.exe, IPseccmd.exe (Windows 2000 Resource Kit). IIS*.vbs (IIS and Active Server Pages management) Prn*.vbs (Printing) Pagefileconfig.vbs (PageFile configuration) bitsadmin.exe, bindiff.exe, cabarc.exe, ftonline.exe, httpcfg.exe, ipseccmd.exe, netcap.exe, rasdiag.exe, spcheck.exe, tracepdb.exe (New support tools) Other management features CHKDSK has performance improvements. Non-persistent Shadow Copy (Volume Snapshot Service) support that uses a copy-on-write technique in order to create a snapshot and APIs to use the same MSConfig utility has been updated to configure advanced Boot.ini options graphically, enable or disable Windows services and launch built-in tools. NTBackup has a wizard-based interface for ease of use and supports backing up locked (in-use) files using Shadow Copy. Media pools created by NTBackup can also be viewed from the backup utility itself without opening Removable Storage Management. Microsoft Management Console 2.0 which introduced an automation object model, view extensions, visual style support, Console Taskpads etc. Increased number of WMI providers and classes. Unified Registry editor that combines Windows 9x's Regedit.exe and Windows NT's Regedt32.exe. The Registry Editor now supports multiple instances if the -m switch is specified. IExpress as part of Internet Explorer 6 to create self-extracting INF-based installation packages. Files and Settings Transfer Wizard and User State Migration Tool Several deployment tools improvements including enhancements to Sysprep, Setup Manager, introduction of WinPE. For example, the Product Key stored in the Answer file for Setup Manager or Sysprep can be stored encrypted. Sysprep can add updated drivers to an installation image with per-machine customizations. The time to preload Windows XP using Sysprep has been reduced using a scriptable WinBOM.ini file that drives Sysprep. Unattended installations are improved in Windows XP with far more comprehensive configuration options for various operating system components. Several improvements have been made to the Package Installer (Update.exe) over Windows 2000. Increased number of Group Policies, including security policies and Resultant Set of Policy (RSoP) management console which allows administrators to see applied policies in logging mode or simulate policy settings that will be applied before committing to changes to objects in planning mode. A Desktop Cleanup Wizard was introduced to help users reduce clutter on their desktops, by looking at the shortcuts on the Desktop and moving any unused ones into a directory called "Unused Desktop Shortcuts". The Desktop Cleanup Wizard operates as a scheduled task that runs once a day to determine if it's been 60 days since the last time the wizard was run. Windows XP can be upgraded to from Windows 98, Windows Me, Windows NT 4.0 Workstation and Windows 2000 Professional. If performing an upgrade setup from Windows 9x family, Windows XP takes a backup of the old installation so that the user can uninstall Windows XP or if setup fails at any point, the system goes back to the previous OS. If Setup completes successfully, users are asked whether they want to delete the backup. This feature is not available when upgrading from Windows 2000 Professional. Windows XP includes a Shutdown Event Tracker (disabled by default) which when enabled from Group Policy allows administrators to document shutdown reasons and analyze the shutdown logs stored in the System log over time to develop an understanding of the cause for most shutdowns. Administrators can choose from a predefined set of reasons or enter their own reasons. Shutdown Event Tracker also takes a system state snapshot just before each shutdown to identify usage of system resources. Windows XP Setup includes a new Quick format option to quickly format large volumes without checking the entire volume for bad sectors. Security features Data Protection API hardening In Windows 2000, an NTLM hash of the user's password was a requirement which technically allowed a potential malefactor to decrypt the Master Key and the NTLM hash directly from the Security Accounts Manager database. Windows XP improves DPAPI security by encrypting the Master Key using an SHA1 hash of the password. This also improves the security of data encrypted with Encrypting File System. PKI support Windows XP PKI supports cross-certification and Bridge CA scenarios. User-type certificates can be auto-enrolled and renewed. Certificate requests for issuing new certificates or renewing expired ones can be pending until administrator approval or until issued by the certificate authority and once approved, they install automatically. Root CA certificates now also auto-update via Microsoft Update. Windows XP also supports delta CRLs (CRLs whose status has changed since the last full base compiled CRL) and base64-encoded CRLs for revocation checking and will use them by default. Windows XP can enroll version 2 certificate templates which have many configurable attributes. Smart cards can be used to log into terminal server sessions (when connecting to a Windows Server 2003 or higher Terminal Server), with CAPICOM or with system tools such as net.exe and runas.exe. There are also numerous improvements to certificate status checking, chain building and revocation checking, path validation and discovery. Windows XP Service Pack 3 adds SHA-2 hashing algorithms (SHA256, SHA384 and SHA512) to the CryptoAPI for validating X.509 certificates. Encrypting File System Windows XP includes several Encrypting File System improvements The most notable improvement is that multiple user accounts can share access to encrypted files on a file-by-file basis. A Details button in the Advanced file attributes dialog in the file's properties allows adding or removing additional users who can access the EFS-encrypted file, and viewing the certificate thumbprint and the Data Recovery Agent account. EFS certificates are autoenrolled in the CA and there is support for revocation checking on certificates used when sharing encrypted files. Unlike Windows 2000, there is no default local Data Recovery Agent and no requirement to have one, although a self-signed certificate for the recovery agent can be generated using cipher.exe. The DPAPI Master Key can be protected using a domain-wide public key. A stronger FIPS 140-1 compliant algorithm such as 3DES can be used. Windows XP Service Pack 1 adds support for and the default use of AES-256 symmetric encryption algorithm for all EFS-encrypted files. With KB912761 for Windows XP SP2 or on Windows XP SP3, users can configure whether EFS generates a self-signed certificate when a certificate authority is unavailable. Windows XP also warns the user if the EFS encrypted files are being copied to a file system such as FAT or unsupported location which does not support EFS, and thus the file is going to get decrypted. Windows XP can also encrypt files on a remote server with NTFS if the server is trusted for delegation in Active Directory and the user's certificate and private key are loaded in the local profile on the server. If a roaming user profile is used, it will be copied locally. On a WebDAV server mapped by a drive letter, Windows XP can encrypt the file locally and transport it as a raw encrypted file to the WebDAV server using the HTTP PUT command. Similarly, EFS encrypted files can be downloaded raw from the WebDAV and decrypted locally. The command line utilities cipher, copy and xcopy have been updated in Windows XP. EFS can also be completely disabled in Windows XP through Group Policy (for a domain) or through the registry (for a non-domain computer). For faster cache validation, the time for how long the user session key and certificate chain are cached can be adjusted. Password Reset Wizard Starting with Windows XP, a password reset disk can be created using the Forgotten Password wizard. This disk can be used to reset the password using the Password Reset Wizard from the logon screen. The user's RSA private key is backed up using an offline public key whose matching private key is stored in one of two places: the password reset disk (if the computer is not a member of a domain) or in Active Directory (if it is a member of a domain). An attacker who can authenticate to Windows XP as LocalSystem still does not have access to a decryption key stored on the PC's hard drive. If the password is reset, the DPAPI master key is deleted and Windows XP blocks all access to the EFS encrypted files to prevent offline and rogue attacks and protect the encrypted files. If the user changes the password back to the original password, EFS encrypted files can be recovered. Credential Manager Windows XP prompts for credentials upon authentication errors and allows saving those that use Integrated Windows Authentication to a secure roaming keyring store protected by the Data Protection API. Saved credentials can be managed from the Stored User Names and Passwords item in the User accounts control panel. If a certificate authority is present, then users can a select an X.509 certificate when prompted for credentials. When that same resource is accessed again, the saved credentials will be used. Remote access/VPN connections also create temporary credentials in the keyring to make the experience seamless. Credential Manager also exposes an API for Single Sign On. Software Restriction Policies Windows XP introduces Software Restriction Policies and the Safer API By use of Software Restriction Policies, a system may be configured to execute or install only those applications and scripts which have been digitally signed or have a certain trust level, thus preventing the execution of untrusted programs and scripts. Administrators can define a default rule using the Local Security Policy snap-in, and exceptions to that rule. The types of rules include: Hash Rule, Path Rule, Certificate Rule and Zone Rule which identify a file by its hash, path, software publisher's certificate or Internet Explorer-zone respectively. For example, an ActiveX control can be restricted to run only for a particular domain by specifying a certificate rule-based software restriction policy. Other security and privacy features Each logon session receives its own set of drive letters. They cannot be shared. The Security permissions user interface is improved over Windows 2000. A new property sheet called Effective Permissions evaluates implicit permissions against explicit permissions and assigned permissions against inherited permissions. When setting object permissions, the user names, groups and security principals can be searched on the domain by specific criteria. The Secondary logon (Run As) feature allows running programs with a restricted token if the Protect my computer and data from unauthorized program activity option is checked. For non-domain computers, network logons and secondary logons (Run As) are disabled for user accounts with blank passwords. Only logons from the main physical console logon screen will be allowed for blank passwords. If the Security Accounts Manager (SAM) database is deleted from another OS, Windows XP will not allow bypassing the logon and will show an error message and then shut down the computer. Digest SSP for HTTP and LDAP queries between Windows and non-Windows systems where Kerberos is not available. Credentials Security Service Provider (CredSSP) in Windows XP SP3 (Disabled by default) which provides Single sign-on and Network Level Authentication for Remote Desktop Services. IPsec configuration for server or domain isolation is simplified with the Simple Policy Update which reduces the number of IPsec filters from many hundreds of filters to only two filters. The Everyone user group no longer includes the Anonymous SID. Windows XP introduced the LOCAL SERVICE and NETWORK SERVICE accounts to run certain Windows services in isolation so that the privileges and access assigned to services is reduced to just those needed for their roles. This way, any potential attack surface is reduced when an attacker is exploiting the service. AuthZ API which implements the NT kernel Security Reference Monitor in user mode for applications to protect objects. P3P support in Internet Explorer 6 Networking and communication features Wi-Fi networks Windows 2000 wireless support did not support seamless roaming and auto-configuration. Windows XP's Wireless Zero Configuration service supports automatic wireless network configuration with re-authentication when necessary thus providing seamless roaming capability and setting the preferred order of connections. In the absence of a wireless access point, Windows XP can set up an ad hoc wireless network. There is native support for WPA and WPA2 authentication in infrastructure networks with the latest service packs and/or updates applied. Windows XP includes a Wireless Network Setup Wizard which supports the Windows Connect Now: USB Flash Drive (WCN-UFD) method to ease setting up the wireless network for inexperienced users. Windows XP can connect to hotspots created using Wireless Provisioning Services. Internet Connection Sharing In Windows XP, Internet Connection Sharing is integrated with UPnP, allowing remote discovery and control of the ICS host. It has a Quality of Service Packet Scheduler component. When an ICS client is on a relatively fast network and the ICS host is connected to the internet through a slow link, Windows may incorrectly calculate the optimal TCP receive window size based on the speed of the link between the client and the ICS host, potentially affecting traffic from the sender adversely. The ICS QoS component sets the TCP receive window size to the same as it would be if the receiver were directly connected to the slow link. Internet Connection Sharing also includes a local DNS resolver in Windows XP to provide name resolution for all network clients on the home network, including non-Windows-based network devices. ICS is also location-aware, that is, when connected to a domain, the computer can have a Group Policy to restrict the use of ICS but when at home, ICS can be enabled. Quality of Service for modems and remote access When multiple applications are accessing the internet simultaneously without any QoS and the connection isn't fast enough, the TCP receive window size is set to the full window of data in transit that the first application uses in the connection until a steady state is reached. Subsequent connections made by other applications will take much longer to reach an optimal window size and the transmission rate of the second or third application will always be lower than that of the application that established the connection first. On such slow links, the QoS component in Windows XP automatically enables a Deficit round robin scheduling scheme, which creates a separate queue for each application and services these queues in a round-robin fashion. IPv6 support There is basic but production quality support in Windows XP for IPv6 and Teredo tunneling through the Advanced Networking Pack later incorporated into Windows XP SP2. IPv6 has to be installed and configured from the command line using the netsh interface ipv6 context as there is no GUI support. After the network interface's link-local address is assigned, stateless autoconfiguration for local and global addresses can be performed by Windows XP. Static IPv6 addresses can be assigned if there is no IPv6 router on the local link. Transition mechanisms such as manually configured tunnels and 6to4 can be set up. Windows Firewall beginning with Windows XP SP2 also supports IPv6 stateful filtering. Applications and tools such as the Telnet client, FTP client, ping, nslookup, tracert, DNS resolver, file and print sharing, Internet Explorer, IIS have been updated to support IPv6. Privacy extensions are enabled and used by default. 6to4 is automatically activated for public IPv4 addresses without a global IPv6 address. Other types of tunnels can be set up include: 6over4, Teredo, ISATAP, PortProxy. Teredo also helps traverse cone and restricted NATs. Teredo host-specific relay is enabled when a global IPv6 address has been assigned, otherwise Teredo client functionality is enabled. The Windows XP DNS resolver can only make DNS queries using IPv4, it does not use IPv6 itself as a transport to make the query. However, when a DNS query sends back both IPv4 and IPv6 resource records, IPv6 addresses are preferred. Windows XP does not support DHCPv6 and PPPv6/IPv6CP. An open source DHCPv6 implementation called Dibbler is available, although stateless autoconfiguration largely makes it unnecessary. Background Intelligent Transfer Service Windows XP includes the Background Intelligent Transfer Service, a Windows service that facilitates prioritized, throttled, and asynchronous transfer of files between machines using idle network bandwidth. BITS will only transfer data whenever there is bandwidth which is not being used by other applications, for example, when applications use 80% of the available bandwidth, BITS will use only the remaining 20%. BITS constantly monitors network traffic for any increase or decrease in network traffic and throttles its own transfers to ensure that other foreground applications (such as a web browser) get the bandwidth they need. BITS also supports resuming transfers in case of disruptions. BITS version 1.0 supports only downloads. From version 1.5, BITS supports both downloads and uploads. Uploads require the IIS web server, with BITS server extension, on the receiving side. Windows XP components such as Windows Update use BITS to download updates so only idle bandwidth is used to download updates and downloading can be resumed in case network connectivity is interrupted. BITS uses a queue to manage file transfers and downloads files on behalf of requesting applications asynchronously, i.e., once an application requests the BITS service for a transfer, it will be free to do any other job, or even terminate. The transfer will continue in the background as long as the network connection is there and the job owner is logged in. BITS supports transfers over both HTTP and HTTPS. If a network application begins to consume more bandwidth, BITS decreases its transfer rate to preserve the user's interactive experience, except for Foreground priority downloads. BITS is exposed through Component Object Model (COM), making it possible to use with virtually any programming language. Faxing Windows XP has a Fax Console to manage incoming, outgoing and archived faxes and settings. The Fax Monitor only appears in the notification area when a fax transmission or reception is in progress. If manual reception of faxes is enabled, it appears upon an incoming fax call. Archived faxes open in Windows Picture and Fax Viewer in TIFF format. Upon installing Microsoft Outlook, the Fax Service automatically switches from the Windows Address Book to using Outlook's Address Book. Windows XP introduces the Fax Service Extended COM API for application developers to incorporate fax functionality. Windows Peer-to-Peer Networking The Advanced Networking Pack, later made part of SP2 introduced Peer-to-Peer Networking and the Peer Name Resolution Protocol (PNRP) to Windows XP. It operates over IPv6. The P2P architecture in Windows XP consists of the following components: PNRP: This provides dynamic name publication and resolution of names to endpoints. PNRP is a distributed name resolution protocol allowing Internet hosts to publish "peer names" and corresponding IPv6 addresses and optionally other information. Other hosts can then resolve the peer name, retrieve the corresponding addresses and other information, and establish peer-to-peer connections. With PNRP, peer names are composed of an "authority" and a "qualifier". The authority is identified by a secure hash of an associated public key, or by a place-holder (the number zero) if the peer name is "unsecured". The qualifier is a string, allowing an authority to have different peer names for different services. If a peer name is secure, the PNRP name records are signed by the publishing authority, and can be verified using its public key. Unsecured peer names can be published by anybody, without possible verification. Multiple entities can publish the same peer name. For example, if a peer name is associated with a group, any group member can publish addresses for the peer name. Peer names are published and resolved within a specified scope. The scope can be a local link, a site (e.g. a campus), or the whole Internet. Graphing: PNRP also allows creating an overlay network called a Graph. Each peer in the overlay network corresponds to a node in the graph. Nodes are resolved to addresses using PNRP. All the nodes in a graph share book-keeping information responsible for the functioning of the network as a whole. For example, in a distributed resource management network, which node has what resource needs to be shared. Such information is shared as Records, which are flooded to all the peers in a graph. Each peer stores the Record to a local database. A Record consists of a header and a body. The body contains data specific to the application that is using the API; the header contains metadata to describe the data in the body as name-value pairs serialized using XML, in addition to author and version information. It can also contain an index of the body data, for fast searching. A node can connect to other nodes directly as well, for communication that need not be shared with the entire Graph. Grouping: The Peer-to-Peer API also allows creation of a secure overlay network called a Group, consisting of all or a subset of nodes in a Graph. A Group can be shared by multiple applications, unlike a Graph. All peers in a Group must be identifiable by a unique named, registered using PNRP, and have a digital signature certificate termed as Group Member Certificate (GMC). All Records exchanged are digitally signed. Peers must be invited into a Group. The invitation contains the GMC that enables it to join the group. Simple File Sharing Windows XP introduces a more simplified form of sharing files with local users in a multi-user environment and over the network called Simple File Sharing. Simple File Sharing which is enabled by default for non-domain joined computers, disables the separate Security tab used to set advanced ACLs/permissions and enables a common interface for both - permissions on file system folders and sharing them. With Simple File Sharing enabled, the My Documents folder or its subfolders can only be read and written to by its Owner and by local Administrators. It is not shared on the network. By checking the Make this folder private option in its Properties, local Administrators are also denied permissions to the My Documents folder. For sharing files with other user accounts on the same computer when Simple File Sharing is enabled, Windows XP includes the Shared Documents folder. Simple File Sharing disables granular local and network sharing permissions. It shares the item with the Everyone group on the network with read only or write access, without asking for a password but forcing Guest user permissions. WebDAV mini-redirector In Windows XP, a "WebDAV mini-redirector" has been added which is preferred over the old Web folders client, by default. This newer client works as a system service at the network-redirector level (immediately above the file-system), allowing WebDAV shares to be assigned to a drive letter and used by any software, even through firewalls and NATs. Applications can open remote files on HTTP servers, edit the file, and save the changes back to the file (if the server allows). The redirector also allows WebDAV shares to be addressed via UNC paths (e.g. http://host/path/ is converted to \\host\path\) for compatibility with Windows filesystem APIs. The WebDAV mini-redirector is known to have some limitations in authentication support. Other networking features Internet Explorer 6 upgradeable to Internet Explorer 8 with Windows RSS Platform Outlook Express 6, Windows Address Book, NetMeeting 3.01 and MSN Explorer 6 DHCP client alternate configuration to support more than one network or in the case when a DHCP server is not available The Windows XP DNS resolver has been improved with the addition of subnet prioritization. If the DNS resolution receives multiple IP address mappings (A resource records) from a DNS server, and some of the records have IP addresses from networks to which the computer is directly connected, the resolver places those resource records first. This behavior reduces network traffic across subnets by forcing computers to connect to network resources that are closer to them. Network bridging (IEEE 802.1D Transparent Bridging) allows a Windows XP computer to act as a bridge for different network mediums, eliminating the need to configure multiple IP subnets and routers to connect multiple network mediums together Network Setup Wizard for setting up the network on non-domain joined computers, an evolution of Windows Me's Home Networking Wizard. Windows XP also improves connection wizards for setting up internet or VPN connections or remote access to a network. NAT Traversal APIs to abstract UPnP functions. UPnP IGD devices show up in Network Connections if the IGD Discovery and Control client is installed and double clicking their icon can initiate a connection to the Internet via the gateway device and show status information. NAT port mappings are also shown and can be set up. Built-in PPPoE protocol for individual authenticated access to remote servers. Connection Manager is the client dialer with the ability to connect to customized remote access connections and customized phone books of access numbers that can be created using the Connection Manager Administration Kit (CMAK). Connection Manager supports favorites to save settings for multiple network locations, client side logging and callback features and exposes more previously unavailable settings in the UI. There is support for split tunneling (although not secure) for VPN connections so VPN clients may access the internet. Windows Update uses binary delta compression so the size of Windows XP updates to download is reduced. EAP-TLS support, PEAPv0/EAP-MSCHAPv2 support beginning with Windows XP SP1. Improved support for infrared including IrDA networking (IrCOMM modems, IrNET and P2P) Network connection status support tab which displays IP configuration and offers a 1-click "Repair" function to perform a series of steps that reset the network connection. Windows XP includes network diagnostic tools such as Netsh diag, netdiag.exe in the support tools and Basic Network Diagnostics integrated into the Help and Support Center A later update, incorporated into Windows XP SP3, also introduced Network Diagnostics for Internet Explorer. There are new WinSock APIs for performance and IPv6 support. Network Location Awareness APIs are exposed through Winsock for determining network states and notifying Winsock client applications of changes. Windows XP components such as Internet Connection Sharing, Windows Firewall and Network Setup Wizard make use of these network location APIs. Winsock has the ability to self-heal if a Winsock LSP uninstallation damages it. Also, users can manually reset and repair a corrupted Winsock stack using the netsh winsock reset command. Support for PVC Encapsulation (RFC 2684) NDIS 5.1 has performance enhancements, Plug and Play and Power event notifications for miniport drivers, send cancellation and 64-bit statistic counters. Remote NDIS supports USB attached network devices. Expanded support for soft modems and HomePNA adapters. Notification when a network has limited or no connectivity. TAPI 3.1 exposes COM interfaces. H.323v2 based IP telephony and IP multicast AV conferencing Telephony Service Providers are included. TAPI 3.1 also includes File Terminals (record streaming data), Pluggable Terminals (add external terminal object), USB/HID Phone TSP (control a USB phone and use it as a streaming endpoint) and support for Auto Discovery of TAPI Servers. Several H.323 supplementary services have been implemented for richer call control features (Call Transfer, Call Hold, Call Diversion, Call Park and Pickup). Windows Messenger and RTC (Real-Time Communication) Client API to provide IM, presence, AV communications, whiteboarding, application sharing, Acoustic Echo Cancellation, media encryption, PC to phone and phone to PC services to applications. For computers in a workgroup, the Windows Time Service in Windows XP supports a new Internet Time feature (NTP client), which updates the clock on the user's computer by synchronizing with an NTP time server on the Internet. This feature is useful for computers whose real-time clock does not maintain the correct time. Microsoft Message Queuing 3.0 supports: Internet Messaging (referencing queues via HTTP, SOAP-formatted messages, MSMQ support for Internet Information Services), queue aliases, multicasting of messages, and additional support for programmatic maintenance and administration of queues and MSMQ itself. MSMQ 3 clients directly communicate with Active Directory using LDAP. Other features Internet Information Services 5.1 COM+ 1.5 Speech Application Programming Interface 5.1 SAPI 5 support in Microsoft Narrator Paint is based on GDI+ and therefore, images can be natively saved as JPEG, GIF, TIFF and PNG without requiring additional graphics filters (in addition to BMP). However, alpha channel transparency is still not supported because the GDI+ version of Paint can only handle up to 24-bit depth images. Support for acquiring images from a scanner or a digital camera was also added to Paint. WordPad has full Unicode support in Windows XP, enabling WordPad to support multiple languages. Windows XP SP1 ships with the RichEdit 4.1 control. General improvements to international support such as more locales, languages and scripts in Uniscribe, expanded MUI support, improved IMEs and National Language Support Regional and Language Options group East Asian languages, and complex script & left-to-right languages together, installable by checking a single check-box option. There is font fallback support for East Asian languages. Windows XP introduces a new "Location" variable which can be set by the user and queried using the GetGeoInfo API to provide location specific services Full Unicode support in the RichEdit control shipped in Windows XP and used by WordPad. Support for tablet and pen-sensitive screens, portrait-oriented screens in Windows XP Tablet PC Edition. It also includes speech recognition to control the operating system and for text dictation in applications using the RichEdit control or the Text Services Framework, handwriting recognition and digital ink support accessible through the Tablet PC Input Panel (TIP). Also included are applications to complement these features such as Windows Journal, Sticky Notes for note taking, a game called InkBall and several additional downloadable Tablet PC applications, extras and powertoys. Microsoft Active Accessibility 2.0 API, adding support for Dynamic Annotation and MSAA Text. The newer accessibility API, Microsoft UI Automation can also be installed on Windows XP. Windows XP supports a total of 1 million card deals in its version of FreeCell. Pinball has been updated to fix a high CPU utilization bug. Help and Support Center is very comprehensive with detailed step-by-step how-to and troubleshooting articles, glossary of terms and an index of all articles. Help and Support Center has Favorites, History and advanced search options. It includes the ability to search across multiple information sources including help sources on the Internet such as the Microsoft Knowledge Base. Users can share and install help content to and from other computers running Windows XP or Windows Server 2003 or switch to help for other supported operating system. Help and Support Center is also OEM-customizable. New set of PowerToys to significantly enhance the operating system functions such as Alt-tab switching, fast user switching, slideshow generation, desktop slideshow, ClearType optimization, shell powertoys and accessories and customizing operating system settings. Ability to change the product key using the Windows Product Activation wizard. New downloadable features Although Windows XP did not ship with the following major Windows features out-of-the-box, these new features can be added to Windows XP by downloading these components which were incorporated in later versions of Windows. .NET Framework versions 1.0, 1.1, 2.0, 3.0, 3.5 and 4.0 Windows Search 2.0, 3.0 and 4.0 Windows Defender Windows Services for UNIX XPS Essentials Pack Microsoft Virtual PC 2004 and 2007 Windows Live Essentials 2009 and Wave 2. Windows PowerShell 1.0 and 2.0 and Windows Remote Management 1.0 and 2.0. Later versions Beginning with Windows XP SP2, the audio volume taper is stored in the registry for on-screen keyboard and remote control applications and can be customized by third parties, and Internet Explorer has improved Group Policy settings support beyond security settings. (KB918997) for Windows XP SP2 and Windows XP SP3 add a Wireless LAN API for developers to create wireless client programs and manage profiles and connections. There is IEEE 802.1X support for wireless and wired connections. In case, a PKI is not available to issue certificates for a VPN connection, there is support for preshared key for IKE authentication. Service Pack 2 USB block storage devices can be made read-only so writing data is not possible. The sound events in Internet Explorer for Blocked pop-up window and the Information bar were installed. DirectX 9.0c (Shader Model 3.0) was installed. A File System Filter Manager and minifilter drivers were installed. Compared to the legacy file system filters, they are easier to develop, offer better stability and can be loaded and unloaded at any time. They reduce recursive I/O on the kernel stack and can process only necessary operations. Legacy file system filter drivers attached to the file system stack directly and didn't have the aforementioned flexibility. Windows XP Service Pack 2 (and KB811660) installed additional functionality for Offline Files. By editing the Registry, users can suppress error messages for file types that Offline Files cannot cache and which are excluded from synchronization. Offline Files for a user that are not on his primary computer (determined by matching the current user's SID with the specified SID in the registry) can be set to purge at logoff. Administratively assigned offline files can also be prevented from being cached for non-primary users. Windows Media Player 9 Series with Windows Media Format Runtime 9.0 was included and can be installed up to version 11 of the player and the format runtime. Windows Movie Maker 2, which was a free download released in 2002, was introduced. Support for DVCPRO50 and DVCPRO100 was installed. A YUV mixing mode in the VMR-7 and VMR-9 renderers which performs mixing in the YUV color space to save memory bandwidth was introduced. Powercfg.exe was installed. The significant security-related changes to MSRPC, DCOM, MSDTC and WMI were installed. Attachment Manager was installed. BITS 2.0, part of Windows XP SP2, installed support for performing concurrent foreground downloads, using Server Message Block paths for remote names, downloading portions of a file, changing the prefix or complete name of a remote name, and limiting client bandwidth usage. BITS is upgradeable to version 2.5 in Windows XP. http.sys and the HTTP Server API, the kernel-mode HTTP server for applications, backported from Windows Server 2003, was included. Bluetooth support Windows XP Service Pack 2 added native Bluetooth support. The Windows XP Bluetooth stack supports external or integrated Bluetooth dongles attached through USB. Windows XP SP2 and SP3 support Bluetooth 1.1 (but not 1.0), Bluetooth 2.0 and Bluetooth 2.0+EDR. The Bluetooth stack supports the following Bluetooth profiles natively: PAN, SPP, DUN, HID, and HCRP. Third-party stacks may replace the Windows XP stack and may support more profiles or newer versions of Bluetooth. Executable space protection Windows XP Service Pack 2 introduced Data Execution Prevention. This feature, present as NX (EVP) in AMD's AMD64 processors and as XD (EDB) in Intel's processors, can flag certain parts of memory as containing data instead of executable code, which prevents overflow errors from resulting in arbitrary code execution. It is intended to prevent an application or service from executing code from a non-executable memory region. This helps prevent certain exploits that store code via a buffer overflow, for example. DEP runs in two modes: hardware-enforced DEP for CPUs that can mark memory pages as nonexecutable, and software-enforced DEP with a limited prevention for CPUs that do not have hardware support. Software-enforced DEP does not protect from execution of code in data pages, but instead from another type of attack (SEH overwrite). Hardware-enforced DEP enables the NX bit on compatible CPUs, through the automatic use of PAE kernel in 32-bit Windows and the native support on 64-bit kernels. Software DEP, while unrelated to the NX bit, is what Microsoft calls their enforcement of "Safe Structured Exception Handling". Software DEP/SafeSEH simply checks when an exception is thrown to make sure that the exception is registered in a function table for the application, and requires the program to be built with it. If DEP is enabled for all applications, users gain additional resistance against zero-day exploits. But not all applications are DEP-compliant and some will generate DEP exceptions. Therefore, DEP is not enforced for all applications by default in 32-bit versions of Windows and is only turned on for critical system components. Windows XP Service Pack 3 introduces additional NX APIs that allow software developers to enable NX hardware protection for their code, independent of system-wide compatibility enforcement settings. Developers can mark their applications as NX-compliant when built, which allows protection to be enforced when that application is installed and runs. This enables a higher percentage of NX-protected code in the software ecosystem on 32-bit platforms, where the default system compatibility policy for NX is configured to protect only operating system components. Windows Firewall Windows XP RTM introduced the Internet Connection Firewall. It was later upgraded to Windows Firewall in Windows XP Service Pack 2 with support for filtering IPv6 traffic as well. By default, Windows Firewall performs stateful packet filtering of inbound solicited or unsolicited traffic on all types of network interfaces (LAN/WLAN, PPPoE, VPN, or dial-up connections). Like Internet Connection Sharing, the firewall has a location-aware policy, meaning it can be disabled in a corporate domain but enabled for a private home network. It has an option to disallow all exceptions which may be useful when connecting to a public network. The firewall can also be used as the edge firewall for ICS clients. When the firewall blocks a program, it displays a notification. Excepted traffic can be specified by TCP/UDP port, application filename and by scope (part of the network from which the excepted traffic originates). It supports port mapping and ICMP. Security log capabilities are included, which can record IP addresses and other data relating to connections originating from the home or office network or the Internet. It can record both dropped packets and successful connections. This can be used, for instance, to track every time a computer on the network connects to a website. Windows Firewall also supports configuration through Group Policy. Applications can use the Windows Firewall APIs to automatically add exceptions. Windows Security Center Windows Security Center, introduced in Windows XP Service Pack 2, provides users with the ability to view the status of computer security settings and services. Windows Security Center also continually monitors these security settings, and informs the user via a pop-up notification balloon if there is a problem. The Windows Security Center consists of three major components: A control panel, a Windows Service, and an application programming interface that is provided by Windows Management Instrumentation. The control panel divides the monitored security settings into categories, the headings of which are displayed with color-coded backgrounds. The current state of these settings is determined by the Windows service which starts automatically when the computer starts, and takes responsibility for continually monitoring the system for changes. The settings are made available to the system through a WMI provider. Anti-malware and firewall software vendors can register with the Security Center through the WMI provider. Windows Update settings and status are also monitored and reported. Service Pack 3 The Windows Imaging Component was installed. Management Console 3.0 was installed. MSI 3.1v2 was included. A Network Access Protection client and Group Policy support for IEEE 802.1X authentication for wired network adapters was installed. BITS 2.5, part of Windows XP SP3, installed support for IPv6 and certificate-based client authentication for secure HTTP transports and custom HTTP headers. Media Center Edition 2005 Windows XP Media Center Edition 2005 includes Microsoft Plus! Digital Media Edition components such as Audio Converter, CD Label Maker, Dancer and Party Mode and screensavers and themes from Microsoft Plus! for Windows XP. See also References Windows XP Windows XP

Operating System (OS)

Terry A. Davis Terrence Andrew Davis (December 15, 1969 – August 11, 2018) was an American programmer who is most known for creating and designing the TempleOS operating system. Its development was an extremely complex, time-consuming and unusual undertaking for one person. During his final years, he amassed an online following and regularly posted video blogs to social media. As a teenager, Davis learned assembly language on a Commodore 64. He later earned a master's degree in electrical engineering from Arizona State University and worked for several years at Ticketmaster as a programmer for VAX machines. In 1996, he began experiencing regular manic episodes, one of which led him to hospitalization. Initially diagnosed with bipolar disorder, he was later declared to have schizophrenia. He collected disability payments and resided in Las Vegas with his parents until the year before his death. Davis grew up as a Catholic and was an atheist for some of his adult life. After experiencing a self-described "revelation", he proclaimed that he was in direct communication with God and that God commanded him to build a successor to the Second Temple. He committed a decade of his life to creating an operating system modeled after the DOS-based interfaces of his youth, first calling it the "J Operating System" and later "LoseThos". In 2013, Davis announced that he had completed the project, which was now called "TempleOS". The operating system itself was generally regarded as a hobby system, not suitable for general use, but Davis received sympathy and support for bringing the project to fruition. Although Davis remained lucid when discussing computer-related subjects, his communication skills were significantly affected by his schizophrenia. He was controversial for his regular use of racist language, which he explained was his way of combating actors of psychological warfare. During his final months, he struggled with periods of homelessness and incarceration. In 2018, he was struck by a train and died at the age of 48. Investigators could not determine whether his death was suicide or accidental. Early life and career Terrence Andrew Davis was born in West Allis, Wisconsin, later moving to Washington, Michigan, California and Arizona. He was the seventh of eight children, and his father was an industrial engineer. As a child, Davis used an Apple II at his elementary school, and as a teenager, learned assembly language on a Commodore 64. He earned a master's degree in electrical engineering from Arizona State University in 1994 and worked for several years at Ticketmaster as a programmer for VAX machines. On the subject of his certifications, he wrote in 2011: "Everybody knows electrical is higher in the engineering pecking order than CS because it requires real math ;-) I'm a rocket scientist, though, not a very good one". Onset of illness and spiritual awakening Davis grew up Catholic, but was an atheist for some of his adult life before experiencing what he called a "revelation from God". Starting in 1996, Davis was admitted to a psychiatric ward approximately every six months due to reoccurring manic episodes. In March, he had begun experiencing regular manic episodes and developed delusions centering around space aliens and government agents. According to Davis, he attributed a profound quality to the Rage Against the Machine lyric "some of those that work forces are the same that burn crosses" and recalled "I started seeing people following me around in suits and stuff. It just seemed something was strange." He started donating large sums of money to charity organizations, something he had never done before. Later, he surmised, "that act [probably] caused God to reveal Himself to me and saved me." Soon afterward, out of fear of the suited figures he believed to be following him, Davis left town and drove hundreds of miles south with no destination. After becoming convinced that his car radio was communicating with him, he dismantled his vehicle (apparently in a search for tracking devices he believed were hidden on it) and threw his keys into the desert. He walked aimlessly along the side of the highway, where he was then picked up by an officer. Davis escaped from the patrol vehicle, broke his collarbone, and was then taken to a hospital. Distressed about a conversation over artifacts found on his X-ray scans, interpreted by him as "alien artifacts", he ran from the hospital and attempted to carjack a nearby truck before being arrested. In jail, he stripped himself, broke his glasses and jammed the frames into a nearby electrical outlet, trying to open his cell door by switching the breaker. This failed, as he had been wearing non-conductive frames. He was then admitted to a mental hospital for two weeks. Regarding these developments, Davis said in a 2014 interview that he had been "genuinely pretty crazy in a way. Now I'm not. I'm crazy in a different way maybe." Davis acknowledged that the sequence of events leading to his spiritual awakening might give the impression of "mental illness, as opposed to some glorious revelation from God. ... It would sound polite if you said I scared myself thinking about quantum computers. And then I guess you just throw in your ordinary mental illness." Reflecting on the initial episode, he said, "I'm not especially proud of the logic and thinking. It looks very young and childish and pathetic. ... In the Bible it says if you seek God, He will be found of you. I was really seeking, and I was looking everywhere to see what he might be saying to me." Davis was initially diagnosed with bipolar disorder and later declared to have schizophrenia. Afterward, he felt "guilty for being such a technology-advocate atheist" and sought to emulate Jesus by giving away all his possessions and living a nomadic lifestyle. In July 1996, he returned to Arizona and started formulating plans for a new business. He designed a three-axis milling machine, as he recalled having 3D printing in mind as an obvious pursuit. An incident involving a Dremel tool nearly set his apartment on fire, which caused him to abandon the idea. He subsequently lived with his parents in Las Vegas and collected Social Security disability payments. After 2003, Davis' hospitalizations became less frequent. His schizophrenia still affected his communication skills, and his online comments were usually incomprehensible. However, he was reported as "always lucid" if the topic was about computers. Vice noted that, in 2012, he had a productive conversation with the contributors at MetaFilter, where his work was introduced as "an operating system written by a schizophrenic programmer". TempleOS TempleOS (known as "J Operating System" from 2004 to 2005, "LoseThos" from 2006 to early 2012, and "SparrowOS" in late 2012) is an operating system similar to the Commodore 64, DESQview and other early DOS-based interfaces. It was conceived by Davis in the early 2000s and developed alone over the course of a decade. This included the design of its original programming language, editor, compiler and kernel. It was ultimately composed of over 100,000 lines of code. In 2005, Davis stated that his ambition for the J Operating System was "to recreate the dynamic environment that used to exist when the Commodore 64 was around and everyone was creating odd-ball software". He envisioned the system as a Commodore 64 with a "thousand times" more powerful processing speed. Three years later, he wrote that the primary purpose of LoseThos was "for making video games. It has no networking or Internet support. As far as I'm concerned, that would be reinventing the wheel". Davis later proclaimed that he was in direct communication with God, and that God told him to build a successor to the Second Temple as an operating system. As such, references to Biblical tropes are ubiquitous in the OS. One bundled program, "After Egypt", is a game in which the player travels to a burning bush to use a "high-speed stopwatch". The stopwatch is meant to act as an oracle that generates pseudo-random text, something Davis believed to be coded messages from God. He likened the process to a Ouija board and speaking in tongues. An example of generated text follows: According to Davis, many of the system's features, such as its 640x480 resolution and 16-color display, were also explicit instructions from God. The charter on his website stated that TempleOS was "God's official temple. Just like Solomon's Temple, this is a community focal point where offerings are made and God's oracle is consulted". He used the oracle to ask God about war ("servicemen competing"), death ("awful"), dinosaurs ("Brontosaurs' feet hurt when stepped"), favorite video game (Donkey Kong), favorite car (BMW), favorite national anthem (Latvia's), favorite band (the Beatles), and the 11th commandment ("Thou shall not litter"). In 2012, Davis stated that LoseThos was downloaded 10,000 times since 2009, and that there was "no evidence anyone has installed it. I am in a CIA prison." Later in the year, he renamed LoseThos to "SparrowOS", and in early 2013, rebranded again as "TempleOS". A few weeks later, his website announced: "God's temple is finished. Now, God kills CIA until it spreads". Recognition, controversy and following Davis was controversial for his regular use of racist and homophobic slurs, sometimes rebuking his critics as "CIA niggers". Online, he would frequently communicate in randomly generated blocks of text and off-topic declarations about God, which led to bans from websites including Something Awful, Reddit, and Hacker News. However, the critical reception to TempleOS was mostly favorable, as tech journalist David Cassel wrote, "programming websites tried to find the necessary patience and understanding to accommodate Davis". TechRepublic and OSNews published positive articles on Davis' work, even though he was banned from OSNews for hostile comments targeting its readers and staff. Such outbursts, along with the system's "amateurish" presentation, ultimately caused TempleOS to become a frequent object of derision. Davis explained that his use of the word "nigger" was a reaction to being subject to psychological warfare tactics from media agencies such as the BBC. He addressed concerns about his language on his website: Once TempleOS was completed, most of his time was spent online, "coding, web surfing, or using the output from the National Institute of Standards and Technology randomness beacon to talk to God". He posted hours of video blogs and would refer to himself as "the smartest programmer that's ever lived" while showing his creations. A small fan following proceeded to form around Davis online. In 2017, the OS was shown as a part of an outsider art exhibition in Bourogne, France. Davis said he was happy to receive the attention but was disappointed that few of his fans actually used the OS to speak to God. His YouTube channels were repeatedly banned due to his vulgarities. In September 2018, OSNews editor Thom Holwerda wrote: "Davis was clearly a gifted programmer – writing an entire operating system is no small feat – and it was sad to see him affected by his mental illness". One fan described him as a "programming legend", while another, a computer engineer, compared the development of TempleOS to a one-man-built skyscraper. The engineer had previously spoken to Davis at length and believed that Davis could have been a "Steve Jobs" or a "Steve Wozniak" were it not for his illness. He added that it "actually boggles my mind that one man wrote all that" and surmised that it may be difficult for a layperson to understand how extraordinary it was to write an entire operating system alone. Death During his final months, Davis struggled with periods of homelessness and incarceration. He stopped taking medication because he believed that it limited his creativity. Some fans helped him by bringing him supplies, but he refused their housing offers. After living with his sister in Arizona, Davis traveled to California, and in April 2018, stopped in Portland, Oregon. Local police were informed that Davis may be a threat, since he had stated a willingness to kill if asked by God. In June, Portland police informed officials in the nearby town of The Dalles that they had received word that Davis may be headed there. No further complaints were received about Davis. In his final video, recorded on a bench at the Dalles Wasco County Library and uploaded hours before his death, he explained that he had removed most of his videos because he did not wish to "litter" the Internet, and that he had learned how to "purify" himself. At the very end, he states: "It's good to be king. Wait, maybe. I think maybe I'm just like a little bizarre little person who walks back and forth. Whatever, you know, but..." On the evening of August 11, 2018, while walking alongside railroad tracks in The Dalles, Oregon, Davis was struck and killed by a Union Pacific train. Investigators could not determine whether his death was suicide or accidental, although the train engineer believed his death to be a suicide. The police report stated that Davis was walking with his back toward the train and that he turned around before the moment of impact. When The Dalles Chronicle ran a story about an unnamed homeless man who was struck by a train, the newspaper was inundated with phone calls inquiring whether it was Davis, which the paper later confirmed in a follow-up piece. As reports of his death surfaced online, he was memorialized by fans in a number of tributes posted to social media. Through the TempleOS website, his family asked people to donate to "organizations working to ease the pain and suffering caused by mental illness". In December 2018, Linux.org (an unofficial community for Linux users) was vandalized by hackers to include a reference to his death. In November 2019, Davis was the subject of a 30-minute documentary on BBC Radio 4. See also Creativity and mental illness Religion and schizophrenia References Notes Citations External links TempleOS Website Archive of the TempleOS website and operating system 1969 births 2018 deaths Former atheists and agnostics Converts to Christianity from atheism or agnosticism American computer programmers Arizona State University alumni Railway accident deaths in the United States People with schizophrenia Outsider artists American male bloggers American bloggers Video bloggers People from West Allis, Wisconsin

Operating System (OS)

386BSD 386BSD (also known as "Jolix") is a discontinued Unix-like operating system based on the Berkeley Software Distribution (BSD). It was released in 1992 and ran on PC-compatible computer systems based on the 32-bit Intel 80386 microprocessor. 386BSD innovations included role-based security, ring buffers, self-ordered configuration and modular kernel design. History 386BSD was written mainly by Berkeley alumni Lynne Jolitz and William Jolitz. William Jolitz had considerable experience with prior BSD releases while at the University of California at Berkeley (2.8 and 2.9BSD) and both contributed code developed at Symmetric Computer Systems during the 1980s, to Berkeley. Work on porting 4.3BSD-Reno and later 4.3BSD Net/2 to the Intel 80386 was done for the University of California by William Jolitz at Berkeley. 4.3BSD Net/2 was an incomplete non-operational release, with portions withheld by the University of California as encumbered (i.e. subject to an AT&T UNIX source code license). The 386BSD releases made to the public beginning in 1992 were based on portions of the 4.3BSD Net/2 release coupled with additional code (see "Missing Pieces I and II", Dr. Dobb's Journal, May–June 1992) written by William and Lynne Jolitz to make a complete operational release. The port began in 1989 and the first, incomplete traces of the port can be found in 4.3BSD Net/2 of 1991. The port was made possible as Keith Bostic, partly influenced by Richard Stallman, had started to remove proprietary AT&T out of BSD in 1988. The port was first released in March 1992 (version 0.0) and in a much more usable version on July 14, 1992 (version 0.1). The porting process with code was extensively documented in an 18-part series written by Lynne Jolitz and William Jolitz in Dr. Dobb's Journal beginning in January 1991. FreeBSD and NetBSD After the release of 386BSD 0.1, a group of users began collecting bug fixes and enhancements, releasing them as an unofficial patchkit. Due to differences of opinion between the Jolitzes and the patchkit maintainers over the future direction and release schedule of 386BSD, the maintainers of the patchkit founded the FreeBSD project in 1993 to continue their work. Around the same time, the NetBSD project was founded by a different group of 386BSD users, with the aim of unifying 386BSD with other strands of BSD development into one multi-platform system. Both projects continue to this day. Lawsuit Due to a lawsuit (UNIX System Laboratories, Inc. v. Berkeley Software Design, Inc.), some potentially so-called encumbered source was agreed to have been distributed within the Berkeley Software Distribution Net/2 from the University of California, and a subsequent release (1993, 4.4BSD-Lite) was made by the university to correct this issue. However, 386BSD, Dr. Dobb's Journal, and William Jolitz and Lynne Jolitz were never parties to these or subsequent lawsuits or settlements arising from this dispute with the University of California, and continued to publish and work on the 386BSD code base before, during, and after these lawsuits without limitation. There has never been any legal filings or claims from the university, USL, or other responsible parties with respect to 386BSD. Finally, no code developed for 386BSD done by William Jolitz and Lynne Jolitz was at issue in any of these lawsuits. Release 1.0 In late 1994, a finished version 386BSD Release 1.0 was distributed by Dr. Dobb's Journal on CDROM only due to the immense size (600 MB) of the release (the "386BSD Reference CD-ROM") and was a best-selling CDROM for three years (1994–1997). 386BSD Release 1.0 contained a completely new kernel design and implementation, and began the process to incorporate recommendations made by earlier Berkeley designers that had never been attempted in BSD. Release 2.0 On August 5, 2016, an update was pushed to the 386BSD GitHub repository by developer Ben Jolitz, named version 2.0. According to the official website, Release 2.0 "built upon the modular framework to create self-healing components." However, , almost all of the documentation remains the same as version 1.0, and a changelog was not available. Relationship with BSD/386 386BSD is often confused with BSD/386 which was a different project developed by BSDi, a Berkeley spinout, starting in 1991. BSD/386 used the same 386BSD code contributed to the University of California on 4.3BSD NET/2. Although Jolitz worked briefly for UUNET (which later spun out BSDi) in 1991, the work he did for them diverged from that contributed to the University of California and did not appear in 386BSD. Instead, William Jolitz gave regular code updates to Donn Seeley of BSDi for packaging and testing, and returned all materials when William Jolitz left that company following fundamental disagreements on company direction and goals. Copyright and use of the code All rights with respect to 386BSD and JOLIX are now held exclusively by William Jolitz and Lynne Jolitz. 386BSD public releases ended in 1997 since code is now available from the many 386BSD-derived operating systems today, along with several derivatives thereof (such as FreeBSD, NetBSD and OpenBSD). Portions of 386BSD may be found in other open systems such as OpenSolaris. Further reading Jolitz, William F. and Jolitz, Lynne Greer: Porting UNIX to the 386: A Practical Approach, 17-part series in Dr. Dobb's Journal, January 1991 – July 1992: Jan/1991: DDJ "Designing a Software Specification" Feb/1991: DDJ "Three Initial PC Utilities" Mar/1991: DDJ "The Standalone System" Apr/1991: DDJ "Language Tools Cross-Support" May/1991: DDJ "The Initial Root Filesystem" Jun/1991: DDJ "Research and the Commercial Sector: Where Does BSD Fit In?" Jul/1991: DDJ "A Stripped-Down Kernel" Aug/1991: DDJ "The Basic Kernel" Sep/1991: DDJ "Multiprogramming and Multiprocessing, Part I" Oct/1991: DDJ "Multiprogramming and Multiprocessing, Part II" Nov/1991: DDJ "Device Autoconfiguration" Feb/1992: DDJ "UNIX Device Drivers, Part I" Mar/1992: DDJ "UNIX Device Drivers, Part II" Apr/1992: DDJ "UNIX Device Drivers, Part III" May/1992: DDJ "Missing Pieces, Part I" Jun/1992: DDJ "Missing Pieces, Part II" Jul/1992: DDJ "The Final Step: Running Light with 386BSD" Jolitz, William F. and Jolitz, Lynne Greer: Operating System Source Code Secrets Vol 1 The Basic Kernel, 1996, Jolitz, William F. and Jolitz, Lynne Greer: Operating System Source Code Secrets Vol 2 Virtual Memory, 2000, References External links William Jolitz's 386bsd Notebook Jolix.com Porting UNIX to the 386: A Practical Approach Memories of 386BSD releases by Lynne Jolitz The unknown hackers - Salon.com 386BSD Design Notes Professional Video Series Frequently asked questions of 386BSD - active Q/A by authors Raising Top Quality Rabble; article mentioning 386BSD Archived comment on "Raising Top Quality Rabble" with remarks on the history of 386BSD by Lynne Jolitz Remarks on the history of 386BSD by Greg Lehey More information on the various releases of 386BSD Browsable 386BSD kernel sources Berkeley Software Distribution Discontinued operating systems Free software operating systems 1992 software

Operating System (OS)

International Systems and Storage Conference The International Systems and Storage Conference (SYSTOR) is an ACM research conference sponsored by the ACM SIGOPS Special Interest Group on Operating Systems. SYSTOR covers all aspects of Computer Systems technology. The first SYSTOR was held in October 2007 (as a workshop). Since 2009, it is held annually in Haifa, Israel, usually in May or June. Since 2012, SYSTOR is held in cooperation with USENIX. Since 2014, SYSTOR is sponsored by ACM. The technical program of SYSTOR typically consists of about 15–20 peer-reviewed papers. As of June 2013, according to Arnetminer, SYSTOR papers published in the years 2009–2012 have been cited a total of 589 times. The SYSTOR conference focuses on experimental and practical computer systems research, which encompasses such topics as: file and storage technology; operating systems; distributed, parallel, and cloud systems; security; virtualization; fault tolerance, reliability, and availability. References External links SYSTOR Conference Website (systor.org) Computer science conferences

Operating System (OS)

Comparison of X Window System desktop environments A desktop environment is a collection of software designed to give functionality and a certain look and feel to an operating system. This article applies to operating systems which are capable of running the X Window System, mostly Unix and Unix-like operating systems such as Linux, Minix, illumos, Solaris, AIX, FreeBSD and Mac OS X. Microsoft Windows is incapable of natively running X applications; however, third-party X servers like Cygwin/X, Exceed, or Xming are available. Technical elements of a desktop environment A desktop environment (DE) can be broken up into several components that function independently and interact with one another to provide the look and feel and functionality of the desktop environment. A fundamental part of a DE is the window manager or WM. A window manager creates a certain way for application windows to present themselves to the user. It manages the various application windows, keeping track of which ones are open and providing features to switch between them. Another important element of a DE is the file manager. This application manages files/ folders and presents them in a way that the user finds convenient. It provides file operations like viewing, copying or moving, changing permissions and deleting. DEs usually provide utilities to set wallpapers and screensavers, display icons on the desktop, and perform some administrative tasks. They may optionally include word processors, CD/DVD writing applications, web browsers and e-mail clients. There are some exceptions: Window managers like Fluxbox, wmii and Ratpoison operate independently of a desktop environment and were written with this objective in mind. Additional hand-picked applications add functionality such as a panel and volume management which gives them some of the qualities of a full DE. This contrasts the behaviour of WMs like Metacity and KWin which were not written with the objective of operating independently of a DE. KDE Software Compilation and GNOME are written almost completely on special software libraries Qt and GTK respectively. This usually means that virtually every component of the desktop environment including the file manager explicitly depends on that library for its functioning. Notably, nothing prevents the user from installing any number of software libraries of their choice. In practice, software written on major libraries can be run under any desktop environment. Running a package designed for one desktop (which essentially means that it's written using the same libraries as the desktop itself is) within a different desktop can be visually displeasing, as well as incurring the RAM penalty of loading libraries that wouldn't otherwise be required. Some of the differences which can influence the choice of desktop environment are: Look and feel of the desktop environment. The user will be more comfortable with a certain look and feel that they may or may not already be familiar with. Flexibility and configurability of the desktop environment. A sophisticated user might want a highly configurable desktop environment to make the desktop environment work the way they want. A beginning user might just want an easy-to-use environment to which they will adjust. Personal preferences for choice of software, which has two aspects: Each desktop environment comes packaged with various default software and various "ways things are done" under that desktop. A casual user might like a highly integrated graphical interface to change various settings while a more experienced user might prefer to use individual configuration utilities or even CLI tools. Desktops are also often closely tied into various major functional components of the desktop manager (example: file manager, browser, word processor); whilst "mix and match" is possible, it is generally pleasing to make choices which result in a consistent look and feel of programs under the chosen desktop environment. Making choices based on what software integrates with a chosen desktop environment necessarily limits the weight that can be given to other application features. Desktop comparison information Overview Default programs packaged This table shows basic information on the programs distributed with some desktop environments for the X Window System. Note that Razor-qt has become LXQt, a port of LXDE to the Qt framework. Comparison of ease of use and stability GNOME's graphical file manager Files (Nautilus) is intended to be very easy to use and has many features. KDE's file manager Dolphin is described as focused on usability. Prior to KDE version 4, the KDE project's standard file manager was Konqueror, which was also designed for ease of use. Both GNOME and KDE come with many graphical configuration tools, reducing the need to manually edit configuration files for new users. They have extensive bundled software such as graphical menu editors, text editors, audio players, and software for doing administrative work. All applications installed in most distributions are automatically added to the GNOME and KDE menus. No major configuration changes are necessary to begin working. However, by using graphical tools, the extent to which the desktops can be configured is determined by the power provided by those tools. Compatibility and interoperability issues Some desktop environments and window managers claim that they support applications made for other desktop environments explicitly. For example, Fluxbox states KDE support in its feature list. Using software made specifically for the desktop environment in use or window manager agnostic software is a way to avoid issues. For software developers, the Portland Project has released a set of common interfaces that allows applications to integrate across many desktop environments. System resources utilization A 2011 test by Phoronix with the default installation of Ubuntu 10.04 showed that LXDE 0.5's memory utilization was lower than that of Xfce 4.6, which in turn was lower than that of GNOME 2.29, with KDE 4.4 using the most RAM compared to the aforementioned desktops. In 2015, it was demonstrated in benchmarks that LXDE performed slightly faster than Xfce overall (in the average of all tests), using the Fedora Linux operating system. See also Comparison of X window managers Comparison of file managers Croquet Project DistroWatch – a website containing information on several hundred distributions freedesktop.org Minimalism (computing) Software bloat References External links Best Linux desktop of 2018 TechRadar Fedora 24: Comparing Gnome, KDE Plasma, Cinnamon, MATE, Xfce, LXDE ZDNet Freedom of choice: 7 top Linux desktop environments compared PC World 11 Best Linux Desktop Environments And Their Comparison | 2018 Edition fossbytes.com The 10 Best Linux Desktop Environments lifewire.com 7 Best Desktop Environments For Linux itsfoss.com What is the difference between Gnome, KDE, Xfce & LXDE pclosmag.com Should You Use a Window Manager as Your Desktop Environment? makeuseof.com Six Popular Linux Desktop Environments techspot.com 10 Best and Most Popular Linux Desktop Environments of All Time tecmint.com 5 Best Linux Desktop Environments With Pros & Cons linuxandubuntu.com The 8 Best Ubuntu Desktop Environments (18.04 Bionic Beaver Linux) linuxconfig.org Best New Linux Desktop Environments Datamation 6 reasons why GNOME is still the best Linux desktop environment opensource.com Best Linux Desktop Environments for 2016 linux.com WTF Desktop Environments: GNOME, KDE, and More Explained Lifehacker A visual history of OS desktop environments NetworkWorld X Window System desktop environments

Operating System (OS)

Version 6 Unix Sixth Edition Unix, also called Version 6 Unix or just V6, was the first version of the Unix operating system to see wide release outside Bell Labs. It was released in May 1975 and, like its direct predecessor, targeted the DEC PDP-11 family of minicomputers. It was superseded by Version 7 Unix in 1978/1979, although V6 systems remained in regular operation until at least 1985. AT&T Corporation licensed Version 5 Unix to educational institutions only, but licensed Version 6 also to commercial users for $20,000, and it remained the most widely used version into the 1980s. An enhanced V6 was the basis of the first ever commercially sold Unix version, INTERACTIVE's IS/1. Bell's own PWB/UNIX 1.0 was also based on V6, where earlier (unreleased) versions were based on V4 and V5. Whitesmiths produced and marketed a (binary-compatible) V6 clone under the name Idris. Source code V6 Unix was released as a distribution including the full source code. Since source code was available and the license was not explicit enough to forbid it, V6 was taken up as a teaching tool, notably by the University of California, Berkeley, Johns Hopkins University and the University of New South Wales (UNSW). UC Berkeley distributed a set of add-on programs called the First Berkeley Software Distribution or 1BSD, which later became a complete operating system distribution. UNSW professor John Lions' famous Commentary on UNIX 6th Edition was an edited selection of the main parts of the kernel as implemented for a Digital PDP-11/40, and was the main source of kernel documentation for many early Unix developers. Due to license restrictions on later Unix versions, the book was mainly distributed by samizdat photo-copying. The source code for the original V6 Unix was later made available as free software under a BSD License from the SCO Group. Portability Interdata 7/32 In 1977, Richard Miller and Ross Nealon, working under the supervision of professor Juris Reinfelds at Wollongong University, completed a port of V6 Unix to the Interdata 7/32, thus proving the portability of Unix and its new systems programming language C in practice. Their "Wollongong Interdata UNIX, Level 6" also included utilities developed at Wollongong, and later releases had features of V7, notably its C compiler. Wollongong Unix was the first ever port to a platform other than the PDP series of computers, proving that portable operating systems were indeed feasible, and that C was the language in which to write them. In 1980, this version was licensed to The Wollongong Group in Palo Alto that published it as Edition 7. Interdata 8/32 Around the same time, a Bell Labs port to the Interdata 8/32 was completed, but not externally released. The goal of this port was to improve the portability of Unix more generally, as well to produce a portable version of the C compiler. The resulting Portable C Compiler (PCC) was distributed with V7 and many later versions of Unix, and was used to produce the UNIX/32V port to the VAX. IBM VM/370 A third Unix portability project was completed at Princeton, NJ in 1976–1977, where the Unix kernel was adapted to run as a guest operating on IBM's VM/370 virtualization environment. This version became the nucleus of Amdahl's first internal UNIX offering. (see Amdahl UTS) Variants and extensions Bell Labs developed several variants of V6, including the stripped-down MINI-UNIX for low-end PDP-11 models, LSI-UNIX or LSX for the LSI-11, and the real-time operating system UNIX/RT, which merged V6 Unix and the earlier MERT hypervisor. After AT&T decided the distribution by Bell Labs of a number of pre-V7 bug fixes would constitute support (disallowed by an antitrust settlement) a tape with the patchset was slipped to Lou Katz of USENIX, who distributed them. The University of Sydney released the Australian Unix Share Accounting Method (AUSAM) in November 1979, a V6 variant with improved security and process accounting. In the Eastern Bloc, clones of V6 Unix appeared for local-built PDP-11 clones (MNOS, later augmented for partial compatibility with BSD Unix) and for the Elektronika BK personal computer (BKUNIX, based on LSX). V6 was used for teaching at MIT in 2002 through 2006, and subsequently replaced by a simpler clone called xv6. See also Ancient UNIX References External links V6 source code Wollongong Interdata UNIX source code Unix V6 Manuals – Web interface to the V6 manual pages. Unix V6 documents, e.g. C Reference, and man pages The First Unix Port; Richard Miller's account of porting Unix to the Interdata 7/32 Unix v6 for PDP-11 online emulator Bell Labs Unices Discontinued operating systems Unix history Unix variants Free software operating systems 1975 software

Operating System (OS)

JX (operating system) JX is a microkernel operating system with both the kernel and applications implemented using the Java programming language. Overview JX is implemented as an extended Java virtual machine (the JX Core), adding support to the Java system for necessary features such as protection domains and hardware access, along with a number of components written in Java that provide kernel facilities to applications running on the computer. Because Java is a type-safe language, JX is able to provide isolation between running applications without needing to use hardware memory protection. This technique, known as language-based protection means that system calls and inter-process communication in JX does not cause an address space switch, an operation which is slow on most computers. JX runs on standard PCs, with support for a limited range of common hardware elements. It is Free software, developed by the University of Erlangen. The primary benefits of JX include: base on a small trusted computing base (TCB) security system lack of address space switching compare to most other microkernel systems it is a highly flexible operating system with different configuration possibilities See also JavaOS References External links Project home page The JX Operating System The Structure of a Type-Safe Operating System A Java Operating System as the Foundation of a Secure Network Operating System Operating system kernels Microkernels Free software operating systems Microkernel-based operating systems Discontinued Java virtual machines

Operating System (OS)

Amiga software Amiga software is computer software engineered to run on the Amiga personal computer. Amiga software covers many applications, including productivity, digital art, games, commercial, freeware and hobbyist products. The market was active in the late 1980s and early 1990s but then dwindled. Most Amiga products were originally created directly for the Amiga computer (most taking advantage of the platform's unique attributes and capabilities), and were not ported from other platforms. During its lifetime, thousands of applications were produced with over 10,000 utilities (collected into the Aminet repository). However, it was perceived as a games machine from outside its community of experienced and professional users. More than 12,000 games were available. New applications for the three existing Amiga-like operating systems are generally ported from the open source (mainly from Linux) software base. Many Amiga software products or noteworthy programs during the timeline were ported to other platforms or inspired new programs, such as those aimed at 3D rendering or audio creations, e.g. LightWave 3D, Cinema 4D, and Blender (whose development started for the Amiga platform only). The first multimedia word processors for Amiga, such as TextCraft, Scribble!, Rashumon, and Wordworth, were the first on the market to implement full color WYSIWYG (with other platforms then only implementing black-and-white previews) and allowing the embedding of audio files. History and characteristics From the origins to 1988 1985 Amiga software started its history with the 1985 Amiga 1000. Commodore International released the programming specifications and development computers to various software houses, prominently Electronic Arts, a software house that then offered Deluxe Paint, Deluxe Music and others. Electronic Arts also developed the Interchange File Format (IFF) file container, to store project files realized by Deluxe Paint and Deluxe Music. IFF became the de facto standard in AmigaOS. The first to be shown were digitizer software ProPaint (in early beta). Both were used by Andy Warhol to produce a black-and-white photo of Debbie Harry at the Launch Gala at Lincoln Center, New York City in July 1985. In 1985 Commodore licensed the software called Transformer from Simile Research and put it on the market in January 1986, bundled with an external A1020 5.25-inch floppy drive. It emulated 8086 Intel-based PC-XT hardware. It could run MS-DOS and MS-DOS software such as Lotus 123 or WordStar. This provided early access to many applications, while waiting for native Amiga software to be developed. In 1985, Deluxe Paint emerged with graphic features that had been available only on dedicated graphic computers. It was dubbed the first Amiga "Killer application". 1986 In 1986 (the year of the launch of Amiga 2000) Amiga software products contributed to the Amiga's success as a game and multimedia machine. AmigaBasic from Microsoft, VizaWrite, TextCraft (word processors), Pagesetter (Desktop Publishing), Analyze! (Spreadsheet), Superbase Personal (Database), MovieCraft (animation), Deluxe paint II, Deluxe Music, Instant Music (a composition music program for non musicians) from Electronic Arts, and GraphiCraft again from Commodore were released. GraphiCraft was used by computer artist Jim Sachs to produce Amiga software such as Defender of the Crown and Centurion: Defender of Rome from Cinemaware and the Amiga porting of Saucer Attack. Graphicraft was a predecessor of Aegis Images and AEGIS Animator, one of the first programs worldwide capable of creating animation videos and cartoons complete with audio stereo, featuring a cel animation working paradigm interface and outputting files based on delta-frame difference compression method which then were the lead for creating the ANIM file type standard. Byte-by-Byte Software Inc. released Sculpt-3D. It was the first rendering tool available for the first time to a vast audience of public, and in October of the same year, Impulse released TurboSilver. 1987 In 1987 the Amiga 500 (A500) was released. The Amiga software market moved in favor of entertainment over professional software. ProWrite (word processor), Maxiplan 500 (spreadsheet), and Aegis Sonix, a music program similar to Instant Music, were produced. . In July, Wordperfect created an "Amiga/Atari Division" and started selling a version of its word processor for the Commodore platform for US$400. It could load and save Wordperfect files created on any platform, such as IBM, Macintosh and Apple II. Wordperfect 4.1 for the Amiga was the first word processor in the world capable of opening an unlimited number of documents (limited by RAM), each in a separate window. In 1987, Andrew Tanenbaum released Minix, a free version of Unix with complete source code. At COMDEX NewTek showed for the first time a prototype of Video Toaster and Impulse released TurboSilver 2.0. 1988 In 1988, Photon Paint was released. It allowed digital painting using HAM graphics mode and the full 4096-color palette of Amiga on a single screen. Maxiplan 500 become Maxiplan 1.x, Electronic Arts showed DeLuxe Photo Lab (photo editing software), Newtek demonstrated DigiView 3.0 hardware and software image digitizing suite, and WordPerfect released the WordPerfect Library for the Amiga. At the summer Consumer Electronics Show (CES), the Pro Draw graphic tablet with mouse emulation software was also announced, as well as Flash-Back and Quarterback hard drive backup software. Superbase Personal became Superbase Professional, Micro Illusions started shipping Music-X audio software for the Amiga, and Lattice released its C++ preprocessor for the Amiga. Cygnus Editor ubiquitous text editor, one of the most versatile text editors and best seller on Amiga since then, was also released this year. It was one of the first Amiga programs featuring an AREXX port. Gold Disk released ComicSetter (comic creation) and MovieSetter (32-color cartoons with stereo sound animation software). In November, at the World of Commodore Show, ReadySoft demonstrated its Amax Macintosh emulator for the Amiga. 1989–1994 In 1989, Rashumon was first launched. In 1990, AmigaDOS 2.0 was released. The interface of the Workbench GUI was changed to a fake 3D aspect using gray shades. For the first time, Commodore introduced a style guide for developers on AmigaOS; because of this, the majority of Amiga software developed for AmigaDOS 2.0 had a standardized GUI that improved usability. Programs such as Imagine 3D, Lightwave, ImageFX, and Scala continued using non-standard GUIs. AmigaVision was released and bundled free with any model of Amiga 3000. Directory Master, Directory Opus, TurboCalc, Photogenics, ImageFX, PC Task, Photogenics, Caligari, Final Calc, and Cinema 4D all belong to this period. 1994 to today After 1994, Commodore's demise left Amiga to an uncertain future. Windows-based PCs became the standard in the home and the office. Many software houses either left the Amiga market or ran into financial troubles. In 1996, Aminet was created. Aminet was the first centralized Internet repository of all Amiga public domain software and documents. It was the first Internet experiment of a centralized software repository created and maintained by one community for the community itself. Amiga's browsers like AWeb, IBrowse and Voyager were enhanced. Voyager was the first browser to adopt tabbed browsing. Mailers like YAM are still used. In productivity software, programs like Candy Factory for image processing were still being developed, for VFX and animation programs like Wildfire by Andreas Maschke (ported by the author to Java later). other prominent graphic software include fxPAINT by IOSpirit, fxSCAN for OCR and scanning by IOSpirit, and SketchBlock painting program by Andy Broad for AmigaOS 4.x. Last but not least Tornado3D raytracing program by the Italian company Eyelight. Usability Amiga software presents a complete graphical interface, following Amiga WYSIWYG "desktop paradigm" and native AmigaOS interface guidelines; that is to say, the software is mouse-driven and presents also pull-down "menus" and "dialogue windows". AmigaOS maintained a text-based shell allowing software to present a text-based GUI, or a "command line". Cataloging The main software categories are Productivity software (also called application software); Support and maintenance utilities for formatting hard disks, recover or backup data, etc.; Multimedia software (graphic, video, music); Communication software (including the software for dealing with Internet and any other net); Programming tools for developing products and applications; other utilities that enhance the ease of use in any Operating System (for example Application Launching Docks); Accessibility; Games; Emulation software that allows a computer to run software written for another architecture. Productivity software Amiga created productivity software which covers graphics, video, design and CAD software; graphic utilities; vector graphics programs and converters; word processors; programmable text editors; database and spreadsheets; science, entertainment and special use programs: entertainment; fractals, virtual reality, artificial intelligence; route planning; personal Organizer, notebook, diary software; personal budgeting, home banking and accounting. Support and maintenance utilities Amiga created utilities for hard disk partitioning; diagnostic tools; VGA promoting tools for ancient Amiga software with TV resolution graphic screens; game loaders for storing and auto-loading from hard disks, auto-starting non-standard floppy disks; disk copiers; backup and recovery tools, archive and compression utilities; command line interfaces and text-based shells; graphical GUI interfaces with WIMP paradigm; advanced graphics systems; PostScript; fonts; font design; audio system; native, external, widely common used, and third-party filesystems; MultiView; MIME types; USB stacks; Firewire stacks (IEEE 1394); printer drivers; video digitizers; graphic tablets; scanner drivers; genlocks, chroma-key, signal video inverters; infrared devices and remote controls; WiFi and Bluetooth devices; and special devices. Music Music software includes sound design; audio synthesis; music; audio digitizing and sampling; hard disk recording; speech synthesis; audio trackers; MOD music module filetype. Communications software Solutions include modem software, Direct Connect, BBS managing, Fidonet, Packet Radio; Prestel, Videotel, Videotex, Minitel; Teletext, Televideo, Viewdata; FAX, answering machine and voice mail; ISDN; networking and Ethernet protocols; World Wide Web (TCP/IP stacks, browsers, E-mail programs, newsreaders, Internet Radio, proxy server support programs, PPP, Telnet, podcasting, RSS feed, Distributed Net, Google Services, Instant Messaging and chat, FTP and FTP server, weather casting news, Webcam supporting, clock synchronization, SMS Short Messages, Web development and HTTP server, Peer2Peer, VCast (online VCR), YouTube, Flash player, monitoring webpages, Remote Desktop, SSL, SSH, et cetera); communication protocols. Modem, Direct Connect, BBS managing, Fidonet, packet radio Termite, X-Term, A-Term, Baud Bandit I and II, OnLine! Direct parallel and serial cable connect: ParNET, SerNET Fidonet Mail: Amiga version of GNU AWK, AmyBW, Q-Blue QWK and Blue Wave mail readers BBS management: C-NET II, Zeus BBS, Hydra BBS, DLG Pro, Amiexpress, Infinity, Tempest (software) Packet Radio: AmiCom, AmigaTNC, and Amipac Amateur radio: Amiga Amateur Radio Group, AMIGA-FAX/SSTV, METEO/FAX/SSTV, PakRatt, Multicom, AmTOR, AmigaCALL. BTX, Prestel, Videotel, Videotex and Minitel In some European countries, and especially in France, Minitel data transmitting services were popular before the Internet. Minitel had many consumer-level communication services, including chatting, email, railway and broadcast timetables and travel and hotel booking. Minitel used little terminals rented from telephone companies or computers with modems that accept Minitel transmission protocol speed. Amiga Minitel communication programs were written in France, Germany and Italy (Amiga Videotel). AmigaTel (CEPT2 standard, for Minitel) BTX (CEPT1 standard, for the German BTX service) MtA (CEPT2 and CEPT3 standards, for Italian Videotex which supported both) Ruby View (CEPT3, for UK's Prestel) Teletext, Televideo, and Viewdata Teletext is an information retrieval service system based on transmitting data with normal TV broadcast signals without interfering with TV programs. Standalone programs for teletext included Amiga Teletext and the Videotex datatype. FAX, answering machine and voice mail AFax, Amiga-FAX, GPFax, FaxQuik, STFax, TrapFax, AVM (software), MultiAnswer, Zyxel Voice Mail. ISDN ISDN digital telephone and circuit-switched telephone network system were supported via the expansion cards ISDN Master and ISDN Master II, their drivers and related software. Networking and Ethernet protocols Amiga supported SANA-II and MNI drivers, Envoy protocols from IAM, AS225, AS225r2 TCP-IP from Commodore, DECnet, Novell NetWare through Amiga Client for Novell NetWare, Quicknet fast proprietary peer to peer protocol, AppleTalk through emulators. Other network protocols available were AmigaUUCP, DNET, Link-It and Enlan-DFS. Amiga also supports Samba and SMBFS. SANA-II drivers MNI drivers Internet Programs to access the Web are mostly available for newer Amiga platforms. Amiga TCP/IP: AmiTCP, EasyNet, Genesis, Miami and Miami Deluxe, Roadshow for AmigaOS, MosNet and NetStack for MorphOS (both based on AmiTCP). Amiga AMP: Apache, MySQL, Perl/PHP/Python (scripting languages) solution stack AAMP. Browsers: Old browsers or "text only" based ones: Amiga Mosaic, Amiga Lynx, Emacs/W3 WWW client in GNU Emacs Modern browsers up to HTML 3.2 without CSS: IBrowse, Voyager, AWeb, and also Amaya through the X11 Amiga compatibility graphic engine library Cygnix Browsers with HTML 5 and CSS: OWB (Origyn Web Browser, sometimes also referred as Odyssey Web Browser) for AmigaOS and MorphOS NetSurf for AmigaOS and MorphOS Timberwolf web browser for AmigaOS 4 based on Mozilla Firefox 4 E-mail: Thor (software) YAM, Simplemail, Anubis (software) Newsreaders: NewsRog, MicroDot II, NewsCoaster Internet Radio: AmiAMP (Amiga look-alike version of Winamp), Gopher: Gopherexx Proxy server PProxy, Privoxy PPP: AmiPPP, Multilink PPP Telnet: AmTelnet Podcasting: AmiPodder Amiga RSS feed: AmRSS Distributed net: DNetC GPS (Global Positioning System): WxWatch Google services: GoogleMaps: Supported through OWB Browser Google Earth: Supported through OWB Browser GoogleMail: Supported only in 'basic HTML' mode. Google Picasa: Supported through OWB Browser on all Amiga systems or directly through WAManager (MOS) dedicated software. GoogleBar Toolbar: Not supported by Amiga browsers Amiga Instant Messaging and chat: AmTalk, ACUSeeMe, AmIRC, Amiga multi-standard Instant Messaging based on Jabber Extensible Messaging and Presence Protocol, Epistula Instant Messaging, SabreMSN, MomosIRC, AmiGG, GadAmi based on popular Gadu gadu and Tlen Polish instant messaging services, WookieChat, climm, Bitlbee Twitter: AmiTwitter for AmigaOS Classic, AmigaOS 4 and MorphOS. Telephony Messenger voice chat: Not supported Skype VoIP: Not supported H.323 VoIP protocol: Not supported Amiga voice calls: It has been reported that AmTalk supports voice calls between two Amigas running that program, but this feature it is unconfirmed. FTP: ATC (Amiga Trading Centre), Amiga wget, AmFTP, AmiFTP, GUI-FTP, HTTPResume, Charon, CManager, FTPMount (mounts remote FTP as standard Amiga devices), Pete's FTP (PFTP). FTP server: Amiga RC-FTPd, AmiFTPd Weather casting net Amiga WET, Weather Experience, Wetter. Live webcam supporting: AmiWebView, WebVision, WebCam Amiga USB webcam driver: Personal Webcam, Amiga Sonix webcam driver for various models of USB webcams Clock synchronization: FACTS SMS Short Messages: TaskiSMS Web development and HTTP Server: Apache for Amiga, Apache PHP, Thttpd, Thttpd PHP, WebMaker HTML editor, Ami.HTML Webscape. Peer2Peer: Amiga Mule (peer-to-peer), Transmission, enqueueTorrent, BitTorrent, Bourriquet, BeeHive, CTorrent, AmiGift, EDonkey, mlDonkey VCast, Online VCR: otrMUI for MorphOS by Thomas Igracki YouTube: On AmigaOS and MorphOS there are various clients or downloaders for YouTube all based upon scripts made by the ARexx language. These scripts spare some functions from existing Amiga programs like wget and MPlayer and join them in a big meta-application utility able to handle YouTube animations: YouTube downloader.rexx, ib youtube.rexx loading YouTube movies into Amiga browser IBrowse, getvideo.rexx, and YouTube client TubeXX, Flayer ARexx script. Flash player: Amiga SWFPlayer Monitoring webpages: Seventhsense Remote desktop: TwinVNC, VNCServer, MorphVNC Pretty Good Privacy: 2.6.3i. SSL, SSH: AmiSSL, Amiga OpenSSL, Amiga OpenSSH, SSHCON Web album photo sharing services: WAManager (for MorphOS) handles Google Picasa web album service. Other: Sniffy, Net Tools (net ping, resolve, traceroute, etc.), Gallerius (generator of HTML galleries) Communication protocols Skypix is an Amiga communication protocol. It was one of the first interactive online graphics-and-sound protocols. It was introduced in 1987 as part of the Skyline (Atredes) bulletin board system (BBS), running on the Skyline BBS and Skyterm terminal. Years before the World Wide Web, Skypix allowed rich interactive graphics and sound, as well as mouse control, to be a part of the online experience, which was until then limited to text and ANSI graphics. Skypix allowed users to write and integrate graphical programs, and included the first "authoring program", Skypaint. Skypix created enthusiastic game and online application writers years before the World Wide Web made such features a common part of the online experience. It was quickly abandoned as more advanced markup languages for BBS became available and due to the emerging of Internet phenomenon that marginalized the BBS system of communication. Programming Despite the variety of programming languages and compilers, most development was done using C and C++, 680x0 assembler and various Basic dialects. Multimedia Drivers for multimedia devices and special input functions Multimedia keyboards: MMKeyboard Hand-writing recognition: Meridian is a program that performs handwriting recognition input functions using a stylus like those equipping any tablet PC, emulating the stylus by mouse. Graphics tablets: FormAldiHyd, GTDriver, and SlateCtrl are shareware/freeware drivers for several serial-port graphics tablets. "mousev1b" is a driver to use an Apple Newton as a graphics tablet. Accessibility software Jakeboard input software and hardware emulation keyboard and mouse was used by persons with physical limitations and/or problems of movements. Software and hardware schemes are downloadable at BlackBeltSystems Amiga Software page. Talkboard similar to jakeboard, is a downloadable speech-generation system for persons. Optical media Alternative filesystems included AsimCDFS, AmiCDROM, CDVDFS, Allegro CDFS and CacheCDFS. BurnIt!, Frying Pan, MakeCD, AmiDVD, DVDRecord, DVDAuthor could burn CDs, DVDs and/or Blu-ray media. MakeCD was the first Amiga program to support Disk At Once (DAO). Frying Pan was the first Amiga program capable to create DVDs. Frying Pan and BurnIt! are capable to handle DVD. BlueHD from German programmer Carsten Siegner is a MorphOS program capable of authoring and burning HD-DVDs in these formats: Normal Video-DVD (European PAL) HD-Video-DVD HDTV (mkv-h264/AAC) (that are recognized by some Blu-ray players) HD-Video-DVD HDTV (MP4-h264/AVC) Disk images and ISO files management ISO-o-Matic software is a CD image converting software and supports b5i, bin, CD-i, img (normal/CloneCD), mdf (Alcohol 120%), nrg (Nero Burning ROM), pdi and uif. ISOMount mounts CD ISOs, PC floppy disk images and Amiga disk images. It supports: Amiga (ADF) 880 KB either OFS and FFS, MS-DOS (IMG) from 360 KB up to 2.88 MB (Fat12), Atari ST 800 KB (Fat12), MAC GS (file image of Mac has no extensions) 800 KB (MFM encoded), CD (ISO) – every size, including floppy-specific. MountVirtual and DiskImage programs for AmigaOS and MorphOS that mount CD ISO images as standard Amiga devices. Supports CD ISO images and disk images such as ADF, DMS, IFS. MountVirtual requires DiskImage. VirtualCD uses ISOs and CD images as virtual drives. mkisofs and Amkisofs are ports of MaKeISOFileSystem. (A complete list of ISO managements and converters is available on Aminet.) Utilities AmiDock creates application launching docks on the desktop. It became popular in 1989–1990, due to the NeXT computer, that used the same 68030 processor as Amiga 3000) and that it also had the Acorn Archimedes RISC OS docking station utility. In Great Britain, Archimedes computers were adopted in schools. Young Amiga users (there were 1,500,000 Amigas sold in the United Kingdom) spotted docks on Archimedes at school and asked for it on Amiga also. Various launch bars or docking utilities were born as third-party hobby utilities (many examples of early docking software for Amiga like the ToolManager are still hosted in the Aminet repository of all Amiga free software, in the "Utility" directory) and then Amidock was officially integrated in AmigaOS with version 3.9. Directory Opus was a file utility program. When this software was released, Amiga magazines proclaimed that it was the most important software ever released for the Amiga and "should be built into the operating system". Directory Opus went on to create a "replacement OS" for Workbench which overlaid itself upon the system. It started as a file manager, and then became a complete desktop replacement and an alternative to the official Workbench. The utility was later ported to Windows and remains widely used. HyperCache (written by Dave Plummer) was the first commercial disk caching software. Significant in that the base operating system lacked this ability, the addition of caching significantly improved the performance of both floppy and hard discs. SysSpeed was a shareware benchmarking program for Amigas equipped with Motorola 68k and PowerPC CPUs. Much shareware and free software was written for the Amiga and could be obtained via the Fred Fish disk series or from the Aminet software archive. Because the custom chipset shares RAM (and therefore the memory bus) with the CPU, throughput increases measurably if the display is disabled. Some processor-intensive software, such as 3D renderers, disable the display during calculation to gain speed. Emulation Notable emulators included: Commercial Medusa (Atari ST emulator), Fusion (Macintosh Emulator), AMax and AMax II, (Macintosh), GO64 (first Commodore C64 emulator), Transformer and PCTask (it was an Intel 8088 emulator, all software based, capable to emulate Intel PC based platforms ranging from PC XT 4,7 and 7 MHz on Amiga 500, up to 80486 running at 12 MHz on Amiga 4000 and other accelerated Amigas), A64 Package (C64), Amiga BBC Emulator (Acorn BBC emulator) Freeware Atari ST Emulator (AtariST), Hatari (Atari ST and STE), Basilisk II (Macintosh) classic, Frodo (C64), PSXE (Sony PlayStation), Hu-Go! (PC Engine, TurboGrafx-16), FunnyMu (Creativision, Funvision, Wizzard), AmiArcadia (Arcadia 2001 and VC 4000, TVGC). VICE emulator is modular and emulates all 8-bit machines made by Commodore: C64 (a patch of VICE supports C64dtv), C128, PET including CBM II version (but excluding "non-standard" features of SuperPET 9000), Plus4 and VIC-20. Games Thousands of games were produced. At the time it was common for games to be produced for multiple formats. Since the Amiga hardware was the most advanced, games were usually developed on an Amiga, and the Amiga version would be the "gold standard" of the bunch. Demos The Amiga was a focal point for the "demo scene". The Amiga thrived on public domain, freeware and other not-for-profit development. The demo scene spearheaded development in multimedia programming techniques for the Amiga, such that it was de rigueur for the latest visual tricks, soundtrackers and 3D algorithms from the demo scene to end up being used in computer game development. Piracy Because Amiga was one of the first game-oriented computers to feature a built-in floppy disk drive, it simplified software piracy. Many of the arguments pertaining to software copying, intellectual property rights in software, the open-source movement by the early 1990s. It was not unusual for demo groups to be openly involved in software piracy. Anti-piracy measures included the practice of distributing software on disks that contained secret "keys" on high-numbered tracks that were officially unused. The Amiga disk drive officially supported tracks 0–79 from a double-density disk, but could actually read tracks 80 through 82. Standard disk-imaging software ignored these tracks, so that a duplicate of a boxed disk would not contain the key and the software would not work. A similar technique involved writing to normally-unused sectors of the disk. Copy software called "nibble" copiers appeared that could exactly reproduce such disks. Publishers turned to other methods. Hardware dongles were occasionally used for high-end software. AmigaHASP protected Rashumon and was sold by HarmonySoft to Aladdin Systems. Some software manufacturers asked users to type a word from a particular page number and line number of the manual, meaning that successfully copying software included photocopying a large quantity of text. Sometimes the text was designed so that photocopiers would produce illegible copies, meaning that pirates had to manually add the text. Pirates responded with "cracking" software that altered the code to bypass copy protection completely. Every protection scheme was eventually broken. One near exception was the scheme on Dragon's Lair, which became the "holy grail" of crackers worldwide, but it was also broken. "Decrunching" The Amiga's floppy disk drive allowed 880 kilobytes on a single disk, comparable to the RAM of most Amigas (512 kilobytes to 1 megabyte). To increase capacity, Amiga used data compression. The disk drive had a slow transfer rate, such that using processor-based decompression could actually reduce loading times versus loading uncompressed data. Early implementations wrote to a video display register, causing it to break into multiple segments of colorful noise, which would become finer as the decrunching continued. This effect was psychedelic and very easy to implement, so it stuck; it was pioneered on the Commodore 64. TransADF TransADF is a program that transfers the contents of a floppy disk or a similar block device to a file. This program can compress the disk image using the popular deflate algorithm, as utilized by PKZip and gzip, amongst others. References Notes Aminet tree, Aminet Statistics WHDload site download section reports that this program supports actually 1991 games (and it is far from creating a complete list of all Amiga games). Lemon Amiga (a program that adds MAMElike interface to WinUAE Amiga emulator) reports in its statistics window section 3453 known Amiga games. Obligement France reported in January 2009 a list of 13,528 known Amiga games, as divided in 12,416 original games, 953 games extensions or data disks for original games, 125 level editors or game editors for existing games, 34 loaders to let Amiga run some games created on other platforms. Ars Technica: A history of the Amiga, part 4: Enter Commodore, By Jeremy Reimer. October 21, 2007 Existing Amiga-like operating system are AmigaOS, AROS, and MorphOS Transformer Emulation Software article page at Brantford Personal Computer Museum online site Interview by Jim Sachs in March 2009, from Amiga Polish Portal (Polskim Portalu Amigowym) Jim Sachs presents himself on site of SereneScreen Aquarium screensaver program Review of ProWrite on Compute! Magazine, issue 88, September 1987 Chronology of Amiga Computers at pctimeline.info Advertising from Wordperfect on InfoWorld Magazine, issue 30, January 21, 1987, page 34 (retrieved from Brief history of Wordperfect at Cunningham & Cunningham Inc., object-oriented programming consultancy firm based in Portland, Oregon, USA, members of Wordperfect Universe User Group) External links Aminet, the biggest repository of all public domain software for the Amiga platform THE Amiga Software Database – ASD, lists almost all of the known commercial Amiga software, books and CD-ROMs, most of them with cover scans TransADF on Aminet Amiga Lists of software

Operating System (OS)

Multiprocessor system architecture A multiprocessor system is defined as "a system with more than one processor", and, more precisely, "a number of central processing units linked together to enable parallel processing to take place". The key objective of a multiprocessor is to boost a system's execution speed. The other objectives are fault tolerance and application matching. The term "multiprocessor" can be confused with the term "multiprocessing". While multiprocessing is a type of processing in which two or more processors work together to execute multiple programs simultaneously, multiprocessor refers to a hardware architecture that allows multiprocessing. Multiprocessor systems are classified according to how processor memory access is handled and whether system processors are of a single type or various ones. Multiprocessor system types There are many types of multiprocessor systems: Loosely coupled multiprocessor system Tightly coupled multiprocessor system Homogeneous multiprocessor system Heterogeneous multiprocessor system Shared memory multiprocessor system Distributed memory multiprocessor system Uniform memory access (UMA) system cc–NUMA system Hybrid system – shared system memory for global data and local memory for local data Loosely-coupled (distributed memory) multiprocessor system In loosely-coupled multiprocessor systems, each processor has its own local memory, input/output (I/O) channels, and operating system. Processors exchange data over a high-speed communication network by sending messages via a technique known as "message passing". Loosely-coupled multiprocessor systems are also known as distributed-memory systems, as the processors do not share physical memory and have individual I/O channels. System characteristics These systems are able to perform multiple-instructions-on-multiple-data (MIMD) programming. This type of architecture allows parallel processing. The distributed memory is highly scalable. Tightly-coupled (shared memory) multiprocessor system Multiprocessor system with a shared memory closely connected to the processors. A symmetric multiprocessing system is a system with centralized shared memory called main memory (MM) operating under a single operating system with two or more homogeneous processors. There are two types of systems: Uniform memory-access (UMA) system NUMA system Uniform memory access (UMA) system Heterogeneous multiprocessing system Symmetric multiprocessing system (SMP) Heterogeneous multiprocessor system A heterogeneous multiprocessing system contains multiple, but not homogeneous, processing units – central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), or any type of application-specific integrated circuits (ASICs). The system architecture allows any accelerator – for instance, a graphics processor – to operate at the same processing level as the system's CPU. Symmetric multiprocessor system Systems operating under a single OS (operating system) with two or more homogeneous processors and with a centralized shared main memory. A symmetric multiprocessor system (SMP) is a system with a pool of homogeneous processors running under a single OS with a centralized, shared main memory. Each processor, executing different programs and working on different sets of data, has the ability to share common resources (memory, I/O device, interrupt system, and so on) that are connected using a system bus, a crossbar, or a mix of the two, or an address bus and data crossbar. Each processor has its own cache memory that acts as a bridge between the processor and main memory. The function of the cache is to alleviate the need for main-memory data access, thus reducing system-bus traffic. Use of shared memory allows for a uniform memory-access time (UMA). cc-NUMA system It is known that the SMP system has limited scalability. To overcome this limitation, the architecture called "cc-NUMA" (cache coherency–non-uniform memory access) is normally used. The main characteristic of a cc-NUMA system is having shared global memory that is distributed to each node, although the effective "access" a processor has to the memory of a remote component subsystem, or "node", is slower compared to local memory access, which is why the memory access is "non-uniform". A cc–NUMA system is a cluster of SMP systems – each called a "node", which can have a single processor, a multi-core processor, or a mix of the two, of one or other kinds of architecture – connected via a high-speed "connection network" that can be a "link" that can be a single or double-reverse ring, or multi-ring, point-to-point connections, or a mix of these (e.g. IBM Power Systems), bus interconnection (e.g. NUMAq), "crossbar", "segmented bus" (NUMA Bull HN ISI ex Honeywell,) "mesh router", etc. cc-NUMA is also called "distributed shared memory" (DSM) architecture. The difference in access times between local and remote memory can be also an order of magnitude, depending on the kind of connection network used (faster in segmented bus, crossbar, and point-to-point interconnection; slower in serial rings connection). Examples of interconnection To overcome this limit, a large remote cache (see Remote cache) is normally used. With this solution, the cc-NUMA system becomes very close to a large SMP system. Tightly-coupled versus loosely-coupled architecture Both architectures have trade-offs which may be summarized as follows: Loosely-coupled architectures feature high performances of each individual processor but do not enable for easy real-time balancing of the load among processors. Tightly-coupled architectures feature easy load-balancing and distribution among processors but suffer from the bottleneck consisting in the sharing of common resources through one or more buses. Multiprocessor system featuring global data multiplication An intermediate approach, between those of the two previous architectures, is having common resources and local resources, such as local memories (LM), in each processor. The common resources are accessible from all processors via the system bus, while local resources are only accessible to the local processor. Cache memories can be viewed in this perspective as local memories. This system (patented by F. Zulian ), used on the DPX/2 300 Unix based system (Bull Hn Information Systems Italia (ex Honeywell)), is a mix of tightly and loosely coupled systems and makes use of all the advancements of these two architectures. The local memory is divided into two sectors, global data (GD) and local data (LD). The basic concept of this architecture is to have global data, which is modifiable information, accessible by all processors. This information is duplicated and stored in each local memory of each processor. Each time the global data is modified in a local memory, a hardware write-broadcasting is sent to the system bus to all other local memories to maintain the global data coherency. Thus, global data may be read by each processor accessing its own local memory without involving the system bus. System bus access is only required when global data is modified in a local memory to update the copy of this data stored in the other local memories. Local data can be exchanged in a loosely coupled system via message-passing References Parallel computing Classes of computers

Operating System (OS)

FLEX (operating system) The FLEX single-tasking operating system was developed by Technical Systems Consultants (TSC) of West Lafayette, Indiana, for the Motorola 6800 in 1976. Overview The original version was for 8" floppy disks and the (smaller) version for 5.25" floppies was called mini-Flex. It was also later ported to the Motorola 6809; that version was called Flex09. All versions were text-based and intended for use on display devices ranging from printing terminals like the Teletype Model 33 ASR to smart terminals. While no graphic displays were supported by TSC software, some hardware manufacturers supported elementary graphics and pointing devices. It was a disk-based operating system, using 256-byte sectors on soft-sectored floppies; the disk structure used linkage bytes in each sector to indicate the next sector in a file or free list. The directory structure was much simplified as a result. TSC (and others) provided several programming languages including BASIC in two flavors (standard and extended) and a tokenizing version of extended BASIC called Pre-compiled BASIC, FORTH, C, FORTRAN, and PASCAL. TSC also wrote a version of FLEX, Smoke Signal DOS, for the California hardware manufacturer Smoke Signal Broadcasting; this version used forward and back linkage bytes in each sector which increased disk reliability at the expense of compatibility and speed. Later, TSC introduced the multitasking, multi-user, Unix-like UniFLEX operating system, which required DMA disk controllers, 8" disk, and so sold in only small numbers. Several of the TSC computer languages were ported to UniFLEX. During the early 1980s, FLEX was offered by Compusense Ltd as an operating system for the 6809-based Dragon 64 home computer. Commands The following commands are supported by different versions of the FLEX operating system. APPEND ASN BACKUP BUILD CAT COPY COPYNEW C4MAT CLEAN DATE DELETE ECHO EXEC FIX GET I JUMP LINK LIST MEMTEST1 MON N NEWDISK O P P.COR PO PRINT PROT PSP Q QCHECK READPROM RENAME RM S SAVE SAVE.LOW SBOX SP STARTUP TOUCH TTYSET UCAL USEMF VER VERIFY VERSION WRITPROM XOUT Y See also Microsoft BASIC-68 for FLEX Microsoft BASIC-69 for FLEX References External links FLEX User Group FLEX User Group SWTPC 6800 FLEX 2 and 6809 FLEX 9 / UniFLEX / OS9 Level 1 emulator Windows-based 6809 Emulator + Flex09 and 6809 applications AmigaDOS-based 6809 Emulator + Flex09 and 6809 applications The Missing 6809 UniFLEX Archive DragonWiki SWTPC documentation collection FLEX Software Archive Discontinued operating systems Disk operating systems TRS-80 Color Computer 1976 software

Operating System (OS)

OpenMAX OpenMAX (Open Media Acceleration), often shortened as "OMX", is a non-proprietary and royalty-free cross-platform set of C-language programming interfaces. It provides abstractions for routines that are especially useful for processing of audio, video, and still images. It is intended for low power and embedded system devices (including smartphones, game consoles, digital media players, and set-top boxes) that need to efficiently process large amounts of multimedia data in predictable ways, such as video codecs, graphics libraries, and other functions for video, image, audio, voice and speech. OpenMAX provides three layers of interfaces: application layer (AL), integration layer (IL) and development layer (DL). OpenMAX is managed by the non-profit technology consortium Khronos Group. History Initially announced in July 2004. The OpenMAX Working Group was initially founded by members ARM, Motorola, Samsung, STMicroelectronics, and Texas Instruments. Version 1.0 of the specification was published in December 2005. The last draft produced by the OpenMAX Working Group (1.2.0) dates from 2011 and no product has been declared as conformant since 2012. The OpenMAX specification were never updated to support recent codecs like HEVC or VP9, making Android the de facto source of updates to the OpenMAX IL standard. Layers OpenMAX AL is the interface between multimedia applications, such as a media player, and the platform media framework. It allows companies that develop applications to easily migrate their applications to different platforms (customers) that support the OpenMAX AL application programming interface (API). OpenMAX IL is the interface between media framework, (such as StageFright or MediaCodec API on Android, DirectShow on Windows, FFmpeg or Libav on Linux, or GStreamer for cross-platform), and a set of multimedia components (such as an audio or video codecs). It allows companies that build platforms (e.g. allowing an implementation of an MP3 player) to easily change components like MP3 decoders and Equalizer effects and buy components for their platform from different vendors. OpenMAX DL is the interface between physical hardware, such as digital signal processor (DSP) chips, CPUs, GPUs, and software, like video codecs and 3D engines. It allows companies to easily integrate new hardware that supports OpenMAX DL without reoptimizing their low level software. Application layer OpenMAX AL accommodates common multimedia application use cases by standardizing a set of representative objects, as well as interfaces on those objects, to control and configure them. The OpenMAX AL API is divided into two profiles: Media Player and Media Player/Recorder. A platform can be compliant to one or both of these profiles by providing all features included in a profile. It is an application-level, C-language, multimedia API designed for resource-constrained devices. The OpenMAX AL API design puts particular emphasis on ensuring the API is suitable for mobile embedded devices - including basic mobile phones, smart “feature” phones, PDAs and mobile digital music players. Nevertheless, this does not preclude its applicability to other sophisticated media playback and recording devices. The OpenMAX AL API design devotes particular attention to application-developer friendliness. Its status as an open cross-platform API enables developers to port the same source across multiple devices with minimal effort. Thus OpenMAX AL provides a stable base for application development. Features OpenMAX AL features include: Video playback and recording Audio playback and recording Image capture (camera) and display Camera controls Radio and RDS Basic MIDI playback Metadata extraction and insertion Digital TV extension A digital television (DTV) extension specification of OpenMAX AL adds standards-agnostic mobile TV tuning, playback, recording and electronic program guide functionality to OpenMAX AL Multimedia API, as a modular royalty-free, cross-platform C-language API for high-performance digital TV-related applications on mobile and embedded devices. DTV Extension is compatible with all major mobile TV standards (e.g. DVB-H, ISDB-T, T-DMB, etc.), and supports broadcast, unicast and multicast delivery methods for Digital TV. Specification versions OpenMAX AL 1.0 Provisional Specification - a provisional version, dated 2007-09-02, to facilitate feedback from the community before the final 1.0 release. OpenMAX AL 1.0 Specification - dated 2009-06-23 OpenMAX AL 1.0.1 Specification - dated 2010-03-12 OpenMAX AL 1.1 Specification - dated 2011-01-18 Implementations Android 4.0 and later exposes OpenMAX AL as part of its NDK (Native Development Kit). LIM OpenMAX is an open source implementation of OpenMAX AL and OpenMAX IL for Linux Bellagio is an open source OpenMAX IL implementation for Linux maintained by STMicroelectronics. Tizonia is an open source OpenMAX IL implementation for Linux GStreamer (GST) is an open source multimedia framework used by several applications. It can use OpenMAX IL modules with its "gst-omx" module. C-only, optimized for NEON (Cortex A8) and SIMD (for ARM11 cores using ARMv6 architecture) optimized OpenMAX DL libraries are available at Comparison with OpenSL ES OpenSL ES (Open Sound Library for Embedded Systems) is another Khronos Group API that also provides an audio library for the same target market as OpenMAX AL, while OpenMAX target the complete multimedia services. OpenSL ES and OpenMAX AL audio subset share the same common architecture and have a few common features: Audio playback and recording Basic MIDI playback Metadata extraction Integration layer The OpenMAX IL API strives to give media components portability across an array of platforms using the C-language. In the OpenMAX IL, components represent individual blocks of functionality. Components can be sources, sinks, codecs, filters, splitters, mixers, or any other data operator. Depending on the implementation, a component could possibly represent a piece of hardware, a software codec, another processor, or a combination thereof. The interface abstracts the hardware and software architecture in the system. The OpenMAX IL API allows the user to load, control, connect, and unload the individual components. This flexible core architecture allows the Integration Layer to easily implement almost any media use case and mesh with existing graph-based media frameworks. The key focus of the OpenMAX IL API is portability of media components. The OpenMAX IL API design devotes particular attention to use case flexibility and optimized data transfers between components. The OpenMAX IL API has been chosen as the base for the API to integrate Audio and Video codecs on Android, this results in most SoC vendors shipping a minimal implementation that only supports the subset required by Android. Applications do not use those OpenMAX IL components directly, but only through the Android MediaCodec API. Android's subset of OpenMAX IL with its extensions is now the de facto standard. In 2011 the provisional version 1.2.0 was released. Open source OpenMAX IL implementations are available, Bellagio, is maintained by STMicroelectronics. LIM OpenMAX, an implementation that has both AL and IL. Android StageFright, an partial implementation of IL that is the de facto standard. Development layer The OpenMAX DL API defines a set of low-level multimedia kernels or media processing building blocks. The building blocks might be used to accelerate traditional computational hotspots within standardized media codecs and other integrated media processing engines. The functional scope of the OpenMAX DL interface spans several domains including signal processing and image processing, audio coding, image coding, and video coding. OpenMAX DL is split into five application domains: AC - Audio Codecs (MP3 decoder and AAC decoder components) IC - Image Codecs (JPEG components) IP - Image Processing (Generic image processing functions) SP - Signal Processing (Generic audio processing functions) VC - Video Codecs (H.264 and MP4 components) OpenMAX DL is, among other companies, openmax_armlibraries implemented by ARM and ANSI C sample code can be downloaded from their webpage. The OpenMAX API is supported by the PlayStation 3 console. Working group The OpenMAX working group was founded alongside sister project OpenVG on July 6, 2004. Promoting members in 2008 were AMD, Apple, ARM, Creative, Dell Inc, Ericsson, Freescale, Imagination Technologies Group plc, Intel, IBM, Motorola, Nokia, Nvidia Corporation, Samsung Electronics Co. Ltd, SK Telecom, Sony Computer Entertainment Inc and Texas Instruments. See also Video Acceleration API (VA API) VDPAU (Video Decode and Presentation API for Unix) X-Video Bitstream Acceleration (XvBA) X-Video Motion Compensation (XvMC) DirectX Video Acceleration (DxVA) API - Microsoft Windows analogue Distributed Codec Engine (libdce) is a Texas Instruments API for the video codec engine in OMAP based embedded systems VideoToolbox is an API from Apple Inc. for hardware-accelerated decoding on Apple TV and Mac OS X. OpenVideo Decode (OVD) – a new open cross-platform video acceleration API from AMD. Nvidia PureVideo - the bit-stream technology from NVIDIA used in their graphics chips to accelerate video decoding on hardware GPU. UVD (Unified Video Decoder) - the bit-stream technology from ATI Technologies used in their graphics chips to accelerate video decoding on hardware GPU. References External links Khronos Group — OpenMAX Overview and API specifications Khronos Group — Public API Registry Khronos Group — OpenMAX AL 1.1 Specification Khronos Group — OpenMAX IL 1.1.2 Specification Khronos Group — OpenMAX DL 1.0.2 Specification ARM - Free OpenMAX Library Mentor Graphics - Nucleus MMF Leverages OpenMAX IL Mentor Graphics - Press Release, Mentor Achieves Industry-First OpenMAX Conformance for Nuclues OS Multimedia Framework Application programming interfaces

Operating System (OS)

Closed platform A closed platform, walled garden, or closed ecosystem is a software system wherein the carrier or service provider has control over applications, content, and/or media, and restricts convenient access to non-approved applicants or content. This is in contrast to an open platform, wherein consumers generally have unrestricted access to applications and content. Overview For example, in telecommunications, the services and applications accessible on a cell phone on any given wireless device were formerly tightly controlled by the mobile operators. The operators limited the applications and developers that were available on users' home portals and home pages. Thus, a service provider might restrict user access to users whose account exhausted the pre-paid money on their account. This has long been a central issue constraining the telecommunications sector, as developers face huge hurdles in making their applications available to end-users. In a more extreme example, the regulated 1970s American telephone system, Bell, owned all the hardware (including all phones) and had indirect control over the information sent through their infrastructure. It was an open government-sanctioned natural monopoly regulated by the Communications Act of 1934. However, in the landmark case Hush-A-Phone v. United States, Bell unsuccessfully sued a company producing plastic telephone attachments. More generally, a walled garden can refer to a closed or exclusive set of information services provided for users. Similar to a real walled garden, a user is unable to escape this closed environment except through the designated entry/exit points or if the walls are removed. Aspects A 2008 Harvard Business School working paper, entitled "Opening Platforms: How, When and Why?", differentiated a platform's openness/closedness by four aspects and gave example platforms: Examples Some examples of walled gardens include: In the 1990s, AOL developed what later was called its "walled garden" model of service. The idea was to preferentially offer sponsored content to users when possible. During this period, CBS paid to provide sports content, ABC paid to provide news, and 1-800-Flowers paid to be the default florist for anyone seeking one. This strategy became AOL's first good method for selling advertisements. In its time, this method was highly profitable to AOL. Amazon's Kindle line of eReaders. As an October 2011 Business Insider article, entitled "How Amazon Makes Money From The Kindle" observes: "Amazon's Kindle is no longer just a product: It's a whole ecosystem." Moreover, as Business Insider noted "The Kindle ecosystem is also Amazon's fastest-growing product and could account for more than 10% of the company's revenue next year." Apple iOS and other mobile devices, which are restricted to running pre-approved applications from a digital distribution service. Barnes & Noble's Nook devices. In late December 2011, B&N began pushing the automatic, over-the-air firmware update 1.4.1 to Nook Tablets that removed users' ability to gain root access to the device and the ability to sideload applications from sources other than the official Barnes and Noble NOOK Store (without modding). Nook HD devices were similarly "closed", until May 2013, when BN opened its ecosystem somewhat by permitting users to install the Google Play Store and the various Android apps offered there, including those of rivals, such as Audible.com, ComiXology, Kindle, Kobo, and Google itself. The Encrypted Media Extensions specification provides APIs to control playback of encrypted content. This is part of the World Wide Web Consortium's web standards and was authored by members working from Google, Microsoft and Netflix. Kwangmyong, the national intranet service that operates in North Korea. It operates as a "walled garden" network, as no information is permitted to enter the network without government approval. Verizon Wireless' CDMA network and policies effectively prohibiting activation of non-Verizon sanctioned devices on their network. Verizon Wireless is frequently noted (and often criticized) for this practice. Permissioned blockchains have been called the “walled gardens” of 2017. Video game consoles have a long history of walled gardens, with developers needing to purchase licences to develop for the platform, and, in some cases, needing editorial approval from the console manufacturer prior to publishing games. See also Data portability Vendor lock-in Business ecosystem Damaged good Dark web Defective by Design Digital rights management Gated community Hardware restriction Open source Software protection dongle User registration References Application programming interfaces Computing platforms Hardware restrictions

Operating System (OS)

Open Mainframe Project Open Mainframe Project is a Collaborative Project managed by the Linux Foundation to encourage the use of Linux-based operating systems and open source software on mainframe computers. The project was announced on August 17, 2015 and was driven by IBM, a major supplier of mainframe hardware, as well as 16 other founding members, that included SUSE, CA Technologies, BMC Software, Compuware as well as clients and partners such as RSM Partner, Vicom Infinity, L3C LLP and ADP, and academic institutions such as Marist College and University of Bedfordshire. Coincident with the announcement, IBM also announced a partnership with Canonical to make the Ubuntu operating system available for their high-end z Systems hardware. Development priorities for the project in 2016 include OpenJDK, Docker and Hyperledger. In February 2016 the Linux Foundation announced new members had joined the Open Mainframe Project: Hitachi Data Systems, Sine Nomine Associates, East Carolina University and DataKinetics, a 35% expansion in the overall membership. Canonical, the organization behind Ubuntu, has also joined. Part of the announcement was the launch of a summer intern program. Projects Zowe Zowe is the first open source project for z/OS. It was announced in August 2018 at SHARE in St. Louis together with the open beta release of version 0.9 that contained contributions from IBM, Computer Associates, and Rocket Software. Version 1.0 was released in February 2019. In September 2019 Phoenix Software International obtained Zowe conformance for their (E)JES Command Line Interface plugins and REST API extension. It narrows the skills gap between new and legacy z/OS developers by offering the choice to work with z/OS either through a Command Line Interface, a "Zowe Explorer" Visual Studio extension, a web browser served from the Zowe Application Framework, or through REST APIs and web sockets served through the API Mediation Layer. Zowe is an extensible platform for tools, and provides the ability for extension through CLI plugins, new applications to be added to the web desktop, and onboarding of REST APIs to the API Mediation Layer. The Zowe conformance program provides certification accreditation to Independent Software Vendors (ISVs) and System Integrators (SIs) building and distributing Zowe extensions. See also Linux on IBM Z References External links Linux Foundation projects IBM

Operating System (OS)

Embedded software Embedded software is computer software, written to control machines or devices that are not typically thought of as computers, commonly known as embedded systems. It is typically specialized for the particular hardware that it runs on and has time and memory constraints. This term is sometimes used interchangeably with firmware. A precise and stable characteristic feature is that no or not all functions of embedded software are initiated/controlled via a human interface, but through machine-interfaces instead. Manufacturers build embedded software into the electronics of cars, telephones, modems, robots, appliances, toys, security systems, pacemakers, televisions and set-top boxes, and digital watches, for example. This software can be very simple, such as lighting controls running on an 8-bit microcontroller with a few kilobytes of memory with the suitable level of processing complexity determined with a Probably Approximately Correct Computation framework (a methodology based on randomized algorithms). However, embedded software can become very sophisticated in applications such as routers, optical network elements，airplanes, missiles, and process control systems. Operating systems Unlike standard computers that generally use an operating systems such as macOS, Windows or Linux, embedded software may use no operating system. When they do use one, a wide variety of operating systems can be chosen from, typically a real-time operating system. Code for embedded software is typically written in C or C++, but various high-level programming languages, such as Java, Python and JavaScript, are now also in common use to target microcontrollers and embedded systems. Assembly languages are often used too, especially in booting and interrupt handling. Ada is used in some military and aviation projects. Differences from application software Most consumers are familiar with application software that provide functionality on a computer. However embedded software is often less visible, but no less complicated. Unlike application software, embedded software has fixed hardware requirements and capabilities, and addition of third-party hardware or software is strictly controlled. Embedded software needs to include all needed device drivers at manufacturing time, and the device drivers are written for the various hardware devices. These device drivers, called BSP (Board support package), form the layer of software containing hardware-specific drivers and other routines that allow a particular operating system (traditionally a real-time operating system, or RTOS) to function in a particular hardware environment (a computer or CPU card), integrated with the RTOS itself. The software is highly dependent on the CPU and specific chips chosen. Most embedded software engineers have at least a passing knowledge of reading schematics, and reading data sheets for components to determine usage of registers and communication system. Conversion between decimal, hexadecimal and binary is useful as well as using bit manipulation. Web applications are often used for managing hardware, although XML files and other output may be passed to a computer for display. File systems with folders are typically used, however SQL databases are often absent. Software development requires use of a cross compiler, which runs on a computer but produces executable code for the target device. Debugging requires use of an in-circuit emulator, and debugging hardware such as JTAG or SWD debuggers. Software developers often have access to the complete kernel (OS) source code. Size of the storage memory and RAM can vary significantly. Some systems run in 16 KB of Flash and 4 KB of RAM with a CPU operating at 8 MHz, other systems can rival contemporary computers. These space requirements lead to more work being done in C or embedded C++, instead of C++. Interpreted languages like BASIC (while e.g. Parallax Propeller can use compiled BASIC) and Java (Java ME Embedded 8.3 is available for e.g. ARM Cortex-M4, Cortex-M7 microcontrollers and older ARM11 used in Raspberry Pi and Intel Galileo Gen. 2) are not commonly used; while an implementation of the interpreted Python 3 language MicroPython is however available expressly for microcontroller use, e.g. 32-bit ARM-based (such as BBC micro:bit) and 16-bit PIC microcontrollers. Communication protocols Communications between processors and between one processor and other components are essential. Besides direct memory addressing, hardware level common protocols include I²C, SPI, serial ports, 1-Wires, Ethernets, and USB. Communications protocols designed for use in embedded systems are available as closed source from companies including InterNiche Technologies and CMX Systems. Open-source protocols stem from uIP, lwip, and others. See also Embedded system Notes References Edward A. Lee, "Embedded Software", Advances in Computers (M. Zelkowitz, editor) 56, Academic Press, London, 2002. Computing terminology Embedded systems

Operating System (OS)

SYSLINUX The Syslinux Project is a suite of five different boot loaders for starting up Linux distros on computers. It was primarily developed by H. Peter Anvin. Components The Syslinux Project consists of five different boot loaders: The eponymous SYSLINUX, used for booting from the FAT filesystem ISOLINUX, used for booting from the ISO 9660 filesystem PXELINUX, used for booting from a network server using the Preboot Execution Environment (PXE) system EXTLINUX, used for booting from Btrfs, ext2, ext3, ext4, FAT, NTFS, UFS/UFS2, and XFS filesystems MEMDISK, emulates a RAM disk for older operating systems like MS-DOS The project also includes two separate menu systems and a development environment for additional modules. SYSLINUX and ISOLINUX SYSLINUX was originally meant for rescue floppy disks, live USBs, or other lightweight environments. ISOLINUX is meant for live CDs and Linux installation CDs. The SYSLINUX bootloader can be used to multiple distributions from a single source such as a USB stick. A minor complication is involved when booting from compact discs. The El Torito standard allows booting in two different modes: No emulation Requires storing the boot information directly on the CD. ISOLINUX is suitable for this mode. Floppy emulation Requires storing the boot information in a disk image file suitable for emulating a FAT-formatted floppy disk. SYSLINUX is suitable for this mode. To have this choice is sometimes useful, since ISOLINUX is vulnerable to BIOS bugs. For that reason, it is handy to be able to boot using SYSLINUX. This mostly affects computers built before about 1999, and, in fact, for modern computers the "no emulation" mode is generally the more reliable method. Newer ISOLINUX versions support creation of so-called "hybrid ISO" images, that put both the El Torito boot record of the compact discs and the master boot record of hard disks into an ISO image. This hybrid image could then be written to both a compact disc or a USB flash drive. PXELINUX PXELINUX is used in conjunction with a PXE-compliant ROM on a network interface controller (NIC), which enables receiving a bootstrap program over the local area network. This bootstrap program loads and configures an operating system kernel that puts the user in control of the computer. Typically, PXELINUX is used for performing Linux installations from a central network server or for booting diskless workstations. EXTLINUX EXTLINUX is a general-purpose bootloader, similar to LILO or GRUB. Since Syslinux 4, EXTLINUX is capable of handling Btrfs, FAT, NTFS, UFS/UFS2, and XFS filesystems. COMBOOT SYSLINUX can be extended by COMBOOT modules written in C or assembly language. 32-bit modules typically use the .c32 filename extension. Version 5 and later do not support 16-bit .com modules. Hardware Detection Tool (HDT) Since the 3.74 release, the Syslinux project hosts the Hardware Detection Tool (HDT) project, licensed under the terms of GNU GPL. This tool is a 32-bit module that displays low-level information for any IA-32–compatible system. It provides both a command-line interface and a semi-graphical menu mode for browsing. HDT is also available as a bootable ISO and a 2.88 MB floppy disk image. The last update of HDT was in 2015; it has since been discontinued. See also Comparison of boot loaders References Sources External links SYSLINUX releases Mailing list Free boot loaders Linux software Linux-only free software

Operating System (OS)

Venix Venix is a discontinued version of the Unix operating system for low-end computers, developed by VenturCom, a "company that specialises in the skinniest implementations of Unix". Overview A working version of Venix/86 for the IBM PC XT was demoed at Comdex in May 1983. It was based on Version 7 Unix with some enhancements from BSD (notably vi, more and csh) and custom inter-process communication mechanisms. It was the first licensed UNIX operating system available for the IBM PC and its compatibles, supported read/write access to a separate DOS/FAT-partition and could run in as little as 128 KB (256 KB - 512 KB recommended). In September 1984, Venix/86 Encore was released; it supported a number of early PC-compatibles, including the AT&T 6300, the Zenith 150, the (first) NCR PC, and the Texas Instruments Professional PC. Venix Encore, which then became Venix 2.0, was still based on Version 7 Unix, and ran on the DEC Rainbow 100 (Venix/86R) as well as PCs (Venix/86 and /286). The system contained a number of enhancements, notably tools to access DOS files directly on a DOS/FAT-partition, and an updated ADB debugger. The system came in two flavors: a 2-user version priced at $800, and an 8-user version at $1,000. There were no technical differences between the two. Confusingly, Venix 2.0 for the DEC PRO-380 microcomputer (Venix/PRO) was based "essentially" on System III. It no longer ran on the Pro350. This is made clear in the ckermit 4E build instructions, which has a special target for Pro running Venix 1.0, but instructs the user to use the sysiii target for the Pro running Venix 2.0. These same sources also make it clear, that Venix had an enhanced TTY interface relative to a pure V7 Unix System. Venix 2.1 was released for at least the PC. Like the original Venix/86, it included a C compiler, a BASIC interpreter and added a Fortran 77 compiler as an option. An optional driver kit made it possible to develop hardware drivers for the system and generate new kernels. In November 1985, Unisource Software Corp., a Venix retailer, announced the availability of RM/Cobol for Venix. From version 3.0, Venix was based on System V. A real-time version based on System V.3.2 was released for the 386 in 1990. The last version, Venix 4.2.1, based on UNIX System V Release 4.2 (UnixWare), was released in 1994. The workstation system included the real-time operating system, NFS and TCP/IP networking, X, OpenLook and Motif GUIs, and the Veritas journaling File System (vxfs). A development system included additionally an ANSI C compiler, a library of real-time functions, GUI development software, real-time development utilities, and selected industrial I/O device drivers. Reception In its 1984 review PC Magazine found Venix functional, despite some bugs in the initial versions. Its use of the BIOS for accessing devices made it more portable than its competitor PC/IX, but slowed down its display processing; the disk access speed was found to be similar. BYTE stated that Venix on the DEC Professional and IBM PC "performed adequately," but criticized its limit on background processes. See also Coherent (operating system) Idris (operating system) Xenix References Further reading Covers and compares PC/IX, Xenix and Venix. External links Professional 325, 350, 380 DEC PRO-350 emulator with VENIX disk images Installing Venix 2.1 in MAME/MESS Venix/386 in the Internet Archive Real-time operating systems UNIX System V Unix variants

Operating System (OS)

GNU GNU () is an extensive collection of free software (383 packages as of January 2022), which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operating systems popularly known as Linux. Most of GNU is licensed under the GNU Project's own General Public License (GPL). GNU is also the project within which the free software concept originated. Richard Stallman, the founder of the project, views GNU as a "technical means to a social end". Relatedly, Lawrence Lessig states in his introduction to the second edition of Stallman's book Free Software, Free Society that in it Stallman has written about "the social aspects of software and how Free Software can create community and social justice". Name GNU is a recursive acronym for "GNU's Not Unix!", chosen because GNU's design is Unix-like, but differs from Unix by being free software and containing no Unix code. Stallman chose the name by using various plays on words, including the song The Gnu. History Development of the GNU operating system was initiated by Richard Stallman while he worked at MIT Artificial Intelligence Laboratory. It was called the GNU Project, and was publicly announced on September 27, 1983, on the net.unix-wizards and net.usoft newsgroups by Stallman. Software development began on January 5, 1984, when Stallman quit his job at the Lab so that they could not claim ownership or interfere with distributing GNU components as free software. The goal was to bring a completely free software operating system into existence. Stallman wanted computer users to be free to study the source code of the software they use, share software with other people, modify the behavior of software, and publish their modified versions of the software. This philosophy was published as the GNU Manifesto in March 1985. Richard Stallman's experience with the Incompatible Timesharing System (ITS), an early operating system written in assembly language that became obsolete due to discontinuation of PDP-10, the computer architecture for which ITS was written, led to a decision that a portable system was necessary. It was thus decided that the development would be started using C and Lisp as system programming languages, and that GNU would be compatible with Unix. At the time, Unix was already a popular proprietary operating system. The design of Unix was modular, so it could be reimplemented piece by piece. Much of the needed software had to be written from scratch, but existing compatible third-party free software components were also used such as the TeX typesetting system, the X Window System, and the Mach microkernel that forms the basis of the GNU Mach core of GNU Hurd (the official kernel of GNU). With the exception of the aforementioned third-party components, most of GNU has been written by volunteers; some in their spare time, some paid by companies, educational institutions, and other non-profit organizations. In October 1985, Stallman set up the Free Software Foundation (FSF). In the late 1980s and 1990s, the FSF hired software developers to write the software needed for GNU. As GNU gained prominence, interested businesses began contributing to development or selling GNU software and technical support. The most prominent and successful of these was Cygnus Solutions, now part of Red Hat. Components The system's basic components include the GNU Compiler Collection (GCC), the GNU C library (glibc), and GNU Core Utilities (coreutils), but also the GNU Debugger (GDB), GNU Binary Utilities (binutils), the GNU Bash shell. GNU developers have contributed to Linux ports of GNU applications and utilities, which are now also widely used on other operating systems such as BSD variants, Solaris and macOS. Many GNU programs have been ported to other operating systems, including proprietary platforms such as Microsoft Windows and macOS. GNU programs have been shown to be more reliable than their proprietary Unix counterparts. As of January 2022, there are a total of 459 GNU packages (including decommissioned, 383 excluding) hosted on the official GNU development site. GNU as an operating system In its original meaning, and one still common in hardware engineering, the operating system is a basic set of functions to control the hardware and manage things like task scheduling and system calls. In modern terminology used by software developers, the collection of these functions is usually referred to as a kernel, while an 'operating system' is expected to have a more extensive set of programmes. The GNU project maintains two kernels itself, allowing the creation of pure GNU operating systems, but the GNU toolchain is also used with non-GNU kernels. Due to the two different definitions of the term 'operating system', there is an ongoing debate concerning the naming of distributions of GNU packages with a non-GNU kernel. (See below.) With kernels maintained by GNU and FSF GNU Hurd The original kernel of GNU Project is the GNU Hurd microkernel, which was the original focus of the Free Software Foundation (FSF). With the April 30, 2015 release of the Debian GNU/Hurd 2015 distro, GNU now provides all required components to assemble an operating system that users can install and use on a computer. However, the Hurd kernel is not yet considered production-ready but rather a base for further development and non-critical application usage. Linux-libre As of 2012, a fork of the Linux kernel became officially part of the GNU Project in the form of Linux-libre, a variant of Linux with all proprietary components removed. The GNU Project has endorsed Linux-libre distributions, such as gNewSense, Trisquel and Parabola GNU/Linux-libre. With non-GNU kernels Because of the development status of Hurd, GNU is usually paired with other kernels such as Linux or FreeBSD. Whether the combination of GNU libraries with external kernels is a GNU operating system with a kernel (e.g. GNU with Linux), because the GNU collection renders the kernel into a usable operating system as understood in modern software development, or whether the kernel is an operating system unto itself with a GNU layer on top (i.e. Linux with GNU), because the kernel can operate a machine without GNU, is a matter of ongoing debate. The FSF maintains that an operating system built using the Linux kernel and GNU tools and utilities should be considered a variant of GNU, and promotes the term GNU/Linux for such systems (leading to the GNU/Linux naming controversy). This view is not exclusive to the FSF. Notably, Debian, one of the biggest and oldest Linux distributions, refers to itself as Debian GNU/Linux. Copyright, GNU licenses, and stewardship The GNU Project recommends that contributors assign the copyright for GNU packages to the Free Software Foundation, though the Free Software Foundation considers it acceptable to release small changes to an existing project to the public domain. However, this is not required; package maintainers may retain copyright to the GNU packages they maintain, though since only the copyright holder may enforce the license used (such as the GNU GPL), the copyright holder in this case enforces it rather than the Free Software Foundation. For the development of needed software, Stallman wrote a license called the GNU General Public License (first called Emacs General Public License), with the goal to guarantee users freedom to share and change free software. Stallman wrote this license after his experience with James Gosling and a program called UniPress, over a controversy around software code use in the GNU Emacs program. For most of the 80s, each GNU package had its own license: the Emacs General Public License, the GCC General Public License, etc. In 1989, FSF published a single license they could use for all their software, and which could be used by non-GNU projects: the GNU General Public License (GPL). This license is now used by most of GNU software, as well as a large number of free software programs that are not part of the GNU Project; it also historically has been the most commonly used free software license (though recently challenged by the MIT license). It gives all recipients of a program the right to run, copy, modify and distribute it, while forbidding them from imposing further restrictions on any copies they distribute. This idea is often referred to as copyleft. In 1991, the GNU Lesser General Public License (LGPL), then known as the Library General Public License, was written for the GNU C Library to allow it to be linked with proprietary software. 1991 also saw the release of version 2 of the GNU GPL. The GNU Free Documentation License (FDL), for documentation, followed in 2000. The GPL and LGPL were revised to version 3 in 2007, adding clauses to protect users against hardware restrictions that prevent users from running modified software on their own devices. Besides GNU's packages, the GNU Project's licenses are used by many unrelated projects, such as the Linux kernel, often used with GNU software. A minority of the software used by most of Linux distributions, such as the X Window System, is licensed under permissive free software licenses. Logo The logo for GNU is a gnu head. Originally drawn by Etienne Suvasa, a bolder and simpler version designed by Aurelio Heckert is now preferred. It appears in GNU software and in printed and electronic documentation for the GNU Project, and is also used in Free Software Foundation materials. There was also a modified version of the official logo. It was created by the Free Software Foundation in September 2013 in order to commemorate the 30th anniversary of the GNU Project. See also Free software movement History of free and open-source software List of computing mascots :Category:Computing mascots References External links Ports of GNU utilities for Microsoft Windows The daemon, the GNU and the penguin Free software operating systems GNU Project GNU Project software Mach (kernel) Microkernel-based operating systems Unix variants Acronyms

Operating System (OS)

CP/CMS CP/CMS (Control Program/Cambridge Monitor System) is a discontinued time-sharing operating system of the late 60s and early 70s, known for its excellent performance and advanced features. It had three distinct versions: CP-40/CMS, an important "one-off" research system that established the CP/CMS virtual machine architecture CP-67/CMS, a reimplementation of CP-40/CMS for the IBM System/360-67, and the primary focus of this article CP-370/CMS, a reimplementation of CP-67/CMS for the System/370 – never released as such, but became the foundation of IBM's VM/370 operating system, announced in 1972. Each implementation was a substantial redesign of its predecessor and an evolutionary step forward. CP-67/CMS was the first widely available virtual machine architecture. IBM pioneered this idea with its research systems M44/44X (which used partial virtualization) and CP-40 (which used full virtualization). In addition to its role as the predecessor of the VM family, CP/CMS played an important role in the development of operating system (OS) theory, the design of IBM's System/370, the time-sharing industry, and the creation of a self-supporting user community that anticipated today's free software movement. History Fundamental CP/CMS architectural and strategic parameters were established in CP-40, which began production use at IBM's Cambridge Scientific Center in early 1967. This effort occurred in a complex political and technical milieu, discussed at some length and supported by first-hand quotes in the Wikipedia article History of CP/CMS. In a nutshell: In the early 1960s, IBM sought to maintain dominance over scientific computing, where time-sharing efforts such as CTSS and MIT's Project MAC gained focus. But IBM had committed to a huge project, the System/360, which took the company in a different direction. The time-sharing community was disappointed with the S/360's lack of time-sharing capabilities. This led to key IBM sales losses at Project MAC and Bell Laboratories. IBM's Cambridge Scientific Center (CSC), originally established to support Project MAC, began an effort to regain IBM's credibility in time-sharing, by building a time-sharing operating system for the S/360. This system would eventually become CP/CMS. In the same spirit, IBM designed and released a S/360 model with time-sharing features, the IBM System/360-67, and a time-sharing operating system, TSS/360. TSS failed; but the 360-67 and CP/CMS succeeded, despite internal political battles over time-sharing, and concerted efforts at IBM to scrap the CP/CMS effort. In 1967, CP/CMS production use began, first on CSC's CP-40, then later on CP-67 at Lincoln Laboratories and other sites. It was made available via the IBM Type-III Library in 1968. By 1972, CP/CMS had gone through several releases; it was a robust, stable system running on 44 systems; it could support 60 timesharing users on a S/360-67; and at least two commercial timesharing vendors (National CSS and IDC) were reselling S/360-67 time using CP/CMS technology. In 1972, IBM announced the addition of virtual memory to the S/370 series, along with the VM/370 operating system, a reimplementation of CP/CMS for the S/370. This marked the end of CP/CMS releases, although the system continued its independent existence for some time. VM releases continued to include source code for some time and members of the VM community long remained active contributors. Overview CP/CMS was built by IBM's Cambridge Scientific Center (CSC), a research and development lab with ties to MIT, under the leadership of Robert Creasy. The system's goals, development process, release, and legacy of breakthrough technology, set this system apart from other OSes of its day and from other large IBM projects. It was an open-source system, made available in source code form to all IBM customers at no charge – as part of the unsupported IBM Type-III Library. CP/CMS users supported themselves and each other. Unusual circumstances, described in the History section below, led to this situation. CP/CMS consisted of two main components: CP, the Control Program, created the virtual machine environment. The widely used version was CP-67, ran on the S/360-67. (The research system CP-40 established the architecture. A third version, CP-370, became VM/370.) Instead of explicitly dividing up memory and other resources among users, which had been the traditional approach, CP provided each user with a simulated stand-alone System/360 computer. Each system was able to run any S/360 software that ran on the bare machine and in effect gave each user a private computer system. CMS, the Cambridge Monitor System (and also Console Monitor System – but renamed Conversational Monitor System in VM) was a lightweight single-user operating system, for interactive time-sharing use. By running many copies of CMS in CP's virtual machines – instead of multiple copies of large, traditional multi-tasking OS – the overhead per user was less. This allowed a great number of simultaneous users to share a single S/360. The CP/CMS virtual machine concept was an important step forward in operating system design. By isolating users from each other, CP/CMS greatly improved system reliability and security. By simulating a full, stand-alone computer for each user, CP/CMS could run any S/360 software in a time-sharing environment, not just applications specifically designed for time-sharing. By using lightweight CMS as the primary user interface, CP/CMS achieved unprecedented time-sharing performance. In addition, the simplicity of CMS made it easier to implement user interface enhancements than in traditional OS. IBM reimplemented CP/CMS as its VM/370 product line, released in 1972 when virtual memory was added to the S/370 series. VM/370's successors (such as z/VM) remain in wide use today. (It is important to note that IBM reimplemented CP-67, as it had CP-40, and did not simply rename and repackage it. VM coexisted with CP/CMS and its successors for many years. It is thus appropriate to view CP/CMS as an independent OS, distinct from the VM family.) CP/CMS as free software CP/CMS was distributed in source code form, and many CP/CMS users were actively involved in studying and modifying that source code. Such direct user involvement with a vendor-supplied operating system was unusual. In the CP/CMS era many vendors distributed operating systems in machine-readable source code. IBM provided optional source code for, e.g., OS/360, DOS/360, and for several later mainstream IBM operating systems. With all these systems, some awareness of system source code was also involved in the SYSGEN process, comparable to a kernel build in modern systems also in installing a Starter Set. (Forty years later, the Hercules emulator can be used to run fossilized versions of these systems, based on source code that is now treated as part of the public domain.) The importance of operating system source code has changed over time. Before IBM unbundled software from hardware in 1969, the OS (and most other software) was included in the cost of the hardware. Each vendor had complete responsibility for the entire system, hardware and software. This made the distribution medium relatively unimportant. After IBM's unbundling, OS software was delivered as IBM System Control Program (SCP) software, eventually in object code only (OCO) form. For complicated reasons, CP/CMS was not released in the normal way. It was not supported by IBM, but was made part of the unsupported IBM Type-III Library, a collection of software contributed by IBM personnel (similarly software contributed by customers formed the Type-IV Library). IBM distributed this library to its customers for use 'as is'. The lack of direct IBM support for such products forced active users to support themselves and encouraged modifications and mutual support. CP/CMS and other Type-III products were early forms of free software. Source code distribution of other IBM operating systems may have continued for some time (e.g. OS/360, DOS/360, DOS/VSE, MVS, and even TSS/370, which all today are generally considered to be in the public domain) since they were arguably published without a copyright notice before 1978. However, the unsupported status of CP/CMS placed different pressures on its user community and created the need for source code distribution. Curiously, CP/CMS was contributed to the Type-III Library by MIT's Lincoln Laboratory and not by IBM, despite the fact that the system was built by IBM's Cambridge Scientific Center. This surprising decision has been described as a form of collusion to outmaneuver the IBM political forces opposed to time-sharing. It may also reflect the amount of formal and informal input from MIT and Union Carbide that was contributed to the design and implementation of CP-40, the S/360-67, CP-67, and CMS. See History of CP/CMS (historical notes) for further insights and references on this topic. Many CP/CMS users made extensive modifications to their own copies of the source code. Much of this work was shared among sites and important changes found their way back into the core system. Other users, such as National CSS and some academic sites, continued independent development of CP/CMS, rather than switching to VM/370 when it became available. These efforts diverged from the community, in what today would be termed a software fork. After IBM released VM/370, source code distribution of VM continued for several releases. (The VM project did not adopt the use of PL/S, an internal systems programming language mandated for use within IBM on many comparable projects. The use of PL/S would have made source code distribution impossible. IBM attempted to turn away from assembly language to higher level languages as early as 1965, and was making substantial use of PL/S by 1969, e.g. in MVS. PL/S was considered a trade secret at the time and was not available to customers. IBM apparently made exceptions to this policy much later.) The VM user community continued to make important contributions to the software, as it had during the CP/CMS Type-III period. Few OS or DOS sites exhibited active user involvement in deep operating system internals, but this was found at many VM sites. This reverse support helped CP/CMS concepts survive and evolve, despite VM's second class citizen status at IBM. Architecture The CP/CMS architecture was revolutionary for its time. The system consisted of a virtualizing control program (CP) which created multiple independent virtual machines (VMs). Platform virtualization was possible because of two elements of the IBM System/360-67: Segregation of privileged 'supervisor state' instructions from normal 'problem state' instructions Address translation hardware When a program was running in 'problem state', using a privileged instruction or an invalid memory address would cause the hardware to raise an exception condition. By trapping these conditions, CP could simulate the appropriate behavior, e.g. performing I/O or paging operations. A guest operating system, which would run in 'supervisor state' on a bare machine, was run in 'problem state' under CP. The result was a fully virtualized environment. Each virtual machine had its own set of virtual devices, mapped from the system's real hardware environment. Thus a given dial-up teletype was presented to its VM instance as its virtual console. Note that, in CP-67, certain model-dependent and diagnostic instructions were not virtualized, notably the DIAG instruction. Ultimately, in later development at IBM and elsewhere, DIAG instructions were used to create a non-virtualized interface, to what became called a hypervisor. Client operating systems could use this mechanism to communicate directly with the control program; this offered dramatic performance improvements. Any S/360 operating system could in fact be run under CP, but normal users ran Cambridge Monitor System (CMS), a simple, single-user operating system. CMS allowed users to run programs and manage their virtual devices. CP-67 versions 1 and 2 did not support virtual memory inside a virtual machine. This was added in version 3. At that point, testing and development of CP itself could be done by running a full copy of CP/CMS inside a single virtual machine. Some CP/CMS operating system work, such as CP-370 development and MVS testing, ran four- or five-level deep stacks of hardware and OS simulations. The CP/CMS design is different from IBM's previous monolithic operating systems, it separates complex "big system" (dispatching, hardware management, mass storage) from "little system" (application program execution, file I/O, console input/output). The re-categorization of both systems into their own entities prevents a bug in one users' system from affecting both. This is a model feature in microkernel operating systems. IBM's decision to implement virtualization and virtual memory features in the subsequent S/370 design (although missing from the initial S/370 series) reflects, at least in part, the success of the CP/CMS approach. In turn the survival and success of IBM's VM operating system family, and of virtualization technology in general, owe much to the S/360-67. In many respects, IBM's CP-67 and CP/CMS products anticipated (and heavily influenced) contemporary virtualization software, such as VMware Workstation, Xen, and Microsoft Virtual PC. Related terminology CP: Control Program. CP-40 and CP-67 were implementations for CSC's customized S/360-40 and the standard S/360-67, respectively. CMS: Cambridge Monitor System. This portion of the CP/CMS system was renamed Conversational Monitor System when IBM released VM/370. Unlike the CP-to-VM transition, however, which was a reimplementation, much of CMS was moved without modification from CP/CMS into VM/370. VM: Virtual Machine, initially the term pseudo-machine was used, but soon virtual machine was borrowed from the IBM M44/44X project. It was well established in CP/CMS by the time IBM introduced VM/370. hypervisor: a mechanism for paravirtualization. This term was coined in IBM's reimplementation of CP-67 as VM/370. See also VP/CSS History of IBM Time-sharing system evolution CMS file system Footnotes Citations Detailed citations for points made in this article can be found in History of CP/CMS. External links VM/CMS handbook History of software IBM mainframe operating systems Time-sharing operating systems Virtualization software VM (operating system) 1960s software

Operating System (OS)

Plan 9 from Bell Labs Plan 9 from Bell Labs is a distributed operating system, originating in the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s, and building on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 is free and open-source. The final official release was in early 2015. Under Plan 9, UNIX's everything is a file metaphor is extended via a pervasive network-centric filesystem, and the cursor-addressed, terminal-based I/O at the heart of UNIX-like operating systems is replaced by a windowing system and graphical user interface without cursor addressing, although rc, the Plan 9 shell, is text-based. The name Plan 9 from Bell Labs is a reference to the Ed Wood 1959 cult science fiction Z-movie Plan 9 from Outer Space. (The name of the project's mascot, “Glenda, the Plan 9 Bunny”, is presumably a reference to Wood's film Glen or Glenda.) The system continues to be used and developed by operating system researchers and hobbyists. History Plan 9 from Bell Labs was originally developed, starting in the late 1980s, by members of the Computing Science Research Center at Bell Labs, the same group that originally developed Unix and the C programming language. The Plan 9 team was initially led by Rob Pike, Ken Thompson, Dave Presotto and Phil Winterbottom, with support from Dennis Ritchie as head of the Computing Techniques Research Department. Over the years, many notable developers have contributed to the project, including Brian Kernighan, Tom Duff, Doug McIlroy, Bjarne Stroustrup and Bruce Ellis. Plan 9 replaced Unix as Bell Labs's primary platform for operating systems research. It explored several changes to the original Unix model that facilitate the use and programming of the system, notably in distributed multi-user environments. After several years of development and internal use, Bell Labs shipped the operating system to universities in 1992. Three years later, Plan 9 was made available for commercial parties by AT&T via the book publisher Harcourt Brace. With source licenses costing $350, AT&T targeted the embedded systems market rather than the computer market at large. Ritchie commented that the developers did not expect to do "much displacement" given how established other operating systems had become. By early 1996, the Plan 9 project had been "put on the back burner" by AT&T in favor of Inferno, intended to be a rival to Sun Microsystems' Java platform. In the late 1990s, Bell Labs' new owner Lucent Technologies dropped commercial support for the project and in 2000, a third release was distributed under an open-source license. A fourth release under a new free software license occurred in 2002. A user and development community, including current and former Bell Labs personnel, produced minor daily releases in the form of ISO images. Bell Labs hosted the development. The development source tree is accessible over the 9P and HTTP protocols and is used to update existing installations. In addition to the official components of the OS included in the ISOs, Bell Labs also hosts a repository of externally developed applications and tools. As Bell Labs has moved on to later projects in recent years, development of the official Plan 9 system had stopped. On March 23, 2021, development resumed following the transfer of copyright from Bell Labs to the Plan 9 Foundation. Unofficial development for the system also continues on the 9front fork, where active contributors provide monthly builds and new functionality. So far, the 9front fork has provided the system Wi-Fi drivers, Audio drivers, USB support and built-in game emulator, along with other features. Other recent Plan 9-inspired operating systems include Harvey OS and Jehanne OS. Design concepts Plan 9 is a distributed operating system, designed to make a network of heterogeneous and geographically separated computers function as a single system. In a typical Plan 9 installation, users work at terminals running the window system rio, and they access CPU servers which handle computation-intensive processes. Permanent data storage is provided by additional network hosts acting as file servers and archival storage. Its designers state that, The first idea (a per-process name space) means that, unlike on most operating systems, processes (running programs) each have their own view of the namespace, corresponding to what other operating systems call the file system; a single path name may refer to different resources for different processes. The potential complexity of this setup is controlled by a set of conventional locations for common resources. The second idea (a message-oriented filesystem) means that processes can offer their services to other processes by providing virtual files that appear in the other processes' namespace. The client process's input/output on such a file becomes inter-process communication between the two processes. This way, Plan 9 generalizes the Unix notion of the filesystem as the central point of access to computing resources. It carries over Unix's idea of device files to provide access to peripheral devices (mice, removable media, etc.) and the possibility to mount filesystems residing on physically distinct filesystems into a hierarchical namespace, but adds the possibility to mount a connection to a server program that speaks a standardized protocol and treat its services as part of the namespace. For example, the original window system, called 8½, exploited these possibilities as follows. Plan 9 represents the user interface on a terminal by means of three pseudo-files: , which can be read by a program to get notification of mouse movements and button clicks, , which can be used to perform textual input/output, and , writing to which enacts graphics operations (see bit blit). The window system multiplexes these devices: when creating a new window to run some program in, it first sets up a new namespace in which , and are connected to itself, hiding the actual device files to which it itself has access. The window system thus receives all input and output commands from the program and handles these appropriately, by sending output to the actual screen device and giving the currently focused program the keyboard and mouse input. The program does not need to know if it is communicating directly with the operating system's device drivers, or with the window system; it only has to assume that its namespace is set up so that these special files provide the kind of input and accept the kind of messages that it expects. Plan 9's distributed operation relies on the per-process namespaces as well, allowing client and server processes to communicate across machines in the way just outlined. For example, the command starts a remote session on a computation server. The command exports part of its local namespace, including the user's terminal's devices (, , ), to the server, so that remote programs can perform input/output using the terminal's mouse, keyboard and display, combining the effects of remote login and a shared network filesystem. 9P protocol All programs that wish to provide services-as-files to other programs speak a unified protocol, called 9P. Compared to other systems, this reduces the number of custom programming interfaces. 9P is a generic, medium-agnostic, byte-oriented protocol that provides for messages delivered between a server and a client. The protocol is used to refer to and communicate with processes, programs, and data, including both the user interface and the network. With the release of the 4th edition, it was modified and renamed 9P2000. Unlike most other operating systems, Plan 9 does not provide special application programming interfaces (such as Berkeley sockets, X resources or ioctl system calls) to access devices. Instead, Plan 9 device drivers implement their control interface as a file system, so that the hardware can be accessed by the ordinary file input/output operations read and write. Consequently, sharing the device across the network can be accomplished by mounting the corresponding directory tree to the target machine. Union directories and namespaces Plan 9 allows the user to collect the files (called names) from different directory trees in a single location. The resulting union directory behaves as the concatenation of the underlying directories (the order of concatenation can be controlled); if the constituent directories contain files having the same name, a listing of the union directory ( or ) will simply report duplicate names. Resolution of a single path name is performed top-down: if the directories and are unioned into with first, then denotes if it exists, only if it exists and does not exist, and no file if neither exists. No recursive unioning of subdirectories is performed, so if exists, the files in are not accessible through the union. A union directory can be created by using the command: ; bind /arm/bin /bin ; bind -a /acme/bin/arm /bin ; bind -b /usr/alice/bin /bin In the example above, is mounted at , the contents of replacing the previous contents of . Acme's directory is then union mounted after , and Alice's personal directory is union mounted before. When a file is requested from , it is first looked for in , then in , and then finally in . The separate process namespaces thus usually replace the notion of a search path in the shell. A path environment variable () still exists in the rc shell (the shell mainly used in Plan 9); however, rc's path environment variable conventionally only contains the and directories and modifying the variable is discouraged, instead, adding additional commands should be done by binding several directories together as a single .<ref name="rc_the_plan_9_shell-section18" Unlike in Plan 9, the path environment variable of Unix shells should be set to include the additional directories whose executable files need to be added as commands. Furthermore, the kernel can keep separate mount tables for each process, and can thus provide each process with its own file system namespace. Processes' namespaces can be constructed independently, and the user may work simultaneously with programs that have heterogeneous namespaces. Namespaces may be used to create an isolated environment similar to chroot, but in a more secure way. Plan 9's union directory architecture inspired 4.4BSD and Linux union file system implementations, although the developers of the BSD union mounting facility found the non-recursive merging of directories in Plan 9 "too restrictive for general purpose use". Special virtual filesystem /proc Instead of having system calls specifically for process management, Plan 9 provides the file system. Each process appears as a directory containing information and control files which can be manipulated by the ordinary file IO system calls. The file system approach allows Plan 9 processes to be managed with simple file management tools such as ls and cat; however, the processes cannot be copied and moved as files. /net Plan 9 does not have specialised system calls or ioctls for accessing the networking stack or networking hardware. Instead, the file system is used. Network connections are controlled by reading and writing control messages to control files. Sub-directories such as and are used as an interface to their respective protocols. Unicode To reduce the complexity of managing character encodings, Plan 9 uses Unicode throughout the system. The initial Unicode implementation was ISO/IEC 10646-1:1993. Ken Thompson invented UTF-8, which became the native encoding in Plan 9. The entire system was converted to general use in 1992. UTF-8 preserves backwards compatibility with traditional null-terminated strings, enabling more reliable information processing and the chaining of multilingual string data with Unix pipes between multiple processes. Using a single UTF-8 encoding with characters for all cultures and regions eliminates the need for switching between code sets. Combining the design concepts Though interesting on their own, the design concepts of Plan 9 were supposed to be most useful when combined. For example, to implement a network address translation (NAT) server, a union directory can be created, overlaying the router's directory tree with its own . Similarly, a virtual private network (VPN) can be implemented by overlaying in a union directory a hierarchy from a remote gateway, using secured 9P over the public Internet. A union directory with the hierarchy and filters can be used to sandbox an untrusted application or to implement a firewall. In the same manner, a distributed computing network can be composed with a union directory of hierarchies from remote hosts, which allows interacting with them as if they are local. When used together, these features allow for assembling a complex distributed computing environment by reusing the existing hierarchical name system. Software for Plan 9 As a benefit from the system's design, most tasks in Plan 9 can be accomplished by using ls, cat, grep, cp and rm utilities in combination with the rc shell (the default Plan 9 shell). Factotum is an authentication and key management server for Plan 9. It handles authentication on behalf of other programs such that both secret keys and implementation details need only be known to Factotum. Graphical programs Unlike Unix, Plan 9 was designed with graphics in mind. After booting, a Plan 9 terminal will run the rio windowing system, in which the user can create new windows displaying rc. Graphical programs invoked from this shell replace it in its window. The plumber provides an inter-process communication mechanism which allows system-wide hyperlinking. Sam and acme are Plan 9's text editors. Storage system Plan 9 supports the Kfs, Paq, Cwfs, FAT, and Fossil file systems. The last was designed at Bell Labs specifically for Plan 9 and provides snapshot storage capability. It can be used directly with a hard drive or backed with Venti, an archival file system and permanent data storage system. Software development The distribution package for Plan 9 includes special compiler variants and programming languages, and provides a tailored set of libraries along with a windowing user interface system specific to Plan 9. The bulk of the system is written in a dialect of C (ANSI C with some extensions and some other features left out). The compilers for this language were custom built with portability in mind; according to their author, they "compile quickly, load slowly, and produce medium quality object code". A concurrent programming language called Alef was available in the first two editions, but was then dropped for maintenance reasons and replaced by a threading library for C. Unix compatibility Though Plan 9 was supposed to be a further development of Unix concepts, compatibility with preexisting Unix software was never the goal for the project. Many command-line utilities of Plan 9 share the names of Unix counterparts, but work differently. Plan 9 can support POSIX applications and can emulate the Berkeley socket interface through the ANSI/POSIX Environment (APE) that implements an interface close to ANSI C and POSIX, with some common extensions (the native Plan 9 C interfaces conform to neither standard). It also includes a POSIX-compatible shell. APE's authors claim to have used it to port the X Window System (X11) to Plan 9, although they do not ship X11 "because supporting it properly is too big a job". Some Linux binaries can be used with the help of a "linuxemu" (Linux emulator) application; however, it is still a work in progress. Vice versa, the vx32 virtual machine allows a slightly modified Plan 9 kernel to run as a user process in Linux, supporting unmodified Plan 9 programs. Reception Comparison to contemporary operating systems In 1991, Plan 9's designers compared their system to other early nineties operating systems in terms of size, showing that the source code for a minimal ("working, albeit not very useful") version was less than one-fifth the size of a Mach microkernel without any device drivers (5899 or 4622 lines of code for Plan 9, depending on metric, vs. 25530 lines). The complete kernel comprised 18000 lines of code. (According to a 2006 count, the kernel was then some 150,000 lines, but this was compared against more than 4.8 million in Linux.) Within the operating systems research community, as well as the commercial Unix world, other attempts at achieving distributed computing and remote filesystem access were made concurrently with the Plan 9 design effort. These included the Network File System and the associated vnode architecture developed at Sun Microsystems, and more radical departures from the Unix model such as the Sprite OS from UC Berkeley. Sprite developer Brent Welch points out that the SunOS vnode architecture is limited compared to Plan 9's capabilities in that it does not support remote device access and remote inter-process communication cleanly, even though it could have, had the preexisting UNIX domain sockets (which "can essentially be used to name user-level servers") been integrated with the vnode architecture. One critique of the "everything is a file", communication-by-textual-message design of Plan 9 pointed out limitations of this paradigm compared to the typed interfaces of Sun's object-oriented operating system, Spring: A later retrospective comparison of Plan 9, Sprite and a third contemporary distributed research operating system, Amoeba, found that Impact Plan 9 demonstrated that an integral concept of Unix—that every system interface could be represented as a set of files—could be successfully implemented in a modern distributed system. Some features from Plan 9, like the UTF-8 character encoding of Unicode, have been implemented in other operating systems. Unix-like operating systems such as Linux have implemented 9P, Plan 9's protocol for accessing remote files, and have adopted features of rfork, Plan 9's process creation mechanism. Additionally, in Plan 9 from User Space, several of Plan 9's applications and tools, including the sam and acme editors, have been ported to Unix and Linux systems and have achieved some level of popularity. Several projects seek to replace the GNU operating system programs surrounding the Linux kernel with the Plan 9 operating system programs. The 9wm window manager was inspired by 8½, the older windowing system of Plan 9; wmii is also heavily influenced by Plan 9. In computer science research, Plan 9 has been used as a grid computing platform and as a vehicle for research into ubiquitous computing without middleware. In commerce, Plan 9 underlies Coraid storage systems. However, Plan 9 has never approached Unix in popularity, and has been primarily a research tool: Other factors that contributed to low adoption of Plan 9 include the lack of commercial backup, the low number of end-user applications, and the lack of device drivers. Plan 9 proponents and developers claim that the problems hindering its adoption have been solved, that its original goals as a distributed system, development environment, and research platform have been met, and that it enjoys moderate but growing popularity. Inferno, through its hosted capabilities, has been a vehicle for bringing Plan 9 technologies to other systems as a hosted part of heterogeneous computing grids. Several projects work to extend Plan 9, including 9atom and 9front. These forks augment Plan 9 with additional hardware drivers and software, including an improved version of the Upas e-mail system, the Go compiler, Mercurial version control system support (and now also a git implementation), and other programs. Plan 9 was ported to the Raspberry Pi single-board computer. The Harvey project attempts to replace the custom Plan 9 C compiler with GCC, to leverage modern development tools such as GitHub and Coverity, and speed up development. Derivatives and forks Inferno is a descendant of Plan 9, 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. 9atom augments the Plan 9 distribution with the addition of a 386 PAE kernel, an amd64 cpu and terminal kernel, nupas, extra pc hardware support, IL and Ken's fs. 9front is a fork of Plan 9. It was started to remedy a perceived lack of devoted development resources inside Bell Labs, and has accumulated various fixes and improvements. 9legacy is an alternative distribution. It includes a set of patches based on the current Plan 9 distribution. Akaros is designed for many-core architectures and large-scale SMP systems. Harvey OS is an effort to get the Plan 9 code working with gcc and clang. JehanneOS is an experimental OS derived from Plan 9. Its userland and modules are mostly derived from 9front, its build system from Harvey OS, and its kernel is a fork of the Plan9-9k 64-bit Plan9 kernel. NIX is a fork of Plan9 aimed at multicore systems and cloud computing. node9 is a scripted derivative of Plan9/Inferno that replaces the Limbo programming language and DIS virtual machine with the Lua language and LuaJit virtual machine. It also replaces the Inferno per-platform hosted I/O with Node.js' libuv eventing and I/O for consistent, cross-platform hosting. It's a proof-of-concept that demonstrates that a distributed OS can be constructed from per-process namespaces and generic cloud elements to construct a single-system-image of arbitrary size. Plan B designed to work in distributed environments where the set of available resources is different at different points in time. License Starting with the release of Fourth edition in April 2002, the full source code of Plan 9 from Bell Labs is freely available under Lucent Public License 1.02, which is considered to be an open-source license by the Open Source Initiative (OSI), free software license by the Free Software Foundation, and it passes the Debian Free Software Guidelines. In February 2014, the University of California, Berkeley, was authorized by the current Plan 9 copyright holder – Alcatel-Lucent – to release all Plan 9 software previously governed by the Lucent Public License, Version 1.02 under the GPL-2.0-only. On March 23, 2021, ownership of Plan 9 transferred from Bell Labs to the Plan 9 Foundation, and all previous releases have been relicensed to the MIT License. See also Alef (programming language) Rendezvous (Plan 9) Inferno (operating system) Minix HelenOS References External links 9p.io: Archived mirror of the original official Plan 9 Web site at plan9.bell-labs.com 9fans: Semi-official mailing list for Plan 9 users and developers Plan 9 Foundation 1992 software ARM operating systems Computing platforms Distributed computing architecture Embedded operating systems Free software operating systems Operating system distributions bootable from read-only media Software projects PowerPC operating systems MIPS operating systems X86-64 operating systems X86 operating systems

Operating System (OS)

W (Unix) The command w on many Unix-like operating systems provides a quick summary of every user logged into a computer, what each user is currently doing, and what load all the activity is imposing on the computer itself. The command is a one-command combination of several other Unix programs: , , and . Example Sample output (which may vary between systems): $ w 11:12am up 608 day(s), 19:56, 6 users, load average: 0.36, 0.36, 0.37 User tty login@ idle what smithj pts/5 8:52am w jonesm pts/23 20Apr06 28 -bash harry pts/18 9:01am 9 pine peterb pts/19 21Apr06 emacs -nw html/index.html janetmcq pts/8 10:12am 3days -csh singh pts/12 16Apr06 5:29 /usr/bin/perl -w perl/test/program.pl References External links Unix user management and support-related utilities

Operating System (OS)

User (computing) A user is a person who utilizes a computer or network service. A user often has a user account and is identified to the system by a username (or user name). Other terms for username include login name, screenname (or screen name), account name, nickname (or nick) and handle, which is derived from the identical citizens band radio term. Some software products provide services to other systems and have no direct end users. End user End users are the ultimate human users (also referred to as operators) of a software product. The end user stands in contrast to users who support or maintain the product such as sysops, database administrators and computer technicians. The term is used to abstract and distinguish those who only use the software from the developers of the system, who enhance the software for end users. In user-centered design, it also distinguishes the software operator from the client who pays for its development and other stakeholders who may not directly use the software, but help establish its requirements. This abstraction is primarily useful in designing the user interface, and refers to a relevant subset of characteristics that most expected users would have in common. In user-centered design, personas are created to represent the types of users. It is sometimes specified for each persona which types of user interfaces it is comfortable with (due to previous experience or the interface's inherent simplicity), and what technical expertise and degree of knowledge it has in specific fields or disciplines. When few constraints are imposed on the end-user category, especially when designing programs for use by the general public, it is common practice to expect minimal technical expertise or previous training in end users. The end-user development discipline blurs the typical distinction between users and developers. It designates activities or techniques in which people who are not professional developers create automated behavior and complex data objects without significant knowledge of a programming language. Systems whose actor is another system or a software agent have no direct end users. User account A user's account allows a user to authenticate to a system and potentially to receive authorization to access resources provided by or connected to that system; however, authentication does not imply authorization. To log into an account, a user is typically required to authenticate oneself with a password or other credentials for the purposes of accounting, security, logging, and resource management. Once the user has logged on, the operating system will often use an identifier such as an integer to refer to them, rather than their username, through a process known as identity correlation. In Unix systems, the username is correlated with a user identifier or user ID. Computer systems operate in one of two types based on what kind of users they have: Single-user systems do not have a concept of several user accounts. Multi-user systems have such a concept, and require users to identify themselves before using the system. Each user account on a multi-user system typically has a home directory, in which to store files pertaining exclusively to that user's activities, which is protected from access by other users (though a system administrator may have access). User accounts often contain a public user profile, which contains basic information provided by the account's owner. The files stored in the home directory (and all other directories in the system) have file system permissions which are inspected by the operating system to determine which users are granted access to read or execute a file, or to store a new file in that directory. While systems expect most user accounts to be used by only a single person, many systems have a special account intended to allow anyone to use the system, such as the username "anonymous" for anonymous FTP and the username "guest" for a guest account. Username format Various computer operating-systems and applications expect/enforce different rules for the format. In Microsoft Windows environments, for example, note the potential use of: User Principal Name (UPN) format – for example: UserName@Example.com Down-Level Logon Name format – for example: DOMAIN\UserName Terminology Some usability professionals have expressed their dislike of the term "user" and have proposed changing it. Don Norman stated that "One of the horrible words we use is 'users'. I am on a crusade to get rid of the word 'users'. I would prefer to call them 'people'." Users of computer systems and software products generally lack the technical expertise required to fully understand how they work. Power users use advanced features of programs, though they are not necessarily capable of computer programming and system administration. See also References Computing terminology Identity management Consumer

Operating System (OS)

File descriptor In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typically have non-negative integer values, with negative values being reserved to indicate "no value" or error conditions. File descriptors are a part of the POSIX API. Each Unix process (except perhaps daemons) should have three standard POSIX file descriptors, corresponding to the three standard streams: Overview In the traditional implementation of Unix, file descriptors index into a per-process maintained by the kernel, that in turn indexes into a system-wide table of files opened by all processes, called the . This table records the mode with which the file (or other resource) has been opened: for reading, writing, appending, and possibly other modes. It also indexes into a third table called the inode table that describes the actual underlying files. To perform input or output, the process passes the file descriptor to the kernel through a system call, and the kernel will access the file on behalf of the process. The process does not have direct access to the file or inode tables. On Linux, the set of file descriptors open in a process can be accessed under the path /proc/PID/fd/, where PID is the process identifier. File descriptor /proc/PID/fd/0 is stdin, /proc/PID/fd/1 is stdout, and /proc/PID/fd/2 is stderr. As a shortcut to these, any running process can also access its own file descriptors through the folders /proc/self/fd and /dev/fd. In Unix-like systems, file descriptors can refer to any Unix file type named in a file system. As well as regular files, this includes directories, block and character devices (also called "special files"), Unix domain sockets, and named pipes. File descriptors can also refer to other objects that do not normally exist in the file system, such as anonymous pipes and network sockets. The FILE data structure in the C standard I/O library usually includes a low level file descriptor for the object in question on Unix-like systems. The overall data structure provides additional abstraction and is instead known as a file handle. Operations on file descriptors The following lists typical operations on file descriptors on modern Unix-like systems. Most of these functions are declared in the <unistd.h> header, but some are in the <fcntl.h> header instead. Creating file descriptors (Linux) (Linux) (Linux) (Linux) (Linux) (Linux) (Linux) (Linux) (with flag CLONE_PIDFD, Linux) (Linux) (Linux) Deriving file descriptors Operations on a single file descriptor , , , , , (also used for sending FDs to other processes over a Unix domain socket) , , , (Linux) , (Linux) (Linux) (Linux) (Linux) (Linux) (with P_PIDFD ID type, Linux) (stdio function:converts file descriptor to FILE*) (stdio function: prints to file descriptor) Operations on multiple file descriptors , , , , (Linux, takes a single epoll filedescriptor to wait on many other file descriptors) (for Linux) (for BSD-based systems). , (for Linux) (for Linux) (for Linux) Operations on the file descriptor table The function is used to perform various operations on a file descriptor, depending on the command argument passed to it. There are commands to get and set attributes associated with a file descriptor, including and . (BSD and Solaris only; deletes all file descriptors greater than or equal to specified number) (duplicates an existing file descriptor guaranteeing to be the lowest number available file descriptor) , (Close fd1 if necessary, and make file descriptor fd1 point to the open file of fd2) Operations that modify process state (sets the process's current working directory based on a directory file descriptor) (maps ranges of a file into the process's address space) File locking and Sockets (creates a new file descriptor for an incoming connection) (shuts down one or both halves of a full duplex connection) Miscellaneous (a large collection of miscellaneous operations on a single file descriptor, often associated with a device) Upcoming operations A series of new operations on file descriptors has been added to many modern Unix-like systems, as well as numerous C libraries, to be standardized in a future version of POSIX. The at suffix signifies that the function takes an additional first argument supplying a file descriptor from which relative paths are resolved, the forms lacking the at suffix thus becoming equivalent to passing a file descriptor corresponding to the current working directory. The purpose of these new operations is to defend against a certain class of TOCTOU attacks. File descriptors as capabilities Unix file descriptors behave in many ways as capabilities. They can be passed between processes across Unix domain sockets using the sendmsg() system call. Note, however, that what is actually passed is a reference to an "open file description" that has mutable state (the file offset, and the file status and access flags). This complicates the secure use of file descriptors as capabilities, since when programs share access to the same open file description, they can interfere with each other's use of it by changing its offset or whether it is blocking or non-blocking, for example. In operating systems that are specifically designed as capability systems, there is very rarely any mutable state associated with a capability itself. A Unix process' file descriptor table is an example of a C-list. See also fuser (Unix) lsof File Control Block (FCB) - an alternative scheme in C/PM and early versions of DOS References POSIX Unix file system technology de:Handle#Datei-Handle

Operating System (OS)

Microkernel In computer science, a microkernel (often abbreviated as μ-kernel) is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system (OS). These mechanisms include low-level address space management, thread management, and inter-process communication (IPC). If the hardware provides multiple rings or CPU modes, the microkernel may be the only software executing at the most privileged level, which is generally referred to as supervisor or kernel mode. Traditional operating system functions, such as device drivers, protocol stacks and file systems, are typically removed from the microkernel itself and are instead run in user space. In terms of the source code size, microkernels are often smaller than monolithic kernels. The MINIX 3 microkernel, for example, has only approximately 12,000 lines of code. History Microkernels trace their roots back to Danish computer pioneer Per Brinch Hansen and his tenure in Danish computer company Regnecentralen where he led software development efforts for the RC 4000 computer. In 1967, Regnecentralen was installing a RC 4000 prototype in a Polish fertilizer plant in Puławy. The computer used a small real-time operating system tailored for the needs of the plant. Brinch Hansen and his team became concerned with the lack of generality and reusability of the RC 4000 system. They feared that each installation would require a different operating system so they started to investigate novel and more general ways of creating software for the RC 4000. In 1969, their effort resulted in the completion of the RC 4000 Multiprogramming System. Its nucleus provided inter-process communication based on message-passing for up to 23 unprivileged processes, out of which 8 at a time were protected from one another. It further implemented scheduling of time slices of programs executed in parallel, initiation and control of program execution at the request of other running programs, and initiation of data transfers to or from peripherals. Besides these elementary mechanisms, it had no built-in strategy for program execution and resource allocation. This strategy was to be implemented by a hierarchy of running programs in which parent processes had complete control over child processes and acted as their operating systems. Following Brinch Hansen's work, microkernels have been developed since the 1970s. The term microkernel itself first appeared no later than 1981. Microkernels were meant as a response to changes in the computer world, and to several challenges adapting existing "mono-kernels" to these new systems. New device drivers, protocol stacks, file systems and other low-level systems were being developed all the time. This code was normally located in the monolithic kernel, and thus required considerable work and careful code management to work on. Microkernels were developed with the idea that all of these services would be implemented as user-space programs, like any other, allowing them to be worked on monolithically and started and stopped like any other program. This would not only allow these services to be more easily worked on, but also separated the kernel code to allow it to be finely tuned without worrying about unintended side effects. Moreover, it would allow entirely new operating systems to be "built up" on a common core, aiding OS research. Microkernels were a very hot topic in the 1980s when the first usable local area networks were being introduced.. The AmigaOS Exec kernel was an early example, introduced in 1986 and used in a PC with relative commercial success. The lack of memory protection, considered in other respects a flaw, allowed this kernel to have very high message-passing performance because it did not need to copy data while exchanging messages between user-space programs. The same mechanisms that allowed the kernel to be distributed into user space also allowed the system to be distributed across network links. The first microkernels, notably Mach created by Richard Rashid, proved to have disappointing performance, but the inherent advantages appeared so great that it was a major line of research into the late 1990s. However, during this time the speed of computers grew greatly in relation to networking systems, and the disadvantages in performance came to overwhelm the advantages in development terms. Many attempts were made to adapt the existing systems to have better performance, but the overhead was always considerable and most of these efforts required the user-space programs to be moved back into the kernel. By 2000, most large-scale Mach kernel efforts had ended, although Apple's macOS, released in 2001, still uses a hybrid kernel called XNU, which combines a heavily modified (hybrid) OSF/1's Mach kernel (OSFMK 7.3 kernel) with code from BSD UNIX, and this kernel is also used in iOS, tvOS, and watchOS. Windows NT, starting with NT 3.1 and continuing with Windows 10, uses a hybrid kernel design. , the Mach-based GNU Hurd is also functional and included in testing versions of Arch Linux and Debian. Although major work on microkernels had largely ended, experimenters continued development. It has since been shown that many of the performance problems of earlier designs were not a fundamental limitation of the concept, but instead due to the designer's desire to use single-purpose systems to implement as many of these services as possible. Using a more pragmatic approach to the problem, including assembly code and relying on the processor to enforce concepts normally supported in software led to a new series of microkernels with dramatically improved performance. Microkernels are closely related to exokernels. They also have much in common with hypervisors, but the latter make no claim to minimality and are specialized to supporting virtual machines; the L4 microkernel frequently finds use in a hypervisor capacity. Introduction Early operating system kernels were rather small, partly because computer memory was limited. As the capability of computers grew, the number of devices the kernel had to control also grew. Throughout the early history of Unix, kernels were generally small, even though they contained various device drivers and file system implementations. When address spaces increased from 16 to 32 bits, kernel design was no longer constrained by the hardware architecture, and kernels began to grow larger. The Berkeley Software Distribution (BSD) of Unix began the era of larger kernels. In addition to operating a basic system consisting of the CPU, disks and printers, BSD added a complete TCP/IP networking system and a number of "virtual" devices that allowed the existing programs to work 'invisibly' over the network. This growth continued for many years, resulting in kernels with millions of lines of source code. As a result of this growth, kernels were prone to bugs and became increasingly difficult to maintain. The microkernel was intended to address this growth of kernels and the difficulties that resulted. In theory, the microkernel design allows for easier management of code due to its division into user space services. This also allows for increased security and stability resulting from the reduced amount of code running in kernel mode. For example, if a networking service crashed due to buffer overflow, only the networking service's memory would be corrupted, leaving the rest of the system still functional. Inter-process communication Inter-process communication (IPC) is any mechanism which allows separate processes to communicate with each other, usually by sending messages. Shared memory is, strictly defined, also an inter-process communication mechanism, but the abbreviation IPC usually refers to message passing only, and it is the latter that is particularly relevant to microkernels. IPC allows the operating system to be built from a number of smaller programs called servers, which are used by other programs on the system, invoked via IPC. Most or all support for peripheral hardware is handled in this fashion, with servers for device drivers, network protocol stacks, file systems, graphics, etc. IPC can be synchronous or asynchronous. Asynchronous IPC is analogous to network communication: the sender dispatches a message and continues executing. The receiver checks (polls) for the availability of the message, or is alerted to it via some notification mechanism. Asynchronous IPC requires that the kernel maintains buffers and queues for messages, and deals with buffer overflows; it also requires double copying of messages (sender to kernel and kernel to receiver). In synchronous IPC, the first party (sender or receiver) blocks until the other party is ready to perform the IPC. It does not require buffering or multiple copies, but the implicit rendezvous can make programming tricky. Most programmers prefer asynchronous send and synchronous receive. First-generation microkernels typically supported synchronous as well as asynchronous IPC, and suffered from poor IPC performance. Jochen Liedtke assumed the design and implementation of the IPC mechanisms to be the underlying reason for this poor performance. In his L4 microkernel he pioneered methods that lowered IPC costs by an order of magnitude. These include an IPC system call that supports a send as well as a receive operation, making all IPC synchronous, and passing as much data as possible in registers. Furthermore, Liedtke introduced the concept of the direct process switch, where during an IPC execution an (incomplete) context switch is performed from the sender directly to the receiver. If, as in L4, part or all of the message is passed in registers, this transfers the in-register part of the message without any copying at all. Furthermore, the overhead of invoking the scheduler is avoided; this is especially beneficial in the common case where IPC is used in an remote procedure call (RPC) type fashion by a client invoking a server. Another optimization, called lazy scheduling, avoids traversing scheduling queues during IPC by leaving threads that block during IPC in the ready queue. Once the scheduler is invoked, it moves such threads to the appropriate waiting queue. As in many cases a thread gets unblocked before the next scheduler invocation, this approach saves significant work. Similar approaches have since been adopted by QNX and MINIX 3. In a series of experiments, Chen and Bershad compared memory cycles per instruction (MCPI) of monolithic Ultrix with those of microkernel Mach combined with a 4.3BSD Unix server running in user space. Their results explained Mach's poorer performance by higher MCPI and demonstrated that IPC alone is not responsible for much of the system overhead, suggesting that optimizations focused exclusively on IPC will have a limited effect. Liedtke later refined Chen and Bershad's results by making an observation that the bulk of the difference between Ultrix and Mach MCPI was caused by capacity cache-misses and concluding that drastically reducing the cache working set of a microkernel will solve the problem. In a client-server system, most communication is essentially synchronous, even if using asynchronous primitives, as the typical operation is a client invoking a server and then waiting for a reply. As it also lends itself to more efficient implementation, most microkernels generally followed L4's lead and only provided a synchronous IPC primitive. Asynchronous IPC could be implemented on top by using helper threads. However, experience has shown that the utility of synchronous IPC is dubious: synchronous IPC forces a multi-threaded design onto otherwise simple systems, with the resulting synchronization complexities. Moreover, an RPC-like server invocation sequentializes client and server, which should be avoided if they are running on separate cores. Versions of L4 deployed in commercial products have therefore found it necessary to add an asynchronous notification mechanism to better support asynchronous communication. This signal-like mechanism does not carry data and therefore does not require buffering by the kernel. By having two forms of IPC, they have nonetheless violated the principle of minimality. Other versions of L4 have switched to asynchronous IPC completely. As synchronous IPC blocks the first party until the other is ready, unrestricted use could easily lead to deadlocks. Furthermore, a client could easily mount a denial-of-service attack on a server by sending a request and never attempting to receive the reply. Therefore, synchronous IPC must provide a means to prevent indefinite blocking. Many microkernels provide timeouts on IPC calls, which limit the blocking time. In practice, choosing sensible timeout values is difficult, and systems almost inevitably use infinite timeouts for clients and zero timeouts for servers. As a consequence, the trend is towards not providing arbitrary timeouts, but only a flag which indicates that the IPC should fail immediately if the partner is not ready. This approach effectively provides a choice of the two timeout values of zero and infinity. Recent versions of L4 and MINIX have gone down this path (older versions of L4 used timeouts). QNX avoids the problem by requiring the client to specify the reply buffer as part of the message send call. When the server replies the kernel copies the data to the client's buffer, without having to wait for the client to receive the response explicitly. Servers Microkernel servers are essentially daemon programs like any others, except that the kernel grants some of them privileges to interact with parts of physical memory that are otherwise off limits to most programs. This allows some servers, particularly device drivers, to interact directly with hardware. A basic set of servers for a general-purpose microkernel includes file system servers, device driver servers, networking servers, display servers, and user interface device servers. This set of servers (drawn from QNX) provides roughly the set of services offered by a Unix monolithic kernel. The necessary servers are started at system startup and provide services, such as file, network, and device access, to ordinary application programs. With such servers running in the environment of a user application, server development is similar to ordinary application development, rather than the build-and-boot process needed for kernel development. Additionally, many "crashes" can be corrected by simply stopping and restarting the server. However, part of the system state is lost with the failing server, hence this approach requires applications to cope with failure. A good example is a server responsible for TCP/IP connections: If this server is restarted, applications will experience a "lost" connection, a normal occurrence in a networked system. For other services, failure is less expected and may require changes to application code. For QNX, restart capability is offered as the QNX High Availability Toolkit. Device drivers Device drivers frequently perform direct memory access (DMA), and therefore can write to arbitrary locations of physical memory, including various kernel data structures. Such drivers must therefore be trusted. It is a common misconception that this means that they must be part of the kernel. In fact, a driver is not inherently more or less trustworthy by being part of the kernel. While running a device driver in user space does not necessarily reduce the damage a misbehaving driver can cause, in practice it is beneficial for system stability in the presence of buggy (rather than malicious) drivers: memory-access violations by the driver code itself (as opposed to the device) may still be caught by the memory-management hardware. Furthermore, many devices are not DMA-capable, their drivers can be made untrusted by running them in user space. Recently, an increasing number of computers feature IOMMUs, many of which can be used to restrict a device's access to physical memory. This also allows user-mode drivers to become untrusted. User-mode drivers actually predate microkernels. The Michigan Terminal System (MTS), in 1967, supported user space drivers (including its file system support), the first operating system to be designed with that capability. Historically, drivers were less of a problem, as the number of devices was small and trusted anyway, so having them in the kernel simplified the design and avoided potential performance problems. This led to the traditional driver-in-the-kernel style of Unix, Linux, and Windows NT. With the proliferation of various kinds of peripherals, the amount of driver code escalated and in modern operating systems dominates the kernel in code size. Essential components and minimality As a microkernel must allow building arbitrary operating system services on top, it must provide some core functionality. At a minimum, this includes: Some mechanisms for dealing with address spaces, required for managing memory protection Some execution abstraction to manage CPU allocation, typically threads or scheduler activations Inter-process communication, required to invoke servers running in their own address spaces This minimal design was pioneered by Brinch Hansen's Nucleus and the hypervisor of IBM's VM. It has since been formalised in Liedtke's minimality principle: A concept is tolerated inside the microkernel only if moving it outside the kernel, i.e., permitting competing implementations, would prevent the implementation of the system's required functionality. Everything else can be done in a usermode program, although device drivers implemented as user programs may on some processor architectures require special privileges to access I/O hardware. Related to the minimality principle, and equally important for microkernel design, is the separation of mechanism and policy, it is what enables the construction of arbitrary systems on top of a minimal kernel. Any policy built into the kernel cannot be overwritten at user level and therefore limits the generality of the microkernel. Policy implemented in user-level servers can be changed by replacing the servers (or letting the application choose between competing servers offering similar services). For efficiency, most microkernels contain schedulers and manage timers, in violation of the minimality principle and the principle of policy-mechanism separation. Start up (booting) of a microkernel-based system requires device drivers, which are not part of the kernel. Typically this means that they are packaged with the kernel in the boot image, and the kernel supports a bootstrap protocol that defines how the drivers are located and started; this is the traditional bootstrap procedure of L4 microkernels. Some microkernels simplify this by placing some key drivers inside the kernel (in violation of the minimality principle), LynxOS and the original Minix are examples. Some even include a file system in the kernel to simplify booting. A microkernel-based system may boot via multiboot compatible boot loader. Such systems usually load statically-linked servers to make an initial bootstrap or mount an OS image to continue bootstrapping. A key component of a microkernel is a good IPC system and virtual-memory-manager design that allows implementing page-fault handling and swapping in usermode servers in a safe way. Since all services are performed by usermode programs, efficient means of communication between programs are essential, far more so than in monolithic kernels. The design of the IPC system makes or breaks a microkernel. To be effective, the IPC system must not only have low overhead, but also interact well with CPU scheduling. Performance On most mainstream processors, obtaining a service is inherently more expensive in a microkernel-based system than a monolithic system. In the monolithic system, the service is obtained by a single system call, which requires two mode switches (changes of the processor's ring or CPU mode). In the microkernel-based system, the service is obtained by sending an IPC message to a server, and obtaining the result in another IPC message from the server. This requires a context switch if the drivers are implemented as processes, or a function call if they are implemented as procedures. In addition, passing actual data to the server and back may incur extra copying overhead, while in a monolithic system the kernel can directly access the data in the client's buffers. Performance is therefore a potential issue in microkernel systems. The experience of first-generation microkernels such as Mach and ChorusOS showed that systems based on them performed very poorly. However, Jochen Liedtke showed that Mach's performance problems were the result of poor design and implementation, specifically Mach's excessive cache footprint. Liedtke demonstrated with his own L4 microkernel that through careful design and implementation, and especially by following the minimality principle, IPC costs could be reduced by more than an order of magnitude compared to Mach. L4's IPC performance is still unbeaten across a range of architectures. While these results demonstrate that the poor performance of systems based on first-generation microkernels is not representative for second-generation kernels such as L4, this constitutes no proof that microkernel-based systems can be built with good performance. It has been shown that a monolithic Linux server ported to L4 exhibits only a few percent overhead over native Linux. However, such a single-server system exhibits few, if any, of the advantages microkernels are supposed to provide by structuring operating system functionality into separate servers. A number of commercial multi-server systems exist, in particular the real-time systems QNX and Integrity. No comprehensive comparison of performance relative to monolithic systems has been published for those multiserver systems. Furthermore, performance does not seem to be the overriding concern for those commercial systems, which instead emphasize reliably quick interrupt handling response times (QNX) and simplicity for the sake of robustness. An attempt to build a high-performance multiserver operating system was the IBM Sawmill Linux project. However, this project was never completed. It has been shown in the meantime that user-level device drivers can come close to the performance of in-kernel drivers even for such high-throughput, high-interrupt devices as Gigabit Ethernet. This seems to imply that high-performance multi-server systems are possible. Security The security benefits of microkernels have been frequently discussed. In the context of security the minimality principle of microkernels is, some have argued, a direct consequence of the principle of least privilege, according to which all code should have only the privileges needed to provide required functionality. Minimality requires that a system's trusted computing base (TCB) should be kept minimal. As the kernel (the code that executes in the privileged mode of the hardware) has unvetted access to any data and can thus violate its integrity or confidentiality, the kernel is always part of the TCB. Minimizing it is natural in a security-driven design. Consequently, microkernel designs have been used for systems designed for high-security applications, including KeyKOS, EROS and military systems. In fact common criteria (CC) at the highest assurance level (Evaluation Assurance Level (EAL) 7) has an explicit requirement that the target of evaluation be "simple", an acknowledgment of the practical impossibility of establishing true trustworthiness for a complex system. Again, the term "simple" is misleading and ill-defined. At least the Department of Defense Trusted Computer System Evaluation Criteria introduced somewhat more precise verbiage at the B3/A1 classes: In 2018, a paper presented at the Asia-Pacific Systems Conference claimed that microkernels were demonstrably safer than monolithic kernels by investigating all published critical CVEs for the Linux kernel at the time. The study concluded that 40% of the issues could not occur at all in a formally verified microkernel, and only 4% of the issues would remain entirely unmitigated in such a system. Third generation More recent work on microkernels has been focusing on formal specifications of the kernel API, and formal proofs of the API's security properties and implementation correctness. The first example of this is a mathematical proof of the confinement mechanisms in EROS, based on a simplified model of the EROS API. More recently (in 2007) a comprehensive set of machine-checked proofs was performed of the properties of the protection model of seL4, a version of L4. This has led to what is referred to as third-generation microkernels, characterised by a security-oriented API with resource access controlled by capabilities, virtualization as a first-class concern, novel approaches to kernel resource management, and a design goal of suitability for formal analysis, besides the usual goal of high performance. Examples are Coyotos, seL4, Nova, Redox and Fiasco.OC. In the case of seL4, complete formal verification of the implementation has been achieved, i.e. a mathematical proof that the kernel's implementation is consistent with its formal specification. This provides a guarantee that the properties proved about the API actually hold for the real kernel, a degree of assurance which goes beyond even CC EAL7. It was followed by proofs of security-enforcement properties of the API, and a proof demonstrating that the executable binary code is a correct translation of the C implementation, taking the compiler out of the TCB. Taken together, these proofs establish an end-to-end proof of security properties of the kernel. Examples Some examples of microkernels are: The L4 microkernel family Zircon Horizon Nanokernel The term nanokernel or picokernel historically referred to: A kernel where the total amount of kernel code, i.e. code executing in the privileged mode of the hardware, is very small. The term picokernel was sometimes used to further emphasize small size. The term nanokernel was coined by Jonathan S. Shapiro in the paper The KeyKOS NanoKernel Architecture. It was a sardonic response to Mach, which claimed to be a microkernel while Shapiro considered it monolithic, essentially unstructured, and slower than the systems it sought to replace. Subsequent reuse of and response to the term, including the picokernel coinage, suggest that the point was largely missed. Both nanokernel and picokernel have subsequently come to have the same meaning expressed by the term microkernel. A virtualization layer underneath an operating system, which is more correctly referred to as a hypervisor. A hardware abstraction layer that forms the lowest-level part of a kernel, sometimes used to provide real-time functionality to normal operating systems, like Adeos. There is also at least one case where the term nanokernel is used to refer not to a small kernel, but one that supports a nanosecond clock resolution. See also Kernel (operating system) Exokernel Hybrid kernel Loadable kernel module Monolithic kernel Microservices Tanenbaum–Torvalds debate Trusted computing base Unikernel Multi-Environment Real-Time References Further reading Scientific articles about microkernels (on CiteSeerX), including: – the basic QNX reference. -the basic reliable reference. – the basic Mach reference. * An assessment of the present and future state of microkernel based OSes as of January 1994 MicroKernel page from the Portland Pattern Repository The Tanenbaum–Torvalds debate The Tanenbaum-Torvalds Debate, 1992.01.29 Tanenbaum, A. S. "Can We Make Operating Systems Reliable and Secure?". Torvalds, L. Linus Torvalds about the microkernels again, 2006.05.09 Shapiro, J. "Debunking Linus's Latest". Tanenbaum, A. S. "Tanenbaum-Torvalds Debate: Part II". Microkernels fr:Noyau de système d'exploitation#Systèmes à micro-noyaux it:Kernel#Microkernel fi:Käyttöjärjestelmän ydin#Mikroydin

Operating System (OS)

Code page 932 (Microsoft Windows) Microsoft Windows code page 932 (abbreviated MS932, Windows-932 or ambiguously CP932), also called Windows-31J amongst other names (see § Terminology below), is the Microsoft Windows code page for the Japanese language, which is an extended variant of the Shift JIS Japanese character encoding. It contains standard 7-bit ASCII codes, and Japanese characters are indicated by the high bit of the first byte being set to 1. Some code points in this page require a second byte, so characters use either 8 or 16 bits for encoding. IBM offer the same extended double-byte codes in their code page 943 (IBM-943 or CP943), which is a combination of the single-byte Code page 897 and the double-byte Code page 941. Windows-31J is the most used non-UTF-8/Unicode Japanese encoding on the web. Actually is the much more declared encoding, but by W3C/WHATWG HTML standards, the encodings are declared the same, and while the latter name is used in the standards it's defined to decode the former. See page for statistics. Terminology Microsoft's Shift JIS variant is known simply as "Code page 932" on Microsoft Windows, however this is ambiguous as IBM's code page 932, while also a Shift JIS variant, lacks the NEC and NEC-selected double-byte vendor extensions which are present in Microsoft's variant (although both include the IBM extensions) and preserves the 1978 ordering of JIS X 0208. IBM's code page 943 (or "IBM-943") includes the same double byte codes as Windows code page 932. Microsoft's version corresponds closely to the encoding referred to as ibm-943_P15A-2003 (with aliases including CP943C and Windows-932) in International Components for Unicode (ICU). There is also a second ICU encoding named ibm-943_P130-1999, which uses different single-byte mappings which more closely match IBM's code page definitions. (See § Single-byte character differences below for details.) Windows code page 932 is registered with the IANA as Windows-31J. The "Windows-31J" label is IANA's and not recognized by Microsoft, which has historically used "shift_jis" instead. The W3C/WHATWG encoding standard used by HTML5 treats the label "shift_jis" interchangeably with "windows-31j" with the intent of being "compatible with deployed content" and matches Windows code page 932 (including the "formerly proprietary extensions from IBM and NEC"). Windows code page 932 is also called MS_Kanji, although IANA treat MS_Kanji as an alias for standard Shift JIS. Python, for example, uses the label MS-Kanji (or cp932) for Windows-932 and the label Shift_JIS (or sjis) for JIS X 0208-defined Shift JIS, without recognising the Windows-31J label. In Japanese editions of Windows, this code page is referred to as "ANSI", since it is the operating system's default 8-bit encoding, even though ANSI was not involved in its definition. Differences from standard Shift JIS Windows-31J is often mistaken for standard Shift JIS (as defined in JIS X 0208:1997 Appendix 1): while similar, the distinction is significant for computer programmers wishing to avoid mojibake. Double-byte character differences In addition to the standard JIS X 0201:1997 and JIS X 0208:1997 characters, Windows-31J includes several JIS X 0208 extensions, namely "NEC special characters (Row 13), NEC selection of IBM extensions (Rows 89 to 92), and IBM extensions (Rows 115 to 119)", in addition to setting some encoding space aside for end user definition. This also differs from IBM-932, which does not include the NEC extensions or NEC selection. The IBM extensions were designed to encode characters from the IBM Japanese DBCS-Host repertoire which were initially absent in JIS X 0208; the because sign ∵ and not sign ￢ were later added to JIS X 0208 itself in 1983, and Microsoft includes them at extension locations as well as their 1983 locations. The NEC extensions also encode the entirety of the IBM repertoire, but in a separate extension within the 94×94 JIS X 0208 grid (in rows 89–92, besides the characters already included in NEC row 13), rather than using Shift JIS codes beyond the JIS X 0208 range; Windows code page 932 includes these 388 characters in both locations. As a result, the because and not signs are encoded three times. Some of these representations were subsequently used for different characters by JIS X 0213 and Shift JIS-2004. For example, compare row 89 in JIS X 0213 (beginning 硃, 硎, 硏…) to row 89 as used by JIS X 0208 with IBM/NEC extensions (beginning 纊, 褜, 鍈…). Consequently, Shift JIS-2004 is not compatible with Windows-31J. In addition to the above, Microsoft uses different (but visually similar) Unicode mapping for several double-byte punctuation characters compared to standard Shift JIS, such as the wave dash being mapped to U+FF5E rather than U+301C, which is followed by ibm-943_P15A-2003 but not ibm-943_P130-1999, and using different mapping for the double byte backslash. Single-byte character differences Windows-932 includes standard 7-bit ASCII mappings for single-byte sequences with the high bit set to 0. Hence, codes 0x5C and 0x7E are mapped to Unicode as U+005C REVERSE SOLIDUS (\, the backslash) and U+007E TILDE (~) respectively, as they are in ASCII (ISO-646-US). This is likewise done by the W3C/WHATWG encoding standard. By contrast, 0x5C is mapped to U+00A5 YEN SIGN (¥) in ISO-646-JP and consequently JIS X 0201, of which standard Shift JIS is an extension. Correspondingly, Windows-31J avoids duplicate encoding of the backslash by mapping the double byte 0x815F to U+FF3C FULLWIDTH REVERSE SOLIDUS, whereas standard Shift JIS maps it to U+005C. However, 0x5C in Windows-932 is nonetheless considered a Yen sign in certain contexts. For this reason, in many Japanese fonts, U+005C is displayed as a Yen symbol, which would normally be represented as U+00A5, rather than as a backslash per Unicode's suggested rendering. U+00A5 is one-way best-fit mapped onto 0x5C in Windows-932. However, code 0x5C in Windows-932 behaves as a reverse solidus (backslash) in all respects (e.g. in file paths on Windows systems) other than how it is displayed by some fonts, and Microsoft's documentation for Windows-932 displays 0x5C as a backslash. This mapping corresponds to the encoding named "ibm-943_P15A-2003" in International Components for Unicode (ICU), except for minor reordering of a few C0 control characters. IBM-943, like IBM-932, is a superset of the single-byte Code page 897, which maps 0x5C to the Yen symbol (¥) and 0x7E to the overline (‾), this is followed by the encoding named "ibm-943_P130-1999" in ICU. Code page 897 (and therefore also IBM-943 and IBM-932) also adds single-byte box-drawing characters replacing certain C0 control characters, however these may still be treated as control characters depending on the context, and are mapped to control characters in ICU. Layout See also LMBCS-16 References External links Microsoft related Microsoft's Reference for Windows Code Page 932 Code page file for MS932 Mapping of Microsoft's Code Page 932 to Unicode ICU Code Page 943C (ibm-943_P15A-2003 alias windows-31j) demonstration IBM related IBM's documentation of Code Page 943 ICU Code Page 943 (ibm-943_P130-1999) demonstration ICU mapping for ibm-943_P130-1999 to Unicode 932 Encodings of Japanese

Operating System (OS)

Windows NT 3.1 Windows NT 3.1 is the first major release of the Windows NT operating system developed by Microsoft, released on July 27, 1993. At the time of Windows NT's release, Microsoft's Windows 3.1 desktop environment had established brand recognition and market share; but Windows 3.1 relied on the DOS operating system for essential functions, and it had a constrictive 16-bit architecture. Windows NT, however, was a complete, 32-bit operating system that retained a desktop environment familiar to Windows 3.1 users. By extending the Windows brand and beginning Windows NT at version 3.1, Microsoft implied that consumers should expect a familiar user experience. The name Windows NT ("New Technology") advertised that this was a re-engineered version of Windows. Windows NT began as a rewrite of the OS/2 operating system, which Microsoft had co-developed with IBM in the 1980s. For several reasons, including the market success of Windows 3.0 in 1990, Microsoft decided to advance Windows rather than OS/2. They relinquished their OS/2 development responsibilities to IBM, and forked their work on OS/2 v3.0 into a competing operating system. Windows NT 3.1 sold about 300,000 copies before it was succeeded by Windows NT 3.5 in 1994. Windows NT 3.1 was available in two editions: Windows NT 3.1 for workstations, and Windows NT 3.1 Advanced Server for servers. When these premiered, their sales were limited by high system requirements, and a general lack of 32-bit applications to take advantage of the OS's data processing capabilities. On December 31, 2000, Microsoft declared Windows NT 3.1 obsolete and stopped providing support and updates for the system. History As NT OS/2 While Microsoft had a major foothold on the personal computer market due to the use of its MS-DOS as the de facto operating system of IBM PC compatibles, Nathan Myhrvold (who had joined Microsoft after its acquisition of Dynamical Systems Research) identified two major threats to Microsoft's monopoly— RISC architectures, which proved to be more powerful than the equivalent Intel processors that MS-DOS ran on, and Unix, a family of cross-platform multitasking operating systems with support for multiprocessing and networking. While the widespread use of Unix was hindered by the need to adapt programs for each individual variant, Bill Gates believed that the combination of a Unix-like operating system with RISC processors could be a market threat, prompting the need for Microsoft to develop a "Unix killer" that could run on multiple architectures. Gates hired Dave Cutler from Digital Equipment Corporation to assist in developing the new operating system; Cutler had left the company after a series of conflicts surrounding its work on the PRISM architecture and its MICA operating system, and agreed to join Microsoft on the condition that he be able to bring a number of staff members from his team at DEC with him. Cutler arrived at Microsoft on October 31, 1988, and work on the future operating system started in November. The operating system was first developed as a revised version of OS/2, an operating system Microsoft had jointly developed with IBM. While OS/2 was originally intended to succeed MS-DOS, it had yet to be commercially successful. The OS was to be designed so it could be ported to different processor platforms, and support multiprocessor systems, which few operating systems did at that time. To target the enterprise market, the OS was also to support networking, the POSIX standard, and a security platform compliant with the "Orange Book" standards; which would require the OS to be a multi-user system with a permission framework and the ability to audit security-related events. Both Microsoft and IBM wanted to market an operating system that appealed to corporate "enterprise software" customers. That meant greater security, reliability, processing power, and computer networking features. However, since Microsoft also wanted to capture market share from Unix on other computing platforms, they needed a system design that was more portable than that of OS/2. To this end, Microsoft began by developing and testing their new operating system for a non-x86 processor: an emulated version of the Intel i860. Alluding to the chip's codename, "N10", Microsoft codenamed their operating system NT OS/2. DEC preemptively sued Microsoft, alleging that they stole code from MICA for use in the new operating system. In an out-of-court settlement, Microsoft agreed to make NT OS/2 compatible with DEC's Alpha processor. The development team originally estimated that development would be complete within 18 months. By April 1989, the NT OS/2 kernel could run inside the i860 emulator. However, the development team later determined that the i860 was unsuitable for the project. By December they had begun porting NT OS/2 to the MIPS R3000 processor instead, and completed the task in three months. Senior Microsoft executive Paul Maritz was targeting a release date in 1992, but the development schedule was uncertain. The company was eager to silence naysayers who speculated that NT wouldn't be on the market until 1994, and had planned to present the new OS at COMDEX in 1990. As Windows NT In May 1990, Microsoft released Windows 3.0, a new version of its MS-DOS-based Windows desktop environment. Windows 3.0 sold well, and the resulting shift in Microsoft's marketing strategy eroded their partnership with IBM—who wanted Microsoft to concentrate solely on developing OS/2 as its primary platform as opposed to building their future business around Windows. Users and developers were unsure of whether to adopt Windows or OS/2 due to these uncertainties (a situation magnified by the fact that the operating systems were incompatible with each other at the API level), while Microsoft's resources were also being drained by the simultaneous development of multiple operating systems. In August 1990, as a response to the popularity of Windows 3.0, the NT OS/2 team decided to re-work the operating system to use an extended 32-bit port of the Windows API known as Win32. Win32 maintained the familiar structure of the 16-bit APIs used by Windows, which would allow developers to easily adapt their software for the new platform while maintaining a level of compatibility with existing software for Windows. With the shift to a Windows-like architecture, the operating system's shell was also changed from OS/2's Presentation Manager to Windows' Program Manager. Due to these changes, NT was not presented at COMDEX 1990 as was originally planned. Neither the general public nor IBM knew about the transformation of NT OS/2 into Windows NT at the time. Although the companies did agree to a revised partnership where IBM and Microsoft would alternate developing major versions of OS/2 instead of collaborating on each version, IBM eventually learned of Microsoft's Windows NT plans in January 1991, and immediately ended the OS/2 partnership. IBM would solely develop OS/2 2.0 (as was planned under the amended version) and all future versions, without any further involvement from Microsoft. In October 1991, Windows NT received its first public demonstration at COMDEX. In an effort to ensure software taking advantage of Windows NT was available upon its release (scheduled for late-1992), Microsoft also distributed a 32-bit software development kit to selected developers in attendance. The demonstration was positively received; PC Magazine called Windows NT "the modern reinvention of the operating system", but at the same time claimed that it was unlikely that the promised backward compatibility would be kept for the final release. In March 1992, Microsoft also released Win32s, which would allow Windows 3.1 to have partial compatibility with Windows NT programs for the purposes of developing software optimized for the platform. At Microsoft's Win32 Professional Developers Conference in June 1992, Windows NT was demonstrated running on x86 and MIPS processors, while a beta version of Windows NT and an updated development kit were also made available. Concurrently, Microsoft announced a new version of its SQL Server product for Windows NT; Unix vendors feared that the software could be a killer app that would affect the market share of Unix systems. Concerns were also raised over NT's memory usage; while most computers of the era shipped with 4 megabytes of RAM, 16 MB was recommended for NTs. Due to the high cost of RAM at the time, critics thought that its high system requirements could affect the sales and adoption of Windows NT. Steps were taken to reduce its memory usage through methods such as paging. Microsoft began releasing public beta builds of NT in October 1992, and a month later at COMDEX, a presentation focusing on third-party software for Windows NT was held. The final pre-release version of NT was released in March 1993, alongside the unveiling of the server version, LAN Manager for Windows NT. Although its stability and performance had improved, there were still fears that the OS could be released in an unfinished state or delayed further into 1993. Release Windows NT 3.1 and Windows NT 3.1 Advanced Server (so numbered to associate them with Windows 3.1) were released on July 26, 1993. At first, only the x86 and MIPS versions shipped; the DEC Alpha version followed in September. Microsoft sold the workstation version for $495, and the server version for $1,495. Ostensibly, the server price was meant to be a promotional discount offered only during the first six months of sale, but they never raised the retail price to the listed one—$2,995. 250 programmers wrote 5.6 million lines of code; the development cost $150 million. In the last year of development, the team fixed more than 30,000 bugs. During the product's lifecycle, Microsoft published three service packs: Service Pack 1 was released on October 8, 1993; Service Pack 2 followed on January 24, 1994; and Service Pack 3's release date was October 29, 1994. The service packs were distributed on CD-ROM and floppy disk, and also through bulletin board systems, CompuServe, and the Internet. Microsoft terminated support for the operating system on December 31, 2000. Support for Windows NT 3.1 RTM (without a service pack) ended on January 8, 1994. Service Pack 1 support ended on April 24, 1994, and finally, Service Pack 2 support ended on January 29, 1995, only 1 year after general availability. Windows NT 3.1 was localized into various languages. Besides English, it was available in Dutch, French, German, Japanese, Spanish and Swedish. The version for workstations, but not Windows NT 3.1 Server, was additionally available in Danish, Finnish, Italian, Norwegian and Portuguese. Operating system goals Cutler set three main goals for Windows NT. The first goal was portability: in contrast to previous operating systems, which were strongly tied to one architecture, Windows NT should be able to operate on multiple architectures. To meet this goal, most of the operating systems, including the operating system core, had to be written in the C programming language. During the planning phase it was clear that this would cause Windows NT to have higher memory consumption than all previous operating systems. Besides the graphics system and parts of the networking system, which were written in C++, only parts of the operating systems which required direct hardware access and performance critical functions were written in assembly language. These parts were isolated so that they could easily be rewritten when porting the operating system to a new architecture. The second goal was reliability: The system should no longer crash due to a faulty application or faulty hardware. This way, the operating system should be made attractive for critical applications. To meet this goal, the architecture of Windows NT was designed so that the operating system core was isolated and applications could not access it directly. The kernel was designed as a microkernel and components of the core were to run atop the kernel in a modular fashion; Cutler knew this principle from his work at Digital. Reliability also includes security, and the operating system should be able to resist external attacks. Mainframes already had a system where every user had their own account which was assigned specific rights by the administrator, this way, users could be prevented access to confidential documents. A virtual memory management was designed to thwart attacks by malware and prevent users from accessing foreign areas of memory. The third goal was called personality: The operating system should be able to run applications designed for various operating systems, such as Windows, MS-DOS and OS/2 applications. The Mach kernel followed a similar concept by moving the APIs to components which operated in user mode as applications, these could be changed and new ones could be added. This principle was applied to Windows NT. Despite all these goals, the performance of the operating system was optimized where possible, by adapting critical sections of the code to fast execution speed. To improve networking performance, large parts of the networking system were moved to the operating system core. Windows NT was designed as a networking operating system. In this branch, Novell had a lead with its product NetWare, mostly because of a lack of competition, and Microsoft failed to develop a product which could challenge NetWare's lead. Cutler hoped to gain additional customers with a reliable networking operating system. Bill Gates already dominated the market of desktop operating systems with MS-DOS and Windows and hoped to do the same in the networking market with Windows NT. He especially hoped to find a market in the emerging number of servers, while at the same time he did not expect a success in the desktop market until 1995. Therefore, Windows NT was positioned as a high-end operating system in an interview with the product manager David Thacher. It was not designed to replace Windows 3.1 completely, but it should rather supplement Microsoft's product palette with an operating system for critical applications. The expectations were 10% to 20% among all Windows sales and a market share of 10% in the high end market, which amounted to one million copies. Platform Architecture While Windows NT 3.1 uses the same graphical user interface as Windows 3.1, it was developed anew. The operating system is not DOS-based, but an independent 32-bit operating system; many concepts were taken from Cutler's previous operating system, VMS. The architecture of Windows NT takes some ideas of the client–server model, like the modular structure and the communication between the modules. System resources like memory, files or devices are viewed as objects by the operating system, which are all accessed in the same way through handles and which can in this way be secured against unauthorized access. The operating system was designed for multiprocessor systems; it supports preemptive multitasking and can make use of threads to run multiple processes in parallel. Using symmetric multiprocessing, the processing usage is evenly distributed among all available processors. The inter-process communication in Windows NT 3.1 is designed around networks; two newly introduced functions, Remote Procedure Call (RPC) and Network DDE, an extension of Dynamic Data Exchange (DDE), facilitate the access and data exchange between processes running on different computers inside a network. The operating system is designed to combine certain elements of a monolithic kernel and a microkernel; nowadays this is most often referred to as a hybrid kernel. The hardware abstraction layer represents the lowermost layer and isolates the operating system from the underlying hardware to make it easy to port the operating system to other platforms. The kernel running atop only has very basic functions like interrupt management and processor synchronization. All other functions of the operating system core are handled by modules which operate independently from one another and can be swapped without affecting the rest of the operating system. Positioned above the operating system core are the subsystems. There are two types of subsystems: one are the integral subsystems, which perform important operating system functions. One such subsystem is the security subsystem, which handles the logon process and monitors the security of the system. The other type of subsystem is the environment subsystem, which exposes the operating system functions to applications via application programming interfaces. The base subsystem is the 32-bit subsystem which runs 32-bit applications written for Windows NT. Windows NT applications can only run on one platform, and must be recompiled for every platform. The 32-bit subsystem also contains all output functions, including the Graphics Device Interface (GDI), so all other subsystems have to call the 32-bit subsystem to be able to output text or graphics. Other subsystems contained in Windows NT 3.1 are the POSIX subsystem, which supports POSIX-compatible applications built for Windows NT, and, in the x86 version only, the OS/2 subsystem, which allows command-line based OS/2 1.x applications to run. The Virtual DOS Machine (VDM) is sometimes also viewed as a subsystem, but is, strictly speaking, a normal 32-bit Windows application. It manages applications originally built for DOS. Built on top is Windows on Windows (WoW), which allows applications built for 16-bit Windows operating systems like Windows 3.1 to run. On x86 computers, the virtual DOS machine uses the virtual 8086 mode to run DOS applications directly, on RISC computers, an emulator licensed from Insignia Solutions is used which emulates a 80286 processor. However, not all DOS and 16-bit Windows applications can be run on Windows NT 3.1 due to various limitations, one of them being the inability of applications to directly access the hardware. As well, VxD files sometimes needed by applications cannot be used with Windows NT 3.1. While pure DOS applications are run in separate memory spaces, 16-bit Windows applications have to share one memory space. While this is done due to compatibility reasons with applications which depend on this ability, like Schedule+ and Microsoft Mail, it also means that 16-bit Windows applications only run in cooperative multitasking. A faulty 16-bit Windows application is in this way able to cause all other 16-bit Windows applications (but not Windows NT itself) to crash. System Windows NT 3.1 provides a boot manager called NTLDR which is loaded during the startup process of the operating system on x86-based computers. It allows a multiboot setup of multiple instances of Windows NT 3.1, as well as MS-DOS and OS/2 1.x. NTLDR is not used for the RISC versions because the RISC computers' firmware provides their own boot manager. Every user has to log on to the computer after Windows NT 3.1 is booted up by pressing the key combination Ctrl+Alt+Del and entering the user name and password. All users have their own user account, and user-specific settings like the Program Manager groups are stored separately for every user. Users can be assigned specific rights, like the right to change the system time or the right to shut down the computer. To facilitate management of user accounts, it is also possible to group multiple user accounts and assign rights to groups of users. Windows NT 3.1 introduced the new NTFS file system. This new file system is more robust against hardware failures and allows assignment of read and write rights to users or groups on the file system level. NTFS supports long file names and has features to accommodate POSIX applications like hard links. For compatibility reasons, Windows NT 3.1 also supports FAT16 as well as OS/2's file system HPFS, but does not support long file names on FAT file system (VFAT). This was added in Windows NT 3.5. Designed as a networking operating system, Windows NT 3.1 supports multiple network protocols. Besides IPX/SPX and NetBEUI, the TCP/IP protocol is supported allowing access to the Internet. Similar to Windows for Workgroups, files and printers can be shared and the access rights and configuration of these resources can be edited over the network. When a network printer is installed, the required drivers are automatically transferred over the network, removing the need to manually install the drivers for every computer. The Remote Access Service (RAS) allows a client from outside the network to connect to the network using a modem, ISDN or X.25 and access its resources. While the workstation allows one RAS connection at a time, the server supports 64. Windows NT 3.1 supports the then-new Unicode standard, a character set which allows multiple languages to be displayed. This facilitates localization of the operating system. All strings, as well as file and folder names, are internally processed in Unicode, but the included programs, like the File Manager, are not Unicode aware, so folders containing Unicode characters cannot be accessed. For demonstration purposes, a Unicode typeface called Lucida Sans Unicode is shipped with Windows NT 3.1 even though it is not installed by default. The previous code pages are still supported for compatibility purposes. The Windows registry, introduced with Windows NT 3.1, is a central, hierarchical configuration database designed to allow configuration of computers over the network and to replace the commonly-used text-based configuration files, like INI files, AUTOEXEC.BAT and CONFIG.SYS. Using the undocumented registry editor, the Windows registry can be viewed and edited by the user. The Advanced Server is designed to manage the workstation computers. It can function as a Domain controller, where all users and groups as well as their rights are stored. This way, a user can log on from any computer in the network, and users can be managed centrally on the server. Trust relationships can be built to other domains to be able to exchange data cross-domain. Using the replication service, files like logon scripts can be synchronized across all computers on the network. The Advanced Server supports the AppleTalk protocol to allow connections to Macintosh computers. Hard drives can be combined to RAIDs in Windows NT 3.1 Advanced Server, the supported configurations are RAID 0, RAID 1 and RAID 5. Included programs Windows NT 3.1, for the most part, comes with 32-bit versions of the components featured in Windows 3.1 and Windows for Workgroups. However, it also included applications specifically aimed at the needs of Windows NT, like the User Manager, the Performance Monitor, the Disk Administrator, the Event Viewer and the Backup application. The Advanced Server contained further, server-specific administration tools. Because Windows NT 3.1 is not DOS-based, a new 32-bit command-line processor, called CMD.EXE was included which was compatible with MS-DOS 5.0. For compatibility reasons, Windows NT 3.1 shipped with a few 16-bit applications, like Microsoft Write or EDLIN. Windows NT 3.1, being an all-new operating system for which no previous drivers could be used, includes a wealth of drivers for various common components and peripherals. This includes common SCSI devices like hard drives, CD-ROM drives, tape drives and image scanners, as well as ISA devices like graphics cards, sound cards and network cards. The PCI bus, however, is expressly not supported. Windows NT 3.1 supports an uninterruptible power supply. Windows NT 3.1 could be installed either by using the CD-ROM and a provided boot disk, or by utilizing a set of twenty-two 3.5" floppies (twenty-three floppies for Advanced Server). Windows NT 3.1 could also be installed over the network. A coupon was included that made it possible to order a set of twenty-seven 5.25" floppies (or twenty-eight floppies for Advanced Server). Compared to the floppies, the CD-ROM contained additional drivers and applications. System requirements Windows NT 3.1 supports multiple platforms: Aside from the x86 architecture, it runs on computers with DEC Alpha or MIPS (R4000 and R4400) processors. Minimum system requirements on x86 systems include a 25 MHz 80386 processor, at least 12 megabytes of memory, 75 megabytes of hard drive space, and a VGA graphics card. RISC systems require 16 megabytes of memory, 92 megabytes of hard drive space, and a CD-ROM drive. The Advanced Server edition requires an 80386 processor with 16 megabytes of memory and 90 megabytes of hard drive space. On RISC systems, 110 megabytes of hard drive space is needed. Windows NT 3.1 supports dual processor systems, while the Advanced Server edition supports up to four processors. Due to an error in the processor detection routine, Windows NT 3.1 cannot be installed on Pentium II or newer processors. Microsoft never fixed the problem, but unofficial patches are available. Reception Windows NT 3.1 sold about 300,000 copies in its first year. The hardware requirements were deemed to be very high at that time; the recommended system requirements of a 486 processor with 16 megabytes of memory were well above the average computer's configuration, and the operating system turned out to be too slow to use. 32-bit applications which could have used the capabilities of Windows NT 3.1 were scarce, so users had to resort to the old 16-bit applications; however, these ran slower than on Windows 3.1. Estimates in November 1993 counted only 150 Windows NT applications. Common types of software, like office suites, were not available for Windows NT 3.1. During the development of the operating system, the API calls were changed so 32-bit applications built on the 1992 pre-release version of Windows NT 3.1 could not be run on the final version. This affected software such as Microsoft Visual C++ 1.0 and Microsoft Fortran PowerStation. RISC systems with Windows NT 3.1 had an even bigger disadvantage: even though they were more powerful than x86 systems, almost no 32-bit applications or drivers were ported to these platforms. 16-bit applications ran much slower under RISC systems because of the 80286 emulation compared to x86 systems which could run 16-bit applications natively, and DOS and 16-bit applications which depended on 386 calls could not be run at all on RISC systems. However, not all reception was negative; the multitasking capabilities of the operating system were rated positively, especially compared to Windows 3.1. Compared to the size of the operating system, the installation turned out to be very easy, even though installing from floppies was a very time-consuming task. The Advanced Server, intended to be the successor to the unsuccessful LAN Manager product, was technically much superior to its predecessor, and only failed to gain success because it shared the same problems with its workstation pendant, such as the low performance running 16-bit applications. The Advanced Server provided a financial advantage for large networks because its price was not dependent on the number of clients, unlike its competitor Novell NetWare. With Windows NT, Microsoft entered a market it could not previously address and which was mostly dominated by Unix, Novell NetWare and OS/2. A test performed by the InfoWorld magazine in November 1993, where the networking capabilities of several operating systems were tested, showed that Windows NT 3.1 was seriously lacking in inter-client communication: it could only connect to its own server via NetBEUI; attempts to connect to Unix, NetWare and OS/2 all failed because no client software was available. For the Advanced Server, only their own client, the Macintosh and, if only limited, OS/2 were able to connect to the server. Even though the operating system's actual success was only moderate, it had a huge lasting impact. Developers of Unix derivations for the first time strived to standardize their operating systems, and Novell was so concerned about its market share that it bought a Unix vendor. Manufacturers of microprocessors hoped to use the portability of the new operating system to increase their own sales, and thus ports of Windows NT were announced for various platforms, like the Sun SPARC architecture and the Clipper architecture. It was recognized that Windows NT would dominate the desktop market as soon as the hardware became powerful enough to run the operating system at an acceptable speed. Eight years later, Microsoft would unify the consumer-oriented Windows line (which had remained MS-DOS based) with the NT line with the October 2001 release of Windows XP—the first consumer-oriented version of Windows to use the NT architecture. Notes and references Notes References: External links Guidebook: Windows NT 3.1 Gallery – Gallery of UI screenshots of Windows NT 3.1 1993 software Products and services discontinued in 2000 3.1 IA-32 operating systems MIPS operating systems

Operating System (OS)

Net (command) In computing, net is a command in IBM OS/2 (including eComStation and ArcaOS), Microsoft Windows and ReactOS used to manage and configure the operating system from the command-line. It is also part of the IBM PC Network Program for DOS. Overview The command is primarily used to manage network resources. It is an external command implemented as net.exe. When used in a batch file, the /Y or /N switches can be used to unconditionally answer Yes or No to questions returned by the command. The net command has several sub-commands that can differ from one implementation or operating system version to another. On Windows CE .NET 4.2, Windows CE 5.0 and Windows Embedded CE 6.0, it is available as an external command stored in . This version only supports the use and view sub-commands. Example The net use command has several network-related functions. Connecting network drive and printer net use can control mounting ("mapping" in Microsoft terminology) drive shares and connecting shared printers in a network environment. This command makes use of the SMB (server message block) and the NetBIOS protocol on port 139 or 445. The basic Windows XP configuration enables this functionality by default. Thus users can connect to and disconnect from shared resources such as computers, printers and drives. net use can display a list of network-connection information on shared resources. Null session connections net use also connects to the IPC$ (interprocess communication share). This is the so-called null session connection, which allows unauthenticated users. The basic syntax for connecting anonymously is: net use \\IP address\IPC$ "" /u:"" For example, typing at the command prompt: net use \\192.168.1.101\IPC$ "" /u:"" attempts to connect to the share IPC$ of the network 192.168.1.101 as an anonymous user with blank password. If successfully connected to the target machine, a lot of information can be gathered such as shares, users, groups, registry keys and more. This would provide a hacker with a lot of information about a remote user. This has changed in Windows NT 4.0 SP6 already. In Windows 2000 "null session connections" could have been enabled after changes of the system-configuration. Similar commands in other OSes Novell NetWare map for mapping volumes (network drives) to drive letters capture for capturing print queues to LPT ports See also List of DOS commands MS-Net References Further reading External links Microsoft TechNet Microcomputer software OS/2 commands Windows administration Windows communication and services

Operating System (OS)

MUSIC/SP MUSIC/SP (Multi-User System for Interactive Computing/System Product; originally "McGill University System for Interactive Computing") was developed at McGill University in the 1970s from an early IBM time-sharing system called RAX (Remote Access Computing System). The system ran on IBM S/360, S/370, and 4300-series mainframe hardware, and offered then-novel features such as file access control and data compression. It was designed to allow academics and students to create and run their programs interactively on terminals, in an era when most mainframe computing was still being done from punched cards. Over the years, development continued and the system evolved to embrace email, the Internet and eventually the World Wide Web. At its peak in the late 1980s, there were over 250 universities, colleges and high school districts that used the system in North and South America, Europe and Asia. By the time of its demise, the MUSIC time-sharing software had been adapted to run under IBM's three major mainframe operating systems: DOS, OS, and VM/CMS, with hardware ranging from small 64K 360s to IBM 9370s and the largest of their mainframes. History 1966 – IBM Remote Access Computing System (RAX) released. 1972 – McGill's RAX modifications accepted by IBM for distribution as "Installed User Program" under the name of "McGill University System for Interactive Computing" (MUSIC). 1978 – MUSIC 4.0 Major change to file system providing longer file names and advanced access control. 1981 – MUSIC 5.0 Support for IBM 4300 series CPUs and FBA disks. 1985 – MUSIC/SP 1.0 Adopted by IBM as "System Product". Support for virtual memory. 1990 – MUSIC/SP 2.2, described by IBM as having "significant enhancements." 1991 – MUSIC/SP 2.3 Internet support and tree-structured file system. Features File system The MUSIC/SP file system was unique in a number of respects. There was a single system-wide file index. The owner's userid and the file name were hashed to locate the file in this index, so any file on the system could be located with a single I/O operation. However, this presented a flat file system to the user. It lacked the directory structure commonly offered by DOS, Microsoft Windows and Unix systems. In 1990 a "tree-structured" directory view of the file system was overlaid on this, bringing the system more in line with the file systems that were then available. By default the information stored in the files was compressed. This offered considerable saving in disk space. The file system had a fairly sophisticated access control scheme allowing the owner to control who could read, write, append to and execute the file. It also had the concept of a "public" file which was visible to all users and a "private" file which was only visible to the owner. In version 2.3, even private files were listed in the common library, with the result that no two users could have files under the same name; by 4.0, this limitation was removed. Virtual memory The initial versions of the system provided no support for virtual memory and address translation. Only one active user could reside in core memory at any time. Swapping (to disk) was used to time-share between different users, and a variable-length timeslice was used. Virtual memory support was introduced in 1985. This allowed multiple users to be in core memory at the same time, removed many of the restrictions in the size of the programs that could be run and provided a significant performance improvement. System performance was also improved by pre-loading commonly used modules into virtual memory at startup time where they could be available to all users simultaneously. Programming languages The system was designed to support academic computing and the teaching of computer science, so a rich suite of programming languages was available. The system nucleus was written in IBM/370 assembler but most of the native applications were written in FORTRAN. The system supported the Waterloo WATFIV and WATBOL compilers and also provided compilers for Pascal, C, PL/I, BASIC, APL, ALGOL, RPG, and GPSS. The system was missing a command scripting language until REXX was ported from CMS in 1984. Later, in 1986, a complete user interface was written entirely in REXX. E-mail and the Internet E-mail was one of the major applications on MUSIC/SP. The e-mail interface initially provided access to local e-mail. As the networks developed, this was expanded to provide access to BITNET and Internet based e-mail. MUSIC/SP did not have direct access to the Internet until 1990, when the University of Wisconsin Wiscnet TCP/IP code was ported to the system, allowing the system to provide access to all Internet services. Compatibility with other IBM systems A major feature of the system was its ability to run programs that were designed to run on IBM's mainstream operating system (MVS). This was accomplished using an MVS emulator that intercepted system calls at the Supervisor Call instruction (SVC) level. Most third-party applications ran in this mode. Rather than write their own version of an application, the MUSIC/SP developers would usually start from the MVS version and rebuild it to run in MVS emulation mode. Since the MVS emulation was a very limited subset of the real thing, the applications generally ran more efficiently on MUSIC/SP. Other features One major advantage the system had in educational environments was that through the use of special lines called "control cards" at the top of a file, source files for any supported language could be automatically directed to the appropriate compiler (Fortran being the default), compiled, linked, and executed, (with compilation, linkage, and execution options also specified in control cards) simply by entering the filename on a command line. A wide variety of terminals were supported as of 1980, including both EBCDIC-based units using IBM-proprietary protocols, and asynchronous ASCII-based units. Since terminals were connected through various types of front-end processors (as per common IBM timesharing practice both then and now), and could therefore function without CPU attention for a considerable amount of time, MUSIC used variable-length time slices, which could, on compute-bound processing, reach a maximum of several seconds per time slice; conversely, if a user filled the output buffer or reached a conversational read, the timeslice would end immediately. Emulation The Sim390 emulator contains a demonstration system of MUSIC/SP. It is freely available and runs on Microsoft Windows. The demonstration system will also run under Hercules. See also Michigan Terminal System Multics time-sharing Time Sharing Option (TSO) VPS/VM an offshoot of Music Time-sharing system evolution References External links MUSIC/SP Sim390 emulator MUSIC/SP demonstration system downloads McGill University Video of using MUSIC/SP on demo system Time-sharing operating systems IBM mainframe operating systems 1970s software McGill University

Operating System (OS)

Xen Xen (pronounced ) is a type-1 hypervisor, providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently. It was originally developed by the University of Cambridge Computer Laboratory and is now being developed by the Linux Foundation with support from Intel, Citrix, Arm Ltd, Huawei, AWS, Alibaba Cloud, AMD, Bitdefender and epam. The Xen Project community develops and maintains Xen Project as free and open-source software, subject to the requirements of the GNU General Public License (GPL), version 2. Xen Project is currently available for the IA-32, x86-64 and ARM instruction sets. Software architecture Xen Project runs in a more privileged CPU state than any other software on the machine, except for Firmware. Responsibilities of the hypervisor include memory management and CPU scheduling of all virtual machines ("domains"), and for launching the most privileged domain ("dom0") - the only virtual machine which by default has direct access to hardware. From the dom0 the hypervisor can be managed and unprivileged domains ("domU") can be launched. The dom0 domain is typically a version of Linux or BSD. User domains may either be traditional operating systems, such as Microsoft Windows under which privileged instructions are provided by hardware virtualization instructions (if the host processor supports x86 virtualization, e.g., Intel VT-x and AMD-V), or paravirtualized operating systems whereby the operating system is aware that it is running inside a virtual machine, and so makes hypercalls directly, rather than issuing privileged instructions. Xen Project boots from a bootloader such as GNU GRUB, and then usually loads a paravirtualized host operating system into the host domain (dom0). History Xen originated as a research project at the University of Cambridge led by Ian Pratt, a senior lecturer in the Computer Laboratory, and his PhD student Keir Fraser. The first public release of Xen was made in 2003, with v1.0 following in 2004. Soon after, Pratt and Fraser along with other Cambridge alumni including Simon Crosby and founding CEO Nick Gault created XenSource Inc. to turn Xen into a competitive enterprise product. To support embedded systems such as smartphone/ IoT with relatively scarce hardware computing resources, the Secure Xen ARM architecture on an ARM CPU was exhibited at Xen Summit on April 17, 2007, held in IBM TJ Watson. The first public release of Secure Xen ARM source code was made at Xen Summit on June 24, 2008 by Sang-bum Suh, a Cambridge alumnus, in Samsung Electronics. On October 22, 2007, Citrix Systems completed its acquisition of XenSource, and the Xen Project moved to the xen.org domain. This move had started some time previously, and made public the existence of the Xen Project Advisory Board (Xen AB), which had members from Citrix, IBM, Intel, Hewlett-Packard, Novell, Red Hat, Sun Microsystems and Oracle. The Xen Advisory Board advises the Xen Project leader and is responsible for the Xen trademark, which Citrix has freely licensed to all vendors and projects that implement the Xen hypervisor. Citrix also used the Xen brand itself for some proprietary products unrelated to Xen, including XenApp and XenDesktop. On April 15, 2013, it was announced that the Xen Project was moved under the auspices of the Linux Foundation as a Collaborative Project. The Linux Foundation launched a new trademark for "Xen Project" to differentiate the project from any commercial use of the older "Xen" trademark. A new community website was launched at xenproject.org as part of the transfer. Project members at the time of the announcement included: Amazon, AMD, Bromium, CA Technologies, Calxeda, Cisco, Citrix, Google, Intel, Oracle, Samsung, and Verizon. The Xen project itself is self-governing. Since version 3.0 of the Linux kernel, Xen support for dom0 and domU exists in the mainline kernel. Release history Uses Internet hosting service companies use hypervisors to provide virtual private servers. Amazon EC2 (since August 2006), IBM SoftLayer, Liquid Web, Fujitsu Global Cloud Platform, Linode, OrionVM and Rackspace Cloud use Xen as the primary VM hypervisor for their product offerings. Virtual machine monitors (also known as hypervisors) also often operate on mainframes and large servers running IBM, HP, and other systems. Server virtualization can provide benefits such as: Consolidation leading to increased utilization Rapid provisioning Dynamic fault tolerance against software failures (through rapid bootstrapping or rebooting) Hardware fault tolerance (through migration of a virtual machine to different hardware) Secure separations of virtual operating systems Support for legacy software as well as new OS instances on the same computer Xen's support for virtual machine live migration from one host to another allows load balancing and the avoidance of downtime. Virtualization also has benefits when working on development (including the development of operating systems): running the new system as a guest avoids the need to reboot the physical computer whenever a bug occurs. Sandboxed guest systems can also help in computer-security research, allowing study of the effects of some virus or worm without the possibility of compromising the host system. Finally, hardware appliance vendors may decide to ship their appliance running several guest systems, so as to be able to execute various pieces of software that require different operating systems. Types of virtualization Xen offers five approaches to running the guest operating system: HVM (hardware virtual machine) HVM with PV drivers PVHVM (paravirtualization with full hardware virtualization, i.e. HVM with PVHVM drivers) PVH (PV in an HVM container) PV (paravirtualization). Xen provides a form of virtualization known as paravirtualization, in which guests run a modified operating system. The guests are modified to use a special hypercall ABI, instead of certain architectural features. Through paravirtualization, Xen can achieve high performance even on its host architecture (x86) which has a reputation for non-cooperation with traditional virtualization techniques. Xen can run paravirtualized guests ("PV guests" in Xen terminology) even on CPUs without any explicit support for virtualization. Paravirtualization avoids the need to emulate a full set of hardware and firmware services, which makes a PV system simpler to manage and reduces the attack surface exposed to potentially malicious guests. On 32-bit x86, the Xen host kernel code runs in Ring 0, while the hosted domains run in Ring 1 (kernel) and Ring 3 (applications). CPUs that support virtualization make it possible to run unmodified guests, including proprietary operating systems (such as Microsoft Windows). This is known as hardware-assisted virtualization, however, in Xen this is known as hardware virtual machine (HVM). HVM extensions provide additional execution modes, with an explicit distinction between the most-privileged modes used by the hypervisor with access to the real hardware (called "root mode" in x86) and the less-privileged modes used by guest kernels and applications with "hardware" accesses under complete control of the hypervisor (in x86, known as "non-root mode"; both root and non-root mode have Rings 0–3). Both Intel and AMD have contributed modifications to Xen to exploit their respective Intel VT-x and AMD-V architecture extensions. Use of ARM v7A and v8A virtualization extensions came with Xen 4.3. HVM extensions also often offer new instructions to allow direct calls by a paravirtualized guest/driver into the hypervisor, typically used for I/O or other operations needing high performance. These allow HVM guests with suitable minor modifications to gain many of the performance benefits of paravirtualized I/O. In current versions of Xen (up to 4.2) only fully virtualized HVM guests can make use of hardware facilities for multiple independent levels of memory protection and paging. As a result, for some workloads, HVM guests with PV drivers (also known as PV-on-HVM, or PVH) provide better performance than pure PV guests. Xen HVM has device emulation based on the QEMU project to provide I/O virtualization to the virtual machines. The system emulates hardware via a patched QEMU "device manager" (qemu-dm) daemon running as a backend in dom0. This means that the virtualized machines see an emulated version of a fairly basic PC. In a performance-critical environment, PV-on-HVM disk and network drivers are used during the normal guest operation, so that the emulated PC hardware is mostly used for booting. Features Administrators can "live migrate" Xen virtual machines between physical hosts across a LAN without loss of availability. During this procedure, the LAN iteratively copies the memory of the virtual machine to the destination without stopping its execution. The process requires a stoppage of around 60–300 ms to perform final synchronization before the virtual machine begins executing at its final destination, providing an illusion of seamless migration. Similar technology can serve to suspend running virtual machines to disk, "freezing" their running state for resumption at a later date. Xen can scale to 4095 physical CPUs, 256 VCPUs per HVM guest, 512 VCPUs per PV guest, 16 TB of RAM per host, and up to 1 TB of RAM per HVM guest or 512 GB of RAM per PV guest. Availability The Xen hypervisor has been ported to a number of processor families: Intel: IA-32, IA-64 (before version 4.2), x86-64 PowerPC: previously supported under the XenPPC project, no longer active after Xen 3.2 ARM: previously supported under the XenARM project for older versions of ARM without virtualization extensions, such as the Cortex-A9. Currently supported since Xen 4.3 for newer versions of the ARM with virtualization extensions, such as the Cortex-A15. MIPS: XLP832 experimental port Hosts Xen can be shipped in a dedicated virtualization platform, such as Citrix Hypervisor (formerly Citrix XenServer, and before that XenSource's XenEnterprise). Alternatively, Xen is distributed as an optional configuration of many standard operating systems. Xen is available for and distributed with: Alpine Linux offers a minimal dom0 system (Busybox, UClibc) that can be run from removable media, like USB sticks. Arch Linux provides the necessary packages with detailed setup instructions on their Wiki. Debian Linux (since version 4.0 "etch") and many of its derivatives; FreeBSD 11 includes experimental host support. Gentoo has the necessary packages available to support Xen, along with instructions on their Wiki. Mageia (since version 4); NetBSD can function as domU and dom0. OpenSolaris-based distributions can function as dom0 and domU from Nevada build 75 onwards. openSUSE 10.x to 12.x: only 64-bit hosts are supported since 12.1; Qubes OS uses Xen to isolate applications for a more secure desktop. SUSE Linux Enterprise Server (since version 10); Solaris (since 2013 with Oracle VM Server for x86, before with Sun xVM); Ubuntu (since 12.04 "Precise Pangolin"; also 8.04 "Hardy Heron", but no dom0-capable kernel in 8.10 "Intrepid Ibex" until 12.04.) Guests Guest systems can run fully virtualized (which requires hardware support), paravirtualized (which requires a modified guest operating system), or fully virtualized with paravirtualized drivers (PVHVM). Most operating systems which can run on PCs can run as a Xen HVM guest. The following systems can operate as paravirtualized Xen guests: Linux FreeBSD in 32-bit, or 64-bit through PVHVM; OpenBSD, through PVHVM; NetBSD MINIX GNU Hurd (gnumach-1-branch-Xen-branch) Plan 9 from Bell Labs Xen version 3.0 introduced the capability to run Microsoft Windows as a guest operating system unmodified if the host machine's processor supports hardware virtualization provided by Intel VT-x (formerly codenamed Vanderpool) or AMD-V (formerly codenamed Pacifica). During the development of Xen 1.x, Microsoft Research, along with the University of Cambridge Operating System group, developed a port of Windows XP to Xen — made possible by Microsoft's Academic Licensing Program. The terms of this license do not allow the publication of this port, although documentation of the experience appears in the original Xen SOSP paper. James Harper and the Xen open-source community have started developing free software paravirtualization drivers for Windows. These provide front-end drivers for the Xen block and network devices and allow much higher disk and network performance for Windows systems running in HVM mode. Without these drivers all disk and network traffic has to be processed through QEMU-DM. Subsequently, Citrix has released under a BSD license (and continues to maintain) PV drivers for Windows. Management Third-party developers have built a number of tools (known as Xen Management Consoles) to facilitate the common tasks of administering a Xen host, such as configuring, starting, monitoring and stopping of Xen guests. Examples include: The OpenNebula cloud management toolkit On openSUSE YaST and virt-man offer graphical VM management OpenStack natively supports Xen as a Hypervisor/Compute target Apache CloudStack also supports Xen as a Hypervisor Novell's PlateSpin Orchestrate also manages Xen virtual machines for Xen shipping in SUSE Linux Enterprise Server. Commercial versions XCP-ng (Open Source, within the Linux Foundation and Xen Project, originally a fork of XenServer) Citrix Hypervisor (formerly XenServer until 2019) Huawei FusionSphere Oracle VM Server for x86 Thinsy Corporation Virtual Iron (discontinued by Oracle) Crucible (hypervisor) by Star Lab Corp. The Xen hypervisor is covered by the GNU General Public Licence, so all of these versions contain a core of free software with source code. However, many of them contain proprietary additions. See also CloudStack Kernel-based Virtual Machine (KVM) OpenStack Virtual disk image tboot, a TXT-based integrity system for the Linux kernel and Xen hypervisor VMware ESX Qubes OS References Further reading Paul Venezia (April 13, 2011) Virtualization shoot-out: Citrix, Microsoft, Red Hat, and VMware. The leading server virtualization contenders tackle InfoWorld's ultimate virtualization challenge, InfoWorld External links 2003 software Citrix Systems Cross-platform free software Free virtualization software Linux Foundation University of Cambridge Computer Laboratory Virtualization-related software for Linux

Operating System (OS)

RIOT (operating system) RIOT is a small operating system for networked, memory-constrained systems with a focus on low-power wireless Internet of things (IoT) devices. It is open-source software, released under the GNU Lesser General Public License (LGPL). Background It was initially developed by Free University of Berlin (FU Berlin), French Institute for Research in Computer Science and Automation (INRIA) and the Hamburg University of Applied Sciences (HAW Hamburg). RIOT's kernel is mostly inherited from FireKernel, which was originally developed for sensor networks. Technical aspects RIOT is based on a microkernel architecture. In contrast to other operating systems with similarly low memory use (such as TinyOS or Contiki), RIOT allows application software programming with the programming languages C and C++, and Rust, also by an experimental application programming interface (API). It has full multithreading and real-time abilities. Secure Sockets Layer (SSL) and successor Transport Layer Security (TLS) are supported by popular libraries such as wolfSSL. RIOT runs on processors of 8 bits (such as AVR Atmega), 16 bits (such as TI MSP430), and 32 bits (such as ARM Cortex). A native port also enables RIOT to run as a Linux or macOS process, enabling use of standard developing and debugging tools such as GNU Compiler Collection (GCC), GNU Debugger, Valgrind, Wireshark, etc. RIOT is partly Portable Operating System Interface (POSIX) compliant. RIOT provides multiple network stacks, including IPv6, 6LoWPAN, or content centric networking and standard protocols such as RPL, User Datagram Protocol (UDP), Transmission Control Protocol (TCP), and CoAP. Source code RIOT source code is available on GitHub, and developed by an international community of open source developers. See also Contiki TinyOS FreeRTOS Nano-RK Zephyr Comparison of real-time operating systems References External links ARM operating systems Embedded operating systems Free software operating systems Internet of things Microkernels Microkernel-based operating systems MIPS operating systems Real-time operating systems

Operating System (OS)

Google File System Google File System (GFS or GoogleFS, not to be confused with the GFS Linux file system) is a proprietary distributed file system developed by Google to provide efficient, reliable access to data using large clusters of commodity hardware. The last version of Google File System codenamed Colossus was released in 2010. Design GFS is enhanced for Google's core data storage and usage needs (primarily the search engine), which can generate enormous amounts of data that must be retained; Google File System grew out of an earlier Google effort, "BigFiles", developed by Larry Page and Sergey Brin in the early days of Google, while it was still located in Stanford. Files are divided into fixed-size chunks of 64 megabytes, similar to clusters or sectors in regular file systems, which are only extremely rarely overwritten, or shrunk; files are usually appended to or read. It is also designed and optimized to run on Google's computing clusters, dense nodes which consist of cheap "commodity" computers, which means precautions must be taken against the high failure rate of individual nodes and the subsequent data loss. Other design decisions select for high data throughputs, even when it comes at the cost of latency. A GFS cluster consists of multiple nodes. These nodes are divided into two types: one Master node and multiple Chunkservers. Each file is divided into fixed-size chunks. Chunkservers store these chunks. Each chunk is assigned a globally unique 64-bit label by the master node at the time of creation, and logical mappings of files to constituent chunks are maintained. Each chunk is replicated several times throughout the network. At default, it is replicated three times, but this is configurable. Files which are in high demand may have a higher replication factor, while files for which the application client uses strict storage optimizations may be replicated less than three times - in order to cope with quick garbage cleaning policies. The Master server does not usually store the actual chunks, but rather all the metadata associated with the chunks, such as the tables mapping the 64-bit labels to chunk locations and the files they make up (mapping from files to chunks), the locations of the copies of the chunks, what processes are reading or writing to a particular chunk, or taking a "snapshot" of the chunk pursuant to replicate it (usually at the instigation of the Master server, when, due to node failures, the number of copies of a chunk has fallen beneath the set number). All this metadata is kept current by the Master server periodically receiving updates from each chunk server ("Heart-beat messages"). Permissions for modifications are handled by a system of time-limited, expiring "leases", where the Master server grants permission to a process for a finite period of time during which no other process will be granted permission by the Master server to modify the chunk. The modifying chunkserver, which is always the primary chunk holder, then propagates the changes to the chunkservers with the backup copies. The changes are not saved until all chunkservers acknowledge, thus guaranteeing the completion and atomicity of the operation. Programs access the chunks by first querying the Master server for the locations of the desired chunks; if the chunks are not being operated on (i.e. no outstanding leases exist), the Master replies with the locations, and the program then contacts and receives the data from the chunkserver directly (similar to Kazaa and its supernodes). Unlike most other file systems, GFS is not implemented in the kernel of an operating system, but is instead provided as a userspace library. Interface The Google File System does not provide a POSIX interface. Files are organized hierarchically in directories and identified by pathnames. The file operations such as create, delete, open, close, read, write are supported. It supports Record Append which allows multiple clients to append data to the same file concurrently and atomicity is guaranteed. Performance Deciding from benchmarking results, when used with relatively small number of servers (15), the file system achieves reading performance comparable to that of a single disk (80–100 MB/s), but has a reduced write performance (30 MB/s), and is relatively slow (5 MB/s) in appending data to existing files. The authors present no results on random seek time. As the master node is not directly involved in data reading (the data are passed from the chunk server directly to the reading client), the read rate increases significantly with the number of chunk servers, achieving 583 MB/s for 342 nodes. Aggregating multiple servers also allows big capacity, while it is somewhat reduced by storing data in three independent locations (to provide redundancy). See also Bigtable Cloud storage CloudStore Fossil, the native file system of Plan 9 GPFS IBM's General Parallel File System GFS2 Red Hat's Global Filesystem 2 Hadoop and its "Hadoop Distributed File System" (HDFS), an open source Java product similar to GFS List of Google products MapReduce MooseFS LizardFS References Bibliography External links . . Distributed file systems supported by the Linux kernel File System Parallel computing Distributed file systems

Operating System (OS)

VM/386 VM/386 is a multitasking operating system or 'control program' that took early advantage of the capabilities of Intel's 386 processor. By utilizing Virtual 8086 mode, users were able to run their existing text-based and graphical DOS software in safely separate environments. The system offered a high degree of control, with the ability to set memory limits, CPU usage and scheduling parameters, device assignments, and interrupt priorities through a virtual machine manager menu. Unique CONFIG.SYS and AUTOEXEC.BAT files could be configured for each application, and even different DOS versions. In 1991 the vendor announced intentions to support DPMI 1.0 in VM/386. Overview VM/386 had initially been developed by Softguard Systems, a producer of copy-protection software, with plans to include features like non-DOS system support, but financial constraints forced its sale to Intelligent Graphics Corporation (IGC), which launched the product in 1987. It won a PC Magazine award for technical excellence in 1988. The company also introduced a multi-user version, which allowed a number of serial terminals and even graphical systems to be connected to a single 386 computer. Current versions of the software have built on the multi-user support, and can handle tens of users in a networked environment with Windows 3.11 support, access controls, virtual memory and device sharing, among other features. A version of the software designed to cooperate with Unix was bundled with Everex Systems workstations. The system now sees use mainly in vertical applications like point-of-sale systems, where its ability to run reliably on cheap, reliable hardware outweigh any gains from newer operating systems that are more complex and less reliable. Early competition included DESQview 386, Sunny Hill Software's Omniview, StarPath Systems' Vmos/3, and Windows/386 2.01. As the target market shifted away from single-user systems to multiple-user setups with many serial terminals it began to compete more directly with the likes of Multiuser DOS and PC-MOS/386. See also Virtual DOS machine Multiuser DOS Federation References External links VM/386 as the operating system in a nuclear waste processing facility DOS software Proprietary operating systems

Operating System (OS)

Barrelfish (operating system) Barrelfish is an experimental computer operating system built by ETH Zurich with the assistance of Microsoft Research in Cambridge. It is an experimental operating system designed from the ground up for scalability for computers built with multi-core processors with the goal of reducing the compounding decrease in benefit as more CPUs are used in a computer via putting low level hardware information in a database, removing the necessity for driver software. The partners released the first snapshot of the OS on September 15, 2009 with a second being released in March, 2011. Excluding some third-party libraries, which are covered by various BSD-like open source licenses, Barrelfish is released under the MIT license. Snapshots are regularly released, the last one dating to March 23, 2020. While originally being developed in collaboration with Microsoft Research, it is now partly supported by Hewlett Packard Enterprise Labs, Huawei, Cisco, Oracle, and VMware. See also Singularity Midori References Further reading External links Barrelfish.org Project Paper - "The Multikernel: A new OS architecture for scalable multicore systems" (PDF file) Free software Distributed operating systems Microkernel-based operating systems Microkernels Microsoft free software Microsoft operating systems Microsoft Research Software using the MIT license 2009 software

Operating System (OS)

AmigaOne AmigaOne is a series of computers intended to run AmigaOS 4 developed by Hyperion Entertainment, as a successor to the Amiga series by Commodore International. Earlier models were produced by Eyetech, and were based on the Teron series of PowerPC POP mainboards. In September 2009, Hyperion Entertainment secured an exclusive licence for the AmigaOne name and subsequently new AmigaOne computers were released by A-Eon Technology and Acube Systems. History AmigaOne by Eyetech (2000–05) Originally in 2000, AmigaOne was the name of a project for new computer hardware to run the Amiga Digital Environment (DE), later plans replaced by AmigaOS 4. Initially it was managed by Eyetech and designed by the German company Escena GmbH. The AmigaOne motherboard was to be available in two models, the AmigaOne-1200 and the AmigaOne-4000 as expansions for the Amiga 1200 and Amiga 4000 computers. This would probably not have been actually possible. This AmigaOne project was cancelled in the design stage in 2001, mostly due to the inability to find or design a suitable northbridge chip. Eyetech, who at this point had invested funds into the project, was forced instead to license the Teron CX board from Mai to form the basis of the new AmigaONE computer range. The first fruit of this partnership with Mai, AmigaOne SE, was announced with a connector for an optionally attached Amiga 1200, in order to use the old custom chips of an Amiga for backwards compatibility. However, no such solution was ever introduced. The main difference between the ATX-format AmigaOne SE and XE was that the AmigaOne SE had a soldered-on 600 MHz PowerPC 750CXe processor, whereas the AmigaOne XE used a CPU board attached to a MegArray connector on the motherboard. While the MegArray connector is physically similar to the Apple Power Mac G4 CPU daughtercard connector, it is not electrically compatible. There were G3 and G4 options with a maximum clock frequency of 800 MHz and 933 MHz. The G4 module originally used a Freescale 7451 processor which was later changed to a Freescale 7455, both without level 3 cache. The G4 CPU runs hotter and requires a better heatsink than that supplied on some machines. Consequently, the G4 was often supplied underclocked to run at 800 MHz. In 2007 Acube offered 1.267 GHz 7457. The Micro-A1 was announced in two configurations, under the Micro-A1 I (Industrial) and Micro-A1 C (Consumer) labels. Only the C configuration was produced. Both AmigaOneG3-XE and AmigaOneG4-XE has four 32-bit PCI-slots (3× 33 MHz, 1× 66 MHz) and one AGP-2x slot. The Micro-A1 has only one 32-bit PCI-slot and an integrated Radeon 7000 via AGP with dedicated 32 MB VRAM. AmigaOne (SE and XE) motherboards had several hardware issues including conflicts between the onboard IDE and Ethernet controllers, problems with USB device detection and initially no support for the on-board AC97 audio. Due to the mistaken belief that the on-board AC97 audio could not be supported, the AC97 codec was removed from later builds of the motherboard. The technical issues preventing AC97 audio support were later resolved. When the AmigaOne boards first became available, AmigaOS 4 was not ready: they were supplied with various Linux distributions. From April 2004 onwards, boards were shipped for developers with a pre-release version of OS4. The Final Update of OS4.0 was released in December 2006, for AmigaOne computers only, with the PowerUP version being released in December 2007. AmigaOS 4.1 for AmigaOne was released in September 2008. MAI Logic Inc. went bankrupt, and consequently the supply of Eyetech AmigaOnes dried up. Eyetech Group Ltd retired from the market in 2005, selling their remaining Amiga business to Amiga Kit. AmigaOne by Hyperion Entertainment (2009–present) In September 2009, as part of the resolution of a dispute over ownership of AmigaOS Hyperion was granted (among other provisions of the Settlement Agreement with Amiga, Inc.) an exclusive licence for the AmigaOne (or Amiga One) name. This Settlement Agreement thus created a legal basis for a new generation of AmigaOne computers. In February 2010, a new Belgian company A-Eon Technology CVBA, in co-operation with Hyperion Entertainment, officially announced a new AmigaOne model, the AmigaOne X1000, first presented at the Vintage Computer festival at Bletchley Park in June 2010. The project was delayed but the new platform was launched in 2012 with AmigaOS 4.1.5. In September 2011, Acube Systems introduced the AmigaOne 500 based on a Sam460ex mainboard. In October 2011, Hyperion Entertainment announced that it was launching an AmigaOne netbook in mid-2012, but it was announced at Amiwest 2013 that the netbook project had been cancelled. Also at Amiwest 2013, A-Eon Technology Ltd, a British computer company, announced three new AmigaOne motherboards, with the project named Cyrus. A-Eon had a list of proposed names which could be voted for and in January 2014 A-Eon Technology announced names for new models as AmigaOne X5000/20, AmigaOne X5000/40 and AmigaOne X3500. The new motherboards were aimed as replacements for the AmigaOne X1000. The AmigaOne X5000/20 was released in October 2016 and - unlike the X1000 - sold via various distributors. ArsTechnica review of the AmigaOne X5000 commended its compatibility with old Amiga applications and games, but criticised the very high price and lack of new software. Lastly, A-Eon Technology Ltd announced at Amiwest 2013 that A-Eon had signed a 1.2 million-dollar investment contract with Ultra Varisys for the ongoing design, development and manufacture of PowerPC hardware for its AmigaOne line of desktop computers. In January 2015, Acube Systems started selling AmigaOne 500 computers based on the Sam460cr motherboard, a cost reduced version of original Sam460ex. Features that were removed included the Silicon Motion SM502 embedded MoC and 1× SATA2 port. In autumn 2015, A-Eon Technology Ltd announced a new motherboard with the project development name Tabor based on a P1022 1.2 GHz SoC. The motherboard design is a microATX form factor with single PCIe slot and SODIMM memory slots. The full system is to be designated as the AmigaOne A1222. Models and variants Operating systems Linux for PowerPC. AmigaOS versions 4.0, 4.1. MorphOS support for AmigaOne 500 / SAM460 was announced in 2012 and introduced with MorphOS 3.8. Support for X5000 was introduced with MorphOS 3.10. FreeBSD. Other AmigaOS4 compatible models The Sam440 mainboard (complete with AMCC PowerPC 440EP SoC) is an embedded motherboard launched by Acube Systems in September 2007. AmigaOS 4 was released for the Sam440 in October 2008. The Sam460ex mainboard (complete with AMCC 460ex SoC, PowerPC 440 core) is an embedded motherboard launched by Acube Systems in April 2010. AmigaOS 4 was released for the Sam460ex in January 2011. A cost reduced version, the Sam460cr, was released with AmigaOS 4.1 Final Edition on January 8, 2015. The Pegasos II mainboard (complete with PPC G3 and G4 CPU) is a MicroATX motherboard launched by Genesi and discontinued in 2006. AmigaOS 4 was released for the Pegasos II in January 2009. See also Amiga models and variants Sam440 Sam460ex Pegasos AmigaOS MorphOS AROS Commodore International Commodore USA References External links Eyetech and Mai Logic - Mai Logic Incorporated And Eyetech Group Limited Partner to Capture New Amiga Territory The Register - Amiga returns with AmigaOne PPC hardware Eyetech - Archived page containing AmigaOne update and information on the AmigaOne partnership between Eyetech, Hyperion Entertainment and Amiga Inc. Amiga Inc - Amiga status announcement Amiga computers PowerPC mainboards AmigaOS

Operating System (OS)

Linux malware Linux malware includes viruses, Trojans, worms and other types of malware that affect the Linux family of operating systems. Linux, Unix and other Unix-like computer operating systems are generally regarded as very well-protected against, but not immune to, computer viruses. There has not been a single widespread Linux virus or malware infection of the type that is common on Microsoft Windows; this is attributable generally to the malware's lack of root access and fast updates to most Linux vulnerabilities. Linux vulnerability Like Unix systems, Linux implements a multi-user environment where users are granted specific privileges and there is some form of access control implemented. To gain control over a Linux system or to cause any serious consequences to the system itself, the malware would have to gain root access to the system. In the past, it has been suggested that Linux had so little malware because its low market share made it a less profitable target. Rick Moen, an experienced Linux system administrator, counters that: In 2008 the quantity of malware targeting Linux was noted as increasing. Shane Coursen, a senior technical consultant with Kaspersky Lab, said at the time, "The growth in Linux malware is simply due to its increasing popularity, particularly as a desktop operating system ... The use of an operating system is directly correlated to the interest by the malware writers to develop malware for that OS." Tom Ferris, a researcher with Security Protocols, commented on one of Kaspersky's reports, stating, "In people's minds, if it's non-Windows, it's secure, and that's not the case. They think nobody writes malware for Linux or Mac OS X. But that's not necessarily true." Some Linux users do run Linux-based anti-virus software to scan insecure documents and email which comes from or is going to Windows users. SecurityFocus's Scott Granneman stated: Because they are predominantly used on mail servers which may send mail to computers running other operating systems, Linux virus scanners generally use definitions for, and scan for, all known viruses for all computer platforms. For example, the open source ClamAV "Detects ... viruses, worms and trojans, including Microsoft Office macro viruses, mobile malware, and other threats." Viruses and trojan horses The viruses listed below pose a potential, although minimal, threat to Linux systems. If an infected binary containing one of the viruses were run, the system would be temporarily infected, as the Linux kernel is memory resident and read-only. Any infection level would depend on which user with what privileges ran the binary. A binary run under the root account would be able to infect the entire system. Privilege escalation vulnerabilities may permit malware running under a limited account to infect the entire system. It is worth noting that this is true for any malicious program that is run without special steps taken to limit its privileges. It is trivial to add a code snippet to any program that a user may download and let this additional code download a modified login server, an open mail relay, or similar program, and make this additional component run any time the user logs in. No special malware writing skills are needed for this. Special skill may be needed for tricking the user to run the (trojan) program in the first place. The use of software repositories significantly reduces any threat of installation of malware, as the software repositories are checked by maintainers, who try to ensure that their repository is malware-free. Subsequently, to ensure safe distribution of the software, checksums are made available. These make it possible to reveal modified versions that may have been introduced by e.g. hijacking of communications using a man-in-the-middle attack or via a redirection attack such as ARP or DNS poisoning. Careful use of these digital signatures provides an additional line of defense, which limits the scope of attacks to include only the original authors, package and release maintainers and possibly others with suitable administrative access, depending on how the keys and checksums are handled. Reproducible builds can ensure that digitally signed source code has been reliably transformed into a binary application. Worms and targeted attacks The classical threat to Unix-like systems are vulnerabilities in network daemons, such as SSH and web servers. These can be used by worms or for attacks against specific targets. As servers are patched quite quickly when a vulnerability is found, there have been only a few widespread worms of this kind. As specific targets can be attacked through a vulnerability that is not publicly known there is no guarantee that a certain installation is secure. Also servers without such vulnerabilities can be successfully attacked through weak passwords. Web scripts Linux servers may also be used by malware without any attack against the system itself, where e.g. web content and scripts are insufficiently restricted or checked and used by malware to attack visitors. Some attacks use complicated malware to attack Linux servers, but when most get full root access then hackers are able to attack by modifying anything like replacing binaries or injecting modules. This may allow the redirection of users to different content on the web. Typically, a CGI script meant for leaving comments, could, by mistake, allow inclusion of code exploiting vulnerabilities in the web browser. Buffer overruns Older Linux distributions were relatively sensitive to buffer overflow attacks: if the program did not care about the size of the buffer itself, the kernel provided only limited protection, allowing an attacker to execute arbitrary code under the rights of the vulnerable application under attack. Programs that gain root access even when launched by a non-root user (via the setuid bit) were particularly attractive to attack. However, as of 2009 most of the kernels include address space layout randomization (ASLR), enhanced memory protection and other extensions making such attacks much more difficult to arrange. Cross-platform viruses An area of concern identified in 2007 is that of cross-platform viruses, driven by the popularity of cross-platform applications. This was brought to the forefront of malware awareness by the distribution of an OpenOffice.org virus called Badbunny. Stuart Smith of Symantec wrote the following: What makes this virus worth mentioning is that it illustrates how easily scripting platforms, extensibility, plug-ins, ActiveX, etc, can be abused. All too often, this is forgotten in the pursuit to match features with another vendor... The ability for malware to survive in a cross-platform, cross-application environment has particular relevance as more and more malware is pushed out via Web sites. How long until someone uses something like this to drop a JavaScript infecter on a Web server, regardless of platform? Social engineering As is the case with any operating system, Linux is vulnerable to malware that tricks the user into installing it through social engineering. In December 2009 a malicious waterfall screensaver that contained a script that used the infected Linux PC in denial-of-service attacks was discovered. Anti-virus applications There are a number of anti-virus applications available which will run under the Linux operating system. Most of these applications are looking for exploits which could affect users of Microsoft Windows. For Microsoft Windows-specific threats These applications are useful for computers (typically, servers) which will pass on files to MS Windows users. They do not look for Linux-specific threats. For Linux-specific threats These applications look for actual threats to the Linux computers on which they are running. chkrootkit (free and open source software) ClamAV (free and open source software) Comodo (proprietary) Dr.Web (proprietary) ESET (proprietary) (detects OS X, Windows malware as well) Linux Malware Detect lynis (open source auditing) rkhunter (free and open source software) Samhain (free and open source software) Sophos (proprietary) (versions for UNIX and Windows too) Linux malware can also be detected (and analyzed) using memory forensics tools, such as: Forcepoint (proprietary) Volatility (free and open source software) Threats The following is a partial list of known Linux malware. However, few if any are in the wild, and most have been rendered obsolete by Linux updates or were never a threat. Known malware is not the only or even the most important threat: new malware or attacks directed to specific sites can use vulnerabilities previously unknown to the community or unused by malware. Botnets Mayhem – 32/64-bit Linux/FreeBSD multifunctional botnet Linux.Remaiten – a threat targeting the Internet of things. Mirai (malware) – a DDoS botnet spreads through telnet service and designed to infect Internet of Things (IoT). GafGyt/BASHLITE/Qbot – a DDoS botnet spreads through SSH and Telnet service weak passwords, firstly discovered during bash Shellshock vulnerability. LuaBot – a botnet coded with modules component in Lua programming language, cross-compiled in C wrapper with LibC, it aims for Internet of Things in ARM, MIPS and PPC architectures, with the usage to DDoS, spreads Mirai (malware) or selling proxy access to the cyber crime. Hydra, Aidra, LightAidra and NewAidra – another form of a powerful IRC botnet that infects Linux boxes. EnergyMech 2.8 overkill mod (Linux/Overkill) – a long last botnet designed to infect servers with its bot and operated through IRC protocol for the DDoS and spreading purpose. Ransomware Rootkits Snakso – a 64-bit Linux webserver rootkit Trojans Viruses Worms See also Botnet Comparison of computer viruses Computer virus Computer worm Dirty COW Ransomware Spyware Timeline of computer viruses and worms Trojan horse (computing) References External links Linuxvirus on the Official Ubuntu Documentation Linux Malware by platform

Operating System (OS)

WIMP (computing) In human–computer interaction, WIMP stands for "windows, icons, menus, pointer", denoting a style of interaction using these elements of the user interface. Other expansions are sometimes used, such as substituting "mouse" and "mice" for menus, or "pull-down menu" and "pointing" for pointer. Though the acronym has fallen into disuse, it has often been likened to the term graphical user interface (GUI). Any interface that uses graphics can be called a GUI, and WIMP systems derive from such systems. However, while all WIMP systems use graphics as a key element (the icon and pointer elements), and therefore are GUIs, the reverse is not true. Some GUIs are not based in windows, icons, menus, and pointers. For example, most mobile phones represent actions as icons and menus, but often do not rely on a conventional pointer or containerized windows to host program interactions. WIMP interaction was developed at Xerox PARC (see Xerox Alto, developed in 1973) and popularized with Apple's introduction of the Macintosh in 1984, which added the concepts of the "menu bar" and extended window management. The WIMP interface has the following components: A window runs a self-contained program, isolated from other programs that (if in a multi-program operating system) run at the same time in other windows. These individual program containers enable users to move fluidly between different windows. The window manager software is typically designed such that it is clear which window is currently active. Design principles of spacing, grouping, and simplicity help the user maintain focus when working between more than one window. An icon acts as a shortcut to an action the computer performs (e.g., execute a program or task). Text labels can be used alongside icons to help identification for small icon sets. A menu is a text or icon-based selection system that selects and executes programs or tasks. Menus may change depending on context in which they are accessed. The pointer is an onscreen symbol that represents movement of a physical device that the user controls to select icons, data elements, etc. This style of system improves human–computer interaction (HCI) by emulating real-world interactions and providing greater ease of use for non-technical people. Because programs contained by a WIMP interface subsequently rely on the same core input methods, the interactions throughout the system are standardized. This consistency allows users' skills carry from one application to another. Criticism Some human–computer interaction researchers consider WIMP to be ill-suited for multiple applications, especially those requiring precise human input or more than three dimensions of input. Drawing and writing are example of these limitations; a traditional pointer is limited by two dimensions, and consequently doesn't account for the pressure applied when using a physical writing utility. Pressure-sensitive graphics tablets are often used to overcome this limitation. Another issue with WIMP-style user interfaces is that many implementations put users with disabilities at a disadvantage. For example, visually impaired users may have difficulty using applications when alternative text-based interfaces are not made available. People with motor impairments, such as Parkinson's disease, may not be able to navigate devices precisely using the traditional mouse pointer for input. To overcome these barriers, researchers continue to explore ways to make modern computer systems more accessible. Recent developments in artificial intelligence, specifically machine learning, have opened new doors for accessibility in technology, or assistive technology. Moving past the WIMP interface Multiple studies have explored the possibilities of moving past the WIMP interface, such as using reality-based interaction, making the interface "three-dimensional" by adding visual depth through the use of monocular cues, and even combining depth with physics. The latter resulted in the development of BumpTop desktop and its acquisition and release by Google. See also Desktop metaphor History of the graphical user interface Natural user interface Touch user interface References Bibliography Alistair D. N. Edwards: The design of auditory interfaces for visually disabled users. In: Proceedings of ACM Conference on Human Factors in Computing Systems (CHI), 1988, pp. 83–88, http://doi.acm.org/10.1145/57167.57180 Mark Green, Robert Jacob, SIGGRAPH: '90 Workshop report: software architectures and metaphors for non-WIMP user interfaces. In: ACM SIGGRAPH Computer Graphics, 25(3) (July 1991), pp. 229–235, http://doi.acm.org/10.1145/126640.126677 Ashley George Taylor: WIMP Interfaces (winter 1997) https://web.archive.org/web/20060719123329/http://www-static.cc.gatech.edu/classes/cs6751_97_winter/Topics/dialog-wimp/ External links ISO 9241-11:2018: Ergonomics of human-system interaction. Part 11: Usability: Definitions and concepts, https://www.iso.org/standard/63500.html Graphical user interfaces User interface techniques Computing acronyms

Operating System (OS)

PC-File PC-File was a flat file database computer application most often run on DOS. It was one of the first of three widely popular software products sold via the marketing method that became known as shareware. It was originally written by Jim "Button" Knopf in late 1982, and he formed the company Buttonware to develop, market, and support it. The program was usually distributed for the cost of diskettes by local PC user groups. There was no copy protection and a manual was distributed as a file on the same diskettes as the program. It was extremely simple to use and extremely stable. It ran on just about any PC, while competing commercial products costing hundreds of dollars were often picky and full of bugs. Knopf originally wrote the software for his own use to manage a church mailing list, on an Apple II. Later, he ported it to CP/M, and then to DOS. Other people heard about it, and started requesting copies. Eventually, the cost of sending out update disks inspired Knopf to include a note requesting a small cash donation to offset the expenses. The response was overwhelming, and when his income from PC-File exceeded "ten times" what he was making from his job at IBM, he decided to turn Buttonware into a full-time business. After PC-File version 3.0, Buttonware released PC-File/R, which had limited "relational" capabilities. In 1987, PC-File+ was rewritten to use the popular dBASE III file format. PC-File for Windows v8 was published by Outlook Software / Ace Software (previously Good Software) in 1994. This version works on Windows 3.1, 95, 98, and XP, but uses the 8.3 file naming convention. PC File will not run on Windows 7 64 bit, even in the XP compatibility mode, but will run in 'XP Mode'. Reception In a 1984 review of databases, PC Magazine found that "quite a few ... rough edges" existed, but concluded that "on a performance/price basis, [PC-File III] may be the best money you'll ever spend". See also PC-Write Bob Wallace PC-Talk Andrew Fluegelman References External links Article about Jim "Button" Knopf, from Dr. Dobb's Journal Shareware

Operating System (OS)