Mac OS X

**OS X** (pronounced /ˌoʊ ɛs ˈtɛn/;[12] originally **Mac OS X**) is a series of Unix-based graphical interface operating systems developed and marketed by Apple Inc. It is designed to run on Macintosh computers, having been

pre-installed on all Macs since 2002. It was the successor to Mac OS 9, released in 1999, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 1984. The first version released was Mac OS X Server 1.0 in 1999, and a desktop version, Mac OS X v10.0 "Cheetah" followed on March 24, 2001. Previous releases of OS X were named after big cats; for example, OS X v10.8 was referred to as "Mountain Lion". However, with the announcement of OS X Mavericks in June 2013, this was dropped in favor of Californian landmarks.[13] Within the market of desktop, laptop and home computers, and by web usage, OS X is the second most widely used OS after Windows.[14][15][16]

OS X, whose *X* is the Roman numeral for *10* and is a prominent part of its brand identity, is built on technologies developed at NeXT
 between the second half of the 1980s and Apple's purchase of the
company in late 1996. The 'X' is also used to emphasize the relatedness
between OS X and UNIX. UNIX 03 certification has been achieved for versions 10.5 for Intel CPUs,[3] and versions 10.6 through 10.10.[4][5][6][7][8] iOS, the mobile OS for the iPhone, iPod Touch,[17] iPad, and the 2nd and 3rd generation Apple TV,[18] shares the Unix-based Darwin core and many frameworks with OS X. An unnamed variant of v10.4 powers the first generation Apple TV.[19]
The first releases of Mac OS X from 1999 to 2006 can run only on the PowerPC based Macs of the period. After Apple announced it would shift to using Intel x86 CPUs from 2006 onwards, Tiger and Leopard were released in versions for Intel and PowerPC processors. Snow Leopard is the first version released only for Intel Macs. Since the release of Mac OS X 10.7 "Lion", OS X has dropped support for 32-bit Intel processors as well. It now runs exclusively on 64-bit Intel CPUs.

Apple offers an application suite for OS X called OS X Server, for use on servers. It includes tools to facilitate management of workgroups of OS X machines, and to provide network services. It is sold separately through the Mac App Store
 as a single item; it remained available until 2014 preinstalled on
dedicated server computers. Before the release of Mac OS X 10.7 "Lion", a
 separate edition of Mac OS X, called Mac OS X Server, with additional
tools bundled with the operating system was sold and was preinstalled on
 servers.

The latest version of OS X is 10.10 "Yosemite", which was released to the public on October 16, 2014.

Related

* Mac OS
* Copland
* NeXTSTEP
* Rhapsody
* Darwin

## History

Main article: History of OS X

The heritage of what would become OS X had originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, and then launched in 1989. The kernel of NeXTSTEP is based upon the Mach kernel, which was originally developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from select parts of BSD. Its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language.
Throughout the early 1990s, Apple had tried to create a "next-generation" OS through the Taligent, Copland and Gershwin projects, although these were eventually abandoned.[20] This led Apple to purchase NeXT in 1996, allowing NeXTSTEP, then called OPENSTEP, to serve as the basis for Apple's next generation OS.[21]
 This purchase also led to Steve Jobs returning to Apple as interim CEO,
 and later CEO, shepherding the transformation of the
programmer-friendly OPENSTEP into a system that would be adopted by
Apple's primary market of home users and creative professionals. The
project was first code named "Rhapsody" and then officially named "Mac OS X".[22]

Mac OS X was launched for PowerPC-based Macs. In 2006, the first Intel Macs had a specialized version of 10.4 "Tiger".[23] In 2007, 10.5 "Leopard" was the first to run on both PowerPC and Intel Macs with the use of Universal Binaries.[24] 10.6 "Snow Leopard" was the first version of OS X to drop support for PowerPC Macs.[25]

Mac OS X Server 1.x is incompatible with software designed for the original Mac OS and has no support for Apple's own IEEE 1394 (FireWire) interface. Mac OS X 10.x includes more backward compatibility through Classic and more functionality by introducing the Carbon API
 as well as FireWire support. As the operating system evolved, it moved
away from the legacy Mac OS to an emphasis on new "digital lifestyle"
applications such as the iLife suite, enhanced business applications (iWork), and integrated home entertainment (the Front Row media center).[26] Each version also included modifications to the general interface, such as the brushed metal
 appearance added in version 10.3, the non-pinstriped titlebar
appearance in version 10.4, and in 10.5 the removal of the previous
brushed metal styles in favor of the "Unified" gradient window style.[27][28]

In 2012, with the release of OS X 10.8, the "Mac" prefix was
officially dropped in all references to the operating system name within
 its web site.[29]

## Description

Box/Mac App Store artwork for OS X. Left to right: Cheetah/Puma (1), Jaguar (2), Panther (3), Tiger (4), Leopard (5), Snow Leopard (6), Lion (7), Mountain Lion (8), Mavericks (9), Yosemite (10).

OS X is the tenth major version of Apple's operating system for
Macintosh computers. Previous Macintosh operating systems were named
using Arabic numerals, e.g. Mac OS 8 and Mac OS 9. The letter *X* in OS X's name refers to the number *10*, a Roman numeral. It is therefore correctly pronounced "ten" /ˈtɛn/ in this context.[12][30] However, a common mispronunciation is "X" /ˈɛks/.[31]

OS X's core is a POSIX compliant operating system (OS) built on top of the XNU kernel, with standard Unix facilities available from the command line interface. Apple has released this family of software as a free and open source operating system named Darwin. On top of Darwin, Apple layered a number of components, including the Aqua interface and the Finder, to complete the GUI-based operating system which is OS X.[32]

OS X introduced a number of new capabilities to provide a more stable and reliable platform than its predecessor, Mac OS 9. For example, pre-emptive multitasking and memory protection improved the system's ability to run multiple applications simultaneously without them interrupting or corrupting each other.[33] Many aspects of OS X's architecture are derived from OPENSTEP, which was designed to be portable, to ease the transition from one platform to another. For example, NeXTSTEP was ported from the original 68k-based NeXT workstations to x86 and other architectures before NeXT was purchased by Apple,[34] and OPENSTEP was later ported to the PowerPC architecture as part of the Rhapsody project.

The most visible change was the Aqua theme. The use of soft edges, translucent colors, and pinstripes—similar to the hardware design of the first iMacs—brought more texture and color to the user interface when compared to what OS 9 and OS X Server 1.0's "Platinum" appearance had offered. According to John Siracusa, an editor of Ars Technica, the introduction of Aqua and its departure from the then conventional look "hit like a ton of bricks."[35] Bruce Tognazzini (who founded the original Apple Human Interface Group) said that the Aqua interface in Mac OS X v10.0 represented a step backwards in usability compared with the original Mac OS interface.[36][37] Third-party developers started producing skins
 for customizable applications and other operating systems which
mimicked the Aqua appearance. To some extent, Apple has used the
successful transition to this new design as leverage, at various times
threatening legal action against people who make or distribute software with an interface the company says is derived from its copyrighted design.[38]

The architecture of OS X incorporates a layered design.[39] The layered frameworks aid rapid development of applications by providing existing code for common tasks.[40]

OS X includes its own software development tools, most prominently an integrated development environment called Xcode. Xcode provides interfaces to compilers that support several programming languages including C, C++, Objective-C, and Java. For the Apple–Intel transition, it was modified so that developers could build their applications as a universal binary, which provides compatibility with both the Intel-based and PowerPC-based Macintosh lines.[41] First and third-party applications can be controlled programatically using the AppleScript framework, retained from classic Mac OS, or using the newer Automator application.[*citation needed*]

The Darwin sub-system in Mac OS X is in charge of managing the filesystem, which includes the Unix permissions layer. In 2003 and 2005, two *Macworld*
 editors expressed criticism of the permission scheme; Ted Landau called
 misconfigured permissions "the most common frustration" in Mac OS X,
while Rob Griffiths suggested that some users may even have to reset permissions every day, a process which can take up to 15 minutes.[42] More recently, another *Macworld* editor, Dan Frakes, called the procedure of repairing permissions vastly overused.[43]
 He argues that OS X typically handles permissions properly without user
 interference, and resetting permissions should just be tried when
problems emerge.[44]

Mac applications may be installed by the user from any source, or from the Mac App Store, a marketplace of software maintained by Apple. All App Store applications run within a 'sandbox',
 restricting their ability to communicate with other programs or modify
the core operating system. This provides increased user security but
restricts the features they can offer.

### Distribution and languages

See also: Usage share of operating systems

As of September 2011, OS X is the second-most-active general-purpose client operating system in use on the World Wide Web, (after Microsoft Windows), with an 8.45% usage share according to statistics compiled by W3Counter.[45] It is the most successful Unix-like desktop operating system on the web, estimated at over 5 times the usage of Linux (which has 1.5%).[45]
There are twenty-two "System Languages" available for the user at the
 moment of installation (the "system language" is the entire operating
system environment). As of Mac OS X Lion, the languages are Arabic,
Chinese (Simplified), Chinese (Traditional), Czech, Danish, Dutch,
English, Finnish, French, German, Hebrew, Hungarian, Italian, Japanese,
Korean, Norwegian, Polish, Portuguese (Brazilian), Portuguese
(European), Russian, Spanish, Swedish and Turkish. Input methods for
typing in dozens of scripts can be chosen independently of the system
language.[46]

## Compatibility

### Software

The APIs that OS X inherited from OpenStep
 are not backward compatible with earlier versions of Mac OS. These APIs
 were created as the result of a 1993 collaboration between NeXT Computer and Sun Microsystems and are now referred to by Apple as Cocoa.
 This heritage is highly visible for Cocoa developers, since the "NS"
prefix is ubiquitous in the framework, standing variously for **N**ext**s**tep or **N**eXT/**S**un.
 The official OpenStep API, published in September 1994, was the first
to split the API between Foundation and Application Kit and the first to
 use the "NS" prefix.[34]
 Apple's Rhapsody project would have required all new development to use
 these APIs, causing much outcry among existing Mac developers. All Mac
software that did not receive a complete rewrite to the new framework
would run in the equivalent of the Classic environment. To permit a smooth transition from Mac OS 9 to (Mac) OS X, the Carbon Application Programming Interface
 (API) was created. Applications written with Carbon can be executed
natively on both systems. Carbon was not included in the first product
sold as "Mac OS X": Mac OS X Server (now referred to as Mac OS X Server
1.x).[*citation needed*]

OS X also used to support the Java Platform
 as a "preferred software package"—in practice this means that
applications written in Java fit as neatly into the operating system as
possible while still being cross-platform compatible, and that graphical user interfaces written in Swing look almost exactly like native Cocoa interfaces. Traditionally, Cocoa programs have been mostly written in Objective-C,
 with Java as an alternative. However, on July 11, 2005, Apple announced
 that "features added to Cocoa in Mac OS X versions later than 10.4 will
 not be added to the Cocoa-Java programming interface."[47]

Since OS X is POSIX compliant, many software packages written for the \*BSDs, Linux, or other Unix-like systems can be recompiled to run on it. Projects such as Homebrew, Fink, MacPorts and pkgsrc provide pre-compiled or pre-formatted packages. From version 10.3 to version 10.7, OS X included X11.app, Apple's version of the X Window System graphical interface for Unix applications, as an optional component during installation.[48] Up to and including Mac OS X v10.4 (Tiger), Apple's implementation was based on the X11 Licensed XFree86 4.3 and X11R6.6. All bundled versions of X11
 feature a window manager which is similar to the OS X look-and-feel and
 has fairly good integration with Mac OS X, also using the native Quartz rendering system. Earlier versions of OS X (in which X11 has not been bundled) can also run X11 applications using XDarwin. With the introduction of version 10.5 Apple switched to the X.org variant of X11.[49] Version Mac OS X 10.7 "Lion" uses X.org Server version 1.10.x[50] Starting with OS X Mountain Lion, X11 is not bundled in OS X; instead, it has to be installed from, for example, the open source XQuartz project.[51]

### Hardware

For the early releases of Mac OS X, the standard hardware platform
supported was the full line of Macintosh computers (laptop, desktop, or
server) based on PowerPC G3, G4, and G5 processors. Later versions discontinued support for some older hardware; for example, Panther does not support "beige" G3s,[52] and Tiger does not support systems that pre-date Apple's introduction of integrated FireWire ports (the ports themselves are not a functional requirement). Mac OS X v10.5 "Leopard",
 introduced October 2007, has dropped support for all PowerPC G3
processors and for PowerPC G4 processors with clock rates below 867 MHz.
 Mac OS X v10.6 "Snow Leopard" supports Macs with Intel processors, not PowerPC. Mac OS X 10.7 "Lion" requires a Mac with an Intel Core 2 Duo or newer processor.[*citation needed*]

Tools such as XPostFacto
 and patches applied to the installation disc have been developed by
third parties to enable installation of newer versions of Mac OS X on
systems not officially supported by Apple. This includes a number of
pre-G3 Power Macintosh systems that can be made to run up to and
including Mac OS X 10.2 Jaguar, all G3-based Macs which can run up to
and including Tiger, and sub-867 MHz G4 Macs can run Leopard by removing
 the restriction from the installation DVD or entering a command in the
Mac's Open Firmware
 interface to tell the Leopard Installer that it has a clock rate of
867 MHz or greater. Except for features requiring specific hardware
(e.g. graphics acceleration, DVD writing), the operating system offers
the same functionality on all supported hardware.[*citation needed*]

PowerPC versions of Mac OS X prior to Leopard retain compatibility
with older Mac OS applications by providing an emulation environment
called Classic, which allows users to run Mac OS 9
 as a process within Mac OS X, so that most older applications run as
they would under the older operating system. Classic is not supported on
 Intel-based Macs or in Mac OS X v10.5 "Leopard", but users still
requiring Classic applications on Intel Macs can use the SheepShaver emulator to run Mac OS 9 on top of Leopard.[*citation needed*]

### PowerPC–Intel transition

Steve Jobs talks about the transition to Intel processors.

Main article: Apple's transition to Intel processors

In April 2002, eWeek announced a rumor that Apple had a version of Mac OS X code-named Marklar, which ran on Intel x86
 processors. The idea behind Marklar was to keep Mac OS X running on an
alternative platform should Apple become dissatisfied with the progress
of the PowerPC platform.[53] These rumors subsided until late in May 2005, when various media outlets, such as *The Wall Street Journal*[54] and CNET,[55] announced that Apple would unveil Marklar in the coming months.

On June 6, 2005, Steve Jobs confirmed these rumors when he announced in his keynote address at the annual Apple Worldwide Developers Conference that Apple would be making the transition from PowerPC to Intel
 processors over the following two years, and that Mac OS X would
support both platforms during the transition. Jobs also confirmed rumors
 that Apple had versions of Mac OS X running on Intel processors for
most of its developmental life. The last time that Apple switched CPU
families—from the Motorola 68K CPU to the IBM/Motorola
 PowerPC—Apple included a Motorola 68K emulator in the new OS that made
almost all 68K software work automatically on the new hardware. Apple
had supported the 68K emulator for 11 years, but stopped supporting it
during the transition to Intel CPUs. Included in the new OS for the
Intel-based Macs is Rosetta, a binary translation
 layer which enables software compiled for PowerPC Mac OS X to run on
Intel Mac OS X machines. Apple dropped support for Classic mode on the
new Intel Macs. Third party emulation software such as Mini vMac, Basilisk II and SheepShaver
 provides support for some early versions of Mac OS. A new version of
Xcode and the underlying command-line compilers support building universal binaries that will run on either architecture.[56]

PowerPC-only software is supported with Rosetta, though applications
may have to be rewritten to run properly on the newer OS X for Intel.
Apple initially encouraged developers to produce universal binaries with
 support for both PowerPC and x86.[57]
 There is a performance penalty when PowerPC binaries run on Intel Macs
through Rosetta. Moreover, some PowerPC software, such as kernel
extensions and System Preferences plugins, are not supported on Intel
Macs. Some PowerPC applications would not run on Intel OS X at all.
Plugins for Safari need to be compiled for the same platform as Safari,
so when Safari is running on Intel it requires plug-ins that have been
compiled as Intel-only or universal binaries, so PowerPC-only plug-ins
will not work.[58] While Intel Macs are able to run PowerPC, x86, and universal binaries; PowerPC Macs support only universal and PowerPC builds.[*citation needed*]

Support for the PowerPC platform was dropped after Mac OS X 10.5.
Such cross-platform capability already existed in Mac OS X's lineage;
OpenStep was ported to many architectures, including x86, and Darwin
included support for both PowerPC and x86. Apple stated that Mac OS X
would not run on Intel-based personal computers aside from its own, but a
 hacked version of the OS compatible with conventional x86 hardware was
developed by the OSx86 community.[59]

On June 8, 2009, Apple announced at its Worldwide Developers Conference that Snow Leopard (version 10.6) would drop support for PowerPC processors and be Intel-only.[60]
 However, Rosetta is still available in Snow Leopard; it is not
installed by default, but it is available on the installation DVD as an
installable add-on and is installed automatically via the Internet when
first attempting to run a PowerPC-based application.[*citation needed*]

On all versions from (and including) Lion, Rosetta is no longer available.[*citation needed*]