Mac OS X is a line of computer operating systems developed, marketed, and sold by Apple Inc, the latest of which is pre-loaded on all currently shipping Macintosh computers. Mac OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessors, Mac OS X is a Unix-like operating system built on technology that had been developed at NeXT through the second half of the 1980s until Apple purchased the company in early 1996 and receiving a UNIX 03 certification after its 10.5 version on Intel processors.
The first version released was Mac OS X Server 1.0 in 1999, and a desktop-oriented version, Mac OS X version 10.0 followed in March 2001. Since then, five more distinct "end-user" and "server" versions have been released, most recently Mac OS X v10.5 in October 2007. Releases of Mac OS X are named after big cats; for example, Mac OS X v10.5 is usually referred to by Apple and users as "Leopard".
The server edition, Mac OS X Server, is architecturally very similar to its desktop counterpart but includes workgroup management and administration software tools that provide simplified access to common network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and others. It is included with Apple's Xserve server hardware, but is designed to run on most of Apple's computer models.
Mac OS X is based on the Mach kernel and is derived from the Berkeley Software Distribution (BSD) and later, certain parts from FreeBSD's and NetBSD's implementation of Unix in Nextstep. Nextstep was the object-oriented operating system developed by Steve Jobs' company NeXT after he left Apple in 1985. While Jobs was away from Apple, Apple tried to create a "next-generation" OS through the Taligent, Copland and Gershwin projects, with little success.
Eventually, NeXT's OS—then called OPENSTEP—was selected to be the basis for Apple's next OS, and Apple purchased NeXT outright. Steve Jobs returned to Apple as interim CEO, and later became CEO again, 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 known as Rhapsody and was later renamed to Mac OS X.
With each new version, Mac OS X evolved away from a focus on backward compatibility with the earlier versions of Mac OS, toward an emphasis on "digital lifestyle" applications such as the iLife suite, enhanced business applications (iWork), and integrated home entertainment (the Front Row media center). Each version also included modifications to the general interface, such as the brushed metal appearance added in version 10.2, 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.
Mac 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 released this core as a free and open source operating system named Darwin). Over this core, Apple layered a number of components, including the Aqua interface and the Finder, to complete the GUI-based operating system which is Mac OS X.
Mac 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. Many aspects of Mac 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, 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's "Platinum" appearance had offered. Many users of the older versions of the operating system decried the new look as lacking professional polish. But, others found Aqua to be a bold and innovative step forward in a time when user interfaces were seen as "dull and boring". Despite the controversy, the look was different, third-party developers started producing skins for customizable applications for Mac 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 claims is derived from its copyrighted design.
Mac 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.
Mac OS X 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.
Since Mac OS X is POSIX compliant, many software packages written for the *BSDs or Linux can be recompiled to run on it. Projects such as Fink, MacPorts and pkgsrc provide pre-compiled or pre-formatted packages. Since version 10.3, Mac OS X has included X11.app, Apple's version of the X Window System graphical interface for Unix applications, as an optional component during installation. 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 Mac OS X look-and-feel and has fairly good integration with Mac OS X, also using the native Quartz rendering system. Earlier versions of Mac OS X (in which X11 has not been bundled) can also run X11 applications using XDarwin.
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".
A few early adopters experienced a surprise: Mac OS X was supported on Mac OS machines that came with a G3 or later processor from the factory—not machines with third-party processor cards. For example, a Power Mac 7300 whose CPU chip failed could be easily upgraded with a G3 processor on a "daughter card," which often cost nearly the same as an exact replacement of the original chip. The user could then go to the same store and buy the Mac OS X upgrade on CD-ROM. This is not guaranteed to work, however.
In April 2002, eWeek reported 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. These rumors subsided until late in May 2005, when various media outlets, such as the Wall Street Journal and CNET, reported 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 has 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 has 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. However, 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.
Software that is available only for PowerPC is supported with Rosetta, though applications may have to be rewritten to run properly on the newer OS X for Intel. Apple encourages developers to produce universal binaries with support for both PowerPC and x86. 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. Further, in order to continue booting from a PowerPC drive, it had to be reformatted. 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. While Intel Macs will be able to run PowerPC, x86, and universal binaries, PowerPC Macs will support only universal and PowerPC builds.
Support for the PowerPC platform remains in Mac OS X version 10.5. Such cross-platform capability already existed in Mac OS X's lineage, as said earlier; Openstep was ported to many architectures, including x86, and Darwin included support for both PowerPC and x86. Although Apple stated that Mac OS X would not run on Intel-based personal computers aside from its own, a hacked version of the OS compatible with conventional x86 hardware has been developed by the OSx86 community.
Mac OS X versions are named after big cats. Prior to its release, version 10.0 was code named "Cheetah" internally at Apple, and version 10.1 was code named internally as "Puma". After the immense buzz surrounding version 10.2, codenamed "Jaguar", Apple's product marketing began openly using the code names to promote the operating system. 10.3 was marketed as "Panther", and 10.4 as "Tiger". "Leopard" is the name for the current release, version 10.5. The forthcoming version 10.6 is named "Snow Leopard". "Panther", "Tiger" and "Leopard" are registered as trademarks of Apple, but "Cheetah", "Puma" and "Jaguar" have never been registered. Apple has also registered "Lynx" and "Cougar" as trademarks.
Computer retailer Tiger Direct sued Apple for its use of the name "Tiger". On May 16, 2005 a US federal court in the Southern District of Florida ruled that Apple's use does not infringe on Tiger Direct's trademark.
Apple released a "preview" version of its new operating system to the public on September 13, 2000 in order to gain feedback from users. It cost $29.95 and came with a t-shirt. The "PB" as it was known marked the first public availability of the Aqua interface and Apple made many changes to the UI based on customer feedback. Mac OS X Public Beta expired and ceased to function in Spring 2001.
On March 24, 2001, Apple released Mac OS X v10.0 (internally codenamed Cheetah). The initial version was slow, not feature complete, and had very few applications available at the time of its launch, mostly from independent developers. While many critics suggested that the operating system was not ready for mainstream adoption, they recognized the importance of its initial launch as a base on which to improve. Simply releasing Mac OS X was received by the Macintosh community as a great accomplishment, for attempts to completely overhaul the Mac OS had been underway since 1996, and delayed by countless setbacks. Following some bug fixes, kernel panics became much less frequent.
Later that year on September 25, 2001, Mac OS X v10.1 (internally codenamed Puma) was released. It had better performance and provided missing features, such as DVD playback. Apple released 10.1 as a free upgrade CD for 10.0 users, in addition to the US$129 boxed version for people running only Mac OS 9. It was discovered that the upgrade CDs were actually full install CDs that could be used with Mac OS 9 systems by removing a specific file; Apple later re-released the CDs in an actual stripped-down format that did not facilitate installation on such systems.
On January 7, 2002, Apple announced that Mac OS X was to be the default operating system for all Macintosh products by the end of that month.
On August 23, 2002, Apple followed up with Mac OS X version 10.2 "Jaguar", the first release to use its code name as part of the branding. It brought great performance enhancements, a sleeker look, and many powerful enhancements (over 150, according to Apple), including Quartz Extreme for compositing graphics directly on an ATI Radeon or Nvidia GeForce2 MX AGP-based video card with at least 16 MB of VRAM, a system-wide repository for contact information in the new Address Book, and an instant messaging client named iChat.
The Happy Mac which had appeared during the Mac OS startup sequence for almost 18 years was replaced with a large grey Apple logo with the introduction of Mac OS X v10.2.
Mac OS X version 10.3 "Panther" was released on October 24, 2003. In addition to providing much improved performance, it also incorporated the most extensive update yet to the user interface. Panther included as many or more new features as Jaguar had the year before, including an updated Finder, incorporating a brushed-metal interface, Fast User Switching, Exposé (Window manager), FileVault, Safari, iChat AV (which added video-conferencing features to iChat), improved Portable Document Format (PDF) rendering and much greater Microsoft Windows interoperability. But, support for some early G3 computers such as "beige" Power Macs and "WallStreet" PowerBooks was discontinued.
Mac OS X version 10.4 "Tiger" was released on April 29, 2005. Apple stated that Tiger contained more than 200 new features. As with Panther, certain older machines were no longer supported; Tiger requires a Mac with a built-in FireWire port. Among the new features, Tiger introduced Spotlight, Dashboard, Smart Folders, updated Mail program with Smart Mailboxes, QuickTime 7, Safari 2, Automator, VoiceOver, Core Image and Core Video. The initial release of the Apple TV used a modified version of Tiger with a different graphical interface and fewer applications and services.
On January 10, 2006, Apple released the first Intel-based Macs along with the 10.4.4 update to Tiger. This operating system functioned identically on the PowerPC-based Macs and the new Intel-based machines, with the exception of the Intel release dropping support for the Classic environment. Because the implementation of the OS is built separately for the two processors, in implementation the PowerPC version and Intel versions are two separate installers (one cannot use the PowerPC installer to install the OS onto an Intel-based Mac).
Mac OS X version 10.5 "Leopard" was released on October 26, 2007. It was called by Apple "the largest update of Mac OS X". It brought more than 300 new features. Leopard supports both PowerPC- and Intel x86-based Macintosh computers, however support for the G3 processor was dropped and the G4 processor required a minimum clock speed of 867 MHz. The single DVD works for all supported Macs (including 64-bit machines). New features include a new look, an updated Finder, Time Machine, Spaces, Boot Camp pre-installed, full support for 64-bit applications (including graphical applications), new features in Mail and iChat, and a number of new security features.
More recently, MacWorld's Dan Frakes called the procedure of repairing permissions vastly overused. He argues that Mac OS X typically handles permissions properly without user interference, and resetting permissions should be tried only when problems emerge.