History of macOS

Mac OS is the operating system used by Apple Macintosh computers. Here we examine Mac OS history, from beginnings to now.

Pre-System 6

 * System 1.0
 * System 1.1
 * System 2.0
 * System 3.0
 * System 3.1
 * System 3.2
 * System 3.3
 * System 4.0
 * System 4.1
 * System 4.2
 * System 4.3

All of these versions could only run one application at a time, though special application shells such as Switcher (discussed under MultiFinder) could get around this to some extent. System 3.0 introduced HFS (Hierarchical File System) which had real directories - previously the Finder created the illusion of folders on the flat file system.

The other significant change that System 4.x brought to the Mac was Colour QuickDraw, which debuted with the Macintosh II in 1986. This significantly altered the extent and design of the underlying graphics architecture (and its APIs), but it is a credit to Apple that most users, and perhaps more importantly existing code, were largely unaware of this.

System 5
System 5 added MultiFinder, an add-on replacement for the Finder which could run several programs at once. Time was given to the background applications only when the foreground (or "running") applications gave it up (cooperative multitasking), but in fact most of them did via a clever change on the OS's event handling. The other significant change that System 5 brought to the Mac was Color QuickDraw, which debuted with the Macintosh II. This significantly altered the extent and design of the underlying graphics architecture (and its APIs), but it is a credit to Apple that most users, and perhaps more importantly existing code, were largely unaware of this.

System 5 was also the first Macintosh operating system to be given a unified "Macintosh System Software" version number, as opposed to the numbers used for the System and Finder files.


 * System Software 5.0 (System 4.2, Finder 6.0, MultiFinder 1.0)
 * System Software 5.1 (System 4.3, Finder 6.0, MultiFinder 1.0)

System 6
System 6 added MultiFinder, an add-on replacement for the Finder which could run several programs at once. Time was given to the background applications only when the foreground (or "running") applications gave it up (cooperative multitasking), but in fact most of them did via a clever change on the OS's event handling. MultiFinder had been released with earlier systems, but the 6.x systems were the first to make it official and widely used.

System 6 consolidated the previous releases into a much more complete and stable operating system. It also moved the Mac to true 32-bit memory addressing - necessary with the ever increasing amounts of RAM available. Earlier systems used the lower 24 bits for addressing, and the upper 8 bits for flags. This was a neat solution on the earlier Macs with their very limited amounts of RAM, but became a liability later. Code that assumed the 24 + 8 bit addressing was "not 32-bit clean" in Apple's words, and developers were required to excise such assumptions from their code.


 * System 6.0 -- never released
 * System 6.0.1 -- release disputed
 * System 6.0.2
 * System 6.0.3
 * System 6.0.4
 * System 6.0.5
 * System 6.0.6 -- missing?
 * System 6.0.7
 * System 6.0.8
 * System 6.0.8L -- never officially released from Apple

System 7
System 7 was a major upgrade to the Mac OS, but the core of the OS remained the same as in prior versions. Instead the new 7.x OS's included a huge number of "high level" additions, considered by some observers to be less well thought out than they might have been.

Although the name was changed to 8.x and 9.x over its history, the OS remained basically the same internally.

Regular Systems

 * System 7
 * System 7.0.1
 * System 7.1
 * System 7.1.1 (System 7 Pro)
 * System 7.1.2
 * System 7.1.2P
 * System 7.1.3
 * System 7.5

Performa Systems

 * System 7.0P1
 * System 7.1P1
 * System 7.1P2
 * System 7.1P3
 * System 7.1P4
 * System 7.1P5
 * System 7.1P6

"Mac OS" designation

 * Mac OS 7.5.1
 * Mac OS 7.5.2
 * Mac OS 7.5.3
 * Mac OS 7.5.3L
 * Mac OS 7.5.3 Revision 2
 * Mac OS 7.5.3 Revision 2.1
 * Mac OS 7.5.3 Revision 2.2
 * Mac OS 7.5.4 -- never released
 * Mac OS 7.5.5
 * Mac OS 7.6
 * Mac OS 7.6.1
 * Mac OS 7.6.3 -- existance disputed

Mac OS 8
Mac OS 8.x was very much a stop-gap version which was brought out to try and keep the Mac OS moving forward during a very trying time for the platform. 8.0 added a number of features from the stillborn Copland project, while leaving the underlying operating system unchanged. The GUI was changed in appearance to a new greyscale look, and the ability to change the appearance (a.k.a "skins") was added with a new control panel. This was provided by a new "appearance" API layer within the OS, one of the few significant changes. Mac OS 8 also saw the introduction of an updated version of HFS, HFS+, which fixed many of the limitations of the earlier system - in fact it is still in use today on Mac OS X. There were some other interface changes such as separating network features from printing (the venerable, and rather odd Chooser was at last headed for retirement), and some improvements to application switching. However, in most significant respects, System 8 was not very different from System 7.x.


 * Mac OS 8
 * Mac OS 8.1
 * Mac OS 8.5
 * Mac OS 8.5.1
 * Mac OS 8.6

Mac OS 9
Mac OS 9.x was a steady evolution from Mac OS 8. In fact the only reason that the version got increased from 8 to 9 was to pave the way to the future OS X ("ten"), rather than leave a gap in the version numbers which might have discouraged some to make the eventual change to OS X. 9 also added some transitional technologies to help application developers adopt some OS X features sooner rather than later, again easing the transition. These included new APIs for the file system, and the bundling of the Carbon library that apps could link against instead of the traditional API libraries - apps that were adapted to do this can be run natively on OS X as well. Other changes were made in OS 9 to allow it to be booted in the "classic environment" within OS X. This is a compatibility layer in OS X (in fact an OS X application, known in developer circles as "the blue box") that runs a complete Mac OS 9 operating system, so allowing applications that have not been ported to Carbon to run on Mac OS X. This is reasonably seamless, though "classic" applications retain their original OS 8/9 appearance and do not gain the OS X "Aqua" appearance.


 * Mac OS 9.0
 * Mac OS 9.0.2
 * Mac OS 9.0.3
 * Mac OS 9.0.4
 * Mac OS 9.1
 * Mac OS 9.2
 * Mac OS 9.2.1
 * Mac OS 9.2.2

Mac OS X
See Mac OS X history.

Mac OS X is the first real replacement for the older Mac OS, based on the OPENSTEP Unix operating system from NeXT. In addition to the original OPENSTEP libraries, OS X adds the Carbon libraries to allow older programming paradigms from the System 7.x core to be run under OS X and gain many of the benefits of this modern OS core. The system also includes Classic, a complete emulator for running older Mac programs.


 * Mac OS X DP1 (Developer Preview 1)
 * Mac OS X DP2
 * Mac OS X DP3
 * Mac OS X DP4
 * Mac OS X Public Beta

Mac OS X 10.0 "Cheetah"

 * Mac OS X 10.0.0
 * Mac OS X 10.0.1
 * Mac OS X 10.0.2
 * Mac OS X 10.0.3
 * Mac OS X 10.0.4

Mac OS X 10.1 "Puma"

 * Mac OS X 10.1
 * Mac OS X 10.1.1
 * Mac OS X 10.1.2
 * Mac OS X 10.1.3
 * Mac OS X 10.1.4
 * Mac OS X 10.1.5

Mac OS X 10.2 "Jaguar"

 * Mac OS X 10.2
 * Mac OS X 10.2.1
 * Mac OS X 10.2.2
 * Mac OS X 10.2.3
 * Mac OS X 10.2.4
 * Mac OS X 10.2.5
 * Mac OS X 10.2.6
 * Mac OS X 10.2.7
 * Mac OS X 10.2.8

Mac OS X 10.3 "Panther"

 * Mac OS X 10.3
 * Mac OS X 10.3.1
 * Mac OS X 10.3.2
 * Mac OS X 10.3.3
 * Mac OS X 10.3.4
 * Mac OS X 10.3.5
 * Mac OS X 10.3.6
 * Mac OS X 10.3.7
 * Mac OS X 10.3.8
 * Mac OS X 10.3.9

Mac OS X 10.4 "Tiger"

 * Mac OS X 10.4