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

Table of contents
1 Pre-System 6
2 System 6
3 System 7
4 Mac OS 8
5 Mac OS 9
6 Mac OS X

Pre-System 6

  • System 1.0
  • System 2.0
  • System 3.0
  • System Tools 4.0 (System 3.2, Finder 5.3)
  • System Tools 5.0 (System 4.2, Finder 6.0)

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 1.0 and 2.0 were released with the Mac 128K and 512K respectively, and supported a flat filing system called MFS (Macintosh File System). 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. System 4.0 was introduced with the Mac Plus (adding SCSI support, AppleTalk, etc), and System 5.0 with the Mac SE and Macintosh II.

The other significant change that System 5.x brought to the Mac was Color 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 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 (Finder 6.1)
  • System 6.0.5
  • System 6.0.7 (buggy)
  • System 6.0.8 (added System 7 file & print sharing compatibility)

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.

  • System 7.0 (released in late 1991; integrated MultiFinder into the basic OS)
  • System 7.0.1 (introduced with LC II and Quadra series)
  • System 7• (System 7 Tuner)
  • System 7.1 (the unofficial developer slogan for this release was "System 7.1 Sucks Less")
  • System 7.1 Pro (combined with PowerTalk, Speech Manager & Macintalk, Thread Manager)
  • System 7.1.2 (first version for PowerMacs?)
  • System 7.2
  • System 7.5
  • System 7.5.1
  • System 7.5.3
  • System 7.5.5
  • Mac OS 7.6 (name changed because of the experimental clone program)

Mac OS 8

Mac OS 9

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 - codenamed Cheetah
  • Mac OS X 10.1 - codenamed Puma, major speedups
  • Mac OS X 10.2 - codenamed Jaguar, introduced many new features:
  • Mac OS X 10.3 - codenamed Panther, released in October 2003, Among the over 150 new features:
    • Updated Finder, incorporating a brushed-metal interface and fast-searching
    • Exposé, a new system to manipulate windows
    • Fast User Switching that allows a user to remain logged in while another user logs in
    • iChat AV video-conferencing software
    • Improved PDF Rendering to allow for extremely fast PDF viewing
    • Built-in faxing support
    • Much greater Microsoft Windows compatibility
    • FileVault: on the fly encryption and decryption of a user's home folder