Mac OS (Classic)

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This article is about the Mac OS prior to Mac OS X. You may be looking for information about the Classic Environment, the Mac OS 9 emulator in Mac OS X.

Mac OS (Classic) is a colloquial name for versions of Mac OS prior to 10 (Mac OS X).



Earlier versions of the System Software from 1984 to early 1987 were not titled as 'System Software'; the unified version names started with System Software 5 (System 4.2). However, despite the unified name, the Finder and the System versions are rarely in sync with each other.

System 1

The first version of Mac OS was bundled with Macs in early 1984. In May of that year, it was replaced by System 1.1 which featured improvements such as a speed increase while copying disks and bug fixes in graphical demos.

System 2

System 2 was introduced in April 1985, and featured a much improved Finder (which jumped from version 1.1g to 4.1).

System 3

Introduced with the Mac Plus in January 1986, System 3 introduced, among other things, the HFS (Hierarchical File System) which replaced the MFS (Macintosh File System). The new file system featured support for folders extending beyond the root level of a disk. With the Macintosh File System, there were two 'levels'-- the root level of the disk and folders inside that. Any folders beyond that were virtual folders, and stored in a data file that the computer read. HFS allowed for true nesting of folders. System 3 had several updates, Systems 3.1, 3.2 and 3.3.

System 4

System 4 was introduced in March 1987. It had no significant new features, but fixed a number of bugs in Systems 3.2 and 3.3.

System 5

In October 1987, System Software 5 was introduced, featuring MultiFinder and Color QuickDraw. It was the first version of Mac OS to have a unified System Software version (5.0) rather than separate versions for the System and Finder (System Software 5.0 included System 4.2 and Finder 6.1).

System 6 through 6.0.8

System 6 featured true 32 bit memory addressing. Additional versions, up to 6.0.8, were released over the next few years to support newer Macintosh models.

System 7 through 7.1.1

Released in May, 1991. New features included:

  • 32-bit operating system
  • Co-operative multitasking
  • Virtual memory support added
  • Quicktime introduced
  • AppleScript introduced

System 7.5 through 7.5.5

System 7.5 saw a confusing bombardment of updates to fix bugs and fix the bugs those bug fixes created!

  • System 7.5.1 was a minor update with some fixes.
  • System 7.5.2 included support for newer, PCI-based, PowerMacs and certain PowerBook models. Also included bug fixes present in 7.5.1.
  • System 7.5.3 was an update which could be applied to any previous version of System 7.5. It included some big changes to the OS as whole and introduced a few bugs on the way. Came pre-installed on several mac models.
  • System 7.5.5 released to fix the bugs introduced in 7.5.3. Not all machines supported this update, so users of some models had to stay with a buggy 7.5.3 or wait until the release of 7.6.
  • Can be found on Apple's old software page for free download

Mac OS 7.6 through 7.6.1

New features:

  • More PowerPC code in this release, indeed, before OS 8, this was the primary System Software to run on PowerPC based Macs.
  • Is not offered as a free download from Apple due to copyrights that Apple included within the System.
  • Is the first time Apple used the name "Mac OS", replacing the traditional "System" moniker.

Mac OS 8

New features:

  • Finder gained 'multithreading'. It was now possible to copy multiple files and open documents simultaneously.
  • The general appearance changed from black and white to 'Platinum' using various shades of grey to give a 3D/metallic view.
  • Spring loaded folders
  • This was the last system to support reading from the MFS. Creating MFS disks had been dropped in System 3, when MFS was replaced with HFS.

Mac OS 8.1

  • The last system to be compatible with the 68040 processor.
  • Introduced HFS+ as a new file system format that allowed for smaller file sizes and more files per drive. Today, we use a slightly modified version of HFS+ (HFS+ with Journaling) however the disks will still read in a OS 8.1 computer.

Mac OS 8.5 through 8.6

New features:

  • Sherlock application. Used for searching various internet services as well as local disks.
  • OS 8.6 brought numerous performance and stability benefits.

Mac OS 9 through 9.2.2

New features:

  • Support for 'iTools' (later renamed .Mac)
  • Automated Software Update function to keep your mac up to date.
  • Multiple user accounts


  • 9.1 or 9.22 (preferred) for use as classic support under Mac OS X
  • The last Classic OS.



Eric Rasmussen's .Mac homepage An excellent history of the mac system software before System 7.

Wikipedia's System 6 page.

Wikipedia's System 7 page.

Mac OS Versions

Classic (prior to Mac OS X) | Mac OS X (Pre-release) | Mac OS X 10.0 (Cheetah) | Mac OS X 10.1 (Puma) | Mac OS X 10.2 (Jaguar) | Mac OS X 10.3 (Panther) | Mac OS X 10.4 (Tiger) | Mac OS X 10.5 (Leopard) | Mac OS X 10.6 (Snow Leopard) | OS X 10.7 (Lion)