(Mac OS) Apple Computer, Inc.'s proprietary operating system for their Macintosh family of personal computers.

The part of the operating system that simulates the desktop is called "Finder." The multitasking version of Finder was called "MultiFinder" until multitasking was integrated into the core of the OS with the introduction of System 7.0 in 1990.

The Macintosh series provides a built-in graphics language, called "QuickDraw", which provides a standard for software developers.

Mac OS 8, scheduled for delivery in July 1997, contains a number of significant improvements, including new human-interface features, increased system stability and performance, a PowerPC processor-native Finder, tighter integration of Internet access through panel-based "assistants," Personal Web Sharing, and the ability to run Java applets and programs through Mac OS Run Time for Java.

Mac OS X ("X" for 10) is based on FreeBSD. Apple released the kernel of Mac OS X Server as "darwin", under an open source license.

See also Macintosh file system, Macintosh user interface.