Mac OS

Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. Mac OS is credited with popularizing the graphical user interface. The original form of what Apple now calls OS X was the integral and unnamed system software first introduced in 1984 with the original Macintosh, and referred to simply as the System software.

Read more about Mac OS:  Concept, Versions, Star Trek, 68000 Emulation, PowerPC Emulation, Macintosh Clones, A/UX, MAE, MkLinux, Mac OS On Non Apple-labeled Computers