Each successive release was nicknamed after a wild cat from Mac OS X 10.0 'Cheetah' until OS X 10.9 Mavericks, which officially dropped 'Mac' from the name and started using names of natural landmarks in California. Previous Macintosh system software releases became retroactively known as 'classic' Mac OS while transitioning to Mac OS X, which was based on NeXTSTEP, a more robust operating system derived from Unix. In December 1996, Apple Computer acquired NeXT, a startup by Apple co-founder Steve Jobs, for its software technology.
System 7.5 became known as Mac OS 7.5.1 during a software update in March 1995 and the name of the operating system was changed several times. Originally known simply as ' System' software, it shipped with the Macintosh 128K in January 1984 and became the first commercially successful operating system to use a purely graphical user interface. MacOS, an abbreviation of Macintosh Operating System, is Apple Inc.'s operating system for Apple Macintosh computers, and is closely related to iOS, Apple's mobile operating system for its iPhone and iPod Touch product lines.
