Mac OS
From Computer History Wiki
Mac OS (originally eventually named System Software; it actually had no official name when first introduced) was the original operating system for the Apple Macintosh, from 1984 to 2001 (from 'System 1' to 'Mac OS 9'). The name 'Macintosh System Software' was adopted in 1987, with 'System 5'. The system was re-named 'Mac OS' in 1996, beginning with version 7.6.
It was based on the operating system for the Apple Lisa.
