– "System 1", released in 1984
Macintosh System Software
– released between 1985 and 1987
System Software 2, 3, and 4
– released in 1987
System Software 5
– released in 1988
System Software 6
– released in 1991
System 7 / Mac OS 7.6
– released in 1997
Mac OS 8
– final major version, released in 1999