Classic Mac OS

The Classic Mac OS is a general term used to describe the Macintosh system software (Mac OS) before (and not including) Mac OS X.

Release history
Major releases of the classic Mac OS:
 * System 1, released January 24, 1984
 * System 2, released April 1985
 * System 3, released January 1986
 * System 4, released January 1987
 * System 5, released October 1987
 * System 6, released April 1988
 * System 7, released May 13, 1991
 * Mac OS 8, released July 26, 1997
 * Mac OS 9, released October 23, 1999