It was introduced on May 13, 1991, by Apple Computer It succeeded System 6, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997. System 7, codenamed 'Big Bang', and later (as of version 7.6) also known as Mac OS 7, is a graphical user interface-based operating system for Macintosh computers and is part of the classic Mac OS series of operating systems.
