Mac OS 7.0

System 7.0 (codenamed "Big Bang" and sometimes retroactively called Mac OS 7) was released in May 1991. It is a single-user graphical user interface-based operating system for Macintosh computers. It was introduced on May 13, 1991 by Apple Computer. It succeeded Mac System Software 6.x, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997. Features added with the System 7 release included virtual memory, personal file sharing, QuickTime, QuickDraw 3D, and an improved user interface.