The system has a single user and task based on floppy disks and extremely limited RAM.
These limited changes mean that the original Macintosh system remained largely as it was when initially introduced. Its official system documentation, Inside Macintosh, initially shipped in three volumes, adding another to describe the changes introduced with the Mac Plus, and another for the Mac II and Mac SE. The development of the Macintosh system software up to System 6 followed a fairly smooth progression with the addition of new features and relatively small changes and upgrades. The Mac OS 7 series was current for a total of more than six years, as the longest-lived major version of classic Mac OS. The name 'Mac OS' debuted on System 7.5.1's boot screen, and the system was officially renamed since Mac OS 7.6 in 1997. It succeeded System 6 upon launch on May 13, 1991, and new features since then include virtual memory, personal file sharing, QuickTime, QuickDraw 3D, and an improved user interface.
System 7, codenamed 'Big Bang', and renamed Mac OS 7 since version 7.6, is the main operating system for Macintosh computers from Apple Computer.
