The system, rebranded 'Mac OS' in 1997, was pre-installed on every Macintosh until 2002 and offered on Macintosh clones for a short time in the 1990s. In 1984, Apple debuted the operating system that is now known as the 'Classic' Mac OS with its release of the original Macintosh System Software. Two major families of Mac operating systems were developed by Apple Inc. For the now classic OS, formerly named that way, see Classic Mac OS.
