A family of OperatingSystems developed by AppleCorporation for their AppleMacintosh.

It has two major branches, the old MacOS Classic family and the new MacOSX family.

MacOS Classic shares many overall design choices with the later MicrosoftWindows (prior to Win32.) It used CooperativeMultitasking and lacked ProtectedMemory, so any application could crash or freeze the entire system. It was initially written for the Motorola 680x0 CPU architecture, but System 7.5 was hacked to run on PowerPC. System 8 was supposed to be a full PowerPC rewrite, but the rewrite effort codenamed Copland was so late that eventually Apple cancelled it and bought NeXT instead. The NeXT engineers effectively rewrote NeXTStep, incorporating a few features from Copland (such as Carbon), and created MacOSX. It took so long that AppleCorporation might as well have just finished Copland. System 8.5 through 9 sport the familiar LookAndFeel.

Part of CategoryOperatingSystem