The document summarizes the evolution of the Macintosh operating system from its inception in 1979 to the present day Mac OS X versions. It was created by Jef Raskin and Steve Jobs at Apple Inc. The original System 1.0 launched in 1984 and was followed by System 2.0 through System 9 and Mac OS X versions from 2001 onward including Cheetah, Puma, Jaguar, Panther, Tiger, Snow Leopard, Lion and Mountain Lion. References for further information are provided.