Mac OS X

Mac OS X is a line of graphical operating systems developed, marketed, and sold by Apple Inc, the latest of which is pre-loaded on all currently shipping Macintosh computers. Mac OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessors, Mac OS X is a Unix-based operating system built on technology that had been developed at NeXT through the second half of the 1980s until Apple purchased the company in early 1997.

The first version released was Mac OS X Server 1.0 in 1999, and a desktop-oriented version, Mac OS X version 10.0 followed in March 2001. Since then, five more distinct "end-user" and "server" versions have been released, most recently Mac OS X v10.5 in October 2007. Releases of Mac OS X are named after big cats, for example Mac OS X v10.5 is usually referred to by Apple and users as "Leopard".