OS X (pronounced /ˌoʊ ɛs ˈtɛn/;originally Mac OS X) is a series of Unix-based graphical interface operating systems developed and marketed by Apple Inc. It is designed to run on Macintosh computers, having been pre-installed on all Macs since 2002. It was the successor to Mac OS 9, released in 1999, the final release of the « classic » Mac OS, which had been Apple’s primary operating system since 1984. The first version released was Mac OS X Server 1.0 in 1999, and a desktop version, Mac OS X v10.0 « Cheetah » followed on March 24, 2001. Previous releases of OS X were named after big cats; for example, OS X v10.8 was referred to as « Mountain Lion ». However, with the announcement of OS X Mavericks in June 2013, this was dropped in favor of Californian landmarks. Within the market of desktop, laptop and home computers, and by web usage, OS X is the second most widely used OS after Windows.