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.