macOS (originally named Mac OS X until 2012 and then OS X until 2016) is the current series of Unix-based graphical operating systems developed and marketed by Apple Inc. designed to run on Macintosh computers, having been pre-installed on all Macs since 2002. Within the market of desktop, laptop and home computers, and by web usage, it is the second most widely used desktop OS after Windows. Launched in 2001 as "Mac OS X", the series is the latest in the family of Macintosh operating systems; it has succeeded the "classic" Mac OS, which was introduced in 1984 and the final release of which was Mac OS 9 in 1999. An initial, early version of the system, Mac OS X Server 1.0, was released in 1999; the first desktop version, Mac OS X 10.0, followed in March 2001. In 2012, Apple renamed the brand to "OS X". Releases were code named and later marketed after big cats through Mountain Lion (10.8); starting in 2013 with Mavericks (10.9), they have been named after landmarks in California. In 2016, Apple renamed the brand to "macOS", adopting the nomenclature that it uses for its other operating systems, iOS, watchOS, and tvOS. The latest version of the series is Sierra (10.12), which was publicly released in September 2016. The system is based on technologies developed at NeXT between the second half of the 1980s and Apple's purchase of the company in late 1996. The "X" in "Mac OS X" and "OS X" was pronounced "ten" as a Roman numeral for the version number "10", was a prominent part of its brand identity, and was used to showcase Unix compatibility; UNIX 03 certification was achieved for Intel CPUs in Leopard (10.5) and all releases from Snow Leopard (10.6) through Sierra (10.12). macOS shares its Unix-based Darwin core and many of its frameworks with iOS, the mobile OS for the iPhone, iPod Touch, iPad, and the 2nd and 3rd generation Apple TV; tvOS, for the 4th generation Apple TV; and watchOS, for the Apple Watch. Earlier, a variant of Tiger (10.4) powered the first-generation Apple TV. Apple also formerly issued a separate line of releases of the system for server computing; that functionality is now offered as an add-on. The earlier releases of Mac OS X from 1999 to 2005 can run only on the PowerPC-based Macs from the time period. After Apple announced a shift to using Intel x86 CPUs from 2006 onwards, Tiger (10.4) and Leopard (10.5) were released in versions for both Intel and PowerPC processors, but Snow Leopard (10.6) dropped PowerPC support. Support for 32-bit Intel processors was dropped after Lion (10.7); all versions of the system released since then run exclusively on 64-bit Intel CPUs.