(Mac OS 10) The current operating system from Apple for the Mac family. Superseding Mac OS 9, OS X Server was introduced in 1999, and the client version came out in 2001. Entirely Unix based, OS X is a major departure from OS 9 with a redesigned user interface (Aqua) and many new features. As a Unix operating system, the rich set of Unix commands became available to all Mac developers for the first time. Years ago, A/UX was an optional Unix-based OS for the Mac, but was never its mainstream environment.|
OS X added protected memory, pre-emptive multitasking, multithreading and symmetric multiprocessing (SMP) to the Mac world. The heart of OS X is the open source, POSIX-compliant Darwin kernel, which includes an enhanced BSD 4.4 operating system and Mach 2.5 microkernel. See HFS.
Prior to Mac OS X 10.5 (Leopard), OS X ran legacy OS 9 and earlier applications via its Classic software, which was a full copy of OS 9 that ran as an OS X process. Classic was not preloaded on new Macs, but was available for installation from the system disks.
In 2006, when Apple began the switch from the PowerPC to the Intel platform, running an Intel x86 version of Mac OS X, Classic support was dropped. However, most PowerPC applications run on Intel Macs via an emulator (see Rosetta).
There are five programming interfaces (APIs) for writing Mac OS X applications. Cocoa is the native OS X interface, derived from OpenStep. Carbon is used for applications that can run on both OS X and earlier Mac OS machines, and Classic is the API prior to Mac OS X. Programs can also be developed in Java and BSD. See OpenStep and Cocoa.
Mac OS X versions were internally code named after wild cats starting with the Cheetah. Starting with Version 10.2 (Jaguar), the animals became the official product name. See Rhapsody and Bonjour.
10.0 Cheetah (code name)
10.1 Puma (code name)
10.6 Snow Leopard