(Mac OS 10) The current operating system from Apple for the Mac family. Starting in the fall of 2016, Version 10.12 uses the rebranded "macOS" moniker and not OS X. See
macOS and
Sierra.
OS X Server was introduced in 1999, and the client version came out in 2001. Based on Unix and featuring an entirely redesigned user interface, OS X was a major departure from the previous OS 9 system. For the first time, the rich set of Unix commands became available to all Mac developers (A/UX was an earlier Unix OS for the Mac but was not widely used).
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.
Legacy Software
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, Apple switched from the PowerPC to the Intel platform, and Classic support was dropped in the Intel version of OS X. However, PowerPC applications could run on Intel Macs via an emulator (see
Rosetta).
Programming Environments
There have been 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.
Faster Cats!
Mac OS X versions were internally code-named after jungle cats. Starting with Version 10.2 (Jaguar), the animals became the official product name until Version 10.9 (see below). See
Rhapsody and
Bonjour.
OS X Version Jungle Cat
10.0 2001 Cheetah (code name)
10.1 2001 Puma (code name)
10.2 2002 Jaguar
10.3 2003 Panther
10.4 2005 Tiger
10.5 2007 Leopard
10.6 2009 Snow Leopard
10.7 2011 Lion
10.8 2012 Mountain Lion
OS X Version Place
10.9 2013 Mavericks
10.10 2014 Yosemite
10.11 2015 El Capitan
macOS Version Place
10.12 2016 Sierra
10.13 2017 High Sierra
10.14 2018 Mojave