macOS is a series of operating systems developed by Apple for their Mac platform. macOS is the second-most commonly used operating system after Microsoft Windows. It first became publicly available in 1984 with the release of the Macintosh 128k.
The classic Mac OS was originally written for the Motorola 68k architecture. The 68k architecture was used from 1984 to 1991, after which Apple transitioned to PowerPC. PowerPC would be used until the classic Mac OS's discontinuation in 2002. Classic Mac OS was based on a simple kernel design, which eventually became too limited and crash-prone for applications. In response, Apple bought NeXT and used NeXTSTEP as a base to develop Mac OS X. In 2006, Apple started to switch to using x86 (Intel) processors in Macs. Support for PowerPC in Mac OS X was dropped in 2009.
The Classic Mac OS can run standalone, and under Mac OS X using the Classic system layer. Only certain versions of Mac OS 9 can run under the Classic system layer, and the layer itself was dropped after Mac OS X Tiger.
PearPC is a useful emulator that can run PowerPC builds of Mac OS X under Windows or other x86 operating systems. PCE and Mini vMac are able to run 68k builds of Mac OS, QEMU is also capable of running earlier PPC builds of MacOS, and VirtualBox and VMware Fusion can run x86/64 builds of Mac OS X.
The original Macintosh System Software is based on the Lisa OS and UI concepts from Xerox PARC. It uses a monolithic architecture but lacks support for memory management, protected memory, access controls, and conflict-free extensions. Only one application at a time could be supported under System Software until version 5 when MultiFinder was introduced. In 1997, Apple rebranded the Macintosh System Software to Mac OS. Mac OS would continue to be developed until the introduction of Mac OS X, after which Apple only delivered minor updates to the classic Mac OS. The final minor updates were designed to ease the transition to OS X. Carbon, an API introduced with Mac OS 8, works as the transitional API for classic Mac OS and Mac OS X applications.
|System Software 1.x||1.0-1.1h||Released in January 1984-April 1984|
|System Software 2.x||2.0-2.1||Released in April 1985-September 1985|
|System Software 3.x||3.0-3.3||Released in January 1986-June 1987|
|System Software 4.x||4.0-4.1.1||Released in January 1987-July 1989|
|System Software 5.x||5.0-5.1||Released in October 1987-February 1988|
|System Software 6.x||6.0-220.127.116.11||Released in 1988-1992|
|Mac OS 7.x||7.0-7.6.1||Released in 1991-1997||Big Bang, Superbeta, Cube-E, Shuswap, Capone, Jirocho, Mozart, Son of Buster, Unity, Zeus, Gory, Harmony, Ides.|
|Mac OS 8.x||8.0-8.6||Released in 1997-1999||Copland, Tempo, Bride of Buster, Sequoia, Snowman, South Park, Allegro, Horatio, Veronica, Sarah.|
|Mac OS 9.x||9.0-9.2.2||Released in 1999-2001||Sonata, Minuet, Fortissimo, Moonlight, Limelight, LU1.|
Mac OS X / macOS
Mac OS X is the current incarnation of Mac OS. The first version released was Mac OS X Server in 1999. Unlike the classic Mac OS, Mac OS X is based on NeXTSTEP (OPENSTEP) and uses its frameworks and architectures. In 2016, Apple began to use the macOS moniker to brand Mac OS X alongside their other operating systems (watchOS, tvOS, iOS).
|Name||OS version||Darwin version||Codename||Notes|
|Mac OS X Server 1.x||N/A||Rhapsody 5.3 - 5.6[note 1]||Rhapsody||Released in March 1999; the first public release of OS X without the Aqua interface|
|Mac OS X Public Beta||N/A||1.2.1||Kodiak||Released in September 2000; first version to include the Aqua interface|
|Mac OS X Cheetah||10.0||1.3.1||Cheetah||Released in March 2001|
|Mac OS X Puma||10.1||1.4.1 / 5||Puma||Released in September 2001|
|Mac OS X Jaguar||10.2||6||Jaguar||Released in August 2002|
|Mac OS X Panther||10.3||7||Pinot||Released in October 2003|
|Mac OS X Tiger||10.4||8||Merlot (PPC) / Chardonay (Intel)||Released in April 2005 (PPC) / January 2006 (Intel)|
|Mac OS X Leopard||10.5||9||Chablis||Released in October 2007; last version to support the PowerPC architecture|
|Mac OS X Snow Leopard||10.6||10||Snow Leopard||Released in August 2009; final version to run PPC-only applications (via Rosetta)|
|Mac OS X Lion||10.7||11||Barolo||Released in July 2011|
|OS X Mountain Lion||10.8||12||Zinfandel||Released in July 2012|
|OS X Mavericks||10.9||13||Cabernet||Released in October 2013; last version to feature skeuomorphic Aqua interface|
|OS X Yosemite||10.10||14||Syrah||Released in October 2014|
|OS X El Capitan||10.11||15||Gala||Released in September 2015|
|macOS Sierra||10.12||16||Fuji||Released in September 2016|
|macOS High Sierra||10.13||17||Lobo||Released in September 2017|
|macOS Mojave||10.14||18||Liberty||Released in September 2018; last version to support 32-bit applications|
|macOS Catalina||10.15||19||Catalina||Released in October 2019|
|macOS Big Sur||11.0||20||Big Sur||To be released in Fall 2020|
- Mac OS X Server 1.x is a direct descendant of the NeXTSTEP/OPENSTEP codebase and is not based on Darwin.