DeveloperApple, Inc.
Source modelClosed source (with open source components)
Initial releaseSystem Software 1
(24 January 1984)
Latest releasemacOS Monterey
(25 October 2021)
Latest previewmacOS Monterey (build 21C5045a)
(1 December 2021)
Supported platformsx86_64, ARM64 (previously 68k, PPC and i386)
Kernel typeHybrid (XNU)
User interfaceAqua

macOS is a series of operating systems developed by Apple for their Macintosh 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 1994, 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 switched to Intel-based x86 processors in Macs. Support for PowerPC in Mac OS X was dropped in 2009.

At WWDC 2020, Apple declared that they would switch over to the Apple Silicon SoC in future Mac computers.

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.

Timeline[edit | edit source]

Classic[edit | edit source]

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.

Classic Mac OS versions
Name Versions Release date(s), Notes Codenames
System Software 1 1.0-1.1h Released in January 1984-April 1984; uses the 68k architecture
System Software 2 2.0-2.1 Released in April 1985-September 1985
System Software 3 3.0-3.3 Released in January 1986-June 1987
System Software 4 4.0-4.1.1 Released in January 1987-July 1989
System Software 5 5.0-5.1 Released in October 1987-February 1988
System Software 6 6.0- Released in 1988-1992
Mac OS 7 7.0-7.6.1 Released in 1991-1997; first version to officially run on PowerPC (added on version 7.1.2) Big Bang, Superbeta, Cube-E, Shuswap, Capone, Jirocho, Mozart, Son of Buster, Unity, Zeus, Gory, Harmony, Ides.
Mac OS 8 8.0-8.6 Released in 1997-1999; version 8.5 removed support for 68k Copland, Tempo, Bride of Buster, Sequoia, Snowman, South Park, Allegro, Horatio, Veronica, Sarah.
Mac OS 9 9.0-9.2.2 Released in 1999-2001; version 9.2 requires a PowerPC G3 processor Sonata, Minuet, Fortissimo, Moonlight, Limelight, LU1.

UNIX-based[edit | edit source]

macOS (formerly known as Mac OS X until 2012, or OS X until 2016) is the current incarnation of Mac OS. The first version released was Mac OS X Server in 1999. Unlike the classic Mac OS, it is based on NeXTSTEP and uses its frameworks and architectures. In 2012, Apple began to use the OS X moniker to brand Mac OS X alongside their other operating systems (watchOS, tvOS, iOS). In 2016, Apple began to use the macOS moniker to brand OS X alongside their other operating systems (watchOS, tvOS, iOS).

macOS versions
Name OS version Darwin version Codename(s) Notes
Mac OS X Server 1.x N/A Rhapsody 5.3 - 5.6[note 1] Rhapsody Released in March 1999
Mac OS X Public Beta N/A 1.2.1 Kodiak Released in September 2000; introduced 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; first version to officially run on Intel (added in 10.4.1)
Mac OS X Leopard 10.5 9 Chablis Released in October 2007; removes support for PowerPC G3 processors
Mac OS X Snow Leopard 10.6 10 Snow Leopard Released in August 2009; removes support for PowerPC Macs
Mac OS X Lion 10.7 11 Barolo Released in July 2011; removes support for PPC-only applications via Rosetta; removes support for x86 processors
OS X Mountain Lion 10.8 12 Zinfandel Released in July 2012; removes the 32-bit kernel and 32-bit EFI bootloader
OS X Mavericks 10.9 13 Cabernet Released in October 2013
OS X Yosemite 10.10 14 Syrah Released in October 2014; refreshed UI design
OS X El Capitan 10.11 15 Gala Released in September 2015
macOS Sierra 10.12 16 Fuji Released in September 2016; removes support for non-SSE4 Intel CPUs
macOS High Sierra 10.13 17 Lobo Released in September 2017
macOS Mojave 10.14 18 Liberty Released in September 2018
macOS Catalina 10.15 19 Marzipan Released in October 2019; removes support for 32-bit applications
macOS Big Sur 11 20 Golden Gate Released in November 2020; refreshed UI design again; first version to run on Apple Silicon.
macOS Monterey 12 21 Star Released in October 2021

Notes[edit | edit source]

  1. Mac OS X Server 1.x is a direct descendant of the NeXTSTEP/OPENSTEP codebase and is not based on Darwin.