macOS

macOS

Developer	Apple, Inc.
Source model	Closed source (with open source components)
Initial release	System Software 1 (24 January 1984)
Latest release	macOS Big Sur (12 November 2020)
Latest preview	macOS Monterey (build 21A5506j) (30 August 2021)
Supported platforms	x86_64, ARM64 (previously 68k, PPC and i386)
Kernel type	Hybrid (XNU)
User interface	Aqua
License	Proprietary

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 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 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

Classic

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.

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	6.0-6.0.8.1	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	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(s)	Notes
Mac OS X Server 1.x	N/A	Rhapsody 5.3 - 5.6	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
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	10.16 (Internal)	20	Golden Gate	Released in November 2020; refreshed UI design again; first version to run on Apple Silicon
	11 (Displayed)
macOS Monterey	12	21	Star	Will be released in the second half of 2021.