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Apple Macintosh Desktop
The original Macintosh System Software and Finder, released in 1984

Two major families of Mac operating systems were developed by Apple Inc.

In 1984, Apple debuted the operating system that is now known as the "Classic" Mac OS with its release of the original Macintosh System Software. The system, rebranded "Mac OS" in 1997, was pre-installed on every Macintosh until 2002 and offered on Macintosh clones for a short time in the 1990s. Noted for its ease of use, it was also criticized for its lack of modern technologies compared to its competitors.

The current Mac operating system is macOS, originally named "Mac OS X" until 2012 and then "OS X" until 2016. Developed between 1997 and 2001 after Apple's purchase of NeXT, Mac OS X brought an entirely new architecture based on NeXTSTEP, a Unix system, that eliminated many of the technical challenges that the classic Mac OS faced. The current macOS is pre-installed with every Mac and receives a major update annually. It is the basis of Apple's current system software for its other devices – iOS, iPadOS, watchOS, and tvOS.

Prior to the introduction of Mac OS X, Apple experimented with several other concepts, releasing different products designed to bring the Macintosh interface or applications to Unix-like systems or vice versa, A/UX, MAE, and MkLinux. Apple's effort to expand upon and develop a replacement for its classic Mac OS in the 1990s led to a few cancelled projects, code named Star Trek, Taligent, and Copland.

Although they have different architectures, Mac operating systems share a common set of GUI principles, including a menu bar across the top of the screen; the Finder shell, featuring a desktop metaphor that represents files and applications using icons and relates concepts like directories and file deletion to real-world objects like folders and a trash can; and overlapping windows for multitasking.

Classic Mac OS

Mac OS 9.0.4 emulated inside of the SheepShaver emulator
Mac OS 9, released in 1999

The "classic" Mac OS is the original Macintosh operating system that was introduced in 1984 alongside the first Macintosh and remained in primary use on Macs until the introduction of Mac OS X in 2001.

Apple released the original Macintosh on January 24, 1984; its early system software was partially based on the Lisa OS and the Xerox PARC Alto computer, which former Apple CEO Steve Jobs previewed. It was originally named "System Software", or simply "System"; Apple rebranded it as "Mac OS" in 1996 due in part to its Macintosh clone program that ended a year later.

Classic Mac OS is characterized by its monolithic design. Initial versions of the System Software run one application at a time. System 5 introduced cooperative multitasking. System 7 supports 32-bit memory addressing and virtual memory, allowing larger programs. Later updates to the System 7 enable the transition to the PowerPC architecture. The system was considered user-friendly, but its architectural limitations were critiqued, such as limited memory management, lack of protected memory and access controls, and susceptibility to conflicts among extensions.


Mac OS wordmark logo
The text-only logo for Classic Mac OS starting with Mac OS 7.6, released in 1997

Nine major versions of the classic Mac OS were released. The name "Classic" that now signifies the system as a whole is a reference to a compatibility layer that helped ease the transition to Mac OS X.

  • Macintosh System Software – "System 1", released in 1984
  • System Software 2, 3, and 4 – released between 1985 and 1987
  • System Software 5 – released in 1987
  • System Software 6 – released in 1988
  • System 7 / Mac OS 7.6 – released in 1991
  • Mac OS 8 – released in 1997
  • Mac OS 9 – final major version, released in 1999

Mac OS X / OS X / macOS

MacOS Mojave Desktop
macOS Mojave, released in 2018

macOS (originally named "Mac OS X" until 2012 and then "OS X" until 2016) is the current Mac operating system that officially succeeded the classic Mac OS in 2001.

Although the system was originally marketed as simply "version 10" of Mac OS, it has a history that is largely independent of the classic Mac OS. It is a Unix-based operating system built on NeXTSTEP and other technology developed at NeXT from the late 1980s until early 1997, when Apple purchased the company and its CEO Steve Jobs returned to Apple. Precursors to the original release of Mac OS X include OPENSTEP, Apple's Rhapsody project, and the Mac OS X Public Beta.

macOS makes use of the BSD codebase and the XNU kernel, and its core set of components is based upon Apple's open source Darwin operating system.

macOS is the basis for some of Apple's other operating systems, including iPhone OS/iOS, iPadOS, watchOS, and tvOS.


The "X" logo for Mac OS X versions 10.0 "Cheetah" and 10.1 "Puma", released in 2001


The first desktop version of the system was released on March 24, 2001, supporting the Aqua user interface. Since then, several more versions adding newer features and technologies have been released. Since 2011, new releases have been offered on an yearly basis.

  • Mac OS X 10.0 – code named "Cheetah", released to end users on Saturday, March 24, 2001
  • Mac OS X 10.1 – code named "Puma", released to end users on Tuesday, September 25, 2001
  • Mac OS X Jaguar – version 10.2, released to end users on Friday, August 23, 2002
  • Mac OS X Panther – version 10.3, released to end users on Friday, October 24, 2003
  • Mac OS X Tiger – version 10.4, released to end users on Friday, April 29, 2005
  • Mac OS X Leopard – version 10.5, released to end users on Friday, October 26, 2007
  • Mac OS X Snow Leopard – version 10.6, publicly unveiled on Monday, June 8, 2009
  • Mac OS X Lion – version 10.7, released to end users on Wednesday, July 20, 2011
  • OS X Mountain Lion – version 10.8, released to end users on Wednesday, July 25, 2012
  • OS X Mavericks – version 10.9, released to end users on Tuesday, October 22, 2013
  • OS X Yosemite – version 10.10, released to end users on Thursday, October 16, 2014
  • OS X El Capitan – version 10.11, released to end users on Wednesday, September 30, 2015
  • macOS Sierra – version 10.12, released to end users on Tuesday, September 20, 2016
  • macOS High Sierra – version 10.13, released to end users on Monday, September 25, 2017
  • macOS Mojave – version 10.14, released to end users on Monday, September 24, 2018
  • macOS Catalina – version 10.15, released to end users on Monday, October 7, 2019
  • macOS Big Sur – version 11, released to end users on Thursday, November 12, 2020
  • macOS Monterey – version 12, released to end users on Monday, October 25, 2021
  • macOS Ventura – version 13, released to end users on Monday, October 24, 2022


An early server computing version of the system was released in 1999 as a technology preview. It was followed by several more official server-based releases. Server functionality has instead been offered as an add-on for the desktop system since 2011.

  • Mac OS X Server 1.0 – code named "Hera", released in 1999
  • macOS Server – several releases since 2001

Related systems

Before the arrival of the Macintosh in 1984, Apple's history of operating systems began with its Apple II series computers in 1977, which ran Apple DOS, ProDOS, and later GS/OS; the Apple III in 1980, which ran Apple SOS; and the Apple Lisa in 1983, which ran Lisa OS and later MacWorks XL, a Macintosh emulator. Apple also developed the Newton OS for its Newton personal digital assistant from 1993 to 1997.

In recent years, Apple has also launched several new operating systems based on the core of macOS, including iOS in 2007 for its iPhone, iPad, and iPod Touch mobile devices and in 2017 for its HomePod smart speakers; watchOS in 2015 for the Apple Watch; tvOS in 2015 for the Apple TV set-top box.

See also

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