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. It was noted for its ease of use, and also criticized for its lack of modern technologies compared to its competitors.[1][2]
The current Mac operating system is macOS, originally named "Mac OS X" until 2012 and then "OS X" until 2016.[3] It was developed between 1997 and 2001 after Apple's purchase of NeXT. It brought an entirely new architecture based on NeXTSTEP, a Unix system, that eliminated many of the technical challenges that the classic Mac OS faced, such as problems with memory management. The current macOS is pre-installed with every Mac and receives a major update annually.[4] It is the basis of Apple's current system software for its other devices – iOS, iPadOS, watchOS, and tvOS.[5]
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 namedStar Trek, Taligent, and Copland.
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.[6][7]
Apple released the original Macintosh on January 24, 1984; its early system software was partially based on the Lisa OS, and inspired by the Alto computer, which former Apple CEO Steve Jobs previewed at Xerox PARC.[6] 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.[8]
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.[9]
macOS Big Sur, released in 2020, introduced the current design iteration of macOS.
macOS (originally named "Mac OS X" until 2012 and then "OS X" until 2016)[10] is the current Mac operating system that officially succeeded the classic Mac OS in 2001.
The system was originally marketed as simply "version 10" of Mac OS, but it has a history that is largely independent of the classic Mac OS. It is a Unix-based operating system[11][12] 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.[13] Precursors to the original release of Mac OS X include OPENSTEP, Apple's Rhapsody project, and the Mac OS X Public Beta.
The first 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.[4]
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 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
macOS Sonoma - version 14, released to end users on Tuesday, September 26, 2023
As of 2020, only one version of macOS was never publicly released, with its version number updated during development. 10.16 was updated to 11.0 in the third beta; the third beta version of macOS Big Sur was 11.0 Beta 3 instead of 10.16 Beta 3.
Server
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.[15]
The Apple Real-time Operating System Environment (A/ROSE) was a small embedded operating system which ran on the Macintosh Coprocessor Platform, an expansion card for the Macintosh. The idea was to offer a single "overdesigned" hardware platform on which third-party vendors could build practically any product, reducing the otherwise heavy workload of developing a NuBus-based expansion card. The first version of the system was ready for use in February 1988.[16]
In 1988, Apple released its first UNIX-based OS, A/UX, which was a UNIX operating system with the Mac OS look and feel. It was not very competitive for its time, due in part to the crowded UNIX market and Macintosh hardware lacking high-end design features present on workstation-class computers. A/UX had most of its success in sales to the U.S. government, where POSIX compliance was a requirement that Mac OS could not meet.[17]
Announced at the 1996 Worldwide Developers Conference (WWDC), MkLinux is an open source operating system that was started by the OSF Research Institute and Apple in February 1996 to port Linux to the PowerPC platform, and thus Macintosh computers. In mid 1998, the community-led MkLinux Developers Association took over development of the operating system. MkLinux is short for "Microkernel Linux," which refers to the project's adaptation of the Linux kernel to run as a server hosted atop the Mach microkernel. MkLinux is based on version 3.0 of Mach.[19]
Star Trek (as in "to boldly go where no Mac has gone before") was a relatively unknown secret prototype beginning in 1992, whose goal was to create a version of the classic Mac OS that would run on Intel-compatible x86 personal computers. In partnership with Apple and with support from Intel, the project was instigated by Novell, which was looking to integrate its DR-DOS with the Mac OS GUI as a mutual response to the monopoly of Microsoft's Windows 3.0 and MS-DOS. A team consisting of four from Apple and four from Novell was able to get the Macintosh Finder and some basic applications such as QuickTime, running smoothly on the x86 architecture. The project was canceled a year later in early 1993, but some of the code was later reused when porting the Mac OS to PowerPC.[20][21]
Taligent (a portmanteau of "talent" and "intelligent") was the name of an object-oriented operating system and the company dedicated to producing it. Started as a project within Apple to provide a replacement for the classic Mac OS, it was later spun off into a joint venture with IBM as part of the AIM alliance, with the purpose of building a competing platform to Microsoft Cairo and NeXTSTEP. The development process never worked, and Taligent is often cited as an example of a project death march. Apple pulled out of the project in 1995 before the code had been delivered.[22]
Copland was a project at Apple to create an updated version of the classic Mac OS. It was to have introduced protected memory, preemptive multitasking and a number of new underlying operating system features, yet still be compatible with existing Mac software. As originally planned, a follow-up release known as "Gershwin" would add multithreading and other advanced features. New features were added more rapidly than they could be completed, and the completion date slipped into the future with no sign of a release. In 1996, Apple decided to cancel the project outright and find a suitable third-party system to replace it. Copland development ended in August 1996, and in December 1996, Apple announced that it was buying NeXT for its NeXTSTEP operating system.[23]
