Macintosh Operating Systems

The original Macintosh System Software and Finder, released in 1984

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The family of Macintosh operating systems developed by Apple Inc. includes the graphical user interface-based operating systems it was designed for use with its Macintosh series of personal computers since 1984, as well as the related system software it once created for compatible third-party systems.

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 1996, was preinstalled 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 preinstalled with every Mac and is updated annually. It is the basis of Apple's current system software for its other devices, iOS, 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, the Macintosh 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 files deletion to real-world objects like folders and a trash can; and overlapping windows for multitasking.

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 through 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.

Releases

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.

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

Main article: macOS

Desktop

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 annual basis.[4]

Mac OS X 10.0 – code name "Cheetah", released to end users on Saturday, March 24, 2001

Mac OS X 10.1 – code name "Puma", released to end users on Tuesday, September 25, 2001