MacOS

macOS (previously Mac OS X and OS X, "X" pronounced "ten" ) is a series of graphical operating systems developed and marketed by Apple Inc. since 2001. It is the primary operating system for their Macintosh family of computers, and is the second most widely used desktop operating system after Microsoft Windows.

macOS is the second major series of Macintosh operating systems, with the first – colloquially called the "classic" Mac OS – introduced in 1984 and the final release (Mac OS 9) released in 1999. During this time, Apple co-founder Steve Jobs had left Apple and started another company called NeXT, developing the NeXTSTEP platform that would later be acquired by Apple to form the basis of macOS.

The first desktop version, Mac OS X Cheetah 10.0, was released in March 2001. The first update to the series, 10.1, arrived later that year. After this, Apple began naming its releases after big cats, which lasted until OS X Mountain Lion 10.8; the release of OS X Mavericks (10.9) began the naming convention of locations in California. After sixteen distinct versions of macOS 10, macOS Big Sur was presented as version 11 in 2020, and macOS Monterey as version 12 in 2021. Apple's mobile operating system, iOS, has been considered a variant of macOS.

A prominent part of macOS's original brand identity was the use of Roman numeral X, pronounced "ten" as in Mac OS X and also the iPhone X, as well as code naming each release after species of big cats, or places within California. Apple shortened the name to "OS X" in 2012, and changed it again to "macOS" in 2016 to align with the branding of Apple's other operating systems, iOS, watchOS, and tvOS.

macOS has supported three major processor architectures, beginning with PowerPC-based Macs in 1999. In 2006, Apple transitioned to the Intel architecture with a line of Macs using Intel Core processors. In 2020, Apple began the Apple silicon transition, using self-designed, 64-bit ARM-based Apple M1 processors on new Mac computers.

Development
macOS originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. The Unix-like NeXTSTEP operating system by the company was developed and launched in 1989. The kernel of NeXTSTEP is based upon the Mach kernel, which was originally developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from parts of BSD. Its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language.

Versions

 * macOS Monterey (12)
 * macOS Big Sur (11)
 * macOS Catalina (10.15)
 * macOS Mojave (10.14)
 * macOS High Sierra (10.13)
 * macOS Sierra (10.12)
 * OS X El Capitan (10.11)
 * OS X Yosemite (10.10)
 * OS X Mavericks (10.9)
 * OS X Mountain Lion (10.8)
 * Mac OS X Lion (10.7)
 * Mac OS X Snow Leopard (10.6)
 * Mac OS X Leopard (10.5)
 * Mac OS X Tiger (10.4)
 * Mac OS X Panther (10.3)
 * Mac OS X Jaguar (10.2)
 * Mac OS X Puma (10.1)
 * Mac OS X Cheetah (10.0)
 * Mac OS X Public Beta