Apple's other operating systems ( iOS, iPadOS, watchOS, tvOS, audioOS) are derivatives of macOS.Ī 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. All releases from Mac OS X 10.5 Leopard and after are UNIX 03 certified, with an exception for Mac OS X 10.7 Lion. The first desktop version, Mac OS X 10.0, was released on March 24, 2001. During this time, Apple co-founder Steve Jobs had left Apple and started another company, NeXT, developing the NeXTSTEP platform that would later be acquired by Apple to form the basis of macOS.

MacOS succeeded the classic Mac OS, a Macintosh operating system from 1984 to 2001. Within the market of desktop and laptop computers, it is the second most widely used desktop OS, after Microsoft Windows and ahead of Linux (including ChromeOS). It is the primary operating system for Apple's Mac computers. MacOS ( / ˌ m æ k oʊ ˈ ɛ s/ previously OS X and originally Mac OS X) is an operating system developed and marketed by Apple Inc.

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