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The name of Apple's Mac operating system, starting with the Sierra Version 10.12 in 2016. Since its introduction in 1984, Mac operating systems have been written for three hardware lines: Motorola, PowerPC and Intel. See macOS server, Macintosh, operating system and Mojave.

Name Evolution
The Mac originally used "System" designations, which then became "Mac OS." Starting in 1999, Mac OS X was a major upgrade. The Mac OS X moniker was used with a subtitle of an animal name and later a California location (see Mac OS X).

YearIntro  Official Name

 1984   (Classic) "System" 1 to 7.5

 1995   (Classic) "Mac OS" 7.5.1 to 9.2.2

 1999   "Mac OS X" 10.0 to 10.8

 2013   "OS X" 10.9 to 10.11

 2016   "macOS" 10.12 and up
References in periodicals archive ?
If Apple plans on sticking to its typical schedule, both iOS 12 and macOS 13.
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Apple's arguably popular voice assistant, Siri, has finally waded its way to macOS.
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One of the important bug fixes that will arrive with macOS High Sierra 10.
The problem with iMessage on macOS High Sierra was first spotted by (http://appleinsider.
The update was made available for free from Apple and is labeled as macOS High Sierra 10.
The vulnerability inside macOS High Sierra was first reported by ex-NSA analyst (https://twitter.
Apple has started rolling out a golden master candidate build of the upcoming macOS High Sierra update for Mac devices.