The Macintosh Operating System (Mac OS) is a program that allows a Macintoshcomputer to operate and be used. Mac OS was first made by Apple Inc. in 1984. In those days Mac OS was called Macintosh System Software – which was shortened to System or SSW (System Software). The term "Mac OS" first appeared in the splash screen for System 7.5.1, but was not adopted as the new name until the release of Mac OS 7.6.
The latest version of Mac OS is macOS 10.12 Sierra. The X in the OS X name is a roman numeral for 10.
↑Operating System Market Share, November 2012, courtesy of Net Applications, a marketing company which obtains its data from the Alexa Toolbar or related products. Because people who install these products on their computers are not always aware that the product reports web browsing habits back to the marketers at Alexa some security software considers the Alexa Toolbar spyware and removes it. Both the automated removal-as-spyware and the self-selecting nature of those who install software that reports on personal web browsing habits raises questions as to whether the resulting data represents a unbiasedstatistical sample of Internet users.