<P> macOS is the second major series of Macintosh operating systems . The first is colloquially called the `` classic '' Mac OS , which was introduced in 1984 , and the final release of which was Mac OS 9 in 1999 . The first desktop version , Mac OS X 10.0 , was released in March 2001 , with its first update , 10.1 , arriving later that year . After this , Apple began naming its releases after big cats , which lasted until OS X 10.8 Mountain Lion . Since OS X 10.9 Mavericks , releases have been named after landmarks in California . Apple shortened the name to `` OS X '' in 2012 and then changed it to `` macOS '' in 2016 , adopting the nomenclature that it uses for their other operating systems , iOS , watchOS , and tvOS . The latest version is macOS High Sierra , which was publicly released in September 2017 . </P>
what is the current mac os operating system
macOS High Sierra