MacOS

macOS is a series of operating systems. The first OS, System 1, was released in 1984.

Mac OSes
Here is the list of all the Mac OSes.
 * Apple DOS (1978)
 * System 1 (1984)
 * System 2 (1985)
 * System 3 (1986)
 * System 4 (1987)
 * System 5 (1987)
 * System 6 (1988)
 * System 7/Mac OS 7 (1991)
 * Mac OS 8 (1997)
 * Mac OS 9 (1999)
 * Mac OS X Cheetah (2001)
 * Mac OS X Puma (2001)
 * Mac OS X Jaguar (2002)
 * Mac OS X Panther (2003
 * Mac OS X Tiger (2005)
 * Mac OS X Leopard (2007)
 * Mac OS X Snow Leopard (2009)
 * Mac OS X Lion (2011)
 * OS X Mountain Lion (2012)
 * OS X Mavericks (2013)
 * OS X Yosemite (2014)
 * OS X El Capitan (2015)
 * macOS Sierra (2016)
 * macOS High Sierra (2017)
 * macOS Mojave (2018)
 * macOS Denali (6932)