The usage share of an operating system is the percentage of computers running that operating system.

This article presents a timeline of events in the history of computer operating systems from 1951 to the current day.

Computer operating systems (OSes) provide a set of functions needed and used by most application programs on a computer, and the links needed to control and synchronize computer hardware.

These tables provide a comparison of operating systems, of computer devices, as listing general and technical information for a number of widely used and currently available PC or handheld (including smartphone and tablet computer) operating systems.

This is a list of real-time operating systems (RTOSs).