The term 'Computer Operating System' refers to the software that manages the hardware and software resources of a computer. Three common examples of computer operating systems are UNIX, MSDOS, and LINUX. UNIX is a multi-user, multitasking operating system developed in the 1970s. MSDOS is a single-user, single-tasking operating system developed by Microsoft in the 1980s. LINUX is a free, open-source operating system developed in the 1990s. All three operating systems are widely used today.