Apple's operating system for computers.

(version 10.5) the sixth major release of macOS, Apple's desktop and server operating system for Macintosh computers.

Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer, Inc. from 1984 to 2001, starting with System 1 and ending with Mac OS 9.

(version 10.2) the third major release of macOS, Apple's desktop and server operating system.

(version 10.3) the fourth major release of macOS, Apple's desktop and server operating system.

(version 10.4) the 5th major release of macOS, Apple's desktop and server operating system for Mac computers.

(version 10.6) (also referred to as OS X Snow Leopard) the seventh major release of macOS, Apple's desktop and server operating system for Macintosh computers.

the ninth and final major release of Apple's classic Mac OS operating system, which was succeeded by Mac OS X 10.0 in 2001, starting the Mac OS X family of operating systems.

(code named Cheetah) the first major release of macOS, Apple's desktop and server operating system.

the eighth major release of the classic Mac OS operating system for Macintosh computers, released by Apple Computer on July 26, 1997.

an operating system developed by Apple, Inc. released on March 16, 1999.

(code named Puma) the second major release of macOS, Apple's desktop and server operating system.

(internally code named "Kodiak") the first publicly available version of Apple Computer's Mac OS X (now named macOS) operating system to feature the Aqua user interface.