MS-DOS MS-DOS, short for Microsoft Disk Operating System, was an operating system for x86-based personal computers mostly developed by Microsoft. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid-1990s, when it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the Microsoft Windows operating system. Microsoft 1981 1981-08-01 August 1, 1981 OS 3-4 3161BC FDC20F 8461A9 CA1A15 111111 1-1