file extension MNU

MS-DOS (short for Microsoft Disk Operating System) is an operating system commercialized by Microsoft. It was the most commonly used member of the DOS family of operating systems and was the dominant operating system for computers during the 1980s. It was based on the Intel 8086 family of microprocessors, particularly the IBM PC and compatibles. It was gradually replaced on consumer desktop computers by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system. It was originally known as QDOS (Quick and Dirty Operating System) and 86-DOS.

MS-DOS was originally released in 1981 and had eight major versions released before Microsoft stopped development in 2000. It was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI.