MS-DOS is an operating system bought by Microsoft. It was the most commonly used member of the DOS family of operating systems and was the main operating system for personal computers during the 1980s and 1990s. It was preceded by M-DOS, designed and copyrighted by Microsoft in 1979. MSDOS was written for 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, in particular by various generations of the Microsoft Windows operating system. MS-DOS developed out of QDOS, also known as 86-DOS.