Mircosoft entered the OS business in 1980 with Xenix, a Unix-based OS, it had moderate success, they started developing a DOS operating System known as MS-DOS, they just needed a computer to provide the OS On, they almost got it with IBM in November of 1980 but negotiations went sour when IBM decided to exclusively use Digital Researches CP/M-86s OS instead, Mircosoft without a computer to supply MS-DOS with decided to scrap the project.