Microsoft MS-DOS

MS-DOS is Microsoft's command line Disk Operating System, originally bought and modified to run on the original IBM PC. It used a command line interface because affordable IBM PC-based home computers of that era were not capable of running a Graphical User Interface yet. The DOS command line interface came to define the stereotypical "hacker typing away on a keyboard" method of using computers in the 1980s.

The original IBM PC first booted to its BIOS, and then the BIOS booted the first 512k sector of disk, which containted the DOS Master Boot Record.

DOS Catapults Microsoft to the Limelight

It can be said with a degree of certainty that the original deal Microsoft made with IBM, where MS-DOS was licensed to run on IBM's computers instead of sold outright to them, was the chief enabling factor in Microsoft's rise to its current status as the largest software vendor in the world. IBM's "great folly" with DOS was the assumption that "people pay for the hardware; no one makes money on software." IBM chose Microsoft over Digital Research, the company which produced CP/M. CP/M was the most common third party operating system available to that time.