MS-DOS is 30 years old today. Well, kind of. On 27 July 1981, Microsoft gave the name MS-DOS to the disk operating system it acquired on that day from Seattle Computer Products (SCP), a hardware company owned and run by a fellow called Rod Brock.

SCP developed what it at various times called QDOS and 86-DOS to run on a CPU card it had built based on Intel’s 8086 processor.

The company had planned to use Digital Research’s CP/M-86 operating system, then still in development. But, having released the card in November 1979 – it shipped with an 8086-compatible version Microsoft’s Basic language interpreter-cum-operating system – and reached April 1980 without CP/M-86 becoming available to bundle, SCP decided it had to create its own OS for the card.

Enter, in August 1980, QDOS. It really did stand for Quick and Dirty Operating System. That’s actually what it was: a basic but serviceable OS good for coding and running programs written in 8086 assembly language – the x86 instruction set. It was written by SCP’s Tim Paterson, who had joined the company as a programmer a couple of years previously and began work on it in April 1980.

Read the rest of the History of MS-Dos at Microsoft’s MS-DOS is 30 today.