Twenty-two-year-old Tim Paterson was hired in June 1978 by SCP's owner Rodney Maurice Brock (26 August 1930 – 30 November 2018).

[8] Digital Research, whose 8-bit CP/M operating system was the industry standard, was working on an 8086-compatible version called CP/M-86, but the delay in its release was costing SCP sales.

In order to fill this void, Paterson wrote QDOS (for Quick and Dirty Operating System)[1] over a four-month period starting in April 1980.

On 27 July 1981, just prior to the launch of the IBM PC on the 12 August 1981, Microsoft bought the full rights to the operating system for an additional US$50,000, giving SCP a perpetual royalty-free license to sell 86-DOS (including updated versions) with its computer hardware.

[3] Realizing that Microsoft was making significant profit on the 86-DOS operating system, SCP attempted to sell it along with a stand-alone inexpensive CPU (without any other circuitry).