I didn't know anyone with a DOS system in the early '80s, but I knew plenty of people with Commodore 64s, TI 99-4As, Apple IIs, computers by Tandy, and even Timex--all with distinct and incompatible operating systems.
Nobody used DOS in the '80s.
mnli hypothesis: Nobody used DOS in the '80s. premise: I didn't know anyone with a DOS system in the early '80s, but I knew plenty of people with Commodore 64s, TI 99-4As, Apple IIs, computers by Tandy, and even Timex--all with distinct and incompatible operating systems.