Good lord, CPM that I ran on an old 2nd hand Altair then patched to run on a borrowed 1985 IBM XT. Then to DOS 2.01 on a Tandy 1000EX with COLOR CGA monitor in 1987. When one of the best games was Red Baron and an external 20 MB hard drive was huge!!!
When Apple had their own DOS, I used to hack all my buddy's files for "Ultima I, II, III". Not sure that's the right title, but it was kinda like a Dungeons and Dragons role player. I could make them invincible for a "slight fee"! Heh, heh!
20 MB???? Hell, I thought I was a hot-rod with 8!