Today’s PC VMs have nothing on IBM who started doing this in the late 1960s with CP/CMS. VM/370 was released in 1972. I ran TK4- (MVS 3.8J) and DOS/VS under one VM/370…running in Hercules. Would anyone do this in the real world? Perhaps a school. IDK.
DOS/VS is the only OS I didn’t bring completely up, because I got lazy. But I have little doubt at this point, that I can. Sorting out the disk layouts was a little tedious. . Bring up/down DOS/VS is very tedious. I was looking for a way to cut my shutdown procedure. I’m probably safe just forcing DOS off at this stage. I’ll bring everything fully up another time.