A townhouse is a type of structure. A condominium is a type of ownership. Condominium's can be townhouses, apartments, trailer park lots or freestanding homes.

I started with CP/M on Cromemco and Northstar systems in the mid 70's and was running an H89 with it by the time IBM came out with the PC. It was much better than MSDOS but neither as cheap nor as ubiquitous the mess supported by Itty Bitty Morons.
Back then a lot of people wrote operating systems but few of them made it into the mainstream. Who remembers HDOS? Even QDOS has a minute and declining marked share.
Glen