I remember CP/M. We had a machine with multiple 8088 processors sharing a single 30Mb disk. Each processor ran CP/M. and ran a terminal. No graphics, jusr CLI. That type,of architecture seems to have disappeared.
We also had an Osborne portable which ran CP/M from 5 in
floppy disks. It had supercalc… my first encounter with a spreadsheet.
At around the same time we had BSD Unix on what was basically a PDP minicomputer with a 68010 processor.
Unix was way ahead of CP/M or DOS… it had multiuser and networking and virtual memory.
What CP/M did have was open source. BSD then had open source but you had to pay for a source licence. DOS never had open source. I always believed IBM went to DOS because of that… I dont believe the story.