MS-DOS was stolen from Digital Research's CP/M.
Story goes one of bills mates took CP/M binaries and changed the
strings and strip features out. Bill then took this software from his buddy and gave him a job at Microshaft in return. All totally legit…
Bill then sold this to IBM as PC-DOS, but billy boy left one string in the binaries which said "(C)Digital Research" woops!
IBM didnt care and bought it anyway. Digital Research came out with a compatible and better dos called DR-Dos and even a window system called Gem Desktop.