Further into history, Microsoft used to be heavily into Unix. Quoth https://en.wikipedia.org/wiki/Xenix https://en.wikipedia.org/wiki/Xenix : ''' Microsoft om

Further into history, Microsoft used to be heavily into Unix. Quoth https://en.wikipedia.org/wiki/Xenix https://en.wikipedia.org/wiki/Xenix : ''' Microsoft omitted multiuser support from its own MS-DOS operating system because Xenix had it.[29] The company planned to over time improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the 68000, Z8000, and LSI-11; they would be upwardly compatible with Xenix, which Byte in 1983 described as "the multi-user MS-DOS of the future".[30][31] Microsoft advertised DOS and Xenix together, listing the shared features of its "single-user OS" and "the multi-user, multi-tasking, UNIX-derived operating system", and promising easy porting between them.[32] '''