@mint @nom And CP/M had a lot of influence from TOPS-10, which both Microsoft cofounders also used while they were at Harvard. The novel features in DOS 2.x (hierarchical filesystems etc.) were directly inspired by Unix and OS/2 later forked off of DOS in order to implement a preemptively multitasking multi threaded operating system with a graphical user interface that could directly compete with Unix features wise without being beholden to AT&T or their licensing department.