Microsoft's Unix derivative, Xenix, was a big influence on DOS 2.0, in particular the concept of directories, path name syntax, and replacing the CP/M-derived F

Microsoft's Unix derivative, Xenix, was a big influence on DOS 2.0, in particular the concept of directories, path name syntax, and replacing the CP/M-derived FCB API for file I/O with Unix-style file handles. That influence endures all the way from DOS 2.0 up to Windows 11. People talk about Windows NT being influenced by OpenVMS, via Dave Cutler – the influence is very obvious in some areas (e.g. asynchronous IO), but path name syntax is one area in which Windows is much more influenced by Unix than by OpenVMS (even considering warts such as drive letters, support for backslash instead of forward slash, and reserved file names such as NUL and CON.)