Not to argue the merits or lack thereof of UI theorists and their, er, highly fertilizing output, but... You are spouting BS. DOS has introduced hierarchical filesystems in 2.0, which was essentially a v7 lookalike welded on top of CP/M clone. It *was* a Unix clone, wrt file-related interfaces. I suggest you to look at the file-related APIs in DOS 1.0 - those are copied from CP/M. FCB junk. 2.0 and later had normal file descriptors, chdir(), pathnames, etc. FS layout had been different (and v7 filesystem would be very painful on floppies with not enough RAM to cache the metadata), but the idea itself had not been independently created - it had been an explicit copy. I'm not familiar with the history of MacOS interfaces, but I very much doubt that it had been independent development there. Hell, it wasn't independent on Unix either, but there it was more that the whole thing started around the work by the core Multics filesystem developers after Bell Labs had pulled out of Multics project.