Two subsystems for POSIX, really. There was the original POSIX subsystem[0] that shipped in NT 3.1 thru 4.0, and the third-party OpenNT that became Interix[1] a

Two subsystems for POSIX, really. There was the original POSIX subsystem[0] that shipped in NT 3.1 thru 4.0, and the third-party OpenNT that became Interix[1] after Microsoft purchased it. [0] https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem [1] https://en.wikipedia.org/wiki/Windows_Services_for_UNIX https://en.wikipedia.org/wiki/Windows_Services_for_UNIX