The NT kernel was created with a POSIX layer (along with os/2). https://en.m.wikipedia.org/wiki/Microsoft_POSIX_subsystem https://en.m.wikipedia.org/wiki/Micro

The NT kernel was created with a POSIX layer (along with os/2). https://en.m.wikipedia.org/wiki/Microsoft_POSIX_subsystem https://en.m.wikipedia.org/wiki/Microsoft_POSIX_subsystem Microsoft had previously been the largest AT&T UNIX licensee with Xenix sales on the TRS-80 model 2, so they were familiar with the need.