>and not been able to find any concrete evidence to support the existence of any other "Windows subsystem for X" subsystems. They were originally known as Micr

>and not been able to find any concrete evidence to support the existence of any other "Windows subsystem for X" subsystems. They were originally known as Microsoft Subsystems[1][2] and encompassed Win32, POSIX, and OS/2. This was followed by Windows Services for UNIX along with the demise of POSIX and OS/2 subsystems, which was subsequently succeeded by Windows Subsystem for Linux. Yes, this means Win32 is to this day a subsystem of Windows NT. [1]: https://en.wikipedia.org/wiki/File:Windows_2000_architecture.svg https://en.wikipedia.org/wiki/File:Windows_2000_architecture... [2]: https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem