> Can someone actually explain to me what Cygwin does internally? Doesn't Windows already implement POSIX?.
Used to. Subsystem for UNIX Applications is now deprecated.
Cygwin runs on top of Win32, and its library functions call into Win32. Thus, it is strictly a compatibility layer.
Whereas SUA runs alongside Win32 and does not depend on Win32 APIs. Thus, it is theoretically a replacement for Win32, for people who wanted to run a UNIX environment on top of the NT kernel. Practically, however, it was used primarily for application porting.
Used to. Subsystem for UNIX Applications is now deprecated.
Cygwin runs on top of Win32, and its library functions call into Win32. Thus, it is strictly a compatibility layer.
Whereas SUA runs alongside Win32 and does not depend on Win32 APIs. Thus, it is theoretically a replacement for Win32, for people who wanted to run a UNIX environment on top of the NT kernel. Practically, however, it was used primarily for application porting.