The '''[Microsoft Windows] [API]''' provides a set of functions that are generally supported on both 32 and 64-bit Windows . ** Documentation ** [http://msdn.microsoft.com/en-us/library/hh920508%28v=vs.85%29.aspx%|%API INdex] : The official reference ** Description ** Originally called the [Win32] API , the name Windows API its roots in 16-bit Windows and its current support of 32 and 64-bit Windows . Tk and Tcl use the Win32 [API] to access [operating system%|%OS] functions and draw on the screen. [[elaborate on how it can be used for many other purposes and how Tcl uses it]] <> API | Microsoft Windows | Porting