DOS programs compiled with the /Mq compiler option have a limited Windows user interface, including a standard menu bar, standard Help (for the QuickWin features), and a client (or application) window with a child (document) window for the C input/output streams, stdin, stdout, and stderr. The /Mq compiler option defines the _WINDOWS constant, declared in the Windows version of STDIO.H. For more information, see Chapter 8 in the Programming Techniques manual.