This class inherits directly from the TWINDOW class, so all window 
  messages are handled. 
  
  TMdiChild windows have a reference of their client window in the
  instance var ::oWndClient, and the client window object keeps
  a reference to all child windows in the instance array ::aWnd

  For a more detailed informations about the client window please press
   Related Topics:  and select  DEFINE WINDOW MDI