The Microsoft Foundation Class Library provides support for Multiple Document Interface (MDI) windows programs with the base window classes CMDIFrameWnd and CMDIChildWnd. To create an MDI program, you can derive your main frame window class from CMDIFrameWnd. You derive child windows from CMDIChildWnd. The derivation of these window classes is the same as described for normal frame windows earlier in this chapter. The rest of this section describes some of the special situations that you must allow for in MDI programs.