Up until now, you have been learning how to develop MFC programs using two fundamental classes of the MFC architecture: CWi nApp and CFrameWnd. The CWi nApp class encompasses the thread and message handling portion of your application. The CFrameWnd class encompasses the window for your application. This chapter discusses two more classes that play an essential role in many MFC applications: CDocument and CVi ew. These two classes form the basis of the document/view architecture.