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MFC Application Architecture Classes
Classes in this category contribute to the architecture of a framework application. They supply functionality common to most applications. You fill in the framework to add application-specific functionality. Typically, you do so by deriving new classes from the architecture classes, and then adding new members or overriding existing member functions.
Application wizards generate several types of applications, all of which use the application framework in differing ways. SDI (single document interface) and MDI (multiple document interface) applications make full use of a part of the framework called document/view architecture. Other types of applications, such as dialog-based applications, form-based applications, and DLLs, use only some of document/view architecture features.
Document/view applications contain one or more sets of documents, views, and frame windows. A document-template object associates the classes for each document/view/frame set.
Although you do not have to use document/view architecture in your MFC application, there are a number of advantages to doing so. The MFC OLE container and server support is based on document/view architecture, as is support for printing and print preview.
All MFC applications have at least two objects: an application object derived from CWinApp, and some sort of main window object, derived (often indirectly) from CWnd. (Most often, the main window is derived from CFrameWnd, CMDIFrameWnd, or CDialog, all of which are derived from CWnd.)
Applications that use document/view architecture contain additional objects. The principal objects are:
An application object derived from class CWinApp, as mentioned before.
One or more document class objects derived from class CDocument. Document class objects are responsible for the internal representation of the data manipulated in the view. They may be associated with a data file.
One or more view objects derived from class CView. Each view is a window that is attached to a document and associated with a frame window. Views display and manipulate the data contained in a document class object.