AppWizard generated the CEx03aView view class, and this class is specific to the EX03A application. (AppWizard generates classes based on the project name you entered in the first AppWizard dialog box.) CEx03aView is at the bottom of a long inheritance chain of MFC library classes, as illustrated previously in the Browse window. The class picks up member functions and data members all along the chain. You can learn about these classes in the Microsoft Foundation Class Reference (online or printed version), but you must be sure to look at the descriptions for every base class because the descriptions of inherited member functions aren't generally repeated for derived classes.
The most important CEx03aView base classes are CWnd and CView. CWnd provides CEx03aView's "windowness," and CView provides the hooks to the rest of the application framework, particularly to the document and to the frame window, as you'll see in Part III of this book.