The first decision to communicate

The first decision to communicate to AppWizard, as shown in Figure 1.2, is whether your
application should be MDI, SDI, or dialog based. AppWizard generates different code and
classes for each of these application types.
 The first step in building a typical application with AppWizard is choosing the interface.
The three application types to choose from are as follows:
l A single document interface (SDI) application, such as Notepad, has only one
document open at a time. When you choose File, Open, the currently open file is
closed before the new one is opened.
l A multiple document interface (MDI) application, such as Excel or Word, can open
many documents (typically files) at once. There is a Window menu and a Close item
on the File menu. It's a quirk of MFC that if you like multiple views on a single
document, you must build an MDI application.
l A dialog-based application, such as the Character Map utility that comes with
Windows and is shown in Figure 1.3, does not have a document at all. There are no
menus. (If you'd like to see Character Map in action, it's usually in the Accessories
folder, reached by clicking Start. You may need to install it by using Add/Remove
programs under Control Panel.)