We are getting to some advanced stuff now. In this lesson I am not going to go in depth at all. I will just give you a flavor of the structure of a SDI (single document interface) and a MDI (multiple document interface) application. In the last lesson we will build a SDI application and you can see the nitty gritty there. The SDI application is typically used when you intend to work with only one data set at a time. For instance, the program notepad.exe is a SDI application. Netscape is also an SDI application. At any one time, there is only one document open at a time. Word for Windows and the VC++ developer studio are MDI applications. In these you can have several documents opened at once. This is particularly useful when you want to cut and paste between documents. Another use for MDI applications is to have one document, but several different views open that view the data differently. A graphing application comes to mind where in one window you have a spreadsheet-like data list,...