Main windows are standalone windows that are independent of all other windows. They can overlap other windows and can be overlapped by other windows.
You use a main window as the anchor for your application. The first window your application opens is a main window unless you are building a Multiple Document Interface (MDI) application, in which case the first window is an MDI frame.
For more on building MDI applications, see Application Techniques.
Define your independent windows as main windows. For example, assume that your application contains a calculator or scratch pad window that you want to have always available to the user. Make it a main window, which can be displayed at any time anywhere on the screen. As a main window, it can overlap other windows on the screen.
