An application uses several types of windows in addition to its main window, including controls, dialog boxes, and message boxes.
A control is a window that an application uses to obtain a specific piece of information from the user, such as the name of a file to open or the desired point size of a text selection. Applications also use controls to obtain information needed to control a particular feature of an application. For example, a word-processing application typically provides a control to let the user turn word wrapping on and off. For more information, see Controls.
Controls are always used in conjunction with another window — typically, a dialog box. A dialog box is a window that contains one or more controls. An application uses a dialog box to prompt the user for input needed to complete a command. For example, an application that includes a command to open a file would display a dialog box that includes controls in which the user specifies a path and filename.
A message box is a window that displays a note, caution, or warning to the user. For example, a message box can inform the user of a problem the application has encountered while performing a task.
Dialog boxes and message boxes do not typically use the same set of window components as does a main window. Most have a title bar, a window menu, a border (non-sizing), and a client area, but they typically do not have a menu bar, minimize and maximize buttons, or scroll bars. For more information, see Dialog Boxes.