The pattern has two or three windows of the previously discussed or developed window class. The pattern has a control object which controls the windows. The pattern has the previously discussed window class and a specialized window class. The pattern also has a control object which now controls the special windows. In the container there are also entities.
Windows are the interfaces to the entities.
It is very important to show and develop all details. The source code can be made in 3GL or 4GL languages, in pure or hybrid object-oriented languages. It is better to use pure OO language though to force the student to use OO technique. Using a framework, the control, interface and container classes are ready and reusable.