Now that you have learned how to add widgets to a screen and position them where you want, let's turn our attention to the third component of GUI programming.

This addresses the question of how to make widgets functional.

Making widgets functional involves making them responsive to events such as the pressing of buttons, the pressing of keys on a keyboard, and mouse clicks. 

This requires associating callbacks with specific events. Callbacks are normally associated with specific widget events using command binding rules, which are discussed in the following section.