Another use for scripts is to enable the user to run part of the code without launching the whole application. You will seldom use either of these techniques. Introducing the Library Level A library is a good place to put code that you need to call from multiple forms. For now, just remember that a library is a place to put code that is shared among forms. The init method occurs first and is the first place to consider placing code when you are placing code at the form level.
All events go through the form's prefilter, and external events can go to the form twice.
First, the event is prefiltered, and then it is sent to the target and can bubble back up to the form. If you want to intercept another object's event, use the form's prefilter. Think of the prefilter as a special level and the else part of the form's if statement as the form level. For example, if you want to do something after the form is opened, use the else portion of the form's built-in arrive method. If you want to trap for an error so that you can do something in addition to the built-in behavior, use the form's else portion of the error method.