As you know, VA Smalltalk already provides many parts. Each of these parts has a predefined public interface. When you work in the Composition Editor, you connect parts to other parts using their public interface features. The term public interface means the attributes, events, and actions on the part's pop-up menu. The reusable parts that you create must have a defined public interface, so they can be used like any other VA Smalltalk part. The Public Interface Editor is used to define the attributes, events, and actions of the public interface for your part.

Now switch to the Public Interface Editor. The Public Interface Editor is a notebook with four pages. The first three notebook pages are used to edit your part's interface. You'll learn about the fourth page, the Promote page, in Building visual parts.