In the first part of this chapter, we added a second nib to our Calculator application, and in doing so provided that application with an About box. Using multiple nibs is a good way to enhance the performance of your program; with multiple nibs, objects are created only when they need to be used. In the second part of this chapter, we learned how to create a Cocoa icons file and how to make this file the application icon for our Calculator. Finally, we saw how to display this icon in our About box.

In the next chapter, we’ll learn about delegation, a powerful tool for controlling the functionality and extending the behavior of the Cocoa AppKit objects.