This chapter may not have been as much fun as the previous ones, because we didn’t show you any cool Interface Builder techniques, any nicely integrated features of Project Builder, or even any powerful AppKit classes. However, we did learn a bit about the Darwin working internals of Mac OS X, things that every serious Cocoa programmer should know. There’s a lot more to learn about Darwin, but we’ve learned enough to go on to our next (more sophisticated) example, MathPaper, in the next chapter.