Xcode is a comprehensive toolset for the development, management, and maintenance of software products that run on the Apple OS X and iOS platforms. It includes an IDE, compiler, debugger, and numerous other tools. Xcode also bundles the OS X and iOS Software Development Kits (SDKs) that comprise the Cocoa and Cocoa Touch frameworks. You have been using Xcode to develop and run the example applications presented throughout this book, so by now, you’re already familiar with several of its basic features. In this appendix, you are going to “look under the hood” to explore some of Xcode’s key features in depth. Specifically, you will examine the key concepts that form the foundation of Xcode and, by doing this, become more familiar with some of its key tools.