This guide takes a step-by-step approach to teaching developers how to build real graphics applications using Cocoa. By showing the basics of an application in one chapter and then layering additional functionality onto that application in subsequent chapters, the book keeps readers interested and motivated. Readers will see immediate results, and then go on to build onto what they've already achieved. The book is divided into four major parts: Part I introduces the Mac OS X graphical user interface (Aqua) from a developer's point of view, Cocoa developer tools (such as the Interface Builder, Project Builder, and gdb debugger), object-oriented concepts, the Objective-C language in which Cocoa is written, and the basics of Cocoa programming itself; Part II focuses on building the first complete application, calculator, a simple four-function calculator. The chapters in this part of the book extend the application, piece by piece, by introducing such features as nibs, icons, delegation, resizing, events, and responders. Part III focuses on building an application called MathPaper, which is similar to a word processor but which instead solves mathematical expressions the user supplies. The chapters in this part of the book extend MathPaper by developing both the front and back ends using a variety of Cocoa classes and methods. They introduce Cocoa'sdocument-based architecture, tasks, pipes, Rich Text format, handling document files, and using Quartz to draw in windows. Part IV focuses on building the GraphPaper application, a more complex multithreading application that graphs mathematical functions in multiple dimensions and that uses mouse-over capabilities to identify graph points. The chapters in this part of the book add more advanced Mac OS X features such as multithreading, colour, mouse events, zoom buttons, pasteboards, services, preferences, and the defaults database.