The Starting point

Code Listing 1. The main() method in Objective-C programs

Figure 1. The annotated main method.

The import

Code Listing 2. Importing UIKit

UIKit Framework

Figure 2. The UIKit.framework from Xcode. The header files that are part of the framework are shown on the left. The contents of UIKit.h file are shown on the right.

UIKit Header File

Code Listing 3. The header file UIKit.h. As you can see the header files for UI element classes are here: Accelerometer, Alert, Application, Button, Color, Date Picker, Scroll View, Slider, and so on.

Need for UIKit.h in main.m

The main() signature

Code Listing 4. Signature of the main() method

The arguments

Code Listing 5. Finding the values of argc and argv[0] of a simple iPhone application from GDB. The location in argv[0] points to a folder for iPhone Simulator

Auto Release Pool and memory management

Code Listing 6. The autorelease pool

Code Listing 7. Autoreleasing an object

Main (UIApplicationMain) from the CocoaTouch framework

Code Listing 8. UIApplicationMain() method

Code Listing 9. Declaration of UIApplicationMain() method in its header file