When I create a new single view application in Xcode 4.6 using storyboard, we can see that the main function creates a new application using the application delegate like th
Look at your Target settings for the Project
Notice the Main Storyboard setting.
If you wanted to do this in code yourself, you would do something like.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:[NSBundle mainBundle]];
UIViewController *vc = [storyboard instantiateInitialViewController];
// Set root view controller and make windows visible
self.window.rootViewController = vc;
[self.window makeKeyAndVisible];
return YES;
}