A view controller functions as the root view screen for the SMP101 mobile application.
When you create the user interface, you assign a target action to a control object—in this example a, Subscribe button that sends a message (the action) another object (the target) in response to a user event, for example, a touch on the button. The view controller manages and configures the view.
In Xcode, you can create the view controller by creating a new file using the UIViewController subclass. Select With XIB for user interface. Xcode creates the corresponding .h, .m, and .xib files.