Apple recently launched the new Xcode and simulators for development. Included is the new iPhone 5 called Retina 4 — simulator. It functions in the same was as the original — now called Retina 3.5. You may have noticed that
right away, your app appears letter-boxed even if you are using the full bounds of the screen: UIScreen mainScreen bounds or similar.
Read More - http://tech.xtremelabs.com/supporting-the-iphone-5-display-height/