I\'m developing the app to work both on iphone4 and iPhone 5. I\'m using the following code to get the screen size
CGRect screenBounds = [[UIScreen mainSc
On the simulator make sure you have set to iPhone (Retina 4-inch). You can do this by going simulator menu at the top go to Hardware>>Device>>iPhone (Retina 4-inch) that will change the phone simulator to the iPhone 5 version.
If this is set then you may need to add a launch image for the iPhone 5. Default-568h@2x.png
if this is missing it will not launch in iPhone (Retina 4-inch).
I have also answer another question here that may help.