An unresponsive iPhone can put a damper in your day, especially if you are in the middle of something important. Luckily, there are a few ways to get your frozen iPhone up and running in just a few minutes. If worse comes to worse and you cannot successfully quit, restart or reset your iPhone, take the phone to an Apple store or send it to Apple in the mail for repair help.
Force Applications to Close
Sometimes when you are using an application that requires a lot of memory, such as a game with complicated graphics, your iPhone will freeze. This is especially likely to happen if you are running another program in the background, such as a radio application. The first thing to try when you encounter a frozen application is forcing the application to quit. Accomplish this process by holding down the "On/Off" button at the top of your phone until a red slider appears. Don't touch the red slider -- rather, press down on the home button until the application closes and your screen becomes responsive once again.
Restart the iPhone
If you are unable to force an application to close, or your device freezes while on the home screen, try to restart the phone. Restarting an iPhone is simply the process of turning the phone off and then back on again, which will typically fix the problem of a frozen screen. To restart your iPhone, hold down the "On/Off" button until the red slider appears, and then slide your finger across the slider to power down the device. After a few seconds, hold down the "On/Off" button until the iPhone turns on again.
Reset the iPhone
On rare occasions, your frozen iPhone will not respond to your attempt to restart. In that instance, you can try to reset the device. Resetting an iPhone is the equivalent of holding down the power button on a computer so that it is forced to shut down without closing out programs like it normally does. To reset an iPhone, just hold down the "On/Off" button and home button until the Apple logo appears and then disappears -- the process takes about 10 seconds. Pressing the "On/Off" button will turn your device on again.
When your device freezes while connected to a computer and in the middle of an update or restore, you should disconnect the iPhone on the iPhone's end of the USB cord. Leave the USB cord plugged in to your computer, and hold down the "On/Off" button on your iPhone until the red slider appears. Once you slide the red slider over, your iPhone will shut down. As you reconnect your device to the USB cord, hold down the home button, and continue to hold down the button until you see an iTunes message on the iPhone screen. Your iPhone is now in recovery mode and should update without problems.