A frozen iPhone does not respond to your input. Two types of recovery methods are available: reset or restore. Resetting the iPhone does not delete data, but a restore of the firmware restores it to original factory settings, causing you to lose data. The option to reset or restore can be made after you back up your data to prevent data loss.
Before resetting or restoring an iPhone, you should back up the data. Backing up data avoids data loss if you restore the phone to original settings. The back up process is available from the "iPhone" icon in iTunes. Hold the "Ctrl" key and right-click the "iPhone" icon. Choose "Back Up" to save all of your text messages, pictures and contact numbers.
To reset the iPhone, hold the "Sleep/Wake" button and the "Home" button together. Keep the buttons pressed until you see the Apple logo on the phone. The phone resets. This procedure does not delete any data, and it is used if your phone freezes or is not responding. In some cases, if you cannot reset the phone manually, do not charge the phone. When the battery runs out of power, the phone resets. You must recharge the battery again.
If your iPhone is restored to original settings, you can restore the backup data to prevent data loss. Plug the phone into your computer. iTunes automatically starts. Hold the "Ctrl" key down and right-click the "iPhone" icon in iTunes. Click "Restore from Backup" to restore all of your data back to the phone.
Always reset the iPhone if it freezes or is not working properly. This is the first step when troubleshooting the phone and can prevent data loss. Remove iPhone applications in case any installed applications are causing the issues. Restoring the phone should only be used when the phone is not responding even after a reset.