You must have noticed lots of visible changes in OS 3.0 but there are many hidden changes. One of them is Forcely Quit app in iPhone. Sometimes an application(from the App Store or even like Safari) can start taking up so much memory that it starts to decrease the performance of the device. In OS 2.X.X we used this trick “ Press and hold the home button. Holding this home button for about 10 seconds will force that app or game to quit. ” But for iPhone OS 3.0 and iPhone 3G S there are certain changes.
If something isn’t working right, restarting, force quitting an application, or resetting iPhone will likely solve the problem. Force quitting can be good avenues, not only to exit a misbehaving or frozen app. It’s also a good practice to quit background apps like Safari and Mail, which take up precious memory, especially before starting a game.
How to Force Quit an App : To force quit an application in 3.0, press and hold the sleep/wake button until the slide to power off screen appears, then press and hold the home button until the application quits (about six seconds).
How to Reset iPhone : Press and hold the Sleep/Wake button and the Home button at the same time for at least ten seconds, until the Apple logo appears.
How to Restart iPhone : Press and hold the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPhone. To turn iPhone back on, press and hold the Sleep/Wake until the Apple logo appears. If you can’t turn off iPhone or if the problem continues, you may need to reset. A reset should be done only if turning iPhone off and on doesn’t resolve the problem.