Freezes and crashes are generic iPhone problems that can occur in any iPhone software, from Safari to Maps. In this excerpt from Take Control of Your iPhone, I cover iPhone freezes and crashes, explaining what’s going on, how to recover from them, and how to avoid them.

Handle Freezes

While running any of iPhone’s applications or widgets, your iPhone may suddenly stop responding to your touchscreen gestures. Even pressing the Home button produces no effect. Typically, any display activity, such as a Web page that is loading or a video that is playing, halts as well. When this occurs, the iPhone software has “frozen.”

Another symptom of a freeze is that the iPhone screen remains black, as if it is not turned on (although this symptom may also be caused by a “dead” battery).

To unfreeze an iPhone press and hold down the Home key for about six seconds. If this works, you are returned to the Home screen, with (hopefully) everything working again. If a force-quit fails to unfreeze the application, try further actions as described ahead in this section (begin with Restart, below).

Handle Crashes

When you’re working with an iPhone application or widget, the iPhone may suddenly toss you back to the Home screen. When you return to the program you were using, you may further find that some of your recent changes have been lost. For example, a Web page that you had closed may now be back. When this occurs, it means the iPhone software has crashed.

After being dumped back Home, you should simply return to what you were doing and hope the crash does not recur. If the same crash does happen again (and sometimes again and again), try restarting your iPhone (described next). This often helps because many crashes are caused by a combination of events that won’t reoccur in exactly the same way after a restart.

Restart

To restart an iPhone, press and hold the Sleep/Wake button (the physical button at the top of the iPhone, next to the SIM card tray) until a red (and white arrow) slider (adjacent to the words “slide to power off”) appears on the screen. Drag the slider to power off your iPhone. Then press and hold the Sleep/Wake button again until the Apple logo appears. Wait a few seconds for iPhone’s startup sequence to finish, and you should be back at the Home screen.

While I refer to this procedure as a “restart,” some Apple documentation refers to it as a “reset.” I prefer “restart” both because it is consistent with the same action on a computer and because it avoids confusion with other meanings of “reset” for the iPhone.

Force Restart

If your iPhone is really confused, even holding down the Sleep/Wake button may have no effect. In such cases, you can generally force the iPhone to restart by holding down the Sleep/Wake and Home buttons simultaneously for around 10 seconds.

Although I have seen no official confirmation of this from Apple, I expect that the difference between a normal and a forced restart is that the former restart is more “graceful,” making sure that all files that should be closed before restarting have done so.