First off, Apple has issued a statement regarding the controversial Carrier IQ software. iOS 5 devices do not run the Carrier IQ software package (IQRD) and Apple will be completely removing all references to the software in a future update. Even without Carrier IQ, the iPhone can still send diagnostic and usage data to Apple daily to help Apple improve its products.
Apple has published iPhone user guides for several generations of iPhones. These support manuals can be viewed directly on your iPhone using the Apple iPhone in-browser user guide. This link will automatically display the manual that best matches your iPhone and operating system.
iPhone user guides are also released as PDF files which can be viewed on a computer or printed out for future reference. See a list of available user guides in PDF format below:
Airplane mode ensures your iPhone complies with airline regulations by shutting off all wireless signals from the device when boarding a plane to prevent interference.
To turn on airplane mode, navigate to Settings -> Airplane Mode -> ON. This will prevent cellular phone calls and data, Wi-Fi, GPS and Bluetooth signals from being emitted from your iPhone. When activated, an airplane icon appears in the status bar of your iPhone home screen.
The Unique Device IDentifier or UDID is a 40-character string composed from various hardware identifiers on iOS devices. The UDID will be unique on each device, and can be used along with app-specific user IDs to identify app-specific data on developers' servers. To find your UDID:
1. Connect your iPhone to the computer and open iTunes.
2. Make sure your iPhone is selected in the left menu and click the Summary tab.
3. Click your Serial Number and the UDID will appear. You can copy the UDID onto the clipboard by typing Command + C in Mac OS or Control + C in Windows.
UPDATE: iOS 6 users who are not interested in targeted ads can now limit ad tracking. Navigate to Settings -> General -> About -> Advertising -> Limit Ad Tracking -> ON.
Apple intends to use consumer data from iTunes to target your iPhone with specific advertising within apps. The iAd program has already launched, but if you're not interested in Apple using your data to find relevant ads you can opt out.