Many people do not even remember phone numbers anymore. Instead, cell phone users rely on the contact information stored in their phones. The iPhone allows users to save contact information and add it to an application called "Contacts." Although this is extremely convenient for many users, it is important to back up that data in another place just in case something happens to your iPhone. You can transfer contact data from your iPhone to the address book that comes with your Mac computer using iTunes.
Plug your iPhone into your Mac computer using the iPhone's USB connection cable.
Wait for iTunes to recognize that you have added a device. Click the iPhone icon once your iPhone appears under "Devices" in the left column of iTunes.
Click the "Info" tab located across the top of iTunes. This opens a screen that allows you to manage your contacts.
Select the check box next to "Sync Address Book Contacts."
Choose to either sync "All Contacts" or "Selected Contacts." If you choose "Selected Contacts," you need to click the check box next to the contacts you want to add to your computer.
Click the "Sync" button and contacts from your iPhone are added to the "Address Book" application on your Mac. They are also automatically added to your Yahoo or Google account if you chose that additional option.