How to back up the iphone4s address book? Need a detailed explanation, thank you!

Just use the export address book in itunes.

If outlook is installed on your computer, please connect your phone to itunes.

It will display the basic information of your mobile phone, and then the second message, which has a function of exporting the address book. You can select it and click on the lower right corner to synchronize.

Then you open outlook to see if there is any information in it. If there is, it is successfully exported.

After emptying the phone, you can import it back to the phone with the same content as above.