This questions was asked a couple of days ago. The emailer wanted a way to backup there address book contacts for backup purposes. The problem with this exporting process on Address Book is that it takes a long time to export the cards individually . This is a big problem since we never have a lot of time. There is a semi-simple way to export Address Book Contacts, without it taking all day.
The first step is open address book go to File > Export > Address Book Archive. When you hit OK, this will export every single vCard file in your address book and place it in a special file. This special file contains all of your contacts.
You can then save this file somewhere safe and you are done. If you want to look inside the file hit “Show Package Contents”. Inside this file you can find all of the meta data associated with the contacts, plus all of the images and other bits and bobs needed to build a contact. Unfortunately you can’t use this files in other programs. The .abcdp (I am sure the programmer was bored) in other apps. It would have been better if the files were exported as vCards, make life a lot more useful.