Downloaded DS game Friend Codes

Im sorry if this is a topic elsewhere but i was unable to find anything so i thought i'd ask here.
If i download a Ds game how is my unique friend code created, is every one that downloaded the game going to have the same code or will they all be different.
Im asking because i'd like to trade with my friend in pokemon but it hasn't actually came out where i live yet so im wondering whether he'll be able to find me if im using a friend code found on a downloaded game.
Thanks in advance for the help guys.

 

Everyone's is different.

 

Cool thanks for the help.