Unlock code for my car radio

Hello, i have seen this problem on my car before when ever the battery got disconected or gone dead. stereo antitheft loc is on and some times if you try to put to many wrong codes in unsucsesfully i had to turn key on for one hour and then the correct code entered.its usually in owners manual under anti-theft stereo loc.they should have wrote the code in there manualy when the car was new.i took mine to a car audio dealer and got the code from a couple of digets that showed up on the radio when he held on to two buttons at the same time and called for the codes that were programed in.this is just a helpfull guide to a related problem i had in a grand prix i bought used and put a new battery in and had no code.i live in louisville ky. and went to a after market dealer on dixie hwy. and it costed about 60 dollars.but since i tryed the wrong code more than three times he had to leave the ignition on for an hour before it would unlock.it worked and i wrote the code down.its usually a 3-4 number code.