Dead locks

Hello
This question isn't about deadlocks, instead, it's about something I've been wondering because of a program I'm doing
thatuses locks. 
My progrm uses begin and commit (or rollback) and locks a table in exclusive mode. What'd happen if the program
unexpectedlydied? How would the database recover from a lock without a commit or rollback? Would the database release
thelock automatically, would it be in deadlock or would I have to release it by hand, and if so how? 

Cheers

Aristide