How often can I castle? I am learning to play chess on my computer. I have learned approximately all the rules but one rule stays vague for me thus far.  

My questions are clear, though. I am putting them separated below with some little additions.


This is simple. How often can I castle? One time, two times, x
times or till the end? I know that it can be executed if a rook and
king are at their original places. 
If I am allowed to castle one time, does that imply that I can make it two times because number of rooks for each player is 2?
FIDE Laws of Chess:


  3.8.b.1. The right to castle has been lost: a) if the king has already moved, or b) with a rook that has already moved.


Emphasis mine.