Computing passing yards

Question
When a pass is completed, is it figured from:

1. From the line of scrimmage or from where the pass was thrown?

2. And... from where the pass is caught or from where the ball is downed after the catch?

Answer
Passing yards are computed from the line of scrimmage (a bit unfair considering most passes are thrown deep in the pocket) and where the ball is downed after the catch.  This now wants me to look into how they can give someone credit for more than 100 yards on an INT return.