Well, I'm electronic engineer and I had quite a difficult time learning microprocessors at university. Actually i didn't have any clue for the first 6 months of the course especially about interrupts or timers and I'm no thicky. But eventually it all sank in very well.
So Waqar is an archetict and looks like he is very interested in the subject and doing well so far with all the disappointed answers he is getting.
Best of luck Waqar and keep trying for one day it will all come to you and you would say that this is very easy stuff!
Mahmood