The Pirc, KID, and KIA all have similar structures. If you become expert at one, will you become expert at all three?

I would say not because there are different lines to deal with in each three, however if you are an expert in one, I would think that you would be able to play the other two decently.

no, differnt continuations and different motives.

No, especially the KIA, because you have an extra tempo. You'll be familiar with the others, but not as expert as you are on one. The Pirc has many traps to memorize, so you won't be as good in it as you are in the KIA.

I understand that the KIA is an opening system, and so you are dealing with different move orders, the extra tempo as white etc. When I first started to study openings, I thought the Pirc was just some fancy KID against e4, but now I see that you have to take into account other factors that make e4 different from d4. I would like to thank you all for your help in making me study these openings more deeply. There is more under the surface than just the similar structures you see at first glance. Thanks again.

i use all 3. and i am equally bad at all of them.

will anyone post diagrams in this forum so I can see what they are?

Now you can understand my confusion wnen I first saw these diagrams

If you want a brief but clear discussion of the similarities and differences between the KID and the pirc, check out Watson's Mastering the Chess Openings, Vol. I, Chapter 14 on the pirc.  Watson also has very good chapter on the KID in Vol. II.   This two volume set is a wonderful resource if you are trying to get the 'sense' of any major opening frequently used today on the GM level.

Watson does not, however, discuss the KIA, since he isn't trying to be exhaustive.  His set does not replace (say) MCO-15 so much as compliment it, but only for the main lines in today's GM play.  

A great introduction to the KIA, however, is "Starting Out: King's Indian Attack."  You pretty much can't go wrong with the Everyman Chess Starting Out series if you want to get aquainted with a new opening and learn the basic ideas behind each of the major lines in it.

I agree with you about the Starting Out series of books. I own a few and I think they give a wonderful basic introduction to the chess openings. I have the one on the King's Indian Attack. I plan to get Watson's books soon. Thank you for your help on this subject.