Another Armor Question

Maybe this has already been posted, but I couldn't find it. If so, I apologize in advance. Anyway, I was playing around with armor the other day trying get the best AC. I put on a Daedric shield just to see what it would do, knowing that I would have to take it off when I equipped my Daedric Dai-Katana. Well intead of unequipping my shield, I just switched over to the weapons and equipped the sword. The shield disappeared from the picture, but the AC stayed the same. So my question is, do you only lose the blocking ability when using a two-handed sword with a shield equipped or do you also lose the AC?

i think u just lose blocking ablilty, cuz u still have it "on" you but ur just not using it