I think storminator and quasqueston have hit it on the head.
It sounds like bunches of you played where the DM wouldn't tell the players the AC. When that happens in 2e, it slows down the game, because you have to do math on both sides of the <= sign. Which is why in all the games I played, we just gave out the AC. In about 1 swing, a fighter's gonna know how tough it is to hit the guy anyway, so why dork around making the math harder. (one house rule was, you don't get told the AC until you commit to attacking the bad guy, no take backs once you find out he has a -10 AC and you have an 15 THAC0).
Short of it is, all players had the THAC0 for each weapon, by each weapon on their char sheet. An attack went by as follows:
Player: I attack the goblin
GM: AC is 7
Player: need a 12 to hit (rolls) got a 13
Player: (rolls d6) I do 5 damage
GM: you jab your sword under his, and jab the goblin in the ribs, he winces in pain and brings his shield in tighter
Doing the secret AC method in 2e slows the game down for little benefit. The GM or the player would have to modify the result to figure out which AC was hit, if the AC was not automatically told. I prefer to let the players do the work and spread the workload (figure 1 round, 6 players, they each have to do the math once, versus making the GM do math 6 times, plus his own monsters).
In 3e, the math requirements are similar, but it naturally allows the DM to protect the AC, without any work on either side's part. This is why the AC reversal in 3e is better, as it gives GMs the best of both worlds, the players do their own math AND they can keep AC secret.
Janx
I should think it would be weird not to complain about it.
