OK, OK, I admit. I saw the Player Character sheets I downloaded at DragonsFoot all listing a place to record "To Hit Armor Class 0" (THAC0) and said "WTH?"
I'm sorry I missed it back then, apparently, the groups I played in just hadn't caught up to AD&D 2nd Ed yet.
Because, I find out after doing some DDG time (DuckDuckGo=a search engine that doesn't steal your data or try to sell you something. I highly recommend it) that it was introduced in AD&D 2nd Edition as a way to replace the attack tables and matrices from 1st ed. Supposedly a way to "simplify" the combat/melee process.
Now after reading up on it a bit, I get it. I can see the appeal for some people who don't like looking up stuff on tables (though with enough usage, you start to remember the tables after awhile).
At the same time, I don't use it in my games and I don't plan to use it either.
Consider me a "die hard" (get it? "die, dice?" 1st edition AD&D aficionado.
I needs me some tables.
I don't and won't get into the uber-geek behavior of knocking or arguing with others over whether they use THAC) or not. Frankly, I don't care. To each their own I say. If it's their game, then it's their rules I say.
For those who, like me, still don't "get" what THAC0 is about, here is a link that I think does a good job of making it all very clear.