Let's Talk About THAC0

Legatus_Legionis

< BLAH HA Ha ha >
I grew up using THAC0, and have no problems with it.

"Thay-Ko"

I never had my players waste time filling out those THAC0 areas on the PC Sheet.

I do have a mini-sheet I use as a DM, where I have the players list their HP, alignment, AC, type of armour/shield (and bonuses), plus weapons used (and bonuses).


And I never allowed my players call out "I rolled X, I hit AC #, did I hit?"

I do require them to state "I rolled X, my hit roll is #". (with all PC modifiers).
We do use Critical Hits and Misses so a roll of 1 is always a critical miss, no matter how many modifiers a PC has.

I don't want my players to know that the actual AC is from whatever they hit. Especially if they know they can't hit it, then they will change tactics only because they were given the AC number.

Also, I modify the monsters/NPC's AC based on if you are the primary target/defense, or if you are the secondary attacker (can't bring sheild/dex to bear on multiply attackers, only the primary/first one, etc.).

And on the larger monsters, their AC varies on where on their body one is attacking, so having player 1 attack hits a certain AC, while player 2 has the same roll/attacked a different location and misses...

So leaving the math of THAC0 to the DM is best.

I also love it when a player who has a better "To-Hit" roll constantly misses and wonders how a PC with a lower THAC0 does hit, to finally realize only magical weapons can hit, or weapons with a +# or better... < HA Ha ha>
 

Hussar

Legend
Sacrosanct said:
Not asking you to buy into my anecdotes. I’m asking you to look at objective facts, like the character sheets having that info for the players since at least 1980, possibly earlier.

If we ARE going to use anecdotes, at least mine is supported by the official tools we had available at the time, whereas your anecdote depends on ignoring said official material. After all, why would a player ask the DM what AC they hit unless they ignored the character sheets available at the time that did that for the player?
Well, I'm not going to presume that a majority of groups actually used published character sheets, so, umm, I'll stick to the notion that my anecdotes are just as valid as your anecdotes.
 

Fenris-77

Explorer
Your anecdotes, my anecdotes, whatever. There are too many long time players here for personal anecdotes to carry weight in a conversation like this. However, since that's what we're doing, I've played with THAC0 innmore campaigns I can count, and worked at a FLGS for years with access to hundreds of other players, and THAC0 was never a point of contention or complaint, not once I can remember. People called their hits at AC and everyone went home happy.
 

cbwjm

I can add a custom title.
Never had an issue with thac0, generally we'd calculate all of the bonuses I to our thac0 so a 5th level fighter specialised in swords, with a 17 strength, and carrying a +1 sword would have sword listed with a thac0 of 13. Then you just roll the d20 and subtract it from 13 and call out which AC you hit, seemed easy enough back then. The main thing I liked about the changes in 3e wasn't so much the change from thac0 to BaB but the consolidation of skills and attack bonuses to a single d20+modifiers. Got rid of thief skills and merged them with all the other skills which was a massive bonus.
 

Azzy

Cyclone Ranger
Well, I'm not going to presume that a majority of groups actually used published character sheets, so, umm, I'll stick to the notion that my anecdotes are just as valid as your anecdotes.
My group never used an official sheet until early in 2e. However, by the time I got my first computer (a Tandy 1000), we made our own sheets in a word processor.
 

Umbran

Mod Squad
Staff member
Granted, I only played AD&D from about 1981 to 2000, but, hey, multiple countries and a couple of continents later, including players from lots of different countries, I'm not sure that I really buy your anecdotes.
Before you get even snarkier about it...

There are elements of rules that we are aware of, that sometimes out of tradition we don't use. Like weapon vs armor type tables. The fact that we didn't use them didn't mean we didn't know about them.

So, do you honestly think your players called out the modified hit totals because the thac0 numbers were actually secret from them, and they *couldn't* do the conversion, or because that was just how they did it, by tradition?
 

Harzel

Explorer
Ok, there's a bit of weirdness here for me. I started with 1e and some boxed set that unfortunately I have lost track of and have never been able to identify from my vague recollections. The only books that I ever had were 1e books and we had pretty much quit playing by 1989. However, when I look back at my old (homebrew) dungeon descriptions, they all list THAC0 for the monsters, and I've certainly 'always' known what THAC0 is. So did THAC0 get introduced prior to 2e in one of the Basic versions, or perhaps in Dragon magazine? I didn't realize this was an anomaly in my history until this thread.
 

CM

Adventurer
Started on it, never liked it, glad it's gone.

It's not intuitive for new players.
 

Harzel

Explorer
While I knew what THAC0 was, and I'm pretty sure I used it, and I seem to recall embracing it as an improvement over the tables, my memory is much too sketchy to remember exactly what the protocol was for players telling he what they had rolled. All that said, I would be astonished if anyone outside of a few geezers on ENWorld thought that BaB was not a vast improvement.

Of course, without a lot of research that no one would ever fund, it's not possible to be sure whether or why some people might have trouble wrapping their heads around THAC0. However, I will venture a guess as to why it has the 'reputation' of being 'complex' despite involving more or less the same arithmetic as BaB. First, I would guess that 'obscure' would be a better description of some people's negative take on it than 'complex'. Second, I would guess that this is a good example of an aspect of earlier D&D that was a barrier to entry for non-nerds. (Sure, there were lots of folks for whom THAC0 was 'no problem', the vast majority of whom I would conjecture were folks who were very facile with quantitative and abstract processes.) The source of the obscurity of THAC0 (or at least a major contributor), I think, is that the THAC0 value is defined by a hypothetical: it's the value you would need to roll if your target had AC0. Intuitively, to me at least, it is notably more difficult to understand (more obscure) how that plays into the to-hit calculation than the quantities involved in BaB - the dice roll, your to-hit bonus, and the target's AC - which are all defined in obvious ways by and related in obvious ways to the current circumstances.
 

Maxperson

Morkus from Orkus
We never had issues with THAC0 in any of our 2e games over the years. The math was just too simple to do for us to have an issue with it.
 

Lanefan

Victoria Rules
It says "adjusted to hit Armor Class." That clearly means you put down what you need to roll to hit the various armor classes after adjustments (modifiers). Seemed pretty obvious to us anyway, back then. I mean, that's what the words mean.
Problem with that was - and still is - those adjustments can change back and forth fifteen times within a single session!

Someone casts Strength on you - change adjustments, and again when it wears off
You're firing a missile instead of swinging an axe - change adjustments (unless your Str and Dex just happen to give you the same to-hit bonus)
Your axe is +2, your bow is +1 and your sword is +0 but +3 vs. Evil - change adjustments every time you change weapon and sometimes when you change opponent
Someone casts Bless for you or Bane against you - change adjustments, and again when it wears off

Writting down the unadjusted base I can see, but rewriting it every time the adjustments change seems like massive overkill. :)

So if I needed a 19 to hit an armor class 0, and I had a +1 modifier for strength and a +2 modifier for the magic weapon (that's why each weapon has it's own table)
Ah, that helps a bit. The sheets I've seen just have the one row for THACx.

Now the adjustments - for each weapon! - might only change six times a session. :)
 

digitalelf

Explorer
So did THAC0 get introduced prior to 2e in one of the Basic versions, or perhaps in Dragon magazine? I didn't realize this was an anomaly in my history until this thread.
THAC0 was first introduced to AD&D (1st Edition) as a usable game mechanic in 1983 with the module "UK3: The Sentinel" as an optional rule.

It latter appeared as an "official" part of the 1st edition ruleset in 1986 with the publication of the "Dungeoneer's Survival Guide" hardbound.

The term THAC0 (as opposed to a usable game mechanic) is actually much much older, and can be found in the 1st edition DMG (published in 1979) on pages 196 - 215 in the "APPENDIX E: ALPHABETICAL MONSTER LISTING". But at that point, it was little more than just another stat. There was no real explanation on how to use it as an actual game mechanic.
 
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Lanefan

Victoria Rules
To be fair, nobody has carefully explained to me that subtraction is really hard yet.
Is isn't.

But I still never used THAC0, for two reasons - one philosophical and one practical.

Philosophical reason: both as player and DM I want the combat matrix (or later, BAB) to be DM-side info rather than player-side.

Practical reason: for me as DM it puts in an extra unnecessary step in figuring out whether an attack hits or not; that step in fact being that I have to start the calculation an entirely different way. The way I do it now the player gives me their roll after adjustments, I add the target's AC* and any other unknown-to-players factors* and if the result is 21+ it's a hit. If instead a player were to just tell me "I hit AC 4" I'd have to reverse-engineer how that number was arrived at (knowing that the player in theory doesn't know the combat matrix) and then do the same steps I already do.

* - can be + or - numbers, or 0.
 

digitalelf

Explorer
If instead a player were to just tell me "I hit AC 4" I'd have to reverse-engineer how that number was arrived at (knowing that the player in theory doesn't know the combat matrix) and then do the same steps I already do.
Like you (I assume), I too do not like to just provide the AC of the PC's foes to my players.

However, that said, neither the Combat Matrices nor THAC0 keep the player from determining the AC of any opponent they face.

The way you do it, the player can easily determine the AC of their opponent by the process of elimination... "Well, a 14 did not hit, but a 15 does, so that orc's AC must be at least 3".

Which is exactly what the players do with the DM using THAC0... "Okay, I rolled a 14, which hit AC 4, but that missed... I now just rolled a 15, which hit. So that orc's AC must be 3".

Don't get me wrong. I don't care how you resolve combat in your games... My point is that you are not keeping any secrets from the players by using the Combat Matrices.

Players that wish to metagame in this fashion, will do so.
 
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Harzel

Explorer
THAC0 was first introduced to AD&D (1st Edition) as a usable game mechanic in 1983 with the module "UK3: The Sentinel" as an optional rule.

It latter appeared as an "official" part of the 1st edition ruleset in 1986 with the publication of the "Dungeoneer's Survival Guide" hardbound.

The term THAC0 (as opposed to a usable game mechanic) is actually much much older, and can be found in the 1st edition DMG (published in 1979) on pages 196 - 215 in the "APPENDIX E: ALPHABETICAL MONSTER LISTING". But at that point, it was little more than just another stat. There was no real explanation on how to use it as an actual game mechanic.
Ah, ok, thanks. That explains my monster descriptions. I guess I figured out how to use it myself. And when we can give XP again, I'll give you some.
 

Oofta

Title? I don't need no stinkin' title.
So am I understanding this right? That one of the "advantages" of THAC0 was that you had a character sheet where you pre-calculated what AC you hit based on your D20 roll? Which you could do with any system that uses a reasonably small range of numbers to determine whether you hit or not?

As far as subtracting being more difficult, it's the combination of adding, and subtracting that you need to do (assuming you need to adjust your pre-written numbers) and some people have a hard time subtracting into negatives. But it's probably like trying to explain color to my buddy who's color-blind. No matter how much I can try to explain the difference between red and green, he's just not going to get it. If you don't understand why adding all numbers is easier than adding and comparing positive numbers is more natural for most people you'll just have to accept that it is.
 

Morrus

Well, that was fun
Staff member
But it's probably like trying to explain color to my buddy who's color-blind. No matter how much I can try to explain the difference between red and green, he's just not going to get it. If you don't understand why adding all numbers is easier than adding and comparing positive numbers is more natural for most people you'll just have to accept that it is.
Wow?
 

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