F (ExTSR) is Frank, as in Frank Mentzer, longtime cohort of Gary Gygax, writer of the Red Box (1983) of D&D Basic and one of the few active folks from the advent of TSR and the role-playing age on Dragonsfoot (which is now no longer the case).
There are people who think of THAC0 solely as a 2nd Edition AD&D creation when in fact according to Frank it predates 1st Edition and may even have been in common parlance around the time of the Lake Geneva Campaign. And again for those that don't know the Lake Geneva Campaign was THE grand-daddy of them all in terms of RPGs campaigns; it was the one that Gary DM'ed and well, pretty much wrote AD&D as we know it.
Now on to THAC0 itself: THAC0 stands for "To Hit Armor Class (Zero)."
In 2nd edition AD&D in melee combat, one rolls a d20 and compares it against their THAC0 score. For example if your THAC0 score is a 18 and you roll a 14 you would hit Armor Class 4. In other words, straight up on the die with no modifiers THAC0 represents the roll you need to hit AC 0 on a d20. In a nutshell that's all there is to it. So why is it that people look like this when you bring up the subject of THAC0 in gaming circles?
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| "Is it THACO or THAC0? I don't see the difference... |
Seriously, simple math is that hard folks? The only argument that I can see possibly being made is for a unified mechanical rule of later editions which THAC0 is not. But, then again 1st and 2nd Edition has lots of wonky bits to it anyways. 3rd edition and later did tidy up stuff, but abandoned this one when it wasn't broken. Plus I'm not a fan of a single mechanic simply for its own sake, but can see the utility in some systems.
Maybe its the seemingly "weird" subtractions say for speed factor where lower is better. Sure AD&D (both 1st and 2nd) are not consistent whether high or low rolls are good or bad.
But the next time somebody starts squawking about the "difficulty" of simple math and unified mechanics being superior just point out they can, you know...do math. For the older grognard crowd point out that THAC0 appears in their "Ye Olde Holy Book" aka the 1st edition Dungeon Master's Guide written by Gary Gygax. For those who want to save vs disbelieve its right there on pages 196-214.
Be prepared to save vs. long winded diatribe regarding about how Gary didn't really like it. Dudes... shut the Hell up, it's in the freaking book, your book no less.
And if you are having issues? Here is a great breakdown of how THAC0 works.
