In games like the tabletop role-playing game Dungeons & Dragons, Armor Class (abbreviated AC) is a number assigned to every character or creature, which indicates how difficult it is to hit that creature with an attack. Tabletop role-playing games are a particular form of role-playing game. ... Players Handbook for D&D Dungeons & Dragons (abbreviated as D&D, DnD, or AD&D for the advanced edition) is a fantasy tabletop role-playing game (RPG) published by Wizards of the Coast. ...

In early versions of D&D, a lower armor class indicated that a creature was more difficult to hit (see THAC0). An unarmored human had an armor class of 10, and armor lowered a character's armor class. A very powerful creature usually had an armor class lower than 0. THAC0 (often pronounced THA-ko) is an acronym constructed from the phrase To Hit Armor Class 0 which comes from the tabletop role-playing game Dungeons & Dragons. ...

In third edition D&D, the armor class system has been effectively reversed. An unarmored human still has an armor class of 10, but wearing additional armor now increases armor class. Thus, a creature with an armor class of 0 in second edition would have an equivalent armor class of 20 in third edition. Also, a wider range of factors can now affect armor class, giving the system a precise method for assigning armor classes and armor modifications, whereas in earlier editions this was somewhat ad hoc.

Numerous Dungeons & Dragons-derived roleplaying- and computer games use Armor Class system or a variation thereof. Many games with unrelated systems (such as Fallout) use the term to represent a character's ability to avoid damage. In role-playing, participants adopt characters, or parts, that have personalities, motivations, and backgrounds different from their own. ... This article needs a complete rewrite for the reasons listed on the talk page. ... Fallout is a computer role-playing game produced by Tim Cain and published by Interplay in 1997. ...