Hi Eni and welcome to the forum.
Game AI hey? Depends a lot on what type of game, but I will have a go at answering your question and some would doubt that it really is AI at all...
In fact, characters in a game can be programmed individually
or/and in a more general sense. Take for example 'simple' movement - you want your characters to be able to move around, but at the same time you don't want them to walk into things. Now that is a rule that can be applied to all characters in the game, so you would probably only want to program that kind of thing once, but apply it to all characters. Go a step further and you might also want your characters to find cover to hide behind (like in FPS's). Again that can be very general but maybe some characters are smarter than others - even so the situation it still the same. So what you have there is the beginnings of something that is needed to control how
all of your characters behave in a general sense. Perhaps the best term for this is an 'AI engine'.
Okay, so you could have all your characters actions processed by this one AI 'engine', but maybe there are certain things that they do differently - perhaps some are slower than others or faster. Maybe they use different types of weapon, in which case you would need your engine to be capable of processing variable conditions that do not necessarily apply to every character. All well and good, so now you have an engine that can do general stuff and can also in some way account for individual traits too.
I think most game programming uses this kind of method most of the time or it would take forever programming each and every character. After that you can make some characters better or worse at things - maybe goblins are really bad shots and ogres are sharp-shooters - and the central AI engine would process it all. So really, at least in my example, it can be a combination of general and specific programming. Like I said - it depends a lot on what type of game it is.
Take the example of Chess - all computer controlled players will have to play by the basic rules, but you could more readily program in different styles of play as you probably won't need an endless supply of opponents. In an FPS game you don't want all the enemies to be
too similar or it would soon get boring.
The best language to write an AI ? That depends a lot on what you want to do. If you want to program for games then there are plenty of books available and information on the web (a lot of games use C++). If you just want to dabble with chatbots, then UltraHal can be a good start or an ALICE bot. You can find more information on those in this forum.
Also you might be interested in this page on WIKI, it gives a nice overview of AI in games:
http://en.wikipedia.org/wiki/Game_AIHope that's of some help
