In addition to the ability to understand a written language (preferably the same one that the questioner is using) the computer would also need to know what the structure of the sentence should be to pass the Turing test; if it confuses the verbs and nouns it would not be very convincing. The computer must know how to type, or have some other way of getting the language to appear on the questioner's screen. The computer must also have a large memory and be able to determine what type of question is being asked so as to give the best possible response. For instance, if the questioner is asking about the weather, the computer should not start talking about politics. If the questioner is using slang or internet speech the computer should know what it means and be able to respond accordingly.
Basically, in order to pass the Turing test the computer needs to have a large memory with information on almost every possible subject, especially the major ones or ones that have been in the news recently (it can just say it doesn't know and ask for a different question on other subjects). It must also be able to understand and respond appropriately regardless of whether the questioner is using proper grammar or slang. Most other problems can be explained away, because humans often make mistakes so only glaring errors would lead the questioner to think something was off with its chat partner.
Signing off,
Alyssa Potok
