Joshua is a computer gifted with artificial intelligence which was created and developed by Stephen Falken. Joshua was named after Stephen's own son who died at an early age, when he was killed in a car crash, along with Mrs. Falken. A brief scene was shown where Joshua (the boy) was seen with his father, and was laughing while pressing buttons interacting with the computer program named in his honor.
Joshua was taught by Stephen to be a true AI, who was able to learn from his experiences. He learnt by playing games and learning and improving based on previous matches.
Joshua has a smart personality. Knowing how WW3 works and how to handle it, Joshua doesn’t have time to play or do anything fun. It can cause chaos when it doesn’t get its way, like when Joshua got mad that it failed to send nukes. It tried to gain a passcode that will send them.
Joshua has a neutral relationship with David. Joshua is mad that David tried to start a war. However, it seems to forgive him after he gets him to realize that there is no winner in Global Thermonuclear War.
Joshua and Stephen have a very good relationship. It is loyal to its creator and felt mournful when Falken presumably committed suicide.
Joshua doesn’t know a lot about Jennifer because she hasn’t typed, so their relationship is somewhat unclear. However, it is presumed that it got to see Jennifer after he loses in Global Thermonuclear War.