CODE - in communications, an unvarying rule for replacing a piece of information such as a letter, word, or phrase with an arbitrarily selected equivalent. The term has been frequently misapplied and used as a synonym for cipher. In the past this blurring of the distinction between code and cipher was rather inconsequential; in fact, many historical ciphers would be more properly classified as codes according to present-day criteria.
GAME THEORY - game theory, branch of applied mathematics that provides tools for analyzing situations in which parties, called players, make decisions that are interdependent. This interdependence causes each player to consider the other player’s possible decisions, or strategies, in formulating his own strategy. A solution to a game describes the optimal decisions of the players, who may have similar, opposed, or mixed interests, and the outcomes that may result from these decisions.