Any device capable of carrying out a sequence of operations in a defined manner. The definition of the operations is called the program. An analog computer performs computations by manipulating continuous physical variables, such as voltage and time. A digital computer operates on discrete quantities, most often represented as ‘on-off’, indicating whether the value of a binary variable is 0 or 1. Numbers and information are then represented by the binary system. Philosophically the excitement generated by computers has been in exploring the extent to which mental operations are well-represented as computations. See also artificial intelligence, Chinese room, connectionism, Turing machine, von Neumann machine.