A mathematical model of a device that (a) changes its internal state (b) reads from, writes on, and moves a potentially infinite tape, (c) that can be programmed, and (d) satisfies the minimal requirements for a computer, all in accordance with its present state, thereby constituting a model for computer-like behavior. See  universal Turing machine. See also  computer,  computer program,  computer programming,  model,  programmed computer,  programmer,  programming,  read,  requirement,  state,  write.