the Turing machine to a more friendly, computer-like abstract model called the counter machine; Elgot and Robinson (1964), Hartmanis (1971), Cook and Reckhow (1973) carried this work even further with the register machine and random-access machine models—but basically all are just multi-tape Turing machines with an arithmetic-like instruction set. 1970–present: as a model of computation Today, the counter, register and random-access machines and their sire the Turing machine continue to be the models of choice for theorists investigating questions in the theory of computation. In particular, computational complexity theory makes use of the Turing machine: See also Arithmetical hierarchy Bekenstein bound, showing the impossibility of infinite-tape Turing machines of finite size and bounded energy BlooP and FlooP Chaitin's constant or Omega (computer science) for information relating to the halting problem Chinese room Conway's Game of Life, a Turing-complete cellular automaton Digital infinity The Emperor's New Mind Enumerator (in theoretical computer science) Genetix Gödel, Escher, Bach: An Eternal Golden Braid, a famous book that discusses, among other topics, the Church–Turing thesis Halting problem, for more references Harvard architecture Imperative programming Langton's ant and Turmites, simple two-dimensional analogues of the Turing machine List of things named after Alan Turing Modified Harvard architecture Quantum Turing machine Claude Shannon, another leading thinker in information theory Turing machine examples Turing switch Turing tarpit, any computing system or language that, despite being Turing complete, is generally considered useless for practical computing Unorganized machine, for Turing's very early ideas on neural networks Von Neumann architecture Notes References Primary literature, reprints, and compilations B. Jack Copeland ed. (2004), The Essential Turing: Seminal Writings in Computing, Logic, Philosophy, Artificial Intelligence, and Artificial Life plus The Secrets of Enigma, Clarendon Press (Oxford University Press), Oxford UK, . Contains the Turing papers plus a draft letter to Emil Post re his criticism of "Turing's convention", and Donald W. Davies' Corrections to Turing's Universal Computing Machine Martin Davis (ed.) (1965), The Undecidable, Raven Press, Hewlett, NY. Emil Post (1936), "Finite Combinatory Processes—Formulation 1", Journal of Symbolic Logic, 1, 103–105, 1936. Reprinted in The Undecidable, pp. 289ff. Emil Post (1947), "Recursive Unsolvability of a Problem of Thue", Journal of Symbolic Logic, vol. 12, pp. 1–11. Reprinted in The Undecidable, pp. 293ff. In the Appendix of this paper Post comments on and gives corrections to Turing's paper of 1936–1937. In particular see the footnotes 11 with corrections to the universal computing machine coding and