What was the name of Stephen Wolfram's book that referenced Wolfram's 2-state 3-symbol Turning machine?
Wolfram's 2-state 3-symbol Turing machine In his book "A New Kind of Science", Stephen Wolfram described a universal 2-state 5-color Turing machine, and conjectured that a particular 2-state 3-symbol Turing machine (hereinafter (2,3) Turing machine) might be universal as well.
Reversible computing Reversible computing is a model of computing where the computational process to some extent is reversible, "i.e.", time-invertible. In a model of computation that uses deterministic transitions from one state of the abstract machine to another, a necessary condition for reversibility is that the relation of the mapping from states to their successors must be one-to-one. Reversible computing is generally considered an unconventional form of computing.