Turing machines, CAs and the universe

摘要

This week we'll venture in the realm of theory for a change, starting with Tur- ing machines. In case some of you don't know what a Turing machine is, here is the Wikipedia definition: "A theoretical device that manipulates symbols contained on a strip of tape." It is not arnpractical computing device, but rather "a thoughtrnexperiment representing a computing machine."