Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In mathematical logic and theoretical computer science a register machine is a generic class of abstract machines used in a manner similar to a Turing machine. All the models are Turing equivalent. The register machine gets its name from its one or more "registers" - in place of a Turing machine''s tape and head the model uses multiple, uniquely-addressed registers, each of which holds a single positive integer.