Turing Machine

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What Does Turing Machine Mean?

A Turing machine is a theoretical machine that manipulates symbols on a tape strip, based on a table of rules. Even though the Turing machine is simple, it can be tailored to replicate the logic associated with any computer algorithm. It is also particularly useful for describing the CPU functions within a computer.


Alan Turing invented the Turing machine in 1936, and he referred to it as an "a-machine" or automatic machine.

Techopedia Explains Turing Machine

The Turing machine is not intended to be a functional computing technology; instead, it is intended as a hypothetical machine that represents a computing machine. The Turing machine can help computer scientists comprehend the boundaries of mechanical computation.

Turing machines mathematically model a device that mechanically runs using a tape. This tape includes symbols, which the machine can write and read, one after the other, with the help of a tape head.

More specifically, a Turing machine includes the following:

  • Tape: A tape that is split into cells, one beside the other. Every cell includes a symbol from a certain finite alphabet. The alphabet includes a unique blank symbol as well as one or more other symbols. The volume of tape required for the computation is always included in the Turing machine.
  • Head: A head that is able to write and read symbols on the tape. In certain models, the head moves while the tape is fixed.
  • State register: A state register to store the Turing machine's state. There is a special start state through which the state register is initialized.
  • Finite table: A finite table (sometimes referred to as a transition function or an action table) of instructions, which are generally quintuples, but occasionally quadruples.

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.