30th November 1936
Alan Turing invents the principle of the modern computer

In 1936, while a fellow of King's College, Cambridge University, Alan Turing invents the principle of the modern computer.

Turing described an abstract machine with the following components:

• An infinite tape divided into cells, extending in both directions, that serves as the machine's memory.
• A tape head that moves along the tape, and can read and write symbols to cells on the tape.
• A set of instructions that determine the operation of the tape head.

Despite the apparent simplicity of this machine, Turing proved that it is sufficient to calculate any algorithm, no matter how complex.

Turing described his machine in a paper titled "On Computable Numbers with an Application to the Entscheidungs-problem". Turing finished and delivered his paper on 28 May 1936. The paper was read on 12 November 1936, and then published in the Proceedings of the London Mathematical Society journal in two parts: the first on 30 November 1936, and the second on 23 December 1936.

The machine described in Turing's paper is now commonly known as the universal Turing machine. The concepts it describes are fundamental to all computers.

Related information:

• Centre for Computing History: Alan Turing
• University of Cambridge: What is a Turing Machine
• Alan Turing: On Computable Numbers with an Application to the Entscheidungs-problem

Image:

• Alan Turing
  Credit: © National Portrait Gallery, London. Elliott & Fry quarter-plate glass negative, 29 March 1951 NPG x82217.

Related Items in the Collection:

Alan Turing proposes the Automatic Computing Engine, or ACE