What is Turing Machine UN+1?

Turing Machine UN+1 is one of the example Turing Machines that Sir Roger Penrose described on pages 54 and 55 of his book The Emperor's New Mind (Oxford University Press, 1989).

It is also one of the sample Turing Machines that's built into both of the Excel files that you can download from the Home page of this website.

If you had already watched the Demo Video (at the top of this page), then you saw a demonstration of the UN+1 Turing Machine.

What the UN+1 Turing Machine does is read the number on the tape (in Unary Notation), add one to it, and display the answer on the tape (again in Unary Notation).