Turing Machine

There is a model of computers called a Turing Machine. The model is that every computer has three parts:

1. A very long strip of paper. So long that it goes on forever in both directions. The paper is split into squares, all the same size.
2. A person or robot who can see one of the squares on the paper and move the paper one square left or one square right at a time.
3. A rule book that the robot must follow.

Usually the rule book is represented with a directed graph