Tturingmachine

This App represents a turing machine. If you don't know what a turing machine is, here is a part of the explanation of it from wikipedia:

"A Turing machine is a hypothetical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a computer.

The "Turing" machine was invented in 1936 by Alan Turing[1] who called it an "a-machine" (automatic machine). The Turing machine is not intended as practical computing technology, but rather as a hypothetical device representing a computing machine. Turing machines help computer scientists understand the limits of mechanical computation."

source: http://en.wikipedia.org/wiki/Turing_machine

The Tturingmachine-app offers you a nice, graphical overview of the tape and lets you watch how the head switches position. Also, you have a clear overlook on the start configuration as well as on the current configuration and all the other, important information.
Navigating through the process is done by either going a single step and watching the tape/word how it changes, or by executing until the end is reached (for prophylaxis on endless loops maximum 500 steps).

For a more detailed tutorial on how to configure and work with the machine, see the menue in the app and click About/Help.