In 1948 Alan Turing described a Logical Computing Machine with the following definition:
"An infinite memory capacity obtained in the form of an infinite tape marked out into squares on each of which a symbol could be printed. At any moment there is one symbol in the machine; it is called the scanned symbol. The machine can alter the scanned symbol and its behavior is in part determined by that symbol, but the symbols on the tape elsewhere do not affect the behavior of the machine. However, the tape can be moved back and forth through the machine, this being one of the elementary operations of the machine. Any symbol on the tape may therefore eventually have an innings."This concept is known today as the Turing Machine. Enter the NXT Turing Machine:
The NXT Turing Machine was made as a computer science project at Aarhus University. The NXT robot travels along a track which is the memory. Bricks are shifted up or down to represent their logic states. The whole system is run using the PC in a Java based GUI. Commands such as read, write, and move are sent to the NXT using bluetooth.
The guys at Lego of Doom have an absolutely MASSIVE writeup of their project and I would very highly recomend that you check it out! You can find their project at: http://legoofdoom.blogspot.com/