Electron Cellular Automata

A CellularAutomaton, also known as WireWorld. It was described by AlexanderKeewatinDewdney in a ScientificAmerican "Computer Recreations" column.

It allows one to simulate digital logic, using solitary "bits" travelling down "wires" and through "gates".

Needless to say, it supports TuringComplete computation.

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Cells are arranged in a square grid, each with 8 neighbors. Each cell has 4 states:

• Background. Always transitions to Background.
• Head. Always transitions to Tail.
• Tail. Always transitions to Wire.
• Wire. transitions to Wire, unless it has 1 or 2 neighbors in state Head, in which case it transitions to Head.

For example, imagine a field with all cells set to Background except for a line of Wire cells, with a Head and Tail at one end. (This pair is called an "electron".) Thus:

 tH.........................

The next states will be:

 .tH........................
 ..tH.......................
 ...tH......................

If the wire forms a loop, the electron will go round and round. If a wire strand leads off the loop, the electron will split and send pulses down the wire. If 2 pulses arrive at the same time in the same place, they can be arranged to cancel. You can make diodes, latches, AND and OR gates.

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A diode, if memory serves, is:

       ..
 ..tH.. ....
       ..

-- AlastairBridgewater

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See it at http://neekatave.com/ca/examples/wirewrld/index.shtml.

There's a brief article at http://mathworld.wolfram.com/WireWorld.html with some examples of logic gates and an 8x8 -> 16 multiplier.

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Cf: CellularAutomaton