Definition

WireWorld is equivalent to a four-state automaton with Moore neighborhoods, wherein the four states have the following significance:

• 0 - background cell

• 1 - wire cell

• 2 - electron head

• 3 - electron tail

The rules of evolution are:

• - a wire cell becomes a head whenever one or two Moore neighbors (besides itself) are heads; otherwise it remains a wire cell.

• - a head always becomes a tail

• - a tail always reverts to a wire cell

• - the background never changes

In a way, the rules resemble a Zhabotinsky reaction; an electron head is the activated state, the tail the refractive state, the wire itself constituting the inactive medium. The background confines the activity to the wires. Of course there is no requirement that the wires must be lines; something other than digital logic would result though, if they were not.

Constituting the electron as a pair, head and tail, polarizes the combination, forcing it to move in the direction of the head. Other mixtures would be possible, but are generally avoided as irrelevant to the task of simulating digital logic; likewise two electrons are not supposed to travel in opposite directions on the same wire. Nevertheless, arranging junctions where electrons can meet; that is, forming logic elements, is one of the design problems to be solved in WireWorld .

Normally the CAM/PC does not allow a four state Moore neighborhood, but the affinity between WireWorld and the Zhabotinsky reaction and its implied counter lets the rule be implemented. Plane 1 holds the circuit diagram, plane 0 the electron's head, plane 3 the tail. To enter the head state is the only decision which requires any neighborhood beyond the cell itself; assigning it to a Moore-neighborhood plane 0 fits just nicely into the CAM/PC 's capabilities.