 It was devised to investigate the relation between computation and reversible processes in physics.This model can be used to simulate Boolean circuits in which the wires of the circuit correspond to paths on which one of the balls may travel, the signal on a wire is encoded by the presence or absence of a ball on that path, and the gates of the circuit are simulated by collisions of balls at points where their paths cross.In particular, it is possible to set up the paths of the balls and the buffers around them to form a reversible Toffoli gate, from which any other Boolean logic gate may be simulated.