A class of automata similar to cellular automata but which have a single "active" cell instead of updating all cells in parallel. In a mobile automaton, the evolution rules apply only to the active cell, and also specify how the active cell moves from one generation to the next. All cells that are not active remain the same from one generation to the next. Mobile automata can therefore be considered a hybrid between elementary cellular automata and Turing machines. An example is shown above (Wolfram 2002, p. 71).
Two-dimensional mobile automata are also possible, but the number of possible rules is much larger than can be systematically categorized (Wolfram 2002, p. 931).