A tag system is set of rules that specifies a fixed number of elements (commonly denoted ν or β) be removed from the beginning of a sequence and a set of elements to be appended ("tagged" onto the end) based on the elements that were removed from the beginning. For example, consider the ν = 1 tag system shown in the illustration above, in which black represents 1 and white represents 0. Then the starting pattern is "1" and the transition rules are (1, ...)->(..., 1, 0) and (0, ...)->(..., 0, 1).

cellular automaton | cyclic tag system | lag system | mobile automaton | substitution system | Turing machine