Good–de Bruijn diagram

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Good–de Bruijn diagram (Good–de Bruijn graph) A directed graph illustrating the possible succession of states of a shift register. Each possible state of the shift register (indicated by its contents) is represented by a node in the graph; from each node a set of arcs lead to all its possible immediate successors. (Succession involves one clocking of the shift register, with some serial input.) If there are n cells in a q-ary shift register, there will be qn nodes, each with q arcs leading from it, and thus qn+1 arcs altogether.

When the serial input is some function of the current state, the behavior of the shift register is described by a Good–de Bruijn graph with some arcs deleted: such subgraphs are used in the study of feedback registers.