A permanent storage memory system comprises first and second memory units each having data stored thereon in different predetermined patterns. The outputs of each memory unit are connected to a common memory output. Timing signals are applied to each memory unit in reverse order and the selected data is transferred to the common memory output from one unit and then the other during the first and second of these signals, respectively. For each memory unit, data is blocked from the output during the period of the timing signal in which the data is not being transferred, thereby to enable ready combination of the data signals from each unit at the memory output. Data from each unit may be scanned in a predetermined sequence, that sequence being initiated from a location in that unit determined by an address signal applied to the unit. The selection of that initial memory location is performed by means of a shift register in combination with a logic unit. The latter receives an address signal and presets the shift register in accordance therewith.

An automatic sequencing circuit is disclosed which recognizes a particular coded input signal, initiates a process or data operation, and provides a coded output indicative of the operation performed. The circuit is particularly suited to hardware implementation of the control graph of a directed-graph design for any equipment using digital logic circuits.