Abstract: An improved distributed input/output system is disclosed for controlling numerous high speed peripheral devices (both low speed, medium speed, and high speed) and the transfer of data signals, status signals, and control signals between those devices and a general purpose digital computer. The control system described includes a direct-memory-access multiplexer which can accommodate a plurality of low or medium-speed input/output services and also high-speed input/output devices under the control of separate programmable microcoded peripheral-unit controllers. The direct-memory-access multiplexer of this invention is fully compatible with controllers that can also be used with an indirect-memory access multiplexer. Each controller, being an element of a distributed system, is adapted to be located at an individual peripheral device and each is connected to the multiplexer by an identical ribbon cable.