This paper presents the design of a parallel digital computer utilizing a 20-μsec core memory and a diode storage microprogram unit. The machine is intended as an on-line controller and is organized for ease of maintenance. A word length of 19 bits provides 31 orders referring to memory locations. Fourteen bits are used for addressing, 12 for base address, one for index control, and one for indirect addressing. A 32nd order permits the address bits to be decoded to generate special functions which require no address. The logic of the machine is resistor-transistor; the arithmetic unit is a bus structure which permits many variants of order structure. In order to make logical decisions, a ``general-purpose'' logic unit has been incorporated so that the microcoder has as much freedom in this area as in the arithmetic unit.