The ROM utilizes a diode x-y memory array which can be comprised of a number of suitable materials which form rectifying junctions. The diodes are formed vertically in order to provide a very high density array. On pitch decoder circuitry which is capable of matching the high density of the memory cells in the x-y memory array is also described, as is a unique apparatus for joining adjacent ends of conductive lines which are spaced very close together without increasing their pitch.