An arrow points from a box labeled Input device/devices at left to a large box at center containing a processor (CPU) and main memory, represented by a column of smaller, adjacent boxes. A jagged break at the bottom of the column indicates that it continues below. Arrows point in both directions between the processor and the main memory. An arrow points from the center box to a box at right labeled Output device/devices. Arrows point in both directions between the center box and a box below labeled Secondary memory.