This paper describes the logical design of an accumulator register for a general purpose digital computer. The only logic gates used are NOR gates and inverter gates and the sole storage device is a gated clocked flip-flop which takes the value on a single input line when the gate line is high. The accumulator register operates in conjunction with another register called the memory exchange register. The memory exchange register can be added to the accumulator, subtracted from the accumulator, ANDed with, and ORed with the accumulator; the result in each case being placed in the accumulator. The accumulator can also be shifted right or left. The problem of carry propagation during addition is alleviated by carry bridging. The accumulator circuitry has been made simpler by treating the operations to be performed collectively rather than individually, and by careful assignment of input-values to the storage devices.

An important step in the design of digital machines lies in the derivation of the Boolean expressions which describe the combinational logical networks in the system. Emphasis is generally placed upon deriving expressions which are minimal according to some criteria. A computer program has been prepared which automatically derives a set of minimal Boolean expressions describing a given logical network with multiple-output lines. The program accepts punched cards listing the in-out relations for the network, and then prints a list of expressions which are minimal according to a selected one of three criteria. This paper describes the basic design procedure and the criteria for minimality.