GB762693A - Data processing device - Google Patents

Abstract

762,693. Digital electric calculating-apparatus. SOC. D'ELECTRONIQUE ET D'AUTOMATISME. March 18, 1954 [March 19, 1953], No. 7959/54. Class 106 (1). In a device for forming the twos complement (ones complement plus unity) of a signed series mode binary number, the sign digit coming first in time and the most significant digit last, the number passes through a device 1, Fig. 1, which leaves the sign digit unaltered but inverts the following digits if the sign digit is negative or leaves them unchanged if it is positive, and enters an input 7 of a two input adder 6, having an internal carry loop formed by a unit-delay 10 and a gate 11, where it has unity added to it if its sign is negative or zero if its sign is positive, the " one " which is added if the number is negative actually being the sign digit which is gated by the device 1 via a unit delay 5 to the second input 8 of the adder 6. The number leaves the adder via a terminal 13, passes through a minor cycle delay 14 and re-enters the adder to allow round carry into only the first digit position of the number, carry from the first to second position (i.e. from the sign digit position to the least significant denomination of the binary number) being prevented by a gate 11 which is closed every second digit period by a control pulse. The device has the property that the number - 0 is converted into + 0 by it. An accumulator, Fig. 2, differs sub. stantially from Fig. 1 only in that the adder 6 is replaced by a three input adder. The main storage circulation path for the accumulator is via a delay 14 and one input 23 of the adder. As shown the accumulator of Fig. 2 contains a device 24 in its output lead which could be a further twos complementor. Suitable diode gating circuits and pulse-shaping circuits are described.