Patent GB-799584-A (GB)
Title: Improvements in or relating to electronic computing apparatus
Inventor: YANDELL RONALD PERCY BAWDEN
IPC: G06F7/50
Filed: 1955-10-25
Abstract: 799,584. Digital electric calculating-apparatus. POWERS-SAMAS ACCOUNTING MACHINES, Ltd. Sept. 21, 1956 [Oct. 25, 1955], No. 30550/55. Class 106 (1). In electronic computing apparatus, two binary coded digits are read simultaneously from a store to an adder whose parallel binary sum-representing outputs are applied to gates in a correction coding circuit, and notation control means under control of a scale-of-notation determining indication read from the store applies a radix determining pulse to the gates thereby to produce binary coded outputs from the gates representative of a digit having the same radix as that of the digits read from the store and as necessary representative of a carry output. General. In the computer described, numbers to be added (or subtracted by complementary addition) are read concurrently by heads RH, Fig. 2, from a magnetic drum D and passed to highways H1, H2, the result being passed via highway H3 to write heads WH. The digits are recorded in parallel on four track sections corresponding to the elements of the 1, 2, 4, 8 code, and each number location is divided into 20 digit positions DT1-DT20, Fig. 3. The amounts are recorded within positions DT3- DT18; position DT2 is used to indicate whether complementing (not described in detail) is to take place and whether an amount is decimal or sterling (pulse or no pulse respectively in the " 8 " section), and position DT19 to indicate the sign of an amount and whether the storage capacity has been exceeded. The highways H1 and H2 each comprise four code lines H11, H12, H14, H18 and H21, H22, H24, H28, Fig. 4, by which the separate binary portions of the coded amounts are passed via diode gates HCG1 and HCG2 and.pulse shapers PS1 to binary adders BA1, BA2, BA4, BAS. Adder BA1 also receives the stored carry DC, if any, from the addition of the preceding coded digits, and the carries C from BA1, BA2, BA4, BA8 are passed respectively to BA2, BA4, BA8 and a pulse shaper and inverter PS4, whereby for each pair of concurrently applied coded digits the sum appears in the code 1, 2, 4, 8, 16 on lines S1, S2, S4, S8 and 16 and on complementary lines " Not S2 " to " Not 16." A correction coding unit CCU produces the correctly coded sum digit on output lines H31, H32, H34, H38 (H3, Fig. 2) and a new carry CC which is passed via a one-digit-delay circuit UD to BA1. Unit CCU is controlled by a notation control unit NCU which supplies a signal on line SOT, TOC or PC according to whether the sum digit is in scale of ten or corresponds to ten shillings or pence respectively. If a " decimal " signal appears on line H18 or H28 during DT2, unit NCU is set to provide a signal on SOT during all digit periods and a decimal-indication pulse is appended to the sum via line DIG1; for sterling amounts, signals appear on lines TOC and PC during DT11 and DT9 respectively and on SOT for the other digit periods. Binary adder. Each of the adders BA1, BA2, BA4, BA8, Fig. 4, comprises diode coincidence gates BAG, Fig. 7, which respond to different combinations of the digit inputs A, B and carry input C (positive for " 1 ") or complementary or " not inputs produced by pulse shapers PS1 and PS2. The sum-producing gate outputs are connected via cathode followers CF1 to common line SD0 and pulse shaper PS3, and the carry-producing outputs via CF3 to line CO. Other circuit details; modifications. The unit CCU, Fig. 4, comprises groups of diode coincidence gates (similar to BAG, Fig. 7) and output cathode followers. The unit UD comprises a pair of bi-stable flip-flop circuits controlled by staggered timing pulses, and the control unit comprises further diode coincidence gates and two flip-flop circuits for decimal/sterling and scale-of-ten (SOT) indication respectively. In a modification, the switching between decimal and sterling is programmed; in another alternative the decimal/sterling indication is given by a manually operable switch. Reference is made also to other digit codes, e.g. 1, 2, 4, 5, and to a parallel addition in which the carry output from CCU, Fig. 4, is applied to the adder unit of next higher denomination.