Patent GB-1238920-A (GB)
IPC: G06F3/023
Filed: 1968-09-12
Abstract: 1,238,920. Electronic computer. TEXAS INSTRUMENTS Inc. 12 Sept., 1968 [29 Sept., 1967 (3)], No. 43348/68. Headings G4A and G4H. [Also in Division H3] Electronic calculator has electronic means comprising an integrated semi-conductor array substantially located in a single plane which is responsive to input signals to perform arithmetical operations, the array also including memory means for storing representations of numbers entered into the calculator and has means responsive to control signals supplied to the calculator to display the answers of the arithmetical operations. A desk top computer powered by batteries has a manually operated keyboard arranged to enter digits 1-9, a decimal point and instructions add, subtract, multiply, divide, clear (C), error (E) and print (P). The keyboard is mounted above a printed circuit plate 6 (Fig. 5) and depression of a key causes a conductive plate to short selected conductors, the layout of the keys corresponding to the numbers, letters and symbols on Fig. 6, e.g. if a key representing Number 2 is pressed leads K2, KBN, COM, K4 are shorted together where COM is connected to earth. The plate shown codes digits in the excess three code and earthed lines represent zeros and non-earthed lines represent ones. It can be seen that an instruction command shorts together the instruction line and the COM and KOP lines. Beneath the plate 6 is an integrated semi-conductor circuit plate 7 carrying the registers, gates and clocks required for performing the arithmetical operations. Arithmetical operations (Fig. 28).-Data from the keyboard 6 enters the L Register 307 which acts as a four-bit buffer register and a 16-position counter to control the number of additions and subtractions in multiply and divide operations under control signals RR, RA, RO, RS. A digit stored in the L Register is supplied to the print matrix and impressed on the tape under the control of three one-shot multivibrators. The digit is then supplied through gate G2 to the operand register. Under control of clock pulses the 6-digit operand register is shifted 5 places, the new digit is passed through G2 and the digits shifted 5 places again to leave the new digit in the right hand column of the shift register. The add key transfers a number in the operand register to the accumulator register and causes the number in the operand register to be added to the number in the accumulator register via the serial adder. During a subtract cycle the 9's complement of the number in the operand register is supplied to the adder, the carry flipflop being set to one during this cycle. During multiplication the most significant digit from the accumulator register is placed in the L- register and the remaining digits of the number are stored in the left-most five columns of the accumulator register. The number in the oper- and register is placed in the six right-most columns of the accumulator register and is added to the contents of the operand register a number of times equal to the number in the L register, the latter being decremented by one each addition. When the number in the L-register is zero the next most significant digit is entered therein and the contents of the accumulator register are shifted and the additions continued. For division the dividend is placed in the accumulator register and the divisor in the operand register. The L-register is set to contain the digit 11 and the divisor is subtracted from the dividend, the result being stored in the accumulator register in the 6 right-most columns. The number 11 is reduced by one and the process continued until the result becomes negative. The divisor is added to the result and the L- register is reduced by one. The number in the L-register represents the 9's complement in the excess 3 code of the quotient, is complemented and stored in the accumulator register. The remainder in the accumulator register is shifted and the subtraction process is repeated until a 6-digit quotient and a 6-digit remainder are obtained. For addition and subtraction the decimal points should be aligned. For division no decimal point is indicated and for multiplication the point is printed in the correct position. A counter for each register indicates the decimal point position.