GB1257970A - - Google Patents

Abstract

1,257,970. Digital calculating machines. BELL PUNCH CO. Ltd. 17 Feb., 1970 [17 Feb., 1969], No. 8578/69. -Heading G4A. A digital electric calculating machine as described in Specification 1,242,121 is modified so that the decimal point of the quotient of a division operation is calculated and displayed. The dividend is in the accumulator register 38, the divisor in register 24; division is by repeated subtraction and the quotient is stored in register 38. The decimal point of the quotient is calculated by storing the decimal point of the dividend in counter 56 and adding to it the complement of the decimal point of the divisor from register 24 and the result is displayed on a visual display 14. The visual display.-This display 14 comprises 10 decade-number tubes 16 and ten corresponding decimal point neon bulbs 17 so that the highest significant digit is in the left-hand tube. A decade counter buffer 20 converts a train of pulses from registers 24, 38 or counter 56 into the BCD equivalent which passes, via staticizer 18, to the display. The decimal point is displayed on the appropriate bulb 17, the lefthand bulb being the zero decimal point. The timing is controlled by the timer circuit 12. The arithmetic apparatus.-Two four-stage shift registers 24, 38 controlled by clock pulses perform addition, subtraction, multiplication or division. The decimal counter 56, which is a four-bi-stable, ten state, ripple through counter, holds a digit corresponding to the decimal point -of the dividend stored in the register 38. Numbers are entered and functions chosen through a keyboard (not shown). Operation.-The divisor in register 24 is repeatedly subtracted from the dividend until the answer is negative when one addition is made, and the quotient is stored in register 38. Then the decimal point of the quotient is calculated as described using gates 360 and 580 (not shown). If 'the sum is greater than ten the counter 56 will count through ten and give the correct result. Then the quotient and decimal point are shifted through buffers 20 to their correct display positions.