PARALLEL ADDITION AND DIVISION OF TWO NUMBERS BY A FIXED DIVISOR

1,177,609. Dividers and addition; data storage. INTERNATIONAL BUSINESS MACHINES CORP. 17 July, 1968 [9 Aug., 1967], No. 34107/68. Addition to 1,177,608. Headings G4A and G4C. Apparatus for dividing the sum of multiorder numbers by a predetermined divisor, generates the sum, generates an intermediate remainder for each order, and combines each order of the sum with the intermediate remainder for the next higher order to produce an intermediate dividend which is divided by the predetermined divisor to produce the quotient, the intermediate remainder for the lowest order being the final remainder. A binary-coded octal index quantity M is added to or subtracted from a binary-coded octal memory address N and the result divided by 3 as in Figs. 10A-10C. Each octal digit of M is applied in true or 7s-complement form (according as addition or subtraction is required) by gates G (Fig. 10A) to a carry-lookahead adder CLA (not shown) and via a respective unit C to a mod 3 adder respective to the octal order. Each octal digit of N is applied to the CLA adder and via a respective unit C to the corresponding mod 3 adder. Each unit C passes its input mod 3. The mod 3 adders feed an arrangement of mod 3 adders and mod 3 subtractors (Fig. 10B) to produce a quantity R in each octal order. The quantities R are combined with respective carries C from the CLA adder and a feedback signal (see below) in respective units P s , P A to produce an intermediate remainder in each octal order. Each unit P A produces (R+C+ feedback) mod 3 and each unit P s produces (R + C - feedback) mod 3. The other intermediate remainders each constitute the high-order digit of a two-octal-digit octal number which is the input to a respective Q f -Q p box, the low-order digit being a respective sum octal digit from the CLA adder. A further Q f -Q p box 10 receives the highestorder sum digit and a high-order carry C, from the CLA adder. Each Q f -Q p box divides its input by 3 and passes the integral portion of the result out as a respective digit of the final quotient. The high-order carry from the CLA adder is not added-in in subtraction and optionally may be similarly discarded in addition. In either case the C input to Q f -Q p box 10 is set to 0 and in the latter case if the highorder-carry is in fact 1 the feedback line shown is energized to add 2 to each P s unit and subtract 2 from each P A unit (2 being 8 mod 3). The carry input into the P A unit 22 is a " hot one " equal to 1 only in the case