Patent GB-1003424-A (GB)
Title: Data processing apparatus
IPC: G06F7/72
Filed: 1962-07-03
Abstract: 1,003,424. Digital electric calculators. RADIO CORPORATION OF AMERICA. July 3 1962 [July 19, 1961], No. 25532/62. Heading G4A. In apparatus in which positive and negative numbers in a range of numbers are represented by their residues to a plurality of relatively prime moduli, means are provided for determining the sign of a residue coded number by forming a corresponding related coded number having only two non-zero residues, which are converted to a signal representative of the sign of the original coded numbers. In the arrangement described, decimal numbers from -105 to +104 inclusive are represented by their residues to the three moduli 5, 6, 7. For example, in this representation, the representation of a negative number being such that the sum of its residue representation and the residue representation of the corresponding positive number is zero. Arithmetic operations.-The circuit described is for calculating the sum, difference or product of two numbers P=(X 1 , Y 1 , Z 1 ) and Q=(X 2 , Y 2 , Z 2 ), the residues X i , Y i  being supplied on a bus 10 over appropriate 3-wire leads R a , R b , R c  which carry the corresponding residue in pure binary coded form as at 3-bit word. The operands P, Q are supplied in turn on the bus 10 and registered via gates 11-16 in registers An A 2  respectively, each of these registers comprising separate registers 17-22 for the respective residues. The binary-coded contents of the registers 17-20 are recoded into 1-outof-5, 1-out-of-6, and 1-out-of-7 coded form by encoders 23-28, corresponding residues being supplied to appropriate circuits 29, 30, 31 which produce the required answer on leads 32, 33, 34 each comprising three wires for the binary coded residues of the answer which is registered in a register A 3 . The circuits 29, 30, 31 comprise magnetic core matrices having sense wires such as 75, 76, 78, Fig. 4, threaded in such a way as to produce the correct answer digits for the various arithmetic operations. Sign determination.-To ascertain the sign of a number supplied on the bus 10, additional equipment not shown in Fig. 1, but shown in Figs. 2 and 4, is provided. This equipment includes a sign translator 71 included in the circuit 30 (shown as 30<SP>1</SP> in Figs. 2 and 4) and gates 41, 42 for supplying the number on the R c  leads to the registers 20, 21 and the number on the R a  leads to the register 21. To determine the sign of a residue coded number, the third residue is subtracted from all three residues to produce a number of the form (x, y, 0). The sign of this number and hence of the original number is determined by the two residues x, y and can be read from a table. For example, for the residue coded number (1, 3, 4)= +81; 4 is subtracted from each residue to produce the number (2, 5, 0) and it is found from a table that this number has a positive sign, which is therefore the sign of the original number. In operation, the gates 14, 15, 41 are opened to direct the first residue R a  to the X 1  register 17, the second residue R b  to the Y 1  register 18 and the third residue R c  to the X 2  and Y 2  registers 20, 21. The circuits 29, 30<SP>1</SP> then produce the answers (in residue form) to the subtractions R a -R c , R b -R c ,to form a number related to the original number but with the third residue equal to zero. The first two residues of the related number are fed via buses 38<SP>1</SP>, 39<SP>1</SP>, Fig. 2, and gates 42, 15 are opened to feed these residues to the Y 2  register 21 and Y 1  register 18 respectively, the encoded equivalents of the residues being supplied to the circuit 30<SP>1</SP>, a " sign translater " 71 in the form of a table look-up matrix magnetic core array is effective to produce on a lead 85 a signal indicative of the sign of the related number (which is the same as the sign of the original number). The " related numbers " in the range of coded numbers are those in which the third residue is zero; and all the numbers to which each related number is related have the same sign characterized by the other two residues.