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Two's Complement Multiplication

IP.com Disclosure Number: IPCOM000069583D
Original Publication Date: 1978-May-01
Included in the Prior Art Database: 2005-Feb-21

Publishing Venue

IBM

Related People

Authors:
Capps, AB Quinn, RL [+details]

Abstract

Fig. 1 shows a multiplication algorithm 1 of two K-bit binary numbers A and B, both in two's-complement form. Rather than first converting the operands to positive form, algorithm 1 multiplies them directly at 11. Two corrections 12 and 13 are then applied to the 2K-bit product. If one operand A is negative (block 121), then the other operand B is subtracted from the high-order K bits of the product (block 122). If B is negative (block 131), then A is subtracted from the high-order K bits of the product (block 132). Corrections 12 and 13 are mutually independent; they may be performed in any order. The subtraction operations signify the binary addition of the two's complement, as in conventional practice.