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# Multidigit Decimal Addition and Subtraction

IP.com Disclosure Number: IPCOM000088127D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

IBM

## Related People

Hicks, DR: AUTHOR [+3]

## Abstract

Example 1 Example 2 (10) B = ADD B, `6666' (20) W3 = ADD W2, CARRY (11) C = XOR A, B (21) W1 = ADD W1, `66' (12) A = ADD A, B, (22) W2 = XOR W1, W2 (13) C = XOR A, C, (23) W3 = ADD W1, W3 (14) C = SRA C (24) W2 = XOR W2, W3 (15) C = NOR C, `7777' (25) SKIP ON DIGITCARRY (16) C = SRL C (26) W3 = SUB W3, `06' (17) A = SUB A, C (27) SKIP ON CARRY (18) C = SRL C (28) W3 = SUB W3, `60'. (19) A = SUB A,C. Example 1 shows an algorithm for the addition of two 16-bit binary-coded decimal (BCD) numbers in a 16-bit binary arithmetic unit. Registers A and B hold the arguments, the result being returned to A; C is a scratch register. The operations ADD, SUB, XOR and NOR represent full-width binary addition, subtraction, exclusive-OR and OR-complement, respectively.

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