Digital computer for adding and subtracting
US5751623A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 22, 1995 |
| Grant date | May 12, 1998 |
| Priority date | — |
| Expiry date | Nov 22, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F7/4912
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for efficiently adding and subtracting multiple digit decimal numbers represented as a series of 8-bit bytes, each 8-bit byte representing one digit of a decimal number. In accordance with the present invention, numeric values are stored internally within a computer in a new format, referred to as "X7B". Numeric input into the computer can be in any form, such as binary, ASCII, EBCDIC, X7B, etc. X7B values are computed by adding the 8-bit binary representation of each decimal digit to a binary value of"0111 1011" (i.e., "7B" hexadecimal). The invention adds or subtracts two X7B numbers by performing the following operations: (1) inputting first and second decimal numbers in X7B format as a concatenation of 8-bit values; (2) adding or subtracting the two X7B values; (3) logically AND'ing each byte of the sum or difference with the hexadecimal value "30"; (4) logically shifting the result of the logical AND operation 3 bits to the right; (5) subtracting the result of the shift operation from the sum or difference resulting from the first addition or subtraction operation; (6) logically AND'ing each byte of the preceding result with the hexadecimal value "0F"; a…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.