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# Coding Scheme for Detecting Data Entry Errors

IP.com Disclosure Number: IPCOM000100397D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 68K

IBM

Chen, CL: AUTHOR

## Abstract

Disclosed is a scheme to encode a sequence of hexadecimal digits with 2 check digits so that the data entry error resulting from a permutation of adjacent digits in the encoded sequence can be detected. Specifically, the scheme detects errors from the following set of permutations. 1. A swap of two adjacent digits. 2. A permutation of 3 adjacent digits. 3. A permutation from digit positions (1, 2, 3, 4) to (3, 4, 1, 2), or a permutation from digit positions (1, 2, 3, 4) to (4, 3, 2, 1).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 71% of the total text.

Coding Scheme for Detecting Data Entry Errors

Disclosed is a scheme to encode a sequence of hexadecimal
digits with 2 check digits so that the data entry error resulting
from a permutation of adjacent digits in the encoded sequence can be
detected.  Specifically, the scheme detects errors from the following
set of permutations.
1.   A swap of two adjacent digits.
2.   A permutation of 3 adjacent digits.
3.   A permutation from digit positions (1, 2, 3, 4) to (3, 4, 1, 2),
or a permutation from digit positions (1, 2, 3, 4) to (4, 3, 2, 1).

The check digits can be generated in a simple manner without
computation.
The following two basic operations are defined:
1.  Sum Operation:  The sum operation is defined in the
Addition Table.  The sum of two hexadecimal digits i and j is given
by the entry at the intersection of the column with heading i and the
row with heading j in the Addition Table. For example, the sum of two
hexadecimal digits 9 and C is 5.
2.  Shift Operation:  The shift of digit i is denoted by H(i) and
is specified by the Shift Table.  For example, the shift of 5 is H(5)
= E.
The encoding procedure comprises the following steps:
1.   Two check digits P1 and P2 will be generated for a set of n
hexadecimal digits D(1,2,.....,n), where n is even.
2.   Set i = 0, and set P1 and P2 to be hex digit 0.
3.   Let P1 = Sum of P1 and D(i+1) Let P2 = Sum of P2
and D(i+2). 4.   Let P1 = H(P1) Let P2 = H...