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README.1ST
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1989-11-09
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53 lines
CREDCHK is a simple, handy utility for anyone who collects money via credit
cards, particularly when credit card numbers are obtained by telephone or
computer bulletin board system. It is Copyright 1989 by David L. Kidder and
all rights are reserved. However, it is released into the public domain upon
the express condition that it is not altered in any way and that no charge is
made for its distribution other than nominal copying charge (under $8) or
normal BBS membership fees.
To use the program, merely enter CREDCHK at the DOS prompt and press carriage
return. The rest should be self-explanatory.
Upon entering a credit card number, CREDCHK first verifies the proper number
of digits (11-16) and a valid first digit (3, 4, 5 or 6). It then performs
the standard "MODULUS-10" check digit procedure. "OK!" is displayed if the
number passes all tests. Otherwise, "INVALID NUMBER!" is displayed.
The program works for the following types of cards:
American Express (first digit = 3)
Visa (first digit = 4)
MasterCard (first digit = 5)
Discover (first digit = 6)
It will reject other types of cards - Department Store cards, Gasoline Credit
Cards, etc. - even if the other parameters, including first digit, are correct
and the account is valid.
The primary purpose of the CREDCHK program is to catch card number entry
errors. This is particularly important in situations such as BBS systems and
telephone ordering where the cardholders themselves may make mistakes. It is
unlikely this program will catch fraudulent purchases by "professionals".
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IMPORTANT!
CREDCHK can only check credit card numbers for validity of format. It is
not designed to be a substitute for your Merchant's Warning Bulletin! It
cannot check to see if a card has been lost, stolen, cancelled or if the
cardholder is over his limit. Use CREDCHK solely as a convenient first check
and do not abandon your other verification procedures!
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If you find this program useful - or if you find a bug - please let me know.
David Kidder
Take 3 Inc.
4839 E. Greenway
Suite 335
Scottsdale, AZ 85254
Voice: 602-420-1801
Data: 602-482-1001