jord1sole/luhn-implementation-c-

Luhn algorithm (credit card check-digit) implemented in C language

luhn-implementation-C-

Luhn algorithm (credit card check-digit) implemented in pure C language

Sample C function "check_number()" to check a numeric character string of any length with Luhn check-digit at end of string plus sample C function "calc_digit()" to calculate check-digit character for a given character string. The sample "main" C program accepts one or more number strings on the command line.

For an excellent description of the Luhn algorithm refer to the Wikipedia page http://en.wikipedia.org/wiki/Luhn_algorithm.

Test credit card account numbers can be found here: https://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm.

You may distribute and/or use for any purpose modified or unmodified copies of this software.

THIS SOFTWARE IS PROVIDED AS IS AND COMES WITH NO WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED. IN NO EVENT WILL THE AUTHOR BE LIABLE FOR ANY DAMAGES RESULTING FROM THE USE OF THIS SOFTWARE.

Bruce D. Lightner, La Jolla, California, USA, [email protected], http://www.lightner.net/bruce/