Using simple algorithm the credit card number can be validated. Each credit card type has his own rules for numbers to start from and for lengh of the number. IssuerIdentifier Card Number Length Diner's Club/Carte Blanche 300xxx-305xxx,36xxxx, 38xxxx 14 American Express 34xxxx, 37xxxx 15 VISA 4xxxxx 13, 16 MasterCard 51xxxx-55xxxx 16 Discover 6011xx 16 Following article explains in details what means digits in credit card numbers. More full example with source code can be found here .
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