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/* Let's talk a little about the anatomy of a credit card:         */
/*                                                                 */
/*    ------------------------------------------------             */
/*    |                                              |             */
/*    |                                              |             */
/*    |                                              |             */
/*    |                                              |             */
/*    |   5 3 0 4    4 6 4 2   1 2 3 4   5 6 7 8     |             */
/*    |   |____________| |___________________| |     |             */
/*    |   |      |                 |         Checksum|             */
/*    |   |      |         Account Identifier        |             */
/*    |   |  BIN(Bank Identification Number)         |             */
/*    |MII(Major Industry Identifier)                |             */
/*    |                                              |             */
/*    ------------------------------------------------             */
/*                                                                 */
/* The first number is Major Industry Identifier (MII),            */
/* which tells you what sort of institution issued the card.       */
/*                                                                 */
/* 1 and 2 are issued by the airlines.                             */
/* 3 is issued by travel and entertainment                         */
/* 4 and 5 are issued by banking and financial institutions        */
/* 6 is issued by merchandising and banking                        */
/* 7 is issued by petroleum companies                              */
/* 8 is issued by telecommunications companies                     */
/* 9 is issued by national assignment                              */
/*                                                                 */
/* The first six digits are the Issuer Identification Number (IIN) */
/* These can be used to look up where the card originated from.    */
/* Here are a few you might recognize:                             */
/*                                                                 */
/* Visa: 4*****                                                    */
/* American Express (AMEX): 34**** or 37****                       */
/* Mastercard: 51**** to 55****                                    */
/*                                                                 */
/* The seventh digit to the second-to-last digit is the customer   */
/* account number. Most companies use just 9 digits for the        */
/* account numbers, but it's possible to use up to 12. This means  */
/* that using the current algorithm for credit cards, the world    */
/* can issue about a trillion cards before it has to change the    */
/* system.                                                         */
/*                                                                 */
/* The very last digit of a credit card is the check digit or      */
/* checksum. It is used to validate the credit card number using   */
/* the Luhn algorithm.                                             */
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