Code in programming language C to create a validation machine to recognize the credit card numbers using the Luhn's Algorithm.
To iniciatize the code, first you need to insert a credit card number. It can be, according to Luhn's Algorithm: a) an invalid card number; b) American Express credit card, if the card number starts with 34 or 37 and have 15-digit numbers; c) Visa credit card, if the card number starts with 4 and have 13 and 16-digit numbers; d) Master credit card, if the card number starts with 51, 52, 53, 54 or 55 and have 16-digit numbers.
I've already debug and made tests beforehand but I accept changes in the section of commit changes. Feel free to give advice on my code or any suggestions!
This code was made in CS50 Harvard's EDx course.