This repository contains a C implementation of a Credit Card Validator program that checks the validity of credit card numbers using Luhn's Algorithm. The program prompts the user for a credit card number and reports whether it is a valid American Express, MasterCard, Visa card, or invalid.
Credit Card Validator implements Luhn's Algorithm to determine the syntactical validity of credit card numbers. It supports American Express (15-digit), MasterCard (16-digit), and Visa (13 or 16-digit) card numbers. The program performs checksum calculations and verifies the structure of credit card numbers.
To use the Credit Card Validator, follow these steps:
- Clone this repository:
git clone https://github.com/excel-asaph/credit-card-validator.git
cd credit-card-validator- Compile and run the program:
To compile the program, you can use the gcc compiler along with the provided Makefile. Follow these steps:
gcc -o creditcard_main creditcard_main.c get_card_length.c get_count_outcome.c amex_first_digit.c amex_second_digit.c visa_master_first_digit.c visa_master_second_digit.c visa_first_digit.c second_to_last.c lasts.c -lcs50
./creditcard_mainMain program file responsible for user input and validation result output.
/**
* @file get_card_length.c
* @brief Implementation of the function to get the length of a credit card number.
*/
/**
* @brief Gets the length of the credit card number.
*
* This function calculates the length of the provided credit card number by iteratively
* dividing it by 10 until the number becomes zero.
*
* @param card The credit card number.
* @return The length of the credit card number.
*/
long get_card_length(long card);/**
* @file get_count_outcome.c
* @brief Implementation of the function to determine the validity of a credit card number based on its length.
*/
/**
* @brief Determines the validity of the credit card number based on its length.
*
* This function returns 1 if the length is not 13, 15, or 16, indicating an invalid length.
*
* @param count The length of the credit card number.
* @return 1 if invalid, 0 if valid.
*/
int get_count_outcome(int count);/**
* @file amex_first_digit.c
* @brief Implementation of the function to retrieve the first digit of an American Express credit card.
*/
/**
* @brief Retrieves the first digit of an American Express credit card.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The first digit of the credit card.
*/
int amex_first_digit(int count, long card);/**
* @file amex_second_digit.c
* @brief Implementation of the function to retrieve the second digit of an American Express credit card.
*/
/**
* @brief Retrieves the second digit of an American Express credit card.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The second digit of the credit card.
*/
int amex_second_digit(int count, long card);/**
* @file visa_master_first_digit.c
* @brief Implementation of the function to retrieve the first digit of a Visa or MasterCard.
*/
/**
* @brief Retrieves the first digit of a Visa or MasterCard.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The first digit of the credit card.
*/
int visa_master_first_digit(int count, long card);/**
* @file visa_master_second_digit.c
* @brief Implementation of the function to retrieve the second digit of a Visa or MasterCard.
*/
/**
* @brief Retrieves the second digit of a Visa or MasterCard.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The second digit of the credit card.
*/
int visa_master_second_digit(int count, long card);/**
* @file visa_first_digit.c
* @brief Implementation of the function to retrieve the first digit of a Visa credit card.
*/
/**
* @brief Retrieves the first digit of a Visa credit card.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The first digit of the credit card.
*/
int visa_first_digit(int count, long card);/**
* @file second_to_last.c
* @brief Implementation of the function to perform calculations on every other digit, starting from the second-to-last digit.
*/
/**
* @brief Performs calculations on every other digit, starting from the second-to-last digit.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The sum of calculated values.
*/
int second_to_last(int count, long card);/**
* @file lasts.c
* @brief Implementation of the function to perform calculations on the remaining digits.
*/
/**
* @brief Performs calculations on the remaining digits.
*
* @param count The length of the credit card number.
* @param card The credit card number.
* @return The sum of calculated values.
*/
int lasts(int count, long card);/**
* @file creditcard_main.c
* @brief Main file for the Credit Card Validity Checking program.
*/
/**
* @brief Main function to check the validity of a credit card number.
*
* This function prompts the user for a credit card number, performs various checks
* using helper functions, and prints the type of the credit card if it's valid.
*
* @return 0 if the program executes successfully.
*/
int main(void);The program utilizes Luhn's Algorithm, a process that involves the following steps:
- Multiply every other digit by 2.
- Sum the digits of those products.
- Add the sum to the sum of the digits that weren't multiplied by 2.
- Check if the total's last digit is 0.
Contributions are welcome! If you'd like to contribute to this project, please follow these steps:
- Fork the repository
- Create a new branch (
git checkout -b feature/new-feature) - Make your changes and commit them (
git commit -am 'Add new feature') - Push to the branch (
git push origin feature/new-feature) - Create a pull request
This project is licensed under the MIT License - see the LICENSE file for details.
Note: This project uses the CS50 library for input, credit to CS50 for the library.