credit card validator in c++ project

Table of Contents

Source Code

#include <iostream>

using namespace std;

bool validate_card(string card_number) {
    int sum = 0;
    bool alternate = false;

    // Iterate through the card number in reverse order
    for (int i = card_number.length() - 1; i >= 0; i--) {
        // Get the current digit
        int digit = card_number[i] - '0';

        // If the current digit is an alternate digit
        if (alternate) {
            digit *= 2;
            if (digit > 9) {
                digit -= 9;
        sum += digit;
        alternate = !alternate;

    return (sum % 10 == 0);

string get_card_type(string card_number) {
    string card_type;
    char first_digit = card_number[0];

    switch (first_digit) {
        case '4':
            card_type = "Visa";
        case '5':
            card_type = "Mastercard";
        case '3':
            card_type = "American Express";
            card_type = "Unknown";
    return card_type;

Code Explanation

A credit card validator project in C++ could involve the following basic functions:

  1. validate_card(): This function would take in a credit card number as input and use the Luhn algorithm to check if the card is a valid number. If the number is valid, the function returns true, otherwise, it returns false.
  2. get_card_type(): This function would take in a credit card number as input and use the first few digits of the number to determine the type of card (e.g. Visa, Mastercard, American Express).
  3. main(): This function would handle the overall flow of the program, including prompting the user for a credit card number, calling the validate_card() and get_card_type() functions, and displaying the results to the user.