Sum of digits in C++

To calculate the sum of digits of an integer in C++, you can use a loop to extract each digit and add it to a running sum. Here’s a simple example:

#include <iostream>

int main() {
    int number, digit, sum = 0;

    // Input an integer
    std::cout << "Enter an integer: ";
    std::cin >> number;

    // Ensure the number is non-negative
    number = abs(number);

    // Calculate the sum of digits
    while (number > 0) {
        digit = number % 10; // Get the last digit
        sum += digit;        // Add the digit to the sum
        number /= 10;       // Remove the last digit
    }

    std::cout << "Sum of digits: " << sum << std::endl;

    return 0;
}

In this program:

1. The user is prompted to enter an integer.
2. The abs function is used to ensure that the number is non-negative, as the sum of digits doesn’t depend on the sign.
3. A while loop is used to extract each digit from the number. The last digit is obtained using the modulo operator (% 10), added to the sum variable, and then removed from the number using integer division (/ 10).
4. The sum variable keeps track of the sum of digits.
5. The program displays the sum of digits as the output.

Compile and run this program, and it will calculate and display the sum of the digits of the entered integer.