C++ Program to Calculate Sum of Natural Numbers

In the following example of C++ Program to Calculate Sum of Natural Numbers :

Positive integers 1, 2, 3, 4... are known as natural numbers.

This program takes a positive integer from user( suppose user entered n ) then, this program displays the value of 1+2+3+....+n.

Example : Sum of Natural Numbers using loop :

Program :

#include <iostream>
using namespace std;

int main() {
    int n, sum = 0;

    cout << "Enter a positive integer: ";
    cin >> n;

    for (int i = 1; i <= n; ++i) {
        sum += i;
    }

    cout << "Sum = " << sum;
    return 0;
}

Output :

Enter a positive integer: 27
Sum = 378

* This program assumes that user always enters positive number.

* If user enters negative number, Sum = 0 is displayed and program is terminated.