C++ Program to Find the Sum of Natural Numbers

1. Introduction

Natural numbers are the set of positive integers starting from 1 and extending indefinitely. They play a foundational role in arithmetic and number theory. In this post, we will create a C++ program to find the sum of n natural numbers.

2. Program Overview

The formula to calculate the sum of the first n natural numbers is given by:
Sum = n * (n + 1) / 2

Using this formula, our program will:

1. Prompt the user to enter the value of n.

2. Compute the sum of the first n natural numbers.

3. Display the calculated sum.

3. Code Program

#include <iostream>
using namespace std;

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

    // Prompting the user for the value of n
    cout << "Enter a positive integer: ";
    cin >> n;

    // Calculating the sum
    sum = n * (n + 1) / 2;

    // Displaying the result
    cout << "The sum of first " << n << " natural numbers is: " << sum;

    return 0;  // Signify successful program termination


Enter a positive integer: 5
The sum of first 5 natural numbers is: 15

4. Step By Step Explanation

1. Headers and Namespace: We initiate by including the iostream library for input-output operations and specifying the use of the standard namespace.

2. Main Function: The program starts its execution from here. Inside, we declare two integer variables - n to store the user input and sum to store the result.

3. User Input: We utilize cout to prompt the user for input and cin to receive the number.

4. Calculation: Using the formula mentioned above, we quickly compute the sum of the first n natural numbers.

5. Displaying the Result: The sum is then printed out using cout.

6. Program Termination: The program concludes, indicating a successful execution with a return value of 0.