C program to find sum of natural numbers from 1 to n

Write a C program to find the sum of all natural numbers between 1 to n using for loop. How to find sum of natural numbers in a given range in C programming. Logic to find sum of all natural numbers in a given range in C programming.

Example

Input

Input upper limit: 10

Output

Sum of natural numbers 1-10: 55

Required knowledge

Basic C programming, Relational operators, For loop

Logic to find sum of natural numbers from 1 to n

Step by step descriptive logic to find sum of n natural numbers.

  1. Input upper limit to find sum of natural numbers. Store it in some variable say N.
  2. Initialize another variable to store sum of numbers say sum = 0.
  3. In order to find sum we need to iterate through all natural numbers between 1 to n. Initialize a loop from 1 to N, increment loop counter by 1 for each iteration. The loop structure should look like for(i=1; i<=N; i++).
  4. Inside the loop add previous value of sum with i. Which is sum = sum + i.
  5. Finally after loop print the value of sum.

Program to find sum of natural numbers from 1 to n

/**
 * C program to find sum of natural numbers between 1 to n
 */

#include <stdio.h>

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

    /* Input upper limit from user */
    printf("Enter upper limit: ");
    scanf("%d", &n);

    /* Find sum of all numbers */
    for(i=1; i<=n; i++)
    {
        sum += i;
    }

    printf("Sum of first %d natural numbers = %d", n, sum);

    return 0;
}

Note: In above program I have used shorthand assignment operator sum += i which is equivalent to sum = sum + i.

Output

Enter upper limit: 10
Sum of first 10 natural numbers = 55

Program to find sum of natural numbers in given range

/**
 * C program to find sum of natural numbers in given range
 */

#include <stdio.h>

int main()
{
    int i, start, end, sum=0;

    /* Input lower and upper limit from user */
    printf("Enter lower limit: ");
    scanf("%d", &start);
    printf("Enter upper limit: ");
    scanf("%d", &end);

    /* Find sum of all numbers */
    for(i=start; i<=end; i++)
    {
        sum += i;
    }

    printf("Sum of natural numbers from %d to %d = %d", start, end, sum);

    return 0;
}

Output

Enter lower limit: 10
Enter upper limit: 15
Sum of natural numbers from 10 to 15 = 75

Happy coding 😉

About Pankaj

Pankaj Prakash is the founder, editor and blogger at Codeforwin. He loves to learn new techs and write programming articles especially for beginners. He works at Vasudhaika Software Sols. as a Software Design Engineer and manages Codeforwin. In short Pankaj is Web developer, Blogger, Learner, Tech and Music lover.

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