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

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 😉 