# 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 😉 