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.

- Input upper limit to find sum of natural numbers. Store it in some variable say
`N`. - Initialize another variable to store sum of numbers say
`sum = 0`

. - 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++)`

. - Inside the loop add previous value of
`sum`with`i`. Which is`sum = sum + i`

. - 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 😉

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