C Program to Find Sum of Natural Numbers Using Recursion

In mathematics, natural numbers (1, 2, 3, 4, ...) are used for counting and ordering. Some definitions of natural numbers include 0 as the first number, but that doesn't really matter for finding the sum of natural numbers.

This C program finds the sum of first n natural numbers using a recursive function.

C Source Code: Sum of First n Natural Numbers Using Recursion

#include<stdio.h>
#include<conio.h>

/* function prototype */
int sum(int n);

int main()
{
 int term, result;

 clrscr();
 printf("Enter number of terms (positive integer): ");
 scanf("%d", &term);

 /* function call */
 result = sum(term);

 printf("Sum of first %d natural numbers is %d", term, result);

 getch();
 return 0;
}

int sum(int n)
{
 int s=0;

 if(n<=0)
 {
  return 0;
 }

 return n + sum(n-1);
}

Output

The output of the above program is:

Enter number of terms (positive integer): 9
Sum of first 9 natural numbers is 45