C Program to Find the Sum of First N Natural Numbers

This C Program calculates the sum of first N natural numbers.

Here is source code of the C program to calculate the sum of first N natural numbers. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

  1. /*
  2.  * C program to find the sum of 'N' natural numbers
  3.  */
  4. #include <stdio.h>
  6. void main()
  7. {
  8.     int i, num, sum = 0;
  10.     printf("Enter an integer number \n");
  11.     scanf ("%d", &num);
  12.     for (i = 1; i <= num; i++)
  13.     {
  14.         sum = sum + i;
  15.     }
  16.     printf ("Sum of first %d natural numbers = %d\n", num, sum);
  17. }

$ cc pgm3.c
$ a.out
Enter an integer number
Sum of first 1300 natural numbers = 845650
$ a.out
Enter an integer number
Sum of first 15 natural numbers = 120

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If you wish to look at other example programs on Mathematical Functions, go to C Programming Examples on Mathematical Functions. If you wish to look at programming examples on all topics, go to C Programming Examples.
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