C program 03

3. Find the factorial of a number.

The factorial of a positive number n is given by:

factorial of n (n!) = 1*2*3*4....n

The factorial of a negative number doesn't exist. And, the factorial of 0 is 1, 0! = 1

#include <stdio.h>

int main()

{

    int n, i;

    unsigned long long factorial = 1;

    printf("\nEnter an integer: ");

    scanf("%d",&n);

    /* show error if the user enters a negative integer*/

    if (n < 0)

        printf("Error! Factorial of a negative number doesn't exist.");

    else if(n==0)

            printf("Factorial of 0 = 1");

    else

    {

        for(i=1; i<=n; ++i)

        {

                factorial *= i;              /*     factorial = factorial*I      */

        }

        printf("Factorial of %d = %llu", n, factorial);

    }

    return 0;

}



Output