/**************************************************
 Program to calculate Factorial using recursion 
 * 
 * Enter a number: 4
 * 4! = 24
 ***************************************************/

#include<stdio.h> // include stdio.h library
long factorial(int num);

int main(void)
{    
    int n;

    printf("Enter a number: \n");
    scanf("%d", &n);

    printf("%d! = %ld", n, factorial(n));

    return 0; // return 0 to operating system
}

long factorial(int num)
{    

    //base condition
    if(num == 0)
    {
        return 1;
    }

    else
    {
        // recursive call
        return num * factorial(num -  1);
    }

}