Calculating the recursive factorial of an integer in C

The factorial of a natural number  n is the product of integers less than or equal to it.
n! means that we start from n and we decrement until we reach the number 1.

n! = n * (n - 1)! * (n - 2)! * ... * 1

Example

The program that calculates the factorial of an integer:

#include< stdio.h> 
#include< stdlib.h> 

//iterative 
unsigned long fact (unsigned short value) {
 int res = 1; 
 for(int i = 1; i <= value; i++) {
 res *= i;
 }
 return res; 
}

//recursive
unsigned long fact_recursive (unsigned short number)
{
 if (number == 0)
 return 1; 
 else
 return number * fact_recursive(number - 1); 

}

int main()
{
 int number; 
 printf("Enter a number: "); 
 scanf("%d",& number); 
 printf("factorial of %d: %d\n",number,fact); 
 return 0; 
}

References:
La factorielles - wikipedia