How to write an algorithm to find factorial of a given number ?

#include <stdio.h>

factorial()
{

int p = 1;
int i = 1;
int n;
printf("Enter a Number greater than 0 \n");
scanf("%d",&n);
while ( i <= n)
{
p = p * i;
i = i + 1;
}

printf("Factorial of the input is %d \n",p);
}