C :: Variable Won't Change When Calculating Factorial In Euler Number Homework

I started to learn programming through this site two weeks or so ago. I've got a book with exercices and so on, and one of them involves calculating e within a tolerance given by the user.

The formula for calculating e is the summation of 1+(1/i!), where i -> n.

So, here's the code and I'll explain the problem below:

Code:

#include <stdio.h>
int main()
{
float error;
float terme;
float sumatori = 0;
int cicle_euler = 1;
int factorial;

[Code]...

For some reason, when I set factorial to cicle_factorial, factorial remains 0, which I find puzzling; the program always halts when 1 + sumatori is 2.0 no matter what error is.

This must be a common problem and I suspect it has to do with some distinction between variables inside a loop and variables outside it, but as I lack technical vocabulary I can't seem to find anything on Google.