** fac **

**Details**

Returns the factorial of an integer number. The factorial of a number N is determined as follows: N! = 1 x 2 x 3 x 4 x ... x N, however factorial of 0 is 1.

**Parameters**

val = any integer number

**Example**

Fac(5) returns 120

Fac(0) returns 1

**Note**

Fac() cannot take unit as arguments. Negative number will cause an error.