How to make a factorial Program in C++?

This program calculates the the factorial of an integer number entered by the user. The function uses for loop to calculate the factorial and returns the number. Program terminates if a non integer number is entered. This C language program uses for loop in just a single statement to calculates the factorial of integer number.

#include<conio.h>

#include<iostream.h>

void main(void)

{

int a=1,n,fn=1;                           //Variable Decileration

clrscr();                                    // // For Clear Screen

cout<<"Enter Your Number = ";    //For Geting any OutPut

cin>>n;                                    //For Geting any Input

for(a=1; a<=n; a++)                   //Looping

{

fn=fn*a;              

}

cout<<fn;                              //For Out put of Factorial Program

getch();                                  //For Stop a Screen for a while untill you press any key

}