functn to double a given value

#include<iostream.h>
#include<conio.h>
int two(int);  // use int two(int&) for call by ref.
void main()
{
clrscr();
int x;
cout<<"enter the no: ";
cin>>x;
cout<<" double the no is: "<<two(x);
getch();
}
int two(int x)    // use int two(int&x) for call by ref.
{
int c=2*x;
return c;
}