Decimal to Binary in C++

# include <iostream>
#include <math.h>
using namespace std ;
int main()
{
unsigned short int x=0,b=128 ,z=0,a=8 ;
cout<<"please enter the number between 0 and 255 \n";
cin >> x;
if (x>255)
cout<<" out of range ";
else
{
cout << x <<" converted to binary number :" ; 
 while (a!=0)
 {
  z=x&b ;
  if (z==128)
  cout << "1" ;
  else
  cout << "0";
  x=(x << 1);
  a-- ;
}
}
cout<<"\n";
system("pause");
return 0 ;
}