A simple output manipulator: sethex
#include <iostream>
#include <iomanip>
using namespace std;


ostream &sethex(ostream &stream)
{
  stream.setf(ios::showbase);
  stream.setf(ios::hex, ios::basefield);

  return stream;
}

int main()
{
  cout << 256 << " " << sethex << 256;

  return 0;
}