// reading a complete binary file
#include <iostream>
#include <fstream>
using namespace std;

ifstream::pos_type size;
char * memblock;

char c1,c2;

int main () {
    
    ifstream in1 ("a.fits", ios::in|ios::binary);
    ifstream in2 ("bla.bin", ios::in|ios::binary);
    
    if (in1.is_open() && in2.is_open())
    {                  
        long begin,end;
        begin = in1.tellg();
        in1.seekg (0, ios::end);
        end = in1.tellg();
        in1.seekg (0, ios::beg);
        cout << "a.fits  size:" << end-begin << endl;
        
        begin = in2.tellg();
        in2.seekg (0, ios::end);
        end = in2.tellg();
        in2.seekg (0, ios::beg);
        cout << "bla.bin size:" << end-begin << endl;
        
        while ( in1.good() && in2.good() )
        {
            c1 = in1.get();
            c2 = in2.get();
            if (c1 != c2)
            {
                cout << "difference found @ adress:" << hex << in1.tellg() << "\t" << in2.tellg() << endl;
                cout << "in1:" << hex << int(c1) << endl;
                cout << "in2:" << hex << int(c2) << endl;
            }
        }
        
        in1.close();
        in2.close();
  } //end of if file open
  
return 0;
} //end of main