ccsun1 :oop % 
ccsun1 :oop % cat -n bin.cpp
     1  //a simple class for binary number
     2  #include <iostream.h>
     3  class BIN{
     4          long data;
     5      friend ostream& operator<< (ostream&, const BIN&);
     6      public:
     7          BIN(){data=0;};
     8          BIN(long);
     9          BIN(BIN& x)   // copy constructor
    10          { cout << "(copy)";    // data = x.data;
    11          }
    12  };
    13  BIN::BIN(long x) { data=x; }
    14  int main()
    15  {
    16          long m;
    17          BIN y;
    18     m=126;
    19     y=m;
    20     cout << "m=" << m;
    21     cout << "=== y =" << y << endl;;
    22     BIN x=y; // will call copy constructor
    23     cout << "\t x= " << x << " Note\n";
    24     cout << "What if the copy constructor is removed?\n\n";
    25     while(m){
    26        cout << "Input an integer:";
    27        cin >> m;
    28        cout << "===" << (BIN)m;
    29        cout << " = " << m << endl;
    30     }
    31     cout << "Thank you for using AT&T:-)\n";
    32  }
    33  ostream& operator<< (ostream& oo, const BIN& x)
    34  {
    35          long tmp,i;
    36          tmp = x.data;
    37          for(i=1; i<=32; i++){
    38             if(tmp<0) oo << 1;
    39             else oo << 0;
    40             if(i%4 == 0) cout << " ";   // Ohh .. bug?
    41             tmp = tmp << 1;
    42          }
    43          return oo;
    44  }
ccsun1 :oop % g++ bin.cpp
ccsun1 :oop % ./a.out
m=126=== y =0000 0000 0000 0000 0000 0000 0111 1110 
(copy)   x= 0000 0000 0000 0000 0000 0000 0000 0000 Note
What if the copy constructor is removed?

Input an integer:3
===0000 0000 0000 0000 0000 0000 0000 0011  = 3
Input an integer:127
===0000 0000 0000 0000 0000 0000 0111 1111  = 127
Input an integer:128
===0000 0000 0000 0000 0000 0000 1000 0000  = 128
Input an integer:256
===0000 0000 0000 0000 0000 0001 0000 0000  = 256
Input an integer:-1
===1111 1111 1111 1111 1111 1111 1111 1111  = -1
Input an integer:-2
===1111 1111 1111 1111 1111 1111 1111 1110  = -2
Input an integer:0
===0000 0000 0000 0000 0000 0000 0000 0000  = 0
Thank you for using AT&T:-)
ccsun1 :oop % 
ccsun1 :oop % exit