1	//a simple class for binary number by tsaiwn@csie.nctu.edu.tw
     2	#include <iostream.h>
     3	class BIN{
     4	    protected: long data;   // so that can be accessed by derived class
     5	    friend ostream& operator<< (ostream&, const BIN&);
     6	    public:
     7	        BIN(){data=0;};
     8	        BIN(long);
     9	        BIN(BIN& x)   // copy constructor
    10	        { data = 3; cout << "(copy)";    // data = x.data;
    11	        }
    12	};
    13	BIN::BIN(long x) { data=x; }
    14	//////
    15	// new class inherit from BIN  (i.e., we reuse BIN to build a new class)
    16	class BINREAL: public BIN{
    17	     float fdata;
    18	    public:
    19	        BINREAL(){data=0; setBin( ); };
    20	        BINREAL(float x) { fdata=x; setBin( ); }
    21	        void setBin( ) {
    22	            long * ptemp = (long *) &fdata;
    23	            data = *ptemp;   // data = ptemp[0];
    24	        }
    25	};
    26	int main()
    27	{     float m;
    28	      BINREAL y;
    29	   m=1234567.3;   // actually it is 1234567.25
    30	   y=m;
    31	   cout << "m=" << m;
    32	   cout << "=== y =" << y << endl;;
    33	   BIN x=y; // will call copy constructor
    34	   cout << "\t\t x= " << x << " Note\n";
    35	   cout << "What if the copy constructor is removed?\n\n";
    36	   while(m){
    37	      cout << "Input a float number:";
    38	      cin >> m;
    39	      y = m;
    40	      cout << "===" << y;
    41	      cout << " = " << m << endl;
    42	   }
    43	   cout << "Thank you for using AT&T:-)\n";
    44	}
    45	ostream& operator<< (ostream& oo, const BIN& x)
    46	{
    47	        long tmp,i;
    48	        tmp = x.data;
    49	        for(i=1; i<=32; i++){
    50	           if(tmp<0) oo << 1;
    51	           else oo << 0;
    52	           if(i%4 == 0) cout << " ";   // Ohh .. bug?
    53	           tmp = tmp << 1;
    54	        }
    55	        return oo;
    56	}
    57	/*** answer:
    58	10:24am magpie::oop/> g++ binfloat.cpp
    59	10:25am magpie::oop/> ./a.out
    60	m=1.23457e+06=== y =0100 1001 1001 0110 1011 0100 0011 1010
    61	(copy)           x= 0000 0000 0000 0000 0000 0000 0000 0011  Note
    62	What if the copy constructor is removed?
    63	
    64	Input a float number:1234567.2
    65	===0100 1001 1001 0110 1011 0100 0011 1010  = 1.23457e+06
    66	Input a float number:0.25
    67	===0011 1110 1000 0000 0000 0000 0000 0000  = 0.25
    68	Input a float number:0.5
    69	===0011 1111 0000 0000 0000 0000 0000 0000  = 0.5
    70	Input a float number:1.0
    71	===0011 1111 1000 0000 0000 0000 0000 0000  = 1
    72	Input a float number:1.25
    73	===0011 1111 1010 0000 0000 0000 0000 0000  = 1.25
    74	Input a float number:1.75
    75	===0011 1111 1110 0000 0000 0000 0000 0000  = 1.75
    76	Input a float number:1.875
    77	===0011 1111 1111 0000 0000 0000 0000 0000  = 1.875
    78	Input a float number:0
    79	===0000 0000 0000 0000 0000 0000 0000 0000  = 0
    80	Thank you for using AT&T:-)
    81	10:26am magpie::oop/>
    82	*******************/