Overloading input/output operators in C++

In C++, stream insertion operator << is used for output and stream extraction operator >> is used for input.

cout is an object of ostream class which is a compiler defined class. When we do cout<<obj where obj is an object of our class, the compiler first looks for an operator function in ostream, then it looks for a global function. One way to overload insertion operator is to modify ostream class which may not be a good idea. So we make a global method and if we want to allow them to access private data members of class, we must make them friend.

#include <iostream>
using namespace std;

class Complex
{
private:
int real, imag;
public:
Complex(int r = 0, int i =0)
{ real = r; imag = i; }
friend ostream & operator << (ostream &out, const Complex &c);
friend istream & operator >> (istream &in, Complex &c);
};

ostream & operator << (ostream &out, const Complex &c)
{
out << c.real;
out << "+i" << c.imag << endl;
return out;
}

istream & operator >> (istream &in, Complex &c)
{
cout << "Enter Real Part ";
in >> c.real;
cout << "Enter Imagenory Part ";
in >> c.imag;
return in;
}

int main()
{
Complex c1;
cin >> c1;
cout << "The complex object is ";
cout << c1;
return 0;
}