If a Manager class is created as a subclass of Employee, do we need to write another operator<<?

That is, do we need both of these:

1. ostream operator<<(ostream& os, const Employee& e)
   
2.  ostream operator<<(ostream& os, const Manager& m)
     

Answer: No, provided some conditions are met:

1. We implement a public Employee virtual method that returns a string representation of Employee; for example, a toString() method.
2. We implement the operator<< using this toString() method:

    Defined in Employee.cpp 
   
      #include "Employee.h"
   
      ostream operator<<(ostream& os, const Employee& e)
      {
        os << e.toString();
        return os;
      }
   
        
   

3. We override toString() in the Manager subclass of Employee to print a representation of a Manager instance.

Then a Manager instance can be passed to the operator<< already written for Employee and the e.toString() will use Manager's implementation of toString().