Pure virtual classes

class EmployeeInterface {
public:
virtual $\tilde{\;}$ EmployeeInterface() { }
virtual void getEmployeeType(void) = 0;
};

class Employee : public virtual EmployeeInterface {...};
class Empowered : public Employee, public virtual EmployeeInterface {...};
class Manager : public Empowered, public virtual EmployeeInterface {...};

void use(EmployeeInterface* e) {...}
...
use(&e1); // output: Employee
use(&e2); // output: Empowered
use(&e3); // output: Manager

• Code behaves as before, but clearer architecture
• public virtual inheritance: avoids having many copies of EmployeeInterface in Empowered and Manager