Employee Class vtable

In the Employee class vtable, the first function pointer is set to 0 (i.e., nullptr), because function earnings is a pure virtual function and therefore lacks an implementation. The second function pointer points to function print, which displays the employee’s full name and social security number. [Note: We’ve abbreviated the output of each print function in this figure to conserve space.] Any class that has one or more null pointers in its vtable is an abstract class. Classes without any null vtable pointers (such as SalariedEmployee, CommissionEmployee and BasePlusCommissionEmployee) are concrete classes.