Page 236 - DCAP404 _Object Oriented Programming

Unit 10: Virtual Functions and Polymorphism

 An abstract base class will not be used to create object, but exist only to act as a base class Notes
of other classes.

 Polymorphism allows the program to use the exactly same function name with exactly
same arguments in both a base class and its subclasses. It refers to the implicit ability of a
function to have different meanings in different contexts.

10.6 Keywords

Abstract Base Class: An abstract base class will not be used to create object, but exist only to act
as a base class of other classes.
Late Binding: Selecting functions during the execution. Though late binding requires some
overhead it provides increased power and flexibility.
Polymorphism: Polymorphism allows the program to use the exactly same function name with
exactly same arguments in both a base class and its subclasses.
Virtual Function: Virtual functions, one of advanced features of OOP is one that does not really
exist but it appears real in some parts of a program.
10.7 Review Questions

1. Make the distinction between virtual functions and virtual base class?
2. How can C++ achieve dynamic binding yet also static typing?
3. What is the difference between virtual and non-virtual member functions?
4. What happens in the hardware when we call a virtual function? How many layers of
indirection are there? How much overhead is there?
5. How can a member function in my derived class call the same function from its base class?
6. Write a program which uses a polymorphism with pointers.

7. Are virtual functions hierarchical? Give an example in support of your answer.
8. Write a program to use constructors and destructors in inheritance.
9. Debug the following program:

class one
{
int a;
public:
void set(int a)
{
a = a;

}
void show()
{
cout << a;

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