Virtual functions allow functions of derived classes to be called through pointers or references to the base class. This is known as polymorphism. For polymorphism to work, classes must inherit from a single base class and virtual functions must be declared in the base class. Polymorphism occurs at either compile-time or runtime depending on when the function call is bound to a definition.

1. Virtual Functions:
Chapter 11:
Ms. Munazza Mah Jabeen
Assistant Professor of Computer Science

2. Virtual Functions:
• Virtual means existing in appearance but not in reality. a program that
appears to be calling a function of one class may in reality be calling a
function of a different class.
• Completely different functions are executed by the same function call
i.e. draw(). This is called polymorphism, which means different forms.
• For the polymorphic approach to work, several conditions must be met.
• First, all the different classes of shapes, such as balls and triangles, must be
descended from a single base class.
• Second, the draw() function must be declared to be virtual in the base class.

3. Normal Member Functions Accessed with Pointers:

4. Virtual Member Functions Accessed with Pointers:

5. Binding:
Polymorphism is classified into 2 branches:
• Compile Time Polymorphism/Early Binding/Static
Binding
• Runtime Polymorphism/Late Binding/Dynamic
Binding
What is Binding?
• For every function call; compiler binds or links the
call to one function definition.
• This linking can happen at 2 different time
• At the time of compiling program, or
• At Runtime

6. Friend Functions & friend Classes:

7. Assignment and Copy Initialization/this pointer: