1. Polymorphism Encapsulation Inheritance
Polymorphism (from the Greek meaning "having multiple forms")
The ability for different objects derived from a common base object to respond to the same stimuli in a completely different ways.

2. Examples Pledge: “I, (state your name), do solemnly swear….”
UPE (Upsilon Pi Epsilon) pledge: "I ( state your name ), … having heard and understood ... the purposes and tenets of Upsilon Pi Epsilon ... do solemnly pledge, ... always to respect and promote ... the aims and ideals of this Society.”
Programing examples

3. Virtual Methods
Different derived classes respond to the same request in different ways.
A class provides virtual method, which allows any class derived from it to respond differently to the same request :
via override the virtual method in the derived class, and then call the method in the base class
Virtual methods
virtual void speak() {};
Pure virtual method
virtual void speak() = 0;

4. Run-time Binding
Virtual methods override by a method in a derived class
virtual void speak() override {};
Compare to general method override
Both require identical signature
Static binding (binding to the type that the method is called) in general method override
vs, run-time binding in the virtual method case (derived class type’s method overrides at the time of instantiate)

5. Which function to call? ClassA^ a=gcnew ClassB(); a->f();
Example:
ClassB derives from ClassA, and so on…
ClassA has a method f();
ClassB, ClassC, ClassD all implement own f();
Object
ClassA
ClassA^ a=gcnew ClassB();
a->f();
ClassB
ClassC
C++: virtual method
ClassD

6. Abstract ref class
An incomplete definition of a ref class that has at least one pure virtual member method;
Cannot instantiate an object of it;
A derived class of it must implement the pure virtual function, (or, it becomes abstract)

7. C++ Example How to check the earnings of different employee types?
Object
first, last,
Earnings, ToString
Employee
Boss
CommissionWorker
PieceWorker
HourlyWorker
salary,
Earnings, ToString
wagePerPiece, quantity
Earnings, ToString

8. Applications

9. Summary
Although virtual functions of a base class are called within a framework, the actual functions to be called at run time are that of the actual class derived from the base class.
Only base classes are needed to define a framework.
Dynamic Binding versus Static Binding