Since reading *Effective C++*, I've increasingly felt that I should relearn C++. But I'll start by piecing together fragmented knowledge and gradually move forward.
**Polymorphism**
Refers to the different implementation actions produced when the same object receives different messages or different objects receive the same message. C++ supports two types of polymorphism: compile-time polymorphism and runtime polymorphism.
a. **Compile-time polymorphism**: Achieved through function overloading.
b. **Runtime polymorphism**: Achieved through virtual functions.
A class containing a pure virtual function is called an abstract class. Since abstract classes contain pure virtual functions that are not defined, it is not possible to define objects of an abstract class.