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Polymorphism in C++ is a core principle of Object-Oriented Programming (OOP) that means "many forms." It allows objects of different classes to be treated as objects of a common type, enabling a single interface to represent different underlying implementations. This flexibility enhances code reusability, maintainability, and extensibility.
There are two main types of polymorphism in C++: Compile-time Polymorphism (Static Polymorphism).
This type of polymorphism is resolved during the compilation phase. It is achieved through:
Function Overloading: Defining multiple functions with the same name but different parameters (number, type, or order of arguments). The compiler determines which function to call based on the arguments provided during the function call.
Operator Overloading: Redefining the behavior of operators (like +, -, *, /) for user-defined data types.
Runtime Polymorphism (Dynamic Polymorphism).
This type of polymorphism is resolved during program execution. It is achieved primarily through:
Virtual Functions: Declaring a function in a base class as virtual. This allows derived classes to provide their own implementations of that function, and the correct version is called based on the actual object type at runtime, even when accessed through a base class pointer or reference.
Abstract Classes and Pure Virtual Functions: A class containing at least one pure virtual function (declared with = 0) becomes an abstract class and cannot be instantiated directly. Derived classes must implement all pure virtual functions to become concrete classes. This enforces a specific interface for derived classes.