C++ Polymorphism: Compile-Time vs Runtime Polymorphism & Overriding

Polymorphism (Greek for "many forms") enables a single interface to control a general class of actions. In C++, polymorphism manifests in two distinct forms: Compile-Time (Static) and Runtime (Dynamic).

Polymorphism Type	Resolution Mechanism	Language Features	Performance
Compile-Time (Static)	Compiler resolves addresses during compilation	Function Overloading, Operator Overloading, Templates	Zero overhead (Fastest)
Runtime (Dynamic)	Resolved at execution time via VTable pointers	Virtual Functions, Abstract Base Classes, Method Overriding	Minor pointer indirection (~1 nanosecond)

Frequently Asked Questions (FAQ) - Student & Interview Review

Q1. What is the difference between Function Overloading and Function Overriding in C++?

Function Overloading occurs within the same scope where functions share a name but differ in parameter signatures (Compile-Time). Function Overriding occurs in derived classes where a child class re-implements a virtual function with the exact same signature as the base class (Runtime).

Q2. What is the purpose of the 'override' keyword in C++11?

The 'override' keyword tells the compiler that the member function is intended to override a virtual function in a base class. If the base signature does not match (e.g. typos, mismatched const), the compiler immediately raises a compile error.