In C++ polymorphism terminology, what is meant by late binding, and how does late binding relate to virtual functions and runtime dispatch?

Introduction / Context:
Late binding is another term for dynamic binding in object oriented programming. In C++, it occurs primarily with virtual functions. Understanding late binding is important for working with polymorphic class hierarchies and predicting how function calls behave when using base class pointers and references. This question asks you to define late binding and relate it to runtime dispatch of virtual functions.

Given Data / Assumptions:

• We have a base class with one or more virtual member functions.
• Derived classes override these virtual functions with their own implementations.
• We call these functions through pointers or references to the base class.
• The language mechanism for selecting the implementation is either static at compile time or late at runtime.

Concept / Approach:
Late binding refers to binding a function call to the function implementation as late as possible, which in C++ is at runtime in the case of virtual functions. The compiler generates dispatch tables (virtual tables) that are consulted when a call is made via a base class pointer or reference. The call is routed to the correct implementation based on the dynamic type of the object, not simply the static type of the variable. The correct option must emphasise the runtime nature of this decision and its connection to virtual functions.

Step-by-Step Solution:
Step 1: Recall that for nonvirtual functions, the compiler knows exactly which function body to call at compile time and binds the call statically. Step 2: For virtual functions, the compiler knows only that the function is virtual and that the exact override will be determined later based on the object's dynamic type. Step 3: At runtime, when you call a virtual function through a base pointer or reference, the dispatch mechanism uses the object's virtual table to choose the correct overriding function. Step 4: This runtime selection is what is meant by late binding. Step 5: Option (a) describes this precisely: the decision is made at runtime based on the dynamic type rather than being fixed at compile time.

Verification / Alternative check:
To verify, imagine a base class Animal with a virtual speak function, and derived classes Dog and Cat that override speak. If you have Animal *p = new Dog(); and call p->speak();, the call resolves to Dog::speak at runtime. If you later assign p = new Cat(); and call p->speak(); again, it resolves to Cat::speak. The specific implementation is not baked in at compile time; it is chosen at runtime depending on what p actually points to. This is a clear demonstration of late binding.

Why Other Options Are Wrong:
Option (b) refers to behaviour in an editor and has nothing to do with language semantics. Option (c) describes static binding, the opposite of late binding. Option (d) is wrong because C++ requires that functions be defined; late binding does not allow calling non existent functions.

Common Pitfalls:
A common pitfall is to assume that late binding applies to all member functions; in C++, only virtual functions participate in late binding by default. Another mistake is to confuse late binding with dynamic linking of libraries, which is an operating system and linker concept. Remembering that late binding in C++ is specifically about runtime dispatch of virtual functions helps avoid these confusions.

Final Answer:
Late binding means that the decision about which virtual function implementation to call is made at runtime based on the object's dynamic type rather than at compile time.