Early Binding and Late Binding in CPP

Introduction

Imagine you’re playing a video game where you can choose different characters. Each character has unique abilities, but the game controls remain the same. This is similar to late binding in C++, where different objects can respond to the same function call in their unique ways. Now, imagine a board game where each player has a fixed set of moves. You know exactly what each move will do. This is similar to early binding in C++, where the function to be executed is known at compile time.

What Is Early Binding in C++?

Early Binding, also known as Static Binding or Compile-time Binding, is a concept in C++ programming where the association between a function call and the function to be executed is determined at compile time. This means that during the compilation process, the compiler can figure out which function needs to be called based on the information available at that time.

In early binding, the function call is resolved using the static type of the object, which is known at compile time. This allows for faster execution because the compiler knows exactly which function to call, and there’s no need to look up the appropriate function at runtime.

Here are some key points about early binding:

• Compile-Time Resolution: The function to be called is determined by the compiler based on the type of object that the function is called upon.
• Faster Execution: Since the function call is resolved at compile time, there’s no runtime overhead to determine the function to be executed. This makes early binding faster compared to late binding.
• Function Overriding: In cases of function overriding (when a derived class provides a specific implementation of a function present in the base class), early binding works as expected if the function is not virtual.

Syntax for Early Binding:

#include <iostream>
using namespace std;

class Base {
public:
    void show() {
        cout << "Base class function" << endl;
    }
};

class Derived : public Base {
public:
    void show() {
        cout << "Derived class function" << endl;
    }
};

int main() {
    Base b;
    Derived d;

    Base* ptr = &d;  // Pointer of base class type pointing to a derived class object
    ptr->show();     // Calls the function based on the static type (early binding)

    return 0;
}

Output:

Base class function

Explanation:

• The code defines a base class Base with a member function show() that prints “Base class function”.
• A derived class Derived is created that inherits from the Base class. It also has a member function show() that prints “Derived class function”.
• In the main() function:
• An object of Base class (b) and an object of Derived class (d) are created.
• A pointer ptr of type Base* (pointer to the base class) is declared and initialized to point to the d object (derived class object).
• When ptr->show(); is called, it invokes the show() function. However, due to early binding (static binding), the function call is determined by the pointer’s type, which is Base*. Therefore, the output is “Base class function”.

What Is Late Binding in C++?

Late binding in C++ refers to the process of determining which function to call at runtime, rather than at compile time. It is also known as dynamic binding or runtime polymorphism. This allows for more flexible and versatile code, particularly in scenarios where different classes inherit from a common base class and may have different implementations of the same function.

The key concept behind late binding is achieved through the use of virtual functions. A virtual function is declared in the base class and then overridden in the derived classes. When a function is declared as virtual in the base class, it indicates that it can be redefined in derived classes, and the appropriate function to call will be determined at runtime.

Here’s how it works: when a pointer or reference to a base class object points to a derived class object, the function call is resolved based on the actual object type it’s pointing to. This means that even if the function call is made through a base class pointer or reference, the appropriate derived class version of the function will be invoked.

Let’s explain this with a simple example:

#include <iostream>

// Base class
class Shape {
public:
    // Virtual function to be overridden by derived classes
    virtual void draw() {
        std::cout << "Drawing a shape." << std::endl;
    }
};

// Derived class - Circle
class Circle : public Shape {
public:
    void draw() override {
        std::cout << "Drawing a circle." << std::endl;
    }
};

// Derived class - Square
class Square : public Shape {
public:
    void draw() override {
        std::cout << "Drawing a square." << std::endl;
    }
};

int main() {
    Shape* shape1 = new Circle();  // Creating a Circle object
    Shape* shape2 = new Square();  // Creating a Square object

    shape1->draw();  // Output: Drawing a circle.
    shape2->draw();  // Output: Drawing a square.

    delete shape1;   // Cleaning up memory
    delete shape2;

    return 0;
}

Output:

Drawing a circle.
Drawing a square.

Explanation:

• We have a base class Shape with a virtual function draw(), which will be overridden by derived classes.
• The derived classes Circle and Square inherit from the Shape class and override the draw() function to provide their own implementation.
• In the main() function:
• We create a Circle object using a pointer of type Shape*, which demonstrates polymorphism (a derived class object assigned to a base class pointer).
• We also create a Square object using another pointer of type Shape*.
• Calling shape1->draw() and shape2->draw() invokes the overridden draw() functions of Circle and Square classes, respectively.
• After using the objects, we delete them using delete to release the allocated memory.

Understand by Detailed Diagram

Here’s a detailed diagram showing the concepts of Early Binding and Late Binding in C++.

Explanation:

Early Binding:

• Compile-time binding: The function call is resolved at compile time.
• Example: Function overloading is an example of Early Binding.
• Efficiency: It’s more efficient as the binding is resolved at compile time.

Late Binding:

• Run-time binding: The function call is resolved at run time.
• Example: Virtual functions in C++ are an example of Late Binding.
• Flexibility: It’s more flexible but can be less efficient compared to Early Binding.

Difference between Early and Late Binding

A Problem to Solve

Problem Statement

You are working on a drawing application that supports various shapes like circles, rectangles, and triangles. Your task is to create a program that utilizes both early binding and late binding to draw and describe these shapes.

Early Binding Task:

• Create Base Class “Shape”: Create a class called “Shape” that has a virtual function draw() and another function describe() which is not virtual.
• Derive Classes “Circle”, “Rectangle”, and “Triangle”: Derive these classes from “Shape”. Override the draw() method in each derived class to print a message like “Drawing a Circle” but do not override the describe() method.
• Test Early Binding: In the main function, create objects of the derived classes and call the describe() method on them to demonstrate early binding.

Late Binding Task:

• Override Virtual Method: In the derived classes, you’ve already overridden the draw() method. This will be used to demonstrate late binding.
• Test Late Binding: In the main function, create pointers of the base class type and assign them the addresses of objects of the derived classes. Call the draw() method using these pointers to demonstrate late binding.

Expected Output

The output of the program should look something like this:

Drawing using early binding:
Description of Shape
Description of Shape
Description of Shape

Drawing using late binding:
Drawing a Circle
Drawing a Rectangle
Drawing a Triangle

Guidelines

• Early binding occurs when the method being called upon an object is determined at compile-time.
• Late binding (or dynamic binding) occurs when the method being called is determined at run-time, often achieved using virtual functions in C++.

Additional Challenge

• Allow the user to choose the shape, and depending on the user’s choice, draw and describe the shape dynamically.

The Pros and Cons of Using Early and Late Binding

Key Takeaways

• Early Binding: In early binding, the function to be called is determined at compile time. It is also known as static binding. It leads to faster execution but less flexibility.
• Late Binding: Late binding, also called dynamic binding, decides the function to call at runtime. This provides more flexibility as the decision is based on the actual object type.
• Compile Time: Early binding is resolved during the compile phase, which makes it faster as the compiler knows the exact function to be called.
• Runtime: Late binding occurs during runtime, allowing different derived classes to call their specific overridden functions, providing more dynamic behavior.
• Efficiency vs. Flexibility: Early binding is efficient but less flexible, while late binding offers flexibility but might involve a slight runtime overhead.

Conclusion

Understanding early and late binding in C++ is pivotal for efficient and adaptable programming. Early binding, where the compiler determines the method call at compile time, often leads to more optimized code as the compiler knows exactly which function needs to be called. Late binding, on the other hand, decides the method call at runtime, allowing for more flexibility and dynamic behavior. This enables functionalities like polymorphism, where a base class reference can be used to call derived class functions.

Mastering these concepts is essential for creating robust programs, and it’s central to object-oriented design principles. It opens doors to new ways of structuring code, offering both efficiency and flexibility where needed. By practicing and using early and late binding where appropriate, aspiring programmers can upgrade their coding skills, write more maintainable code, and leverage the full potential of C++’s rich feature set.

FAQs

• What are early and late binding in C++?
  • Early binding in C++ is a process in which the function call is resolved at compile time. Late binding, on the other hand, is a concept where the function to be invoked is determined at runtime.
• Why do we use early and late binding in C++?
  • We use early binding in C++ to make our programs more efficient. Since the function call is resolved at compile time, the compiler can optimize the code better. We use late binding to make our programs more flexible. It allows a base class pointer to control objects of different derived classes.
• How do we use early and late binding in C++?
  • We use early binding when a non-virtual function is called or when a function is called on an object, not a pointer or a reference. We use late binding with the help of virtual functions and pointers or references of base class type.
• Can using early and late binding make code more confusing?
  • If used incorrectly, early and late binding can make your code less efficient or less flexible. It’s important to understand how early and late binding work and when to use them.
• What are some examples of using early and late binding in C++?
  • Some examples include calling a specific function on an object of a specific class (early binding) and calling a function on a base class pointer that points to an object of a derived class (late binding).