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ANNA UNIVERSITY • COURSE LECTURE PAGE

Operator Overloading in C++

Course: Fundamentals of C++ Programming

Unit: Object-Oriented Programming

Target Learners: Undergraduate Engineering Students

Instructor: Dr.K.Gokulakrishnan, Associate Professor, Electronics and Communication Engineering

Learning Objectives

• Define operator overloading in C++.
• Differentiate unary and binary operator overloading.
• Implement operator overloading using a class.
• Analyze the advantages and limitations of operator overloading.

Introduction

This lecture introduces operator overloading as a compile-time polymorphism feature in C++. It enables built-in operators such as + and - to work with user-defined objects in a meaningful and readable way.

Lecture Slides

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Theory Explanation

Operator overloading allows an existing C++ operator to be redefined for class objects. This makes programs more natural to write and easier to understand. For example, if c1 and c2 are complex numbers, writing c1 + c2 is clearer than calling a separate function such as add(c1, c2).

Important: Operator overloading does not create new operators and does not change precedence or associativity.

Example Program

complex_operator_overloading.cpp

#include <iostream>
using namespace std;

class Complex {
private:
    int real;
    int imag;

public:
    Complex(int r = 0, int i = 0) {
        real = r;
        imag = i;
    }

    Complex operator+(const Complex& c) const {
        return Complex(real + c.real, imag + c.imag);
    }

    void display() const {
        cout << real << " + " << imag << "i";
    }
};

int main() {
    Complex c1(2, 3), c2(4, 5);
    Complex c3 = c1 + c2;

    cout << "Sum = ";
    c3.display();

    return 0;
}

Run Code

Explanation of the Program

• The class Complex stores the real and imaginary parts.
• The + operator is overloaded as a member function.
• The expression c1 + c2 returns a new object of type Complex.
• The program demonstrates binary operator overloading clearly and compactly.

Key Points to Remember

• Operator overloading is compile-time polymorphism.
• Not all operators can be overloaded.
• Overloaded operators should preserve intuitive meaning.
• Complex numbers are a classic example for teaching binary operator overloading.

Viva Questions

1. What is operator overloading in C++?
2. Why is it called compile-time polymorphism?
3. What is the difference between unary and binary operators?
4. Can all operators be overloaded? Give examples.
5. Why is the Complex class suitable for operator overloading?

Practice / Assignment Questions

Question Type	Question
Short Answer	Define operator overloading and write its general syntax.
Long Answer	Design and implement a class to overload a binary operator and justify its design.
Programming Task	Write a C++ program to overload the - operator for a Complex class.

References

• E. Balagurusamy, Object Oriented Programming with C++.
• Herbert Schildt, C++: The Complete Reference.
• Bjarne Stroustrup, The C++ Programming Language.

Students are encouraged to read the lecture notes, review the slides, execute the sample code, and answer the viva and assignment questions for effective understanding.