Write a C++ Program to Use Constructors and Destructors in a Class

Write a Program to Use Constructors and Destructors in a Class

In C++, constructors and destructors are special member functions used to manage the lifecycle of an object — from its creation to its destruction. Understanding how they work is a key part of mastering object-oriented programming (OOP) in C++.

🔹 What is a Constructor?

A constructor is a special function that is automatically called when an object is created. Its main purpose is to initialize object data members.

Characteristics:

• Has the same name as the class.
• No return type (not even `void`).
• Can be overloaded (i.e., multiple constructors with different parameters).

🔹 What is a Destructor?

A destructor is a special function that is automatically called when an object goes out of scope or is deleted. Its main purpose is to perform clean-up tasks like releasing memory or closing files.

Characteristics:

• Same name as the class, preceded by a tilde (`~`).
• Cannot be overloaded.
• No parameters and no return type.

✅ C++ Program Using Constructor and Destructor

#include <iostream>

using namespace std;

class Student {

private:

    string name;

    int rollNo;

public:

    // Constructor

    Student() {

        cout << "Constructor called: Object created!" << endl;

        name = "Not Assigned";

        rollNo = 0;

    }

    // Parameterized Constructor

    Student(string n, int r) {

        name = n;

        rollNo = r;

        cout << "Parameterized Constructor called!" << endl;

    }

    // Display function

    void display() {

        cout << "Name: " << name << ", Roll No: " << rollNo << endl;

    }

    // Destructor

    ~Student() {

        cout << "Destructor called: Object destroyed!" << endl;

    }

};

int main() {

    cout << "Creating student1 using default constructor...\n";

    Student student1;

    student1.display();

    cout << "\nCreating student2 using parameterized constructor...\n";

    Student student2("Vivek Bhardwaj", 101);

    student2.display();

    cout << "\nEnd of main function.\n";

    return 0;

}

🔍 Output Explanation

Creating student1 using default constructor...

Constructor called: Object created!

Name: Not Assigned, Roll No: 0

Creating student2 using parameterized constructor...

Parameterized Constructor called!

Name: Vivek Bhardwaj, Roll No: 101

End of main function.

Destructor called: Object destroyed!

Destructor called: Object destroyed!

• student1 is created using the default constructor.
• student2 is created using the parameterized constructor.
• Both objects are destroyed at the end of the program, triggering the destructor.

✅ Conclusion

Constructors and destructors automate the process of initialization and cleanup in object-oriented programming. They help manage memory and resources efficiently without manual intervention.

• Use constructors to ensure that objects are always created with valid initial states.
• Use destructors to free resources, especially when dealing with file handling, dynamic memory, or complex objects.