#include <iostream>

#include <string>

using namespace std;

/*

* CONSTRUCTORS - BASICS

* =====================

* A constructor is a special member function that:

* 1. Has the SAME NAME as the class

* 2. NO RETURN TYPE (not even void)

* 3. Automatically called when an object is created

* 4. Used to INITIALIZE objects

*

* INTERVIEW QUESTION: What is a constructor?

* ANSWER: A constructor is a special member function with the same name as the

* class, has no return type, and is automatically invoked when an object is created.

* Its primary purpose is to initialize the object's data members.

*/

class Student {

private:

string name;

int age;

int rollNumber;

public:

// DEFAULT CONSTRUCTOR (No parameters)

// If you don't write any constructor, compiler provides a default one

Student() {

cout << "Default Constructor Called!" << endl;

name = "Unknown";

age = 0;

rollNumber = 0;

}

// Display function

void display() {

cout << "Name: " << name << ", Age: " << age << ", Roll: " << rollNumber << endl;

}

};

// Example without explicit constructor

class Box {

private:

int length;

int width;

public:

// NO CONSTRUCTOR DEFINED

// Compiler will provide a default constructor that does nothing

void setDimensions(int l, int w) {

length = l;

width = w;

}

void display() {

cout << "Length: " << length << ", Width: " << width << endl;

}

};

int main() {

cout << "=== BASIC CONSTRUCTOR DEMO ===" << endl;

cout << endl;

// Creating object - Constructor is called automatically

cout << "Creating Student object s1:" << endl;

Student s1;

s1.display();

cout << "\n=== WITHOUT EXPLICIT CONSTRUCTOR ===" << endl;

Box b1; // Compiler-provided default constructor called (does nothing)

// length and width have garbage values

cout << "Box b1 before initialization: ";

b1.display(); // Uncommenting this will show garbage values

b1.setDimensions(10, 20);

cout << "Box b1 after initialization: ";

b1.display();

cout << "\n=== KEY TAKEAWAYS ===" << endl;

cout << "1. Constructor has same name as class" << endl;

cout << "2. No return type (not even void)" << endl;

cout << "3. Called automatically when object is created" << endl;

cout << "4. If not defined, compiler provides default constructor" << endl;

cout << "5. Used to initialize object's data members" << endl;

return 0;

}

/*

* INTERVIEW QUESTIONS:

*

* Q1: What happens if you don't define a constructor?

* A1: The compiler automatically provides a default constructor that does nothing.

*

* Q2: Can a constructor have a return type?

* A2: No, constructors cannot have a return type, not even void.

*

* Q3: When is a constructor called?

* A3: A constructor is called automatically when an object of the class is created.

*

* Q4: How many constructors can a class have?

* A4: A class can have multiple constructors (constructor overloading).

*

* Q5: Can constructors be private?

* A5: Yes, private constructors are used in Singleton pattern and factory methods.

*/