🟣 OOP · Lesson 39

Constructors in C++

What is Constructors in C++?

Constructors in C++
A constructor is a special member function that initializes an object automatically when it is created. It has the same name as the class and no return type.

Level
🟣 Object-Oriented Programming

Example File
constructors.cpp

Main Focus
Concept + syntax + practical C++ program

Why should you learn this?

It helps you write correct and readable C++ programs.
It is used repeatedly in school practicals, projects and competitive programming.
It builds the base for advanced topics such as OOP, STL and data structures.

Important Terms

Term	Meaning / Use
constructor	Constructors in C++ programming में Constructor use होता है।
default constructor	Constructors in C++ programming में Default constructor use होता है।
parameterized constructor	Constructors in C++ programming में Parameterized constructor use होता है।
initialization	Constructors in C++ programming में Initialization use होता है।

Syntax / Pattern

C++

ClassName(parameters) { initialization; }

Example Program

main.cpp

#include <iostream>
using namespace std;
class Student{
    int roll;
public:
    Student(int r){ roll = r; }
    void show(){ cout << roll; }
};
int main(){
    Student s(12);
    s.show();
    return 0;
}

Expected Output

Program Explanation

Student(int r) runs automatically when s is created.
roll is initialized with 12.

Exam Tip: In C++ practical answers, write the logic first, then the program, then expected output. For theory, always include one suitable example.

Where will you use it?

initializing records
setting default values
resource setup

Common Mistakes

Writing return type for constructor.
Forgetting to initialize all data members.

Practice Tasks

Create constructor for Employee.
Write default and parameterized constructor.

Summary

Constructors in C++ एक ज़रूरी C++ topic है। परिभाषा सीखें, syntax समझें, example program चलाएं और फिर practice tasks हल करके concept मज़बूत करें।