Default constructor in C++ - Mini Project: Build & Apply

Default Constructor in C++

📖 Scenario: Imagine you are creating a simple program to represent a book in a library. Each book has a title and a number of pages. You want to create a class to hold this information and learn how to use a default constructor to set initial values.

🎯 Goal: Build a C++ class called Book with a default constructor that sets the title to "Unknown" and pages to 0. Then create an object of this class and print its details.

📋 What You'll Learn

Create a class named Book

Add two member variables: title (string) and pages (int)

Write a default constructor that sets title to "Unknown" and pages to 0

Create an object of Book using the default constructor

Print the title and pages of the object

💡 Why This Matters

🌍 Real World

Default constructors help create objects with safe starting values, useful in many programs like managing library books or user profiles.

💼 Career

Understanding constructors is essential for C++ programming jobs, especially in software development and systems programming.

1

Create the Book class with member variables

Write a class called Book with two public member variables: title of type std::string and pages of type int.

C++

#include 
#include 

// Define class Book with public members title and pages
// Your code here

Need a hint?

Use class Book { public: std::string title; int pages; }; to define the class.

2

Add a default constructor to Book

Inside the Book class, add a default constructor named Book() that sets title to "Unknown" and pages to 0.

C++

#include 
#include 

class Book {
public:
    std::string title;
    int pages;

    // Add default constructor here
    // Your code here
};

Need a hint?

Write a constructor like Book() { title = "Unknown"; pages = 0; }.

3

Create a Book object using the default constructor

In the main() function, create an object named myBook of type Book using the default constructor.

C++

#include 
#include 

class Book {
public:
    std::string title;
    int pages;

    Book() {
        title = "Unknown";
        pages = 0;
    }
};

int main() {
    // Create Book object myBook
    // Your code here
    return 0;
}

Need a hint?

Write Book myBook; inside main().

4

Print the title and pages of myBook

Add code in main() to print the title and pages of the myBook object. Use std::cout to print exactly: Title: Unknown and Pages: 0 on separate lines.

C++

#include 
#include 

class Book {
public:
    std::string title;
    int pages;

    Book() {
        title = "Unknown";
        pages = 0;
    }
};

int main() {
    Book myBook;
    // Print title and pages of myBook
    // Your code here
    return 0;
}

Need a hint?

Use std::cout << "Title: " << myBook.title << std::endl; and similarly for pages.