In object-oriented programming, inheritance allows us to create new classes that inherit the properties and behaviors of existing classes. This feature enables us to extend functionality, modify existing behavior, or encapsulate new features without altering the original code.

Base Class Definition

Let's start with a basic base class named Base:

#include <iostream>

class Base {
protected:
    int m_value;

public:
    Base(int value) : m_value(value) {}

    void identify() const {
        std::cout << "I am a Base\n";
    }
};

Here, Base has a protected member m_value and a member function identify().

Derived Class Inheritance

Next, we create a derived class called Derived that inherits from the Base class. The derived class introduces its own constructor and a new member function, getValue():

class Derived : public Base {
public:
    Derived(int value) : Base(value) {}

    int getValue() const {
        return m_value;
    }
};

In this example, Derived extends the functionality of Base without modifying its directly.

Adding New Functionality

The key concept here is adding new functionality to the derived class. For instance, we have introduced a method getValue() in Derived to retrieve the value of m_value.

int getValue() const {
    return m_value;
}

Usage of Derived Class

Now, let's see how we can utilize the derived class:

int main() {
    Derived derived{5};
    std::cout << "derived has value " << derived.getValue() << '\n';

    return 0;
}

In this example, we create an object of type Derived, initialize it with a value of 5, and then use the getValue() method to retrieve and print the value.