<div class="image-550">
<img src="https://cdn.kahimyang.com/resources-24/open-close-3.avif" alt="Open-Closed Principle in C++" loading="lazy" />
</div>
<h4>
Understanding the Open-Closed Principle
</h4>
<p>
The key idea behind OCP is to design your system in such a way that you can introduce new features or requirements by adding new code rather than modifying existing code. This promotes code reusability and maintainability.
</p>
<h4>
Example Scenario
</h4>
<p>
Let's consider a scenario where we have a simple system to calculate the area of different shapes. Initially, we have two shapes: Rectangle and Circle.
</p>
<h4>
Initial Design
</h4>
<p>
Rectangle.h:
</p>

<pre style="font-size: 90%;">
<code class="language-cpp normalize-whitespace line-numbers" >
#pragma once

class Rectangle {
public:
    Rectangle(double width, double height) : 
                 width(width), height(height) {}
    double area() const { return width * height; }
private:
    double width;
    double height;
};
</code>
</pre>

<p>
Circle.h:
</p>

<pre style="font-size: 90%;">
<code class="language-cpp normalize-whitespace line-numbers" >
#pragma once

class Circle {
public:
    Circle(double radius) : radius(radius) {}
    double area() const 
       { return 3.14159 * radius * radius; }
private:
    double radius;
};
</code>
</pre>
<p>
Main.cpp:
</p>
<pre style="font-size: 90%;">
<code class="language-cpp normalize-whitespace line-numbers" >
#include &lt;iostream>
#include "Rectangle.h"
#include "Circle.h"

int main() {
    Rectangle rectangle(5.0, 3.0);
    Circle circle(2.0);

    std::cout &lt;&lt; "Rectangle area: " &lt;&lt; 
                   rectangle.area() &lt;&lt; std::endl;
    std::cout &lt;&lt; "Circle area: " &lt;&lt; 
                   circle.area() &lt;&lt; std::endl;

    return 0;
}
</code>
</pre>


Implementing the Open-Closed Principle in C++: A Detailed Guide