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Concrete Class & Abstract Class

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In C++, a concrete class is a class that can be instantiated to create objects, while an abstract class cannot be instantiated and typically contains at least one pure virtual function. Here's a simple C++ program to illustrate the difference between a concrete class and an abstract class:


#include <iostream>

using namespace std;

// Abstract Class

class AbstractClass {

public:

    // Pure virtual function

    virtual void display() = 0;


    // Concrete method

    void show() {

        cout << "This is a concrete method in an abstract class." << endl;

    }

};

// Concrete Class

class ConcreteClass : public AbstractClass {

public:

    // Implementation of the pure virtual function

    void display() override {

        cout << "This is the implementation of the pure virtual function in a concrete class." << endl;

    }

};

int main() {

    // AbstractClass obj; // This will cause a compilation error

    ConcreteClass obj; // Instantiating the concrete class

    obj.display(); // Calling the implemented method

    obj.show(); // Calling the concrete method from the abstract class

    return 0;

}


Explanation:


- Abstract Class:

  - Defined using the keyword `class`.

  - Contains a pure virtual function: `virtual void display() = 0;`.

  - Cannot be instantiated directly.


- Concrete Class:

  - Inherits from the abstract class: `class ConcreteClass : public AbstractClass`.

  - Implements the pure virtual function: `void display() override`.

  - Can be instantiated to create objects.


In the `main()` function, attempting to instantiate `AbstractClass` will result in a compilation error, while instantiating `ConcreteClass` is allowed and we can call both the implemented pure virtual function and the inherited concrete method.


This example illustrates the key differences between concrete and abstract classes in C++. Feel free to experiment with this code and let me know if you have any questions or need further details! 🚀

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