Explain polymorphism and compare compile time and run time polymorphism. Describe virtual and pure virtual function with an example.

 Polymorphism is the concept of object-oriented programming that allows a function to take on many different forms, depending on the context in which it is called. In C++, polymorphism can be achieved through function overloading and function overriding.

Compile-time polymorphism, also known as static polymorphism, occurs when the compiler determines which function to call based on the types of the arguments provided. This is achieved through function overloading, where multiple functions have the same name but different parameters.

Run-time polymorphism, also known as dynamic polymorphism, occurs when the compiler cannot determine which function to call until the program is actually running. This is achieved through function overriding, where a derived class provides a new implementation for a function defined in its base class.

In C++, virtual functions enable run-time polymorphism. When a function is declared as virtual in the base class, the derived class can override the function to provide its own implementation. This allows the program to determine which function to call based on the actual type of the object, rather than the declared type of the pointer or reference.

Pure virtual functions are virtual functions that do not have an implementation in the base class. They must be overridden in the derived classes, and any class with a pure virtual function is an abstract class and cannot be instantiated. This allows for the creation of a common interface for a set of related classes.

#include <iostream>

using namespace std;

// Base class

class Shape {

    public:

        virtual float area() = 0; // Pure virtual function

        virtual void display() { cout << "Shape" << endl; }// virtual function

};

// Derived classes

class Rectangle : public Shape {

    float width, height;

    public:

        Rectangle(float w, float h) { width = w; height = h; }

        float area() { return width * height; }

        void display() { cout << "Rectangle" << endl; }

};

class Circle : public Shape {

    float radius;

    public:

        Circle(float r) { radius = r; }

        float area() { return 3.14 * radius * radius; }

        void display() { cout << "Circle" << endl; }

};

int main() {

    Shape *s;

    Rectangle rect(5, 10);

    Circle circ(7);

    

    s = &rect;

    s->display();

    cout << "Area: " << s->area() << endl;

    

    s = &circ;

    s->display();

    cout << "Area: " << s->area() << endl;

    

    return 0;

}