Day 51: Polymorphism in C++ – Types, Examples, and Applications | Class 11, Chapter 5 - BSEB Class 11-12 Computer Science: 100-Day Bilingual Guide with MCQs, Solutions and Questions

Day 51 – Polymorphism in C++

Class 11 Computer Science – Chapter 5

What is Polymorphism? (Polymorphism क्या है?)

Polymorphism in C++ refers to the ability of a function, object, or operator to behave differently based on the context. It is one of the core principles of object-oriented programming.
C++ में Polymorphism का अर्थ है एक फ़ंक्शन, ऑब्जेक्ट, या ऑपरेटर का विभिन्न संदर्भों में अलग-अलग तरीके से व्यवहार करना। यह ऑब्जेक्ट-ओरिएंटेड प्रोग्रामिंग के प्रमुख सिद्धांतों में से एक है।

Types of Polymorphism (Polymorphism के प्रकार)

• Compile-Time Polymorphism (संकलन-समय बहुरूपता): Achieved using function overloading and operator overloading.
• Run-Time Polymorphism (रन-समय बहुरूपता): Achieved using function overriding and virtual functions.

Examples of Polymorphism in C++ (C++ में Polymorphism के उदाहरण)

Example 1: Function Overloading

#include <iostream>
using namespace std;

class Calculator {
public:
    int add(int a, int b) {
        return a + b;
    }
    double add(double a, double b) {
        return a + b;
    }
};

int main() {
    Calculator calc;
    cout << "Integer addition: " << calc.add(3, 4) << endl;
    cout << "Double addition: " << calc.add(2.5, 3.5) << endl;
    return 0;
}

Output:

Integer addition: 7
Double addition: 6

Example 2: Function Overriding

#include <iostream>
using namespace std;

class Base {
public:
    virtual void show() {
        cout << "Base class show()" << endl;
    }
};

class Derived : public Base {
public:
    void show() override {
        cout << "Derived class show()" << endl;
    }
};

int main() {
    Base *ptr;
    Derived obj;
    ptr = &obj;
    ptr->show();
    return 0;
}

Output:

Derived class show()

Practice Questions

Multiple Choice Questions (MCQs)

1. Which of the following is an example of compile-time polymorphism?
   (a) Function Overloading | (b) Virtual Functions | (c) Function Overriding | (d) None
2. What is the purpose of polymorphism?
   (a) Data security | (b) Code reusability | (c) Faster execution | (d) None
3. Which keyword is used to define virtual functions?
   (a) virtual | (b) override | (c) const | (d) None
4. What is function overriding?
   (a) Redefining a base class function in the derived class
   (b) Multiple functions with the same name but different parameters
   (c) Reusing an operator for user-defined types
   (d) None
5. Which type of polymorphism is resolved at runtime?
   (a) Compile-Time | (b) Run-Time | (c) Static | (d) None
6. What is operator overloading in C++?
   (a) Redefining an operator to work with user-defined types
   (b) Using multiple operators on one object
   (c) Using operators in functions
   (d) None
7. What is the output of this code?
   

   class A {
   public:
       virtual void display() {
           cout << "Class A";
       }
   };
   
   class B : public A {
   public:
       void display() override {
           cout << "Class B";
       }
   };
   
   int main() {
       A *ptr;
       B obj;
       ptr = &obj;
       ptr->display();
       return 0;
   }
           

   (a) Class A | (b) Class B | (c) Error | (d) None
8. What is the main advantage of polymorphism in OOP?
   (a) Flexibility | (b) Faster execution | (c) Data hiding | (d) None
9. Which function call is resolved during runtime in polymorphism?
   (a) Overloaded functions | (b) Overridden functions | (c) Both | (d) None
10. Which feature of polymorphism is achieved using function overriding?
    (a) Dynamic Method Dispatch | (b) Compile-Time Execution | (c) Operator Overloading | (d) None

Answers to MCQs:

1: (a), 2: (b), 3: (a), 4: (a), 5: (b), 6: (a), 7: (b), 8: (a), 9: (b), 10: (a)

Short Answer Questions

1. What is polymorphism in C++?
   Answer: Polymorphism allows functions or objects to behave differently based on the context.
2. What is the difference between compile-time and run-time polymorphism?
   Answer: Compile-time polymorphism is resolved during compilation (e.g., function overloading), while run-time polymorphism is resolved during execution (e.g., function overriding).
3. Write a program to demonstrate operator overloading in C++.
   Answer:

   class Complex {
   public:
       int real, imag;
       Complex operator+(Complex obj) {
           Complex temp;
           temp.real = real + obj.real;
           temp.imag = imag + obj.imag;
           return temp;
       }
   };
   

4. What is the role of virtual functions in polymorphism?
   Answer: Virtual functions allow dynamic method resolution, enabling run-time polymorphism.
5. Write an example of function overriding in C++.
   Answer:

   class Base {
   public:
       virtual void display() {
           cout << "Base Class";
       }
   };
   
   class Derived : public Base {
   public:
       void display() override {
           cout << "Derived Class";
       }
   };
   

Long Answer Questions

1. Explain polymorphism in C++ with examples of function overloading and overriding.
2. Write a program to demonstrate virtual functions in C++.
3. Discuss the advantages and disadvantages of polymorphism in object-oriented programming.