Why inheritance is used in C++ - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of Inheritance in C++

Why do programmers use inheritance in C++?

A To reuse code from existing classes and create a hierarchy of related classes

B To make programs run faster by avoiding function calls

C To store data in a file for later use

D To prevent any changes to the base class

💡 Hint

Think about how you can build new things based on old things without rewriting everything.

Inheritance allows a new class to use properties and methods of an existing class, promoting code reuse and logical organization.

❓ Predict Output

intermediate

Output of Inheritance Example

What is the output of this C++ code using inheritance?

C++

#include <iostream>
class Animal {
public:
    void speak() { std::cout << "Animal speaks" << std::endl; }
};

class Dog : public Animal {
public:
    void speak() { std::cout << "Dog barks" << std::endl; }
};

int main() {
    Dog d;
    d.speak();
    return 0;
}

A Animal speaks

B Compilation error due to speak() redefinition

C No output

D Dog barks

💡 Hint

Which speak() method is called when using a Dog object?

The Dog class overrides the speak() method, so calling speak() on a Dog object prints "Dog barks".

🔧 Debug

advanced

Identify the Inheritance Error

What error does this C++ code produce?

C++

#include <iostream>
class Base {
public:
    void show() { std::cout << "Base" << std::endl; }
};

class Derived : Base {
};

int main() {
    Derived d;
    d.show();
    return 0;
}

A Compilation error: 'show' is inaccessible due to private inheritance

B Runtime error: segmentation fault

C No error, output is 'Derived'

D Compilation error: missing semicolon after class definition

💡 Hint

Check the default inheritance access level in C++ classes.

In C++, class inheritance is private by default, so Base's public members become private in Derived, making show() inaccessible.

📝 Syntax

advanced

Correct Syntax for Public Inheritance

Which option shows the correct syntax for public inheritance in C++?

A class Derived extends Base {};

B class Derived inherits Base {};

C class Derived : public Base {};

D class Derived < Base {};

💡 Hint

Remember the keyword used in C++ for inheritance.

C++ uses a colon and the keyword 'public' to specify public inheritance.

🚀 Application

expert

Number of Accessible Members in Derived Class

Given the following code, how many members are accessible directly from an object of class Derived?

class Base {
public:
    int a;
protected:
    int b;
private:
    int c;
};

class Derived : public Base {
public:
    void func() {
        a = 1;
        b = 2;
        // c = 3; // Is this accessible?
    }
};

int main() {
    Derived d;
    d.a = 5;
    // d.b = 6; // Is this accessible?
    // d.c = 7; // Is this accessible?
    return 0;
}

A No members are accessible directly from Derived objects

B Only 1 member (a) is accessible directly from Derived objects

C All 3 members (a, b, and c) are accessible directly from Derived objects

D 2 members (a and b) are accessible directly from Derived objects

💡 Hint

Consider the access levels and where they apply.

Public members are accessible from outside. Protected members are accessible inside Derived but not from outside objects. Private members are not accessible at all.