How Does Inheritance Work in C++?

Expected Interview Answer

Step-by-Step Explanation

1. Step 1

   Define the base class

   Write a class containing the members and functions shared by all related types, marking reusable ones public or protected.

2. Step 2

   Derive a class

   Use 'class Derived : public Base' so the derived class inherits the base's public and protected members.

3. Step 3

   Choose the access specifier

   Pick public, protected, or private inheritance to control how inherited members are exposed in the derived class.

4. Step 4

   Add or override behaviour

   Extend the derived class with new members, and override virtual base functions to specialise behaviour.

5. Step 5

   Use base pointers for polymorphism

   Point a Base* at a Derived object and call virtual functions to get runtime dispatch to the derived version.

Code Example

#include <iostream>
#include <string>
using namespace std;

class Animal {
protected:
    string name;
public:
    Animal(const string& n) : name(n) {}
    virtual void speak() const {
        cout << name << " makes a sound\n";
    }
    virtual ~Animal() = default;
};

class Dog : public Animal {
public:
    Dog(const string& n) : Animal(n) {}
    void speak() const override {
        cout << name << " barks\n";
    }
};

int main() {
    Animal* a = new Dog("Rex");
    a->speak();   // Rex barks (runtime polymorphism)
    delete a;
}

Follow-up Questions

• What is the difference between public, protected, and private inheritance?
• What is the diamond problem and how do virtual base classes solve it?
• Are constructors and destructors inherited in C++?
• How does inheritance enable runtime polymorphism?
• When should you prefer composition over inheritance?