Inheritance

Inheritance means a class acquires properties and behaviors of another class. The child class reuses code from the parent class.

Think of it like a child inheriting traits from parents — you get the base features, and can add your own on top.

Syntax

class Parent {
    // base class
};

class Child : public Parent {
    // derived class
};

Simple Example

class Animal {
public:
    string name;
    void eat() { cout << "Animal is eating" << endl; }
};

class Dog : public Animal { // Dog inherits Animal
public:
    void bark() { cout << "Dog is barking" << endl; }
};

int main() {
    Dog d;
    d.eat();  // inherited from Animal
    d.bark(); // Dog's own method
}

Types of Inheritance in C++

1. Single

class A {};
class B : public A {};

2. Multilevel

class A {};
class B : public A {};
class C : public B {}; // C inherits B which inherits A

3. Multiple

class A {};
class B {};
class C : public A, public B {}; // C inherits both A and B

4. Hierarchical

class A {};
class B : public A {};
class C : public A {}; // both B and C inherit A

5. Hybrid

// combination of multiple + hierarchical
class A {};
class B : public A {};
class C : public A {};
class D : public B, public C {}; // Diamond problem

Access Specifiers in Inheritance

Inheritance Type	Public member becomes	Protected member becomes
public	public	protected
protected	protected	protected
private	private	private

Most commonly used is public inheritance in interviews.

Diamond Problem — Virtual Inheritance

class A { public: void show() { cout << "A" << endl; } };
class B : public A {};
class C : public A {};
class D : public B, public C {}; // ERROR! ambiguity

// Fix: Virtual Inheritance
class B : virtual public A {};
class C : virtual public A {};
class D : public B, public C {}; // only one copy of A

C++ Specific Points

Feature	Detail
Default inheritance	private
Most used	public inheritance
Diamond fix	virtual inheritance
Constructor order	Parent constructor called first
Destructor order	Child destructor called first

One-liner: "Inheritance allows a derived class to reuse, extend, and modify the behavior of a base class, promoting code reusability."