Don't Repeat Yourself (DRY)

Inheritance allows you to create a new class (the Child or Derived class) that inherits all the properties and functions of an existing class (the Parent or Base class).

The Logic of Inheritance

Think of a Vehicle class. It has a brand and a start() function. A Car is a type of Vehicle. So instead of rewriting the brand and start() code for Car, Truck, and Motorcycle, we just inherit from Vehicle!

Syntax

class Car : public Vehicle {
    // Car inherits everything from Vehicle
};

Types of Inheritance

1. Single: One parent, one child.
2. Multilevel: Grandparent -> Parent -> Child.
3. Multiple: One child can have TWO parents. (Unique to C++).
4. Hierarchical: One parent, many children.

The protected Keyword

A child can see its parent's public and protected members, but never the private ones. Private means "Private to THIS class only."

Function Overriding

A child can provide its own "special" version of a parent's function.

class Animal { public: void speak() { cout << "Sound"; } };
class Dog : public Animal { public: void speak() { cout << "Woof!"; } };

Multiple inheritance is powerful but dangerous. It can lead to the "Diamond Problem" where a child doesn't know which version of a function to use. C++ solves this using Virtual Inheritance.