Describe the differences between class inheritance and interface inheritance in C++. Provide examples to illustrate their usage and benefits.

In C++, there are two types of inheritance: class inheritance and interface inheritance. Both inheritance mechanisms allow for code reuse and the creation of hierarchical relationships between classes. However, they differ in their purpose, implementation, and the nature of the relationship between classes. Let's explore the differences between class inheritance and interface inheritance in C++.

Class Inheritance:
Class inheritance, also known as implementation inheritance or implementation inheritance, allows a derived class to inherit the properties (data members and member functions) of a base class. The derived class can extend or modify the inherited properties, providing a mechanism for code reuse and specialization.

In class inheritance, the derived class inherits the members of the base class using the `public`, `protected`, or `private` access specifiers. The access specifiers determine the visibility of the inherited members in the derived class.

Here's an example that demonstrates class inheritance:

```
cpp`class Animal {
public:
void eat() {
cout << "Animal is eating." << endl;
}
};

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

int main() {
Dog dog;
dog.eat(); // Accessing the inherited member
dog.bark();

return 0;
}`
```
In this example, the `Dog` class inherits the `eat()` member function from the `Animal` class. The `Dog` class can use the `eat()` function as if it was defined within itself. Class inheritance allows for code reuse and enables the creation of class hierarchies based on the "is-a" relationship.

Interface Inheritance:
Interface inheritance, also known as pure virtual inheritance or pure virtual functions, focuses on defining an abstract interface that derived classes must implement. It allows a class to inherit only the function signatures (declarations) from a base class without inheriting their implementation.

In interface inheritance, the base class declares one or more pure virtual functions using the syntax `virtual ReturnType FunctionName() = 0;`. A class that inherits this interface must provide implementations for all the pure virtual functions.

Here's an example that illustrates interface inheritance:

```
cpp`class Drawable {
public:
virtual void draw() = 0; // Pure virtual function
};

class Circle : public Drawable {
public:
void draw() override {
cout << "Drawing a circle." << endl;
}
};

class Square : public Drawable {
public:
void draw() override {
cout << "Drawing a square." << endl;
}
};

int main() {
Circle circle;
Square square;

circle.draw();
square.draw();

return 0;
}`
```
In this example, the `Drawable` class defines an interface by declaring a pure virtual function `draw()`. The `Circle` and `Square` classes inherit from the `Drawable` class and provide their own implementations for the `draw()` function. Interface inheritance allows for polymorphism, as objects of different derived classes can be treated uniformly based on their common interface.

Benefits of Class Inheritance:

* Code Reusability: Class inheritance allows derived classes to inherit the properties and behavior of a base class, promoting code reuse and avoiding duplication.
* Code Organization: Class inheritance facilitates the organization of related classes into a hierarchy based on the "is-a" relationship, making the code structure more intuitive and maintainable.
* Polymorphism: Class inheritance enables polymorphism, allowing objects of derived classes to be treated as objects of the base class. This provides flexibility and extensibility in code design.

Benefits of Interface Inheritance:

* Abstraction: Interface inheritance focuses on defining abstract interfaces that specify the contract for derived classes. It allows for the separation of interface