What is a pure virtual function in C++?

Can you explain what a pure virtual function is in C++?

A pure virtual function is a function declared in a base class that has no implementation. It's defined by assigning 0 in its declaration.

Why would I use a pure virtual function instead of a regular virtual function?

Using a pure virtual function makes the class abstract, meaning it cannot be instantiated. This enforces that derived classes must implement the function.

Can you give me an example of a pure virtual function?

Sure! Here's a simple example:

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

class Circle : public Shape {
public:
    void draw() override {
        // Implementation for drawing a circle
    }
};

What happens if a derived class does not implement the pure virtual function?

If a derived class does not implement the pure virtual function, it also becomes an abstract class and cannot be instantiated.