What is the difference between virtual and pure virtual functions?

What is the difference between virtual and pure virtual functions in C++?

In C++, a virtual function is a function in a base class that you expect to override in derived classes. A pure virtual function, on the other hand, is a virtual function that has no implementation in the base class and must be overridden in derived classes.

Can you give me an example of each?

Sure! A virtual function might look like this:

class Base {
public:
    virtual void show() { cout << "Base class show"; }
};

A pure virtual function would be defined like this:

class Base {
public:
    virtual void show() = 0; // Pure virtual function
};

What happens if a derived class doesn't implement a pure virtual function?

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

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

You would use a pure virtual function when you want to enforce that derived classes must provide an implementation, ensuring a consistent interface.