Describe how a pure virtual function (the prototype) is written.

What will be an ideal response?

The prototype for a pure virtual function is written by making use of an assigned zero, like this:
```
class Base
{
public:
virtual return_type FunctionName() = 0;
// the = 0; means virtual
};

Such as:
class Animal
{
public:
virtual float HowMuchDoIWeigh() = 0;
// the = 0; means virtual
};
```