
618 Binding, Polymorphisms, and Virtual Functions
15.7 PURE VIRTUAL FUNCTIONS
In practical applications, the member function of the base class is rarely used for doing any op-
eration; such functions are called do-nothing functions, dummy functions, or pure
virtual functions. The do-nothing functions or pure functions are always virtual functions.
Usually, pure virtual functions are defined with a null body. This is so, because derived classes
should be able to override them. Any normal function cannot be declared as a pure function. After
the declaration of a pure function in a class, the class becomes an abstract class. It cannot be used
to ...