Abstract Base Class (ABC)

Classes that act as base classes and not meant to be instantiated are called abstract base classes.
Properties possessed by abstract base class(ABC) are:
•    An ABC should contain at least one pure virtual function.
•    An ABC has no instances (objects).
•    An ABC should omit implementations except for the destructor and functions that provide access to private data members. That means, virtual functions in an abstract base class usually should be pure.
•     An ABC is used only as the basis for derived classes and thus defines a minimum interface for its descendants.

Example of an ABC is:

class ABC
{
public:
virtual void purevirtualfunction() = 0;
};

Above is an abstract base class. This class is inherited by the other classes, like

class hello : public ABC
{
public:
void purevirtualfunction()
{
……………
//methods and variables
……………
}
};