Virtual function in java

Sometimes implementation of all functions cannot be provided in a base class because we don’t know the implementation.

Friend function in c++

Such a class is called an abstract class.For example, let Shape be a base class. We cannot provide the implementation of function draw() in Shape, but we know every derived class must have an implementation of draw().

Similarly, an Animal class doesn’t have the implementation of move() (assuming that all animals move), but all animals must know how to move. We cannot create objects of abstract classes.

A pure virtual function (or abstract function) in C++ is a virtual function for which we can have an implementation, But we must override that function in the derived class, otherwise, the derived class will also become an abstract class.

A pure virtual function is declared by assigning 0 in the declaration.

Example of Pure Virtual Functions

Complete Example

A pure virtual function is implemented by classes that are derived from an Abstract class.

Some Interesting Facts

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