virtual base class in c++ - Wikitechy

Syntax for Pure Virtual Function is ?

Editor — Mon, 12 Jul 2021 22:58:10 +0000

Syntax for Pure Virtual Function is ?

A. virtual void show()==0

B. void virtual show()==0

C. virtual void show()=0

D. void virtual show()=0

Answer : B. virtual void show()==0

Explanation :

In C++, A pure virtual function or abstract function is a virtual function for which we don’t have implementation, we only declare it. A pure virtual function is declared by assigning 0 in declaration.

Syntax

// An abstract class 
class Sample
{    
    // Data members of class 
public: 
    // Pure Virtual Function 
    virtual void show() = 0; 
    
   /* Other members */
};

Find the wrong statement about Abstract Class ?

Editor — Mon, 12 Jul 2021 22:54:00 +0000

Find the wrong statement about Abstract Class ?

A. We can’t create its objects

B. We can’t create pointers to an abstract class

C. It contains at least one pure virtual function

D. We can create references to an abstract class

Answer : B. We can’t create pointers to an abstract class

Explanation :

Abstract Class is a class which contains atleast one Pure Virtual function.
An abstract class is a class that is designed to be specifically used as a base class.
It is used to provide an Interface for its sub classes.
Classes inheriting an Abstract Class must provide definition to the pure virtual function, otherwise they will also become abstract class.
You declare a pure virtual function by using a pure specifier (= 0) in the declaration of a virtual member function in the class declaration.

Example

class AB {
public:
  virtual void f() = 0;
};

Which of the following statements about virtual base classes is correct ?

Editor — Mon, 12 Jul 2021 22:41:41 +0000

Which of the following statements about virtual base classes is correct ?

A. It is used to provide multiple inheritance .

B. It is used to avoid multiple copies of base class in derived class .

C. It is used to allow multiple copies of base class in a derived class.

D. It allows private members of the base class to be inherited in the derived class.

Answer : B. It is used to avoid multiple copies of base class in derived class .

Explanation

When two or more objects are derived from a common base class, we can prevent multiple copies of the base class being present in an object derived from those objects by declaring the base class as virtual when it is being inherited such a base class is known as virtual base class.
Virtual base classes, used in virtual inheritance, is a way of preventing multiple “instances” of a given class appearing in an inheritance hierarchy when using multiple inheritance.