FAQs on C++ Programming Tutorials - Abstract Classes and Pure virtual Functions

Question 1

1. What is an abstract class in C++?

Accepted Answer

Ans. An abstract class in C++ is a class that cannot be instantiated. It is designed to serve as a base for derived classes and contains at least one pure virtual function. Abstract classes provide a way to define common attributes and behavior that can be inherited by their derived classes.

Question 2

2. What is a pure virtual function in C++?

Accepted Answer

Ans. A pure virtual function in C++ is a virtual function that is declared in a base class but has no implementation in that class. It is denoted by adding ' = 0' at the end of the function declaration. Derived classes must override the pure virtual function and provide their own implementation. Pure virtual functions make a class abstract.

Question 3

3. How to declare an abstract class in C++?

Accepted Answer

Ans. To declare an abstract class in C++, we need to define at least one pure virtual function in the class. We can do this by adding ' = 0' at the end of the function declaration. It is also recommended to provide a virtual destructor in the abstract class to ensure proper cleanup of derived objects.

Question 4

4. Can we instantiate an abstract class in C++?

Accepted Answer

Ans. No, we cannot instantiate an abstract class in C++. Since an abstract class contains at least one pure virtual function, it is incomplete and cannot be used to create objects. However, we can create pointers and references to abstract classes, which can be used to point to objects of derived classes.

Question 5

5. Why do we need abstract classes and pure virtual functions in C++?

Accepted Answer

Ans. Abstract classes and pure virtual functions in C++ provide a way to achieve abstraction and polymorphism. They allow us to define a common interface and behavior in a base class and let the derived classes provide their own specific implementations. This helps in code reusability and allows for easier maintenance and extension of the codebase. Additionally, abstract classes and pure virtual functions are key components of the object-oriented programming paradigm.

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