Question

A class with at least one pure virtual member function is called a(n) _________ class.

Short answer

A class with at least one pure virtual member function is called an __abstract class__.

Step-by-step solution

Complete the sentence

A class with at least one pure virtual member function is called an abstract class.

Key concepts

Pure Virtual Function

In C++ programming, a pure virtual function is a function declared within a base class that has no implementation whatsoever in that base class. It is declared by assigning `0` as the function's body. Pure virtual functions are essential in situations where you want to ensure that all derived classes implement specific methods.

Here's the syntax to declare a pure virtual function: ```cpp virtual void functionName() = 0; ```

• By marking a function as pure virtual using the `= 0` syntax, it tells the compiler that this function must be overridden by any subclass that inherits from the base class.
• Pure virtual functions enable developers to create a more flexible and extendable program, facilitating the polymorphic behavior of derived classes.

Pure virtual functions are foundational to creating abstract classes, which cannot be instantiated themselves but serve as a base for other classes.

Object-Oriented Programming

Object-oriented programming, often abbreviated as OOP, is a programming paradigm that relies on the concept of "objects". These objects can include data in the form of fields (often known as attributes or properties) and code in the form of procedures (often called methods or functions).

Key features of OOP include:

• Encapsulation: Combining data and functions into a single unit known as an object.
• Inheritance: The mechanism by which a new class can inherit properties and behavior from an existing class.
• Polymorphism: The ability for different classes to be treated as instances of the same class through interfaces. Specifically, the ability of different classes to respond to the same function call.
• Abstraction: Hiding complex reality while exposing only the necessary parts. In OOP, classes can enforce abstraction using abstract classes and pure virtual functions.

C++ is one of the prime languages that support object-oriented programming paradigms, enabling developers to create robust and reusable code.

C++ Programming

C++ is a powerful and popular programming language widely used for various types of software development due to its ability to support low-level manipulation and high-level features provided by object-oriented programming.

• It is an extension of the C programming language, and equally supports procedural programming as well as object-oriented programming principles.
• C++ is known for its performance, as the language gives developers the capability to write fine-tuned command structures. Thus, it is often used in systems programming, game development, and real-time simulation software.

In C++, concepts such as "abstract class" and "pure virtual function" are crucial as they support the creation of dynamic and flexible applications. They help developers design applications where the interface and functionality can be separated, encouraging modularity.

Class Hierarchy

A class hierarchy in object-oriented programming defines the relationship between various classes and how they inherit from one another. This concept allows for systematic and organized classification of various classes, typically defined by the principle of inheritance.

• A simple class hierarchy begins with a base class and can expand into multiple derived classes, which further branch into their respective subclasses.
• At the top of the class hierarchy, we often see abstract classes containing pure virtual functions to enforce rules across derived classes.
• Maintaining a clear class hierarchy helps in implementing the code reusability feature of OOP, where the base class provides a blueprint for derived classes.

For example, in a class hierarchy for animals, a base class "Animal" might have a pure virtual function `makeSound()`, ensuring every derived class like `Dog` or `Cat` implements its own version of `makeSound()`.