Question

What base class is named in the line below? class Pet : public Dog

Short answer

Answer: The base class in the given line of code is 'Dog'.

Step-by-step solution

Identify the Class Definition Syntax.

Here's the given line of code: ``` class Pet : public Dog ``` This line signifies that we are defining a new class 'Pet' and specifying that it must inherit from another class.

Locate the Base Class.

Inherited class is always mentioned after the colon (:) in the class definition. In this case, the class right after the colon is 'Dog,' with the 'public' keyword indicating the access level for the inherited members from the base class.

State the Base Class.

The base class named in the given line of code is 'Dog.' This means that the 'Pet' class publicly inherits all members (attributes and methods) from the 'Dog' class.

Key concepts

Base Class

In C++, the concept of a "base class" is fundamental to understanding inheritance. Essentially, a base class is the class from which other classes derive or inherit properties and behaviors. This means that when a class inherits another class, the originally inherited class is referred to as the base class.

Base classes are utilized to create a hierarchical relationship between classes, where derived classes build upon and extend the functionality of base classes. For example, in the original exercise, the base class is "Dog," from which the "Pet" class inherits properties. This allows "Pet" to use any member functions or attributes (that are accessible) of the class "Dog." Collectively, this has the following benefits:

• Code Reusability - Once a base class is created, its features can be reused by any of its derived classes without rewriting the code.
• Maintainability - Updating the base class automatically updates its features for all derived classes.
• Organized Hierarchy - Base classes help in creating structured and logical class hierarchies.

Class Definition Syntax

In C++, understanding the class definition syntax is key to utilizing inheritance effectively. A typical class definition in this context will involve several elements:

The keyword `class` is used to define a class followed by the class name, like `class Pet`. If this class inherits another, a colon (`:`) follows the class name along with the type of inheritance (`public`, `protected`, or `private`) and the base class name. Thus, the syntax `class Pet : public Dog` provides a clear definition:

• **`class Pet`** - Begins the definition of the new class named Pet.
• **`:`** - Signifies inheritance in the class syntax.
• **`public Dog`** - Specifies the inheritance type (`public`) and the base class (`Dog`), meaning "Pet" will inherit publicly from "Dog."

The placement of the inheritance type and the base class name right after the colon is crucial in class definitions, as it determines both the hierarchy and access levels for inherited members.

Access Levels

Access levels in C++ inheritance define how the members (both data and functions) of a base class are accessible to derived classes and outside users. There are three main access specifiers: `public`, `protected`, and `private`. These determine the visibility and usage permissions for members of the base class when inherited.

• **Public Inheritance** - This is the most common form of inheritance. When a class inherits publicly, all `public` members of the base class remain `public` in the derived class, and all `protected` members remain `protected.` This is what we see in the example "public Dog," where "Pet" gets the `public` and `protected` members of "Dog."
• **Protected Inheritance** - Here, both `public` and `protected` members of the base class become `protected` in the derived class. This limits the exposure of these members to outside classes but allows derived classes to access them.
• **Private Inheritance** - In this case, both `public` and `protected` members turn `private` within the derived class. This form is less commonly used but can be useful when a class needs to use another class's implementation without exposing its interface.

Understanding these access levels helps in effectively implementing class hierarchies that are secure and maintain the integrity of encapsulation within C++ programs.