Question

Complete the following table by filling in private, protected, public, or inaccessible in the right-hand column: $$\begin{array}{ll} \hline \begin{array}{l} \text { In a public base class, this base class } \\ \text { MEMBER access specification... } \end{array} & \begin{array}{l} \text { .. becomes this access specification } \\ \text { in the derived dass. } \end{array} \\ \hline \text { private } & \\ \text { protected } & \\ \text { public } & \\ \hline \end{array}$$

Short answer

Answer: In a derived class, private members of a public base class become inaccessible, protected members remain protected, and public members stay as public.

Step-by-step solution

Private Members in the Base Class

In a public base class, private members remain private and can only be accessed within the base class itself. They are not accessible by the derived class. Therefore, private members become inaccessible in the derived class.

Protected Members in the Base Class

In a public base class, protected members are inherited by the derived class and will remain protected. These members can be accessed within the derived class and classes derived from it. So, protected members stay protected in the derived class.

Public Members in the Base Class

In a public base class, public members are inherited and also remain public. They can be accessed within the derived class and from any class objects, So, public members keep their status as public in the derived class.

Fill the Table with the Results

Based on the previous steps, the table can be completed as follows: $$\begin{array}{ll} \hline \begin{array}{l} \text { In a public base class, this base class } \\\ \text { MEMBER access specification... } \end{array} & \begin{array}{l} \text { .. becomes this access specification } \\\ \text { in the derived class. } \end{array} \\\ \hline \text { private } & \text { inaccessible } \\\ \text { protected } & \text { protected } \\\ \text { public } & \text { public } \\\ \hline \end{array}$$

Key concepts

Inheritance in C++

Inheritance is a fundamental concept in C++, enabling new classes, known as derived classes, to be built upon existing classes, referred to as base classes. When a class inherits from another, it adopts the members and behaviors of the base class, while also having the capability to introduce its own unique features.

This mechanism not only promotes code reusability but also establishes a relationship where derived classes can be considered specific instances of their base classes, which can then lead to polymorphic behavior. Inheritance in C++ can be of multiple forms, including public, protected, and private inheritance, which dictate how base class members are accessed in the derived classes.

Private Members

Private members of a class are the elements that cannot be accessed outside the class they are declared in, not even by derived classes. They are a crucial aspect of encapsulation, one of the core principles of object-oriented programming.

Encapsulation ensures that the internal data of the object is protected, maintaining a clear boundary between an object's interface and its implementation. In the case of inheritance, private members of a base class remain inaccessible to the derived class. This means that while the derived class is built upon the base class, it cannot directly manipulate or even view the private members it inherits.

Protected Members

Protected members strike a balance between the strict access control of private members and the openness of public members. These members are accessible within their own class and by classes that are derived from it, but they are not available to the rest of the program.

For a derived class, protected members provide the ability to interact with certain attributes or methods inherited from the base class without exposing them to the rest of the program. This level of access is particularly useful in a class hierarchy to permit controlled modification of inherited behavior without breaking the encapsulation.

Public Members

Public members are the most open access level in C++, where members declared as public within a class are accessible everywhere in the program. This includes within the class itself, from any derived classes, and from any other part of the program that has visibility of the class object.

Using public members is advantageous when creating an interface for a class that is meant for wide usage across various components. When a class inherits from a base class with public members, those members retain their public status in the derived class, making them equally accessible through objects of derived classes.