What is Protected Inheritance?

The field of computer science uses programming to create solutions to problems. C++ is a programming language used in computer science that utilizes object orientation to model the real world. In object-orientated programming, classes are created to provide a framework for object models that are used during the running of a program. Classes are often created in a structured hierarchy where more generalized parent classes are created first then used as a basis for more specifically detailed child classes. Protected inheritance allows descendant classes to have full and direct access to those predecessor member items that are implicitly inherited into descendant classes.

One of the major benefits of object orientation is that when a structure or class is created, one can hide the data and functionality of the class from other programming structures and functions if access is not necessary. In C++, this is accomplished by using access modifiers. If a programmer wants to deny access to the internal information and functions of a class from outside of the class, the keyword "private" is used — but inter-class access between inter-class members is always allowed. To limit access only to descendant classes as in protected inheritance, the keyword "protected" is utilized. The keyword "public" allows full access to member variables and functions.

Inheritance in software has the benefit of allowing programming code, which has already been created, to be indirectly reused. When a child class is created, all of the member variables and functions of the predecessor classes automatically become part of the child. The programmer does not have to re-code them. This is a major advantage when large hierarchies of classes are needed. An example of this might be when entities in a biological taxonomy model need to replicated in software.

Private inheritance happens when predecessor classes have designated their member elements as private. Children who implicitly receive these variables and functions do not have direct, immediate access to them, thus preserving certain features of the parent and child. With protected inheritance, when a parent declares an element as protected, the variables or functions are inherited, and the child can access them, but other classes cannot. Public inheritance allows the child to integrate and manipulate parent features. It also lets other structures have access to the child members as well.

Protected inheritance is an important concept in C++ programming. It helps to define the constraints under which a program will operate. Concisely written and well-engineered programs that utilize inheritance help to reduce application errors, aid in troubleshooting and give controlled flexibility to the standard object orientated principles of information hiding and encapsulation.