This book does not talk about one specific programming language like C++, C# or Java. Instead this is a theoretical explanation of Object-oriented programming paradigm used in computer programming to build applications and software. This book would contain a design language to demonstrate the concepts of object-oriented paradigm. These would resemble to those of C++ or C#. Typically, Java is used for object-oriented programming, but I cannot find any reason to “not” use C++ or C# for the teaching purposes when they also support the same concepts and same paradigm in a much better and simpler way.