Object-oriented programming languages. In object-oriented programming languages, a key concept is to encapsulate imple- mentation details within so-called objects which represent an association of data with its operations. Specifically, the operations provide an interface between the object’s data and its user rendering it unnecessary for the user to access the data directly. Due to this information hiding, the developer of the object, on the one hand, is free in choosing (or even in changing) the appropriate implementation for the data as well as the operations and, on the other hand, the user does not have to rely on a specific implementation but only on the interface. This idea can be traced back to the early 1960’s. One of the first and probably most influen- tial object-oriented languages was Simula [22], developed by Xxx-Xxxxx Xxxx and Xxxxxxx Xxxxxxx. Xxxxxx did not only introduce the concept of objects but also the notion of classes, used as “blue-prints” from which new objects can be instan- tiated. Moreover, the language supported sub-classing and overriding. That is, a class can inherit the data types and operations of another class and, beyond that, it may re-define such an inherited operation by providing a new implementation. Inspired by Xxxxxx, Xxxx Xxx led the development of Smalltalk in the 1970’s [30]. With Smalltalk Xxx introduced the term object-oriented programming to express the pervasive use of objects and messages passing. Indeed, in Smalltalk everything is an object, including classes which can be created and modified dynamically. As for the mainstream software application development, the object-oriented programming approach had its break-through in the early 1990’s largely due to C++, developed by Xxxxxx Xxxxxxxxxx [67]. The programming language C++, orig- inally named “C with Classes”, can be considered as an extension of the language C by object-orientation. Xxxxxxxxxx developed C++ with the intention to make Xxxxxx’x object-oriented features available for real word software applications, since Simula was too slow for practical use. In fact, C regarded as a middle-level language, was and still is one of the most popular programming languages due to its execution speed. The high performance of nowadays computer hardware, however, allows to use more high level computer languages also for most of the mainstream soft- ware applications. As a consequence, lots of high level programming language and scripting language with support for object-orientation have been develo...
