Simula, Smalltalk, and Eiffel

These are the principal specialized "Object Oriented" languages. Simula was developed in the mid-1960s as a language for simulations (simulations of anything you wanted: modelling aircraft movements at an airport, modelling the spread of a disease in a population of individuals, modelling the activities in an automated car wash. Simula was based on Algol-60 but added a variety of constructs that were needed for simulation work. Essentially, it allowed the programmer to create in the computer a set of "objects" (each of which owned some resources and had specified behaviours) that modelled things in the real world. Once the objects had been created, the Simula run-time system could mimic the passage of time and could allow the programmer to track interactions among the objects.

The Smalltalk language was developed by the very innovative research group at Xerox's Palo Alto Research Centre (the same group as invented the prototype for the "Macintosh/Windows" OS and interface). Smalltalk offers a different way of thinking about programming problems. Usually, each problem is treated as if it were totally new. The problem gets analyzed, broken down into subtasks, and then new code is written to handle each of these subtasks. Smalltalk encourages an alternative view; instead of writing new special purpose code, try to find a way of building up a solution to a problem by combining reusable components. The reusable components are Smalltalk objects. A Smalltalk system provides hundreds of different kinds (classes) of "off the shelf " reusable components. Actually, Smalltalk is an interpretive system (a bit like Lisp) and the language is not strictly in the Algol family.

In some respects, Eiffel is the best programming language currently available. It takes advantage of the experience gained with earlier languages like Simula, Pascal, Smalltalk, ADA and others. It is a compiled language (so Eiffel programs are much more efficient than interpreted Smalltalk programs). The basic idea is the same as Smalltalk, i.e. the best way to construct programs is to build them out of reusable objects. Although in many respects very good, Eiffel is restrictive. It enforces the use of an Object Oriented (OO) style. You have to learn several styles, not just OO. For this reason, you are learning C++ because it supports conventional procedural style as well as OO.