Introduction to Smalltalk

Smalltalk is completely object-oriented; more than other OO programming languages claim to be. In its design there is no compromise between objects and machine-dependent types (strings, number representations, ...). Everything is an object!

What is an object anyway?

• Objects have a number of state variables. Example: a telephone knows of its colour, number.
• Every object is unique, thus we can access an object by its unique identification. Think of something like car plates or telephone numbers.
• Every object is of a specified class. A class is just the meta information that defines objects. A class can actually create new objects (named instances) of its type.
• Objects do respond to messages, which may take parameters or not.
• Further, we need to consider an object's lifetime, that is, the duration of the existence of the object, starting with its creation, lasting till its destruction. You control it!

Others? There are none, thus everything is an object. A Smalltalk program lives in an environment full of objects. It does only see objects and sends messages to them following your programming code, then, waits for the message to return and continues.

Why objects?

You may have wondered why there is a need for such things like object-oriented programming. Considering MolTalk as an application of object-oriented programming it jumps right at your eyes: once you know an object's identifier you can access all of its information by simply sending messages to it. Objects can ideally represent the hierarchical organisation of information stored in macromolecular structures.