The introduction of Smalltalk
came along with an, at the time,
- literal -- constants
- object -- action by messages
- class -- collection of protocols
- protocol -- related methods
- category -- collection of classes
slide: Smalltalk -- terminology
Most important is the notion
of object, which is something
that acts in response to messages
(by executing a method procedure).
In Smalltalk, everything is an object.
Moreover, every object is an instance of
A class is the description
of a collection of objects which share
the same structure and applicable methods.
The methods of both objects and classes
(considered as an object) are grouped
in so-called protocols.
Related collections of classes may be
grouped in so-called categories.
Both protocols and categories
are merely syntactic add-ons,
meant to facilitate programming.