GNU Smalltalk User's Guide
Smalltalk organizes all of its classes as a tree hierarchy.
At the very top of this hierarchy is class Object.
Following somewhere below it are more specific classes, such
as the ones we've worked with--strings, integers, arrays, and
so forth. They are grouped together based on their similarities;
for instance, types of objects which may be compared
as greater or less than each other fall under a class known
One of the first tasks when creating a new object is to
figure out where within this hierarchy your object falls.
Coming up with an answer to this problem is at least as much
art as science, and there are no hard-and-fast rules to nail
it down. We'll take a look at three kinds of objects to
give you a feel for how this organization matters.