Guess how you create a new class? This should be getting monotonous by now—by sending a message to an object. The way we create our first “custom” class is by sending the following message:
Object subclass: #Account. Account instanceVariableNames: 'balance'.
Quite a mouthful, isn’t it? GNU Smalltalk provides a
simpler way to write this, but for now let’s stick with this.
Conceptually, it isn’t really that bad. The Smalltalk variable
Object is bound to the grand-daddy of all classes on the
system. What we’re doing here is telling the Object class
that we want to add to it a subclass known as Account.
instanceVariableNames: 'balance' tells the new
class that each of its objects (instances) will have a
hidden variable named