Notes:
The concept of encapsulation (information hiding) forms the foundation of object orientation. In a partial sense, objects can be viewed as symbol tables that can be persistent or non-persistent. These objects, by definition, require symbol scoping. Symbol scoping is the means by which only certain data is made available to a particular execution or object context.
What evolved were several scopes. The instance variable (I%) has a scope of the persistent objects lifetime. The domain variable (O%) has the lifetime of a domain. Temporary variables (A%) have a lifetime as long as the method is executing.
Other variables scopes exist as a natural extension of this concept.