Attribute Slots
Attribute slots are used to manage the setting and querying of instance variables. We define now a person with three attributes name, salary and projects.Attributes might have a default value or they might be multivalued. When an instance of class Person is created, the slot names can be used for specifying values for the slots.
Person p1 -name "Joe"
Object p1 has three instance variables, namely name, salary and projects.