The class is defined in two different sections namely @interface and @implementation . Almost everything is in form of objects. Objects receive messages and objects are often referred as receivers. Objects contain instance variables. Objects and instance variables have scope.
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a class describes the contents of the objects that belong to it : it describes an aggregate of data fields (called instance variables), and defines the operations (called methods). object: an object is an element (or instance) of a class; objects have the behaviors of their class.
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