76 ;;Quote: all procedures make assumptions about the form of data they manipulate

76 ;;Quote: in an improperly functioning system, procedures can get unexpected data

76 ;;Quote: an object-oriented system has a single entity, the object, to represent both information and its manipulation

76 ;;Quote: manipulate information by sending a message to an object in an object-oriented system

78 ;;Quote: methods can only send messages to objects, they can not call methods directly; implements strong typing

82 ;;Quote: the external view of an object is its protocol, i.e., the set of messages that it responds to

82 ;;Quote: within an object, data in private variables and procedures in methods; localizes the data/program distinction

82 ;;Quote: to inquire about information, must send a message to an object; this hides the object's implementation

82 ;;Quote: all instances of a class have the same instance variables but different values

82 ;;Quote: two instances of a class respond differently to a message only if the values of their instance variables differ; they use the same method