Classes and Instances
| Terminology | Summary | |---+---| | class | An object that describes the implementation of a set of similar objects. | | instance | One of the objects described by a class; it has memory and responds to messages. | | instance variable | A variable available to a single object for the entire lifetime of the object; instance variables can be named or indexed. | | protocal description | A description of a class in terms of its instances public message protocal. | | implementation description | A message selector and a set of argument names, one for each argument that a message with this selector must have. | | temporary variable | A variable created for a specific activity and available only for the duration of that activity. | | class variable | A variable shared by all the instances of a single class. | | global variable | A variable shared by all the instances of all classes. | | pool variable | A variable shared by the instances of a set of classes. | | Smalltalk | A pool shared by all classes that contains the global variables. | | method | A procedure describing how to perform one of an object's operations; it is made up of a message pattern, temporary variable declaration, and a sequence of expressions. A method is executed when a message matching its message pattern is sent to an instance of the class in which the method is found. | | argument name | Name of a pseudo-variable available to a method only for the duration of that method's execution; the value of the argument names are the arguments of the message that invoked the method. | | up | When used in a method, indicates that the value of the next expression is to be the value of the method. | | self | A pseudo-variable referring to the receiver of a message. | | message category | A group of methods in a class description. | | primitive method | An operation performed directly by the Smalltalk-80 virtual machine; it is not described as a sequence of Smalltalk-80 expressions. |