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The pioneering object-oriented programming systemdeveloped in 1972 by the Software Concepts Group, led by AlanKay, at Xerox PARC between 1971 and 1983. It includes alanguage, a programming environment, and an extensive objectlibrary.Smalltalk took the concepts of class and message fromSimula-67 and made them all-pervasive. Innovations includedthe bitmap display, windowing system, and use of a mouse.The syntax is very simple. The fundamental construction isto send a message to an object:object messageor with extra parametersobject message: param1 secondArg: param2 .. nthArg: paramNwhere "secondArg:" etc. are considered to be part of themessage name.Five pseudo-variables are defined: "self", "super", "nil","true", "false". "self" is the receiver of the currentmessage. "super" is used to delegate processing of a messageto the superclass of the receiver. "nil" is a reference to"nothing" (an instance of UndefinedObject). All variablesinitially contain a reference to nil. "true" and "false" areBooleans.In Smalltalk, any message can be sent to any object. Therecipient object itself decides (based on the message name,also called the "message selector") how to respond to themessage. Because of that, the multiple inheritance systemincluded in the early versions of Smalltalk-80 appeared to beunused in practice. All modern implementations have singleinheritance, so each class can have at most one superclass.Early implementations were interpreted but all modern onesuse dynamic translation (JIT).Early versions were Smalltalk-72, Smalltalk-74, Smalltalk-76(inheritance taken from Simula, and concurrency), andSmalltalk-78, Smalltalk-80. Other versions include LittleSmalltalk, Smalltalk/V, Kamin's interpreters. Currentversions are VisualWorks, Squeak, VisualAge, DolphinSmalltalk, Object Studio, GNU Smalltalk.See also: International Smalltalk Association.UIUC Smalltalk archive (http://st-www.cs.uiuc.edu/).FAQ (http://XCF.Berkeley.EDU/pub/misc/smalltalk/FAQ/).Usenet newsgroup: news:comp.lang.smalltalk.["The Smalltalk-76 Programming System Design andImplementation", D.H. Ingalls, 5th POPL, ACM 1978, pp. 9-16].