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Smalltalk An operating system and object-oriented programming language that was developed at Xerox PARC. As an integrated environment, it eliminates the distinction between programming language and operating system. It also allows its user interface and behavior to be customized.
Smalltalk was the first object-oriented programming language to become popular. It was originally used to create prototypes of simpler programming languages and the graphical interfaces that are so popular today. Smalltalk was first run on Xerox's Alto computer, which was designed for it. In 1980, Smalltalk-80 was licensed to Tektronix, Apple, HP and TI for internal use. The first commercial release of Smalltalk was Methods from Digitalk in 1983, which later evolved into Visual Smalltalk. In 1997, Smalltalk became an ANSI standard (X3J20). See VisualWorks, Visual Smalltalk, VisualAge and Alto.
| (language) | Smalltalk - The pioneering object-oriented programming system
developed in 1972 by the Software Concepts Group, led by Alan Kay, at Xerox PARC between 1971 and 1983. It includes a
language, a programming environment, and an extensive object
library.
Smalltalk took the concepts of class and message from
Simula-67 and made them all-pervasive. Innovations included
the bitmap display, windowing system, and use of a mouse.
The syntax is very simple. The fundamental construction is
to send a message to an object:
object message
or with extra parameters
object message: param1 secondArg: param2 .. nthArg: paramN
where "secondArg:" etc. are considered to be part of the
message name.
Five pseudo-variables are defined: "self", "super", "nil",
"true", "false". "self" is the receiver of the current
message. "super" is used to delegate processing of a message
to the superclass of the receiver. "nil" is a reference to
"nothing" (an instance of UndefinedObject). All variables
initially contain a reference to nil. "true" and "false" are
Booleans.
In Smalltalk, any message can be sent to any object. The
recipient object itself decides (based on the message name,
also called the "message selector") how to respond to the
message. Because of that, the multiple inheritance system
included in the early versions of Smalltalk-80 appeared to be
unused in practice. All modern implementations have single
inheritance, so each class can have at most one superclass.
Early implementations were interpreted but all modern ones
use dynamic translation (JIT).
Early versions were Smalltalk-72, Smalltalk-74, Smalltalk-76
(inheritance taken from Simula, and concurrency), and
Smalltalk-78, Smalltalk-80. Other versions include Little Smalltalk, Smalltalk/V, Kamin's interpreters. Current
versions are VisualWorks, Squeak, VisualAge, Dolphin Smalltalk, Object Studio, GNU Smalltalk.
See also: International Smalltalk Association.
UIUC Smalltalk archive.
FAQ.
Usenet newsgroup: news:comp.lang.smalltalk.
["The Smalltalk-76 Programming System Design and
Implementation", D.H. Ingalls, 5th POPL, ACM 1978, pp. 9-16]. | |
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