Smalltalk
Smalltalk is a purely object-oriented programming language that was originally created in the 1970s for educational use, specifically for constructionist learning, but later found use in business. It was created at Xerox PARC by Learning Research Group scientists, including Alan Kay, Dan Ingalls, Adele Goldberg, Ted Kaehler, Diana Merry, and Scott Wallace.
In Smalltalk, executing programs are built of opaque, atomic objects, which are instances of template code stored in classes. These objects intercommunicate by passing of messages, via an intermediary virtual machine environment. A relatively small number of objects, called primitives, are not amenable to live redefinition, sometimes being defined independently of the Smalltalk programming environment.
Having undergone significant industry development toward other uses, including business and database functions, Smalltalk is still in use today. When first publicly released, Smalltalk-80 presented numerous foundational ideas for the nascent field of object-oriented programming.
Since inception, the language provided interactive programming via an integrated development environment. This requires reflection and late binding in the language execution of code. Later development has led to at least one instance of Smalltalk execution environment which lacks such an integrated graphical user interface or front-end.
Smalltalk-like languages are in active development and have gathered communities of users around them. American National Standards Institute Smalltalk was ratified in 1998 and represents the standard version of Smalltalk.
Smalltalk took second place for "most loved programming language" in the Stack Overflow Developer Survey in 2017, but it was not among the 26 most loved programming languages of the 2018 survey.
History
There are a large number of Smalltalk variants. The unqualified word Smalltalk is often used to indicate the Smalltalk-80 language and compatible VM, the first version to be made publicly available and created in 1980. The first hardware-environments which ran the Smalltalk VMs were Xerox Alto computers.Smalltalk was the product of research led by Alan Kay at Xerox Palo Alto Research Center ; Alan Kay designed most of the early Smalltalk versions, Adele Goldberg wrote most of the documentation, and Dan Ingalls implemented most of the early versions. Smalltalk-71 was an unpublished language design by Kay. In September 1972, Kay made a bet that the core of a programming language based on the idea of message passing could be implemented in "a page of code"; by about the eighth morning, a working interpreter scheme had emerged, forming the basis for what is now termed Smalltalk-72. Its syntax and execution model were very different from modern Smalltalk variants.
The first Smalltalk interpreter actually implemented was for Smalltalk-72, and was written by Dan Ingalls in about 700 lines of BASIC in October 1972 for the Data General Nova. This version was demonstrated at the MIT AI Lab by Alan Kay in November that year; published accounts of the Actor model cite this period and Smalltalk-72's message-passing ideas as an influence on the model's development. The first bitmap line drawing routines were implemented by Ted Kaehler in late December 1972. Smalltalk-72 was ported to the Xerox Alto in April 1973, the same month the first units began operation.
After significant revisions which froze some aspects of execution semantics to gain performance, Smalltalk-76 was created. This system had a development environment featuring most of the now-familiar tools, including a class library code browser/editor. Smalltalk-80 added metaclasses, to help maintain the "everything is an object" paradigm by associating properties and behavior with individual classes, and even primitives such as integer and Boolean values.
Smalltalk-80 was the first language variant made available outside of PARC. In 1981, it was shared with Tektronix, Hewlett-Packard, Apple Computer, and DEC for review and debugging on their platforms. The August 1981 issue of Byte Magazine was devoted to Smalltalk-80 and brought its ideas to a large audience. Several books on Smalltalk-80 were also published. Smalltalk-80 became the basis for all future commercial versions of Smalltalk. The final release of Smalltalk-80 Version 1 was in November 1981. Xerox only distributed Version 1 to Apple, DEC, HP, and Tektronix, but these companies were allowed unrestricted redistribution via any system they built. This encouraged the wide spread of Smalltalk. Later, in 1983, Xerox released Smalltalk-80 Version 2. This version was generally available to the public, although under a restrictive license. Versions 1 and 2 were fairly similar, although Version 2 did have some added features such as a spelling corrector. Each release consisted of a virtual image and a virtual machine specification.
ANSI Smalltalk has been the standard language reference since 1998. Two currently popular Smalltalk implementation variants are descendants of those original Smalltalk-80 images. Squeak is an open source implementation derived from Smalltalk-80 Version 1 by way of Apple Smalltalk. VisualWorks is derived from Smalltalk-80 version 2 by way of Smalltalk-80 2.5 and ObjectWorks. As an interesting link between generations, in 2001, Vassili Bykov implemented Hobbes, a virtual machine running Smalltalk-80 inside VisualWorks.
During the late 1980s to mid-1990s, Smalltalk environments, including support, training and add-ons, were sold by two competing organizations: ParcPlace Systems and Digitalk, both California-based. ParcPlace Systems tended to focus on the Unix/Sun microsystems market, while Digitalk focused on Intel-based PCs running Microsoft Windows or IBM's OS/2. Both firms struggled to take Smalltalk mainstream due to Smalltalk's substantial memory needs, limited run-time performance, and initial lack of supported connectivity to SQL-based relational database servers. While the high price of ParcPlace Smalltalk limited its market penetration to mid-sized and large commercial organizations, the Digitalk products initially tried to reach a wider audience with a lower price. IBM initially supported the Digitalk product, but then entered the market with a Smalltalk product in 1995 named VisualAge/Smalltalk. Easel introduced Enfin at this time on Windows and OS/2. Enfin became far more popular in Europe, as IBM introduced it into IT shops before their development of IBM Smalltalk. Enfin was later acquired by Cincom Systems, and is now sold under the name ObjectStudio, and is part of the Cincom Smalltalk product suite.
In 1995, ParcPlace and Digitalk merged into ParcPlace-Digitalk and then rebranded in 1997 as ObjectShare, located in Irvine, California. ObjectShare was traded publicly until 1999, when it was delisted and dissolved. The merged firm never managed to find an effective response to Java as to market positioning, and by 1997 its owners were looking to sell the business. In 1999, Seagull Software acquired the ObjectShare Java development lab, and still owns VisualSmalltalk, although worldwide distribution rights for the Smalltalk product remained with ObjectShare who then sold them to Cincom. VisualWorks was sold to Cincom and is now part of Cincom Smalltalk. Cincom has backed Smalltalk strongly, releasing multiple new versions of VisualWorks and ObjectStudio each year since 1999.
Cincom, GemTalk, and Instantiations, continue to sell Smalltalk environments. IBM ended VisualAge Smalltalk, having in the late 1990s decided to back Java instead and,, is supported by Instantiations, Inc. Instantiations renamed the product VA Smalltalk and continue to release new versions yearly. The open Squeak implementation has an active community of developers, including many of the original Smalltalk community, and was used to provide the Etoys environment on the One Laptop per Child project, a toolkit for developing collaborative applications Croquet Project, and the Open Cobalt virtual world application. GNU Smalltalk is a free software implementation of a derivative of Smalltalk-80 from the GNU project. Pharo Smalltalk is a fork of Squeak oriented toward research and use in commercial environments.
As of 2016, a significant development that has spread across all Smalltalk environments is the increasing usage of two web frameworks, Seaside and AIDA/Web, to simplify the building of complex web applications. Seaside has seen considerable market interest with Cincom, Gemstone, and Instantiations incorporating and extending it.
Influences
Smalltalk was one of many object-oriented programming languages based on Simula. Smalltalk is also one of the most influential programming languages. Virtually all of the object-oriented languages that came after—Flavors, CLOS, Objective-C, Java, Python, Ruby, and many others—were influenced by Smalltalk. Smalltalk was also one of the most popular languages for agile software development methods, rapid application development or prototyping, and software design patterns. The highly productive environment provided by Smalltalk platforms made them ideal for rapid, iterative development.Smalltalk emerged from a larger program of Advanced Research Projects Agency-funded research that in many ways defined the modern world of computing. In addition to Smalltalk, working prototypes of things such as hypertext, GUIs, multimedia, the mouse, telepresence, and the Internet were developed by ARPA researchers in the 1960s. Alan Kay also described a tablet computer he named the Dynabook which resembles modern tablet computers.
Smalltalk environments were often the first to develop what are now common object-oriented software design patterns. One of the most popular is the model–view–controller pattern for user interface design. The MVC pattern enables developers to have multiple consistent views of the same underlying data. It's ideal for software development environments, where there are various views of the same underlying specification. Also, for simulations or games where the underlying model may be viewed from various angles and levels of abstraction.
In addition to the MVC pattern, the Smalltalk language and environment were influential in the history of the graphical user interface and the what you see is what you get user interface, font editors, and desktop metaphors for UI design. The powerful built-in debugging and object inspection tools that came with Smalltalk environments set the standard for all the integrated development environments, starting with Lisp Machine environments, that came after.
Smalltalk uses several collection filter operators that rhyme with the "-ect" suffix, collect:, select:, inject:into:, et al. This was inspired by a line from the 1967 Arlo Guthrie monologue "Alice's Restaurant Massacree," in which Guthrie underwent a battery of being "injected, inspected, detected, infected, neglected and selected."