Misplaced Pages

#869130

87-538: In computing, Strongtalk is a Smalltalk environment with optional static typing support. Strongtalk can make some compile time checks, and offer stronger type safety guarantees; this is the source of its name. It is non-commercial, though it was originally a commercial project developed by a small startup company named LongView Technologies (trading as Animorphic Systems ). David Griswold wanted to use Smalltalk more extensively, but then-extant implementations were insufficient for his needs. He wanted to improve

174-399: A mouse , Ethernet networking, and the ability to run multiple applications simultaneously. It is one of the first computers to use a WYSIWYG (What You See Is What You Get) text editor and has a bit-mapped display. The Alto did not succeed commercially, but it had a significant influence on the development of future computer systems. The Alto was designed for an operating system based on

261-530: A personal computer in the sense that it is used by one person sitting at a desk, in contrast with the mainframe computers and other minicomputers of the era. It is arguably "the first personal computer", although this title is disputed. More significantly (and perhaps less controversially), it may be considered to be one of the first workstation systems, with successors such as the Apollo workstations and systems by Symbolics (designed to natively run Lisp as

348-412: A string literal . For example: If the sequence does not include whitespace or punctuation characters, this can also be written as: Arrays: defines an array of four integers. defines a seven element array whose first element is a literal array, second element a byte array, third element the string 'four', and so on. Many implementations support the following literal syntax for ByteArrays: defines

435-543: A writable control store extension and has 128 (expandable to 512) KB of main memory organized in 16-bit words. Mass storage is provided by a hard disk drive that uses a removable 2.5 MB one-platter cartridge ( Diablo Systems , a company Xerox later bought) similar to those used by the IBM 2310 . The base machine and one disk drive are housed in a cabinet about the size of a small refrigerator ; one more disk drive can be added via daisy-chaining . Alto both blurs and ignores

522-411: A ByteArray of four integers. And last but not least, blocks ( anonymous function literals) Xerox Alto The Xerox Alto is a computer system developed at Xerox PARC (Palo Alto Research Center) in the 1970s. It is considered one of the first workstations or personal computers , and its development pioneered many aspects of modern computing. It features a graphical user interface (GUI),

609-470: A GUI, later using the desktop metaphor . The first machines were introduced on March 1, 1973, and in limited production starting one decade before Xerox's designs inspired Apple to release the first mass-market GUI computers. The Alto is contained in a relatively small cabinet and uses a custom central processing unit (CPU) built from multiple SSI and MSI integrated circuits . Each machine cost tens of thousands of dollars. Few were built initially, but by

696-462: A class's method dictionary. The part of the class hierarchy that defines classes can add new classes to the system. The system is extended by running Smalltalk-80 code that creates or defines classes and methods. In this way a Smalltalk-80 system is a "living" system, carrying around the ability to extend itself at run time. One can even extend the compiler at run-time; indeed this is how the Compiler

783-460: A code snippet by Ralph Johnson , demonstrating all the basic standard syntactic elements of methods: The following examples illustrate the most common objects which can be written as literal values in Smalltalk-80 methods. Numbers. The following list illustrates some of the possibilities. The last two entries are a binary and a hexadecimal number, respectively. The number before the 'r'

870-771: A complete redesign of the Lilith under the Name "Project Oberon" . In 1978, Xerox donated 50 Altos to the Massachusetts Institute of Technology , Stanford University , Carnegie Mellon University , and the University of Rochester . The National Bureau of Standards 's Institute for Computer Sciences in Gaithersburg, Maryland received one Alto in late 1978 along with Xerox Interim File System (IFS) file servers and Dover laser printers. These machines inspired

957-565: A development environment). In 1976 to 1977, the Swiss computer pioneer Niklaus Wirth spent a sabbatical at PARC and was excited by the Alto. Unable to bring back an Alto system to Europe, Wirth decided to build a new system from scratch and he designed with his group the Lilith . It was ready to use around 1980, before Apple released Lisa in 1981 and Macintosh in 1984. Around 1985, Wirth started

SECTION 10

#1732798731870

1044-431: A display of pixels corresponding to the ones and zeros of the memory data. Ethernet is likewise supported by minimal hardware, with a shift register that acts bidirectionally to serialize output words and deserialize input words. Its speed was designed to be 3 Mbit/s because the microcode engine can not go faster and continue to support the video display, disk activity, and memory refresh. Unlike most minicomputers of

1131-469: A larger program of Advanced Research Projects Agency (ARPA) 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 (one of the inventors of Smalltalk) also described a tablet computer he named

1218-648: A number of facilities such as distributed Smalltalk where messages are exchanged between multiple Smalltalk systems, database interfaces where objects are transparently faulted out of a database, promises , etc. The design of distributed Smalltalk influenced such systems as CORBA . Smalltalk-80 syntax is rather minimalist, based on only a handful of declarations and reserved words. In fact, only six "keywords" are reserved in Smalltalk: true , false , nil , self , super , and thisContext . These are properly termed pseudo-variables , identifiers that follow

1305-457: A spelling corrector. Each release consisted of a virtual image (platform-independent file with object definitions) 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

1392-514: A string: Two equal strings (strings are equal if they contain all the same characters) can be different objects residing in different places in memory. In addition to strings, Smalltalk has a class of character sequence objects named Symbol. Symbols are guaranteed to be unique—there can be no two equal symbols which are different objects. Because of that, symbols are very cheap to compare and are often used for language artifacts such as message selectors (see below). Symbols are written as # followed by

1479-525: 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

1566-517: Is a structurally reflective system which structure is defined by Smalltalk-80 objects. The classes and methods that define the system are also objects and fully part of the system that they help define. The Smalltalk compiler, which is itself written in Smalltalk and exists alongside all the other code in the system, compiles textual source code into method objects, typically instances of CompiledMethod . These get added to classes by storing them in

1653-421: Is always private to that object. Other objects can query or change that state only by sending requests (messages) to the object to do so. Any message can be sent to any object: when a message is received, the receiver determines whether that message is appropriate. If the message is not understood by the object then the virtual machine sends the doesNotUnderstand: message with the original message as an argument, and

1740-515: Is available for Windows XP (other ports are in the works) and includes a basic development environment. Smalltalk In Smalltalk, executing programs are built of opaque, atomic, so-called objects, which are instances of template code stored in classes. These objects intercommunicate by passing of messages, via an intermediary virtual machine environment (VM). A relatively small number of objects, called primitives, are not amenable to live redefinition, sometimes being defined independently of

1827-537: Is based mostly on the August 1976 Alto Hardware Manual by Xerox PARC. Alto uses a microcoded design, but unlike many computers, the microcode engine is not hidden from the programmer in a layered design. Applications such as Pinball take advantage of this to accelerate performance. The Alto has a bit-slice arithmetic logic unit (ALU) based on the Texas Instruments 74181 chip, a ROM control store with

SECTION 20

#1732798731870

1914-621: Is derived from Smalltalk-80 version 2 by way of Smalltalk-80 2.5 and ObjectWorks (both products of ParcPlace Systems, a Xerox PARC spin-off company formed to bring Smalltalk to the market). As an interesting link between generations, in 2001, Vassili Bykov implemented Hobbes, a virtual machine running Smalltalk-80 inside VisualWorks. ( Dan Ingalls later ported Hobbes to Squeak.) 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

2001-425: Is developed and maintained. Since the classes are objects, they can be asked questions such as "what methods do you implement?" or "what fields/slots/instance variables do you define?". So objects can easily be inspected, copied, (de) serialized and so on with generic code that applies to any object in the system. Smalltalk-80 also provides computational reflection, the ability to observe the computational state of

2088-574: Is implemented on top of the built-in constructs by the standard Smalltalk class library. (For performance reasons, implementations may recognize and treat as special some of those messages; however, this is only an optimization and is not coded into the language syntax.) The adage that "Smalltalk syntax fits on a postcard " may have originated in Alan Kay's original conception of the language, as related by him in practically every of tens or hundreds of public lectures, op. cit., or perhaps it could refer to

2175-535: Is implemented using this facility. One of the more interesting uses of this is in the Seaside web framework which relieves the programmer of dealing with the complexity of a Web Browser's back button by storing continuations for each edited page and switching between them as the user navigates a web site. Programming the web server using Seaside can then be done using a more conventional programming style. As with message sending Smalltalk-80 virtual machines optimize away

2262-471: Is now termed Smalltalk-72 and influenced the development of the Actor model . Its syntax and execution model were very different from modern Smalltalk variants. After significant revisions which froze some aspects of execution semantics to gain performance (by adopting a Simula -like class inheritance model of execution), Smalltalk-76 was created. This system had a development environment featuring most of

2349-641: Is summarized in the commonly heard phrase "In Smalltalk everything is an object", which may be more accurately expressed as "all values are objects", as variables are not. Since all values are objects, classes are also objects. Each class is an instance of the metaclass of that class. Metaclasses in turn are also objects, and are all instances of a class named Metaclass. Classes contain method dictionaries that map selectors (the equivalent of function procedure names in other languages) to method objects, objects that are executed to evaluate messages. Classes inherit from other classes, with either Object or ProtoObject at

2436-404: Is the radix or base. The base does not have to be a power of two; for example 36rSMALLTALK is a valid number equal to 80738163270632 decimal. Characters are written by preceding them with a dollar sign: Strings are sequences of characters enclosed in single quotes: To include a quote in a string, escape it using a second quote: Double quotes do not need escaping, since single quotes delimit

2523-492: Is the fact that a large number of the personal computers of tomorrow will be designed with knowledge gained from the development of the Alto. After the Alto, PARC developed more powerful workstations (none intended as projects ) informally termed "the D-machines": Dandelion (least powerful, but the only to be made a product in one form), Dolphin; Dorado (most powerful; an emitter-coupled logic (ECL) machine); and hybrids like

2610-626: Is the first computer with a graphical operating system, and was built on earlier graphical interface designs. It was conceived in 1972 in a memo written by Butler Lampson , inspired by the oN-Line System (NLS) developed by Douglas Engelbart and Dustin Lindberg at SRI International (SRI). Of further influence was the PLATO education system developed at the Computer-based Education Research Laboratory at

2697-419: 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. 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

Strongtalk - Misplaced Pages Continue

2784-486: Is the part of the system that implements the programming system itself, and developers can use the meta-model to do things like walk through, examine, and modify code in the running system, or find all the instances of a certain kind of structure (e.g., all instances of the Method class in the meta-model). Smalltalk-80 is a totally reflective system. Smalltalk-80 provides both structural and computational reflection. Smalltalk

2871-538: The ARPANET . The firm was reluctant to get into the computer business again with commercially untested designs, although many of the philosophies would ship in later products. Byte magazine stated in 1981, It is unlikely that a person outside of the computer-science research community will ever be able to buy an Alto. They are not intended for commercial sale, but rather as development tools for Xerox, and so will not be mass-produced. What makes them worthy of mention

2958-577: The Dynabook which resembles modern tablet computers like the iPad. 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 (MVC) 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 (e.g., entity-relation, dataflow, object model, etc.) of

3045-603: The Stack Overflow Developer Survey in 2017, but it was not among the 26 most loved programming languages of the 2018 survey. 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

3132-639: The Xerox 820 , it pointedly rejected the Alto design and opted instead for a very conventional model, a CP/M -based machine with the then-standard 80 by 24 character-only monitor and no mouse. With the help of PARC researchers, Xerox eventually developed the Star , based on the Dandelion workstation, and later the cost-reduced Star, the 6085 office system, based on the Daybreak workstation. These machines, based on

3219-518: The underscore character, instead having the left-arrow character used in ALGOL 60 and many derivatives for the assignment operator : this peculiarity may have been the source of the CamelCase style for compound identifiers . Altos were also microcode-programmable by users. The Alto helped popularize the use of raster graphics model for all output, including text and graphics. It also introduced

3306-880: The Alto's electronics. Due to the success of the pilot run, the team went on to produce approximately 2,000 units over the next ten years. Several Xerox Alto chassis are now on display at the Computer History Museum in Mountain View, California , one is on display at the Computer Museum of America in Roswell, Georgia , and several are in private hands. Running systems are on display at the System Source Computer Museum in Hunt Valley , Maryland . Charles P. Thacker

3393-522: The Alto, Apple engineers used the concepts in developing the Lisa and Macintosh systems. In 1981, Xerox commercialized a line of office computers, the Star , based on concepts from the Alto. A complete office system including several workstations, storage, and a laser printer cost up to $ 100,000 (equivalent to $ 335,000 in 2023). Like the Alto, the Star had little direct impact on the market. The Alto

3480-606: The Alto, including a television camera, the Hy-Type daisywheel printer and a parallel port, although these were quite rare. The Alto could also control external disk drives to act as a file server . This was a common application for the machine. Early software for the Alto was written in the programming language BCPL , and later in Mesa , which was not widely used outside PARC but influenced several later languages, such as Modula . The Alto used an early version of ASCII which lacked

3567-695: The Dandel-Iris. Before the advent of personal computers such as the Apple II in 1977 and the IBM Personal Computer (IBM PC) in 1981, the computer market was dominated by costly mainframes and minicomputers equipped with dumb terminals that time-shared the processing time of the central computer. Through the 1970s, Xerox showed no interest in PARC's work. When Xerox finally entered the PC market with

Strongtalk - Misplaced Pages Continue

3654-526: 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 (later VisualAge). Enfin

3741-631: The ETH Zuerich Lilith and Three Rivers Company PERQ workstations, and the Stanford University Network (SUN) workstation, which launched a spin-off company, Sun Microsystems . The Apollo/Domain workstation was heavily influenced by the Alto. Following the acquisition of an Alto, the White House information systems department sought to lead federal computer suppliers in its direction. The Executive Office of

3828-557: The President of the United States (EOP) issued a request for proposal for a computer system to replace the aging Office of Management and Budget (OMB) budget system, using Alto-like workstations, connected to an IBM-compatible mainframe. The request was eventually withdrawn because no mainframe producer could supply such a configuration. In December 1979, Apple Computer 's co-founder Steve Jobs visited Xerox PARC, where he

3915-491: 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 (OOP). Since inception, the language provided interactive programming via an integrated development environment . This requires reflection and late binding in

4002-697: The University of Illinois. The Alto was designed mostly by Charles P. Thacker . Industrial Design and manufacturing was sub-contracted to Xerox's Special Programs Group in El Segundo , whose team included program manager Doug Stewart, operations manager Abbey Silverstone , and industrial designer Bob Nishimura. An initial run of 30 units was produced by the Special Programs Group, working with John Ellenby at PARC and Stewart and Silverstone at El Segundo, who were responsible for re-designing

4089-510: 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,

4176-566: The Wildflower architecture described in a paper by Butler Lampson , incorporated most of the Alto innovations, including the graphical user interface with icons, windows, folders, Ethernet-based local networking, and network-based laser printer services. Xerox only realized its mistake in the early 1980s, after the Macintosh revolutionized the PC market via its bitmap display and the mouse-centered interface. Both of these were inspired by

4263-654: The Xerox System Development Department to design the Star workstations. Xerox was slow to realize the value of the technology that had been developed at PARC. The Xerox corporate acquisition of Scientific Data Systems (SDS, later XDS) in the late 1960s had no interest to PARC. PARC built their own emulation of the Digital Equipment Corporation PDP-10 named the MAXC. The MAXC was PARC's gateway machine to

4350-400: The boot button, different microcode and operating systems can be loaded. This gave rise to the expression "nose boot" where the keys needed to boot for a test OS release requires more fingers than the user can articulate. Nose boots were obsoleted by the move2keys program that shifts files on the disk so that a specified key sequence can be used. Several other I/O devices were developed for

4437-701: The business. In 1999, Seagull Software acquired the ObjectShare Java development lab (including the original Smalltalk/V and Visual Smalltalk development team), 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

SECTION 50

#1732798731870

4524-770: The central concept in Smalltalk-80 (but not in Smalltalk-72) is that of an object . An object is always an instance of a class . Classes are "blueprints" that describe the properties and behavior of their instances. For example, a GUI's window class might declare that windows have properties such as the label, the position and whether the window is visible or not. The class might also declare that instances support operations such as opening, closing, moving and hiding. Each particular window object would have its own values of those properties, and each of them would be able to perform operations defined by its class. A Smalltalk object can do exactly three things: The state an object holds

4611-428: The concept of the bit block transfer operation ( bit blit , BitBLT), as the fundamental programming interface to the display. Despite its small memory size, many innovative programs were written for the Alto, including: There was no spreadsheet or database software. The first electronic spreadsheet program, VisiCalc , did not appear until 1979. Technically, the Alto is a small minicomputer, but it could be considered

4698-471: The default implementation of doesNotUnderstand: raises an exception that if not caught opens the system's debugger. Alan Kay has commented that despite the attention given to objects, messaging is the most important concept in Smalltalk: "The big idea is 'messaging'—that is what the kernel of Smalltalk/Squeak is all about (and it's something that was never quite completed in our Xerox PARC phase)." Unlike most other languages, Smalltalk code can be modified while

4785-526: The distinction between functional elements. Rather than a distinct central processing unit with a well-defined electrical interface (such as a system bus ) to storage and peripherals, the Alto ALU interacts directly with hardware interfaces to memory and peripherals, driven by microinstructions that are output from the control store. The microcode machine supports up to 16 cooperative multitasking tasks, each with fixed priority . The emulator task executes

4872-529: The era, Alto does not support a serial terminal for user interface. Apart from an Ethernet connection, the Alto's only common output device is a bi-level (black and white) cathode-ray tube (CRT) display with a tilt-and-swivel base, mounted in portrait orientation rather than the more common "landscape" orientation. Its input devices are a custom detachable keyboard , a three-button mouse , and an optional 5-key chorded keyboard (chord keyset). The last two items had been introduced by SRI's On-Line System and

4959-423: The expensive use of contexts internally, providing the illusion and flexibility of a spaghetti stack without most its costs. Essentially context objects are created lazily as required, for example when a message is sent to the thisContext variable. An example of how Smalltalk can use reflection is the mechanism for handling errors. When an object is sent a message that it does not implement, the virtual machine sends

5046-436: The first being the sender of the former. In this way the stack is a linked list of context objects, and the debugger is essentially an inspector of this "spaghetti stack". By sending messages to thisContext a method activation can ask questions like "who sent this message to me". These facilities make it possible to implement coroutines or Prolog -like back-tracking without modifying the virtual machine. The exception system

5133-496: 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 (ANSI) Smalltalk was ratified in 1998 and represents the standard version of Smalltalk. Smalltalk took second place for "most loved programming language" in

5220-646: The last two being vectors of bytes. Consequently Smalltalk can evaluate 52 factorial to produce 80658175170943878571660636856403766975289505440883277824000000000000. The transition from small to large integers is transparent to the programmer; variables do not require type declarations. This makes the system both concise and flexible. A programmer can change or extend (through subclassing ) the classes that implement what in other languages would be primitive values, so that new behavior can be defined for their instances—for example, to implement new control structures—or even so that their existing behavior will be changed. This fact

5307-619: The late 1970s, about 1,000 were in use at various Xerox laboratories, and about another 500 in several universities. Total production was about 2,000 systems. The Alto became well known in Silicon Valley and its GUI was increasingly seen as the future of computing. In 1979, Steve Jobs arranged a visit to Xerox PARC, during which Apple Computer personnel received demonstrations of Xerox technology in exchange for Xerox being able to purchase stock options in Apple. After two visits to see

SECTION 60

#1732798731870

5394-534: The late 1990s decided to back Java instead and, as of 2005 , is supported by Instantiations, Inc. Instantiations renamed the product VA Smalltalk (VAST Platform) 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 (OLPC) project,

5481-518: The mouse was an instant success among Alto users, but the chord keyset never became popular. In the early mice, the buttons are three narrow bars, arranged top to bottom rather than side to side; they were named after their colors in the documentation. The motion is sensed by two perpendicular wheels. These were soon replaced with a ball-type mouse, which was invented by Ronald E. Rider and developed by Bill English . These are photo-mechanical mice, first using white light, and then infrared (IR), to count

5568-406: The normal instruction set to which most applications are written; that instruction set is similar to a Data General Nova . Other tasks serve the display, memory refresh, disk, network, and other I/O functions. For example, the bitmap display controller is little more than a 16- bit shift register ; microcode moves display refresh data from main memory to the shift register, which serializes it into

5655-452: The now familiar tools, including a class library code browser/editor. Smalltalk-80 added metaclasses , to help maintain the "everything is an object" (except variables) paradigm by associating properties and behavior with individual classes, and even primitives such as integer and Boolean values (for example, to support different ways to create instances). Smalltalk-80 was the first language variant made available outside of PARC. In 1981, it

5742-411: The object the doesNotUnderstand: message with a reification of the message as an argument. The message (another object, an instance of Message ) contains the selector of the message and an Array of its arguments. In an interactive Smalltalk system the default implementation of doesNotUnderstand: is one that opens an error window (a Notifier) reporting the error to the user. Through this and

5829-476: 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 (RAD) or prototyping, and software design patterns . The highly productive environment provided by Smalltalk platforms made them ideal for rapid, iterative development. Smalltalk emerged from

5916-468: The performance, add type-checking, and use native graphical user interface (GUI) widgets . His efforts resulted in the 1993 paper he co-authored with Gilad Bracha . This version was based on adding type-checking to the ParcPlace Systems implementation of Smalltalk. However, an implementation begun from scratch could gain a better typing system. He became interested in the improvements that

6003-471: The reflective facilities the user can examine the context in which the error occurred, redefine the offending code, and continue, all within the system, using Smalltalk-80's reflective facilities. By creating a class that understands (implements) only doesNotUnderstand:, one can create an instance that can intercept any message sent to it via its doesNotUnderstand: method. Such instances are called transparent proxies. Such proxies can then be used to implement

6090-410: The root of the class hierarchy. Sending a message to an object at the most abstract involves fetching the class of the receiver (the object being sent the message) and looking up the message's selector in the class's method dictionary, followed by the superclass and so on until the method is found or doesNotUnderstand is sent. Smalltalk virtual machines use various techniques to speed up message lookup so

6177-404: The rotations of wheels inside the mouse. Each key on the Alto keyboard is represented as a separate bit in a set of memory locations. As a result, it is possible to read multiple key presses concurrently . This trait can be used to alter from where on the disk the Alto boots. The keyboard value is used as the sector address on the disk to boot from, and by holding specific keys down while pressing

6264-462: The rules for variable identifiers but denote bindings that a programmer cannot change. The true , false , and nil pseudo-variables are singleton instances. self and super refer to the receiver of a message within a method activated in response to that message, but sends to super are looked up in the superclass of the method's defining class rather than the class of the receiver, which allows methods in subclasses to invoke methods of

6351-473: The same name in superclasses. thisContext refers to the current activation record. The only built-in language constructs are message sends, assignment, method return and literal syntax for some objects. From its origins as a language for children of all ages, standard Smalltalk syntax uses punctuation in a manner more like English than mainstream coding languages. The remainder of the language, including control structures for conditional evaluation and iteration,

6438-568: 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 (GUI) and the what you see is what you get ( WYSIWYG ) 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

6525-406: The sense that they are instances of corresponding classes, and operations on them are invoked by sending messages. For efficiency and generality integers are implemented by four classes, Integer, the abstract superclass of all integers, SmallInteger, whose instances fit in a machine word, for example having a 61-bit signed range in a 64-bit implementation, LargePositiveInteger and LargeNegativeInteger,

6612-449: The standard for all the integrated development environments , starting with Lisp Machine environments, that came after. Smalltalk uses several commands that rhyme with the "-ect" suffix. 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." As in other object-oriented languages,

6699-502: The system is running. Live coding and applying fixes 'on-the-fly' is a dominant programming methodology for Smalltalk and is one of the main reasons for its productivity. Smalltalk is a "pure" object-oriented programming language, meaning that, unlike C++ and Java , there are no primitive types. All values are represented as objects and computation on integers uses message sending just like any other object. In Smalltalk, types such as integers, Booleans and characters are also objects, in

6786-465: The system provides both a simple consistent message binding mechanism and good efficiency. Code blocks —Smalltalk's way of expressing anonymous functions —are also objects. They have a very lightweight syntax and are used throughout the system to implement control structures, especially for the Collection hierarchy. Reflection is a feature of having a meta-model as Smalltalk does. The meta-model

6873-410: The system. In languages derived from the original Smalltalk-80 the current activation of a method is accessible as an object named via a pseudo-variable (one of the six reserved words), thisContext , which corresponds to a stack frame in conventional language implementations, and is called a "context". Sending a message is done within some context, and to evaluate the message another context is created,

6960-478: The team for the language Self had achieved, and envisioned the same methods used to improve Smalltalk. Urs Hölzle , who worked on the powerful Self compiler, spoke with Griswold about implementing the same type feedback in a Smalltalk compiler. Griswold, Hölzle, Lars Bak , and others formed a small company (LongView Technologies, doing business as Animorphic Systems) to re-implement Strongtalk. Work began in 1994 and they completed an implementation in 1996. The firm

7047-577: Was awarded the 2009 Turing Award of the Association for Computing Machinery on March 9, 2010, for his pioneering design and realization of the Alto. The 2004 Charles Stark Draper Prize was awarded to Thacker, Alan C. Kay , Butler Lampson, and Robert W. Taylor for their work on Alto. On October 21, 2014, Xerox Alto's source code and other resources were released from the Computer History Museum. The following description

7134-541: Was bought by Sun Microsystems in 1997, and the team got focused on Java , releasing the HotSpot virtual machine, and work on Strongtalk stalled. Sun released the 1997 re-implementation of Strongtalk as open-source software under a revised BSD license , including the Strongtalk system image in 2002, and the virtual machine in 2006. Strongtalk is touted as the fastest implementation of Smalltalk . Strongtalk

7221-519: 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

7308-625: 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, CA. ObjectShare ( NASDAQ : OBJS) 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

7395-406: 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

7482-612: Was shown the Smalltalk -76 object-oriented programming environment, networking, and most importantly the WYSIWYG , mouse-driven graphical user interface provided by the Alto. At the time, he didn't recognize the significance of the first two, but was excited by the last one. The GUI was promptly integrating into Apple's products, first into the Lisa and then in the Macintosh , and Jobs recruited several key researchers from PARC. In 1980-1981, Altos were used by engineers at PARC and at

7569-510: Was the product of research led by Alan Kay at Xerox Palo Alto Research Center (PARC); 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. The first version, termed Smalltalk-71, was created by Kay in a few mornings on a bet that a programming language based on the idea of message passing inspired by Simula could be implemented in "a page of code". A later variant used for research work

#869130