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The Early History Of Smalltalk by Alan Kay
Abstract TOC Introduction Section I II III IV V VI
For References & Appendixes see pdf or book versions.

V. 1976-80--The first modern Smalltalk (-76), its birth, applications, and improvements

By the end of 1975 I felt that we were losing our balance--that the "Dynabook for children" idea was slowily dimming out--or perhaps starting to be overwhelmed by professional needs. In January 1976, I took the whole group to Pajaro Dunes for a three day offsite to bring up the issues and try to reset the compass. It was called "Let's Burn Our Disk Packs." There were no shouting matches, the group liked (I would go so far to say: loved) each other too much for that. But we were troubled. I used the old aphorism that "no biological organism can live in its own waste products" to please for a really fresh start: a hw-sw system very different from the ALTO and Smalltalk, One thing we all did agree on was that the current Smalltalk's power did not match our various levels of aspiration. I thought we needed something different, as I did not see how OOP by itself was going to solve our end-user problems. Others, particularly some of the grad students, really wanted a better Smalltalk that was faster and could be used for bigger problems. I think Dan felt that a better Smalltalk could be the vehicle for the different system I wanted, but could not describe clearly. The meeting was not a disaster, and we went back to PARC still friends and colleagues, but the absolute cohesiveness of the first four years never rejelled. I started designing a new small machine and language I called the NoteTaker and dan started to design Smalltalk-76.

The reason I wanted to "burn the disk packs" is that I had a very McLuhanish feeling about media and environments: that once we've shaped tools, in his words, they hum around and "reshape us." Of course this is a great idea if the tools are really good and aimed squarey at the issues in question. But the other edge of the sword cuts as deep--that inadquate tools and environments still reshape our thinking in spite of their problems, in part, because we want paradigms to guide our goals. Strong paradigms like LISP and Smalltalk are so compelling that they eat their young: when you look at an application in either of these two systems, they resemble the systems themselves, not a new idea. When I looked at Smalltalk in 1975, I was looking at something great, but I did not see an enduser language, I did not see a solution to the original goal of a "reading" and "writing" computer medium for children. I wanted to stop, dynamite everything and start from scratch again.

The NoteTaker was to be a "laptop" that could be built in a few years using the (almost) available 16K RAMS (a vast improvement over the 1K RAMS that the ALTO employed). A laptop couldn't use a mouse (which I hated anyway) and a table seemed awkward (not a lot of room and the stylus could flop out of reach when let go), so I came up with an embedded pointing device I called a "tabmouse." It was a relative pointer and had an up sensor so it could be stroked like a mouse and would also stay where you left it, but it felt like a stylus and used a pantograph mechanism that eliminated the annoying hysteresis bias in the x and y directions that made it hard to use a mouse as a pen. I planned to use a multiprocessor architecture of slow but highly integrated chips as originally specified for the Dynabook and wanted a new bytecoded interpreter for a friendlier and simpler system than Smalltalk-72.

Meanwhile Dan was proceeding with his total revamp of Smalltalk and along somewhat similar lines [In 78]. The first major thing that needed to be done was to get rid of the function/class dualism in favor of a completely intensional definition with every piece of code as an intrinisc method. We had wanted that from the beginning, (and most of the code was already written that way). There were a variety of strong desires for a real intheriteance mechanism from Adele and me, from Larry Tesler, who was working on desktop publishing, and from the grad students. Dan had to find a better way than simula's ver rigid compile-time concpetion. It was time to make good on the idea that "everything was an object," which included all the internal "systems" objects like "activation records," etc. We were all agreed that the flexible syntax of the earlier Smalltalks was too flexible, and this level of extensibility was not desireable. All of the extensions we liked used various keyword schemes, so Dan came up with a combination keyword/operator syntax that was very flexible, but allowed the language to be read unambiguously by both humans and the machine. This allowed a FLEX machine-like byte-code compiler and efficient interpreter to be defined that ran up to 180 times as fast as the previous direct interpreter. The OOZE VM system could be modified to handle the new objects and its capactiy was well matched to the ALTO's RAM and disk.

Inheritance

A word about inheritance. Simula-I had neither classes as objects nor inheritance. Simula-67 added the latter as a generalization to the ALGOL-60 <block> structure. This was a great idea. But it did have some drawbacks: minor ones like name clashes in multiple threaded lists (no on uses threaded lists anymore), and major ones like rigidity in the extended type structures, need to qualify types, only a single path of inheritance, and difficulty in adopting to an interactive development system with incremental cmpiling and other needs for instant changes. Then there were a host of problems that were really outside the scope of Simula's goals: having to do with various kinds of modeling and inferencing that were of interest in the world of artifical intelligence. For example, not all useful questions could be answered by following a static chain. Some of them required a kind of "inhertance" or "inferencing" through dynamcically bound "parts" (ie. instance variables). Multiple inerheritance also looked important but the corresponding possible clashes between methods of the same name in different superclases looked difficult to handle, and so forth.

On the other hand, since things can be done with a dynamic language that the difficult with a statically compiled one, I just decided to leave inhertance out as a feature in Smalltalk-72, knowing that we could simulate it back using Smalltalk's LISPlike flexibility. The biggest contributer to these AI ideas was Larry Tesler who used what is now called "slot inheritance" extensively in his various versions of early desktop publishing systems. Nowadays, this would be called a "delgation-style" inheritance scheme [Liberman 84]. Danny Bobrow and Terry Winograd during this period were designing a "frame-based" AI language called KRL which was "object-oriented" and I beleive was influenced by early Smalltalk. It had a kind of multiple inheritance--called perspectives--which permitted an object to play multiple roles in a very clean way. Many of these ideas a few years later went into PIE, an interesting extension of Smalltalk to networks andhigher level descriptions by Ira Goldstein and Bobrow [Goldstein & Bobrow 1980].

By the time Smalltalk-76 cam along, Dan Ingalis had come up with a scheme that was Simula-like in its semantics but could be incrementally changed on the fly to be in accord with our goals of close interaction. I was not completly thrilled with it because it seemed that we needed a better theory about ineritance entirely (and still do). For example, inheritance and instancing (which is a kind of inheritance) muddles both pragmatics (suc as factoring code to save space) and semantics (used for way too many tasks such as: specialization, generalization, speciation, etc.) Alan Borning employed a multiple inheritance scheme in Thinglab [Borning 1977] which was implemented in Smalltalk-76. But no comprehensive and clean multiple inerhitance scheme appeared that was compelling enough to surmount Dan's original Simula-like design.

Meanwhile, the running battle with Xerox continued. there were now about 500 ALTOs linked with Ethernets to each other and to Laserprinter and file servers, that used ALTOs as controllers. I wrote many memos to the Xerox planners trying to get them to make plans that included personal computing as one of their main directions. Here is an example:

A Simple Vision of the Future

A Brief Update Of My 1971 Pendery Paper

In the 1990's there will be millions of personal computers. They will be the size of notebooks of today, have high-resolution flat-screen reflective display.s, wigh less than ten pounds, have ten to twenty times the computing and storage capacity of an Alto. Let's call them Dynabooks.

The purchase price will be about that of a color television set of the era, although most of the machines will be given away by manufacturers who will be marketing the content rather than the container of personal computing.

...

Though the Dynabook will have considerable local storage and will do most computing locally, it will spend a large percentage of its time hooked to various large, global information utilities which will permit communication with others of ideas, data, working models, as well as the daily chit-chat that orgnizations need in order to function. The communications link will be by private and public wire and by packet radio, Dynabooks will also by used as servers in the information utilties. They will have enough power to be entirely shaped by solftware.

The Main Points Of This Vision

  • There need only be a few hardware types to handle almost all of the processing activity of a system.
  • Personal Computers, Communications Link, and Information Utilities are the three critical components of a Xerox future.

...

In other words, the material of a computer system is the computer irself, all of the content and function is fashioned in software.

There are two important guidelines to be drawn from this:

  • Material: If the design and development of the hardware computer material is done as carefully and completely as Xerox's development of special light-sensitve alloys, then only one or two computer designs need to be built... Extra investment in devleopment here will be vastly repaid by simplifying the manufacturing process and providing lower costs through increased volume.
  • Content: Aside from the wonderful generality of being able to continuously shape new content from the same material, software has three important characteristics:
    • the replication time and cost of a content-function is zero
    • the development time and cost for a content-function is high
    • the change time and cost for a content-function is low

Xerox must take these several points seriously if it is to survive and prosper in its new business are of information media. If it does, the company has an excellent chance for several reasons:

  • Xerox has the financial base to cover the large development costs of a small number of very powerful computer-types and a large number of software functions.
  • Xerox has the marketing base tosell these functions on a wide enough scale to garner back to itself an incredible profit.
  • Xerox has working for it an impressively large percentage of the best software designers in the world.

In 1976, Check Thacker designed the ALTO III that would use the new 16k chips and be able to fit on a desktop. It could be marketed for about what the large cumbersome special purpose "word-processors" cost, yet could do so much more. Nevertheless, in august of 1976, Xerox made a fateful decision: not to bring the ALTO III to market. This was a huge blow to many of us--even I, who had never really, really thought of the ALTO as anything but a stepping stone to the "real thing." In 1992, the world market for personal computers and workstations was $90 million--twice as much as the mainframe and mni market, and many times Xerox's 1992 gross. The most successful company of this era--Microsoft--is not a hardware company, but a software company.

The Smalltalk User Interface

I have been asked by several of the reviewers to say more about the development of the "Smalltalk-style" overlapping window user interface since thee are now more than 20 million computers in the workld that use its descendents. A decent history would be as long as this chapter, and none has been written so far. There is a summary of some of the ideas in [Kay 89]--let me add a few more points.

All of the elements eventually use in the Smalltalk user interface were already to be found in the sixties--as different ways to access and invoke the functionality provided by an interactive system. The two major centers of ieads were Lincoln Labs and RAND corp--both ARPA funded. The big shift that consolidated these ideas into a powerful theory and long-lived examples came because the LRG focus was on children. Hence,we were thinking about learning as being one of the main effects we wanted to have happen. EArly on, this led to a 90 degree rotation of the purposed of the user interface from"access to functionality" to "environment in which users learn by doing." This new stance could now respond to the echos of Montessori and Dewey, particularly the former, and got me, on rereading Jerome Bruner, to think beyond the children's curriculum to a "curriculum of the user interface."

The particular aim of LRG was to find the equivalent of writing--that is learning and thinking by doing in a medium--our new "pocket universe." For various reasons I had settled on "iconic programming" as the way to achieve this, drawing on the iconic representations used by many ARPA projects in the sixties. My friend Nicholas Negroponte, an architect, was extremely interested in how environments affected peoples' work and creativity. He was interested in embedding the new computer majic in familiar surroundings. I had quite a bit of theatrical experience in a past life, and remembered Coleridge's adage that "people attend 'bad theatre' hoping to forget, people attend 'good theatre' aching to remember." In other words, it is the ability to evoke the audience's own intelligence and experiences that makes theatre work.

Putting all this together, we want an apparently free environment in which exploration causes desired sequences to happen (Montessori); one that allows kinesthetic, iconic, and symbolic learning--"doing with images makes symbols" (Piaget & Bruner); the user is never trapped in a mode (GRAIL); tha magic is embedded in the familiar (negroponte); and which acts as a magnifying mirror for the user's own intelligence (Coleridge). It would be a great finish to ths story to say that having articulated this we were able to move straightforwardly to the design as we know it today. In fact, the UI design work happened in fits and starts in between feeding Smalltalk itself, designing children's experiments, trying to understand iconic construction, and ust playing around. In spite of this meandering, the context almost forced a good design to turn out anyway. Just about everyone at PARC at this time had opinions about the UI, ours and theirs. It is impossible to give detailed credit for the hundreds of ideas and discussions. However, the consolidation can certainly be attributed to Dan Ingalls, for listening to everyone, contributing original ideas, and constantly building a design for user testing. I had a fiar amount to do with setting the context, invetning overlapping windows, etc., and Adele and I designed most of the experiments. Beyond that, Ted Kaeh;er, and vistor Ron Baecker made highly valuable contrubutions. Dave Smith designed, SmallStar, the protype iconic interface for the Xerox Star product [Smith 83].

Meanwhile, I had gotton Doug Fairbairn interested in the Notetaker. He designed a wonderful "smart bus" that could efficiently handle slow multiple processors and the system looked very promising, even though most of the rest of PARC thought I was nuts to abandon the fast bipolar hw of the ALTO. But I couldn't see that bipolar was ever going to make it into a laptop or Dynabook. On the other hand I hated the 8-bit micros that were just starting to appear, because of the silliness and naivete of their designs--there was no hint that anyone who had ever designed software was involved.

Smalltalk-76

Dan finished the Smalltalk-76 design November, and he, Dave Robson, Ted Kaehler, and Diana Merry, successfully implemented the system from scratch (which included rewriting all of the existing class definition) in just seven months. this was such a wonderful achievement that I was bowled over in spite of my wanting to start over. It was fast, lively, could handle "big" problems, and was great fun. The system consisted of about 50 classes descibed in about 180 pages of source code. This included all of the OS functions, files, printing and other Ethernet services, the window interface, editors, graphics and painting systems, and two new contributions by Larry Tesler, the famous browsers for static methods in the inheritance heirarchy and dynamic contexts for debuging in the runtime environment. In every way it was the consolidation of all of our ideas and yearning about Smalltalk in one integrated package. Al Smalltalks since have resmbled this conception very closely. In many ways, as Tony Hoare once remakred about Algol, Dan's Smalltalk-76 was a great improvement on its successors!

Here are two stylish ST-76 classes written by Dan.

Class new title: 'Window';
  fields: 'frame';
  asFollows!

This is a superclass for presenting windows on the display. It holds control until the stylus is depressed outside. While it holds control, it distributes messages to itself based on user actions.
Scheduling
startup

  [frame contains; stylus =>
    self enter.
    repeat:
      [frame contains: stylus =>
        [keyboard active => [ self keyboard ]
        stylus down => [ self pendown ]]
      self outside => []
      stylus down => [ ^self leave ]]]
  ^false]
Default Event Responses
enter
[self show]
leave
outside
[ ^false]
pendown
keyboard
[ keyboard next. frame flash ]
Image
show

  [frame outline: 2.
titleframe put: self title at: frame origina + title loc.
titleframe complement]
... etc.
Class new title: 'DocWindow';
  subclassOf: Window;
  fields: 'document scrollbar editMenu';
  asFollows!

User events are passed on to the document while the window is active. If the stylus goes out of the window, scrollbar and the editMenu are each given a chance to gain control. Event Responses
enter
[ self show. edit Menu show. scrollbar show ]
leave [ document hideselection. editMenu hide. scrollbar hide ]
outside
  [editMenu startup => []
  scrollbar startup => [self showdoc]
  ^false]
pendown [ document pendown ]
keyboard [ document keyboard ]
Image
show
[ super show. self showDoc ]
showDoc [ document showin; frame at: scrollbar position ]
title [^document title]

Notice, particularly in class Window, how the code is expressed as goals for other objects (or itself) to achieve. The superclass Windpow's main job is to notice events and distribute them as messages to its subclasses. In the example, a document window (a subclass of DocWindow) is going to deal with the effects of user interactions. The Window class will notice that the keyboard is actie and send a message to itself which will be intercepted by the subclass method. If there is no method the character will be thrown away and the window will flash. In this case, it find DocWindow method: keyboard, which tells the held document to check it out.

In January of 1978 Smalltalk-76 had its first real test. CSL had invited the top ten executives of Xerox to PARC for a two day seminar on software, with a special emphasis on complexity and what could be done about it. LRG got asked to give them a hands-on experience in end-user programming so "they could do 'something real' over two 1 1/2 hour sessions." We immediately decided not to teach them Smalltalk-76 (my "burn our disk packs" point in spades), but to create in two months in Smalltalk-76 a rich system especially tailored for adult nonexpert users (Dan's point in trumps). We took our "Simpula" job shop simulation model as a starting point and decided to build a user interface for a generalized job shop simulation tool that the executives could make into specific dynamic simulations that would act out their changing states by animating graphics on the screen. We called it the Smalltalk SimKit. This was a maximum effort and everyone pitched in. Adele became the design leader in spite of the very recent appearence of a new baby. I have a priceless memory of her debugging away on the SimKit while simultaneously nursing Rachell.

There were many interesting problems to be solved. The system itself was straightforward but it had to be completely sealed off from Smalltalk proper, particularly with regard to error messages. Dave Robson came up with a nice scheme (almost an expert system) to capture complaints from the bowels of Smalltalk and translated them into meaningful SimKit terms. There were many user interface details--some workaday, like making new browsers that could only look at the four SimKit classes (Station, Worker, Job, Report), and some more surprising as when we tried it on ten PARC nontechnical adults of about the same age and found that they couldn't read the screen very well. The small fonts our thirtysomething year-old eyes were used to didn't work for those in their 50s. This led to a nice introduction to the system in which the executives were encouraged to customize the screen by choosing amoung different fonts and sizes with the side effect that they learned how to use the mouse unselfconsciously.

On the morning of the "big day" Ted Kaehler decided to make a change in the virtual memory system OOZE to speed it up a little. We all held our breaths, but such was the clarity of the design and the confidence of the implementers that it did work, and the executive hands-on was a howling success. About an hour into the first session one of the VPs (who had written a few programs in FORTRAN 15 years before) finally realized he was programming and mused "so it's finally come to this." Nine out of the ten executives were able to finish a simulation problem that related to their specific interests. One of the most interesting and sophisticated was a PC board production line done by the head of a Xerox owned company using actual figures (that he carried around in his head) to prime a model that could not be solved easily by closed form mathematics--it revealed a seriousl flaw in the dispoition of workers given the line's average probability of manufacturing defects.

Another important system done at this time was Alan Borning's Thinglab [Borning 1979]--the first serious attempt to go beyond Ivan Sutherland's Sketchpad. Alan devised a very nice approach for dealing with constraints that did not require the solver to be omnicient (or able to solve Fermat's last theorem).

Meanwhile, the NoteTaker was getting realler, bigger, and slower. By this time the Western Digital emulation-style chips I hoped to used showed signs of being "diffusion-ware," and did not look like they would really show up. We started looking around for something that we could count on, even if it didn't have a good architecture. In 1978, the best candidate was the Intel 8086, a 16-bit chip (with many unfortunate remnants of the 8008 and 8080), but with (barely) enough capacity to do the job--we would need three of them to make up for the ALTO, one for the interpreter, one for bitmapped graphics, and one for i/o (networking, etc).

Dan had been interested in the NoteTaker all along and wanted to see if the could make a version of Smalltalk-76 that could be the NoteTaker system. IN order for this to happen it would have to run in 256K (the maximum amount of RAM that we had planned for the machine. None of the NOVA-like emulated "machine-code" from the ALTO could be brought over, and it had to fit in memory as well-lthere would only be floppies, no swapping memory existed. This challenge led to some excellent improvements in the system design. Ted Kaehler's system tracer (which could write out new virual memories from old ones) was used to clone Smalltalk-76 into the NoteTaker. The indexed object table (as was used in early Smalltalk-80) first appeared here to simplify object access. An experiment in stacking contexts contiguously was tried: to save space and gain speed. Most of the old machine code was rewritten in Smalltalk and the total machine kernal was reduced to 6K bytes of (the not very strong) 8086 code.

All of the re-engineering had an interesting effect. Through the 8086 was not as good at bitblt as the ALTO (and much of the former machine code to assist graphics was now in Smalltalk), the overall interpreter was about twice as fast as the ALTO version (because not all the Smalltalk byte-code interpreer would fit into the 4k microcode memory on the ALTO). With various kinds of tricks and tuning, graphics display was "largely compensated" (in Dan's words). This was mainly because the ALTO did not have enough microcode memory to take in all of the Smalltalk emulation code--some of it had to be rendered in emulated "NOVA" code which forced two layers of interpretation. In fact, the Notetaker worked extreemely well, though it would have crushed any lap. It had hopped back on the desk, and looked suspiciously like miniCOM (and several computers that would appear a few years later). It really did run on batteries and several of us had the pleasure of taking NoteTaker on a plane and running an object-oriented system with a windowed interface at 35,000 feet.

We eventually built about 10 of the machines, and though in many senses an engineering success, what had to be done to make them had once again squeezed out the real end-users for whom it was originally aimed. If Xerox (and PARC) as a whole had believved in these smaller scale ideas, we could have put much more silicon muscle behind the dreams and successfully built them in the 70's when they were first possible. It was a bitter disappointment to have to get the wrong kind of CPU from Intel and the wrong kind of display from HP because there was not enough corporate will to take advantage of internal technological expertise.

By now it was already 1979, and we found ourselves doing one of our many demos, but this time for a very interested audience: Steve Jobs, JeffRaskin, and other technical people from Apple. They had started a project called Lisa but weren't quite sure what it shouldbe like, until Jeff said to Steve, "You should really come over to PARC and see what they ae doing." Thus, more than eight years after overlapping windows had been invented and more than six years after the ALTO started running, the people who could really do something about the ideas, finally to to see them. The machine used was the Dorado, a very fast "big brother" of the ALTO, whose Smalltalk microcode had been largely written by Bruce Horn, one of our original "Smalltalk kids" who was still only a teen-ager. Larry Tesler gave the main part of the demo with Dan sitting in the copilot's chair and Adele and I watched from the rear. One of the best parts of the demo was when Steve Jobs said he didn't like the blt-style scrolling we were using and asked if we cold do it in a smooth continuous style. In less than a minute Dan found the methods involved, made the (relatively major) changes and scrolling was now continuous! This shocked the visitors, espeicially the programmers among them, as they had never seen a really powerful incremental system before.

Steve tried to get and/or buy the technology from Xerox (which was one of Apple's minority venture captialists), but Xerox would neither part with it nor would come up with the resources to continue to develop it in house by funding a better NoteTaker cum Smalltalk.

IV V VI

Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission.
HOPL-II/4/93/MA, USA
1993 ACM 0-89791-571-2/93/0004/0069...$1.50

The Early History Of Smalltalk by Alan Kay
Abstract TOC Introduction Section I II III IV V VI
For References & Appendixes see pdf or book versions.

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