It is claimed again and again that in the course of the Macintosh’s development, Apple just resorted to the ideas the research laboratory Xerox PARC had hatched before. Fact or Fiction?

Entrance of Xerox PARC in the eighties

In the Untied States, the brand name “Xerox” denotes photocopying just as “Kleenex” stands for tissues or “Scotch tape” for adhesive film. After all, already in 1950, the Xerox Corp. was the world’s first company to actually transfer the “Xerography” invented by the American law student Chester Carlson into a functional product. Carlson received in 1937 a patent for a process that he called ”electrophotography.” On 22 October 1938 followed the premiere in practice: With the help of a metal plate was coated with sulfur and a lamp Chester the lettering ”10-22-38 Astoria” on a wax paper.

The first photocopy

By the end of the sixties, the Xerox management sensed the threat of Japanese companies catching up on Xerox’s technological advantage. Moreover, the Xerox head worried that the “paperless office” might emerge with the following computer generations, in which the Xerox would no longer have a place. Against this background, the Xerox Palo Alto Research Center (PARC) in California was founded in 1971. John Warnock, former researcher in the Xerox PARC and later one of the two founders of Adobe Systems, remembers: “The atmosphere was electric – there was total intellectual freedom. There was no conventional wisdom; almost every idea was up for challenge and got challenged regularly.” Larry Tessler, who later took part in developing the Macintosh and the Newton PDA at Apple, also enjoyed the liberties the PARC provided in the seventies: “The management said go create the new world. We don’t understand it. Here are people who have a lot of ideas and tremendous talent, [are] young, energetic.” The problem, however, was that the company management at the East Coast of the USA did not [care a straw for] the PARC’s research results unless they were directly involved with photocopiers.

Link:

In his TV documentation “Triumph of the Nerds” Robert Cringley is interviewing researchers at the Xerox PARC Within two years, the researchers at the PARC had designed the Alto, which was something like the first personal computer. The Alto did not feature character-oriented graphics, as did all the other computers of that time, but a bit-oriented version instead. A high quality printer could print exactly what the screen displayed.

Xerox Alto

However, this marvelous machine was not freely available on the market. Approximately 1500 units had been produced, 1000 of which Xerox employed in-house; the rest went to universities and public authorities.

Link: An advertising spot for the Xerox Alto taken from Robert Cringley’s TV documentation “Triumph of the Nerds“.

Jef Raskin, who had been charged initially with the Macintosh project at Apple, kept regular contact to the PARC researchers and tried to convince the Apple management to employ a graphical user interface like the Alto contained in the development of the Lisa. Raskin claimed he wanted to introduce Jobs to the PARC, but due to his personal dislike of Raskin, Jobs simply did not agree to respond to the offer. According to Raskin, it was not until Bill Atkinson supported him that Jobs set out for the PARC. Whatever way the contact was actually accomplished, this visit meant a turning point to the life of Steve Jobs; the three technologies that the 24-year-old encountered there were each revolutionary on their own: the first graphical user interface for computers; networked Alto computers; and object-oriented programming.

They showed me really three things. But I was so blinded by the first one I didn’t even really see the other two. One of the things they showed me was object oriented programming – they showed me that but I didn’t even see that. The other one they showed me was a networked computer system… they had over a hundred Alto computers all networked using email etc., etc., I didn’t even see that. I was so blinded by the first thing they showed me, which was the graphical user interface. I thought it was the best thing I’d ever seen in my life. Now remember it was very flawed, what we saw was incomplete, they’d done a bunch of things wrong. But we didn’t know that at the time but still thought they had the germ of the idea was there and they’d done it very well and within you know ten minutes it was obvious to me that all computers would work like this some day.

Adele Goldberg

Jobs decided to realign Apple’s strategy and fully rely on the “graphical user interface” (GUI) he had seen at the Xerox PARC. Adele Goldberg, who had been a researcher at the PARC at that time, already suspected that Jobs’ visit would entail extensive consequences: “He came back, and I almost said ‘asked’ but the truth is ‘demanded,’ that his entire programming team get a demo of the Smalltalk System, and the then head of the science center asked me to give the demo because Steve specifically asked for me to give the demo, and I said ‘no way.’ I had a big argument with these Xerox executives, telling them that they were about to give away the kitchen sink, and I said that I would only do it if I were ordered to do it, cause then, of course, it would be their responsibility, and that’s what they did.”

Bill Atkinson and Larry Tessler the demo for Apple at Xerox PARC” (taken from: Triumph of the Nerds)

Apple bought access to the PARC by means of a stock deal that seemed lucrative to the Xerox managers on the East Coast: They might buy 100,000 Apple stocks for one million dollars. Holding this admission ticket in the hand, Steve Jobs, Apple’s president Mike Scott, Bill Atkinson, and a number of members of the developing team marched up. “I think mostly … what we got in that hour and a half was inspiration and just sort of basically a bolstering of our convictions that a more graphical way to do things would make this business computer more accessible.”

Larry Tesler, who then took part in the demo as an employee of the PARC, had been fascinated by the visitors: “After an hour looking at demos, they understood our technology and what it meant, more than any Xerox executive understood after years of showing it to them.”

The Macintosh team took up the ideas of the PARC, but it also changed numerous operating modes and added countless new features. Accordingly, the Xerox Alto did not imply, for example, menus flapping down from the upper edge of the screen, but operated with some kind of a pop-up window instead. Moreover, the window did not open automatically by double-clicking on a document, but had to be opened manually. During months of painstaking work, Atkinson had written the QuickDraw routine for the Lisa and the Macintosh, which allowed for overlapping windows to be drawn on the computer screen for the first time.

The screen of the Xerox Star

In contrast to the first Mac, the Alto featured no completed desktop metaphor nor ingenious desktop icons such as the trash can, which made it easier to delete files, and not just for computer novices. The historical accomplishments of the Mac team also included the Macintosh Human Interface Guide, which, for instance, when it detected a document in a Macintosh application, determined that it was to be saved using the command “Apple-S.”

As for Xerox, the bitter aftertaste of having missed an historical opportunity remained, particularly due to the fact that parallel to the Apple developers, Bill Gates and his Microsoft crew also went in and out as they pleased. (By the way, they did so without holding an admission ticket comparable to the one Jobs had procured by means of the stock deal.)

“Basically, they were copier heads that just had no clue about a computer or what it could do. And so they just grabbed defeat from the greatest victory in the computer industry. Xerox could have owned the entire computer industry today,” Steve Jobs said in 1996. “Could have been, you know, a company ten times its size. Could have been IBM – could have been the IBM of the nineties. Could have been the Microsoft of the nineties.”
Besides, in the context of the dispute with Apple about the plagiarism accusations around the first Windows versions, Microsoft had pointed out that Apple and Microsoft had both helped themselves generously at XEROX.

In the early ’80s Steve Jobs needed help from Bill Gates: Apple was developing its first Macintosh. Microsoft, which had supplied IBM with the MS-DOS operating system for its PCs, was invited to be the Mac’s first software developer. Early Mac developer Andy Hertzfeld says that when Jobs recruited Microsoft he feared it “might try to copy our ideas into a PC. Steve made Microsoft promise not to ship any software that used a mouse – until at least one year after the first shipment of the Macintosh”.
In 1983, Microsoft sprang a surprise with a new operating system for PCs using an interface like the Mac’s – Windows. Jobs “went ballistic”, demanding an explanation and saying: “I want him in this room by tomorrow afternoon, or else.”
Gates arrived alone to find himself surrounded by 10 Apple employees. “You’re ripping us off,” Jobs shouted.
But Gates looked him in the eye, and said in his squeaky voice, “Well, Steve, I think there’s more than one way of looking at it. I think it’s more like we both had this rich neighbour named Xerox and I broke into his house to steal the TV set and found out that you had already stolen it.”
This episode is described slightly exaggeratedly in the movie “Pirates in the Silicon Valley”:

Apple sued Microsoft in 1988. Six years later a judge threw the case out.

Christoph Dernbach

****************************************************

Book cover: Revolution in The Valley

James Turner from O’Reilly News interviewed Andy Hertzfeld, one of the original designers of the Macintosh and author of the book, Revolution in the Valley: The Insanely Great Story of How the Mac Was Made, which chronicles the efforts to create the Mac. Andy Hertzfeld currently works at Google as a Software Engineer. In this Interview James Turner asked some questions about Xerox PARC and the development of the Mac:

JT: In your book you allude to Xerox as being, to Bill Gates, the rich uncle that both Apple and Microsoft stole from. What was the relationship like with PARC when you were developing the Mac and how did the Xerox researchers feel about the Mac?

AH: Well, we had no formal relationship with PARC while we were developing the Mac. We got a single demo before the Mac project got off the ground, when the LISA project, that sort of cousin or bigger brother of the Mac, was in development. And so from that one demo we were already pointed in that direction but I would say that Xerox PARC demo galvanized and reinforced our strong opinion that the graphic user-interface was the way to go. And then the influence of PARC was strong in the project, but not through a formal relationship with PARC; more through PARC people getting wind of what we were doing and coming to work at Apple. The very first one was Tom Malloy on the LISA project. He was sort of a disciple of Charles Simonyi–I write about that a little bit in my book. He was one of the original LISA people who came to Apple in 1978. But later, Larry Tessler was a really key figure coming to the LISA team in the summer of 1980 from Xerox PARC and eventually, mostly after the original Mac shipped, there were a dozen or more. Another person I have to mention is Bruce Horn who started working at Xerox PARC when he was 14 years old; he was one of those kids they picked from a Palo Alto High School to teach Smalltalk to and he was one of the four or five key Macintosh developers. And of course he was steeped in all of the PARC values and through Bruce, a lot of them made it into the Macintosh.

JT: Was there any feeling among the Apple engineers that any – guilt is probably too strong a word, but feeling like you know Xerox had these great ideas. I guess Xerox really let them go to waste but–

AH: Oh there was nothing like that; Steve Jobs has a good quote. It’s actually a Picasso quote that he often cites; he cited it at one of our retreats which was sort of good artists copy; great artists steal. And what that means is that when you’re passionate about what you’re doing you’ll take ideas from anywhere and with no guilt. You want to make the best possible thing and that was our mentality.

JT: I have to say I actually worked for Xerox AI Systems in 1986 and it was kind of frustrating because they really had the mentality there that if you couldn’t sell paper and toner for [them] they weren’t interested.

AH: Oh sure. Xerox in a well-documented fashion – they had at least the possibility of having the world at their feet there with the work that Alan Kay and his team did. But yeah; they completely blew it and most of the best PARC people were really frustrated by the Xerox management. There’s no doubt of that; that’s one of the reasons why Steve Jobs is great. You had someone leading the company who could relate to the customers and appreciate things.

Few computer enthusiasts or professionals can look at the machines of today without wondering: What’s next?

The Alto: a Personal Computer

In 1972, Xerox Corporation decided to produce a personal computer to be used for research. The result was the Alto computer, whose name comes from the Xerox Palo Alto Research Center where it was developed. The Alto was the result of a joint effort by Ed McCreight, Chuck Thacker, Butler Lampson, Bob Sproull, and Dave Boggs, who were attempting to make a device that was small enough to fit in an office comfortably, but powerful enough to support a reliable, high-quality operating system and graphics display. Their goal was to provide each user with a personal computing facility capable of meeting all individual needs and a communications facility that would allow users to share information easily.

In 1978, Xerox donated a total of fifty Altos to Stanford, Carnegie-Mellon, and MIT (Massachusetts Institute of Technology). These machines were quickly assimilated into the research community and rapidly became the standard against which other personal computers were judged.

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 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.

The Alto consists of four major parts: the graphics display, the keyboard, the graphics mouse, and the disk storage/processor box. Each Alto is housed in a beautifully formed, textured beige metal cabinet that hints at its $32,000 price tag. With the exception of the disk storage/processor box, everything is designed to sit on a desk or tabletop.

The Graphics Display

The graphics display is the most striking feature of the Alto. It looks somewhat like a television screen that has been turned sideways (see photo 1). It is a raster-scan display, and the physical dimensions of the screen are 8 inches (horizontal) by 10 inches (vertical). The black-and-white display allows the user to address an area 808 pixels (picture elements) vertically by 606 pixels horizontally. This results in resolution of about 80 points per inch.

The method of display used is called bit-mapped raster scan. This means that every point on the display is addressable as a bit in memory. Although this method can take up a great deal of memory, it has the advantage of making the display veryfast. Bit mapping also provides the user with a convenient method of screen access and the ability to easily look at the current contents of the screen.

In terms of displaying text, the screen can hold 60 lines of 90 characters (assuming the characters are equivalent to the typical 7 by 9 dot character commonly found on most video terminals). Character generation is not done in hardware on the Alto. A character set may be created by a user and displayed on the screen. Mixed fonts are allowed so that text of various sizes and shapes may be simultaneously displayed on the screen.

The Keyboard

The Graphics Mouse

Movement is detected by the motion of one of the ball bearings. The mouse reports changes in position to the Alto. From this, a cursor on the Alto display can be positioned. The physical position of the mouse on the table is unimportant, since only the change in position is reported. The mouse graphics interface is considerably more flexible and comfortable than a bit pad, joystick, or trackball. Many Alto programs can be controlled with the mo
use alone, independent of a keyboard.

Disk Storage/Processor Box

The processor and disk storage for the Alto are contained in a rack about the size of a waist-high filing cabinet. Each Alto has two 3-megabyte disk drives. The drives themselves resemble small pizza ovens and are often referred to in this manner.

The “brain” of the Alto is a 16-bit custom-made processor intended to resemble the Data General Nova 1220. The processor is made entirely of small- to medium-scale TTL (transistor-transistor logic) ICs (integrated circuits). The processor operates at a speed of approximately 400,000 instructions per second. Each Alto has an address space of 64 K 16-bit words, including the graphics bitmap. By using a technique called bank selection, the Alto may expand its available memory in 64 K-word increments up to 256 K words. An Alto with 256 K words is known as a wide-bodied Alto.

Quite a bit of the magic of the Alto is performed at the microcode level. The Alto can run up to sixteen tasks concurrently, and all of the scheduling and I/O (input/output) for this multiprocessing is done in microcode. The user has direct control over only one task, however. The user task is the lowest priority and must, if necessary, relinquish processing cycles to the other tasks that control the display, disks, keyboard and mouse I/O, and Ethernet connections. The user has direct control over the microcode and may rewrite it according to individual taste.

The Software

The Alto has the interesting property of using software (often microcode) to perform many tasks, such as keyboard encoding and character generation, that are typically done in hardware. This approach leaves the Alto with an occasionally cumbersome but highly flexible architecture.

Each Alto has a ROM (read-only memory) that contains just enough software to “bootstrap” an Alto into the local network (see textbox on this page). By keeping a bootstrap program in ROM, the user will always have a “safety net” to fall back on in case some other portion of the system software is not working. All of the Alto software can be retrieved from across the network.

The Alto Operating System (OS), a program which provides a set of basic facilities for control and communication with the Alto, is written in BCPL, a language very similar to C. Most programs, BCPL or otherwise, run under the direction of the Alto OS. Since the address space of an Alto is small, a technique called a “Junta” is used to permit BCPL programs to shed unwanted sections of the Alto OS during execution. If those portions are needed later, they may be restored by performing a “Counterjunta.”

The Alto has a highly flexible and rugged file system. Unlike many file systems (eg: Digital Research’s CP/M or Radio Shack’s TRSDOS) that limit names to six or eight characters with a three-character extension, the Alto file system permits file names of up to thirty-one characters in length. When a file name is entered for the first time, the file name is stored exactly as typed, even with regard to upper- and lowercase. Since the file names may be very long, this permits a programmer to use upper- and lowercase to improve readability. LongFileName.BigExtension is much easier on the eyes than LONGFILENAME.BIGEXTENSION. After the creationof a file, case is ignored when the user is speaking about the file, so either of the two names in the previous examples, as well as longfilename.bigextension, would be valid.

Alto files are divided into pages. Each page contains a small header that describes the current page, tells what file the page belongs to, and points to the places on the disk that contain the next and previous pages for the same file. This makes the file system almost indestructible. A program called Scavenger can automatically rebuild a broken file system.

BCPL and Mesa are the system languages for the Alto, which means that the system utilities and many applications programs are written in them. Other languages are available on the Alto, however. Much of the research work done on the Alto at Xerox is written in Smalltalk, an object-oriented language that is both easy to learn and highly powerful (see the special August 1981 BYTE issueon the Smalltalk language). Another supported language is LISP, a list-processing language that is very popular in the artificial intelligence research community.

Using the Screen

r> Photo 5d: Examples of Alto software: Directory from the Neptune directory editor. The file names in black have been selected for further operations such as printing or erasure. The cursor is displayed as a cross in a circle. A system with the advanced graphics capability of the Alto will make extensive use of those facilities. The screen may be broken up into windows, and each window may be accessed in a different manner, ifdesired. Many Alto programs use only the mouse and screen windows for program control. For instance, the Neptune program is used for managing the contents of the Alto’s local disks (see photo 5d). A file may be deleted simply by touching the file name with the cursor, then touching the Delete spot on the screen with the cursor. As the cursor enters a new window, it may change shape, perhaps appearing as an arrow in one window and a paintbrush in another.

Photo 5e: Examples of Alto software: Bravo’s ability to change fonts (there are hundreds of fonts for the Alton, from Gothic to Elvish Runes; the central paragraph in this display has been changed to Greek). The document in the bottom window has to been converted to the form shown in the top window. Since the Alto is used extensively for research in the office automation field, a good text editor is an obvious requirement. Bravo is a text editor and formatter widely used on the Alto. In the tradition of screen-oriented editors, the current state the user’s file is always shown on the screen. Bravo is controlled partly by keyboard commands and partly by mouse commands. It allows a user to open windows into one or more files. Text may be added or deleted by pointing at the desired location on the screen (see photo 5e) with the mouse cursor, and giving a command via the keyboard or mouse. Bravo supports many different fonts and allows the user to change easily from one font to the next. In addition, Bravo remembers the changes that have been made to a document and allows the user to reverse any or all changes.

Bravo allows the user to edit and format text, but often a person may wish to include illustrations in a document. To do this, a program called Draw is used. Draw is an interactive sketch-pad program that provides a variety of tools for creating and manipulating pictures made from lines, curves, and text. Draw divides the screen into a number of windows (see photo 6). The left side of the screen contains a menu of commands and a variety of brushstrokes that can be selected. The top of the screen contains an area for text commands and messages from the program. The middle of the screen is the picture workspace. Curves can be drawn by moving the cursor directly, or by selecting several points and allowing Draw to mathematically fit a curve to those points. Once an object is defined, it can be repainted using a number of brushstrokes. Since this is very similar to the techniques used by artists and calligraphers, quite a bit of artistic expression is possible. An object can be duplicated, rotated, stretched, or shrunk, by means of a small set of commands and mouse gestures.

The Network

Photo 6a: Use of the Draw program: Points are placed with the cursor, and curves and lines are filled in by the program. Photo 6b: Use of the Draw program: Lines may be “painted” with a variety of “brushstrokes” (the cursor has changed to a small paintbrush). Photo 6c: Use of the Draw program: Texture is given to the lines; dotted lines are created with the scissors cursor. Photo 6d: Use of the Draw program: Picture may be mathematically manipulated; a new figure may be created by reversing, tilting, or stretching a copy of the original. Each Alto is assigned an Ethernet address that identifies it uniquely onthe network. A typical Ethernet address might be 50#100, which is meaningless to most people. To permit an easily remembered distinction between Altos, each is assigned a name. For instance, the Altos at Stanford are named after rivers and mountains in California State parks; Altos at CMU are named after jewels, and Altos at Xerox are named after people. This leads to such interesting names as Cypress, Turquoise, or Machiavelli, which are considerably easier to remember than 50#100.

Alto networks do not consist entirely of Altos. Several other devices are connected to the Ethernet network. One type is called a server. Servers are userless Altos that are dedicated to some specific function. A server might be connected to a printer. Thus, printing a file would actually consist of sending the proper messages to a Printing Server. One common type of server is a File Server. These machines support extra-large disks and are repositories for programs and files that are too large or too infrequently accessed to make storage on individual machines worthwhile. The Stanford File Server is named Lassen.

Due to the design of the network and the Altos, a new Alto can be wheeled in, plugged into the network medium (standard coaxial cable), and, with a blank disk pack fresh from the factory, become entirely functional with a full set of software in a matter of minutes. An Alto can also be disconnected, moved to another port in the coaxial cable, and reconnected without affecting either the performance of the network or the Alto.

Photo 7: The multiplayer Trek program. This game is played entirely under mouse control. The lower portion of the screen shows a short-range sensor scan; above is the long-range display, and navigation and weapons controls. Several programs exist that take advantage of the distributed processing capabilities inherent in the Ethernet network. Of all of them, the most enjoyable are the games. Trek is a multiplayer “spacewar” game that is controlled primarily by the mouse (see photo 7). Mazewar is a multi-player romp through a realistic labyrinth (see photo 8). The unique feature of these games is that large numbers of users can join or leave the game as they please without affecting the play of the others. Since all the Altos can listen to the same packet (block information on the Ethernet) at once, the game program is never running on any single coordinating machine. Instead, it is running independently on every participating Alto.

The Future

all>Photo 8: The multiplayer Mazewar game. The eye represents the persona of an opponent. Any Alto on the net can join or leave the game at any time. A stand-alone Alto is usable, but the best configuration is a group of Altos connected by an Ethernet system. Since the Ethernet system is a local network, a special device called a gateway was developed to allow local Ethernet networks to speak to other Ethernet networks or packet networks of other types. Many companies are researching network schemes that would allow packet transmission across cable-television lines. Since these cables are currently installed in many homes and buildings, it is not difficult to imagine a city with an “information grid,” analogous to the electric-power grid that exists today. Combined with an electronic mail system (a prototype called Laurel is used on Altos today) the possibilities are staggering.

The Alto has been around for several years. As research tools go, it is covered with moss and gathering dust. But new products will be appearing on the market based on the expertise gained in producing and using the Alto. The next few years should show a dramatic increase in the quality of personal computing and the ability to interconnect personal computers. And the Alto is one of the first personal computers that satisfies the needs of the computer scientist as well as the secretary or businessman.

by Thomas A Wadlow; 5157 Norma Way Apt 226, Livermore CA 94550 Acknowledgments

I would like to thank Dr Brian Reid and Mark Roberts of Stanford University for their time and helpful comments; also Sandy Lanzarotta of Xerox and Cindy Pavlinac for their help and support.

References

1. Lampson, B W and E Taft. Alto User’s Handbook, 1979.
2. Metcalfe, R M and D R Boggs. “Ethernet: Distributed Packet Switching For Local Computer Networks.” Communications of the ACM 19,7, July 1976, pages 395 through 404.
3. Shoch, J F and J A Hupp. “Measured Performance of an Ethernet Local Network.” Communications of the ACM 23,12, December 1980, pages 711 through 721.
4. Thacker, C P, E M McCreight, B W Lampson, R F Sproull, and D R Boggs. Alto: A Personal Computer. Tech Rep CSL-79-11. Palo Alto CA: Xerox Palo Alto Research Center, August 1979. (To appear in Computer Structures: Readings and Examples, Second Edition. Siewiorek, Bell, and Newell, editors.)

]]> http://www.mac-history.net/xerox-parc/2008-07-19/computer-history-xerox-alto/feed 0 http://www.mac-history.net/computer-history/2008-06-02/computer-history-xerox-alto-a-personal-computer http://www.mac-history.net/computer-history/2008-06-02/computer-history-xerox-alto-a-personal-computer#comments Mon, 02 Jun 2008 05:01:11 +0000 Christoph Dernbach http://www.mac-history.net/?p=498

In the mid-1970s, the personal-computer market blossomed with the introduction of the Altair 8800. Each year since has brought us personal computers with more power, faster execution, larger memory, and better mass storage.

Reprinted from Byte, issue 9/1981, pp. 58-68. Source: GUIdebook

Few computer enthusiasts or professionals can look at the machines of today without wondering: What’s next?

The Alto: a Personal Computer

In 1972, Xerox Corporation decided to produce a personal computer to be used for research. The result was the Alto computer, whose name comes from the Xerox Palo Alto Research Center where it was developed. The Alto was the result of a joint effort by Ed McCreight, Chuck Thacker, Butler Lampson, Bob Sproull, and Dave Boggs, who were attempting to make a device that was small enough to fit in an office comfortably, but powerful enough to support a reliable, high-quality operating system and graphics display. Their goal was to provide each user with a personal computing facility capable of meeting all individual needs and a communications facility that would allow users to share information easily.

In 1978, Xerox donated a total of fifty Altos to Stanford, Carnegie-Mellon, and MIT (Massachusetts Institute of Technology). These machines were quickly assimilated into the research community and rapidly became the standard against which other personal computers were judged.

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 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.

Photo 1: Two of the Xerox Alto personal computers. Each Alto processor is made of medium- and small-scale TTL integrated circuits, and is mounted in a rack beneath two 3-megabyte hard-disk drives. Note that the video displays are taller than they are wide and are similar to a page of paper, rather than standard television screen.

The Hardware

The Alto consists of four major parts: the graphics display, the keyboard, the graphics mouse, and the disk storage/processor box. Each Alto is housed in a beautifully formed, textured beige metal cabinet that hints at its $32,000 price tag. With the exception of the disk storage/processor box, everything is designed to sit on a desk or tabletop.

The Graphics Display

The graphics display is the most striking feature of the Alto. It looks somewhat like a television screen that has been turned sideways (see photo 1). It is a raster-scan display, and the physical dimensions of the screen are 8 inches (horizontal) by 10 inches (vertical). The black-and-white display allows the user to address an area 808 pixels (picture elements) vertically by 606 pixels horizontally. This results in resolution of about 80 points per inch.

The method of display used is called bit-mapped raster scan. This means that every point on the display is addressable as a bit in memory. Although this method can take up a great deal of memory, it has the advantage of making the display veryfast. Bit mapping also provides the user with a convenient method of screen access and the ability to easily look at the current contents of the screen.

In terms of displaying text, the screen can hold 60 lines of 90 characters (assuming the characters are equivalent to the typical 7 by 9 dot character commonly found on most video terminals). Character generation is not done in hardware on the Alto. A character set may be created by a user and displayed on the screen. Mixed fonts are allowed so that text of various sizes and shapes may be simultaneously displayed on the screen.

Photo 2: Display from the keyboard-test program. The Alto keyboard has a separate signal line for each key and can thus tell when any number of keys are being pressed simultaneously. In the display, the black keys are being held down. The small square above the keyboard represents the mouse (see photo 4); one mouse key is also pressed.

Since each dot on the display corresponds to only one bit in memory, there is no facility for grays or intermediate intensities. Due to the large number of points per inch, however, various combinations of points can be displayed to form a “texture” that gives the impression of varying shades of gray. This is exactly the same method used to reproduce pictures in a newspaper.

The Keyboard

Photo 3: The Pinball game. Flippers are actuated by the two shift keys; an Alto port can be connected to a speaker to provide bells and buzzer sounds.

Superficially, the Alto keyboard resembles a typical typewriter keyboard with the addition of a few special keys. The keyboard is detachable, and quite comfortable for typing. It has the unique property of being entirely unencoded. Each key has its own signal line in the keyboard interface, which allows a program to take advantage of the possibility of “chord” commands, where the user holds down one or more keys. For example, Shift-Control-E is as easy for the Alto to read as A-B-C (see photo 2). Another advantage is the ability to determine how long a key has been held down. For example, the pinball game program in photo 3 determines the force of a shot by measuring how long a key is held down on the keyboard. There is, of course, software to allow a program to read the keyboard in the typical manner.

The Graphics Mouse

Photo 4: The mouse input device. The operator uses the mouse to control cursor placement on the screen; it detects its own change in position (a joystick relies on absolute position) as the operator rolls it around on a piece of soft plastic. The mouse also has three buttons, called red, yellow and blue.

The mouse is a small box with three buttons on the top and several ball bearings on the bottom. A slender cable connects the mouse to the Alto keyboard (see photo 4). The buttons are named red, yellow, and blue, although the physical buttons are all black. The mouse is typically held in the user’s right hand and rolled along the table on a soft piece of plastic that provides traction for the ball bearings.

Movement is detected by the motion of one of the ball bearings. The mouse reports changes in position to the Alto. From this, a cursor on the Alto display can be positioned. The physical position of the mouse on the table is unimportant, since only the change in position is reported. The mouse graphics interface is considerably more flexible and comfortable than a bit pad, joystick, or trackball. Many Alto programs can be controlled with the mouse alone, independent of a keyboard.

Disk Storage/Processor Box

The processor and disk storage for the Alto are contained in a rack about the size of a waist-high filing cabinet. Each Alto has two 3-megabyte disk drives. The drives themselves resemble small pizza ovens and are often referred to in this manner.

The “brain” of the Alto is a 16-bit custom-made processor intended to resemble the Data General Nova 1220. The processor is made entirely of small- to medium-scale TTL (transistor-transistor logic) ICs (integrated circuits). The processor operates at a speed of approximately 400,000 instructions per second. Each Alto has an address space of 64 K 16-bit words, including the graphics bitmap. By using a technique called bank selection, the Alto may expand its available memory in 64 K-word increments up to 256 K words. An Alto with 256 K words is known as a wide-bodied Alto.

Quite a bit of the magic of the Alto is performed at the microcode level. The Alto can run up to sixteen tasks concurrently, and all of the scheduling and I/O (input/output) for this multiprocessing is done in microcode. The user has direct control over only one task, however. The user task is the lowest priority and must, if necessary, relinquish processing cycles to the other tasks that control the display, disks, keyboard and mouse I/O, and Ethernet connections. The user has direct control over the microcode and may rewrite it according to individual taste.

The Software

The Alto has the interesting property of using software (often microcode) to perform many tasks, such as keyboard encoding and character generation, that are typically done in hardware. This approach leaves the Alto with an occasionally cumbersome but highly flexible architecture.

Each Alto has a ROM (read-only memory) that contains just enough software to “bootstrap” an Alto into the local network (see textbox on this page). By keeping a bootstrap program in ROM, the user will always have a “safety net” to fall back on in case some other portion of the system software is not working. All of the Alto software can be retrieved from across the network.

The Alto Operating System (OS), a program which provides a set of basic facilities for control and communication with the Alto, is written in BCPL, a language very similar to C. Most programs, BCPL or otherwise, run under the direction of the Alto OS. Since the address space of an Alto is small, a technique called a “Junta” is used to permit BCPL programs to shed unwanted sections of the Alto OS during execution. If those portions are needed later, they may be restored by performing a “Counterjunta.”

Photo 5a: Examples of Alto software: Display of the Alto Executive, with an example of star and question-mark notation.

One BCPL program that runs on top of the operating system is called the Alto Executive (see photo 5a). This program speaks to the user directly and makes facilities available for file manipulation and program execution. An interesting feature of the Executive is that of escape expansion and file-name completion. Typing a partial file or program name followed by an escape, in the same fashion that an ESC (escape) or ALT (alternate mode) might be sent from an ASCII (American Standard Code for Information Interchange) terminal, causes the Executive to complete the typing of the name on the screen. Thisallows a programmer to name a file in a descriptive manner (such as Gatewaylnformation.press), rather than typing in a long name. The Executive program will recognize it as soon as it has read enough characters to determine the file uniquely. By typing a question mark instead of an escape, the Executive will list all file names that are valid matches for the string typed thus far.

The Alto has a highly flexible and rugged file system. Unlike many file systems (eg: Digital Research’s CP/M or Radio Shack’s TRSDOS) that limit names to six or eight characters with a three-character extension, the Alto file system permits file names of up to thirty-one characters in length. When a file name is entered for the first time, the file name is stored exactly as typed, even with regard to upper- and lowercase. Since the file names may be very long, this permits a programmer to use upper- and lowercase to improve readability. LongFileName.BigExtension is much easier on the eyes than LONGFILENAME.BIGEXTENSION. After the creationof a file, case is ignored when the user is speaking about the file, so either of the two names in the previous examples, as well as longfilename.bigextension, would be valid.

Alto files are divided into pages. Each page contains a small header that describes the current page, tells what file the page belongs to, and points to the places on the disk that contain the next and previous pages for the same file. This makes the file system almost indestructible. A program called Scavenger can automatically rebuild a broken file system.

Photo 5b: Examples of Alto software: NetExecutive (similar to the Alto Executive, but it allows access to resources on the Ethernet.

Of course, no Alto is an island, so software is needed to deal with the Ethernet network. Some of this software appears in the form of the NetExecutive (see photo 5b) and FTP (file-transfer program). The NetExecis a program that appears to be very similar to the Alto Executive, but it loads programs from across the network rather than from the local disk. This means that a user need not keep infrequently used or large programs locally. Instead, these programs can be loaded through the network (at an apparent speed of approximately 800,000 bits per second) only when needed. FTP performs similar feats of file manipulation, but in a considerably more flexible manner.

Photo 5c: Examples of Alto software: Typical Mesa program being edited by Bravo; note the different typefonts used in the program listing.

Although a great deal of software written for the Alto is in BCPL, there is a new contender for software development called Mesa. Mesa is a Pascal-like language that is incompatible with BCPL because of differences in their respective microcodes. Mesa is expected to be the programming language for the successors of the Alto (see photo 5c).

BCPL and Mesa are the system languages for the Alto, which means that the system utilities and many applications programs are written in them. Other languages are available on the Alto, however. Much of the research work done on the Alto at Xerox is written in Smalltalk, an object-oriented language that is both easy to learn and highly powerful (see the special August 1981 BYTE issueon the Smalltalk language). Another supported language is LISP, a list-processing language that is very popular in the artificial intelligence research community.

Using the Screen

Photo 5d: Examples of Alto software: Directory from the Neptune directory editor. The file names in black have been selected for further operations such as printing or erasure. The cursor is displayed as a cross in a circle.

A system with the advanced graphics capability of the Alto will make extensive use of those facilities. The screen may be broken up into windows, and each window may be accessed in a different manner, ifdesired. Many Alto programs use only the mouse and screen windows for program control. For instance, the Neptune program is used for managing the contents of the Alto’s local disks (see photo 5d). A file may be deleted simply by touching the file name with the cursor, then touching the Delete spot on the screen with the cursor. As the cursor enters a new window, it may change shape, perhaps appearing as an arrow in one window and a paintbrush in another.

Photo 5e: Examples of Alto software: Bravo’s ability to change fonts (there are hundreds of fonts for the Alton, from Gothic to Elvish Runes; the central paragraph in this display has been changed to Greek). The document in the bottom window has to been converted to the form shown in the top window.

Since the Alto is used extensively for research in the office automation field, a good text editor is an obvious requirement. Bravo is a text editor and formatter widely used on the Alto. In the tradition of screen-oriented editors, the current state the user’s file is always shown on the screen. Bravo is controlled partly by keyboard commands and partly by mouse commands. It allows a user to open windows into one or more files. Text may be added or deleted by pointing at the desired location on the screen (see photo 5e) with the mouse cursor, and giving a command via the keyboard or mouse. Bravo supports many different fonts and allows the user to change easily from one font to the next. In addition, Bravo remembers the changes that have been made to a document and allows the user to reverse any or all changes.

Bravo allows the user to edit and format text, but often a person may wish to include illustrations in a document. To do this, a program called Draw is used. Draw is an interactive sketch-pad program that provides a variety of tools for creating and manipulating pictures made from lines, curves, and text. Draw divides the screen into a number of windows (see photo 6). The left side of the screen contains a menu of commands and a variety of brushstrokes that can be selected. The top of the screen contains an area for text commands and messages from the program. The middle of the screen is the picture workspace. Curves can be drawn by moving the cursor directly, or by selecting several points and allowing Draw to mathematically fit a curve to those points. Once an object is defined, it can be repainted using a number of brushstrokes. Since this is very similar to the techniques used by artists and calligraphers, quite a bit of artistic expression is possible. An object can be duplicated, rotated, stretched, or shrunk, by means of a small set of commands and mouse gestures.

The Network

Photo 6a: Use of the Draw program: Points are placed with the cursor, and curves and lines are filled in by the program.

Photo 6b: Use of the Draw program: Lines may be “painted” with a variety of “brushstrokes” (the cursor has changed to a small paintbrush).

Photo 6c: Use of the Draw program: Texture is given to the lines; dotted lines are created with the scissors cursor.

Photo 6d: Use of the Draw program: Picture may be mathematically manipulated; a new figure may be created by reversing, tilting, or stretching a copy of the original.

Each Alto is assigned an Ethernet address that identifies it uniquely onthe network. A typical Ethernet address might be 50#100, which is meaningless to most people. To permit an easily remembered distinction between Altos, each is assigned a name. For instance, the Altos at Stanford are named after rivers and mountains in California State parks; Altos at CMU are named after jewels, and Altos at Xerox are named after people. This leads to such interesting names as Cypress, Turquoise, or Machiavelli, which are considerably easier to remember than 50#100.

Alto networks do not consist entirely of Altos. Several other devices are connected to the Ethernet network. One type is called a server. Servers are userless Altos that are dedicated to some specific function. A server might be connected to a printer. Thus, printing a file would actually consist of sending the proper messages to a Printing Server. One common type of server is a File Server. These machines support extra-large disks and are repositories for programs and files that are too large or too infrequently accessed to make storage on individual machines worthwhile. The Stanford File Server is named Lassen.

Due to the design of the network and the Altos, a new Alto can be wheeled in, plugged into the network medium (standard coaxial cable), and, with a blank disk pack fresh from the factory, become entirely functional with a full set of software in a matter of minutes. An Alto can also be disconnected, moved to another port in the coaxial cable, and reconnected without affecting either the performance of the network or the Alto.

Photo 7: The multiplayer Trek program. This game is played entirely under mouse control. The lower portion of the screen shows a short-range sensor scan; above is the long-range display, and navigation and weapons controls.

Several programs exist that take advantage of the distributed processing capabilities inherent in the Ethernet network. Of all of them, the most enjoyable are the games. Trek is a multiplayer “spacewar” game that is controlled primarily by the mouse (see photo 7). Mazewar is a multi-player romp through a realistic labyrinth (see photo 8). The unique feature of these games is that large numbers of users can join or leave the game as they please without affecting the play of the others. Since all the Altos can listen to the same packet (block information on the Ethernet) at once, the game program is never running on any single coordinating machine. Instead, it is running independently on every participating Alto.

The Future

Photo 8: The multiplayer Mazewar game. The eye represents the persona of an opponent. Any Alto on the net can join or leave the game at any time.

A stand-alone Alto is usable, but the best configuration is a group of Altos connected by an Ethernet system. Since the Ethernet system is a local network, a special device called a gateway was developed to allow local Ethernet networks to speak to other Ethernet networks or packet networks of other types. Many companies are researching network schemes that would allow packet transmission across cable-television lines. Since these cables are currently installed in many homes and buildings, it is not difficult to imagine a city with an “information grid,” analogous to the electric-power grid that exists today. Combined with an electronic mail system (a prototype called Laurel is used on Altos today) the possibilities are staggering.

The Alto has been around for several years. As research tools go, it is covered with moss and gathering dust. But new products will be appearing on the market based on the expertise gained in producing and using the Alto. The next few years should show a dramatic increase in the quality of personal computing and the ability to interconnect personal computers. And the Alto is one of the first personal computers that satisfies the needs of the computer scientist as well as the secretary or businessman.

by Thomas A Wadlow; 5157 Norma Way Apt 226, Livermore CA 94550

Acknowledgments

I would like to thank Dr Brian Reid and Mark Roberts of Stanford University for their time and helpful comments; also Sandy Lanzarotta of Xerox and Cindy Pavlinac for their help and support.

References

1. Lampson, B W and E Taft. Alto User’s Handbook, 1979.
2. Metcalfe, R M and D R Boggs. “Ethernet: Distributed Packet Switching For Local Computer Networks.” Communications of the ACM 19,7, July 1976, pages 395 through 404.
3. Shoch, J F and J A Hupp. “Measured Performance of an Ethernet Local Network.” Communications of the ACM 23,12, December 1980, pages 711 through 721.
4. Thacker, C P, E M McCreight, B W Lampson, R F Sproull, and D R Boggs. Alto: A Personal Computer. Tech Rep CSL-79-11. Palo Alto CA: Xerox Palo Alto Research Center, August 1979. (To appear in Computer Structures: Readings and Examples, Second Edition. Siewiorek, Bell, and Newell, editors.)

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