view additional pages

Video

COMPUTERS AND VIDEO appear to offer an endless variety of combinations, as this month’s cover by Robert Tinney depicts. With an increase in higher-power communication satellites that require smaller, less-expensive user antennas and electronics, and with the melding of television receivers and microprocessors, we might look ahead to the day when worldwide person-to-person visual as well as aural communication is based on personal computers and not on a direct descendant of Mr. Bell’s original invention. “Bulletin Boards in Space.” described by John Markoff in the May BYTE West Coast column (page 88), may give way to worldwide electronic conferencing and conventioning by adding television cameras to the growing list of common personal computer user options.

Many videotex, work-alike, and other interactive cable-television-based systems already exist. With the proliferation of coaxial-cable interconnection and its high-speed data-transmission capabilities, more and more homes and businesses could be linked via computer-controlled video instead of the restricted-bandwidth, audio-frequency-based systems now in use.

Shopping via computer is already a reality in some areas. With television- or presentation-level graphics, perhaps complicated and expensive encoding schemes could become unnecessary because you might be able to view the person to whom your message is directed. And as Rich Malloy, our product-review editor, stated in the July 1983 BYTE in his introduction to the Videotex theme, the printing presses might stop and BYTE could be delivered to you electronically.

Though with us for over a generation, until recently hardware costs made computer and video interactivity limited and expensive. In recent years, dramatic advances in digital electronics and large-scale integration (LSI) have made personal computers, videocassette recorders (VCRs), and videodiscs available to anyone with a down-to-earth application or interest in learning. In this issue, we present articles on a wide range of topics related to computers and video.

Peter R. Cook’s article, “Electronic Encyclopedias.” explores something that all of the major encyclopedia publishers have talked about for several years: how to develop an “intelligent encyclopedia” that uses natural means of accessing and using knowledge. Included with this article is contributing editor Mark Dahmke’s look at “An Ideal Video Peripheral,” a glimpse at how personal computers and videodiscs might communicate more efficiently.

In ‘”televisions as Monitors,” Ken Coach describes some of the characteristics common to the new generation of television receivers that can double as microcomputer video monitors.

If you already have an inexpensive VCR with limited or no programming capabilities or are considering purchasing one. Cy Tymony’s “Computer Control of a Video Recorder” should be particulary interesting. This construction project enables you to use your micro as a programmable control center for your VCR.

Stan Jarvis’s “Videodiscs and Computers” takes a look at the videodisc industry, its evolution. and the myriad of companies and equipment facing personal computer owners.

As an example of what you can do with a CAV (frame-addressable) videodisc, Rod Daynes and Steve Holder designed a game around a generic version in “Controlling Videodiscs with Micros.” They used the videodisc support commands available in the Sony SMC-70 computer.

—Gene Smarte. Managing Editor

ELECTRONIC ENCYCLOPEDIAS

by Peter R. Cook

Interactive video technologies help explore “the realm of worthwhile knowledge”.

Peter R. Cook is vice president of creative services for Grolier Electronic Publishing Inc. (95 Madison Ave., New York, NY 10016). He is responsible for coordinating the development of that firm’s Multi-Component Electronic Encyclopedia, which is intended to combine videodisc and videotex technology. Cook spent five years at Arete Publishing Co.. producing the Academic American Encyclopedia.

ENCYCLOPEDIAS EVOKE special memories for most people. When you were a child, you probably did research for essays and class projects, looked for “naughty” words and pictures, struggled through dull facts about dead people, or discovered fascinating facts in articles from “Aardvark” to “Zygote.” Later on, maybe you used an encyclopedia to solve crossword puzzles, to help a child with homework, or to look up the location of a vacation spot or an unfamiliar country mentioned in the news.

Now there is a whole new range of associations that most people wouldn’t normally connect with an encyclopedia: on-line databases, videotex systems, and laser videodiscs—new interactive technologies that, at first glance, might appear to be the very antithesis of the traditional printed encyclopedia. But major electronic publishing companies are beginning to create a new generation of encyclopedias, powerful informational/educational tools that can interact through, and with, all of these new media.

As part of a long-range development plan, Grolier is creating a massive encyclopedic database of text and audiovisual materials that can be accessed and manipulated using interactive technologies. The two major components of this plan, the text database and the audiovisual database, currently are be- ing developed along separate but convergent tracks—one utilizes on-line or videotex technology, the other utilizes videodisc technology.

In this article, 1 will review both development tracks, observing from the publisher’s point of view how information is enhanced by delivery via new interactive technologies. But let’s begin with a look at encyclopedias delivered via a traditional interactive medium—the book. Though new technologies should not slavishly imitate those that preceded them, there is much to be gained by using the book metaphor for building the foundation of an information tool that utilizes the full power of interactive video technologies.

According to an entry in the Academic American Encyclopedia (AAE), a printed general encyclopedia “attempts to present the entire realm of worthwhile knowledge: the humanities and literature: fine, applied, and performing arts: science and technology: history and social sciences: critical issues such as bioethics and civil rights: and select data on significant places and persons.”

Mechanics and economics tend to limit the size of a printed encyclopedia’s “realm of worthwhile knowledge”: of necessity, the information itself is synthesized and summarized. Distillation and outlining of knowledge, along with broad coverage, make a general encyclopedia—whether it be in 1, 20, or 30 volumes—a useful reference tool.

The reference characteristics of encyclopedias are what brought about their rather unnatural, usually alphabetical, information structure. There is no inherent logic in grouping “Aardvark” with “Alvar Aalto” and “Hank Aaron,” although such curious juxtapositions often create wonderfully serendipitous discoveries. Diverse subjects are thrown together for no reason other than the fact that an alphabetical, dictionary-like organization improves access to information. Some encyclopedias still cling to the earlier thematic approach in which related information is grouped together. Thematic groupings make it possible for information to be viewed in a broader context, but highly specific facts are harder to locate.

Alphabetical encyclopedias compensate for the seemingly arbitrary arrangement of their articles by using in- tegrated cross-references that indicate the presence of related articles and draw connections between the various realms of knowledge. In its current (fifteenth) edition, the Encyclopaedia Britannica attempts to overcome the shortcomings of this alphabetic tyranny by breaking the set into three resources: Propaedia. a one-volume overview of knowledge; Macropaedia, a collection of in-depth articles (many of considerable length) on broad areas of knowledge; and Micropaedia. containing very short articles as well as discrete, specific facts. The attempt, however, is thwarted by the awkwardness of three integrated, but separate, resources.

While encyclopedias may have to struggle with the drawbacks of their own unique organizations, they also exhibit the positive characteristics of the printed book. Books are physical entities, portable random-access devices. Their organization is universally recognized: pages, chapters, tables of contents, prefaces, introductions, indexes, bibliographies, etc. They are the framework of written language. Other characteristics inherent in books let you browse through them easily and give you a sense of scale and place. You know how to navigate in a book.

But the book also has its limitations. It is a fixed medium: once printed, it cannot be changed. The only way for a user to update a printed encyclopedia is to buy a new one, write notes in the margin, or purchase the yearbook that most encyclopedia publishers issue annually to maintain the currency of existing sets. The information is also fixed in that it cannot be dynamically rearranged for the user’s convenience. Comparing all the articles on dinosaurs, for example, might require accessing more than a dozen volumes. Information access is also limited by the specificity of the article titles and by the quality of the index—nonindexed information is almost the equivalent of no information. Finally, no matter how descriptive the text or how informative the illustrations, no printed encyclopedia can capture the power of a place, person, or event more vividly than an audiovisual medium. Yet the printed encyclopedia is, and will continue to be, a highly valued information resource for most people.

Now consider an electronic encyclopedia that uses the full power of new interactive media and is designed to meet the needs of a new generation of users.

Electronic Reference Work.

In 1982, Grolier acquired the rights to the Academic American Encyclopedia, a new 20-volume general-reference work designed for use in homes and schools. Containing approximately 30,000 articles and 9 million words, the AAE is characterized by its currency and its short entry format (its articles have an average length of approximately 300 words). For us it had the additional virtue of being typeset entirely with computerized equipment, and thus it could be converted for on-line dissemination.

The electronic edition of the AAE has been in existence for two years and is currently available to over 250,000 online and videotex subscribers through existing information utilities. These include services such as CompuServe, Dow Jones News/Retrieval, BRS. Dialog, and Vu/Ttext. We also distribute through NAPLPS (North American Presenta-tion-Level-Protocol Syntax, or “nap-lips”) graphics-based systems: Viewtron, Keycom, and Times Mirror’s Gateway (which uses Telidon graphics, a forerunner of NAPLPS). Users accessing the encyclopedia remain customers of the information utility, which in turn pays Grolier a royalty.

The encyclopedia’s inherent data structure has to be adapted to the display characteristics and access protocols of individual systems. Because these system requirements have a considerable effect on how the user interacts with the encyclopedia, it is worth reviewing some samples at length, beginning with the less complex, and consequently less powerful, systems.

Viewtron: An ASCII/NAPLPS Hybrid.

Viewtron, operated by Viewdata Corp. of America (a Knight-Ridder subsidiary), is the first commercial videotex service to use NAPLPS color graphics, which can be accessed only by AT&T’s Sceptre terminal. This regional service is now available in just three Florida counties; if successful, however, the service will become available in major cities around the country.

Viewtron is a relatively simple menu-driven system that stores most of its databases on preexisting frames. However, because the AAE is a large database (by videotex standards), it is actually accessed through a communications gateway. The AAE text is housed on computers at Vu/Text (another Knight-Ridder subsidiary) in Philadelphia; the computers are linked by dedicated line to the Viewtron host in Miami. A user accessing the system is connected via the gateway as soon as he selects the AAE from a menu (see photos la through Id). The videotex terminal “paints” the appropriate NAPLPS frame, but it has an active window for displaying the ASCI! (American National Standard Code for Information Interchange) text from the Vu/Text gateway. The user is then prompted to type in a search term, which is matched against the AAE’s 30,000 article titles. If an exact match exists, the system displays the first 15 lines of the article and the user can “page” through the rest at his own pace. If the search term is too broad, a number of articles are selected. For example, if just “Lincoln” is entered for information on Abraham Lincoln, the system locates all articles with the word “Lincoln” in the title, including “Lincoln, Nebraska” and “Lincoln Center for the Performing Arts.” The first article is displayed with the qualifier “1 of n [articles],” and the subscriber can then use the system’s “browse” function to scan the first frame of each article.

ASCII (Non-Graphic) Videotex Services.

Dow [ones News/Retrieval and CompuServe are both consumer-oriented information utilities that primarily use keyword and menu-driven access. A subscriber logging onto Dow Jones News/ Retrieval is guided to the AAE via names and enters a search term or query that is matched against article headings. If the search term is in more than one heading, the system generates a menu, listing all of the articles, and the user selects from this (see figures 1a through 1e). If the selected article is long, an additional menu (or series of menus) is shown, providing a numbered outline of the contents. Thus, the user can select the most appropriate section without having to page through the entire article.

Dow Jones News/Retrieval also lists the number of pages or screens of text in each article and lets the viewer know which page he is viewing (2 of 14, etc.). CompuServe gives each page an individual number, which can be used in conjunction with the GO command to go directly to the page, bypassing the intermediate menu stages. As useful as these features are, menu-driven systems are limited. Access is through the article title only, which doesn’t open up the full potential of an electronic encyclopedia.

Free Text Databases.

Two much more powerful on-line database systems are BRS and Dialog. Considerably more expensive than the consumer databases, BRS and Dialog use free text search procedures in which every word in the database is indexed and therefore can be searched.

When accessing via BRS, a search term or query is entered using the required command language. However, if the search term is not properly qualified, the system may locate far too many occurrences to be helpful. For example, a search for “Einstein” produced several hundred “hits” (occurrences) of the word in 69 articles throughout the encyclopedia (see figures 2a through 2c). But the search can be narrowed down by using Boolean operators such as and, which combines two search terms in the same article: same, which combines two terms in the same paragraph; with. which combines them in the same sentence; and adj. which requires the two terms be directly adjacent. If what I really want to find out about Einstein is when he moved to Princeton, I would phrase the search as: “Einstein same Princeton,” which means I’m looking for the paragraphs in which both of the words appear. This narrows the hits down to just two paragraphs, which can be quickly displayed. These paragraphs tell me that Einstein moved to Princeton in 1933 and that he died there in 1955.

This simple example doesn’t really illustrate the full retrieval capabilities of free text systems. They can be powerful tools in the hands of an experienced researcher or librarian. On the other hand, their complex command syntax and Boolean search logic make them too complex for easy access by most untrained users.

In an effort to broaden the appeal and usage of their services, BRS and Dialog have both introduced easier-to-use and less expensive off-peak services: BRS After Dark and Knowledge Index, respectively. Communications software is also being introduced; Sci-Mate and In-Search simplify command procedures and enable the user to develop a search strategy before going on line. Such efforts are the first steps in what will undoubtedly be a series of software products aimed at making these information utilities (including Dow Jones News/ Retrieval and CompuServe) more powerful and easier to use.

Earlier i used the printed book as an example of a medium with which we are manifestly familiar; the reason for our familiarity is that the structure and conventions of books have been evolving for centuries. On-line databases have been in use for little more than a decade, and it is only in the last two or three years that large numbers of untrained users have started accessing them. Consequently, the learning curve for everyone—system operators, information providers, and end users—is particularly steep. There is still much to be learned about how users interact with electronic information utilities, what kinds of displays are best, what accessing protocols and commands are most effective and easy to learn, and what information is most appropriate.

Enlarging the Database.

The electronic edition of the AAE is already quite different from its printed parent. Updated twice a year instead of annually, it has no physical growth limitations, unlike the printed work. We intend to use this essentially unlimited capacity for growth: to respond directly to users’ needs; to reflect areas of strong current interest; to broaden the database so it is more appropriate to different age and interest levels; and to develop satellite databases designed to interact with the encyclopedia.

Responding to users’ needs: An electronic encyclopedia has a unique advantage over its print counterpart because it is possible to “capture” such key parts of the information transaction as search terms and usage time. Analyzing the captured data can reveal shortcomings, whether in the form of inadequate article headings or missing information. Such data also reveals areas of high and low interest—a useful guide for database growth.

Reflecting areas of strong current interest: Printed encyclopedias contain little information of transitory interest. It will be a long time before the Britannica has an article on Michael Jackson. This isn’t necessarily because encyclopedia editors disdain popular culture. The physical limitations of the printed work make it difficult and costly to insert large numbers of new articles each year. Space has to be found for each new article, usually at the expense of other articles. Further, an article of fleeting interest may create a difficult hole to fill when its importance diminishes.

This is not the case with an electronic edition, in which articles can be added to and deleted from the database with considerable ease. For example, coverage of the Olympic Games and athletes can grow in anticipation of this year’s meeting in Los Angeles. Next year the coverage can be reduced. An electronic encyclopedia can be a truly responsive, dynamic reference work.

Expanding for a broader audience: In its present form, the AAE spans a wide range of age and interest levels. As stated in its preface, the AAE is “for students from junior high school, high school, or college and for the inquisitive adult.” By expanding that base to include young children and advanced scholars, the resulting database will be several times larger than the printed encyclopedia and will be capable of responding appropriately to the user’s age and interests.

Satellite databases: Grolier has recently completed the first of a series of satellite database products designed to interact with, and be enhanced by, the electronic encyclopedia. Whiz-Quiz is a menu-driven educational game that directs the player to the AAE to find out more about a topic. We believe that children in particular will be compelled by this mechanism to explore the encyclopedia.

The User Interface.

Regardless of what shape or direction a database takes, the key to its use and value is the user interface. The user interacts with the electronic encyclopedia on several distinct levels: entry level: logging onto a system and getting to the database search level: entering a search term to locate a specific article (or group of articles) retrieval level: once the relevant article is located, finding and retrieving the required information manipulation level: getting the information in the form of a printout, writing words down directly from the screen, or simply remembering the facts exit level: leaving the database The first and last levels are entirely the province of the system’s operator and, in any event, are not an obstacle to most users. The search and retrieval levels, however, are areas of major concern because that is where the user works most closely with the system. The information-manipulation level will become increasingly important as software is written to take full advantage of encyclopedic databases.

The best way to analyze potential improvements at the search level is to return to the book metaphor. As an access device, a book is very forgiving. When you look something up in an index, you usually don’t need to know the exact spelling to locate it. Likewise, you sometimes use a dictionary because you can’t spell a word but have no problem locating it.

Databases are not so forgiving. A misspelled search term, no matter how close to the correct word, cannot be used to locate the required article. Some systems attempt to overcome this by providing a function called truncation. On Dow Jones News/Retrieval, for example, all you have to enter for an article on Zbigniew Brzezinski is “BRZ—a nice feature, but not the complete solution. The problem isn’t just misspelling; children in particular tend to use plurals for certain common nouns: cats, dogs, trees, dinosaurs, etc. This is not a problem in a printed reference work; however, when entered on a videotex system, the search terms will fail to match the exact article titles, which are singular.

First-time users, especially children, make repeated errors when entering search terms. Analysis of the search terms for one of the videotex services reveals that about one-third of all terms failed to locate an article. In approximately 90 percent of those cases, the information existed but errors (misspellings, use of plurals, incorrect positioning of names) prevented the user from finding it, at least on the first try.

Clearly, the unforgiving nature of search-term entry on videotex systems is a frustrating inadequacy that can be improved by the system operators. At the same time, the information provider has a responsibility. Other aids to access are required. Current videotex systems allow only keyword access to article headings. There is no on-line index, and today’s videotex systems do not have the full text-indexing capabilities of BRS and Dialog. Clearly, the specific entry headings need to be broadened so that the same information is available via several different search terms. An on-line index would broaden access still further, especially when combined with a thesaurus function.

Free text systems are not restricted to keyword access. Rather, the user can focus his search language to a highly specific degree, examining the body of knowledge with precision. The price of that precision is a high degree of practice and skill.

In the long term, both keyword and free text access to large databases probably will give way to search languages with a high degree of artificial intelligence (AI). At present, when you search for information in an encyclopedia, particularly on videotex systems, you have to think about its likely location. You cannot interrogate the database, but this is exactly what you should be able to do, posing such questions as: Who wrote The Grapes of Wrath? How many Nobel Prize winners went to Harvard? Where do icebergs come from?

Answers to all these questions can be found eventually with current systems, but a fully developed database incorporating AI search techniques would take you directly to the sources.

Having located an article, the user begins to read it. The “window” into the encyclopedia’s massive database is a television or monitor. The text display (depending on the service and the end-user’s hardware) varies from 16 lines by 32 characters per line (approximately 85 words) to 2 5 lines by 80 characters per line (approximately 330 words). By contrast, the printed AAE contains 1500 words per page, and pages can be viewed two at a time. Clearly, current video-display technologies are capable of only the most myopic view of a large text database, which is why it is all the more important to be able to rapidly shift the view, to be able to browse and move around in an article quickly and easily.

But there is a need for other orientation tool§, such as sequential numbering of article pages (which Dow Jones News/Retrieval has) as well as individual numbering of pages (which CompuServe has).

A recent study of a group of eighth-graders’ use of the videotex AAE produced some interesting findings. While the students searched for articles and moved around in them with varying degrees of proficiency, they confined their activities to finding information rather than using it. They actually read and manipulated the information later as printouts, which could be studied at leisure, marked up, and incorporated into their research projects. In fact, I suspect that many of our users who have access to a printer do their serious reading in ink-on-paper form.

This doesn’t mean that no one reads text from the screen. Graphics-oriented videotex systems, such as Viewtron, are based on the assumption that subscribers will read from the screen. This is fine for news summaries. But the real utility of an electronic encyclopedia won’t be realized until people can access, manipulate, and reorganize significant amounts of information electronically using such powerful information tools as word processors, database managers, and graphics programs.

Electronic Knowledge Land.

Grolier is working on some of the refinements I have been describing. We believe that, having freed encyclopedia information from the artificial constraints of the alphabet and the physical constraints of the book, we should be able to reshape and reorganize that information. We want to put it to new uses. We want to create a reference tool that can interact with other information tools. Additionally, we’re trying to build a conceptual framework—an outline of knowledge—for intellectual pursuit and stimulation. At present, this new “knowledge land” is largely uncharted, although major landmarks are known. We hope that videotex systems will have the navigational tools to explore it fully, and that software producers will have created the manipulation tools to exploit it fully.

A Videodisc Encyclopedia.

The videodisc is another interactive medium that we believe is applicable to encyclopedia information. The ability to randomly access any frame, combined with the disc’s dense storage capacity (54,000 frames per side on a laser disc) and its inherent audiovisual properties, make it a particularly powerful publishing medium. As part of a joint venture with Long- man, a British publisher, Grolier recently produced a pilot disc. The pilot was developed as a test vehicle to determine how the organization, content, and audiovisual treatment of encyclopedia material might best be accomplished.

Long before the pilot went into production, we had concluded that we would need a lot of discs to encompass all the information contained in a general encyclopedia. This led us to ask ourselves how each disc should be organized so that it could be both a stand-alone information resource and a part of an integrated series. We decided to organize each disc around a specific theme or subject area. The pilot is part of what will eventually be a two-sided disc devoted to the human body (see photos 2a through 2c).

Each thematic videodisc will be a self-contained information resource. The discs will not attempt to be the equivalent of a printed reference work. Rather, each disc will “illuminate” knowledge areas, conveying through audiovisual means only the essence of a subject.

Designed for use with a standard consumer laser videodisc player under normal keypad control, the discs will become considerably more versatile resources under microcomputer control. While the number of combined microcomputer/videodisc applications has increased substantially in the last two years—applications that include training, point of purchase, education, and games—there are few truly “generic” discs for which software can be written.

Grolier is developing two electronic databases, one in text form and one in audiovisual form. These two databases are being developed separately so that each can take advantage of the separately developing markets for on-line / videotex and videodisc products. But both databases will ultimately be brought together (although whether through telecommunications or local mass storage is yet to be determined). The result should be an innovative informational/educational resource: an encyclopedia that is appropriate to the media and appropriate to the times.

An Ideal Video Peripheral by Mark Dahmke

As a software consultant, my major complaint with most of the popular videodisc players is that they communicate with computers very poorly. Typically, the videodisc player is treated as a printer or a plotter; the user has to deal with commands that may or may not be ASCII (American National Standard Code for Information Interchange) format and may or may not be logical and consistent.

The Discovision (now Pioneer) model 7820 had a command set that looked like a selection of random numbers. The codes to send the numerals 0 through 9 were: 3F. 0F, 8F. 4F. 2F. AF. 6F. 1F, 9F, and 5F. in that order. In addition, the 7820 had an IEEE-488 external interface that wasn’t compatible with most microcomputers. In an attempted remedy. Discovision built a serial converter box to change the IEEE-488 protocol to and from RS-232C levels. What they came up with was a protocol converter with a 1-byte buffer that could easily be overrun, erasing the last command before it could get to the player.

Even if the translation and protocol conversion problems are ironed out eventually, a programmer is still faced with a stiff challenge in trying to get the status and frame number back from the player. Some players won’t give out this information at all. Ones that do return strangely encoded bytes that take many instructions to untangle. On some players the frame number comes back as a 2-byte integer. on another it comes back as four ASCII digits in hexadecimal, and on still another it shows up as five-decimal ASCII digits. Any software expected to run on more than one model of videodisc player has to account for all of these differences.

Timing seems to be the worst problem with interfaces. Data sent to the player at serial-port speeds just can’t control a fast videodisc player in the manner required by modern interactive applications. Some new players offer parallel ports, but many computers (e.g.. the IBM Personal Computer) don’t support full bidirectional interfaces. IBM claims that its Centronics port is “parallel input and output.” However, if you check the circuit diagram, you will see that it isn’t. It is wired so that reading the port returns only what was last sent.

Newer videodisc players operate at floppy-disk and, in some cases, hard-disk speeds. Some have worst-case access times of 2 to 3 seconds. Within a year or two, I expect to see write-once, multiple-read videodiscs with interfaces to let them be used as archives. (Some current videodiscs can hold gigabytes of data.) For this to work, however, the interface will have to be smart enough to recover the stored data and fast enough to return it to main memory at magnetic-disk speeds. This technique can work, as shown by the fact that it is already being used in several hard-disk backup systems for videotape recording equipment. In these disk-to-tape systems, the data from the disk is recorded redundantly in the scan lines of a National “television System Committee (NTSC) signal, which is then recorded on videotape. While this prac- tice could easily be transferred to videodisc hardware, much of the videodisc would be wasted and not used to its full potential. The developing direct-digital recording techniques will remedy this problem by maximizing use of the disc recording surface.

Loading software into a personal computer from a videodisc as if it were a floppy disk would greatly enhance educational applications. For example, audiovisual and computer-graphics course material (all orchestrated by an authoring language) could be combined and loaded into a personal computer from the first part of a videodisc while just the audiovisual portion is stored separately on the remainder of the videodisc. A development system would consist of the videodisc player and other end-product hardware, but the graphics and curriculum-specific data, or “courseware.” would be developed on attached floppy-disk or hard-disk systems.

Figure 1 shows one possible hardware configuration for a first-generation intelligent player. The main feature of the design is the videodisc interface adapter, which would plug into an expansion slot on the microcomputer. The interface adapter gives the programmer tight control over the timing of the player and also controls the video overlay circuit.

As digital television and audio reproduction become affordable and popular (I estimate that this will take five to seven years), we’ll be able to define the formats that will let personal computers store and retrieve video images and sound. We’ll be able to create high-resolution computer graphics and synthesized music on personal computers and write it onto a write-once videodisc peripheral. We’ll then be able to play it back through digital television sets. Alternately, digital television images could be recorded from TV sets onto a videodisc and then retrieved. displayed, or processed on personal computers.

Figure 2 shows a second-generation interface built around digital television. As 32-bit processors become faster, and memory bandwidth greater, it will be possible to directly manipulate high-resolution images that come from the videodisc or are created directly by the microcomputer. The video output from the TV camera can be routed to a digital television for viewing, or the output can be held in the graphics frame buffer for further modification and processing.

Mark Dahmke. a contributing editor for BYTE, is a software consultant and heads MCD Consulting Inc. He can be contacted at POB 80266. Lincoln. NE 68501.

view additional pages

What’s a RAM?

The vocabulary of engineers or experimenters working with computers, synthesizers, electronic calculators and similar digital devices is replete with acronyms you should know. RAM is one, read on to find out what it is and how it’s used.

by DON LANCASTER

ANY MEMORY IS A STORAGE DEVICE THAT is given some information at some time and hopefully will return that identical information at a later date for reuse at least once. The most elemental unit of a memory storage system is the cell which can store one bit consisting of a “1-0″ or “Yes-No” simple decision. Memory cells are often grouped into words of several bits each. These words can represent the number in a calculator, an instruction command in a computer, a tone and its duration in an electronic music composer, an alphanumeric character in a TV Typewriter and so on.

Memories can range from one bit to many billions of bits. The equivalent of the human memory is sometimes suggested as 10 billion bits while the longest memory you can buy in a single off-the-shelf integrated circuit is 4096 bits.

There are several different types of memories. You usually classify them by when, how and how often you put information in them. A Read Only Memory (See “What is a Read Only Memory?”, Radio-Electronics, February 1974) has information put into it only once. It keeps the information inside it more or less permanently. Read only memories are often used for such things as square root, log and trig instruction microprograms in a calculator, for time-zone conversion in a digital clock and for many other situations where you always want the same response to your system. Some read-only-memory systems are called “table lookup” systems, for they provide an “answer” in the same way you would get it from a math handbook. A few read-only-memory systems can be altered, but not rapidly. This is done by erasing them with intense ultraviolet light and reprogramming them; others are altered with special voltage or current pulses. Sometimes these are called Read Mostly Memories.

We could also theoretically have a write only memory that would accept information but never return it. Contrary to some misguided and uninformed industry jokes about WOM’s, these DO “exist and have a very specialized use in computer programming, particularly in data stripping and formating. Still, nobody really manufactures WOM’s. When you want a WOM function, you use one location of a read-write memory over and over again instead, never bothering to read it.

The most versatile memory is one that you can write (put information into) and read (receive information from) rapidly and in any sequence. Magnetic cores are typically this type of memory, although by eliminating or not using the write current generators, we can also obtain a read only function. Most cores are destructively read out, meaning that the information is lost the first time you use it. You then have to perform a rewrite after read operation and then put the information back into the memory cells if you are going to use the information again.

Most semiconductor memories are non-destructively read out in that you can accept information without physically altering the memory contents.

If you must put the information in and get it back in one specified sequence, you have a sequential memory. Long MOS shift registers can make a sequential memory. These have traditionally been lower in cost than true read-write memories, but have disadvantages of being noisier and having to wait a long time for the information you need to come out.

The more versatile read-write memory is one that you can read or write in any location at any time. This is called a Random Access Memory, or RAM for short. RAM’s can be made sequential simply by deciding that you want to access or address things in order.

A memory is non-volatile if you can remove the supply power or stop moving the data around inside the memory and still hold the information. Magnetic core is usually non-volatile. Semiconductor read only memories are, of course, non-volatile. Most reasonable or available semiconductor RAM’s are volatile and you must keep the supply power up or you will lose information. Many RAM’s offer a reduced power mode where you can keep information for long times on battery power. In a few years, we can expect true non-volatile semiconductor RAM’s, but for now, you have to design your memory application in such a way that the information is either no longer needed or stored somewhere else than in a semiconductor RAM during power down times. This really isn’t nearly as bad as it seems for usually you can easily get around the problem one way or another. Often a mixture of ROM’s and RAM’s in a single system does the job.

There are two basic types of semiconductor RAM’s. These are the static RAM and the dynamic RAM. Both of these are volatile and will lose information during power down times. The difference is that static RAM’s will keep their information so long as power is applied without reshuffling or refreshing the data while a dynamic RAM has to have its internal storage moved around occasionally, often at a 500-hertz rate or faster. Static RAM’s usually have a flip-flop cell for data storage. Once set or reset, it will stay in that state until power is removed or it is relr tten. Dynamic RAM’s usually use a capacitor for data storage. The capacitor will eventually discharge and thus the data must be moved or refreshed before it is lost. Dynamic RAM’s are normally far cheaper as you can pack a lot more bits onto a given size chip, but they add to the external circuit complexity and may take some elaborate timing to reliably get them to work. Thus, dynamic RAM’s are more suited for very large memory systems, those over 50,000 bits or so.

Today, you can buy a 256-bit surplus static RAM for $2.56 and get the same thing new for under $6.00. A 1024-bit dynamic RAM runs around $5.00 surplus and under $12.00 new. Thus, we are talking prices right now of a penny per bit and under and projected pricing runs as low as one-tenth of a penny per bit. At this projected pricing, a minicomputer computer memory big enough to speak Basic or Fortran could be built for a memory component cost of $64.00 for 64,000 bits, perhaps arranged as 4000 words of 16 bits each. Simpler memory systems for things like terminals, electronic locks, music composers and a whole bunch of things nobody has thought up yet today should cost well under $20.00 and eventually should come down to $2.00. So, now is the time to start becoming familiar with these exciting new devices.

A simple semiconductor RAM Let’s start with a rather small RAM and see what we can do with it. We’ll use the 7474 TTL dual type D flip-flop as shown in Fig. 1. We’ll start with a one-bit memory and then double it to two bits by using both halves of the package.

In Fig. 1-a, we use half the 7474. This stage can store a “1″ (often a high state around 3.3 volts) or a “0″ (usually a low state around 0.5 volt). The stored value appears at the “Q” output. The opposite or compliment of the stored value appears at ‘he Q output. We have a data or D input and a clock or CL input. Information present on ‘he D line gets loaded into our memory at the time the clock goes from ground to a positive value. To enter information into our memory, we put the information on the D line. At that time, it does NOT go into the cell. At the instant we bring the clock line from ground to a positive level or from a TTL positive logic 0 to a positive logic 1, we actually load or write the information into our flip-flop cell. Whatever was on D at the instant of positive edge clocking gets loaded into the memory and appears at the Q output.

This is a random access memory as we always can get to the memory cell (trivial, as we only have one cell) anytime we want. It is static as it will keep the loaded information for as long as we apply power. It is volatile as the information will go away if we ever shut off the +5-volt power supply. And our simple memory is organized as “one word of one bit each.”

We can watch or read our memory any time we like, but since a change may be produced during clocking, we shouldn’t be using or reading at that particular instant. We call the clocking interval the write cycle. Time spent looking at this particular cell’s output is called the read cycle. Normally, you don’t read and write simultaneously. You either execute a read cycle where you monitor and use the output of the memory cell or you execute a write cycle where you place new information into the cell. The 7474 will do a write or a read cycle in under 50 ns. Since nothing physically changes internal to the 7474 during reading, the readout is non-destructive and we can reuse the stored information hundreds or even millions of times if we like.

A one-bit, one-word memory by itself isn’t too useful, although you can think of an alarm system as a one-bit memory and there are numerous other trivial applications. To do any really useful function, we most often need quite a few more bits of storage.

Figure 1-b shows how you can use both halves of a 7474 to build a memory of one word of two bits. This is done by simultaneously clocking each half of the package and using both outputs at once. Thus we have two data input lines, two output lines and one write line. This organization is one word of two bits. In 1-c, we have the opposite, a memory of two words of one bit each. Now something new has been added. We have to combine or select which of the two memory bits is going to appear as an output. We also have to decide which of the two cells is going to have data written into it at any given time. This decision is called addressing. We now have to address cell A (a 0 on the address line) or cell B (a 1 on the address line). By controlling the address line, we select which memory cell is to be acted upon or read.

The more cells we have, the more complicated the addressing will become. Note that we needn’t alternate memory cells if you don’t want to. You can address either cell in any sequence you want. Hence the name random access.

Adding more bits We could use as many 7474′s as we like to build up any memory, but even at surplus prices, the 25( or so per bit and the large supply power and size will eventually get to us. The next step up is to use packages with more than two D flip-flops. Quad and hex latches, the 74175 and 74174 are a good choice. Figure 2 shows some memory circuits using these components.

In Fig. 2-a, we have a 16-cell memory arranged as four words of four bits each. We have four data lines, four output lines and two address lines. These two address lines are binarily decoded (00, 01, 10 and 11) to get at the four possible memory cell locations. We might use this memory to store four BCD numbers as part of a computer or calculator.

In Fig. 2-b, we use eight 74174′s to build a 48-bit memory organized as eight words of six bits each. This time, we have six data input lines, six output lines, and three address lines. The three address lines are decoded (000, 001, 010, 011, 100, 101, 110 and 111) to get at the eight possible locations of six cell groups. Since we can represent a letter, number, space or punctuation with six bits of the standard ASCII code, this memory could be used to store an eight character message.

Which organization?

Suppose we had a 64-cell memory. How could we group the cells to obtain different combinations of bits-per-word and numbers of words? Figure 3 shows some possibilities. While each of these memories is 64 bits total capacity, the organization of each is different.

In Fig. 3-a, we have one word of 64 bits each. We need zero address lines since we are always looking at the same word, but we need 64 input lines and 64 output lines. In Fig. 3-b, we have two words of 32-bits each. We now need one address line to select which half of the memory is to be written into or read from. There are 32 input leads and 32 output leads. The next combination of Fig. 3-c would be four words of 16 bits each. Here we need two address lines binarily decoded to select which quarter of the memory is to be active and there would be 16 input leads and 16 output leads.

You can rapidly run down the other organizations. Figure 3-d gives us eight words of eight bits each. There are three address lines needed that are decoded one-of-eight to pick one-eighth of the memory for use and we have eight input lines and eight output lines. In Fig. 3-e, we have four words of 16 bits each. Four address lines decode one of sixteen and there are four input and output lines. Two words of 32 bits each take two input lines, two output lines and five address lines, the latter decoded one- of -32 as shown in Fig. 3-f. Finally, in Fig. 3-g, we have 64 words of one bit each. There is one input line, one output line and six address lines which are binarily decoded one-of-64 to pick which of the individual memory cells is to be interrogated.

So, we have a wide choice of organizations to any memory. The more the bits, the more the choices. Which do we use?

This depends on you if you are working with a large system and depends on the integrated circuit manufacturer if you are trying to get the job done with only one or two stock integrated circuits. Obviously, you organize the memory to suit the information you are trying to put into it. Four-bit words are common for BCD (binary coded decimal) number storage in calculators. Six-bit words are often used to store ASCII characters. If the full ASCII code, including transparent control commands and lower case and error detection is to be used, we have to up to eight bits per word. Or, we might like to use the remaining two bits to select a color on a color display. We could get one of four with two bits. Minicomputers tend to use 8-, 9-, 12-, 13-, 16-, 17-, 18-, 24- or 25-bit words depending on the manufacturer and the task the computer is aimed at. So, for system’s use, you pick the number of bits needed to do the job.

On the other hand, if you are a integrated circuit manufacturer, you want to have the most reasonable package in your system. The majority of semiconductor memories only have ONE input line and ONE output line and address lines for one-of-N decoding, giving you organizations such as 256 one-bit words 1024 one-bit words, 4096 one-bit words, and so on. Occasionally a smaller memory may have four bits per word, to make working with BCD numbers easier. Other arrangements are rarely used and you usually add packages to pick up the total number of bits you want.

Decoding All organizations in Fig. 3 have binary to one-of-N decoders on the address lines. If this decoder is internally provided in the integrated circuit as it almost always is, we have an internally decoded memory. If we must provide external address decoding as is common with magnetic cores, we need external decoding. External decoding is also needed when you have several memory packages that you are combining for a total storage. In this case, you use output enable or chip select lines to pick which package is to be used. Once selected, each individual package then goes on to provide internal decoding. For instance, with two IC’s we could simply tie their inputs and outputs together and drive the first memory’s chip select as an address line and drive the second memory’s chip select from the compliment of that line. Thus, we pick one-of-two memory IC’s and the chip selects give us a new form of addressing. If we tie four memories together, we use two new address lines, one-of-four decode them and then chip select only one memory at a time. Figure 4 shows how you can expand memories using the chip select system.

Unlike magnetic cores and many older memory systems, the data input and output lines are completely separate with most new semiconductor RAM’s. This eliminates amplifier recovery problems, steering networks, “single port” problems and things like this.

Who makes what?

Figure 5 is a list of my choice of the best There are lots of different ways to classify semiconductor RAM’s. One grouping is based on the process used. Bipolar RAM’s include TI L and ECL logic. MOS versions include P-channel, (metal and silicon gate), N-channel, and CMOS types. In the past, MOS devices have almost always been slower and much cheaper. Some MOS memories are now as fast as TTL and most MOS devices will continue to be cheaper than bipolar for some time to come.

MOS memories are further broken down into static and dynamic versions. Dynamic versions are much cheaper and much harder to use, particularly in experimental or very small system applications.

Let’s take a closer look at some specific IC’s: 7489 The 7489 is a good choice for initial experiments with RAM’s. It is TTL and works off a single 5-volt supply. Organization is 16 words of four bits each as shown in Fig. 7.

There are four data inputs and four data outputs along with four address lines. The address lines are four-line-to-one-of-sixteen decoded internally. Internal circuitry is arranged so that you store and read out the compliment of the input information.

To read this memory, you apply a four-bit address to pick the slot you want to look at and then bring the memory enable line low. For instance, address 0101 selects the fifth group of four cells. Data appears at the output shortly after the address is stable.

To write into the 7489, pick an address, input the compliment of the data you want to store and then briefly bring the write enable low. This loads the memory.

One thing you have to watch very carefully in any semiconductor memory is that the address cannot be changed immediately before, during or immediately after a write command. (The definition of “immediately” varies with the IC—carefully consult the data sheets!) As a memory address changes, certain locations are “flashed” by in the decoding process. It is possible to write, erase or physically move data around if you aren’t careful. ALWAYS PULSE THE WRITE COMMAND ON ANY SEMICONDUCTOR MEMORY. NEVER CHANGE ADDRESSES DURING WRITE PULSING! Put another way, always leave the memory in a disable or a read mode. Don’t put into write mode until after the address is stable. This particular memory cycles in under 50 ns. If you are running any memory very fast, times will occur when the old information or wrong information will be put out until the answers settle down. If this “garbage” time is too great for your application, you can add a latch to the output (perhaps a 74174) to sample the output only during instants when you know the data is good. A very few new memory lC’s include internal latches and eliminate this problem.

By the same token, if you are running fast, the ripple and gate times on address changes may cut into your cycle time significantly. Again, if you are running fast, it pays to either use fully synchronous timing or else latch the addresses to get them all changing at once. Some semiconductor mainframes get around the problem by using emitter coupled logic (ECL) and its very high speeds for addressing.

The 7489 has a few obvious and apparently untapped electronic music applications. For instance, you can use sixteen four-bit words to completely specify one cycle of a music waveform, the attack-sustain-decay envelope of a note or a melodic sequence. These run around $3.50 surplus and under $11.00 new.

Other TTL memories There’s quite a few other TTL memories available, some as long as 1024 bits. The 7481 is a very old design arranged as sixteen words of one bit each. The 74170 is called a 4×4 file, meaning it is a 16-bit memory arranged as four words of four bits each. The 74200 and faster 74S200 are a 256 x 1 memory or 256 words of one bit each. There’s also a bunch of “non-7400″ TTL memories. The Signetics 8225 is a pin-for-pin replacement for the 7489.

1101 The 1101 is a MOS static memory arranged as 256 words on one bit each. It’s shown in Fig. 8. MOS memories are gener- ally much cheaper and often much slower than TTL ones. The 1101 works on +5, -9 supplies and runs quite hot. There is TTL compatibility on inputs, addresses and outputs. There are seven address lines, internally decoded to pick one of the 256 bits. There is one input line and two output lines, a normal one and its compliment.

To read, you make the chip select low and the read/write low after applying the selected address. The output data will be valid within a microsecond or so afterward.

To write, you select your address, wait 300 ns, bring the read/write line high for at least 400 ns and then wait at least 100 ns after the write line goes low before changing addresses. As usual, NEVER change the address during, before or immediately after writing.

The 1101 is widely available and costs as little as $2.56 for probably good surplus units and as little as 50? for questionable surplus units. New cost is under $6.00. One possible application would to be using six of them in a data terminal or programmable calculator to store a 256-word message using the ASCII code.

Improved 1101′s The original 1101′s were rather slow and could take as long as 1.5 ms to read. They are very hot running and the -9 supply is usually a rather wierd thing to have to provide. Improved devices are now available. An 1101A1 cycles in one microsecond maximum. The Signetics 25L01 and the Mostek MK4007-4P are second-generation, pin-identical, versions that cycle in under a microsecond, consume much less supply power and work on standard +5, -12 supplies.

CMOS RAM’s One new type of 1101 replacement is the CD4061, a CMOS device made by RCA. This is a pin-for-pin replacement, but being CMOS, it takes only one supply and draws utterly negligible supply power if you aren’t writing or changing the address. Thus, you can use this with a very small battery for power down storage and still hold the information.You can also run on incredibly lower currents than the 1101 style devices and much faster as well—several hundred nanoseconds. This makes the 4061 ideal for hand-held data equipment and calculators, as well as meter readers and things like this. The only hitch—it’s a new device and still costs $40.00. Maybe next year.

Other CMOS memories include the Motorola 14505 (64 x 1), the Solid State Scientific SCL5554 (256 x 1) and the Inselek A5503 (256 x 1).

1103 The main reason we include the 1103 here is as a warning NOT to try and use it-—unless you have lots of fancy equipment and considerable experience. This is especially true of surplus 1103′s.

The 1103 is a 1024-word x 1-bit dynamic shift register. It is very low in cost. It ranks as the all time most successful single integrated circuit and it toppled “king core” from the computer world. The device trades a very simple and very dense internal circuit for quite a bit in the way of outside support circuitry. This IC needs critically controlled clocks, usually needs an output sense amplifier, and has a complex timing sequence so elaborate that a 30-ns overlap error in the wrong place will cause information dropout. The 1103 is eminently suited for large memories of at least 50,000 bits (this is tiny by mainframe computer standards) or so, where all the critical support circuitry is easily worked with and may be offset by the savings you get by cramming 1000 bits in each package.

The 1103 uses capacitors for internal data storage. The data must be moved around or refreshed at least 500 times per second.

The 1103 is obsolete today. There are some significantly improved devices available today that are much easier to use, but they still are a rather tough design problem if you do not have elaborate equipment and considerable digital know-how. Improved versions include the Intel 1103-A, the Mostek MK4006 and MK.4008, the Electronic Arrays EA1500 1501 and 1502 and the American Microsystems S3103.

4096 bits The big race today is to build an improved 1103-style integrated circuit with 4096 bits. At least one has been announced by TI at a 100-lot price of $26.00, or around 0.6cc per bit. The other manufacturers aren’t taking this sitting down and the race is on. Pinouts have pretty much been standardized and some should be available as you read this. Competitive products include the Electronic Arrays 1504, the Intel 2107A, Standard Microsystems 4412, Texas Instruments 4030, Microsystems International 7112, Mostek 4096, Motorola 6605 and probably a bunch more. Only eight of these integrated circuits are needed to build a decent minicomputer main memory.

+5-volt, single supply MOS memories A number of new, very easy to use and interchangeable MOS memories are now available that use an n-channel static technology. They have no clocks and are entirely and absolutely TTL compatible. There are no clocks or sense amplifiers needed. These include the Signetics 2602, the Intel 2102, Intersil 1M7552, Motorola MCM6602 and the Microsystems International MF 2102. Cost in single quantities is around 2

These integrated circuits cycle in a microsecond and screened 0.5-ms devices are also available. There are ten input address lines, a data in and a data out. Figure 9 shows the pinouts.

To read, you pick your address with the chip select low and the read-write high. The output data appears within a microsecond or so of an address change. To write, apply your input data, select your address, wait 400 ns, bring the write line low for at least 500 ns, send it back high again and wait at least 100 ns before changing the address. Once again, don't change the address immediately before, during or immediately after the write line is active low. The chip select can be used to expand the memory by several IC's. Six of these in parallel are ideal for a data terminal or TV typewriter memory. Prices should drop well under a penny per bit by next year.

What good are semiconductor memories? Calculators, programmable computers, teaching machines, terminals, TV typewriters, electronic games, minicomputers, fullblown computers, electronic music and hundreds of other applications exist now. What can you do with them? Let us know.

Sitting here on my 50 mbs internet connection I’m going to say that guess was a bit off. The total amount data they are talking about transmitting over a year is less than the size of the images in this post.

I also particularly liked that the searches on the third page are for “Computer, Privacy Surveillance, NSA and Tapping”. Just a hunch but I’d guess that the person who made that screenshot probably later joined the EFF.

view additional pages

Trends in Telecommunications

On-line search software and faster modems for PCs

by John Markoff

Now that the personal computer (PC) has won the battle for office desktop space, software developers are turning their attention toward programs that combine the storage capacity of mainframe computers with the local processing power of PCs. Although mainframes offer PC users access to huge on-line databases of specialized information, how to get to the information and bring it to the PC in a usable form is another question entirely.

In recent months, a new class of PC software has emerged that facilitates the redistribution of tasks between mainframes and PCs. It is called “on-line search” or “database-access” software, and these programs give us a glimpse of how radically PCs will alter the traditional mainframe database-access model based on one central processor and hundreds of remote dumb terminals.

In contrast, on-line search software uses the processing power of the PC to mediate between the researcher and the mainframe database and can offer potentially both a simpler user interface for novices and a more powerful searching tool for experts.

During the past decade there has been an explosion of new sources of electronic information. Several mainframe electronic-information providers such as The Source, CompuServe, and Newsnet have designed their systems specifically for novice users, but most on-line database services require special training to be used effectively. These include databases such as Dialog Information Retrieval Service, Nexis and Lexis, and Data Resources Incorporated.

The high cost of on-line information is also a deterrent to new users. Some databases on Dialog cost more than $100 an hour. This has meant that users generally must undergo extensive training to learn how to develop search strategies to minimize connect time.

Reducing Costs PC-based on-line search software will be beneficial to database users because it will simplify complex user interfaces now found on many mainframe databases and it will permit extensive off-line preprocessing of searches, there- by reducing the cost of information retrieval.

On-line search software introduced to date can be placed in two distinct categories. The first category is composed of programs that are “loosely coupled” to a specific mainframe database. These programs are extensions of intelligent communications software programs and generally permit automatic log-on, query, and downloading from a host mainframe computer.

The second category includes software that has been “tightly coupled” to one or more particular databases. By tailoring programs for interaction with a host computer, software designers are able to create user interfaces that require little knowledge on the part of the user of either micro-to-mainframe communications or the formal database query process.

The emergence of new communication network standards and standards in the on-line information industry will tighten this coupling to the point where the relationship between the mainframe database system and PC software will approximate the current relationship between operating systems and application programs.

Dialog, a subsidiary of the Lockheed Corporation, is the largest collection of public online databases. It has more than 75 million records of information including articles from over 60,000 journals. These records are contained in more than 200 separate databases ranging form biographic databases such as American Men & Women of Science to statistical databases such as U.S. Exports.

Most Dialog reference records are currently available as abstracts that require you to go to a library to obtain the entire article or source (articles can be ordered on line for an extra fee). However, there is a trend toward making the full text of documents available on line. One Dialog database provider, Information Access Corporation, recently introduced two such databases, called Magazine ASAP and Trade & Industry ASAP, that will cover 120 different popular magazines and publications ranging from Scientific American to Playboy.

In-Search.

In-Search is an example of an on-line search program that has been tightly coupled with the Dialog databases.

In-Search, initially designed to be used on the IBM PC or PC XT, was introduced recently by the Menlo Corporation of Santa Clara, California. This program costs $399. It differs from other database-communication programs both in its scope (the program and its assorted reference files occupy more than one megabyte of disk space) and in the sophistication of its user interface, which offers a window-based display environment and “unhooks” the control of the database query process from the Dialog mainframe computer. “Unhooking” means that you’re able to prepare your query in a screen-oriented editor while either on or off line. The process takes place with little interaction with the Dialog mainframe computer.

If the query has been prepared off line, you can log on to Dialog and have the query sent automatically. When Dialog responds with abstracts, they appear specially formatted in an overlapping window display.

Here, again, the user interaction is not dependent on the control of a remote mainframe computer. If you wish to interrupt the flow of information from the Dialog mainframe, you can do so simply by paging backward or forward through the information in much the same way that you can scroll through a text document in word-processing software. Because information from Dialog can be captured in a buffer (In-Search tailors the size of the buffer to the available memory level of an individual computer) on your PC, it’s possible to selectively mark records for later printing. You also can store retrievals to disk as ASCII (American National Standard Code for Information Interchange) text that can be edited by a word processor or called up for viewing by In-Search.

In designing the In-Search user interface, Menlo Corporation has attempted to take concepts from other popular types of PC software. For example, when working in the query editor, you can edit and change lines of text exactly as though you were working with a document text editor. In-Search has even supplied users with the option of the familiar WordStar command-key sequences for cursor control and word and character deletions (the cursor-control keypad is functional as well). The basic In-Search display also contains a menu of command options that are arranged similarly to those provided by electronic spreadsheet programs. By pressing a function key, you can enter a command mode and select a command that will cause In-Search either to send a particular command to the Dialog system or to retrieve information from its own local database.

Although it is possible to first prepare a particular search strategy off line and then retrieve references quickly to minimize connect-time charges, In-Search is based on a different, more interactive philosophy of on-line database use.

Menlo’s president, Lloyd Kreuzer, argues that In-Search is designed to function in a highly interactive manner. This sets it apart from other PC front-end software packages that assume you know what you want before going on line.

In contrast, Kreuzer believes that the most effective way to use a database like Dialog is to be able to alter a search strategy depending on the nature of the data revealed on a search. “Interactive searching is less precise and therefore more likely to turn up things,” he says. “The keyboard is never dead and [in fact] it is uncoupled from the Dialog process.”

When using In-Search on a fixed disk, the program provides local on-line detailed information on each individual database. This information, traditionally provided as printed textual documentation by Dialog (on forms called “blue sheets”), allows you to obtain information on the scope of an individual database as well as information on specific database indexes that aid in refining searches.

In-Search also supplies you with local context-sensitive on-line help both for using Dialog and In-Search. If you have an IBM PC without a fixed disk, you must insert one of four separate floppy disks that represent major database categories: arts, education, and social sciences; biology and medicine; busi- ness, government, and news: and engineering, mathematics, and physical science. On a fixed-disk PC, these files are directly accessible by the program and in the future it may be possible for the Menlo Corporation to use Dialog to download updates both to the on-line reference sheets and to the In-Search program itself.

The search process begins with selection of a database to search in. The first In-Search display shows three windows. Two small windows on the left side of the screen allow you to select one of the four major categories and to select further specific subject areas within each category. After you select category and subject you can select a specific database. At this point you are placed in the query editor (In-Search calls this the Search Keywords and Phrases screen) to formalize a search.

After In-Search sends the query to Dialog, the references yielded by each search are displayed in a separate window referred to as a reference text display. Any search words that you entered in the query editor appear as highlighted text as they are scrolled on the reference text screen.

At the same time, information on modem status is given in a small window in the lower-right corner of the display. When Dialog is sending records, the window indicates Phone-Working. The status changes to Phone-Online after the records have been retrieved or when you interrupt the retrieval process.

For a simple search to answer the question “Are there any books currently available that describe bicycle tours of the California wine-growing region?” You would first select the Books in Print database and then enter the words “bicycle.” “wine,” and “California” in the query editor. You enter each of these words on a separate line. The first three lines of the editor are labeled S1, S2, and S3. On line S4, you enter the phrase “S1 AND S2 AND S3″ to insure that any reference in Books in Print that contains the first three words in its abstract will be located. (Running this query with In-Search located one book: Grape Expeditions: Bicycle Tours of the California Wine Country.) In-Search documents the AND, OR, and NOT logical operators, which are subsets of Dialog’s complete range. However, expert users can implement all the other search operators that Dialog permits.

Effective searching of the Dialog database, even with In-Search, is frequently complicated. Since Dialog is generally a collection of document abstracts, it is heavily indexed, and it is important to understand the structure of the indexes to conduct a complete search.

A Dialog database is broken into records that are composed of fields. A typical record might include fields such as title, author, journal, abstract, descriptors, and identifiers. (Descriptors and identifiers are standard and nonstandard terms used by the database publisher to identify the subject matter of a record.) Each field is indexed either as a word index or as a phrase index.

In-Search gives you on-line access to specific indexes for each database. You can select an index for any term or phrase entered on the query editor screen. You also can send the Dialog database an “Expand” command that shows a listing of indexed words around the particular search word for a particular field in the database. This often will aid in narrowing down the focus of a search. (It is possible to search only one Dialog database at a time, however, some preselection is possible by searching the subject index first with a special command.) The importance of indexed searching was exemplified when I searched for my last name in The Computer Database. No references were found; however, when the author index was specified, Dialog located 106 references.

Possibly the most intriguing aspect of this new class of software is the change that it portends in the realm of microcomputer-to-mainframe communications. The analogy that casts the mainframe database in the role of an operating system, linked simultaneously to many remote application programs, brings many possibilities into view. In this model, interaction between microcomputers and mainframe computers would be similar to program calls to an operating system.

Menlo’s Kreuzer has called upon online database providers to develop an open-architecture, machine-to-machine interface standard that would permit third-party software developers to create a new generation of applications programs.

“(What is needed is) a universal set of calls to create an open standard for the on-line community that will let us, or anyone, write applications programs,” he says. “The information industry literally will explode once we have a machine interface to all the data.”

Such an architecture would move in a philosophically different direction than the one currently being followed by some on-line information providers who have been setting up systems based on hierarchical “user-friendly” menus for novice users.

Instead, Kreuzer is aiming at fundamentally changing the division of labor between mainframes and PCs. While it is logical that the data searching and sorting algorithms will remain on the mainframe computer, the PC can be expected to handle the user interface, on-line help, and preprocessing of the search request more efficiently.

Further Benefits

Tighter coupling of the communications process between mainframe host and remote PC potentially can yield other dividends as well. Higher data-communications speeds is one obvious possibility. In-Search already uses a significant amount of data compression on the large on-line reference files that are stored on the PC to reduce their size by almost 40 percent. There are a series of simple strategies for increasing the data-communications bandwidth as well. If the applications program can be coupled more tightly to the host computer, it is possible to employ a variety of data-compression strategies to go beyond the current 1200-bps (bit-per-second) limitation over phone lines.

Post-processing is another significant area. While In-Search currently formats only downloaded information and stores it to disk or outputs it to a printer, several other on-line search programs permit later manipulation of information as well. SciMate, from the Institute for Scientific Information (ISI) in Philadelphia, is an on-line search program that is priced at $880 and designed for IBM PC, Apple II, and CP/M computers. It provides for automatic logon and query of four different database systems and includes a local database manager that makes it possible to store downloaded information. The database component of SciMate is called Personal Data Manager. It will take advantage of the record and field structure of information from a host computer or permit you to create your own structure for a local database. Although there are limitations on field and record size, Personal Data Manager permits you to link records to store longer textual documents. You also can move files to word-processing programs or merge locally created notes or documents into the database.

In a smaller fashion. Informatics General Corporation and VisiCorp have developed two complementary programs, Answer/DB and VisiAnswer, that permit the transfer of quantitative data from a corporate mainframe computer to an IBM PC where it can then be loaded into a VisiCalc spreadsheet program for local analysis.

Faster Modems for PCs

Today there are a series of barriers confronting high-speed PC data communications. Most of these barriers fall within the realm of the voice-grade telecommunication network and into existing modem technologies designed to send data over this network.

Yet, while digital technologies are promising dramatically higher communication speeds, a series of new modem designs is being introduced that will bring PC-to-PC data rates up to 9600 bps and, with additional data compression, may push speeds higher.

The new technology wasn’t originally developed for personal computer users, but rather for digital-facsimile transmission systems. Now that the technology has been moved to PCs, it raises a number of possibilities, including using facsimile machines as remote input-output devices for PCs.

Gamma “technology, a Palo Alto, California, data-communications corporation, recently introduced the FAXT-96, a half-duplex 9600-bps synchronous modem board for the IBM PC and PC XT.

Priced initially at $1995 and designed to be used with a synchronous adapter card, the FAXT-96 plugs directly into a card slot in an IBM PC or PC compatible and permits 9600-bps communication over ordinary dial-up telephone lines. The modem includes auto-dial, autoanswer, and multiple-speed features. It connects directly to a phone line and to a synchronous adapter.

The use of dial-up 9600-bps communications is new. It has been made possible because of improvements in modem technology and improvements in the method of encoding digital data on bandwidth-limited voice-grade lines. Control of the FAXT-96 is handled in software from a “master control panel” screen on the IBM PC.

Previous high-speed synchronous modems have been stand-alone units that have been intended for either remote-terminal or micro-to-mainframe communication. The Gamma Technology modem differs in that, although it can be used as a high-speed micro- to-mainframe communications link, a software package also is being offered that permits error-checked PC-to-PC file transmission at 9600 bps.

The shift from asynchronous to synchronous transmission protocols at higher data rates frees the communication process from the start-stop bit overhead, a difference that automatically yields about a 20 percent increase in transmission efficiency.

The significance of higher data communications rates has grown with the deregulation of the communications industry because communication costs are expected to rise. Gamma Technology is claiming that an eightfold increase in data rate (from 1200 bps to 9600 bps) will save several thousand dollars a year if 160K bytes of information are transmitted daily across the United States. Savings would be even greater if data were transmitted overseas.

The FAXT-96 can be programmed to meet several international modem standards set by the CCITT (International Consultant Committee for “telegraph and “telephone). The standards include CCITT V.29 at 9600, 7200, and 4800 bps and CCITT V.27 at 4800 and 2400 bps. Until now, U.S. modem signaling standards have been dominated by AT&T-developed standards. That’s changing, both because of the global need for communications and because AT&T has less influence in an area of deregulation.

There are some limitations. Because sending data at 9600 bps is pressing to the limit what currently is possible with voice-grade lines, poor line quality can make it impossible to send data at that speed. “lb cope with line-quality problems, the Gamma “technology modem automatically tests line quality during an initial handshaking phase and then sets transmission speed at the highest data rate the line will support, ranging from 9600 bps down to 2400 bps. The line test is done by having one system send a known signal to the receiving system. The receiving system knows what it is supposed to get and can make adjustments to make the closest fit.

A recent study by Xerox of facsimile-system performance showed that the same modem technology that Gamma is using would support 9600-bps data transmission worldwide approximately 75 percent of the time over voice-grade lines. Over domestic long-distance lines the 7200-bps rate had to be selected only 27 percent of the time.

In addition to cutting communications costs, higher-speed data communications opens up new applications. Facsimile-to-PC connections would make the transmission of the textual information possible for bit-mapped display on the IBM PC. At 9600 bps the facsimile-transmission time for an by 11-inch piece of paper is 30 seconds. Another possibility is for the transmission of specialized database information that includes diagrams or other images.

MORE COLOR. MORE SOUND. MORE GRAPHICS CAPABILITIES.

Compare the built-in features of leading microcomputers with the Atari personal computers. And go ahead, compare apples and oranges. Their most expensive against our least expensive: the ATARI 400 Start with graphics capabilities. The ATARI 400 offers 128 color variations. 16 colors in 8 luminance levels. Plus 29 keystroke graphics symbols and 8 graphics modes. All controlled from a full 57 key ASCII keyboard. With upper and lower case. And the system is FCC approved with a built-in RF modulator That’s just for openers.

Now, compare sound capabilities. Four separate sound channels and a built-in speaker. With the optional audio/digital recorder, you can add Atari’s unique Talk & Teach Educational System cassettes.

Here’s the clincher: Solid state (ROM) software. For home management, business and entertainment. Or just plug in an Atari 10K BASIC or Assembler language cartridge and the full power of the computer is in your hands.

Memory? 8K expandable to 16K. And that’s just for the ATARI 400 at a suggested retail of only $549.99.

The ATARI 800 gives you all that and much more.

User-installable memory to 48K. A full-stroke keyboard.

With a high-speed serial I/O port that allows you to add a whole family of smart peripherals. Including up to four individually accessible disk drives. And a high speed dot-matrix impact printer. And, the Atari Program Recorde is included with the 800 system. Suggested retail price for the ATARI 800 (including recorder) is $999.99.

Make your own comparison wherever personal computers are sold. Or, send for a free chart that compares the built-in features of the ATARI 400 and 800 to other leading personal computers.

ATARI PERSONAL COMPUTER SYSTEMS
1265 Borregas Ave. Dept. C, Sunnyvale, California 94086. Call toll-free 800-538-8547 (in Calif. 800-672-1404) for the name of your nearest Atari retailer.

view additional pages

VIC-20 – Commodore’s Entry in the Small Computer Arena

by David D. Busch

If first impressions stick, the Vic-20 microcomputer by Commodore (King of Prussia, PA) will lodge itself in the mind of any potential purchaser. The 6502 microprocessor-based computer just doesn’t look like a $299 machine.

In fact, when I demonstrate the unit to those unfamiliar with it, I always save the price for last. This ploy is especially effective if the potential user already has some familiarity with other microcomputers and their prices.

First, I demonstrate the full-stroke, typewriter-style keyboard, which features four special function keys and a control key. The Pet Basic is identical to that used in higher-priced Commodore machines and comparable to Applesoft or Radio Shack’s model III Basic. Lowercase characters are built-in, but the user can define any character set by using an 8-by-8 dot matrix. There are high resolution graphics (every dot on the screen may be addressed)—in eight colors. Need sound? Four voices are built in, and adding a joystick is as simple as plugging a stock Atari unit into a socket.

I then mention the price. “What’s the catch?” I am asked immediately. In truth, there are several. It is not really possible to do anything useful with the system for $299—not even save or load programs. It is necessary to add $75 for the Commodore Datasette cassette recorder. Ordinary tape recorders, which produce sine wave output, cannot be substituted for the square-wave Commodore unit.

Because the unit comes with 5K bytes of RAM and only about 3.5K bytes are available for user programs, it is necessary to purchase additional memory in order to use all of the features to their fullest capacity. For example, in the stock Vic-20, only a small portion of the screen can be manipulated in hi-res graphics. Defining a complete new character set leaves only a small amount of memory for programs. These tools can be best used when an additional $300 investment is made to expand RAM to its 32K-byte limit.

The final catch Is that the display is only 22 columns wide. This may also be remedied by add-ons and user programs. However, at a time when many micro users are complaining that 64-character screens should be 80 columns wide, a 22-character display seems less than adequate.

My feeling is that Vic-20 purchasers should appreciate the value they get for $299, but consider the unit for what it really is—a competent $600-$700 color microcomputer.

The company can easily be forgiven for the attention given to the keyboard while offering a less-than-perfect screen display. The screen display is relatively easy to modify with add-on components. Given the wide range of televisions likely to be used as monitors for low-cost micros and narrow bandwidths, Commodore opted to provide a sharp display that can be upgraded to suit the higher resolution of composite video monitors.

As a writer capable of 60-word-per-minute bursts, it was the keyboard that sold me. It’s a solid, professional-feeling unit that can accept input as quickly as any user can type. There is no keyboard bounce, and most keys have been laid out in a logical manner.

The biggest drawback is the placement of the RETURN (ENTER) key. It is at the far right of the home row, four keys removed from the L. I am most accustomed to the following layout: “J, K, L, semicolon, ENTER,” although one of the computers I use follows a “J, K, L semicolon, quotation mark, ENTER” format, both standard, typewriter-style layouts. The Vic-20 uses “J, K, L, colon, semicolon, equals-sign, RETURN.” As a result, the tendency is to hit the equals-sign key instead of RETURN.

It is relatively easy to learn this unusual layout and by the time I had written two or three programs, I rarely hit ” = ” by mistake. All other keys have logical or unobtrusive placement.

One welcome feature is the addition of four special function keys. These are marked F1, and so on, and by hitting SHIFT, are used to produce eight separate function keys. They are defined as CHR$(133) through CHR$(140), and are accessible to any Basic program. Business users and game enthusiasts will find special applications for these keys. For example, a menu may be designed instructing the operator to hit F1-F8 to invoke particular subroutines. Then, lines such as IF A$ = CHR$(133) GOTO 100 may be used. An alternative might be: ON VAL(A$) – 133 GOSUB 100,200, 300,400,500,600,700,800.

A large number of characters are available from the 61-key board. The machine powers up in Graphics mode and typing normally produces the uppercase characters and numbers shown on the keytops.

However, each key may also produce one of two graphics characters while in the Graphics mode. Two keys are located on the lower left side of the keyboard; one of two SHIFT keys is to the right, while a special key labeled with the Commodore logo is on the left. Striking the Commodore key and pressing another key produces the graphic character printed on the left side of the keyfront. Pushing the SHIFT key in tandem with another key produces the graphic character printed on the right side of the second keyfront. (Of course, either SHIFT key may be used, but it is easier for a beginner to stick to the one paired with the Commodore key.) The Vic-20 has a Text mode, and by pressing SHIFT and the Commodore key simultaneously, Text is invoked. The keyboard then functions as an ordinary typewriter with upper and lower case letters. Even so, the graphics on the left sides of the keyfronts (those most likely to be used in business applications) are still available by hitting the Commodore key.

That’s not all. Any of the characters available may be printed in any of eight colors, normally or reversed, by using a Control key. The Vic-20 prints its characters in blue until a color control key is pressed. The color keys are on the top row of the keyboard. CTRL-1 produces black characters, CTRL-2, white, and so on through red, cyan, purple, green, blue and yellow. Reverse On and Reverse Off are also summoned by using the control key. Once one of these has been entered, the display changes to the new parameters for all characters until the next control character is entered.

Vic-20′s Pet Basic does not have any graphics or color commands, such as Line or Fill, but I understand that the Super Expander cartridge will provide these capabilities. Graphics characters may be incorporated in programs through time-consuming, but easy-to-use PRINT statements. For example: 100 PRINT “(RVS ON)(CTRL-3) THESE CHARACTERS WILL BE PRINTED IN THE BACKGROUND COLOR ON RED”

110 PRINT “(RVS OFF) THESE CHARACTERS WILL BE PRINTED IN RED, OVER THE BACKGROUND COLOR.”

For the alpha characters, I could have substituted any of the graphics characters, but, of course, could not reproduce them for the printed page. In fact, the (RVS ON) and (CTRL-3) in the above lines actually appear on the Vic screen, replaced by graphics symbols that denote the function invoked. All screen controls are indicated in this manner—a reverse “Q” means cursor down, while a heart indicates clear screen. I found these symbols confusing at first. Unless you have a printer with graphics capability (Commodore offers one for the Vic-20 at $399), your program listings will be lacking all the needed information.

I found the screen display to be excellent. The unit connects to any color television through a supplied RF modulator. I tried the unit with seven different brands and had no trouble getting a sharp image. One exception was a 10-year-old television with a dirty tuner mechanism. Fine-tuning the TV, and, sometimes, moving the RF modulator to get rid of a residual moire effect produced an excellent picture. My test for picture quality involved the use of a high-resolution game, AMOK, a machine language program with a special character set that makes considerably greater demands on resolution than standard alphanumerics or graphics.

POKE generates color, sound, noise On some sets, color balance adjustments had to be made to clearly differentiate the eight available colors. Cyan tended to resemble green on a few units, while red often looked more brown or orange. To avoid constant plugging and unplugging, I have dedicated a 13-in. GE television to permanent Vic duty in my office. Until I receive the Super Expander cartridge and begin working more heavily with hi-res graphics, I see no need to invest in a monitor for the Vic.

The display area on the screen is surrounded by a colored border. Both the border and the screen may be changed to other colors with a single POKE statement, either in command mode or from a program. There are 255 color combinations available.

POKE may also be used to generate sound and noise. Three voices, each with a different three-octave range and a fourth white noise tone generator, are available. The Vic introductory guide includes programs to simulate 20 sounds, including laser beams and birds chirping. Some fine tuning on the television may be necessary to optimize the sound with picture.

Programs are loaded and run from the Pet Datasette cassette recorder. This unit is totally slaved to the CPU, deriving its power and on-off signals from the main unit. At 300 baud, it is a little slow, but I found the capability to use long file names extremely helpful. With Radio Shack cassette files, for example, one may CLOAD or CSAVE a file by single letter name—CLOAD A, for example.

The Vic-20 may be commanded to search for a more-detailed file name—LOAD CHECKBOOK 1982—for example. Or if the file name is not known for certain, a partial specification may be entered. LOAD CHECK would cause the Vic to load CHECKBOOK 1981, CHECKBOOK 1982, or CHECKERS, depending on which it found first. However, the system does tell you what files it has found as it passes through.

I have tried several programs that use the Atari joystick. At present, only a single controller may be used. AMOK, based roughly on the arcade standard Berserk, is a Roger Merrit product. Using the joystick, I was able to make the little man run through the maze with ease, zapping robots along the way. The joystick may be read from user programs through a simple PEEKing routine described by Commodore in its Programmer’s Reference Guide.

Although not tested, light pens and game paddles can also be used with the Vic. I see this machine, because of its low cost, becoming a popular games machine—like the Atari 400—with some serious capabilities as an added attraction.

Those are the current hardware highlights—disk drives, memory expansion and ROM packs. Other enhancements are on the way, but unavailable at press time.

Software base is firm From a software standpoint, the Vic-20 enters the field from an unusually strong position. All standard Pet Basic programs may be loaded and run, as long as ROM-dependent features (such as PEEK and POKE) are not used. Programs written for 40- and 80-column screens will cause material to wrap around the Vic’s 22-character display, but the user can usually remedy this minor annoyance.

Those who already know Pet Basic, or some other Microsoft variation on that theme, will find transition to the Vic painless. TRS-80 owners will be hard-pressed to note any differences at all—GETS in place of INKEY$ and FRE(X) for PRINT MEM are the two notable examples. Even file handling is very similar to Radio Shack’s Disk Basic. Files may be opened and closed, but the Vic-20 allows specification of a device number so that the same syntax may be used for either cassettes or disk data files.

Because of the common language, the Vic-20 should prove to be formidable competition for the Radio Shack Color Computer as a second computer for current model I or III owners.

As a long-time user of line-oriented program text editors, it took me several weeks to become accustomed to the Vic’s screen editing. With line editing, the programmer LISTS a section of the program, types in EDIT 20 (or whatever line is to be changed) and then makes changes. The Vic’s screen editor works in a very different way.

Any program line that appears on the screen may be edited by moving the cursor to that line, overtyping the text, or making insertions or deletions by hitting an appropriate key. Pressing RETURN makes the changes permanent. One may simply renumber a line by typing over the line number (the old version of the line remains and should be deleted).

Beginners to computing will find the guidebook, Personal Computing on the Vic-20, to be a clear, concise and helpful introduction. However, I have seen better Basic courses. The Commodore guidebook is more feature-specific and helps the new user discover the capabilities of the Vic-20 rather than serving as a thorough grounding in Basic programming.

Those already familiar with some dialect of Basic who choose the Vic-20 will find the introductory guide somewhat frustrating. It is difficult to sort through the elementary material to find the “meat” to help you make the switch. The guide is not at all detailed in helpful programming tricks. For example, I could find no reference to using the special function keys. I had to experiment and finally used GET$ to see what ASCII value was returned when the user pressed one of the special keys.

Serious programmers must make the purchase of the Vic-20 Programmer’s Reference Guide their number one priority. This volume not only contains all the material missing from the user’s guide, but has invaluable data I never expected to see. The reference guide contains techniques—with examples—that left me more impressed than ever with Vic’s capabilities.

Consider generating special character sets. There is a register in RAM that controls where the Vic gets its character set information. This location may be changed by hitting the shift Commodore Key, or by POKING to toggle back and forth between two ROM addresses which contain the Uppercase/full graphics or Uppercase-lowercase/partial graphics characters. These character sets may also be reversed. Because the characters are stored in ROM, it is obviously impossible for the user to change them. However, by POKING the RAM register which supplies the ROM addresses with a new location in RAM, it is possible to have the system derive its character information from a user-supplied table. Then, when letter A is printed, instead of A, the screen will display whatever character has been created by the user.

Or, most of the existing character set may be copied over from ROM to the RAM table, so that most keys still produce their ordinary output while others generate new characters. Each complete character set takes up 2K bytes of memory, so not much room is left for user programs with an unexpanded Vic.

The method for designing characters is simple to understand. Each is built on an 8-by-8 matrix, so that eight bytes (each containing eight bits) are needed. It’s easier to visualize this capability:
Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7 Bit 8
Byte 1 0 0 0 1 1 0 0 0
Byte 2 0 0 1 0 0 1 0 0
Byte 3 0 1 0 0 0 0 1 0
Byte 4 0 1 1 1 1 1 1 0
Byte 5 0 1 0 0 0 0 1 0
Byte 6 0 1 0 0 0 0 1 0
Byte 7 0 1 0 0 0 0 1 0
Byte 8 0 0 0 0 0 0 0 0

The above eight bytes, translated from binary and POKED to the desired location in the user’s character set, will produce the uppercase letter A. By placing X’s and O’s in a similar matrix, users can custom-design special languages, scientific symbols or flying saucers for games.

Machine language programmers who don’t like rewriting their codes to be compatible with every new ROM will appreciate Commodore’s dedication to the KERNAL concept. KERNAL, Vic’s operating system, contains a standardized jump table to the input, output and memory-management routines in the system. Should Commodore introduce new ROMs for the Vic (as they have done for the Pet), the KERNAL jump table will be changed to match new ROM locations for routines. Serving as a sort of forwarding address, it will allow programmers to address the ROM through the table, confident that JSRs will end up where they are supposed to—even if the ROM has been changed.

The Vic-20 will inevitably be compared with other computers in the low price range. I’ve owned a Sinclair ZX81, and have investigated both the TRS-80 Color Computer and the Atari 400, and can make some comparisons.

The most significant difference among the four is the keyboard. As a touch typist, I found the tiny Sinclair membrane keyboard almost impossible to use for long periods. The single key entry of most Basic keywords was of no help because I can usually type PRINT faster than I can hunt for the correct key on the ZX81′s tiny surface.

The Atari 400 keyboard is only slightly better. It is roughly the size of an actual typewriter keyboard, so the fingers may be positioned for touch typing. However, the flat keys provide no feedback, and it is possible to do only slow, methodical touch typing with it. The Color Computer’s calculator keys are better, but still not up to the full keyboard feel of the Vic.

Costs vary with power and equipment On the basis of price alone, the Sinclair is quite powerful for $150 ($99 as a kit), but its 32-character by 16-line CRT display is black and white only, and resolution may be spotty on a variety of televisions. Of course, the unit comes with just 1K byte of memory, and expanding to 16K bytes raises its price $100. That is still less expensive than the $299 Vic, which actually costs closer to $400 with the required cassette recorder included.

That makes the Vic similar in price to the $399 Color Computer, which may be used with a tape recorder in a pinch. The Atari, also $400, is supplied with 16K bytes of memory, which may make it a better deal if all factors were equal.

The Atari will display 24 by 40 characters, to the Color Computer’s 32 by 16, and Vic’s 22 by 23 (without expansion add-ons).

The ZX81 is now limited to 16K-byte memory, but the other three systems can be expanded to 32K bytes with memory boards supplied by either their manufacturers or outside suppliers. The three color computers can also use ROM packs.

As far as other peripherals go, the Color Computer has an early lead, because its disk drives are now available. Outside suppliers have also introduced accessories for the Color Computer’s expansion bus, which will make that unit very flexible should it remain in the Radio Shack line for a number of years.

Disk drives for the Vic have yet to be introduced, although one is promised. A printer is already available, and third-party suppliers offer RS-232 interfaces and other accessories.

As with any computer purchase, the final decision should be partially based on end-user requirements. On business trips, I carry a complete ZX81 kit in one pocket of my camera bag. For that application, small size and portability were paramount. Now I find the Vic-20 has its advantages. It is a low-cost color computer with a Basic that took me no time to learn. Because it has built-in lowercase and is portable, I may find some future word processing-on-the-road uses for it.

Others may prefer the Atari because an excellent selection of games is already available and the Color Computer might be the choice for some because of widespread Radio Shack support.

To date, support for the Vic from Commodore has been slow. Promised accessories and peripherals were two to three months late. My local dealer noted that he sold 50 units during the Christmas season, but would have been able to move 200 or more if more software and hardware had been available. The thoroughness of the Programmer’s Reference Manual is a good sign, and could indicate an exciting future for the Vic-20.

For a bit of a comparison, check out the ridiculous amount stuff crammed into a Texas Instruments OMAP 5 processor that’s designed for cell phones.

Also, you have to check out the picture of Roger Amidon’s computer “Spider” on the fourth page.

view additional pages

The First Ten Years of Amateur Computing

Sol Libes President, Amateur Computer Group of New Jersey
995 Chimney Ridge
Springfield NJ 07081

Most people I meet are under the mistaken notion that personal computing started only two or three years ago, with the introduction of the Altair 8800 by MITS. Nothing could be further from the truth. In fact, the amateur computing hobby was then almost ten years old.

I therefore decided to write this article to set the record straight, give credit to the early pioneers in this hobby and shed some light on the early history of microprocessors.

If one could find a specific date for the birth of personal computing, it would be May 5 1966. For it was on that date that Steven B Gray founded the Amateur Computer Society and began publishing a quarterly called the ACS Newsletter.

The newsletter exchanged information on where to get surplus computer gear, how to build not too complicated circuits, where to get integrated circuits, tips, experiences and where to get help. By the end of 1966, the Society reported that it had over 70 members.

1966 also saw the publication of the first books on how to build a home computer.

Typical was We Built Our Own Computers by A B Bolt and published by Cambridge University Press.

In January 1968, a survey in the ACS Newsletter reported that two amateurs had their home built systems up and running and that many others were actively working on their systems. The survey indicated that programmable memory sizes ranged from 4 to 8 K with some as high as 20 K, all magnetic core of course. Teletypes and Flexowriters were popular for IO. Clock speeds ranged from 500 kHz to 1 MHz, with the average 500 kHz. Most used discrete transistors, and a few reported using those new and hard to come by RTL integrated circuits. Instruction sets were small, ranging from 11 to 34 instructions. Word sizes were from four to 32 bits, with 12 bits the typical number. Registers ranged from two to 11, with three most common. Most reported that they had been working on their machines for about two years.

The April 1968 issue of Popular Mechanics reported on ECHO IV (Electronic Computing Home Operator), a home built computer constructed by Jim Sutherland. It had four registers, used a 4 bit word, had 8 K bytes of core memory, 18 instructions and a clock speed of 160 kHz.

In December 1968 Don Tarbell (now known for his high speed tape cassette interface) reported on his home built computer in the ACS Newsletter. It had a 4 bit word size, four registers, 10 kHz clock and was constructed using RTL integrated circuit logic. He used a Teletype for IO.

In 1967, Dave Digby ran an ad in CQ magazine offering a computer kit. It was advertised as featuring RTL logic, four registers, a 512 to 1024 byte delay line memory, and serial input and output. The price was $1000. As far as I know, he never delivered any units.

Most early builders constructed copies of the Digital Equipment Corporation’s PDP-8 minicomputer with their own modifications. In the surplus area, 1000 Minute-men I missile guidance processors became available in 1971.

1971 also saw the introduction of the first computer kit. It was part of the National Radio Institute’s course on computer electronics. It used 52 TTL integrated circuits, had a 32 by 8 bit integrated circuit memory, 15 instructions and an operator’s panel, and it sold for $503. Louis E Frenzel, then of NRI and now at Heathkit, was the designer.

In late 1971, the Kenback Corporation introduced the Kenback-1 computer for $750. It was intended primarily for educational use. It had a 1 K byte MOS shift register memory made by a small, young integrated circuit manufacturer called Intel. It also had three registers, an 8 bit word size, 65 instructions, operator’s panel, and an audio cassette for program storage.

The December 1971 issue of Computers and Automation described five home built computer systems. And by the end of the year 1971, there were reported to be 195 members in the Amateur Computer Society.

In 1972 things continued to pick up. In June Don Tarbell reported that he had written an editor program for his new home built system and was working on an assembler program. His system used an 8 bit word, 16 registers, and 4 K bytes of core memory.

Early 1972 saw the introduction of the 8008 microprocessor, by Intel, the opening of a number of used computer equipment stores, large price drops in TTL logic and the availability of the 1101 programmable memory at low cost. All of this proved to be a tremendous stimulus for amateur computer experimenters.

In the September 1972 issue of the ACS Newsletter Hal Chamberlin reported on his home built HAL-4096. This 16 bit machine utilized surplus IBM 1620 core memories. Hal furnished a complete set of construction plans for $2. The system had 16 registers, priority interrupt, Selectric and paper tape IO, and many other very advanced features.

The September 14 1972 issue of Electronic Design carried an article on how to build a circuit which would display 1024 ASCII characters on a TV set.

In 1973 amateur computing advanced in several areas. In May, the EPD company advertised the System One computer kit for $695. It had 1 K bytes of memory with expansion to 8 K and contained 82 integrated circuits. It had 57 instructions encoded in a diode matrix read only memory.

The September 1973 issue of Radio Electronics published Don Lancaster’s plans for the construction of the TVT-1. Although intended as a TV typewriter, many enterprising experimenters interfaced it to modems and home built computers.

In late 1973, the Scelbi Computer Consulting Company introduced the first computer kit using a microprocessor. The kit was called the Scelbi-8H and it sold for $565. It used the Intel 8008 and had 1 K bytes of integrated circuit programmable memory. It was expandable to 16 K bytes of programmable memory ($2760) and had options such as cassette IO, ASCII keyboard input, oscilloscope output and serial IO.

In 1973, Digital Equipment Corporation offered the PDP-8A with 1 K words of 12 bit programmable memory for $875. Also in 1973, a small publishing house catering to computer and digital electronics hobbyists began publishing with a book on wire wrap construction techniques. It was called M P Publishing Company and was a part time activity of Carl Helmers (who later began a monthly called Experimenters’ Computer System which after five issues was transformed into BYTE in 1975).

1974 marked a year of substantial increase in amateur computing. In July, Radio-Electronics magazine carried a construction article by Jonathan Titus on building the Mark-8 processor, which used the Intel 8008 microprocessor. It is estimated that over 500 of these units were built by avid experimenters.

In October, Southwest Technical Products Company (SwTPC) introduced the TVT-II kit for $180 and an ASCII keyboard kit for $40.

In September, Hal Singer started the Micro-8 Newsletter to exchange information among hundreds of experimenters who were building the Mark-8 unit.

In November 1974, Hal Chamberlin and some associates began another very popular but short-lived magazine called The Computer Hobbyist.

1975 was the year that personal computing exploded. It began, in January, when Popular Electronics carried an article on the Altair 8800 microcomputer by MITS. First deliveries were in April 1975. The kit sold for $375 and included 1 K bytes of programmable memory, but no IO. MITS claims that by the end of 1976 they had sold over 10,000 Altair 8800s (80% to hobbyists).

In April, the first computer club held its meeting. Started by Bob Reiling and Gordon French, and calling itself The Homebrew Computer Club, it met in Menlo Park CA. One month later the Amateur Computer Group of New Jersey was formed.

In the fall of 1975, MITS released its 4 K and 8 K BASIC interpreters, SwTPC introduced their 6800 based microcomputer, and the first decade of amateur computing was complete. Since then, the field as we know it today has rapidly matured and expanded.

Some Microprocessor History Intel Corporation must be credited with developing the microprocessor, the single chip integrated circuit which performs the basic functions of a central processing unit.

In 1969, a Japanese company, Busicom, contracted with Intel to develop a chip set for a printer-calculator. It used a 4 bit data bus and consisted of four integrated circuits in a set: a processor, read only memory with IO, programmable memory with IO, and a shift register type memory. Busicom permitted Intel to market the chip set for noncalculator applications, and the first generation of microprocessors was born.

The processor chip was designated the 4004, and it sold for $200. It came in an 18 pin dual in line package (DIP) and would interface only with the other chips in the family. Programs had to be stored in the erasable read only memory. Data and address information was multiplexed on the 4 bit bus. Since program could only be executed out of read only memory, and since progammable memory was used only to store data, debugging software proved to be difficult. Further, a great deal of support logic was required.

At nearly the same time, Datapoint, a manufacturer of intelligent terminals, contracted with Intel and Texas Instruments to produce a true processor on a chip. Intel succeeded in doing this. Unfortunately, the device proved to be too slow for Datapoint’s use. Intel decided, therefore, in 1971, to market the device for $200 and call it the 8008. It marked the first generation of “true” microprocessor integrated circuits.

The 8008 used an 8 bit data word with a more powerful instruction set than the 4004, but it still had many of the disadvantages of the 4004. It required considerable support logic. The 8008 however was a more general purpose device. For example, it contained a set of logical operations that the 4004 did not have. Its instruction set was similar to a minicomputer’s, and it could directly address 16 K bytes of programmable memory. It even had interrupt capability.

At the same time, Intel introduced the 1101, a 256 by 1 bit programmable memory (which enabled the experimenter to build a 1 K by 8 bit memory with only 32 integrated circuits!), and the 1702 256 by 8 bit EROM. With the 8008, 1101 and 1702 integrated circuits, general purpose computers could now be built.

In 1972 several other manufacturers recognized this emerging market. Most notable was National Semiconductor who introduced the IMP-16, a chip set which may have been a little ahead of its time. It was a bit slice system of variable word length and user definable instruction set. It later developed into the third generation Pace microprocessor.

In late 1973, Intel introduced the 8080 processor, and, soon after, Motorola introduced the 6800. The 8080 has become the de facto industry standard, used in more applications than any other processor. The 8080 is basically an enhancement of the 8008. It came in a 40 pin dual in line package and could directly address 64 K bytes of programmable memory and read only memory. It had a true bidirectional data bus and an expanded instruction set. However, it still required an external clock and multiple power supplies. The 6800 on the other hand required only one TTL compatible power supply, had simpler control circuitry, and an instruction set more compatible with larger computers.

1975 and 1976 saw the introduction of enhanced third generation microprocessors. The Zilog Z-80, an enhanced 8080, featured a larger instruction set, more registers, on chip clock, and more. The 6502, from MOS Technology, was an enhancement of the 6800. The Texas Instruments TMS9900 and TMS9980 became the first widely available single chip 16 bit microprocessors.

1977 marked the introduction of the fourth generation of microprocessors. In fact, these devices now could be called microcomputers in a single integrated circuit. These new devices include the complete microprocessor, read only memory, programmable memory, and IO circuitry on one chip. A minimum of support logic is required.

The future promises an increase in word size, functions, speed and memory capacity. (It looks like the single chip processor that runs BASIC may soon be a reality.) The next ten years in microprocessors and personal computing should be even more amazing than the past decade.”

a computer can get awfully bored when it can’t communicate!

So unless you’d prefer to have your computer sitting around cooling its chips, we’d strongly suggest you buy a couple of peripherals from Heath.

Why us? Because we make peripheral kits. In fact, they’re some of the best around. Our H9 is an excellent example. Its a complete ASCII keyboard/12″ CRT terminal that was designed for hobbyists just like you. It has a lot of really great features and resolution that’s just beautiful. Right on out to 80 characters per line. (Something most outboard TV monitors won’t match!) And with built-in selectable interfacing options, the H9 will “converse” with just about any computer going!

The H10 is another of our “universal” peripheral kits. Completely self-contained (it even has its own power supply), this rugged paper tape reader/punch gives you quick, convenient mass storage and internal tape duplicatior capability It’s easy to build and, with its heavy-duty stepper motor, sensitive Darlington photo transistors and precision punches, the H10 is a source of re liable data loading and storage – time after time.

Best of all, priced at $530 and $350 respectively,* the H9 and H10 kits cost less than most other comparable peripherals on the market today!

A computer can get awfully bored when it can’t communicate. Start communicating with yours through an economical peripheral from Heath!

Mail order, FOB. Benton Harbor, Michigan, Retail prices slightly higher.

Prices and specifications subject to change without notice.

HEATHKIT COMPUTERS

System Engineered for Personal Computing

H9 H10

view additional pages

Public Key Cryptography

An introduction to a powerful cryptographic system for use on microcomputers.

John Smith
21505 Evalyn Ave.
Torrance, CA 90503

Cryptography, the art of concealing the meaning of messages, has been practiced for at least 3000 years. In the past few centuries, it has become an indispensable tool in the military affairs, diplomacy, and commerce of most major nations. During that time there have been many innovations, and cryptography has changed and grown to accommodate the increasingly complex needs of its users. Present techniques are very sophisticated and provide excellent message protection. Current developments in computer technology and information theory, however, are on the verge of revolutionizing cryptography. New kinds of cryptographic systems are emerging that have incredible properties, which appear to eliminate completely some problems that have plagued cryptography users for centuries. One of these new systems is public key cryptography.

In public key systems, as in most forms of cryptography, a piece of information called a key is used to transform a message into cryptic form. In conventional cryptography this key must be kept secret, for it can also be used to decrypt the message. In public key cryptography, however, a message remains secure even if its encryption key is publicly revealed. This unique feature gives public key systems great advantages over conventional systems.

This article deals with the theory and application of public key cryptography. It reviews the methods and problems of traditional cryptography and describes the remarkable concept and advantages of public keys. It also describes a real public key cryptosystem, showing examples of the encryption and decryption operations; and it attempts to clarify the concept of trap-door one-way functions, upon which public key systems are based.

Computers are essential for implementing many modern cryptosystems, including the one described here. Several BASIC-language programs (TRS-80) are included to illustrate algorithms used in this system. These can be used to experiment with the encryption, decryption, and derivation of small keys.

Conventional Cryptosystems.

A cryptosystem must have two methods for transforming messages: a method of encryption, which renders messages unintelligible; and a method of decryption, for restoring them to their original forms. For simplicity, normal message text shall be called plaintext, and the encrypted form, ciphertext. Ciphertext messages may also be called cryptograms, or may just be called messages when it is clear that the encrypted form is meant.

To appreciate the significance of a public key system, we need to know some of the methods and problems of conventional cryptosystems. In a conventional system (see figure 1), a plaintext message is converted to a cryptogram by an encryptor and sent over a communication channel. While in transit, the cryptogram may be intercepted by someone other than the intended recipient. If it is encrypted well, it will be meaningless to the interceptor. At the receiving end, the cryptogram is converted back into plaintext by a decryptor. The encryptor and decryptor may be procedures executed by people or computers or may be specially constructed devices. In any case, they are both supplied with keys from a key source.

Cryptographic keys are analogous to the house and car keys we carry in our daily lives and serve a similar purpose. In many modern systems, each key is a string of digits. For example, keys defined by the Data Encryption Standard of the National Bureau of Standards consist of 64 binary digits, 56 of which are significant. To encrypt a message, a key and the message are somehow inserted into an encryptor, and the cryptogram that emerges is a jumble of characters that depends on both the message and the key. To decrypt the message, the correct key and the cryptogram are inserted into a decryptor, and the plaintext message emerges. In conventional systems, the correct key for decrypting a message is the same one used to encrypt it. Obviously, the keys used must be closely guarded secrets.

In a good system the number of possible keys should be very large, and decryption of any cryptogram should be possible with only very few of the keys, often with only one. These conditions make it impractical to try decrypting a message with one key after another until the one that reveals plaintext is found. The Data Encryption Standard provides more than 7 X 1016 keys (a 7 followed by 16 zeros), and there is some controversy over whether this number is sufficient!

The keys to be used are obtained from a key source, which selects them, perhaps randomly, from the large set of all usable keys. The key source may be located near the encryptor, near the decryptor, or elsewhere. But each key to be used must be made available to both the encryptor and the decryptor. Therein lies the most serious problem of conventional cryptosystems: some safe method must exist for distributing secret keys to the encryptor and the decryptor.

This problem is illustrated with a simple example: let’s say you want to communicate privately with a friend named Mary. Many communication channels are available to you, none of which may be completely private: telephone, mail, and computer networks, for examples. You could send encrypted messages, but Mary could not read them without the keys. And you dare not send secret keys over these public channels. One of you must visit the other, so that you could agree on a key to use for future correspondence. But if your communication need was for only one private message exchange, it could be transacted during the visit, rendering the conventional cryptosystem unnecessary. Or if your communication need were immediate, a personal visit could cause an unacceptable delay. And if you need to communicate with several people, all the necessary visits could entail considerable expense.

Most conventional cryptosystems, including the Data Encryption Standard system, have this problem. Public key cryptosystems, however, can avoid this problem entirely.

Public Key Systems.

The concept of public keys may be one of the most significant cryptographic ideas of all time. A public key system has two kinds of keys: encryption keys and decryption keys. It may seem that having two kinds would make the key distribution problem worse, or at least no better. These keys, however, have remarkable, almost magical, properties:

• for each encryption key there is a decryption key, which is not the same as the encryption key
• it is feasible to compute a pair of keys, consisting of an encryption key and a corresponding decryption key
• it is not feasible to compute the decryption key from knowledge of the encryption key

Because of these properties, Mary and you can use a public key system to communicate privately without transmitting any secret keys. To set it up, you generate a pair of keys, and send the encryption key to Mary by any convenient means. It need not be kept secret. It can only encrypt messages—not decrypt them. Revealing it discloses nothing useful about the decryption key. Mary can use it to encrypt messages and send them to you. No one but you, however, can decrypt the messages (not even Mary!), as long as you do not reveal the decryption key. Figure 2 illustrates the flow of information in this situation, with Mary on the left and you on the right. To allow you to send private messages to her, Mary must similarly create a pair of keys, and send her encryption key to you. You can also go a step further. Since your encryption key need not be kept secret, you can make it public, for example, by placing it in a computer network public file. Once you have done so, anyone who wants to send you a private message can look up your public key and use it to encrypt a message. Since you need not transmit the decryption key, and since it cannot be computed from your public key, the message is secure. Only you can decrypt it. Other people can place their encryption keys in the same public file, which would thus become a directory of public keys. Any two people with directory entries could then communicate privately, even if they had no previous contact. It would be necessary, however, to protect the keys in such a file so that no one could change someone else’s encryption key, for example, by substituting another encryption key. Fortunately, there is a way to protect the keys themselves with a public key cryptosystem, but that is another topic.

The RSA Cryptosystem.

Now that the general concepts of public key cryptography have been examined, the next problem is how to design an actual working system. Indeed, when Whitfield Diffie and Martin Hellman conceived the basic properties of this cryptosystem in 1976, no one knew how to make a system that could employ them. The situation was similar to that of space travel in 1950. It was conceivable, but no one had accomplished it. In 1977, three researchers at the Massachusetts Institute of Technology, Ron Rivest, Adi Shamir, and Len Adleman, published an elegant method for creating and using public keys.

In the Rivest-Shamir-Adleman (or RSA) cryptosystem, the keys are 200-digit numbers. The encryption key is the product of two secret prime numbers, having approximately 100 digits each, selected by the person creating the keys. The corresponding decryption key is computed from the same two prime numbers, using a nonsecret formula.

Anyone who knows the secret prime numbers can compute the decryption key, but the primes are hidden because only their product, the encryption key, is revealed. Of course, the primes may be discovered by factoring the key, but factoring such a number is about as easy as traveling to Alpha Centauri, especially if the person who constructs the number has done it in a way that discourages factoring. Rivest, Shamir, and Adleman estimated that a fast computer would require 3.8 billion years (nearly the estimated age of the earth) to factor a 200-digit key. Estimates of the time required to factor keys of several other lengths are shown in table 1.

Before encryption, a message is converted into a string of numbers. This step is common in cryptosystems, as it is in computers and communication systems. Next, the message is subdivided into blocks, much as computer text files are subdivided into records or sectors. Each block contains the same number of digits, and is treated as one large number during encryption. To encrypt the message, an arithmetic operation involving the encryption key is performed on each block, resulting in a cryptogram containing as many blocks as the original message. The arithmetic operation, described below, is the same for all blocks. To decrypt, the inverse arithmetic operation, which requires the decryption key, is performed on each block of the cryptogram. The result is the original message in its numerical form.

As you can imagine, it would be cumbersome to illustrate these operations with 200-digit numbers, so the detailed descriptions below use small keys and messages; otherwise, the operations shown are the same as those used in a full-size RSA system. Also, the encryption method described here is actually a subset of the original RSA method. This modification, which is due to Donald Knuth (see reference 3), uses the basic RSA technique, while lessening somewhat the number of computations involved. (For more detailed information, the reader should refer to the original Rivest-Shamir-Adleman paper, shown as reference 5.)

How to Encrypt.

While the encryption and decryption operations are normally performed by a computer program, I will describe them as if you were performing them by hand. Normally, the only manual operation required is entering the message to be encrypted.

Suppose you wish to encrypt the message

MARY HAD A LITTLE LAMB.

Once entered into a computer, the message will be in numerical form, frequently in ASCII (American Standard Code for Information Interchange). In ASCII, this message is

77 65 82 89 32 72 65 68 32

65 32 76 73 84 84 76 69 32 76 65 77 66 46

This is not yet encrypted, of course. It is merely written as a computer might represent it (all the numbers in this article are decimal). Group the message into blocks with six digits each:

776582 893272 656832 653276 738484 766932 766577 664600

Each block except the last consists of three consecutive characters from the ASCII representation above. The last block consists of the last two characters plus two zeros added at the right to make the final block as long as the rest. Digits added for this purpose may have any value.

Suppose that the encryption key, usually called n, is 94815109. This is the product of two prime numbers. To encrypt the message, treat each block as a number, and cube it modulo n (see the text box “Arithmetic with a Modulus”). For example, to encrypt the first block of the message:

(776582 X 776582 X 776582) mod 94815109 = 71611947

Performing the cubing operation on all eight blocks produces the cryptogram

71611947 48484364 03944704 03741778 61544362 35331577 88278091 50439554

Arithmetic modulo n is a fundamental part of the RSA system. It is also used in decryption and creating keys. Most of us have used arithmetic modulo n, although perhaps we didn’t call it that. For instance, arithmetic modulo 12 is frequently used in calculations related to keeping time. The text box “Arithmetic with a Modulus” reviews the mechanics.

Almost any method may be used to convert the text to numbers. It would have worked just as well to use A = l, B=2, . . . Z = 26, but the ASCII code is already in wide use, and it includes numbers for spaces and punctuation. The block length should be almost equal to the key length, because making it long minimizes the number of blocks per message. When considered as a number, however, no block should be as large as the key. For the above key, no block should be larger than 94815108. Making the block length slightly less than the key length ensures that this requirement is met. Of course, with full-length keys, there will be about 100 characters per block.

Listing 1 is a BASIC program that uses the above key to encrypt a line of text. Two lines of the program (670 and 680) perform the encryption. The rest deal with input, formatting, and printing. If desired, the encryption key in line 220 may be changed; use a key with seven or eight digits, or reduce the number of characters per block (line 210).

The programs in listings 1 through 4 were written for the TRS-80 BASIC interpreter, which is capable of 16-digit precision. They may be adapted for use with other interpreters, and I have tried to structure and annotate them well enough to make them easy to modify.

How to Decrypt.

Since the RSA system is a public key system, the decryption key, usually called d, differs from the public encryption key. For the above encryption key, d is 63196467. Knowing the value of d, you can decrypt the message by raising each cryptogram block to the power d, modulo n. That is, if a cryptogram block is C, you must compute (C) mod n. For example, to decrypt the first block of the above cryptogram:

(71611947^63196467) mod 94815109 = 776582

converts this block back to the first three ASCII codes of the original message. Each of the remaining blocks is decrypted in the same way. Fortunately, raising a number to a large power does not require performing a comparable number of multiplications. One efficient algorithm is a variation of the “Russian Peasant Method” of multiplication (see reference 4). It computes M = (C^d) mod n, as follows:

1. Let M = 1.

2. If d is odd, let M = (MXC) mod n.

3. Let C = (CXC) mod n.

4. Let d = integer part of d/2.

5. If d is not zero, repeat from step 2; otherwise, terminate with M as the answer.

To raise a number to the power 63196467, this algorithm executes its loop (steps 2 through 5) 26 times. It is employed as a subroutine in the BASIC-language decryption program of listing 2. Line 200 contains the keys, which may be changed, if desired. Lines 340 through 380 execute the algorithm.

How to Derive Keys.

Earlier, I said that it is feasible to derive a pair of keys, n and d, for encryption and decryption, but not feasible to calculate d from n. That seems incredible, but experts believe it is true when n and d are constructed in the following way.

The encryption key, n, is the product of two large prime numbers, p and q:

n = pq (1)

The decryption key, d, is calculated from p and q by

d = [ 2(p-l)(q-l) + 1 ]/3 (2)

Although n is made public, p and q remain secret. If n is sufficiently large, say 200 digits, it is practically impossible for anyone to factor it and discover the values of p and q; and without knowing p and q, it is equally difficult to compute d.

For the encryption and decryption examples given earlier, the keys were constructed as follows:

prime number, p = 7151 prime number, q = 13259 encryption key, n = 7151X13259

= 94815109 decryption key, d = (2X7150X 13258 + l)/3

= 63196467

Because p and q may have 100 or more digits in an operational RSA system, their selection requires computer assistance. The following three restrictions apply to how they should be chosen. First, neither p — 1 nor q — 1 must be divisible by 3, or the decryption operation will not work correctly. Second, p — 1 and q — 1 should both contain at least one large prime factor. Third, the ratio p/q should not approximate a simple fraction, e.g., 2/3, 3/4, etc., etc. These last two restrictions help ensure that n will be difficult to factor. Donald Knuth, in the second edition of his book (see reference 3), gives a detailed procedure for selecting p and q, which ensures that these restrictions are met. While the procedure described is for constructing 250-digit keys, it is applicable to other key lengths.

Enough keys are available for everyone. The number of 250-digit keys constructible with Knuth’s procedure is much greater than 10^200. For comparison, the number of atoms in the known universe is about 10^80.

To create a different pair of seven-or eight-digit keys, find primes p and q such that neither p — 1 nor q— 1 is divisible by 3, and the product n=pq is a seven- or eight-digit number. Then calculate d from formula (2). Divisibility by 3 is easily checked by casting out 3s, and the BASIC programs described below are helpful in finding prime numbers.

How to Find Large Prime Numbers.

To find a large prime number, select a random odd number of the required size and determine whether it is prime. If it is not, increase it (or decrease it) by 2 and try again, repeating until finding a prime. It is not necessary, however, to attempt to factor a number to determine whether it is prime.

To test whether a number n is prime, select any number greater than 1 and smaller than n, say x, and calculate

y = (x^n-1) mod n

If y is not equal to 1, n is not prime. But if y = 1, n may be prime, and further testing is required. Repeat the test using another value of x. If this test is performed with many different values of x, and if y = 1 for all the test cases, n is probably prime. Listing 3 is a BASIC program that uses 10 values of x to test a number for primality. If the program says the number is not prime, it is not prime. But if the program says the number is probably prime, there is a small chance that it is not.

What is the probability that this program will make an error? I don’t know, but it illustrates a class of programs, some of which are very good. Knuth (reference 3, page 375) presents one that is slightly more complicated, for which the odds against an error are a million to one when 10 values of x are used for testing, and are a million million to one when 20 values are used. For serious work I would use the more complicated program, but the one presented here illustrates the process of testing without factoring—and it doesn’t seem bad. It has not made an error in several hundred trials.

Listing 4 is a BASIC program that searches for a prime number using the same test method as the previous program. The program will begin with the number you enter and search downward until it finds a probable prime, which it will identify. If you enter 99999999, it will find the largest eight-digit prime. This program helps to find primes for constructing small keys like the ones above.

One-Way Functions and Trap-Doors.

Public key cryptosystems derive their unusual properties from mathematical functions called trap-door one-way functions, which are useful because they can act as ordinary functions or as one-way functions.

One-way functions are like oneway streets. The ordinary cube function, B = A3, resembles a one-way function in that it is easier to calculate B, given A, than it is to calculate A, given B. The latter calculation, the cube-root function, is called the inverse of the cube function. The inverse of an automobile would convert smog to gasoline. A mathematical function is said to be one-way if it is much more difficult to compute the inverse than to compute the function itself. To qualify as a one-way function, the inverse must be very difficult to compute, even by machine.

A function that could be computed in a few seconds, for which computing an inverse required thousands of years, would fit the definition.

To create a public key cryptosystem, a trap-door one-way function is used. It is easy to compute an inverse of a trap-door one-way function, but it can be very difficult to determine how. Computing an inverse can take millions of years because finding out how to do it can take that long. If the method is known, computing an inverse may take only a few seconds. This is a completely different situation than that created by a one-way function, for which there is no easy way to compute an inverse. When a trap-door one-way function is being constructed, the person constructing it has access to information, called trap-door information, that reveals how to compute inverses. Once the function is constructed, the trap-door information is hidden so well that it can take millions of years to find.

The Knuth modification of the RSA system encryption function, cubing a number modulo n, is a trapdoor one-way function. Its inverse function is the cube root modulo n. In arithmetic modulo n, “cube root” is defined as in ordinary arithmetic: if B is the cube of A, then A is the cube root of B. Notice that this definition does not say how to compute cube roots (in either kind of arithmetic). If you know how to compute cube roots modulo n, you know how to decrypt messages. In modulo n arithmetic, the cube root of B is computed by raising B to some power d, modulo n. But knowing this doesn’t help unless you know the value of d. And d can be computed by formula (2) if n has two factors (p and q), and p — 1 and q — 1 are not divisible by 3. If you construct the modulus, n, you know p and q, and can therefore calculate the value of d. Knowing d, you can compute cube roots; in other words, decrypt cryptograms. The values of p and q are hidden from other people by the difficulty of factoring n. They are deprived of the value of d, and therefore cannot compute cube roots. Hence, they cannot decrypt cryptograms created by cubing modulo n. In the RSA system, the value of d is the trap-door information that reveals how to compute inverses (cube roots). You might think of p and q as comprising a trap-door through which the value of d is obtained. Factoring n is analogous to finding the trap-door, but it is very difficult to do.

Other trap-door one-way functions undoubtedly exist, and these could be the foundations for other public key cryptosystems. For each of these systems, the same principles would apply. The creator of the system parameters would have access to certain trap-door information, which would reveal how to compute inverses. For everyone else, the trapdoor would be hidden, and for them the encryption function would be, in effect, a one-way function.

Is the RSA System Unbreakable?.

Successfully analyzing a cryptosystem, and being able to read its cryptograms without authorization, is called breaking the system. Theoretically, the RSA system can be broken by a determined analyst. Factoring the encryption key, or modulus, would do the trick, for then the decryption key could be easily calculated from formula (2), after which any message could easily be decrypted. However, factoring a key of the recommended length and construction does not seem feasible. Knuth gives a procedure for constructing a 250-digit key and considers it inconceivable at this time that such a key could be factored. Experts acknowledge that a breakthrough in the art of factoring large numbers would render the RSA system worthless but consider such a breakthrough extremely unlikely. Apparently, factoring large numbers is not a new problem, but one that expert mathematicians have attacked for centuries, and it is known to be very difficult.

Another way to break the system is to determine the value of d without factoring n. Although you can approach this problem in several ways, experts believe that none of them are likely to be fruitful.

Yet another method of breaking the system is to learn how to compute cube roots modulo n without knowing the value of d. Less seems to be known about the difficulty of doing this than is known about the difficulty of factoring n. At this time, no one knows how to compute such cube roots in a reasonable time without knowing d.

Any new cryptosystem should be viewed with suspicion. The accepted method of demonstrating the adequacy of a new system is to subject it to prolonged, concerted attack by people with experience in breaking other systems. If the new system proves resistant to such an attack, it may tentatively be considered secure. The process of validation is continuing, but a fairly large number of preliminary studies done so far indicate that the system is quite secure.

Digital Signatures.

Very closely related to public key cryptography is the concept of digital signatures. One problem with corresponding electronically, such as via a computer network, is that messages can be easily forged—you usually cannot be certain that the sender of a received message is actually the person claimed in the message. A public key cryptosystem, however, can be used to provide positive identification of any sender who has a public key on record. If, for example, Mary has filed a public key in some public access file, she can digitally sign a message to you by decrypting it with her private key before transmitting it. After receiving the message, you (or anyone else) can read the message by encrypting it with Mary’s public encryption key. The process is essentially the reverse of the cryptosystem: the message is first decrypted and then encrypted, and anyone can reveal the message, but only Mary with her secret decryption key can create it.

In addition, messages using digital signatures can be subsequently encrypted with another key. After Mary decrypts her message to you with her secret decryption key, she can then encrypt it with your public encryption key. The result is a message that only Mary could have created, and only you can read!

Messages with digital signatures have other interesting and useful properties and may be used to advantage with other (non-PKC) cryptosystems. These properties and applications might easily justify an article on digital signatures alone.

Summary.

This article has described the principles of public key cryptosystems. One example has been given, the Rivest-Shamir-Adleman system. We have seen how keys are constructed and used, and have at our disposal four BASIC programs for further experimentation. These programs may also be useful as models for assembly-language programs that could manipulate larger numbers and run faster. We have seen that the RSA cryptosystem provides public keys in more than astronomical quantities and that it is believed to be unbreakable.

Several questions come to mind: Is a personal computer powerful enough to run a full-size RSA system? How long would a small computer take to construct a 200-digit key? Or even a 100-digit key? How long would it take to decrypt a medium-length message?

Regardless of the answers to these questions, the prospects are good for using public key systems with small computers. New computer models appear almost monthly, and their performance is improving rapidly. The theoretical work that gave birth to the RSA system is also proceeding at a rapid pace, and we can expect new and different public key systems to result from that work. Some of these may be suitable, perhaps even optimized, for small machines, and the prospects are exciting.

view additional pages

The Apple Macintosh Computer

Mouse-window-desktop technology arrives for under $2500

by Gregg Williams

Apple established itself as one of the leading innovators in personal computing technology a year ago by introducing the Lisa, a synthesis and extension of human-interface technology that has since been widely imitated. Now the company has strengthened that reputation with a new machine, the Macintosh (above). In terms of technological sophistication and probable effect on the marketplace, the Macintosh will outdistance the Lisa as much as the Lisa has outdistanced its predecessors.

The Macintosh arrives, finally, after a history of colorful rumors. It will cost from $1995 to $2495, weighs 22.7 pounds, and improves on the mouse-window-desktop technology started by the impressive but expensive Lisa computer. A system with printer and second disk drive costs about $900 more, but even at that price, the Macintosh is worth waiting for.

The Macintosh at Work

Before we look at the Macintosh (or Mac) in more detail, let’s look at how it works. When you turn the Mac on, its screen tells you to insert a 3-1/2-inch Sony floppy disk. When you do that, the Macintosh puts a disk icon on the screen along with the disk’s name. As with the Lisa computer, you first select an object, then choose a menu item that works on the object. Say, for example, we choose the disk by moving the cursor to the disk icon and clicking the mouse button once (figure la). The disk “opens up,” showing a window containing icons, each one of which corresponds to an item on the disk. To start using the Mac Paint program, we select the Mac Paint icon and choose the menu item “open,” as shown in figure lb. (We also could have opened Mac Paint by double-clicking on the icon.) What follows is a brief example of how the Mac Paint program works. When we open the program, we get the screen of figure 1c. The large blank area is a window onto the drawing area, the boxes on the left are tools, the boxes on the bottom row are patterns, and the lines in the corner are selections for the current line width. By selecting the “open oval” tool and the thickest line width, we can draw empty ovals with thick borders (figure 1d). By selecting the “paint bucket” tool and the “diagonal bricks” pattern, we can fill the oval with that texture (figure 1e). The “eraser” tool lets us erase part of the image (figure 1f); for finer control, we can give the FAT BITS command (figure 1g), which allows us to erase or paint on a pixel-by-pixel basis. When we are finished with our image and select the QUIT command, the program displays an alert box that asks if we want to save our changes (figure 1h).

Foundations of Macintosh Design

The Macintosh computer is built on three cornerstone ideas: second-generation Lisa technology, reliability and low cost through simplicity, and maximum synergy between hardware and software. Each of these ideas contributes significantly to the uniqueness of the Mac’s design.

Second-Generation Lisa Technology

Without question, the strongest influence on the Mac is that of the Apple Lisa computer, which proved the viability of certain concepts in a commercial product: the graphics/ mouse orientation, the desktop metaphor, the data-as-concrete-object metaphor, and the shared user interface between programs. The Mac has inherited these concepts; for further details on them, see my article, “The Lisa Computer System” (February 1983 BYTE, page 33).

Four differences between the Lisa and the Mac make the latter a second-generation computer. First, the Mac runs at a higher clock speed, 7.83 MHz (compared to the Lisa’s 5 MHz). Second, the Mac, which has a smaller amount of memory to work with than the Lisa, uses its memory more efficiently because its programs and subroutines are coded in 68000 assembly language (as opposed to the Lisa, which uses less efficient 68000 machine-language programs that are compiled from high-level Pascal source code). Third, the Macintosh eliminates add-on peripheral cards and uses instead a highspeed serial bus that implements what Apple calls “virtual slots.” (I will talk about this in greater detail below.) The final difference is actually an important limitation of the Macintosh: it allows only one major application program to be active at a time (the Mac BASIC and “desk ac- cessory” programs are two exceptions that I’ll cover later). This limitation is largely due to the Mac’s small memory space and the overall design of the software, which assumes that the current program has access to all the machine’s memory. This is not as bad as it sounds; a single application can use multiple windows, and material can be cut and pasted from one document to another by storing the material to be pasted on a “clipboard” before loading in the second document (which replaces the first). Still, the absence of hardware slots and the inability to run two applications simultaneously are two important ways in which the Macintosh is fundamentally different from the Lisa computer.

Reliability and Low Cost through Simplicity

Although the Macintosh costs approximately one-third the price of a Lisa, the Mac has much more than one-third of the Lisa’s power. The idea of reliability through simplicity not only makes the Macintosh possible at a relatively low price but also produces a machine that has a reliability normally associated with much simpler computers.

One component of the Mac’s simplicity is its low chip count—it contains about 50 ICs (integrated circuits), which decreases its physical size and price and increases its reliability. Mac reduces its chip count by combining the functions of many standard chips into eight programmable-logic arrays (PALs).

The Macintosh has only two circuit boards, one that holds all its analog circuitry and one that holds all its digital circuitry (see photos 2a and 2b). By partitioning its functions and reducing the number of connectors (by decreasing the number of boards to be connected), the designers have made the Mac both more reliable and less expensive. They carried this philosophy farther by eliminating hardware slots; you add peripherals to a Mac through its two high-speed serial ports.

The Macintosh was designed to reduce (or, in the case of the digital board, eliminate) the number of places in which hardware must be fine-tuned during assembly. In some cases, the designers eliminated the need for adjustment through clever circuit design, which also means there’s one less thing to go wrong with the computer once it is in the owner’s hands. In other cases, Apple eliminated fine-tuning by requiring a vendor of externally manufactured subassemblies to tune the part before delivery; for example, the video-display tube and yoke are delivered pre-adjusted, and the Sony 3V2-inch disk drive is delivered tested and with several Apple-specified modifications.

Maximum Synergy between Hardware and Software

The Macintosh’s hardware and software were optimized for maximum performance. This means that the hardware and software evolved over a period of time in a process of mutual give and take. For example, the pixels displayed on the Mac’s video display are square (not rectangular, as in other computers); this greatly simplifies the software that draws squares and circles, scales text and graphics, and prints screen images.

Hardware

The main unit of the Macintosh consists of eight parts: two circuit boards, a cable to connect them, a metal chassis, a 3-1/2-inch disk drive, a video-display tube with yoke, and a plastic front bezel and rear housing (see photos 3a and 3b). An external mouse and keyboard make for a total of 10 parts. The main unit takes up an amazingly small 10-inch by 10-inch area (it is 13% inches high). True, the keyboard and mouse take up more area than that, but the footprint of the main unit is considerably smaller than that of comparable com- puters. The Mac is also pleasantly compact and light; an entire Mac system in an optional padded satchel weighs 25.6 pounds (less than many transportable computers) and can be carried onto an airplane.

Figure 2 shows a block diagram of the Macintosh hardware; for more details, see the “Macintosh System Architecture” text box. For now, let’s look at the machine’s major subassemblies: Processor: The Macintosh uses a Motorola 68000 processor running at 7.83 MHz.

Video display: The Mac has a 9-inch monitor that displays a noninterlaced image at 60.15 Hz. The resolution of the video image is 80 pixels per inch, so the overall screen is 512 by 342 pixels.

ROM: The Mac uses two 256K-bit ROMs configured as 64K bytes of memory. The ROM (read-only memory) contains most of the Mac’s operating system and a “toolbox” of optimized 68000 user interface related routines (see the text box “The User Interface Toolbox” for more detail). The ROM is always accessed at full speed, 7.83 MHz.

RAM: The Mac has 128K bytes of memory; at some point (Apple says by the end of 1984), this will be expandable to 512K bytes (by substituting 256K-bit dynamic RAM (random-access read/write memory) chips for the 64K-bit chips currently being used). The screen display uses 21,888 bytes and is drawn using this memory and DMA (direct memory access) circuitry. Apple has an un- disclosed proprietary technique for phase-locking the 68000 to less expensive memory, which lowers the product cost without sacrificing the speed of memory access.

When the Mac is drawing a horizontal line of the video display, the 68000 and the video DMA circuitry alternate (interleave) their accesses to the RAM address and data lines.

Since these two can never access RAM simultaneously, the 68000 can never produce hashing or other glitches in the video display by accessing RAM at the wrong time. Because of this interleaving, the 68000 accesses RAM at 3.92 MHz, half of the full 7.83 MHz rate, during the display of a horizontal line of the screen. This is done in the following way: the DMA circuitry puts a word from RAM into the video shift register; while the register is sending out those 16 bits serially to the screen, the 68000 uses RAM for its own purposes; then the cycle begins again with the DMA circuitry.

When the video display is doing a horizontal or vertical retrace, however, the 68000 gets exclusive use of the RAM at its full speed, 7.83 MHz. This has a significant effect on the average speed of RAM access. Out of the 45 us (microseconds) for each horizontal display line, over 12 us (about 27 percent of the time) are occupied by horizontal retrace. Of these 12 us, about 0.5 us is used to send data to the sound and disk-speed circuitry, while the rest is available to the 68000. Furthermore, out of the 16.626 ms (milliseconds) used to draw each complete screen, 1.258 ms (about 7.6 percent of the time) are devoted to vertical retrace. Of this, about 14 us are used for sound and disk-speed control (representing the control work done at the end of the equivalent of 28 unused horizontal lines of video), leaving more than 1.244 ms for the 68000 to access RAM at full speed.

To summarize, the ROM is always accessed at 7.83 MHz, regardless of screen display. The RAM is accessed at 3.92 MHz during screen display and at 7.83 MHz otherwise. The average speed of the system is around 6 MHz.

One memory area of interest is the sound buffer. Along with associated hardware, this buffer enables you to create four channels of arbitrary sound while using no more than 50 percent of the 68000′s computing power. The 68000 performs look-up operations every 44 us on up to four 256-byte waveform tables; the result of these lookups is placed in a 370-byte sound buffer, from which the sound hardware fetches 1 byte every 44 us to deliver to an 8-bit digital-to-analog circuit (DAC). An internal VIA (versatile interface adapter) can also be used to generate a single square-wave tone while using an insignificant part of the 68000′s computing power.

Mass storage: The Macintosh uses a custom version of the Sony 3-1/2-inch disk and drive (see photo 4). The drive can store 400K bytes on a single-sided 3V2-inch disk; the Mac is designed to be able to use double-sided drives to get 800K bytes per disk, an option that Apple may pursue at a later date. The standard Sony 3-1/2-inch disk (used to date by Hewlett-Packard and other vendors) puts 70 tracks of data at 135 tpi (tracks per inch) onto each disk. At Apple’s urging, Sony now makes the drive in another model that has 80 tracks of data at 135 tpi. As a comparison, the Hewlett-Packard HP 150 uses the 70-track version and conventional sectoring to get 270K bytes per single-sided disk.

In addition to the change to 80 tpi, Apple contracted Sony to modify the drive in several other ways. Two changes allow the Sony drive to mimic the behavior of the Lisa “twiggy” drives (which were originally chosen for use in the Mac): disk ejection under software control and variable disk-rotation speed. The first change allows the Mac to ensure that a disk is correctly updated before it is surrendered to the user (that is, you can’t take a disk out of the drive until the Mac software permits it). The second change enables the Mac to record onto the disk at a constant linear density (which means you can put more data on the outermost tracks), as opposed to the constant radial density approach most computers use (which puts the same amount of data on each track regardless of position).

The Macintosh’s drive rotates under software control between 390 and 600 rpm (revolutions per minute) and transfers data at the rate of 489.6K bits per second (bits as recorded on the disk, not decoded data bits). Most computers use a disk-controller chip instead of the processor to control the drive. The Mac (like the Apple II) uses its processor to directly control the drive. Because the Macintosh can control more disk-related parameters than the Apple II (the variable motor speed, for example), Macintosh owners will be treated to an even greater wealth of copy-protection schemes than Apple II owners enjoy. Also, the Macintosh drive uses modified group code recording to encode data onto the disk. This technique, invented by Steve Wozniak for use with the Apple II, encodes 6 bits of data into an eight-transition group that is recorded onto the disk surface.

Keyboard: The keyboard has 58 keys; the left Shift key is split on the international version of the Macintosh, giving it a total of 59 keys. The keyboard includes Return, Caps Lock, and Shift keys in their usual places, two Option keys, and a cloverleaf command key (see photo 5). Combinations of the Shift, Caps Lock, and Option keys give each key up to six meanings; the command key acts as a modifier and is often used with a letter key as the keyboard substitute for a mouse-selected menu item. The keyboard contains an 8021 microprocessor and is connected to the main box by a four-wire bidirectional serial connection. The connections on both ends use the same kind of square modular plug found in most telephones.

Mouse: The Mac’s one-button mechanical mouse, about the size of a pack of cigarettes, is essentially the same as the Lisa’s; it differs only in the shape of the plastic housing. The mouse is used to position the cursor on the screen; when you slide the mouse over a horizontal surface, the cursor moves in the same direction on the screen.

Serial bus: The Macintosh’s serial bus is very important because it is the way that most future peripherals (except the second 3-1/2-inch disk drive and the keypad) will connect to the computer. The bus can run in two modes: with an external clock, it can transfer data at up to 1 megabit per second; with internal clocking (which embeds clock bits in the data stream itself), it can transfer data at up to 230.4K bits per second. The latter scheme will be used to connect most peripherals, which need only a low to medium data-transfer rate, to the Macintosh in a passive daisy-chained line. This scheme implements what the Mac’s designers call “virtual slots.”

Virtual slots have several advantages over conventional hardware peripheral slots. They reduce the potential problems inherent in any added mechanical connection (a serial interface connector has fewer pins than a typical interface board). They reduce RFI (radio-frequency interference) by keeping the main box leakproof and allowing easy, inexpensive shielding of the serial line. By deciding that peripherals will supply their own power, the Macintosh designers were able to streamline the power supply of the main box without worrying about the power needs of unspecified future peripherals. Finally, virtual slots eliminate the need of peripheral cards to insert themselves somewhere in the computer’s memory map; the unchanging memory map creates a known, unchanging system architecture that all software designers can be assured of, regardless of the peripherals connected.

The virtual-slot scheme is both practical and elegant; it offers a simple, standard way to connect unspecified future peripherals. The 230.4K bit-per-second data-transfer rate is high enough to meet the needs of most peripherals—printers, modems, plotters, music synthesizers, and so on. However, one class of add-on card will not work using this scheme: processor cards like the Microsoft Softcard, which allow a computer to run another processor’s software. Such cards require full access to the data and address lines and will not work via a serial “virtual slot.” As a result, despite some rumors to the contrary, the Macintosh will never use IBM PC- or MS-DOS-based software.

Power supply: Apple designed two power supplies for the Macintosh. The first one uses a 60-watt switching power supply similar to one used in the Apple II family; it can operate on 85 to 135 V AC at either 50 or 60 Hz. For technical reasons, use of this power supply would have delayed the introduction of the machine, so Apple designed and produced a simpler nonswitching power supply (105 to 130 V AC, 60 Hz) for initial use in the first U.S. models of the Macintosh. The first switching power supply will be used later in the year for the international model and possibly for the U.S. model.

The supply was designed to drive two twiggy disks; when the design was changed to include two 3-1/2-inch disks instead, the supply had a sizable margin of unused power.

System Software

As stated before, the Macintosh contains 64K bytes of ROM accessed at 7.83 MHz. The ROM contains most of the Mac operating system and a set of optimized 68000 routines called the Macintosh User-Interface Toolbox. The operating-system software interacts at the lowest level with the hardware; it includes such things as device drivers and memory- and file-management routines. The toolbox contains various routines that let you manipulate windows, text, the mouse, pull-down menus, desk accessories, dialogue boxes, fonts, and other aspects of the Mac user interface. These are high-level routines that perform the details of such complicated operations with minimum programming on the application designer’s part. For example, the window-management routines take care of correctly redrawing the display when a window is moved or changed. For more details, see the text box “The User-Interface Toolbox.”

The designers intend for you to access all ROM routines indirectly via the 68000 “line 1010 unimplemented” instructions, which receive their addresses from a table in RAM; this table can be changed to point to other routines, thereby allowing future versions of Mac software to patch the inevitable bugs that will be found in the Mac ROM. Because the application drives the ROM routines (instead of the other way around), the Macintosh is an “open” system whose behavior is completely determined by the contents of the disk inserted into it—that is, software designers can use the ROM routines to create a “standard” Macintosh application, or they can write their own code to create an application that behaves the way they want it to.

Although the designers of the Macintosh have a general philosophy of allowing only one application program to be open at a time, they have included in the main menu a collection of short, useful programs that can run without forcing you to end your current program. Apple calls these programs desk accessories. Many of the accessories are simply conveniences—the clock accessory, for example, shows you the current date and time—but a very powerful accessory is called the scrapbook. Ordinarily, you can cut and paste data from one document to another by cutting the data into the clipboard, loading in the new document, and pasting in the data; this process would be tedious if you had several items of the same type to cut and paste. The scrapbook is a sequence of data items—text or graphics—that can be stored or recalled together, thus minimizing the number of document changes and allowing you to recall often-used data items easily. The scrapbook is actually implemented as a disk file; as a result, it tends to be rather large.

System software reacts to all peripherals on an asynchronous basis-peripherals compete for the attention of the 68000 by sending it interrupts, which the 68000 services according to the level of the interrupt. This keeps the 68000 from being tied exclusively to a peripheral—for example, to the 3-1/2-inch disk drive waiting to get up to its full speed—when it could be doing something more useful. The Mac’s designers have managed to do this even with high-speed peripherals that usually require the full attention of a processor. For example, disk and serial-port routines have been dovetailed to permit the use of both peripherals at the same time.

Disk Reliability

Reliability was one of the main reasons that Apple decided to use the 3-1/2-inch Sony disk drive instead of the 5-1/4-inch twiggy drive. (A projected shortage of twiggy drives was another reason.) Apple is expecting the Macintosh to be the first real consumer-oriented computer, and it sees the magnetic medium as being more likely to fail than the electronics. The Sony 3-1/2-inch disk is better suited to the consumer environment. The drive can hold an acceptable amount of storage per disk, and the small disk, with its rigid shell and normally closed access window, is less likely to suffer from bad handling than a conventional 5-1/4-inch floppy disk. In addition, the magnetic medium is connected to a steel hub that the drive mates with and rotates. This is an improvement over 5-1/4-inch floppy-disk drives, which clamp the Mylar edge of the center hole. The 3V2-inch disk hub is needed to get accurate enough disk-head placement to make a data density of 135 tracks per inch possible.

The data on the disk is encoded in a way that enables the Macintosh to recover from some disk medium or disk file errors. The file directory is duplicated in a normal disk file (which can be used if, for some reason, the directory is damaged). Also, each block of data on the disk includes a 12-byte identifier that gives the file number, sequence-within-file number, and date/time stamp for the data in the rest of that block; this can be used in many situations to recover most or all of the data on the disk.

Applications and Languages

Neither application software nor a language is included in the basic Macintosh package. However, a two-program set will be available for $195; both programs require the recently introduced Imagewriter printer to print things out. The first program is Mac Paint, the drawing program we looked at earlier. Created in house at Apple, Mac Paint is limited to drawings that will fit on one 8-1/2- by 11-inch page. Mac Paint is unlike the Lisa drawing program (Lisa Draw) in that it manipulates the drawing on a bit-by-bit level (a Lisa Draw drawing is stored as a collection of elementary objects—circles, text, boxes, etc.). This representation makes some things, such as arbitrary erasures, easier on the Mac and other things, such as deleting a single object within the drawing, harder.

The second program in the set is Mac Write (figure 3), which was created out of house for Apple and can handle documents up to 10 single-spaced or 20 double-spaced pages. Like Lisa Write, Mac Write can handle multiple fonts and sizes as well as variations achieved by adding any combination of five modifiers-underline, bold, italic, outline, and shadow.

Apple Macintosh Pascal, Assembler/Debugger, BASIC, and Logo will cost $99 each; the first two will be available during the second quarter of 1984, and the other two will follow in the third quarter. The Logo is from LCSI, which developed Apple II Logo. Both the BASIC and Pascal compile on a line-by-line basis into an intermediate pseudocode, which gives them the speed of compiled languages while retaining the interactive nature of interpreted languages. Both languages use separate windows for program source code and output, and both can be debugged on a line-by-line basis. Both have graphics and mouse commands that call on the toolbox routines in ROM, and both use floating-point arithmetic routines (in RAM) that meet the IEEE-754 floating-point standard.

Mac Pascal, which was created out of house, is interesting in that it is the only Pascal I know of that can be executed interactively. Another nice feature is its syntax checker, an item that can be called from its “Run” menu. This menu item is often handy for finding those petty syntax errors to which Pascal code is prone.

Mac BASIC was created in house by Donn Denman, who worked on Apple III Business BASIC. An interactive, multitasking BASIC, it can execute multiple copies of the same program or multiple programs simultaneously; each program and each running task has its own window.

Other Apple programs announced for delivery in 1984 include Mac Terminal (which emulates the DEC VT-52 and VT-100 and Teletype ASR33 terminals—available first quarter, $99). Also planned are Mac Draw (an object-oriented drawing program) and Mac Project (a scheduling and project-management program). These are both Macintosh versions of two Lisa application programs; each costs $125 and will be available in the third quarter of 1984.

Third-Party Software

Apple has not spent all its energy trying to write all the software that the Macintosh needs. Instead, it has created two exemplary Macintosh packages and gone to third-party software developers to get them to create the bulk of available Macintosh software. Apple estimates that by the time you read this, the Mac will be in the hands of more than 100 software vendors.

At the time this was written, some software developers had made commitments to market Macintosh software. Microsoft Multiplan and BASIC will be available at the Mac’s introduction; Microsoft File, Chart, and Word will be available by mid-February. Lotus is working on converting its popular 1-2-3 spreadsheet program. Software Publishing Corporation will have its PFS File and PFS Report programs available sometime in April.

Optional Hardware

The Macintosh uses Apple’s new $495 dot-matrix Imagewriter printer, the only printer that is supported by the current print driver within the Macintosh. To get its level of graphics and text quality (see listings la through 1c), the Imagewriter usually stays in a graphics mode that prints a single column of dots for every byte sent to it by the Mac. However, the Imagewriter can print text in three modes: a high-resolution mode (listing 1b), a medium-resolution mode (listing 1c), and a draft mode that uses the printer’s built-in character set for quick text-only printing. (I found I prefer the medium- over the high-resolution text.) Although the Imagewriter could hardly be called fast, it is not unacceptably slow, and it is considerably faster than the Apple Dot-Matrix Printer running under the Lisa computer’s parallel port.

Two other pieces of hardware are an external disk drive (at $395, available during the first quarter) and a numeric keypad ($99, at introduction). The external disk driver connects to the main unit via a dedicated “second disk” connector in back. When the keypad is connected, the keyboard line runs from the Mac, through the keypad, and into the keyboard itself. Another product, announced but not scheduled, is external hardware that will give the Mac IBM 3270 emulation capability.

Documentation and Training

In its ads, Apple is stressing the necessity of going to a Macintosh dealer and trying the computer out. Once you have bought it, though, you will probably be learning how to use the Mac on your own. Apple will help you in this process by providing you with a cassette/disk combination. You boot up the 3-1/2-inch disk tutorial and listen to the interactive lesson provided on the cassette. (Of course, you have to have a cassette player.) Although I have not seen the cassette/disk tutorial program, I think it will work well; text-only tutorial programs are fine, but many buyers of the Mac will benefit from the warmth of a human voice teaching them.

I saw final-draft copies of only two Macintosh product documents. Explore Mac Paint is a booklet (about 25 pages) that teaches you about Mac Paint by showing you what it does. It is very easy to read because it has more pictures in it than text. Mac Write is much longer and looks more like conventional documentation. It is sensibly divided into three sections : “Learning Mac Write” (a do-by-example tutorial that shows you most of the features of the program), “Using Mac Write” (a “cookbook”

showing you how to accomplish many common tasks), and “Reference.” All in all, the documentation should be quite good.

Service

The Macintosh has no user-serviceable parts. Unlike the Lisa computer, the Mac is not meant to be opened by the user; you are expected to return your Mac to an authorized Apple service center for repair. The Mac comes with Apple’s standard 90-day parts-and-labor warranty. You can also buy a one-year maintenance contract. According to Apple, other service plans will be available, including options for large-volume purchasers of the Macintosh.

Caveats

I wrote this article after two days of meetings with various members of the Macintosh staff, studying preliminary Mac documentation, making numerous phone calls to Apple, and working for several days (over a period of weeks) with a Macintosh computer. I used several final-draft versions of Mac Write and Mac Paint, though I occasionally found operating-system features that “crashed” the system or weren’t yet implemented. Apple was still making minor changes to both software and pricing when this was written.

Commentary

There is a lot to like about the Macintosh; it is a superb example of what American technology can do when given the chance. The simple, compact, economical design, the virtual slots, and the enhanced performance of 128K bytes of memory because of the 64K-byte ROM code are all important innovations done well.

I’m glad that Apple decided to go with a Sony 3-1/2-inch disk (as compared to the Lisa 1, which needs special, expensive, hard-to-get twiggy floppy disks). However, I’m disappointed that both Apple and Hewlett-Packard have used nonstandard formats that are incompatible with each other. It would have been nice to start the widespread use of the Sony microfloppy with a standard disk format, but the incentive to sacrifice standardization for performance is one of the drawbacks of a competitive industry.

I also feel strongly that the basic Macintosh package should include two disk drives. With a one-drive system, it will take at least eight disk swaps to back up a 3-1/2-inch disk. How many people (especially novices) will go to this trouble, and how many will suffer when they don’t? (I am not alone in feeling this way; the first thing two BYTE editors said when they first saw the Macintosh was, “Only one disk drive? You’ve got to be kidding!” After numerous disk swaps when trying to load Mac Paint from one disk and a drawing from another, I am convinced that most users will eventually buy the second disk drive.) At the time this was written, Apple was committed to a totally unbundled pricing of the Macintosh—that is, the basic Macintosh package (at $1995 to $2495) includes the main unit, the keyboard, the mouse, necessary cables, a tutorial disk, and a disk containing the operating system. Everything else—Mac Write, Mac Print, all languages, the Image-writer printer, and the second disk drive—is priced separately. Since manufacturers want to claim the lowest possible price for their products, unbundling is common (IBM, for example, introduced the IBM PC with a low-end model, 16K bytes of memory, and a cassette port for $1265). True, the low-end Macintosh is far more complete than most manufacturers’ low-end products, but Apple has taken unbundling farther than any other microcomputer vendor—no one has sold a computer without BASIC (or some other language) in years. A usable Macintosh system with Mac Write, Mac Draw, a programming language, and the Imagewriter printer costs from $2589 to $3189; a second disk drive will add another $395. Apple would be wise to make this package available at a discounted package price, just as it now does for the Apple IIe. Apple contends that the Macintosh will become a home machine because office users will take it home a few times and like it enough to buy themselves one for their personal use. However, the Mac is still too expensive to penetrate the home market significantly; that will be left to less expensive machines, such as the Commodore 64, the IBM PCjr, the Apple II family, and the Coleco Adam.

Finally, I have to point out that, although Apple’s advertisements call the Macintosh a 32-bit system, its MC68000 processor is generally regarded as a 16-bit processor (the limiting factor is its inability to deal with multiplicands greater than 16 bits). This is no different from the vendors of some other 68000-based microcomputers, but I hate to see Apple hyping a machine that easily stands on its own merits.

Conclusions

Exactly a year ago, in a product description of the Apple Lisa computer, I said, “Technology, while expensive to create, is much cheaper to distribute. Apple knows this machine is expensive and is also not unaware that most people would be incredibly interested in a similar but less expensive machine. We’ll see what happens.”

Now we have seen what has happened, and it is rather impressive. The Lisa computer was important because it was the first commercial product to use the mouse-window-desktop environment. The Macintosh is equally important because it makes that same environment very affordable. It is also important because it is a second-generation design that, in several areas, improves on the original.

The Macintosh will have three important effects. First, like the Lisa, it will be imitated but not copied. In the year since the Lisa was announced, dozens of hardware and software companies have announced products that duplicate part of the Lisa user environment—the mouse, the windows, the integrated software. Some, like Microsoft’s mouse-based series of packages and Visicorp’s Visi On, have tried to mimic that environment on a smaller, less expensive machine (the IBM PC) with only partial success.

In a similar way, companies will be out to imitate the Macintosh, but their attempts will be less successful. Those companies that try to imitate the Mac on other machines will have trouble matching its price/performance combination. So far, attempts to imitate the Lisa by enhancing an existing computer (usually an IBM PC) have been given the benefit of the doubt because they are less expensive than the Lisa; attempts to imitate the Macintosh will now have a harder time because the Mac with software is about as cheap as the host hardware alone.

The only other way to match the Mac would be to design an entirely new system that would be comparably priced. This will probably not be attempted; only a few corporations have the ability to duplicate Apple’s design and manufacturing effort, and still fewer will make such a large financial commitment. (Apple is the only American company that does not live under the tyranny of next quarter’s profits; if any company tries to duplicate Apple’s effort, it will probably be a Japanese one.) Those that try will find it hard to create similar technology that competes with the Macintosh in size and price; Apple is confident that a number of its components and manufacturing techniques will be difficult to copy. Even though Apple has suffered from carbon-copy Apple II machines, it does not expect to have the same thing happen with the Macintosh.

Second, the Macintosh will secure the place of the Sony 3-1/2-inch disk as the magnetic medium of choice for the next generation of personal computers. I was disappointed when I first saw that the Mac used the 3V2-inch disk—”Another disk format to contend with,” I thought, “and you can’t use disks from the Lisa.” (You will be able to use Mac disks with the new Lisa 2; see “Apple Announces the Lisa 2,” on page 84.) Once I had heard Apple’s line of reasoning, though, I had to agree with its choice. Hewlett-Packard’s HP 150 is the only other major computer to use the Sony 3-1/2-inch disk to date; Apple’s use of it will tip the scales in Sony’s favor, and other manufacturers will follow.

Third, the Macintosh will increase Apple’s reputation in the market; in fact, to some people Apple will be as synonymous with the phrase “personal computer” as IBM is synonymous with “computer.” The Mac will compete with IBM’s PC, not its cheaper sibling, the IBM PCjr. Many business users will stay with the “safer” IBM PC. However, people new to computing and those who are maverick enough to see the value and promise of the Mac will favor it. The Mac will delay IBM’s domination of the personal computer market.

Overall, the Macintosh is a very important machine that, in my opinion, replaces the Lisa as the most important development in computers in the last five years. The Macintosh brings us one step closer to the ideal of computer as appliance. We’re not there yet—at least, not until the next set of improvements (which, in this industry, we may see fairly soon). Who knows who the next innovator will be?

---

Macintosh System Architecture

by Burrell C. Smith

Inside the Macintosh, hardware and software work together to provide a system capable of supporting high-performance graphics, built-in peripherals, and communication channels to the outside world. From the beginning of the Macintosh project, the product-design goals of small size, light weight, and moderate end-user cost encouraged us to create a low-power, low component-count design. The large number of I/O devices that are built into each unit, combined with our desire for high performance, caused us to explore many alternatives for each aspect of the hardware implementation. A cooperative spirit among the people working on the industrial design, analog electronics, digital electronics, and low-level software resulted in the synthesis of detailed implementations that combined strengths from each group, providing an integrated design solution for all aspects of the product.

The heart of the Macintosh digital electronics is the MC68000 processor and its memory (both RAM and ROM). In the Macintosh, the data-output lines from the system RAM drive a data bus separate from that used by the rest of the machine (see figure 2). The RAM is triple-ported; this means that the 68000, screen-displaying hardware, and sound-output hardware have periodic access to the address and data buses, so that the video, the sound, and the current 68000 task appear to execute concurrently.

ROM memory connects directly to the system data bus and is used by only the 68000. Much of the system’s time-critical code, such as the low-level graphics primitives, operating-system routines, and user-interface routines, reside in ROM. Macintosh software calls this code through 68000 “line 1010 unimplemented” instructions, which get one of approximately 480 addresses from an address table stored in low memory; this effectively allows the ROM subroutines to function as extensions of the 68000 instruction set. Since the ROM data and address buses are used exclusively by the 68000, ROM is always accessed at the full processor speed of 7.83 MHz; consequently, the ROM can perform as a readonly cache memory.

The 512- by 342-pixel video display appears in memory as a linear array of 10,944 16-bit words of data, with the most significant bit representing the pixel farthest left. Each 512-pixel horizontal line consists of 32 words of data, with bits shifted out at 15.67 MHz (322.68 us per 512-pixel line) followed by 12 words of horizontal blanking (taking 12.25 us). The last memory bus cycle of each horizontal line is reserved for sound DMA, where a byte of sound data is fetched from the sound buffer and sent to the sound PWM (pulse-width modulator) for conversion into an analog level. The update rate of the sound channel is then equal to the video horizontal rate, or 22,254.55 Hz. In the vertical direction, 342 active scan lines are followed by a vertical retrace and enough inactive horizontal lines to take up the same time as 28 horizontal lines, providing a vertical retrace time of 1.258 ms. Although screen-memory accesses may occur at any time, a vertical retrace interrupt is generated at the falling edge of the vertical sync pulse to allow screen animation to occur completely synchronous to the video beam movement.

Access to RAM is divided into synchronous time slots, with the 68000 and video circuits sharing alternate word accesses during the live portion of the horizontal video-display line and the sound circuits using the video time slot during the last memory bus cycle of the horizontal line. Although the access to RAM is divided three ways, the 68000′s share is maximized by giving it access to unused cycles during horizontal and vertical blanking. This way, 68000 access to RAM averages to a speed of about 6 MHz.

For high-performance sound generation, a tightly coded routine generates 370 samples of sound data and places them into the sound buffer just after a vertical retrace interrupt. The 68000′s 32-bit registers are used to control pitch with 24 bits of precision, providing each of four possible voices with 16,777,216 possible frequencies. For simpler sounds, a timer in the system’s VIA provides a square wave of programmable pitch. All sounds pass through a software-controlled volume adjustment that creates approximately 20 decibels of total amplitude variation in eight discrete steps.

The Macintosh disk controller is a single LSI (large-scale integration) component referred to as the IWM (“integrated Woz machine”) chip. The device, a one-chip integration of the disk controller originally designed by Steve Wozniak for the Apple II, handles data at 500 kilobits per second. To control the disk drive’s motor speed, a pulse-width modulator located on the digital board allows the disk to move at one of 400 possible disk motor speeds; the PWM is driven from a table in memory in a fashion similar to that of the sound system. By varying the motor speed, we created a more reliable disk drive that puts significantly more data on the same disk.

The Macintosh communications chip, the Zilog 8530 SCC (serial communications controller), provides synchronous and asynchronous data transmission at up to 230.4K bits per second using a self-clocking data format and up to 1 megabit per second using an external clock. The Macintosh’s two serial ports are identical; each provides single-ended or differential signaling and multidrop (party-line) capability.

The 6522 VIA (versatile interface adapter) rounds out the I/O requirements of the machine by providing system timers, support for the mouse and keyboard, and general-purpose I/O lines for selecting various system functions such as alternate screen and sound buffers and for communicating with the system’s real-time clock and parameter memory.

Burrell C. Smith is a member of the Apple Macintosh design team.

---

Going for the World Market

Having learned from past experience, Apple designed the Macintosh so that it could easily be modified for all markets outside the United States. The following examples show how pervasive nation- or language-specific aspects of a computer design are and how Apple has minimized the changes needed.

•Except for the word ‘Apple” on the rear panel, the Macintosh has no English text anywhere on the product or in the ROM. Each plug is labeled with a picture that identifies its function.

•The video-display rate of 60.15 Hz is generated internally instead of being derived from the line current. This allows the Mac to be used without modification in countries that have 50-Hz line current.

•Macintosh software has been designed so that all text messages, message layouts, and icons can be stored in a resource file, separate from the program itself. A designer can use a resource-editor program to change text (for example, to another language), icons, message layout, and the for- mats of time, dates, numbers, and currency. With this method, the program itself does not have to be changed and recompiled to make these changes.

•The keys on the keyboard are defined by the software, thus allowing Apple to change the keyboard easily to accommodate the special characters needed by some languages. In addition, Apple has designed the Mac so that two keyboards (differing in only one key) can be used for all versions of the product; Apple customizes a keyboard for a given language by printing the necessary legends into the plastic keys. In addition, any Mac keyboard can produce the full Macintosh character set; the only advantage to having the keyboard for a certain language is that the keyboard layout will be more appropriate for that language.

With these innovations, the most time-consuming part of modifying the Macintosh for another country is translating and printing the documentation. Apple reports that it will be shipping the Macintosh to several foreign countries “within several months of the Mac’s introduction.” (Companies never seem to meet such deadlines, so expect foreign versions to be shipped before the end of 1984.)

---

The User-Interface Toolbox

The toolbox (which occupies two-thirds of the high-speed 64K-byte ROM inside the Macintosh) includes optimized 68000 machine-language routines that handle all aspects of the Macintosh user interface-things like windows, text, the mouse, pulldown menus, desk accessories, dialogue boxes, and fonts. The figure below shows the relative relationships among the different units (or packages of routines). Here is a brief description of each unit, starting with the lowest-level unit and working up:

•Resource Manager: These routines coordinate the use of resources, which are data structures such as text strings, menus, and icon and font definitions. These resources are kept separate from the actual code of an application, which means that the resources of an application can be modified without forcing a recompilation (or modification) of the application program. The Resource Manager is usually called by higher units like the menu and font managers.

•Font Manager: This unit supports the use of various text fonts. It calls the resource manager when it needs to use a font not already in memory, and it is usually called by the Quickdraw unit.

•Quickdraw: Quickdraw is a graphics package that is at the heart of both the Lisa and Macintosh computers. Bill Atkinson, its creator, worked for 3-1/2 years on the code, rewriting it many times and reducing it from a 160K-byte compiled Pascal program to a 24K-byte package of highly optimized 68000 code. Atkinson, who was involved in the early design of the Lisa’s user interface, designed and optimized Quickdraw for the Lisa computer; he later joined the Macintosh design team. Quick-draw is very fast—for example, it can print to the screen more than 7000 characters per second. Two of its most interesting capabilities are its ability to fill in any arbitrary shape with a pattern and its ability to “clip” an image to correspond to the boundaries of an arbitrary masking shape. The latter ability is needed to correctly display window contents when one window overlaps others. The source code for Quickdraw is identical in both the Lisa and the Macintosh.

•Event Manager: All system events (e.g., keypresses and mouse button presses) are received and interpreted through this unit, which mediates between the application program and the outside world.

•Toolbox Utilities: These routines handle miscellaneous tasks that include string operations, fixed-point arithmetic, and bitwise logical operations.

•Window Manager: Since all action on the Macintosh display occurs within windows, this is a very important unit that is used a lot. The Window Manager allows the application program to interact with windows on a high level while it takes care of the low-level details automatically. It allows you to create different kinds of boxes (document, dialogue, and alert boxes, for example), delete them, move them, change their size, and make an inactive window active and vice versa. The Window Manager ensures that the computer automatically redraws the necessary screen areas when some aspect of a window is changed.

•Control Manager: This unit controls the use of software buttons, check boxes, and dials, all of which can be called on to show and alter the status of certain variables.

•Menu Manager: Given a two-dimensional matrix of menu items (each column is a menu title followed by its selections), this unit controls the display and behavior of that matrix of pull-down menus.

•Text Edit: These routines control elementary text entry and editing. Text Edit is designed with lots of software “hooks” so that you can modify its behavior but still use it. An external unit called Core Edit, which must be loaded into RAM, contains more sophisticated entry and editing routines; Core Edit can handle different fonts, sizes, and text styles.

•Dialog Manager: Dialogue boxes are text boxes with several check boxes; usually, clicking the mouse button near a box selects it (and the action or condition associated with it) and unselects the previously checked box. An alert box (as in figure 1h) alerts you to a potentially dangerous situation and forces you to click on one of two buttons, “Cancel” or “OK.” The Dialog Manager handles the display of and user response to a dialogue or alert box.

•Desk Manager: This unit allows the application program to use the desk accessories, which are resources that are called in from disk if they are not currently in memory.

Applications can be written in Mac BASIC, Mac Pascal, or 68000 assembly language (usually one of the latter two). Both Mac Pascal and Mac BASIC are designed so that their keywords directly call most of the toolbox routines. Most applications that use the routines are essentially an endlessly repeating loop that waits for an event, determines what kind of event it is, and then processes the event.

---

Macintosh System Software Overview

by Andy Hertzfeld

The Macintosh is more than a powerful, inexpensive 68000-based desktop computer. It comes with a built-in personality provided by 64K bytes of handcrafted system software contained in two ROM chips on its digital board. Besides performing traditional operating-system functions such as memory and file management, the Macintosh ROM includes the revolutionary Quickdraw package and a User-Interface Toolbox to help programmers develop applications that share a consistent, advanced user interface.

The Macintosh ROM can be thought of as an extension to the 68000 instruction set, augmenting its 56 basic instructions with more than 480 new instructions designed for implementing fast mouse-based applications. It is implemented entirely in 68000 assembly-language code that has been handcrafted and optimized over a period of almost three years. We chose assembly language over a higher-level language because it was very important for the system to be small and fast. The Macintosh is intended to be a very high-volume product, and we could afford to lavish time and attention on every rou- tine, making each one as efficient as possible, knowing that our efforts would be multiplied by the millions of units that we will eventually ship.

It is somewhat risky to put 64K bytes of intricate system software in ROM on a disk-based system, but we did it because we wanted the machine to have a built-in standard user interface. By using our ROM-based toolbox, a programmer saves development time and precious memory space; this provides a positive incentive for doing it our way. Also, the price per bit of ROM is significantly less than that of RAM, and not having the operating system load in from disk saves space on every disk you have. Application programs never reference the ROM directly; instead, they use compact “trap” instructions that are interpreted by the system dispatcher. This allows us to intercept any routine to fix the program bugs that will inevitably arise.

The Mac’s system software design philosophy emphasizes simplicity, flexibility, and high performance. We chose the single- application-at-a-time philosophy to help keep things relatively simple. The user- interface software is designed to be flexible because we are still learning how to make systems easier and more fun to use. Another reason for designing the software this way is that trying to live for years with what we thought was best at any given time would doom us to eventual failure. High performance is extremely important in an interactive system; people won’t enjoy using a system unless it is very responsive.

About one-third of the ROM is devoted to what we call the Macintosh Operating System, which contains many components found in more traditional systems. It includes the low-level device drivers and interrupt handlers, an asynchronous I/O system, a memory manager, a simple, fast file system, a segment loader, and various utility routines. The I/O system supports swappable, RAM-based device drivers as well as its built-in serial, disk, and sound drivers. Most I/O and file-system calls can be made asynchronously, which allows an application to overlap I/O tasks with other tasks. The memory manager minimizes the fragmentation of available memory into small pieces by supporting relocatable objects that are always accessed indirectly; the memory manager also provides an automatic caching scheme by optionally purging objects as memory grows fuller. The file system ensures against loss of data by maintaining tags on every block; these allow the contents of a disk to be pieced back together even if the directory is destroyed.

Another third of the ROM is occupied by Bill Atkinson’s Quickdraw graphics package. Quickdraw, which is the cornerstone of Apple’s “Lisa technology” is responsible for the Mac’s extremely fast user interaction. It draws practically everything you see on the screen, including text (in a variety of typefaces and styles) and both filled and unfilled rectangles, lines, and ovals. It also is capable of representing arbitrary areas of the screen called regions in a very compact data structure. All Quickdraw calls are clipped to the intersection of up to three regions, providing the fundamental capability necessary for overlapping windows. Quickdraw also is capable of recording any sequence of procedure calls and saving them as a picture. Pictures provide an easy, powerful method for transferring graphics between applications.

The final third of the Macintosh ROM is occupied by the User-Interface Toolbox, a collection of various managers and services intended to help a programmer develop applications that conform to the Macintosh standard user interface. Its principal com- ponents are resources, windows, menus, controls, dialogues, and a text-editing package. The window, menu, and control managers contain little information on how individual windows, menus, or controls look or behave. Instead, this information is encapsulated in definition functions, which are kept as resources and swapped into memory as necessary to implement messages sent by the various managers. This provides a very flexible structure capable of evolving as we learn how to improve the user interface.

Another important goal of the Macintosh system software is to facilitate the passing of data between applications. A * scrap manager is provided to help applications share data. It defines two data types that every application is requested to support (simple ASCII text and Quickdraw pictures) and lets applications define their own custom types. It provides routines for transferring data in and out of the scrap.

As stated above, Macintosh supports only one application running at any given time. This restriction is mainly due to limited available memory. By making a few simple calls to the desk manager, an application may allow many useful mini-applications to run concurrently with itself. These small programs are called desk accessories and are capable of cutting and pasting data with each other as well as with the major application. We currently provide five desk accessories (calculator, clock, notepad, control panel for default system parameters, and scrapbook).

By the spring of 1983, it became apparent that we would not be able to fit all the routines that we had hoped to into our 64K-byte ROM space. We designed a facility to allow some system code (in the system resource file) to be swapped in from disk to RAM when needed. We now use five such RAM-based packages, including a fully IEEE-standard floating-point numeric package, a standard file dialogue package, and an international string package that deals with various formats for date and time display.

In summary, the 64K bytes of ROM-based firmware provide Macintosh with a unique personality and user interface, forming the foundation for the development of communicating applications that share a common user interface. The Macintosh firmware is very fast and flexible, and it will be exciting to see all the applications that develop from it in the years to come.

Andy Hertzfeld is a member of the Apple Macintosh design team.

---

By the Way. . .

•No, we didn’t misspell the name. “Mcintosh” is the apple, but “Macintosh” is the Apple computer. The product’s original code name was misspelled by its first users, and Apple decided to stay with that spelling.

•The Mac Write program was originally named “Macauthor,” and the Mac Draw program was originally named “Mackelangelo.” People at Apple decided that the names were too cute to use; they were right.

•Apple is one of those exceptional companies that gives its employees credit instead of commanding them to work in anonymity behind the corporate name. The names of the hundred or so employees who worked on the Macintosh are molded into the inside face of the plastic rear housing. Don’t try to look for them, though; the Mac is not supposed to be opened except by repair people.

•The Macintosh is not going to be strictly a “serious” computer. Some of the software engineers at Apple are very excited about the great games that could take advantage of the Mac’s computing power and high-resolution graphics. I saw an incredible game that has Alice (of Wonderland fame) dodging animated chess pieces in 3D.

view additional pages

Apple’s Enhanced Computer, the Apple IIe

It’s like having an Apple II with all the extras built in.

It all began in the summer of 1977 at the West Coast Computer Faire. A fledgling computer company with an unusual name—Apple Computer— introduced a new hobby computer called the Apple II. The new Apple II was an impressive machine. It had BASIC in ROM (read-only memory), a built-in Teletype-style keyboard, high-resolution color graphics, and, once the new 16K-bit semiconductor memory devices became available, its memory could be expanded all the way up to 48K bytes. One of the first true home computers, it was completely self-contained, needing only a TV set for a display and a common cassette recorder for data storage.

Today, almost everyone is familiar with the Apple II. It can be found in homes, schools, laboratories, and businesses, and is being used in a wide variety of ways. During the past five years, an entire subindustry has sprung up around it that has, in turn, stimulated further Apple II sales.

It had been obvious for a while at Apple Computer that a replacement for the Apple II was needed. The Teletype-style keyboard, uppercase only 40-column display, and the maximum of 64K bytes of memory were becoming limitations as the marketplace changed and software became more sophisticated. The design was getting old and technology had changed enough to allow a redesign with significantly fewer parts. A new design could also address foreign requirements for special keyboards, displays, and video signals better than the Apple II. Although the Apple II was a tremendous success, it was clearly time to design a successor.

Enter the Apple IIe.

For about the same price as the Apple II, the Apple IIe (e for enhanced) provides a variety of exciting new features and capabilities. Rather than start from scratch and design an entirely new machine, Apple Computer Inc. chose to make a very careful series of enhancements and improvements while keeping the flavor and style of the Apple II. Although completely redesigned internally, the Apple IIe is clearly a member of the Apple II family.

Even though it looks almost the same as the Apple II, the Apple IIe (see photo 1) gives you a great deal more for your money. The base-priced machine includes 64K bytes of memory (expandable to 128K bytes), Applesoft BASIC in ROM, a 63-key keyboard that produces both upper- case and lowercase characters and has special-function keys, seven expansion slots for I/O (input/output) devices, and a video interface that can display 24 lines in a 40-column-wide format with both uppercase and lowercase characters (this can be easily and inexpensively expanded to 80 columns). In addition to the standard Apple II I/O expansion slots, the main circuit board also holds a special auxiliary connector that is used primarily for various video- and memory-expansion options. Along with Applesoft BASIC, the internal 16K bytes of ROM hold an improved monitor, built-in self-test routines, extended memory-management routines, and an 80-column firmware package with extended editing features that can be used with the 40-column display.

The quality of the product is highly evident. The case is rugged structural foam, the keyboard has a nice touch and dished keytops, and the back panel (see photo 2) has an array of openings that fit the 9-pin, 19-pin, and 25-pin D-type connectors commonly used for serial I/O devices. It appears obvious that the Apple IIe was designed from the ground up to meet the new FCC (Federal Communications Commission) RFI (radio-frequency interference) regulations.

The computer has a metal bottom pan, a metal back panel (rather than plastic as in the present model), and the removable cover is shielded with conductive paint and grounded with metal gaskets at the front and back edges. Some other nice touches include: the “D” and “K” keys (the ones that the middle fingers of a touch-typist’s hands fall on) have small bumps on their surfaces; the connector openings on the back panel come with plastic caps to cover them if connectors aren’t installed; the top cover has tabs in the rear to help lift it open, and screw holes to help keep it shut when desired (schools should like this feature).

Design Credits.

Although it is impossible to give credit to all the people involved, three people deserve special mention. Peter Quinn, the POS Hardware Section Manager, was responsible for the team that designed the Apple IIe. Walt Broedner designed the Apple IIe hardware, including its two custom integrated circuits. Rick Auricchio is Broedner’s software counterpart—he modified the original Apple II Plus firmware and added all the new code that is in the Apple IIe firmware.

The Keyboard.

The keyboard is the most obvious difference between the Apple II and the Apple IIe. It is essentially an enhanced version of the Apple Ill’s keyboard without the numeric pad; the keyboard on the Apple IIe (see photo 3) has 63 keys, while the Apple II has 53, and the layout is slightly different. Although the changes seem minor, they make the new keyboard significantly easier to use, especially in word-processing or screen-editing applications.

One of the most significant changes is indicated only by the Caps Lock key. The Apple IIe keyboard provides full uppercase and lowercase operation. When Caps Lock is latched down, however, it operates much like the original Apple II keyboard and produces only uppercase characters. If the two solder pads on the main board labeled X6 are connected, programs can check to see if the Shift keys are pressed by reading the PB2 input in the game-paddle port. (This supports a common Apple II modification and many existing word-processing programs.) To correct a limitation of the old Apple II keyboard, the new keyboard can produce all 128 ASCII (American National Standard Code for Information Interchange) character codes. This was accomplished in the Apple IIe by adding some new character keys, along with Tab and Delete keys, to improve its word-processing capability. (The added keys, with different keycaps, will be used in European versions to provide an ISO [International Organization for Standardization] standard keyboard layout.) Two interesting additions are the Open-Apple and Solid-Apple keys, which are positioned one on each side of the space bar. If you press Control, Open-Apple, and Reset simultaneously, the Apple IIe will write some arbitrary data into each page of memory and then simulate a power-up cold start. This eliminates the need to turn the Apple off and then on again to exit a protected program (a definite annoyance), but prevents people from making unauthorized copies of protected software.

Pressing Reset while holding Control and Solid-Apple invokes the built-in self-test software, which responds with “KERNEL OK” if the memory and circuitry pass the tests. Open-Apple and Solid-Apple may also be read individually and used as special-purpose keys by various programs—they are internally connected to the game-paddle port inputs PB0 and PB1. Other improvements in- clude a full set of cursor-control keys positioned to the right of the space bar, auto-repeat on all keys after a 0.9-second delay, and a relocated Reset key. (The Reset key is placed apart from the main keyboard to keep it from being pressed accidentally. In addition, the Control key must be pressed simultaneously with the Reset key to have an effect; this behavior, standard on the Apple IIe, was an option on later models of the Apple II Plus.) Internally, the keyboard is completely different from that on the Apple II. The Apple IIe keyboard is a simple array of switches—the key- board-scanning circuitry has been moved to the main printed-circuit board, which also holds a special numeric pad connector. A ROM on the main board maps the keyboard-switch closures into the appropriate ASCII codes and can be changed to provide foreign or special keyboards. (Incidentally, the American version of the ROM is only half used. The other half holds a Dvorak keyboard map that can be accessed with a few jumpers and etch cuts.) For programmers, the keyboard provides an additional “Any key down” flag; it can be read by examining location C010 hexadecimal. This will allow pro- grams to provide their own auto-repeat or special pause functions, overriding the auto-repeat built into the keyboard.

Text-Display Modes.

The standard Apple IIe displays 24 rows of 40 characters (see photo 4a). It provides normal (white on black) and inverse-video (black on white) modes for all characters, and a flashing mode for the uppercase characters and special symbols. If you try to display a lowercase character in flashing mode, the display shows a flashing special character instead. Although this may seem strange, it emulates exactly what is displayed by Apple IIs that have been modified with added lowercase adapters, and is done this way for compatibility with those machines. The Apple IIe also provides an alternate character set where there are only two modes—normal and inverse—but the characters are always displayed correctly.

Although the ability to display both uppercase and lowercase characters is a definite improvement, I suspect that few users will stay with the 40-column display. The two 80-column options are just too useful— and too inexpensive—to be ignored.

The 80-Column Display Options.

To accommodate users who need a display wider than 40 columns, the Apple IIe offers two 80-column option cards: the 80-column text card and the extended memory 80-column card, which includes 64K bytes of additional memory. Either of these cards can be plugged into the auxiliary connector, and they are both just memory cards. Photo 4b shows an example of the 80-column text display.

The actual 80-column display circuitry and firmware are already built into the Apple IIe. In fact, by setting the appropriate soft switches, you can see an 80-column display on any Apple IIe—every character in the normal 40-column display will be displayed twice. Both of the 80-column cards (see photo 5) provide the additional display memory required for 80-column operation; however, the 80-column text card is inexpensive because it is simply a lK-byte memory card.

The extra (separate) display memory is needed because the 80-column circuitry displays twice as many characters in the same period of time as the 40-column circuitry. This doubles the rate at which the display accesses memory; if the Apple’s main memory was used, this wouldn’t allow the processor any memory cycles. The designers found an ingenious solution to this dilemma. The Apple IIe’s dis- play always accesses memory at the 40-column rate, allowing the processor all the memory cycles needed. When in 80-column mode, however, the display circuitry reads both the main memory and auxiliary display memory simultaneously, saving the character that is read from the auxiliary memory and displaying it after the character read from the main memory. This allows the display to operate twice as fast but doesn’t affect the operation of the processor.

One of the nicest things about the Apple IIe 80-column option is that it is compatible with all other Apple IIe display modes. In the old Apple II, people often used two monitors with 80-column cards—one for the 80-column display and one for 40-column text and graphics—because the available 80-column cards had separate video outputs for the 80-column text.

The 80-Column Firmware.

The 80-column routines built into the Apple IIe ROMs provide a number of advanced cursor-control and editing features. One of the most interesting is the lowercase restrict mode. If you type a Control-R when the 80-column firmware is active, the keyboard input is restricted to uppercase only (just as if Caps Lock was pressed) unless you are between quotes. This mode is handy because Applesoft BASIC and DOS 3.3 won’t accept lowercase commands—it locks you into uppercase except when typing in BASIC string constants (which can accept lowercase).

To maximize its compatibility with existing software, the Apple IIe 80-column firmware emulates an 80-column card installed in I/O slot 3 (the standard location). If one of the two 80-column option cards is installed, typing PR#3 will activate the internal 80-column routines and disable any firmware installed in slot 3. Once activated, the 80-column firmware and its extended editing features can be used in either 40-column or 80-column mode. In fact, by setting one of the soft switches, you can use the 80-column firmware even if you don’t have the 80-column card installed.

To help you keep track of which display software is active, the Apple IIe displays three different types of cursors. A small checkerboard cursor indicates that the 80-column firmware is inactive. A larger block cursor is displayed when the firmware is on, and a + (plus sign) within the block indicates that the firmware is in “Escape mode” and is waiting for another keystroke, which will be interpreted as a cursor-movement command.

The 80-column software is also compatible with other languages. If you have Apple’s Pascal 1.1 or one of the Apple II CP/M systems, these both can load in 80-column mode and operate correctly without any additional patches or modifications.

Graphics.

Like the Apple II, the Apple IIe offers two standard graphics modes. The low-resolution mode produces 16-color graphics, with either 40 by 48 pixels (picture elements) or 40 by 40 pixels and four lines of text. The standard high-resolution mode provides a 280 by 192 bit-mapped pixel array with half-dot-shift logic (see photo 6). Depending upon the software used, this mode can be used to provide limited 560 by 192 monochrome graphics, 280 by 192 monochrome graphics with no limitations, 140 by 192 six-color graphics with limitations, or 140 by 192 four-color graphics. (The vertical dimension is reduced to 160 pixels if you want four lines of text at the bottom.) The 80-column options are the keys to the new Apple IIe graphics features. With the proper software, the Apple IIe can provide double-density graphics in both low-resolution and high-resolution modes. Either of the 80-column cards will support the double-density low-resolution graphics, but you will need the extended memory 80-column card if you want to use the double-density high-resolution mode, which can also provide 140 by 192 graphics with 16 colors! At the time this article was written (November 1982), no software was available to support these new graphics modes; however, it will undoubtedly be available soon, either from commercial vendors or user’s groups.

The double-density graphics modes are provided by the 80-column display circuitry. Instead of simply displaying bytes sequentially from the main memory, it displays bytes alternately from the main memory and the auxiliary memory, at twice the normal rate. Although this capability was designed to provide an 80-col- umn text display, the designers soon realized that it could also be used to provide additional graphics modes.

Use of the double-density graphics has three requirements. First, you need a Revision “B” main circuit board; this will probably be the only type shipped after the first month of production. Second, you must connect two pins on your 80-column card; this is explained in the Apple IIe Reference Manual. Third, you must turn on the AN3 output to the game-paddle connector; this can be used to switch between normal and double-density mode. (Unfortunately, the Apple IIe sent to BYTE for review had a Revision “A” main board. Thus, there is no photo of the new graphics modes included with this article.) Inside the Box.

The most significant differences between the Apple II and the Apple IIe are internal. The main printed-circuit board has been totally redesigned and incorporates many new features and options unavailable in the Apple II.

The power supply is unchanged, but there are now seven I/O expansion slots instead of the eight found in the Apple II. Part of the Apple IIe memory emulates a 16K-byte RAM (random-access read/write memory) card (commonly installed in Apple IIs), and the card’s former location, I/O slot 0, is no longer present.

The most obvious change is a reduction in the number of ICs (integrated circuits). Where an Apple II with a keyboard enhancer, a 16K-byte memory card, and an 80-column card included about 120 ICs, the Apple IIe provides the same features with just 31 ICs. A large part of this reduction is due to the use of 64K-bit dynamic memories, rather than 16K-bit ones. The entire 64K-byte memory of the Apple IIe occupies just 8 ICs.

Another significant reduction in IC count is provided by two custom-designed MOS (metal-oxide semiconductor) ICs—the IOU (input/output unit) and MMU (memory-management unit)—that manage memory and I/O decoding and provide many of the new internal features. Photo 7 shows the engineering breadboard of the Apple IIe main board and a second board that emulates the IOU and MMU with standard 7400-series ICs, so that the designs could be completely tested before committing them to silicon. The IOU and MMU emulations required about 50 and 60 ICs respectively. In the final board (shown in photo 8), these 110 ICs are replaced with just two components.

Working together, the IOU and MMU generate all memory-address- ing and I/O-decoding signals. The MMU is primarily responsible for supporting the 6502 processor. It accepts addresses from the processor, does any necessary memory-bank switching, and converts the address to the multiplexed form required by the dynamic memories. The IOU provides similar functions for the video display. It also includes the video-timing logic, keyboard control, and other miscellaneous functions. To support foreign versions of the Apple IIe, the IOU includes video circuitry to provide both the American-standard NTSC (National Television System Committee) signals and European-standard PAL signals. The IOU ICs are customized during assembly by the manufacturer by connecting the internal bonding wires to the appropriate set of pads on the IC chip inside the package.

The Auxiliary Connector.

Although I/O slot 0 is no longer present, a new “auxiliary connector” can be used in a variety of ways. In the factory, the auxiliary connector is used to connect special test equipment to the Apple IIe With this equipment and the signals available at the auxiliary connector, problems can be localized to one or two ICs.

Once in the customer’s hands, the auxiliary connector is used to hold various video and memory options. Its set of signals provides access to a number of areas in the Apple IIe and can, in fact, be used to totally disable the internal video-generation circuitry, so that an alternate video generator can be installed. Currently, the only options supplied by Apple Computer Inc. for the auxiliary slot are the two 80-column cards. However, other devices should soon be available from Apple and other manufacturers.

The Extended Memory 80-Column Card.

Besides an 80-column display, the extended memory 80-column card provides an additional 64K bytes of memory. Rather than switching blocks of auxiliary memory into a fixed address range, the designers chose to replicate the entire 64K-byte addressing space on the auxiliary card and provide a series of soft switches that enable either the main memory or auxiliary memory in various address ranges. The documentation points out that “even though an Apple IIe with an extended memory 80-column card has a total of 128K bytes of programmable memory in it, it is not appropriate to call it a 128K-byte system. Rather, there are 64K bytes of auxiliary memory that can be swapped for main memory under program control.”

To help programmers use the auxiliary memory, the Apple IIe 80-column firmware provides two special routines: AUXMOVE and XFER. Using these two routines, you can store and retrieve data in the auxiliary memory or transfer control to a program that resides there.

AUXMOVE is used to copy data from main memory to auxiliary memory or vice versa. You simply store the data’s starting address, ending address, and destination address in memory locations; set or clear the processor’s carry flag to indicate direction; and call AUXMOVE. XFER is used in a similar fashion in order to jump from programs in main memory to others in auxiliary memory (or vice versa). XFER may also be used to switch stacks and zero pages as you transfer from one section of memory to the other.

These two routines, and the auxiliary memory, open up some interesting possibilities. It appears to be possible, for example, to have an entire Pascal system residing in main memory, while a DOS 3.3/BASIC system is in auxiliary memory, and be able to transfer control between the two systems at will.

Soft Switches.

To support the auxiliary memory and 80-column display software, the Apple IIe provides a number of new soft switches and adds a few new features to the old ones. (A soft switch, in an Apple II or Apple IIe, is a memory location that can be accessed to cause some hardware change to take place.) Existing soft switches in the Apple II were used to select various video modes and control the internal I/O devices (keyboard, game paddles, speaker port, and cassette port). If a 16K-byte memory card was added, it included additional switches to disable the card or to enable areas on the card as read-only or read-write memory. When using the switches, however, the programmer had to keep track of them. There was no way to read them back.

The Apple IIe makes many of the existing soft switches, and all the new ones, readable. Specifically, you can read back the states of the video-mode switches, the 16K-byte memory-card-area switches, and all the new auxiliary-memory switches by examining locations between hexa- decimal C010 and C01F. To help provide better graphics animation, you can also read the “vertical blanking” from the video display, thus allowing you to change the contents of memory while it is not being used to create the video display.

The auxiliary memory is supported by several new switches that change the display from main to auxiliary memory, enable display areas in both memories at once for 80-column text or double-density graphics, and control reads and writes to the auxiliary memory. Other switches allow you to overlay portions of the I/O-slot memory space with the internal ROM 80-column firmware or self-test routines, and select either the standard or alternate display character sets. (Figures la and lb provide memory-switching maps for the Apple IIe.) Apple II Compatibility.

One of the major concerns during the design of the Apple IIe was its level of compatibility with the Apple II. Literally thousands of programs are written for the Apple II, and numerous hardware products are designed to plug into Apple II I/O slots. User surveys had shown that the volume of available software was a prime consideration among purchasers. It was therefore obvious that the new machine had to be compatible with virtually all existing Apple II hardware and software products, while still including the desired new features and design improvements.

The designers succeeded admirably. The Apple IIe is physically a complete redesign; logically, however, it is compatible with almost all existing Apple II software and hardware add-ons. This goal was not met simply—more than 150 software products and numerous peripheral devices were tested for compatibility during the Apple IIe development process.

Unfortunately, a few Apple II-based products from other manufacturers won’t work properly in an Apple IIe—primarily because their designers did not follow Apple’s interface guidelines. In general, accessory cards that occupy one of the I/O slots and do not connect directly to an IC socket will operate correctly. Others that connect directly to the main circuit board or to the keyboard will not be compatible without redesign.

Examples of cards that will work in an Apple IIe include 80-column cards, serial and parallel interfaces, graphics tablets, disk controllers, and memory cards that do not connect to an IC socket. To maximize compatibility, Apple II-style video- and game-paddle connectors are provided inside the case, even though the new-style connectors are now on the back panel. This allows existing video switches, joysticks, and game controls to be used with the Apple IIe (although they may cause excessive Figure 1: (continued) RF interference).

Devices that won’t work in an Apple IIe include keyboard enhancers, lowercase display adapters, numeric pads (existing designs), and memory cards that connect to an IC socket with a small flat cable. Fortunately, the capabilities of most of these devices are already included in the Apple IIe.

It is much harder to quantify which Apple II software products will or will not work in an Apple IIe. To support the new hardware features, certain changes had to be made to the ROM monitor routines, and these changes may affect programs that use the monitor. Approximately 40 standard entry points and routines in the monitor have been documented by Apple Computer, and all these have been left intact and operate correctly, even though the actual code may have changed somewhat. However, some programs use undocumented entry points and these may or may not run properly.

It seems safe to assume that all programs written in higher-level languages will work. Thus, software written in Integer or Applesoft BASIC, FORTRAN, PILOT, Logo, and Pascal should run correctly (providing that no strange monitor CALLs were made), along with CP/M programs that use the standard BIOS (basic input/output system) CALLs. Also, any software sold by Apple Computer will be compatible with the Apple IIe. In addition, a great deal of commercial software has been tested at Apple Computer, and your local dealer should know which products are compatible with the new machine. (If in doubt, you should ask the dealer to demonstrate the program on an Apple IIe before purchase.) Software.

As with most new computers, a great deal of software isn’t available yet specifically for the Apple IIe, but the machine doesn’t require it. Most of its new features can be applied to make existing Apple II software easier to use. At least initially, the Apple IIe will use the same DOS 3.3 disk operating system that is currently used in the Apple II, although it will probably be repackaged on a new master disk.

Apple Computer Inc. has done a great deal to make writing programs for the Apple IIe as easy as possible. The Apple IIe Reference Manual provides precise technical descriptions of every area of the machine, and the built-in memory-management routines will encourage programmers to take advantage of the extended memory option. Because the 80-column firmware acts like a conventional 80-column card in I/O slot 3, programs that use 80-column displays can easily be compatible with both the Apple IIe and the Apple II.

To help programmers identify the type of machine and which options are present, the Apple IIe Extended 80-Column Text Card Supplement to the reference manual provides an identification routine, with examples in assembly language, BASIC, and Pascal. To aid outside developers (Apple considers them extremely valuable), 120 Apple IIes were lent to various vendors during the eight months prior to the product introduction. This allowed a large number of software and hardware suppliers to prepare a variety of new products—eighteen programs from ten companies are scheduled for introduction coincidentally with the Apple IIe.

One interesting new program for the Apple IIe is simply called “Apple presents Apple IIe.” Primarily a keyboard tutorial, it uses humorous text and excellent graphics to guide you in a friendly fashion through the features of the Apple IIe keyboard. The section that teaches the cursor keys includes two simple but well-designed maze games where you guide a rabbit or gnome through a maze with the cursor-control keys. These made an immediate hit with our 3-year-old, who within 15 minutes was guiding the rabbit through the maze and laughing at its antics when it hit the walls.

Applewriter and Quickfile.

Applewriter IIe and Quickfile IIe are Apple Computer’s first two major software products that are designed to use all the new Apple IIe features. Both are enhanced versions of the same programs for the Apple III, and both are characterized by being extremely friendly to the user—they provide clear, simple prompts, multiple menus to select options, and numerous “help” screens to guide you through the program operations. Although at the time this article was written (with Applewriter) the documentation was preliminary, it appears to follow the format of the other Apple IIe manuals—clear and friendly.

Applewriter IIe is a document-oriented word processor with numerous editing and print-formatting features. It will run with or without the 80-column display and extended memory options, but will use them if they’re present. One of the more interesting features of Apple-writer IIe is called WPL (word-pro- cessing language). WPL allows you to compose and execute a series of Applewriter commands that are stored in a disk file. It provides looping, conditional execution, and subroutine calls, effectively allowing you to automate the production of form letters, invoices, or other repetitive tasks. WPL also provides a turnkey capability that can be used to automatically execute a WPL program after you load the Applewriter IIe disk.

To get familiar with Applewriter IIe, I used it to prepare this article. I was particularly impressed with the print-formatting capabilities. It was very easy to set up a standard manuscript page—double-spaced, one-inch margins, with headers and footers— and I could preview the actual appearance of the result by printing to the display rather than the printer. It did, however, take me a while to get used to some of the editing features. When you delete characters, words, or paragraphs, Applewriter deletes from right to left. This is fine if you are correcting a mistyped character immediately but seems a little awkward otherwise. On the whole, I liked Applewriter and recommend that you look it over if you are considering purchasing a word processor for your Apple IIe.

Quickfile IIe is an information-filing system (or database manager) that allows you to store and retrieve information, search and sort your files, and print reports in formats that you define. It also has math capability—you could set it up, for example, to file a list of checks and their amounts, and it could also balance your checkbook for you.

Quickfile IIe is also compatible with Applewriter IIe. Quickfile reports can be included in Apple-writer documents, and Quickfile files can guide the production of Apple-writer form letters. I didn’t get a chance to spend much time with Quickfile, but it appears to be very well done, as is most of Apple’s software.

Documentation.

The new Apple IIe manuals are so good they must be seen to be believed. In a spiral-bound format, slightly larger than the Apple II manuals, they are extremely clear and readable—presenting their information in an easy step-by-step manner. It is obvious that Apple spared no effort or expense when designing them.

The Apple IIe Owner’s Manual is an excellent example of the right way to introduce a beginner to a first computer. Using clearly written text and numerous color photos, it starts out by telling you how to unpack and set up the computer and then explains the various parts of the system in layman’s terms. As you read through the manual, points of special interest and warnings are clearly noted and possible error messages are explained. Nine pages are devoted to the keyboard alone—they describe how to use each of the functions available and how they are commonly used in programs. Further chapters introduce you to the system hardware, the DOS 3.3 disk operating system, the display features, and various computer applications. Other chapters describe the various computer languages, how to add components to your system, and what to do when you have problems.

This is clearly the first manual a new owner should read, and is also the only manual that is included with the Apple IIe. The new owner picks up the only manual in the box and it tells exactly what to do to get the system up and running. To avoid confusion, all other manuals are optional, and many manuals included with products are available separately. (The Apple He Owner’s Manual is shown in photo 9.) The Apple IIe Reference Manual is an optional manual worth noting. It provides a complete technical description of the machine, and its operation, in detail sufficient to satisfy almost anyone. It provides descriptions of the hardware and special features, instructions for using the monitor, timing diagrams and pin-outs of the custom ICs and ROMs, and a complete set of schematics. No self-respecting programmer or experimenter should be without this manual. Apple also provides other manuals, including rewritten Applesoft and DOS manuals and reference manuals for the Apple IIe and the 80-column boards; see the “At a Glance” text box on page 70.

Conclusions.

As you can probably tell, I was impressed with the Apple IIe. The people at Apple Computer had their act together when they designed this machine and it really shows.

I am disappointed that the 80-column cards are not as inexpensive as they were rumored to be; other vendors will probably design less expensive ones. However, with the new keyboard and 80-column display, the Apple IIe can handle just about any task.

The manuals with the system are superb. They are friendly, easy to read, and comprehensive, setting a new standard for the industry to meet.

Applewriter IIe and Quickfile IIe are well-written, useful programs that will find favor with people who wish to use their Apple IIe for word processing and information filing. With these two programs and a spreadsheet (like Visicalc), you could satisfy virtually all your computing needs.

I was most impressed with the balance struck between compatibility and new features, and the obvious care that went into the design. Congratulations, Apple Computer, you’ve produced another winner.

view additional pages

Microcomputing, British Style

The Fifth Personal Computer World Show

by Gregg Williams, Senior Editor

Quick: what’s the most microcomputer-hungry country in the world? The United States, of course, right? We’ve got Silicon Valley and Route 128 (recently dubbed Technology Highway) near Boston. We’ve got BYTE, Apple, Atari, and IBM. True enough, but Britain has the people and it has a lot more than we do.

There’s ample evidence that, compared to the U.S., proportionally more of Britain’s population is interested in microcomputers. The Fifth Personal Computer World Show, a business and hobby microcomputer show hosted by one of Britain’s leading computer magazines, Personal Computer World, is a case in point. From September 9 to 12, 1982, 47,461 people attended the show—12,000 more than visited this year’s West Coast Computer Faire, which also lasted four days and was—until now—the world’s largest microcomputer show. If that’s not enough evidence, consider that the Personal Computer World Show held at the Barbican Center in London had far fewer exhibitors and less exhibition space than the Computer Faire, yet drew roughly one-third more people. A quick check in an almanac confirms that the population of the United States is almost four times that of the United Kingdom, which makes the attendance figures even more impressive. Something rather important is happening over there.

Last September, I attended the show to observe the state of microcomputing in Britain firsthand. And if the crowds I saw in London were any indication, more Britons from a wider range of ages (still almost exclusively men and boys, though) are clamoring for microcomputers than Americans are on the basis of any American convention I’ve ever attended. On the weekend, I saw a line—er, excuse me, queue—of people several blocks long waiting to buy tickets. It must have taken hours to reach the window, and once inside you couldn’t move or see anything.

Why are the British so enthusiastic about microcomputers? Part of the answer lies in the official support of the British government, which decided that microcomputers are important enough to warrant government-sponsored public education on the subject. The British Broadcasting Corporation (BBC) sponsored a tutorial series on computers and commissioned an official microcomputer to be used in conjunction with the programs. I’m told that the television programs have been augmented by books and materials to be used in the public school system. A BBC series on programming is planned, and the National Extension College, a home-study institute, already has a course on BASIC programming using a generalized version of the language.

Jack Schofield, editor of another leading British microcomputer magazine, Practical Computing, has his own hypothesis for the popularity of microcomputers in Britain. The past decade has not been kind, economically or socially, to Britain, and as a result most people have learned to accept long lines and high prices as part of daily life. Fearful that high technology may put him out of a job someday, the average Briton has accepted the computer as a potential influence, but one that he has some control over. This, Schofield says, may explain the strong interest in microcomputers that transcends British class and economic boundaries.

Whether or not Schofield’s hypothesis is correct, the British appetite for microcomputers owes a good deal to the pivotal work of one man: Clive Sinclair. As head of Sinclair Research, the company that makes the ZX80, the ZX81, and the Spectrum microcomputers, Clive Sinclair is to the British small computer what Adam Osborne is to the American business computer: the creator of a product whose price is so low that the competition finally accepted it as the price to beat. Before Sinclair brought out the ZX80 at about £100 (less than $200), the British had only expensive American imports. Discounted Commodore VIC-20s and Atari 400s, for example, sell for around £200 and £300 respectively, almost twice their American prices. Because it is so expensive abroad, the Apple II is known primarily in Britain and Europe as a business machine, believe it or not. American microcomputers have always been just too expensive for the average person. You can then imagine the exultation when Sinclair Research brought out the ZX80 for under £100—one-half to one-third the price of the imports. Granted, it wasn’t as good a computer, but more people could afford it, and that made the difference. Now more than half the microcomputers in Britain are ZX80s and ZX81s. The ZX81 now sells for £50, and British manufacturers are interested in creating a full-featured computer for less than £300.

My first observation at the Personal Computer World Show was that people were insatiably curious about microcomputers. After that, I was impressed by the diversity of inexpensive machines. I’ve written short descriptions of the six machines most worthy of note—the Acorn BBC Model B, the Dragon 32, the EACA Genie III, the Camputers Lynx, the Grundy Newbrain AD, and the Sinclair Spectrum. (All but the Genie III are low-cost machines.) I’ve included a chart that compares those computers, a collection of photos from the show, and a list of addresses for all the products mentioned in this article. So lean back and enjoy the show—at least you don’t have to fight the crowds.

The Sinclair Spectrum

If Clive Sinclair’s black-and-white ZX80 and ZX81 have become the most popular microcomputers in Britain (and, for that matter, in the rest of the world), is it any wonder that his company’s new color microcomputer, the Spectrum, is doing just as well?

The success of the Spectrum is a source of great comfort to Clive Sinclair, especially since the BBC chose Acorn’s design over his for use in its computer-literacy program. (Incidentally, Sinclair could be accused of the same tactic for which he had berated Acorn: advertising the product long before he was able to deliver it.) As the British ad for the Spectrum points out, the Spectrum is markedly simpler and more elegant than the Acorn BBC Microcomputer when measured by the number of chips on its main circuit board. However, the Spectrum shows a quirkiness that is the price we pay for its circuit board elegance and low cost. And Clive Sinclair’s statement that the Spectrum is “less than half the price of its nearest competitor—and more powerful” is only half right: half the price, yes, but definitely not more powerful.

First of all, you have to consider the keyboard. For £125, we can’t quite demand the full keyboards offered by machines that are considerably more expensive than the basic Spectrum. Given the price differential, we can make allowances for the Spectrum’s unique keyboard, which is basically a pressure-sensitive membrane (like those of the ZX80 and ZX81) mounted under a piece of molded gray rubber that protrudes above the plastic cover to make “keys.” This interesting scheme works surprisingly well, but the cramped 9.3-inch-wide keyboard has other faults that are harder to excuse.

Inexpensive or not, the keyboard layout is impossible to justify. It may be innovative, but it’s also poorly designed in several respects. The layout is clever in that you can use it to enter letters, numbers, one-stroke BASIC keywords, graphics symbols, and the like. But that scheme makes the keyboard busy. Most keys have five legends: three printed on the key and one each immediately above and below the key. This design may be necessary, but it also causes eyestrain and confusion. I’d be willing to forgive all this, but I can’t excuse such thoughtless “innovations” as providing only one Caps Shift key (in the lower left-hand corner; the one on the right is used as a Symbol Shift key) and placing the space key in the lower right-hand corner of the keyboard.

The Spectrum’s BASIC is a superset of the Sinclair BASIC used in the ZX80 and ZX81, and it has some valuable features, most of them having to do with the rather clever way graphics are implemented. ZX81 cassette tapes will not load on a Spectrum, and most ZX81 BASIC programs will require some modification to work.

Sinclair used his earlier computers as a testing ground for several original features. Some of these (like the “intelligent” cursor that prevents you from entering syntactically incorrect BASIC statements) have remained in the Spectrum, while others (like the nonstandard character code used in the ZX80 and ZX81, abandoned for the ASCII code in the Spectrum) are mercifully absent.

The character-oriented video image is 24 lines of 32 characters each. Each character has a separate attribute byte (each one of eight colors, chosen independently) that determines its foreground and background colors, brightness, and flashing/steady status. The screen is always in the bit-mapped graphics mode (192 by 256 pixels), and characters are “painted” onto the video display in a pixel pattern. (This makes possible unrestricted mixing of text and graphics as well as an OVER command that merges a character string with whatever image is already on the screen.) Actually, it’s easiest to think of the video screen in terms of monochrome pixel graphics (i.e., each pixel is either on or off), with each 8- by 8-pixel square (character) having its own foreground and background color. Using the metaphor of images being “printed” on video “paper,” the BASIC commands INK and PAPER set the foreground and background, respectively, of the next character to be printed. Unfortunately, this scheme restricts the color combinations of two adjacent pixels (unlike most high-resolution graphics schemes, which allow two adjacent pixels to be almost any color pair). The Spectrum also has 21 user-defined characters, each of which can be defined via special BASIC commands (thus simplifying the process more than other microcomputers).

Like the ZX81, the Spectrum has a rear-edge connector that contains a full set of address, control, and data lines. The Spectrum will accept the same ZX printer that the ZX81 uses, but, unlike the ZX81, it is upgraded to its maximum 48K bytes of memory via an internal 32K-byte board and won’t work with the ZX81 16K-byte memory pack. Other peripherals in the works from Sinclair are a £20 RS-232C/network interface board and a £50 3-inch disk drive. The company’s Microdrive (as it is called) is noteworthy because it costs well under $100. Each 3-inch floppy disk can hold up to 100K bytes of data; its average access time is 3.5 seconds, and its data-transfer rate is 128K bits per second.

How will the Spectrum fare in the American market? That depends. Timex Corporation has the rights to market the Spectrum (it already markets a modified ZX81 as the Timex/Sinclair 1000). If the Spectrum were to sell for the equivalent of £125, its price in Britain, it would cost roughly $220 in the United States—hardly competitive with comparable low-cost American units. My guess is that Timex will market an American version of the Spectrum for somewhere between $125 and $175 within the next six months.

In any case, the Spectrum is a promising machine. I’ll reserve further judgment until it becomes available here in the United States.

The Acorn BBC Model B Microcomputer

The BBC Microcomputer enjoys a colorful reputation because of its history. (See “The BBC Computer,” Popular Computing, October 1982.) More than two years ago, the BBC decided to start a computer literacy television series. The network realized that, with more powerful and increasingly inexpensive microcomputers, it would soon be possible to create them with enough computing power to offer their owners personal hands-on experience with microcomputers at an affordable price. The BBC considered the Newbrain computer and rejected it. Acorn and Sinclair Research, along with other companies, then submitted designs, and the Acorn won. (Sinclair went on to market its design as the Sinclair Spectrum.) Clive Sinclair has been quick to point out problems with the Acorn unit, and the interaction between the two companies has been a source of entertainment for the British computer community.

Although the BBC Model B is more expensive than some units (see page 49), it has an advantage over most of the very-low-cost ones: it is a no-compromise computer that has many uses beyond self-instruction in computer technology. I will confine my remarks to the Model B unit instead of the less expensive Model A (at £299) because the latter lacks most of the features that make the BBC Microcomputer competitive with other similarly priced units.

The BBC Model B has eight video-display modes, five pixel-graphics modes in which you can display text, and three text-only modes. The highest graphics mode (640 by 256 pixels, 2 colors) requires a video monitor, while the lowest one (160 by 256 pixels, 4 or 16 colors) offers roughly the same resolution, practically speaking (i.e., once the image is displayed on a standard color television) as the Apple and Atari computers, but it also offers additional colors.

The most innovative feature of both BBC computers is the Tube, a special interface built into the computer that enables the main computer (which uses a 6502 board) to communicate with any suitably designed auxiliary microprocessor board. This is, not coincidentally, a way for Acorn to provide a Z80 board so that the BBC computer can run business software available through Digital Research’s popular CP/M operating system. At first, the Tube sounds like the Microsoft Consumer Products’ Softcard for the Apple II, but the connection it uses is different. The Softcard and similar boards share the address and data lines with the main microprocessor. The Tube, however, uses a dedicated 2-MHz serial link with memory buffers on each side of the link and interrupt-driven software. This scheme allows true coprocessing with both processors running at full speed. Acorn has plans to offer 6502 and Z80 auxiliary boards and is experimenting with a board containing National Semiconductor’s 16-bit 16032 chip.

Acorn is offering an interface to its Econet local network system that will make it possible to hook up as many as 254 microcomputers using inexpensive 4-wire telephone cable. Orbis, a subsidiary of Acorn, supports the Cambridge Ring (developed at the Cambridge University Computer Laboratory), a high-speed local network in a ring configuration that can connect to anything from mainframes to microcomputers.

BBC BASIC is closely modeled after the de facto standard Microsoft versions, but it adds several good extensions. The most important of these are local variables, subroutines that pass parameters, and recursion. BASIC has always been severely handicapped because it lacks these features (especially the first two), and I applaud the BBC’s inclusion of them in the language. (Language designers, especially Microsoft, take note.) Another fascinating feature is a built-in 6502 assembler that allows 6502 assembly-language code in a BASIC program—bravo again! How Acorn got these and many other features into a 16K-byte BASIC, I’ll never know.

The BBC Model B includes an RS423 serial port, which is said to be an RS-232C-compatible interface that facilitates a higher data-transfer rate and a longer maximum cable length than the RS-232C. In addition, the Model B includes an 8-bit Centronics-type parallel port, an 8-bit input/output (I/O) port, an RGB (red-green-blue) color-monitor output, and four 12-bit analog-to-digital ports.

Although some other British microcomputers offer more features for a given price, none of them surpasses the BBC Model B microcomputer in terms of versatility and expansion capability. Acorn has plans to produce a version of its computer for American use but has not yet set an availability date.

The Dragon 32

The Dragon 32 is named for its standard 32K bytes of memory—quite a selling point in a country accustomed to microcomputers with memories as small as 1K bytes. And because the Dragon 32 is one of the newest British microcomputers, it offers more features for the money than most of its competitors (see table 1).

The Dragon 32 seems to be a very adequate machine, but there’s nothing exceptional about it. In fact, I can sum it up in one sentence: it looks like a Radio Shack TRS-80 Color Computer with 32K bytes of memory. (I’ve found that some Color Computer cartridges will run on the Dragon 32, but they must be taken out of their plastic shells to fit in the Dragon 32 cartridge slot.) Its similarities to the TRS-80 Color Computer include use of the 6809E microprocessor and Microsoft’s Extended Color BASIC (right down to command names—PMODE, HEX$, and DEFUSR, for example), nine colors for color graphics display, five graphics modes, joysticks, and cartridge software.

The Dragon 32, however, does have several advantages over the TRS-80 Color Computer. First, in Britain it is considerably cheaper than the Color Computer. Second, the Dragon 32 can be expanded to a full 64K-byte workspace (unlike the Color Computer, which can only be expanded from 16K to 32K bytes of memory). Third, the Dragon 32 has a typewriter-style keyboard that is somewhat better than the TRS-80 Color Computer’s adequate but calculator-like keys. Finally, the Dragon 32 includes a Centronics-type parallel-printer port.

Dragon Data Ltd. plans to market its computer in America but hasn’t decided on a date. You can be sure the company will take care of its home market before expanding internationally. When that happens, American buyers will have a choice of low-cost color computers.

The EACA Genie III

The Genie III is the only one of the six microcomputers profiled here that doesn’t fall in the low-cost category. I included it because, of all the business machines at the show, it’s the one that caught my eye. Like the IBM Personal Computer, it is newsworthy not because it’s innovative but because it carefully combines the best features of other computers. It is manufactured by EACA International and distributed in Britain by Lowe Electronics.

The Genie III is housed in two units. The main one contains the computer itself, a 12-inch green-phosphor video display, and two 5-1/4-inch double-sided 80-track floppy-disk drives. (These can be augmented by either two 5-1/4-inch or two 8-inch floppy disks.) The other unit is a detachable 86-key keyboard, which includes a numeric keypad around whose two edges eight function keys are wrapped.

Emulation capabilities are the Genie Ill’s main claim to fame. It is supplied with two operating systems, NEWDOS-80 version 2.0 and CP/M 2.2. If you load NEWDOS-80, the BASIC loaded is a RAM (random-access read/write memory) version of Radio Shack TRS-80 Model I BASIC supplied (legally) by Microsoft; the video display shows 16 lines of 64 characters each, and the machine emulates a TRS-80 Model I. If you load CP/M, the video display shows 24 lines of 80 characters each, and the machine emulates a CP/M system with a standard screen size. (Under software control, NEWDOS can also use the 24 by 80 video format.) Table 1 lists some of the Genie Ill’s features. Its built-in real-time clock, optional high-resolution graphics (288- by 640-pixel) board, and optional programmable-character interface board are also of interest. With additional hardware, the Genie III can support multiple users and run Digital Research’s MP/M operating system. You can also add an external 5-megabyte hard disk.

The Grundy Newbrain AD

In the July 1982 issue of Personal Computer World, managing editor Dick Pountain writes, “When the Newbrain was announced to the world two years ago, the design concept was significantly in advance of anything that had been seen in the field of handheld computing.” And so it was—even though problems plagued the design. In fact, the company that created it, Newbury Labs, sold the design to its current owner, Grundy Business Systems Ltd. At one time, the Newbrain was in line to be the BBC computer, but design problems and the change in ownership caused the BBC to look elsewhere.

The machine is now being advertised as a compact but powerful microcomputer, and the number of hardware and software features and options it offers supports this point of view. The Newbrain AD, which contains a 16-character fluorescent display, is complemented by a cheaper version, the Newbrain A, which sells for £199. The Newbrain M, a third model that includes a battery-backup option, is scheduled to be released soon.

The basic unit includes a Z80A microprocessor that runs at 4 MHz, a National Semiconductor COP 420M microprocessor dedicated to handling input and output, 32K bytes of RAM, and 29K bytes of ROM (readonly memory). Through an external expansion box, you can increase this to a staggering 2 megabytes of RAM and 4 megabytes of ROM. Grundy plans to market the CP/M operating system and popular applications-software packages in ROM, which will convert the Newbrain to a “crashproof,” stand-alone computer dedicated to one task. The keyboard has calculator-type keys in a standard configuration; the spaces between keys are just slightly smaller than those on a standard typewriter keyboard. The Newbrain video-display character set contains 512 letters, numbers, and graphics as well as videotex symbols. The character set is divided into two 256-character banks, only one of which can be selected at a time.

A Multiple Communication/Network Module adds 8, 16, or 24 (depending on the model) RS-232/V24 bidirectional serial ports. According to the manufacturer, Newbrains connected through this module constitute a de facto network that can share floppy or hard disks, printers, and other peripherals.

An optional Videotex Module enables Newbrain owners to access British Teletext and Prestel services.

The Newbrain produces a monochrome text or graphics video image. The machine offers a choice of several pixel densities: 256, 320, 512, or 640 pixels per row. In addition, you can split the video display into separate graphics and scrolling-text areas (with text above graphics); a graphics-only display has 250 rows of pixels.

The Newbrain software is equally versatile, if confusing on occasion. The 29K bytes of ROM contain the Newbrain operating system as well as its BASIC, mathematics package, screen editor, graphics package, and device-driver software. The BASIC conforms to the ANSI (American National Standards Institute) x3.2/78 standard instead of the more common de facto Microsoft BASIC standard. The Newbrain’s graphics package combines traditional point-to-point drawing with Logo-like “turtle” commands (e.g., move-forward-drawing-a-line and rotate-pen-to-new-facing-angle). In addition, commands that draw arcs and fill areas with color are available.

The most useful commands relate to data streams, which are the “pipeline” through which all data transfer occurs. As with the Atari 400 and 800 computers, all input and output is handled through the operating system. This procedure accomplishes two things: first, it allows I/O to be handled in a standard way, regardless of the language or hardware involved; second, it is an open-ended approach that lets you write software interfaces that will work with any hardware you connect the machine to. Up to 255 data streams can be open at one time. For example, multiple data streams opened to the Newbrain screen editor give you multiple graphics “pages” that can be written to and displayed independently.

The Newbrain is obviously a complex, capable machine designed with open-ended expansion in mind. I personally do not like its small size, and its design is sometimes too complex. I would, however, want to examine it more carefully before making a final decision on it.

The Camputers Lynx

The Lynx, from Camputers Ltd., is one of the newest machines I saw in England. “Previewed,” not announced, at the Personal Computer World Show, it offers more computing power for the money than any other machine I saw there.

The unit itself is almost Spartan in appearance and size, but it has some rather attractive features. The keyboard, which houses the entire computer, is full-sized and conventionally laid out. Unfortunately, the Delete key is where the Return key usually is, and the Return key is, oddly enough, to the right of the right Shift key. The Lynx comes with 48K bytes of memory, but it can be expanded to an impressive maximum of 192K bytes. The computer runs a Z80A microprocessor and can optionally run CP/M. It has a good 40-character, 24-line video display that converts to an 8-color, 248- by 256-pixel graphics display. With additional memory, video resolution doubles to 80 characters per line and 248- by 512-pixel graphics. I was told that the unit allows user-defined characters. Representatives from Lynx say a 5Vi-inch disk drive will be available for the unit and that the company will eventually market an adapted version of the machine in the United States.

ASCII Art in 1939
Typewritten Flag (ASCII Art)
ASCII Art – 1948
I.C.S ASCII Art Ad

WHERE TO BUY IT?

NOW GET YOUR ANSWER COMPUTER QUICK!
PLAYBOY has programmed the names and addresses of quality retailers across the country, stores which handle the fine products advertised in this issue. To find those stores in your area that handle products in which you’re interested, simply use the attached reply card. Within 5 days you’ll receive a computer-printed letter with the answers. Why search around when you can relax?

REACTS
5-DAY READER ACTION SERVICE

are you the I.C.S. type of man?

There is a definite I.C.S. type. The records of 100,000 current students . . . nearly 5 million students since 1891 . . . supply the outlines. Here’s how the typical enrollee shapes up at the time of beginning his studies: He is an adult. In wartime he is in the Armed Forces or in vital production. But war or peace, good times or bad times, he is an employed man. Circumstances have prevented his attending a college but he is ambitious, intelligent, determined to acquire the specialized training that will help him in his present job and prepare him for a better one.

Does the description fit you? Then you’ll be interested in what I.C.S. helps these students to achieve. In a single 30-day period we have received as many as 635 student letters reporting advancement in salary and position. In a period of 120 days we have received 1,920 such reports.

Graduates include the presidents, board chairmen, chief engineers or chief chemists of some of the largest steel, airplane, chemical, railroad and electrical equipment companies in the country. Thousands of others have registered substantial successes in their chosen fields. Here’s the kind of coupon they signed.

INTERNATIONAL CORRESPONDENCE SCHOOLS

view additional pages

Introducing Apple II.

The home computer that’s ready to work, play and grow with you.

Clear the kitchen table. Bring in the color T.V. Plug in your new Apple II? and connect any standard cassette recorder/player. Now you’re ready for an evening of discovery in the new world of personal computers.

Only Apple II makes it that easy. It’s a complete, ready to use computer—not a kit. At $1298, it includes features you won’t find on other personal computers costing twice as much.

Features such as video graphics in 15 colors. And a built-in memory capacity of 8K bytes ROM and 4K bytes RAM —with room for lots more. But you don’t even need to know a RAM from a ROM to use and enjoy Apple II. It’s the first personal computer with a fast version of BASIC—the English-like programming language—permanently built in. That means you can begin running your Apple II the first evening, entering your own instructions and watching them work, even if you’ve had no previous computer experience.

The familiar typewriter-style keyboard makes communication easy. And your programs and data can be stored on (and retrieved from) audio cassettes, using the built-in cassette interface, so you can swap with other Apple II users.This and other peripherals—optional equipment on most personal computers, at hundreds of dollars extra cost—are built into Apple II. And it’s designed to keep up with changing technology, to expand easily whenever you need it to As an educational tool, Apple II is a sound investment. You can program it to tutor your children in most any subject, such as spelling, history or math. But the biggest benefit—no matter how you use Apple II—is that you and your family increase your familiarity with the computer itself. The more you experiment with it, the more you discover about its potential.

Start by playing PONG. Then invent your own games using the input keyboard, game paddles and built-in speaker. As you experiment you’ll acquire new programming skills which will open up new ways to use your Apple II. You’ll learn to “paint” dazzling color displays using the unique color graphics commands in Apple BASIC, and write programs

to create beautiful kaleidoscopic designs As you master Apple BASIC, you’ll be able to organize, index and store data on household finances, income tax, recipes, and record collections. You can learn to chart your biorhythms, balance your checking account, even control your home environment. Apple II will go as far as your imagination can take it. Best of all, Apple II is designed to grow with you. As your skill and experience with computing increase, you may want to add new Apple peripherals. For example, a refined, more sophisticated BASIC language is being developed for advanced scientific and mathematical applications. And in addition to the built-in audio, video and game interfaces, there’s room for eight plug-in options such as a prototyping board for experimenting with interfaces to other equipment; a serial board for connecting teletype, printer and other terminals; a parallel interface for communicating with a printer or another computer; an EPROM board for storing programs permanently; and a modem board communications interface. A floppy disk interface with software and complete operating systems will be available at the end of 1977. And there are many more options to come, because Apple II was designed from the beginning to accommodate increased power and capability as your requirements change.

If you’d like to see for yourself how easy it is to use and enjoy Apple II, visit your local dealer for a demonstration and a copy of our detailed brochure. Or write Apple Computer Inc., 20863 Stevens Creek Blvd.,Cupertino, California 95014.

Apple IIâ„¢ is a completely self-contained computer system with BASIC in ROM, color graphics, ASCII keyboard, lightweight, efficient switching power supply and molded case. It is supplied with BASIC in ROM, up to 48K bytes of RAM, and with cassette tape, video and game I/O interfaces built-in. Also included are two game paddles and a demonstration cassette.

SPECIFICATIONS

• Microprocessor: 6502 (1 MHz)
• Video Display: Memory mapped, 5 modes—all Software-selectable:
• Text—40 characters/line, 24 lines upper case.
• Color graphics—40h x 48v, 15 colors
• High-resolution graphics—280h x 192v; black, white, violet, green (16K RAM minimum required)
• Both graphics modes can be selected to include 4 lines of text at the bottom of the display area.
• Completely transparent memory access. All color generation done digitally.

• Memory: up to 48K bytes onboard RAM (4K supplied)
• Uses either 4K or new 16K dynamic memory chips
• Up to 12K ROM (8K supplied)
• Software
• Fast extended Integer BASIC in ROM with color graphics commands
• Extensive monitor in ROM
•I/O
• 1500 bps cassette interface
• 8-slot motherboard
• Apple game I/O connector
• ASCII keyboard port
• Speaker
• Composite video output

Apple II is also available in board-only form for the do-it-yourself hobbyist. Has all of the features of the Apple II system, but does not include case, keyboard, power supply or game paddles. $598.

PONG is a trademark of Atari Inc.

Apple II plugs into any standard TV using an inexpensive modulator (not supplied).

Apple Computer Inc

Typewriter Artist Produces Pictures Like Tapestry
Pictures that resemble tapestry are produced with a typewriter by Rosaire J. Belanger, a mill worker in Saco, Me. Belanger first draws a pencil sketch on a sheet of paper, then inserts it in his typewriter and fills in the sketch with various characters to produce shading and outlines. With carbon paper, he transfers the picture onto graph paper, and copies it on blank paper.

They’re Here!
THE NEW HEATHKIT PERSONAL COMPUTING SYSTEMS

H8: 8-bit Computer $375

H11: 16-bit Computer

H9: Video Terminal

H10: Paper Tape Reader/Punch

The new VALUE-STANDARD in personal computing systems! Play exciting and challenging computer games, exercise your imagination and ingenuity with do-it-yourself creative programming, store and retrieve personal records like taxes and budgets, solve complex mathematics and scientific problems almost instantly, control your home appliances for best energy savings and efficiency — literally thousands of fascinating, exciting and practical applicatons. The Heathkit computer systems are low-priced, versatile and reliable — they’re the ones to have for REAL power and performance!

These Heathkit computer products are “total system” designs with powerful system software already included in the purchase price. They’re the ones you need to get up and running fast. And they’re backed by superior documentation and service support from the Heath Company, the world’s largest manufacturer of electronic kits.

NEW H8 8-Bit Digital Computer. This 8-bit computer based on the famous 8080A microprocessor features a Heathkit exclusive “intelligent” front panel with octal data entry and control, 9-digit readout, a built-in bootstrap for one-button program loading, and a heavy-duty power supply with power enough for plenty of memory and interface expansion capability. It’s easier and faster to use than other personal computers and it’s priced low enough for any budget. With assembler, editor, BASIC and debug software.

NEW H11 16-bit Digital Computer. The most sophisticated and versatile personal computer available today — brought to you by Heath Company and Digital Equipment Corporation, the world leader in minicomputer systems. Powerful features include DEC’S 16-bit LSI-11 CPU. 4096 x 16 read/write MOS memory expandable to 20K, priority interrupt, DMA operation and more. DEC PDP-11 software is included.

NEW H9 Video Terminal. A full ASCII terminal featuring a bright 12″ CRT, long and short-form display, full 80-character lines, all standard serial interfacing, plus a fully wired and tested control board. Has auto-scrolling, cursor with full positioning controls, full-page or line-erase modes, a transmit page function and a plot mode for simple curves and graphs.

NEW H10 Paper Tape Reader/Punch. Complete mass storage peripheral uses low-cost paper tape. Features solid-state reader with stepper motor drive, totally independent punch and reader modes and a copy mode for fast, easy tape duplication. Reads up to 50 characters per second, punches up to 10 characters per second.

Other Heathkit computer products include a cassette recorder/player and tape for mass storage, the LA36 DEC writer II, serial and parallel interfaces, software, memory expansion and I/O cards, and a complete library of the latest computer books — everything you need to make Heath your personal computing headquarters!

Heathkit Catalog
Read all about our exciting computer systems and nearly 400 other fun-to-build, money-saving electronic products in kit form.
Prices are mail-order FOB, Benton Harbor, Michigan. Prices and specifications subject to change without notice.

Typewritten Flag
Anyone can draw an accurate picture of the American flag on a typewriter, according to Menno Fast, a relief worker in Poland. Fast read a recent Popular Mechanics article on drawing pictures with a typewriter. He submits a drawing of the flag as proof that it can be made on an ordinary typewriter using standard spacing. The flag, with a full 13 stripes and 48 stars, appears to be rippling in the wind.

KEYBOARD ART
By Paul Hadley
WHILE purely entertaining, doodling with a typewriter gives vent to the imagination and originality of both the experienced and the hunt-and-peck typist. Fill-in pictures are the easiest to “draw” with a typewriter. An example is shown in the flower which is made with the letter X alone. Such pictures, whether a flower or a portrait, are made by using an outline of the subject as a typing guide. This is done by tracing the outline lightly on paper and backing it with carbon paper to type the picture. Caricature or cartoon “drawing” combines letters with symbols as shown in the examples below. Here, half-spacing of the typewriter is required, as in the case of the owl’s beak and feet. The log cabin shows what can be done in drawing a picture in perspective.