Byte, marzo del 86

Proseguimos con nuestro proyecto de leer la revista Byte, cuarenta años más tarde. El resto de entradas de la serie, como siempre, las encontrarás en la etiqueta Byte de obm. En enero habíamos hablado del Atari 520ST y este mes toca el hermano mayor, el 1040ST.

Portada de la revista Byte. La ilustra una foto cenital de un ordenador, con su monitor (de tubo, claro) y su ratón de dos botones. Hay un segundo tema de portada, Homebound Computing

Destaco, en primer lugar, un megaanuncio de Microsoft publicitando sus lenguajes de programación.

Solo pongo la portada, porque se alarga hasta siete páginas más, que el catálogo de Redmond era extenso y su presupuesto para publicidad profundo. Sirve el anuncio, además, para ver cuáles eran los lenguajes que Microsoft consideraba importantes en la época. Arrancan con C («First with the pros«), Macro Assembler («The Quickest. Bar none«), FORTRAN («The overwhelming favorite«), COBOL («The interactive edge«), Pascal («When you’ve outgrown the others«) compartiendo página con QuickBASIC («BASIC just got faster«), que ilustraban, si no me equivoco, con una HP12, y cerraban con LISP («The language of artificial intelligence«), muMATH («Mainframe math on your PC«) y Sort («Versatility without compromise«), compartiendo página también.

¿Quién esperaba ver a FORTRAN y COBOL ahí arriba en 1986? Yo, no. Ni siquiera recordaba que Microsoft hubiese tenido un sistema de álgebra simbólica…

Y de la publicidad de lenguajes saltamos al programa que, en una realidad paralela a la nuestra, ocupa el lugar de Photoshop: el mítico Deluxe Paint (aquí, una carta de amor al Deluxe Paint III), que en aquella época no le sacaba los colores (see what I did there?) a los de Adobe… porque Photoshop 1.0 no llegaría al mercado hasta el muy lejano año de 1990.

Drawing and Painting Program for Amiga

Electronic Arts has released a graphics package for drawing and painting with the Amiga. Deluxe Paint, first in a series of arts software for the Commodore machine, has 20 drawing tools, 7 painting modes, 14 special-effects tools for brushes, 10 built-in brush shapes, and a palette of 32 colors (out of a possible 4096).

Deluxe Paint's drawing tools include magnify and zoom functions that let you split the screen into a normal image and a magnified portion of the image. As you zero in on and alter details in the magnified window, changes are reflected in the normal window. Another tool lets you customize paintbrushes. Anything you can draw can be framed, picked up, and used as a new paintbrush.

The package offers four types of brushes: circles, squares, dots, and airbrush. You can rotate any brush 360 degrees, flip it vertically or horizontally, stretch it into new shapes, or shear its angles. Shading and smearing capabilities help with texture and nuance.

You can create animation effects with what Electronic Arts calls "color cycling—cycling a variety of colors through a static picture to concoct the illusion of motion. You can use three different color cycles and speeds per picture.

Five color controls let you handle the mix of red, green, and blue and adjust the hue and brightness of each color. The software enables the Amiga to automatically generate the shades of color between any two pigments you pick.

Deluxe Paint, priced at $79.95, is designed to work with two other programs still in the Electronic Arts workshop, Deluxe Print and Deluxe Video Construction Kit (reportedly slated for April release). It requires 2 56K bytes of RAM and Kickstart 1.1.

Me paro un momento en la sección de libros para recordar al muy mítico (en aquella época) Peter Norton. Si tuviste un PC con MS-DOS, muy probablemente recuerdes sus míticas Norton Utilities (que ¡siguen existiendo!), pero a lo mejor no sabías que era un autor de «best sellers» sobre la programación del PC.

BOOK REVIEWS

THE PETER NORTON PROGRAMMER'S GUIDE TO THE IBM PC Peter Norton Microsoft Press Bellevue, WA: 1985 426 pages. $19.95

THE COMPUTER CULTURE Denis P. Donnelly, editor Fairleigh Dickinson University Press Cranbury, NJ: 1985 176 pages. $24.50

MICROSOFT MACINATIONS Mitchell Waite, Robert Lafore, Ira Lansing Microsoft Press Bellevue, WA: 1985 497 pages, $19.95

THE COMPUTER LAW ANNUAL 1985 Miles R. Gilburne, Ronald L. Johnston, Allen R. Grogan, editors Harcourt Brace Jovanovich New York: 1985 405 pages, $60

THE PETER NORTON PROGRAMMER'S GUIDE TO THE IBM PC

Reviewed by Donald Evan Crabb

Although the information Peter Norton provides in The Peter Norton Programmer's Guide to the IBM PC is not new or unique, reading it is an education. The book picks up where Norton's Inside the IBM PC (Robert J. Brady Co., 1983) left off. Whereas the earlier book concentrates on the hardware components of the IBM Personal Computer and how they work together, the new book is written strictly with the PC programmer in mind. Both works combined provide a comprehensive technical reference to the PC. As you might expect, these books cover some material in common. For example, both explore the ROM BIOS of the PC. But the discussion in The Programmer's Guide is designed for the programmer. In fact, this book should be useful to anyone who needs to understand the technical details involved in creating PC programs. Norton makes the distinction right from the start that he is providing more than just PC programming knowledge. He is trying to impart concepts about PC programming.

Norton also concerns himself with the philosophy of programming the PC. He laces the book with explanations about the design concepts that permeate the entire IBM PC line. Due to Norton's wealth of experience working with PCs, this information is synthesized so that it is more useful than the usual dry engineering discussion that you often get in books of this kind. He carefully divides the ROM information into four chapters: ROM BIOS basics, ROM BIOS video services, ROM BIOS disk services, and ROM BIOS keyboard services.

The Programmer's Guide details the original PC. But keep in mind the subtitle of this book: "The ultimate reference guide to the entire family of IBM personal computers." Norton explains differences between the design, construction, and systems software of the other members of the PC family and the PC. Most of the examples and information describe the Intel 8088 microprocessor and how it's programmed through the services provided by the ROM BIOS and by DOS. Many of the programming examples use BASIC as the representative high-level language. Pascal and C-language examples also appear. Norton shows how to write 8088 assembly-language interface programs for each of these languages.

The scope of the book extends to a number of programming areas. From video and disk basics, Norton moves from how the keyboard operates in programs to all the programming aspects of DOS. The final two chapters, "Program Building" and "Programming Languages," are worth the price of admission alone. Norton covers the conceptual basics of writing, compiling and interpreting, linking, and executing programs. Especially informative are the discussions of the DOS LINK program and the logical organization of assembly-language programs.

Norton discusses both the IBM Pascal compiler and the generic Microsoft Pascal compiler. He discusses Pascal data formats on the PC and how to work with them, as...

(Si tuviese más tiempo y dinero de los que tengo, seguramente haría por obtener una copia del Computer Law Annual 1985, porque por la crítica parece digno de leer con curiosidad histórica, con artículos sobre los problemas de propiedad intelectual de la ingeniería inversa, o la normativa antitrust, aunque también dicen que está escrito para juristas.)

No me alargaré mucho con el ordenador protagonista del número: a estas horas ya deberíais tener claro que el ST era mejor que el Mac (y del Windows de la época ya ni hablemos)… pero que estaba por debajo del Amiga (con la excepción de las aplicaciones musicales: ¿sabíais que Fatboy Slim sigue usando un ST?).

The Atari 1040ST

A megabyte of memory for $999

Editor's note: The following is a BYTE product preview. \t is not a review. We provide an advance look at this product because we feel that it is significant. A complete review will follow in a subsequent issue.

Atari's new $999 1-megabyte 1040ST (see photo 1) establishes a price break reminiscent of the Commodore 64's. And, as table 1 shows, the 1040ST will be the first computer to begin its retail life at a price that represents less than one dollar per kilobyte. The 1040ST is clearly a bargain, with over 1 megabyte of RAM (random-access read/write memory), its operating system in ROM (read-only memory), an internal 720Kbyte double-sided drive, an internal power supply, and the same features and functionality that already make the Atari 520ST an attractive purchase. (Editor's note: See "The Atari 520ST" by }on R. Edwards, Phillip Robinson, and Brenda McLaughlin. January BYTE, page 84. |

System Description

Our coverage of the 520ST adequately describes most of the features of the 1040ST (see also the "In Brief" box on page 86). The new computer has the same keyboard, the same ports (although these are now in new locations, see photo 2), and the same architecture. We remain uncomfortable with the keyboard, but the keytops are removable. We suspect that some speedy entrepreneur will provide alternative tapered keys for the ST machines.

The most obvious changes are cosmetic: The keyboard/computer unit is 2 inches deeper and 4'/2 pounds heavier than the 520ST and the keyboard provides a much more substantial feel. The mouse/joystick ports are now located under the bottom right front of the unit, a significant improvement for left-handed users.

A number of changes are more than cosmetic. The internal power supply eliminates two of the external power supplies needed by the 520ST (wire haters rejoice). We left the unit on for five days and experienced no difficulties with overheating. There is no internal fan, but the unit appears to adequately dissipate heat. The internal disk drive supports both single and double-sided disks. An RF (radio frequency) modulator will allow you to hook up the 1040ST to a television set; you might, therefore, obtain the high-resolution monochrome system for word processing and programming without sacrificing the use of low- and medium-resolution color. However, we received a preproduction unit lacking the RF modulator that will accompany the final product; therefore, we were unable to test the television quality of the computer's output.

The megabyte of RAM in the 1040ST isn't crammed into the case. The 520ST uses a custom Memory Controller chip to handle its sixteen 2 56K-byte dynamic RAM chips. The 1040ST uses the same Memory Controller. Because the controller can handle 32 RAM chips at a time, the Atari engineers simply had to find room for 16 more 2 56K-byte dynamic RAMs on the 1040ST circuit board to pump RAM capacity to a full megabyte (see photo 3). In fact, the Memory Controller can also govern 1 -megabit dynamic RAM chips. Atari should have little difficulty designing an ST with 4 megabytes of memory. Undoubtedly, the most interesting addition to this computer, apart from the extra memory, will be an empty socket for a graphics coprocessor. Our preproduction unit also did not include the socket, and it may not be offered with the first releases of the 1040ST Phil Robinson discussed this and Atari's future plans with Shiraz Shivji, vice president of research and development for the company (see the text box "An Interview with Shiraz Shivji" on page 90).

TOS IN ROM

With TOS (the operating system for both the 520ST and the 1040ST) in ROM, the 1040ST boots more quickly than the 520ST. [Editors note: Atari is currently supplying the ROM chips to 520ST developers and will be making the chips available through users groups.] Booting with a nonsystem disk takes less than 6 seconds, down from 37...

Los de mirada afilada habréis notado que en la portada, además del ST, había un segundo tema, el «homebound computing». ¿Que qué es eso? Nos lo cuenta el primer artículo del tema, que comienza recordándonos que el teletrabajo no lo inventó el COVID, y que ya se hablaba de ello hace cuarenta años, pero que anuncia que el tema se va a centrar en la informática como ayuda para las personas que, por el motivo que sea (una discapacidad, por ejemplo), no pueden desplazarse.

WORKING AT HOME WITH COMPUTERS

by Jane Morrill Tazelaar

For some, telecommuting is a choice: for others, it is the only option

THERE ARE MANY REASONS for wanting to work at home. Some of them involve disabilities that make it impossible or impractical to work in an office. For many disabled persons, the alternative to working at home is no alternative at all; it is the only work they can do, the only way they can become productive members of the work force. Some people work at home because of priorities such as being available to young children, especially during the preschool years. Many parents of small children must choose between sending them to daycare centers or babysitters and earning a reasonable living. Other reasons involve the lack of local work opportunities in economically depressed or geographically remote areas. And for some people, working at home is a simple matter of choice. The electronic cottage, the flexiplace, telecommuting, worksteading, or whatever you wish to call it could be the answer to all these problems.

Starting Your Own Business

Starting your own business seems to be the answer for many people. There is a certain romance in the very word entrepreneur, and there is a great deal of information available to help you get started if the idea of being one appeals to you. The various organizations associated with the cottage industry movement— the Association of Electronic Cottagers, the National Association for the Cottage Industry, and the National Alliance of Homebased Businesswomen— offer good and helpful information for the aspiring entrepreneur. (See the text box "Sources Mentioned" on page 1 56 for addresses and phone numbers.) They also offer countless references, contacts, and, possibly most important, support groups.

Two subjects seemed to jump out at me from all the literature I have seen on starting your own business: selling and networking. First, if you don't want to sell, you probably don't want your own business. Most business ventures involve direct selling. Whether you provide a product or a service, you need to sell it. Even if you have salespeople working for you, you have to sell the idea to some financial institution to get funds to get started and to the people you hire to get them to work for you. Then, long after the basics are in place and you are operational, you'd better be prepared to talk about your product or service, explain its value, and convince a prospective buyer that he or she ought to do business with your company instead of someone else's— in other words, sell.

Networking is a way to increase your contacts. Whether people are business contacts or social contacts or both, they can add significantly to the success of your business. The people you know either personally or electronically are sources that can provide you with future customers, business partners, financiers, good tax accountants, awareness of your competition, discounts on computing equipment, the inside story on future technology, and so on.

Starting your own business is a very rewarding venture for some and a complete disaster for others. At the...

Me salto el artículo sobre síntesis de habla a partir de imágenes para pasar directamente al e-learning, que me toca la fibra especialmente.

THE ELECTRONIC UNIVERSITY NETWORK

by Donna Osgood

Get a degree without ever leaving your computer

UNTIL RECENTLY, education at home meant correspondence courses. Taking courses through the mail is a slow, cumbersome way to learn, and for many people it means missing out on a vital part of the education experience: contact with a human instructor. Without that, you can easily lose interest in the course and drop out.

Meanwhile, as the baby boom generation passes, colleges faced with declining enrollments are looking for ways to reach a wider range of potential students. They need to reach people who would not ordinarily be willing or able to matriculate in the traditional way.

TeleLearning's Electronic University Network addresses both problems. Through the Network, universities offer accredited courses to students who enroll, participate in "class," interact with instructors and other students, and take tests on the material they have studied, all without leaving their microcomputers. Since classes are small (usually 10 students per instructor) and feedback on each assignment comes within a day or so, students taking courses from colleges through the Electronic University Network get much more individual attention than they would in a large class on campus. Some of the other benefits of telecommunication apply here as well: An instructor can judge a student only on the basis of his or her work, without interference from preconceived notions and biases based on how the student looks, speaks, or acts.

Founded in 1983, TeleLeaming began offering accredited courses in March of 1984. In January 1985 it established full-fledged degree programs, and it now offers two associate degrees, two bachelor's degrees, three MBAs, and specialized professional certificates. The degrees are awarded by fully accredited colleges (Thomas A. Edison State College in Trenton, New lersey, City University in Bellevue, Washington, and lohn F. Kennedy University in Orinda, California). The Electronic University itself offers no credit, acting solely as a coordinating medium and resource center for students. About 17,000 students have enrolled.

Courses available through the Electronic University Network include noncredit courses for personal improvement (writing, computer literacy, drawing, and wine appreciation, for example), business and professional skill classes (time management, accounting, and business math, among others), and tutoring programs for children (reading, math, and computer literacy). Courses for credit span the humanities, natural sciences, mathematics, social sciences, and business at undergraduate and graduate levels.

How It Works

You enter the Electronic University by buying an enrollment package for $150. This one-time fee covers operating software, communications software, and lifetime enrollment in the Electronic University for your entire family. Tuition for individual classes is handled separately. The admissions questionnaire and class registration...

Y es que en 1986, el año en que los módems de 2400 baudios nos parecían lo más, la educación a distancia ya no era necesariamente por correspondencia, gracias a la Electronic University Network de Telelearning. Hay más sobre el tema en Tedium.co y en eLearning Inside, pero el artículo nos explica que la cosa no era ni siquiera «lo último de lo último», porque se había fundado en el lejano 1983 y tenía programas de grado oficiales desde 1985, con 17 000 estudiantes matriculados hasta entonces. Eso sí, los materiales de aprendizaje no eran en línea: te enviaban el libro a casa. Tecnología necesaria: un IBM PC o PCjr, un Apple II o un (cómo no) Commodore 64 (el 35% de los matriculados no tenía ordenador al apuntarse). ¡Y había hasta mensajería instantánea!

Pasar a otro tema del que también, oh sorpresa, seguimos hablando hoy: envejecimiento y tecnología.

INCREASING INDEPENDENCE FOR THE AGING

by K. G. Engelhardt and Roger Edwards

Robotic aids and smart technology can help us age less dependency

FOR THE FIRST time in history, a significant portion of our population is living to be senior citizens, and we have no experience in caring for large numbers of healthy, literate, articulate older persons, many of whom are highly educated. As our society grays, we need more ways to help increase the independence of those with chronic and multiple disabilities. Rapid advances in microprocessor based technologies are providing us with many new possibilities. Their miniaturization, flexibility, modularity, and ever-decreasing costs now make it possible to realistically address human problems that we could not just 10 years ago.

The need to control our environment and our lives in order to reduce dependence is critical to human development. Loss of personal independence is costly, not only in actual dollars spent on institutional and long-term care, but also in emotional and psychological terms. The need to reduce premature and unnecessary institutionalization of our elderly citizens is critical. We need more devices that will increase the independence and the sphere of control of individuals with disabilities and to augment the care givers' tasks with state-of-the-art tools to help them provide better care.

This article discusses potential applications of microprocessor-based technology for increasing independence in those with declining abilities. From panic buttons to smart houses, from stationary telemanipulators to self-navigating robots, from memory-aid devices to expert systems for daily living, microprocessor based technology can assist the functionally dependent older person.

Applications

An applications team was formed during the winter of 1984 to investigate potential uses for robots and robotic related technologies. The team identified 54 subgroups of tasks and divided them into 12 major categories: patient transport-lift-transfer, housekeeping, ambulation (walking patients to help prevent bedsores), physical therapy, depuddler (urine cleaner), surveillance (to help with wandering patients), physician assistant, nurse assistant, patient assistant, vital-signs monitor, mental stimulation, and one miscellaneous group. Let's look at some possible robotic applications in a few of these groups. Lifting and Transferring: The challenge of lifting and transferring individuals with partial or total paralysis, extensive weakness, or increased fragility due to age is significant. One robotic solution could be a track mounted robot arm that glides along the ceiling until it reaches the room to which it has been summoned. The care giver or the older person could then direct the arm to assist in lifting or transferring the individual from bed to chair or wheelchair to bath, for example. This assistance could also help...

Que sí, que hace cuarenta años ya nos interesaba si las tecnologías digitales podrían ser una ayuda para una sociedad que envejecía cada vez más. Y a continuación viene el tema en que nos paramos cada vez en obm: ordenadores y discapacidad visual.

COMPUTING FOR THE BLIND USER

by Aries Arditi and Arthur E. Gillman

Some special human factors must be considered in assembling a workable system

INEXPENSIVE COMPUTERS and nonvisual communications hardware have, in theory, made personal computing as accessible to blind as to sighted persons. But in practice, personal computing has its own special set of problems for the blind user. In this article we'll present some of the human-factors issues specific to nonvisual personal computing. Our concern is to make computers more accessible and efficient for blind and visually impaired persons. We hope our suggestions will be useful to individuals and to designers of hardware and software. Many of the improvements we discuss below can be implemented in several ways, often in more than one component of the system. They are intended to illustrate human-factors issues rather than to critique specific products.

The system we use as a basis for this discussion is a popular one for blind and visually impaired users and is inexpensive enough for home use as well as employment settings. It consists of an Apple IIe microcomputer operating under DOS 3.3, a Votrax Personal Speech System for voice output, and Raised Dot Computing's Braille-Edit program version 2.44a. [Editor's note: There is a more recent version of Braille-Edit with a number of new features and enhancements. See Henry Brugsch's review, "Braille-Edit", on page 251. Also, for an address list for manufacturers of products mentioned in this article, turn to page 208. | Most blind users have a printer for producing sighted (conventional) hard copy. Another useful peripheral is a braille printer, since braille hard copy is easier to proofread than voice output. While we will not specifically discuss braille hard copy, many of the human-factors issues discussed here are relevant to the design of braille printers.

Braille-Edit is an integrated software package designed to satisfy most blind users' needs to process documents. It is intended for use with a low-cost artificial-voice system such as the Votrax Personal Speech System or Street Electronics' Echo series (including the Echo+ speech synthesizer) and various other peripherals. Braille-Edit is not intended to (and does not) make all programs that run on the Apple accessible to the blind user, nor is it particularly useful in programming the computer. But it has a number of desirable utilities for the blind user, such as a translator of text to and from grade II braille (a commonly used coding system similar to Speedwriting shorthand) that makes impressively few errors and a copy facility for copying files to and from a paperless brailler such as the Versabraille from Telesensory Systems Inc. (TSI).

The hardware and software designed to make a system accessible to the blind user can be viewed as an...

El primer párrafo se podría haber escrito hoy… Cuarenta años más tarde, las tecnologías son 10 000 veces mejores, pero los problemas, o son los mismos o hemos introducido barreras nuevas para compensar las que (afortunadamente) hemos tirado abajo.

Y una vez cerrada la sección, nos pasamos a la guerra que se mantenía entre los ordenadores con CPUs Motorola 68000: el Mac, el ST y el Amiga (en orden rigurosamente creciente). Bruce Webster, uno de los autores estrella de la revista, hacía una comparativa que se alargó tanto que en este número solo cabía la primera parte, cuya conclusión es que el Mac está más maduro (llevaba mucho más en el mercado9, el 520ST es una ganga y el Amiga se veía lastrado por los problemas de Commodore, pero era el que apuntaba más maneras…

68000 Wars: Round 1

It is late November— almost Thanksgiving—as I finish writing this, and the editors back in Peterborough are screaming for my column. It's nice to be wanted, eh? However, if 1 don't wrap this up and upload it posthaste, I may be wanted in two or three states. Worse yet, a certain managing editor may end up being wanted for manslaughter, though I doubt if any reasonable jury would convict him. I must type faster...

I now have all three of the prominent 68000 machines: Apple's Macintosh, the Atari 520ST, and Commodore's Amiga 1000. I've had the Mac for nearly two years and the ST and Amiga for less than two months. And the single most common question I get these days is, "What do you think of the |one of the above| as compared to |one or two of the others above|?" Also, a lot of claims and counterclaims have been floating around concerning the relative merits of and problems with the three machines. In this column and the next few, 1 hope to sort out fact from fantasy and present some well-supported— if not completely objective— opinions. (Note: "Objective opinion" is an oxymoron, that is, a self-contradictory phrase, like "intelligent idiot" or "deliverable vaporware.")

Mac versus ST versus Amiga

The format of this column is simple. I'll take a number of different areas, one by one, and give my opinion on how the three machines stack up— who wins, who places, who shows. Where possible, this is based on direct experience. However, since I am not all-seeing or all-knowing, I have asked questions of those with more experience or knowledge, and I've done my best to acknowledge them at the end of the column.

Appearance and Physical Setup

The Macintosh wins this category easily. My 2-megabyte Mac has a 20-megabyte hard disk (MacBottom) and two disk drives (internal and external). The design is clean, attractive, professional, and unique. Better yet, the system takes up less than one square foot (9Vi by 9/2 inches) for the main unit and another 6 by 13 inches for the detachable keyboard, which can be easily moved 3 to 4 feet from the main unit. The Mac itself needs only one power outlet, though the hard disk requires its own as well. It definitely looks good in an executive suite and won't eat up all your desk space.

The Amiga comes in second, resembling the IBM PC (though, in my opinion, it looks nicer). The main unit is 17!/$ by 13 inches, covering more than twice as much desk space as the Mac. The monitor stacks nicely on top of the main unit, but a second (external) disk drive must sit to one side and takes up an 8- by 6-inch area. The detachable keyboard (6 by 16 inches) is larger than the Mac's, but it slides nicely under the main unit when not in use, and it can be moved almost as far as the Mac's. One warning, though: Since the expansion bus is on the right side of the Amiga, adding hardware is going to cause the Amiga to grow wider. The basic system (with two drives and monitor) needs two power outlets.

The ST comes in last, for reasons groused about last month. The main unit is 18!/$ by 9 l /2 inches. It therefore takes up less space than the Amiga, but neither the monitor nor the external disk drives can stack on it, so a complete system takes up much more desk space than either the Mac or the Amiga: A conservative estimate is about 21 by 21 inches. The keyboard is built into the main unit, so you don't have the additional space requirements for that, but you also don't have the flexibility of a detachable keyboard. The ST has a nice design but looks much like a home computer (which it is). Most unfortunate are the thick cables and external power supplies— one for the main unit and one for each disk drive. A basic system with monitor and two disk...

En nuestra sección habitual, temas que ni por casualidad encontraríamos hoy en una revista de informática… ¡las ecuaciones diofánticas!

Diophantine Equations

A man buys some x's at $154 each and some y's at $69 each. If he spends a total of $5000, how many of each did he buy?

Although this problem appears to be from a first-year algebra text, we find that the techniques required are not usually found in a "mainstream" course in mathematics. The equation 1 54x + 69y = 5000 has infinitely many solutions. However, assuming the man bought whole-number quantities, we want integral solutions [x,y] for the equation, and now we need a method for solving such equations.

Diophantine Equations

Equations of the form ax + by = c, for integral a, b. and c and integral solutions (x.y). are called Diophantine equations. No one is certain when or where Diophantus of Alexandria was born. Sources vary from "born about A.D. 50" to "flourished about A.D. 2 50." He is called "the father of algebra," having promoted algebraic notation and algebraic treatment of mathematical problems. Previously, such work was done by "rhetorical algebra" or geometric proofs.

A variety of methods are available for solving Diophantine equations. One of these is modulo arithmetic, a powerful and fascinating concept that 1 may explore more closely in a future column.

A very simple method of solving our original problem comes to mind. Since the equation is equivalent to y = (50001 54x)/69, we can simply try consecutive values of x (from 1 to 32 only) until we get an integral value for y.

Since we are mathematically inclined, such an inelegant approach may not sit well with us. Rather, we may prefer to look for a method of solution based on general principles of mathematics. What can we say in general about integral solutions for an equation of the form ax + by = c?

First, we can readily see under what conditions the equation would have no solution. Consider the greatest common denominator (GCD) of a and b. We will call it d. If d is not a factor of c, the equation will have no integral solutions. Why? Since aid is, by hypothesis, an integer and bid is also one, the value (ald)x + (bld)y will be an integer if x and y are integers. That is, the integers are closed under addition and multiplication. Thus, if eld is not an integer, either x or y must not be an integer.

Diophantus Meets Euclid

This leads us to Euclid's algorithm, which was the subject of my last column in January (page 397). If we employ Euclid's algorithm to determine the GCD of a and b, we can immediately determine whether there are integer solutions to the Diophantine equation by dividing the GCD into c. But we can use Euclid's algorithm for much more than that. To see how, let us reexamine the algorithm with an eye toward solving Diophantine equations. Figure 1 outlines the way the Euclidean algorithm finds the GCD of 1 54 and 69. Their GCD is 1, meaning that the two numbers are relatively prime. Now, to begin our examination of the way to solve Diophantine equations, let's modify our original equation to 154x' + 69y' = 1. That is, we will begin with the case where c is equal to the GCD.

In figure 2, I have rewritten the divisions of figure 1 as equations. In order to find integer values of x' and y' that solve the equation 154x' + 69y' = 1, all 1 need to do is substitute 154-2(69) for 16 in equations 2 and 3 and 69-4(154-2(69)) for 5 in equation 3. After collecting terms, I find that 1 = 13(154)-29(69). Thus, x = 13, y — 29 will satisfy the equation 154x' + 69y' = 1. We will call (13,-29) the basic solution to 154x' + 69y' = 1. Is it the only solution?

Let us write our equation in the general form again: ax + by = c. Now, let n be any integer and d be the GCD of a and b. If we add to the left-hand side of the equation, we haven't changed it...

(Y, para que no digáis que abuso del tema, me he saltado un artículo que comienza con «Windows can be implemented on almost any system with a memory-mapped display»…)

Me paro en la sección de BIX (ya recordaréis: el extracto en papel que hacía Byte de las conversaciones en su servicio en línea) para contemplar el nacimiento de IFF, el metaformato de archivos presentado por Electronic Arts que debería ser la base de cómo trabajamos hoy, y que permitía encapsular múltiples tipos de información (texto, gráficos y audio, para empezar) en un único archivo.

IFF Graphics Protocol

amiga/softw.devlpmt #157, from gregr [Gregg Riker, Electronic Arts]

TITLE: IFF (Information Format Files) Is Available!

I mentioned that I used IFF files with the SlideShow. Allow me to elaborate.

Electronic Arts has a general interest in promoting standards, so we knocked heads with some people at Commodore-Amiga and came up with IFF.

IFF is intended to be used by any and all interested developers. It offers a convenient way of allowing programs to exchange data with one another.

For example, Graphicraft will be able to exchange files with Deluxe Paint and other EA products. The design is extensible, in that you may add your own types to the standard. There are programs available in C (public domain!) that will read and write graphic images in IFF format.

If you're interested in a copy of the spec, please contact Rob Peck at Commodore-Amiga. He can supply you with a copy. If you have any problems or need more information, please contact Jerry Morrison at Electronic Arts, (415) 571-7171.

P.S.: IFF covers graphics, audio, and text and is expandable!

Y cierro con una curiosidad. A estas alturas deberíais estar tan enamorados y enamoradas de las ilustraciones de Byte como yo… y esto es tan claro que ya en aquella época la revista vendía ediciones limitadas de sus portadas:

Anuncio de dos ediciones limitadas de reproducciones de portadas de la revista. Una de ellas es una mano robótica dibujando una mano humana junto a una mano humana dibujando una robótica, y la otra es una ilustración de un disquete de cinco pulgadas y cuarto.

Y hasta aquí la Byte del mes. Si queréis hacer los deberes para el mes que viene, como siempre, aquí tenéis los archivos de la revista Byte en archive.org.

Pero, como venimos haciendo últimamente, no nos iremos sin darle un repaso a los episodios del mes de Computer Chronicles

El primero no es especialmente apasionante, y se dedicaba a las carreras profesionales en informática, incluyendo la emprendeduría… Una cosa a destacar es que no era totalmente necesario tener un grado en informática para encontrar trabajo en el campo: bastaba con unas cuantas asignaturas desde otros grados. Por cierto, que ya hablaban de la importancia de las competencias comunicativas… y ya se comentaba que las mujeres se iban a computer science y no a computer engineering. Tremendo, eso sí, en los breves del final del episodio, cómo AT&T presentaba un sistema de correo electrónico «de bajo coste»: ¡40 céntimos por enviar una página de texto! (Un sello costaba 22). Y con servicio de entrega en mano para personas sin correo electrónico por… ¡siete dólares y medio! ¡De la época! Todo ello mientras IBM presentaba un procesador experimental con 93 000 transistores (el procesador del iPhone 16 tiene… quince mil millones)

En el segundo episodio se hablaba de la computación en paralelo. Solo por ver un superordenador Cray de la época ya vale la pena darle al play. El H. T. Kung al que se entrevista a medio programa, por cierto, está a un grado de separación de Deep Blue, de unos de los primeros «gusanos» de internet, de la fundación de Y Combinator (una de las empresas de capital de riesgo más importantes del Silicon Valley)… y de las TPUs de Google. Se dice pronto. Y el Craig Mundie que sale justo después lideró la investigación y estrategia de Microsoft de 2006 a 2012.

Y para cerrar, dos episodios dedicados a los ordenadores y sus usos militares, otro tema del que seguimos hablando hoy. En esta primera parte se repasa la larga historia de esos usos militares, ya desde el ENIAC, y el enorme papel de DARPA en la investigación en el campo. No os perdáis las demostraciones de simuladores de vuelo de altísima tecnología que palidecen al compararlas con lo que podemos correr hoy en básicamente cualquier PC. Y la investigación en armas autónomas ya había comenzado, con el eventual premio Turing Raj Reddy.

Y en la segunda parte, sistemas informatizados en los barcos de la Armada de los Estados Unidos, capaces de disparar autónomamente (y el rechazo que provocaba la idea entre al menos parte de los militares de la época), o las «star wars» de Reagan… y menciones a coches autónomos.

Os diría que avanzaseis los deberes para anticipar el mes que viene… pero marzo fue el último mes de la temporada 85-86 del programa, y la siguiente temporada no llegaría hasta septiembre.

Y eso es todo por marzo… de 1986. El mes que viene, más.

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