[editor : Carl T. Helmers Jr.] [publisher : Virginia Londoner, Gordon R Williamson] [art : Wai Chiu Li, Christine Dixon, Holly Carmen LaBossiere, Deborah Porter] [cover : Robert Tinney] #Magazine

#Abstract

This month's cover theme is "Computers in the Laboratory." Personal computers can be employed as a tool of analysis and control in scientific applications. We celebrate this theme with a fantasy suggestive of one area of scientific application: an advanced color-graphics-oriented personal computer is shown over a Bunsen burner on a beaker stand. On the terminal is a high-resolution image of some liquid boiling. This computer, without floppy-disk drives, certainly suggests a future direction: built-in, permanent mass storage with sufficient capacity to eliminate any need for removable media. We might even conjecture that a pattern is shown here being "boiled" into a bubble memory.

Hunting the Computerized Eclipse

[author : Carl Helmers] #Edito

Extract : «  As noted last month, the subject of this editorial is completing some technical details of a project that has consumed all my spare time during the closing months of 1979. This project is the practical execution of what was really a pipe dream last March when the July 1979 editorial ("Computers and Eclipses") was written. The July editorial was inspired by my travels the previous February to see my first total solar eclipse from a roadside near Roundup, Montana. During that event, which took place in cold wintry weather, all my pictures were taken manually using the telephoto lens on my Nikon F2A camera. I knew there had to be a better way of controlling my camera during an eclipse event, and set about concocting a suitable first approximation of a computer-control method.

As a result of writing about the problem, I received a letter from and eventually met one of our readers, Norm Whyte, of Monte Rio, California. In the course of the ensuing correspondence and telephone calls, we developed a degree of friendship based on mutual interests in matters scientific and technological. The result was that since there were a couple of berths left in the travel plans for Norm's eclipse trip to Kenya during February 1980, I was able to become more serious about making a real version of the fantasy sketch outlined in last July's editorial.

With the decision to go made, the next decision was how to implement the system. The number one step, of course, was to order a motor drive and a magazine back for the Nikon camera. I quickly came to the conclusion that if I were going to travel all the way to Kenya to watch 4 minutes of celestial follies, more than thirty-six exposures would be appropriate. The Peterborough Camera Shop did their job, so by September I had the motor drive, and I had the magazine-back and bulk-loading accessories by mid-October. The camera system and methods of developing a 250-frame roll in a small batch tank were debugged at the camera store in November, through the efforts of its owner Wayne Esty and lab technician Skip DeLiquori. [...]  »

TABLE OF CONTENTS

Steve tells you how the Intel 8088 is well-suited for building a minimum-configuration 16-bit computer.

[author : Steve Ciarcia] #Microprocessor #Electronic

Extract : «  [...] The exciting items in microcomputing these days are the 16-bit microprocessors made by companies such as Intel (the 8086), Zilog (the Z8000) and Motorola (the M68000). All of these devices, although they differ in internal architectures, commonly claim to have compressed the power of a minicomputer within a single chip of silicon. Most notably are the 16-bit data bus and increased addressing space. A 20-bit address can directly address a megabyte of memory.

There seems to be little doubt in the minds of microcomputer-system designers that the 16-bit processors are the wave of the future. Already some major manufacturers are designing the new processors into intelligent terminals, word-processing systems, and other equipment. The day when this revolution within a revolution will affect the personal and small-business computer market-place is not too far away.

But if it is obvious that the 16-bit machines will be the trend of future product technology, it is equally obvious that it is relatively difficult for the designer to make a leap from the 8-bit world of the 8080, Z80, 6800 and 6502 to the emerging 16-bit world. The 16-bit instruction sets are more complex. The 8086, for instance, has a repertoire of some 133 instructions, as compared to seventy-eight for the 8080. Simply because of the larger range of memory that can be addressed and because of address segmentation, addressing of memory is more advanced. Also, the register set is more complicated, and the types of operands with which the processor can work are more extensive.

As complex as the 8086 or any other 16-bit microprocessor is from a software viewpoint, it is in the design of hardware circuits to work with the 16-bit processors where the real complexities arise. Peripheral interfaces and existing hardware systems are generally based on an 8-bit data bus. When your whole design is built to make efficient use of an 8-bit data bus, converting to a 16-bit architecture is not a simple matter of replacing the processor. This incompatibility dictates substantial design changes to take advantage of the new 16-bit microprocessor. [...]  »

Learn how to use a computer to explore the inner processes of a molecule by finding solutions to the Schrödinger wave equation.

[author : Michael Liebl] #Listing #BASIC #Mathematics #Physics #Book

Extract : «  Years spent subconsciously gathering and sifting data in our daily lives gives each of us a common sense intuition for the laws of nature. But our intuitive understanding of how nature works often fails when we explore worlds beyond the realm of common experience. In the submicroscopic world of atoms and molecules, matter exhibits unexpected behavior attributable to its dual nature as particle and wave. Scientists interpret this world with the aid of quantum mechanics, a discipline that more often than not involves long and complicated mathematical operations.

The computer, by virtue of the ease and speed with which it handles such operations, has become an invaluable tool in the quantum-mechanical study of atoms and molecules. This article describes a program written in BASIC which allows anyone with an elementary understanding of quantum mechanics to investigate the behavior of an electron in the bond formed between two atoms in a diatomic molecule. [...]  »

After developing a general algorithm last month, Scott now explores several modifications that may be applied to typical conflict-simulation problems.

[author : Scott T Jones] #Method

Extract : «  In part 1 some general terrain problems were defined. These were problems that could be expressed in terms of movement on a map, with terrain defined as any map feature affecting movement. By superimposing a rectangular grid and coordinate system on these maps, we were then able to represent the terrain with a set of boolean arrays or terrain masks. Movement, distance, and the concept of movement cost for different types of terrain were also defined. A scatter function was then defined to generate scatter maps representing all possible movement within the limits imposed by the terrain.

Finally, we demonstrated the use of these scatter maps to solve such problems as the feasibility of road construction within cost restraints and the determination of an optimal path between two points on a map, across variable terrain.

Part 2 is concerned with the application of these techniques to the problems encountered in conflict simulations. [...]  »

For hobby applications where an isolation transformer is too big and expensive, this relay-based circuit can provide some protection from power-line wiring errors.

[author : Neil Schneider and Bror Erickson] #Electronic

Extract : «  Several years ago while he was working with color organ circuits, a friend of mine connected a color organ to an All American Five radio receiver. For those of you who are too young to remember, the All American Five was a popular five-tube radio design containing no power transformer. To my friend's surprise, and fortunately not to his harm, the connection of his color organ to this radio resulted in foot-high flames as the audio output transformer burned.

The radio receiver had a "hot" internal chassis which was isolated from the outside world by its plastic case. The power cord was not polarized to connect the chassis to the low side of the AC power line. As my friend made his connection, he placed the 117 VAC power line current across the 8 ohm impedance audio-output secondary winding of the transformer, and across the speaker. This resulted in flames and a destroyed radio receiver. [...]  »

This game uses the Motorola MEK6800 D2 kit. It can be interfaced to display the landing approach on an oscilloscope.

[author : S J Houng] #Listing #Assembly #GameRacingPiloting #Book #Electronic

Extract : «  This article describes a program that simulates the landing of a jet-propelled craft on a random surface. The surface is generated by a random-number generator. As in photo 1, the craft can be steered vertically or horizontally by the firing of the main jet, the side jets, or both of them. During the dynamic simulation, the craft will move vertically along the central vertical line of the oscilloscope. The horizontal movement of the random surface causes the craft to appear to move in the opposite direction.

The sequence of the simulation is as follows:
• The dynamic equations of the craft are solved by Euler's method. The solutions are velocity and displacement.
• The craft is displayed according to the vertical displacement, and the jets are made visible when they are fired.
• The random surface is displayed relative to the horizontal displacement of the craft. There are 256 segments of random surface which form a continuous terrain. Only five surface segments are shown on the oscilloscope at one time.
• When the craft has touched down on the surface, the vertical and horizontal velocity are compared with the crash velocity. If the craft exceeds the crash velocity, it will disappear from the screen. If it lands safely, it will remain on the surface waiting for liftoff. [...]  »

An inexpensive way to add front-panel functions to a minimal microcomputer system.

[author : Albert S Woodhull] #Electronic #Listing #Assembly

Extract : «  How do you take the very first steps into learning about microprocessors? An article by Sol Libes ("Notes on Bringing up a Microcomputer," January 1978 BYTE, page 162) described a procedure for the initial testing of a homebrew microcomputer which uses simple procedures to determine whether or not address and control signals are functioning properly. The procedures described are effective, but in order to use them you need a way to load some programs into memory.

If you are building a kit or following a complete microcomputer design, then the details of input and output interfacing will be provided for — a bootstrap program will either be available in read-only memory or can be easily entered from a front panel. But suppose you are just feeling your way along, as I did. I had obtained an 8080A chip set through Intel's University Program, but I had no intention of building a real computer. I had full access to an Altair and an IMSAI at the college where I teach; I wanted only to learn a little about how the hardware worked. I certainly did not want to spend either the money or the time to imitate the Altair's front panel. The following is a description of how I solved this problem in an economical way. [...]  »

The program presented here uses the high-resolution graphics ability of the Apple II to give a visual representation of molecular bonding.

[author : Randall S Matthews] #Listing #BASIC #Physics #Graphics

Extract : «  To an organic chemist learning to program a newly acquired microcomputer (in my case, the 16 K byte Apple II), the challenge of "teaching" chemical principles to the computer naturally arises. For example: can the Apple II learn the rudiments of structural organic chemistry, and use that knowledge to assemble and draw simple molecules? This subject is usually covered early in the first semester of sophomore organic chemistry. I decided to write a BASIC program that would accept a hydrocarbon molecular formula as input, and then randomly construct a molecule fitting that formula and draw its structure using high-resolution graphics as output. [...]  »

This is a three-dimensional, 4-by-4-by-4, tic-tac-toe game that can play against a human opponent. The program has ten levels of expertise, is written in BASIC, and can be modified to run in two dimensions.

[author : J Roehrig] #Listing #BASIC #GameBoard

Extract : «  This article describes Super TIC, a program that plays three-dimensional (4 by 4 by 4) tic-tac-toe. It was written specifically for microprocessors and has the following features:
• It is fast, despite the fact that it checks every possible move. The response time is 13 seconds per move (worst case) using an IMSAI 8080 computer with North Star BASIC, and it averages less than six seconds per move.
• It gives a graphic display of the game (designed for a 24 line by 80 character terminal) without requiring a graphics board.
• It plays at ten different levels of skill without requiring modification of the program.
• One program line can be modified to change the program's strategy so that it plays defensively or aggressively.
• The modification of four lines (see listing 2) allows the game to be played in a two-dimensional 4 by 4 format. [...]  »

A first look at a personal computer from a company esteemed for its calculators and minicomputers.

[author : Christopher P Morgan] #ComputerDesktop #Review

Extract : «  A question often heard in personal computer circles is, "When is Hewlett-Packard going to bring out a personal computer?" The question has been answered, and the new HP-85 computer is quite a system.

Hewlett-Packard (HP) has long been a respected manufacturer of minicomputers, desktop calculators, and handheld calculators; the high quality of their electronic test equipment is well known to the engineering community. Hewlett-Packard also has the reputation for being a careful, conservative company, and the HP-85 is, not surprisingly, a logical outgrowth of their desktop and hand-held calculators.

We recently had the opportunity to audition the HP-85. Our preliminary findings are listed below. [...]  »

James provides us with a direct comparison of the TRS-80 computer with an IBM System/370.

[author : James R Lewis] #Listing #BASIC #Assembly #Performance

Extract : «  I have been asked to evaluate the performance characteristics of numerous hardware and software computer products in my capacity as a systems programmer. In late 1978 I acquired a Radio Shack TRS-80 personal computer system with Level I BASIC and 4 K bytes of memory. I did not consider a performance evaluation; after all, this was my own toy. I did not have to respond to any requests for performance improvements or evaluations. Only my personal satisfaction was important.

As it turned out, I was satisfied, but my friends and colleagues were not. They were continually asking, "How fast does your toy run?" or "What new tricks have you taught it now?" It seemed that a comprehensive performance testing and evaluation plan was called for. I decided to compare my TRS-80 personal computer with one of the IBM computers (a System/370-148) at work. Since I was also in the process of converting from Level I to Level II BASIC and acquiring more hardware, I wanted to see if I could verify the performance improvements claimed by Radio Shack. [...]  »

These authors describe a situation in which a specialized tool was replaced by a general-purpose minicomputer.

[author : Peter A Santi, John Fryhofer and Gregory Hansen] #Computer #DataAcquisition #Mathematics #Listing #Pascal

Extract : «  A planimeter is an instrument (formerly mechanical) for measuring the area of a two-dimensional figure by tracing its perimeter. Area measurements obtained from planimeters are useful for a variety of applications, such as cartography, geology, metallurgy and biology. Our biomedical application requires area and length measurements of irregularly shaped two-dimensional figures. To this end an electronic planimeter has been designed consisting of a Summagraphcs (Summagraphics) Bit Pad and a Terak microcomputer programmed in UCSD Pascal (Version 1.5).

In practice, a user specifies a scale factor and then traces the boundary line of a figure using either a stylus or a single-button cursor. To improve the accuracy of the area measurement, the program detects closure (ie: when the end of the tracing meets the beginning) and displays the calculations. You can trace additional figures with the same scale by using only the stylus or cursor switch. Using this electronic planimeter, area and perimeter length measurements are more accurate and can be obtained faster than with a mechanical planimeter. [...]  »

The need to convert an assembler mnemonic to the hexadecimal object code often occurs when programming the 8080 microprocessor family. Here is a helpful summary of related information.

[author : D Martin Harrell] #Assembly #Programming

Extract : «  Manual conversion between assembly language mnemonics and hexadecimal object code can be tedious — particularly if much code is involved. However, the task does not have to be overwhelming. A conversion table helps immensely and is also a good training aid for novice programmers. It presents the entire instruction set in compact form, revealing useful patterns, and also inconsistencies. [...]  »

Techniques to enable your computer to detect and correct typographical errors In assembly-language programs.

[author : Roger A McGregor] #Assembly #Programming

Extract : «  GIGO (garbage in, garbage out) is an expression heard so often by programmers that it is accepted as truth and even offered as an excuse for poorly written programs. It is a truism that ought to be examined, especially in the area of human prepared input that is typed.

If the instructions in figure 1a are entered instead of the correct instructions of figure 1b, the great majority of microprocessor assemblers will be unable to locate any of the program symbols. This inability compels the user to go through the tedious process of calling an edit program, making corrections, calling the assembler, and trying once more to assemble the source code, hoping that no new errors have been introduced. This procedure can be very time consuming; it is always frustrating. An examination of how the errors are detected in a normal assembler or compiler may shed light on how an automated correction can be attempted.

Normally, after a symbol has been segregated from the source text, it is passed to a symbol table lookup routine as a search argument. The function of the lookup routine is to find an entry in the symbol table whose symbol matches the search argument, and to either return that entry (a hit) or set some indicator to inform the calling routine of an unsuccessful search (a no-hit). Both hits and no hits are valid returns, depending on the pass being made on the source code. [...]  »

Gear-Ratio Calculations for Bicycle Derailleurs and many more

#Book

Extract : «  What Computers Can't Do, Hubert L Dreyfus, Harper and Row, New York, 1972, hardcover, 259 pages, $10.95 [...]

Brain, Mind and Computers, Stanley L Jaki, Gateway Editions, 1969, softcover, 267 pages, $4.95 [...]

Z80 Software Gourmet Guide and Cookbook, Nat Wadsworth, Scelbi Publications, 1979, softcover, 322 pages, $14.95 [...]

BASEX, Paul Warme, BYTE Books, Peterborough NH, 1979, softcover, 97 pages, $8 [...]  »

The Direct Impact of the Computer

Cutting the Gregorian Knot

The Periodic Chart at Your Fingertips....