[editor : Carl T. Helmers Jr.] [publisher : Virginia Peschke, Manfred Peschke] [art : Wai Chiu Li, Ellen Shamonsky] [cover : Thomas A Defanti and Guenther Tetz] #Magazine
#Magazine #Graphics
Extract : « The artwork on our cover this month and the samples found on the following pages were created by Thomas A Defanti and Guenther Tetz of the University of Illinois at Chicago Circle. The system used to create these works used a high level "Graphics Symbiosis System" (acronym: GRASS) grafted onto a PDP-11/45 computer with a Vector General 3DR display scope, a data tablet and 30 channels of analog input and output for interactive control of the programmed parameters of the display. Consider it in some sense the visual equivalent of a Moog synthesizer's audio functions. A more complete description is found in a paper entitled "The Digital Component of the Circle Graphics Habitat" which was published on pages 195 to 203 of the proceedings of the 1976 National Computer Conference (a monstrously thick book available from AFIPS, the American Federation of Information Processing Societies, 210 Summit Av, Montvale NJ 07645). [...] »
#Abstract
One whole subset of the personal computing world is provided by the users and manufacturers of programmable calculators. All the problems of creating applications software which users must solve on bigger machines are present, and often intensified by lack of scale, in these smallest of personal computers. William B Jenkins gives some useful information on the general process of creating an application program, and the specific problems of doing it on an SR-52 programmable calculator, in his article entitled How to Write an Application Program.
One of the conveniences of the 6800, 6502 and similar microprocessors is a relative branch method which allows one to construct position independent code which can be relocated by simply moving the programs involved. But these forms are typically limited to a 1 byte displacement, a limitation which Robert Borrmann shows how to overcome in the 6800 case by using appropriate stack manipulations and "long branch" subroutines. Read his article Relocatability and the Long Branch in this issue.
Looking for a different type of board game to play on your computer? How about the current game fad Othello (known as Reversi in England)? In Othello, a New Ancient Game Richard O Duda provides a short article with details for this game of skill and tactics.
This month, Mike Wimble concludes his 3 part series about an APL interpreter with An APL Interpreter for Microcomputers, Part 3: Mathematical Processing. With this segment, the functional design of interpreter is completed. Watch future issues for results of the Great APL Interpreter Contest inspired by Mike's article.
At first glance a simulator designed to run on the computer it is simulating may not seem very useful. Kin-man Chung feels differently for he wrote one. His article, An 8080 Simulator, describes one such program and gives ideas on how it can be put to good use.
For those who tire of the many versions of the Star Trek game, there are many much more interesting and interactive graphics games to consider. In his article, How to Implement Space War, Dave Kruglinski provides readers with a version of the classic graphics game, Space War, which was originated in the early 1960s by students at MIT, and has taken an amazingly long time to be documented in versions for personal computers. Dave's 8080 version is complete with orbiting space ships, spiraling torpedoes and dynamic effects implemented with limited resolution point plotting graphic display.
Is your computer cold ? Add some vitamin C for a new high in resistance to frustration and rude language. Turn to J Gregory Madden's C: A Language for Microprocessors?, a description of an excellent structured programming language which could be adapted to microprocessor use from its origins on large PDP-11s with the Unix operating system.
Do you use cassettes as your principal mass storage medium? Then you will benefit from Wayne D Smith's discussion of Fundamentals of Sequential File Processing when it comes time to write software using such media.
Want to get involved in pitch generation for computer music synthesis? Thomas Schneider explains several approaches you might consider in his article, Simple Approaches to Computer Music Synthesis.
Using flowcharts to gather the logic for a program does not mesh with the current trend of structured programming. One technique that is directed towards the structured program approach is the use of Warnier-Orr diagrams. Use of these diagrams, as described by David Higgins in his article Structured Program Design , will result in accurate, well structured programs that will work correctly the first time they are executed.
The home computer has many uses besides number crunching and game playing. One of these uses, discussed by David Holladay in Computer Information Arrangement, is an information retrieval system. This type of system could be used to make your own dictionary type reference, help keep track of your files with cross reference, or simply make a personal version of the Schwann Catalog for your record collection.
Sensible automobile owners have long had the habit of recording mileage and gasoline filling figures at each visit to the service station. In this issue John P Bauernschub explains how to Analyze Your Car's Gas Economy with Your Computer in a short article presenting a complete BASIC program for this application.
Are you looking for a stimulating thought game to play with your computer? The game of Mastermind as described by W Lloyd Milligan in his article of that name will force you to think in a very logical manner if you want to have a chance at winning.
[author : Carl Helmers] #Edito
Extract : « (or What the World Needs Is a Good Mass Produced High Resolution Color Display...)
This commentary on the possibilities of color imagery and display was inspired by a fantastic image processing system which was surely witnessed by many of the 36,000 people who thronged to the National Computer Conference in Dallas TX this past June. The system in question is produced by a company called Comtal, located in Pasadena CA. It is referenced variously as the Model 8000-S and "Vision One" in the literature I picked up at the site of the demonstration in the main exhibit area of the conference.
This Vision One system is not exactly a personal computing product. Its price tag in the $70,000 range makes it a candidate for laboratory or institutional use, but hardly a peripheral for the individual of ordinary means. Its characteristics include a built in LSI-11 computer with extensive software, direct refresh raster graphics hardware with 512 by 512 8 bit picture elements (ie: 262,144 bytes in its serial CCD refresh memory), and a hard surface disk drive. One of the prime practical applications of this system is its use by the Jet Propulsion Laboratory of Pasadena as the analysis and enhancement processor for the color photos returned from the Viking landers on the planet Mars. But the artistic and personal use attributes of such a color display are immense, as was demonstrated by the "show off" sequences which were viewable at the NCC show. These included false color processing of digitized pictures, as well as dynamically changing kaleidoscopic abstract patterns. [...] »
TABLE OF CONTENTS
[theme : Programming Techniques] [author : Borrmann] #Listing #Assembly #Programming
Extract : « A position independent relocatable program is a program that can be moved to any convenient place within your memory space, and executed without any changes. One of the very nice things about the Motorola 6800 instruction set is the relative addressing mode used in its branch (BRA) and branch to subroutine (BSR) instructions; instructions using this addressing mode are inherently relocatable without patching. [...] »
[theme : Interpreter Design] [author : Wimble] #Algorithm #Programming
Extract : « In part 2 of this 3 part series (see last month's issue) I covered the expression evaluation portion of an APL interpreter. This month's concluding installment deals with mathematical processing. Mathematical processing is a 2 part function: recognition followed by interpretation. Both of these topics are covered here, followed by a short summary. [...] »
[theme : Software] [author : Kruglinski] #Listing #Assembly #GameRacingPiloting
Extract : « You say you'd love to go and play "Pong," "Tank" or "Shoot 'em" down at the corner tavern but they won't let you in because you're not old enough? Or maybe you learned to play Space War back in college on a turbocharged PDP 911/S megacomputer and you don't think your poor microcomputer could keep up? Or perhaps you hate BASIC but can't think of a good reason to mess with 50 pages of assembly language. Even if you don't fit into any of the above categories, merely reading this article will sufficiently disturb your mental equilibrium to start you on your way to being a Space War freak, making all other problems fade into insignificance. [...] »
[theme : Applications] [author : Bauerschnub] #Listing #BASIC #DataAnalysis #Transport
Extract : « How well is your car performing? Is it matching the EPA miles per gallon ratings that the manufacturer posted on it? Is it time for a tune-up? Here is a system that will produce these answers and provide a worthwhile application for your personal computer. [...] »
[theme : Software] [author : Jenkins] #Algorithm #Listing #TI
Extract : « The Texas Instruments SR-52 is a very impressive machine for its size. Several different libraries of programs are provided that include engineering, finance and games applications. The game programs do, of course, provide the easiest way to impress your friends with the power of the SR-52. This is no different from using game programs with any computer system. For personal use, though, games can quickly lose their glamour. When this happens, it is time to learn how to program. [...] »
[theme : Software] [author : Duda] #Listing #BASIC #GameBoard
Extract : « Othello is a 2 person board game based on the 100 year old game of Reversi. It resembles GO, but is much faster paced and easier to learn. If you are not already an Othello buff, this program will both teach you the game and provide an entertaining addition to your games library. [...] »
[theme : Software] [author : Chung] #Algorithm #Listing #Assembly
Extract : « A simulator can be very useful to the personal computing experimenter for a number of reasons. The idea of a simulator is to perfectly duplicate the operation of a certain computing system using the instruction set of another computer. For example, suppose you have an 8080 program which you want to run on your 6800 system rather than completely write a new program. Since the simulator acts functionally like an 8080 processor to interpret the 8080 object code bit patterns, its hardware registers and program counter, it is possible for the 6800 system to run the 8080 program. Another attraction of a simulator is that in software it is possible to achieve a number of debugging and checkout functions as a part of the simulator itself, since the machine being run is always under total software control. When a simulator for machine X is run on machine X, these attractions can justify the use of the simulator. [...] »
[theme : Applications] [author : Smith] #Electronic #Algorithm #Storage #DataManagement
Extract : « The newly available floppy disk drive units have opened many new areas of applications for microprocessor users. In the area of high utilization data, and fast interactive programs, the capabilities of random access disk storage devices are unequaled. Unfortunately, the price of such units often puts them outside the budget of personal computer users. Even when disk units are available, the advisability of using these devices for storing low utilization programs or data may be doubtful. You don't really need a $1000 auxiliary storage device to maintain a Christmas card list which is used once a year.
The new, special design digital cassette recorders have also generated a great deal of interest. These units allow software control of all tape functions, and provide for tape position sensing. While the price of these units is about half that of a single disk drive, they are still somewhat expensive. Like disk units, they also require fairly sophisticated interface hardware for proper operation. [...] »
[theme : Languages] [author : Madden] #Initiation #C #Programming
Extract : « I would first like to congratulate Peter Skye for his work on the high level language project! The interest created by his letters in recent BYTEs has helped to prod the emergence of a high level language. PL/I is a fairly popular language, and a good choice as an initial high level machine independent language. But what about other languages? Is there perhaps one which might be a better choice? Let's take a brief look .... [...] »
[theme : Hardware] [author : Schneider] #Electronic #Audio
Extract : « In order to produce a musical output, we must at least create a pitch output under control. This is but a starting point, since more complicated waveform and envelope generation is also useful in music. [...] »
[theme : Software Design] [author : Higgins] #Method #Listing #BASIC #Programming #Book
Extract : « In the world of electronics, no experimenter in his right mind would build a circuit by throwing a few parts together with some wire and some hope, then attaching a line cord and plugging it in to see if it works. Not only are you likely to destroy some very expensive parts, but it is also a good way to get fried, or at least get a new hairdo.
Yet, after all the trouble that a serious microcomputer hobbyist will take to insure that his circuit is put together correctly before he ever turns it on, he will invariably try to program his new computer by using a technique analogous to the one above. That is why his programs almost never run right the first time, if indeed they ever manage to run right at all. It is also why many microcomputer buffs stay up until odd hours of the night drinking coffee by the gallon in an effort to find that one little bug.
But there is hope. I'm sure that nearly everyone involved with computers has heard something about structured programming in one form or another. It is not really a new technique, having been preached about for many years. However, the tools and methodologies available to design programs have changed radically over the years. [...]
[...] Bibliography
1. Orr, Kenneth T, Structured Systems Development, Yourdon Press, New York, 1977.
2. Warnier, J D, Logical Construction of Programs, Van Nostrand Reinhold Company, New York, 1976. »
[theme : Applications] [author : Holladay] #Storage #DataManagement
Extract : « An examination of the small system computer field might lead the observer to take a limited view of the potential uses of small systems. This is unfortunate, because a computer, even a small one, can do more than play games or make lights blink.
One general application of computers is the information retrieval system. A classic goal of information retrieval is the construction of a system that absorbs the contents of books and can answer questions concerning the information contained in them. This goal has been unapproachable in even the largest of computer systems. The best approach is to put the burden of intelligence on the user's shoulders and make use of the computer's bookeeping ability. This reduces the program to a large scale sorting system tailored to a microcomputer's capabilities. [...] »
[theme : Games] [author : Milligan] #Listing #BASIC #GamePuzzle
Extract : « One of the most interesting conventional (ie: noncomputer) games on the market is "Mastermind," distributed by Invicta Plastics, Suite 940, 200 5th Av, New York NY 10010, and available in many local stores. Mastermind involves deductive logic, hypothesis testing and probabilistic inference. In Mastermind, the players take turns as "codemaker" and "codebreaker." The codemaker sets up a concealed row of four colored pegs from a set of Red, BLue, BRown, Green, Yellow and Orange pegs. It is acceptable to use the same color or colors more than once. In version 2, a more advanced game, empty Spaces are also permitted. (The bold face characters are abbreviations recognized by the BASIC program.)
The codebreaker has ten tries (rows) in which to discover the secret arrangement of colors in the concealed row. [...] »
#Book
Extract : « Chess Skill in Man and Machine edited by Peter W Frey, Springer-Verlag, New York, 1977. Hardcover $14.80. [...] »
#Association