[editor : Carl T. Helmers Jr.] [publisher : Virginia Peschke, Manfred Peschke] [art : Matthew Arnorld, Noreen Bardsley, Mary Jane Frohlich, Lynn Malo, Bill Morello] [cover : Robert Tinney] #Magazine
#Abstract
Terry Dollhoff provides readers with some food for thought on hashing techniques. Turn to Making Hash With Tables to find out what it means to hash data as a method of improving table access time. The straightforward way of seeking data in a table (searching each element in turn) is far from the most time efficient, as you'll discover by considering Terry's arguments.
For an output only interface, you don't necessarily have to use a UART to drive a Teletype printer. Gregory C Jewell shows How to Drive a Teletype Without a UART using five standard TTL integrated circuits.
How do you drive a tape recorder's head directly, and read data directly? If you read David M Allen's article in this issue, you'll find out that Saturation Recording's Not All That Hard after all. David shows a simple tape driver circuit, input signal processor and the design of software for direct digital recording with audio tape heads on cassette recorders.
Watts Inside a Power Supply? Find out by reading Gary Liming's account of power supply basics. You'll find that there are indeed watts lost inside a power supply, the reason these items invariably come with some form of heat sink. After reading Gary's article you'll have some good background information in your memory banks for evaluating the various power supply schemes which are used in practice, and why such schemes are used.
Altair BASIC (in whatever form you have it) is an excellent aid to the utilization of an 8800 system. However, there is that residual problem of putting in a 20 byte bootstrap program every time you turn power on. In this issue, a short article by Jim Kreitner shows you how to Pick Up BASIC by PROM Bootstraps.
Who knows what the bears and bulls will be doing next in the stock market? Play Black Friday, a BASIC game by Bob Baker, and you'll get a heuristic feel for what happens through the powerful tool of simulation. Will X-Pando do better than Slippery Oil after a simulated year of trading? Play the game and find out.
Newcomers may wonder what is meant by the term "direct access storage device." This is the most useful form of mass storage, a form which is the dream and goal of every small system hacker who has passed the beginning stages of programming applications of his or her computer. To help define the terminology for the novice, reader Curt Hill has provided an elementary article on the types and uses of direct access storage.
The SYS 8 monitor as it is supplied by IMSAI and Processor Technology is a self-contained operating system for 8080 based microprocessors which comes equipped with its own set of executive commands. These commands are used for calling programs that are resident in the system. Wouldn't it be great if programs that are not part of the monitor could be part of the executive command table? This was the conclusion of Willard I Nico. He decided to have easy availability of his most used programs by adding them to the executive command table. He describes how you too can easily accomplish this in his article SYS 8 1/2 - Your Own Executive Commands.
Representations of two dimensional game boards as the bits of various bytes in your computer's memory can often be chosen to help facilitate evaluation and strategy computations. In Computer Models For Board Games, Russell R Yost Jr presents some basic background information on the problem and suggestions for representations useful in the games of TACTIX and HEXPAWN.
For use when testing out your hardware, the idea of The Built-In Logic Tester can prove quite useful. K W Christner discusses the concept in a short article on his version of a logic probe.
Riddle of the Month: What is not like an elephant with a suntan?
An EROM which forgets its memory pattern due to ultravilet light.
Build the "Coffee Can Special" EROM Eraser described by Lawrence Burbey in order to convert white elephant EROMs into blanks ready for reprogramming.
Video interfaces often produce an EIA composite video signal as the principal output. What do you do when you have a commercial digital monitor with separate sync inputs of the type used in display terminals? Why, that's when you follow David Rosen's lead and Separate Your Sync by tapping the interface at a nonstandard point.
June BYTE had an article on ELM, an Eloquent Little Monitor. In this issue, author G H Gable describes a method of Using Interrupts to Speed Up an ELM. The use of interrupts and a tape drive with a direct memory access interface make a valuable extension of the basic monitor concept.
In June and July a survey was conducted of computer hobbyist clubs in the US and Canada. The questionnaire covered such areas as number of members per club, types of computers owned, applications for the computers and the members' backgrounds. In his article, A Computer Hobbyist Club Survey, David Caulkins releases the results of the survey and explains some of the conclusions that he has reached as a result of the survey.
[author : Carl Helmers] #Edito
Extract : « With the beginning of the new year, it's time to return to the theme of the "ideal" personal computing system, the ne(c) plus ultra in terms of design finesse, convenience and low price. In short, a quality packaged product ready to be programmed by the user... the same concept found in the programmable calculator, but applied to the general purpose computer system instead. This product is on the way. My "authoritative" pronouncement on the future of the field during 1977 is that 1977 is to be the year of the "Appliance Computer." Now that I've made my pronouncement, you ask in reply "now how can Helmers make a crazy statement like that?" The rest of this month's commentary concerns the reasons for this summary of the coming year, a view from the root node of an information tree.
Quite simply, the "appliance computer" is the concept of a true finished product desk top general purpose computer which can be purchased at your local dealer, a complete package of hardware with supporting systems software at a reasonable price. It is the software experimenter's dream machine, a computer where the only concerns are the generation of programs and the hardware is just assumed to exist and work properly. It is the starting point of applications and systems programming experimentation. The appliance computer is the personal computing system which does not require that its owner own an oscilloscope, a complete electronics laboratory, or have experience in the repair and tuning of hardware. [...] »
TABLE OF CONTENTS
[theme : Software] [author : Dollhoff] #HowItWorks #Listing #Assembly #Programming
Extract : « Hashing is a technique used to speed up table searching operations by making position in the table depend upon the data. Many newcomers to programming reject hashing as an overly complicated technique useful only by the designer of exotic systems software, but this is not the case. Any large program, written for fun or profit, may include tasks of accessing, storing, or modifying entries in a table or array. Most game playing programs include a number of such tasks. Application of hashing techniques can often dramatically improve the performance of these programs. This article will explore the use of hashing (sometimes called key-to-address transformation) as a simple but effective mechanism for accessing stored data. These techniques can be used in applications where the data is organized randomly and where each item has a unique key associated with it. [...] »
[theme : Hardware] [author : Jewell] #Electronic #Interface
Extract : « This parallel to serial converter performs functions similar to any other; however, this circuit is designed with the microprocessor hobbyist in mind. This conversion design is simple and extremely easy to trouble shoot. All the logic involved is out in the open, so it can be examined with an oscilloscope. [...] »
[theme : Mass Storage Technology] [author : Allen] #Electronic #Algorithm #Storage
Extract : « The cassette recorder is doubtless the most common and popular peripheral device among hobbyists, and considerable attention has been paid to its employment. Almost all of this attention has been directed toward the use of unmodified audio recorders. This complicates a simple problem. Saturation recording is the logical way to store digital data on tape, so why use audio? Saturation recording is more straightforward, more flexible, and inherently more reliable. The design presented here uses only a few garden variety integrated circuits; no PLLs, no UARTs. It presupposes no encoding scheme, so the user is free to pick and choose among the various techniques available. I used ordinary NRZ (Non Return to Zero) ASCII because it was easiest to write software for. [...] »
[theme : Hardware] [author : Christner] #Electronic #Diagnostic
Extract : « After unsuccessfully attempting to debug a friend's microprocessor system using the only piece of test equipment he had, a VOM, I decided that every system should have a built-in logic tester. A simple circuit with LED indicators would be adequate to troubleshoot most bad components, open circuits, and short circuits. The logic tester, permanently mounted in the chassis or on one of the printed circuit boards and powered by the computer's +5 V power supply, would always be there to make quick checks. [...] »
[theme : Hardware] [author : Burbey] #Electronic
Extract : « If you plan to reprogram your erasable PROMs (EROMs) you have probably noticed a general lack of information on cheap ultraviolet sources to do the job. [...] »
[theme : Hardware] [author : Rosen] #Electronic
Extract : « While building my television typewriter (from the Southwest Technical Products kit), I searched around the various surplus stores and TV repair shops in my area for a second hand TV receiver to use as a display. Fortunately, I came across a Sylvania model SDM-5035 12 inch video monitor. This monitor was once part of a data processing terminal. It is designed specifically for optimum legibility in the presentation of alphanumeric display information in dot matrix format. [...] »
[theme : Software] [author : Gable] #OperatingSystem #HowItWorks #Algorithm
Extract : « Software systems are always subject to improvement and extension. The Eloquent Little Monitor is no exception. In the basic ELM monitor, described in my article in June BYTE, page 66, input and output to and from the terminal is handled in a fairly simplistic way. In the case of output, when a byte is ready to be printed, the terminal port is addressed and the byte is dumped onto the IO device. If the terminal is ready, it accepts the byte and prints it. If the terminal is not ready, for instance, if it has not finished printing the last byte, the processor idles, waiting for the terminal to be ready, before actually outputting the byte. [...] »
[theme : Hardware] [author : Liming] #Electronic
Extract : « Ever spend an hour or so entering software in your system, when suddenly the air conditioner or furnace kicks in, leaving your all too volatile memory looking like garbage? Power supplies are very important components to a small computer system; and careful consideration, before building or buying, will help make your system more reliable. [...] »
[theme : Hardware] [author : Kreitner] #Electronic #Listing #Assembly #Programming
Extract : « Most Altair owners tire of handloading the bootstrap loader for BASIC in a very short time, even though it is only 20 bytes. Here is a simple and very effective design for a 32 byte PROM board that holds the bootstraps for Altair Extended, 8 K, or 4 K BASIC (Version 3.2). [...] »
[theme : Software] [author : Baker] #Listing #BASIC #Game
Extract : « This computer game provides a realistic simulation of the actual stock market rather than a completely randomized happening of events. The program was written in BASIC for a DEC PDP-10 system so you may have to modify it slightly for your particular system. The game is programmed to allow one to four players with an option to play a game lasting from 3 to 1 years (rounds). [...] »
[theme : Mass Storage Devices] [author : Hill] #HowItWorks #Storage
Extract : « Why They Are Essential
What is the most important part of a computer system? Well, this is a difficult or impossible question to answer, but let us look at the components. Of course, there will have to be a processor, and this selection will affect the potential of the system; but a processor alone is just expensive junk. There will also have to be main memory; generally the more of it and the faster it is the better. [...] »
[theme : Software] [author : Nico] #HowItWorks #OperatingSystem
Extract : « Every time I get something new, I take it apart to see how it works and what I can change to make it work better for my use. My analyst says, "Don't worry! Boys are always taking clocks and radios and toasters apart." Well, that's a fine excuse for boys, but I'm pushing 32 H and still taking things apart ... so I worry! Once in a while though, I come up with what I think is a pretty good idea; like when I got my IMSAI computer running and started taking apart the software they sent with it. [...] »
[theme : Applications] [author : Yost] #Method #GameBoard
Extract : « A board game situation can be represented in binary code in a variety of ways. Often it will be found that the representation chosen has major consequences in the amount of memory used for program or for the situation memory that seems to be required for most game playing programs. [...] »
[theme : Survey] [author : Caulkins] #Association
Extract : « In May, June and July of 1976, a survey was made of hobbyist computer clubs. The intent was to collect data on club size and activities and to evaluate interest in an organization of clubs. I used a mailing list of 52 clubs, sending questionnaires to each; 22 (42.3%) were filled out and returned. During the survey the mailing list grew to 67. Just recently, through the courtesy of Jim Warren of Dr Dobb's Journal, I've learned of a club list of approximately 100 members. [...] »
#Book
Extract : « Computer Power and Human Reason: from Judgment to Calculation by Joseph Weizenbaum, W H Freeman and Co, San Francisco, 1976, 300 pp, $9.95. [...]
Advanced Placement Calculus: Exercises with Computer Programs by B Bates, K Jarvis and A Van Duyne, 174 pp, $5.50. [...]
Problem-Solving with the Computer by Edwin R Sage, 244 pp, $6.95. [...]
The ENTELEK Computer-Based Math Lab by Lawrence M Stolurow, 344 pp, 8-1/2 X 11, ISBN 87567-040-7, $24.95. [...]
Problems for Computer Solution by Gruenberger and J affray, 401 pp, $8.95. [...]
Problems for Computer Solution by Stephen Rogowski, Student's edition, 113 pp, $3.95; Teacher's edition, 279 pp, $9.95. [...]
The ENTELEK Computer-Based Physics Lab by Richard A Rader, 133 pp, 8-1/2 X 11, ISBN 87567-035-0, $14.95. [...]
Chemistry with a Computer by Paul Cauchon, 188 pp, 8-1/2 X 11, $9.95. [...] »
#Association
#Association
