[editor : Carl T. Helmers Jr.] [publisher : Virginia Londner] [art : Stephen Kruse, Wai Chiu Li, Dorothy Shamonsky, Ellen Shamonsky] #Magazine
#Abstract
This month's cover shows Babbage's 1822 difference engine, a device designed to calculate values in mathematical tables. Charles Babbage was one of the earlier pioneers in the field of computational machinery, whose work paved the way for later breakthroughs in computing.
One way to demonstrate your KIM-1 computer is to use it as a clock. Robert Baker's article KIMER : A KIM-1 Timer shows you how to display hours, minutes and seconds on the computer's LED display. The program can also be used as a timer. page 12
Heat sensitive aluminized paper is the key ingredient in Axiom's unusual EX800 printer. Find out about one user's reactions to this peripheral in The Axiom EX800 Printer: A User's Report by R J Bosen. page 28
Transforming the goal "I want thus and so function" into a program which performs that function is an act of design. Albert D Hearn provides the novice programmer with some background philosophy about design of personalized programs in his article entitled Modular Programming. page 32
Are you afraid of dynamic memories? Let author Lane T Hauck remove some of the mysteries about these devices in Who's Afraid Of Dynamic Memories? The greatest potential of the dynamic memory for the experimenter is its low price; reading the article should prove to be a "refreshing" experience. page 42
Dr James M Williams takes readers on a fascinating tour of early experiments in automata in his article Antique Mechanical Computers, Part 1: Early Automata. Read about Vaucanson's mechanical duck and the other miraculous pre-19th century devices that foreshadowed today's computers. page 48
Today more and more design engineers are introducing parallel processing into computer systems to improve through put rates. With the advent of inexpensive microprocessors, experimenters can now investigate this fascinating area. Find out more by reading Robert Loewer's The Z-80 in Parallel. page 60
When did personal computing really begin? Was it 1974 or 1971 ? The surprising answer is 1966. Sol Libes' The First Ten Years of Amateur Computing traces the growth of this rapidly growing field over the past decade, and gives credit to the true pioneers. page 64
The ability to control DC motors allows you to imagine applications from games to robotics. Robert L Walton describes a simple method of shaft position control in his article, Controlling DC Motors. page 72
Have you ever wondered how this business of computing ever got started? And just what were the major developments and discoveries that made the computer industry what it is today? Well, take A Short History of Computing course by reading the article by Keith S Reid-Green. It provides a perspective on the antecedents of today's developments in the field of computing. page 84
If you would like to turn your printer or other peripheral on and off from your computer keyboard, Steve Ciarcia describes a simple way to do it with an EROM in Ciarcia's Circuit Cellar: Build a Keyboard Function Decoder. page 98
How do I choose a microprocessor for personal computing? In some respects the problem is analogous to attempting to choose between a V-8 and a V-6 automobile engine of the same horsepower: both make the car go and most users couldn't care less about the type of engine so long as the car gets them to their desired destinations. Similar considerations apply in the choice of a personal computer product based on the microprocessor it contains. Who cares what microprocessor the product contains, so long as it accomplishes a certain minimum level of function with respect to systems and applications software? Lou Frenzel of the Heath Company gives some thoughts on How to Choose a Microprocessor in an article in this issue. page 124
Thinking of writing your own high level language interpreter for your home computer? If so, Ted Williams' and Steve Conley's article, A High Level Language for 8 Bit Machines, will supply you with an overview of one such implementation. The language that they develop is suitable for use as both an interpreter or a compiler. page 152
If you own a Tarbell cassette interface, read How to Get Your Tarbell Going. Author Larry Weinstein explains how the unit works and gives so me suggestions for improving performance. page 162
[author : Carl Helmers] #Edito
Extract : « In the June 1978 issue of BYTE, on pages 103 and 104, we printed a short report on activities of Ward Christensen and Randy Suess of the Chicago Area Computer Hobbyist Exchange (or CACHE). These two gentlemen have implemented a sort of public bulletin board in the form of a computer system which answers the phone through an auto answer modem, determines the data rate of the caller's modem, generates an interactive self-documenting conversation, and is able to store messages on a floppy disk. (For those who missed the original notice, the phone number to call is (312) 528-7141. You will need a Bell 103 style modem running in originate mode at 110 or 300 bps.
Another very active input is the continuing activity of the PCNET committee on the West Coast, which will sooner or later get around to defining a protocol appropriate to a number of users talking to each other. I also received considerable inspiration from a memo on Telemail put out by Ken Bowles of the University of California at San Diego. All these inputs add up to this present exploration of the state of modem technology as applied to the personal computer. [...] »
TABLE OF CONTENTS
[theme : Software] [author : Baker] #Listing #Assembly #Time
Extract : « This short program converts your KIM-l into a 24 hour digital clock and illustrates the use of the built-in timer for long time delays, and the use of instruction loops for shorter delays. The 7 segment displays are used for output, and are used in conjunction with one of the routines in the read only memory which drives them. [...] »
[theme : Product Description] [author : Bosen] #Review #Printer
Extract : « Some time ago I decided I needed a hard copy printer to make my computer system really useful, but as I looked over the possibilities on the market I concluded that every alternative was either too expensive, too slow, or too limited in capability for my needs (which included good legibility and lower case printing).
Just as I was about to abandon my plans, I saw a press release concerning a company called "Axiom" and a printer that appeared to solve all of my problems. It was advertised at $660, could print up to 160 characters per second (including upper and lower case letters) with an 80 column page width, and offered double and quadruple width characters as a bonus. I immediately wrote to Axiom and was surprised to receive a thick information packet within a week. [...] »
[theme : Hardware] [author : Loewer] #Electronic #Microprocessor #Book
Extract : « Many design engineers have introduced various types of parallel processing into systems in order to achieve higher throughput rates. Almost without exception though, these applications have been limited to medium and large scale computers due to price and complexity.
In the past two years, microprocessors have reached a level of sophistication which makes them candidates for parallel processing systems. Such systems could conceivably offer minicomputer performance at microcomputer cost. This article is an investigation of that idea. [...] »
[theme : Hardware] [author : Walton] #Electronic #Listing #Assembly #Interface
Extract : « This article wilt explain one inexpensive way to control the position of a small 1.5 V to 3 V hobby DC motor to within a quarter turn out of a total range of 16,384 turns. Various types of mechanical apparatus may be attached to this shaft for accurate positioning. The feedback portion of this circuit may be used alone for position sensing of shafts which reverse direction during operation. Modifications to obtain resolution better than a quarter turn and to drive higher powered DC motors will be discussed. [...] »
[theme : Hardware] [author : Ciarcia] #Electronic #Interface #Keyboard #Printer
Extract : « [...] The third and probably best approach is to use some of the unused functions on your keyboard to control peripherals remotely. There are a number of unprinted characters on a keyboard such as: end of transmission, end of text, or device control codes. By attaching an ASCII decoding circuit to monitor the line between the keyboard and the computer, these functions can be isolated and utilized as peripheral device control signals — more about this later. [...] »
[theme : Software] [author : Williams-Conley] #Algorithm #Programming #Book
Extract : « Interpreters such as BASIC or APL do not translate the high level source code into machine language. Rather, they scan the line of code and then perform a set of operations based upon the instruction and data stored in tables from previous instructions. Thus an interpreter saves the time consumed by translation, but no machine code is saved for later execution. The main advantage of an interpreter is the ease of error correction. The results of each line of code can be printed and the exact source of difficulty can be pinpointed. The price paid for this feature is memory. The source code, data, tables and the Interpreter program must all be resident in memory at the same time. [...] »
[theme : Hardware] [author : Weinstein] #Electronic #Interface #Storage #Listing #Assembly
Extract : « The function of the Tarbell cassette interface (referred to as the "Tarbell") is to enable a computer system to save the contents of memory on audio tape. The purpose of this article is to explain how the Tarbell interface works and to suggest some improvements to its design for readers who have had difficulties with the unit.
The Tarbell is intended for use with inexpensive cassette recorders: the inputs and outputs are matched for the typical Aux In, Ext Spkr and Earphone connections. The computer interface to the Tarbell is on a byte level, with the bytes and commands passed by 10 instructions on the Altair (S-100) bus. [...] »
[theme : Software] [author : Hearn] #Method
Extract : « If you have done some programming, you know that it's one of the most enjoyable and satisfying parts of personal computer use. The very thought that the vast power in the small system's processor is limited only by the program that you write for it is tremendously exciting.
If you are new to the computer game, the programs you have written up to now have probably been relatively small and uncomplicated, but you have developed a lot of experience and confidence from them. Most likely you haven't used any particular technique in designing and writing your programs: you have probably approached program design in an informal way and relied upon your good senses to guide you in this unfamiliar task. [...] »
[theme : Memory Design Tutorial] [author : Hauck] #Memory
Extract : « It is unfortunate that the dynamic memory has had a rocky start in the small systems world, but it is not really surprising. The dynamic programmable memory is a part generally avoided by most designers because it is not nearly as simple to use as static memory. But taking the extra trouble and design care can pay handsome cost and performance dividends, since the dynamic memory is inherently a lower cost part than its static counterpart (by present standards of technology). The purpose of this article is to remove some of the mystery about dynamic memory parts. [...] »
[theme : History] [author : Williams] #History
Extract : « My purpose in writing these articles is to remind computer enthusiasts that there is a high technology in every age, not just our own. Described herein are some of the stellar accomplishments of earlier times. The technology of electronics is merely the latest link in a continuous chain of technological developments spanning 20,000 years. Before that, there was a mechanical technology. [...] »
[theme : History] [author : Libes] #History
Extract : « 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. [...] »
[theme : History] [author : Reid-Green] #History
Extract : « A few weeks ago a master's degree candidate in computer science confided, with an embarrassed laugh, that he had never seen a computer. His experience with the machines of his chosen vocation had consisted entirely of submitting punched cards through a hole in a wall and later getting printed results the same way. While his opportunities to see equipment are restricted due to his student status, there are also thousands of working programmers and analysts using large scale equipment who have no contact with existing hardware and will never have a chance to see any first or second generation computers in operation. [...] »
[theme : Architecture] [author : Frenzel] #Microprocessor #Tips
Extract : « All personal and hobby computers are microprocessor based. That is, they use a single processor integrated circuit chip. One of the most important decisions you will ever make in purchasing a personal computer is choosing the type of microprocessor. The semiconductor manufacturers have provided computer designers with a wide range of microprocessing units having varying degrees of power and sophistication. As a result, there are at least a half dozen different processors available in hobby computers. This wide variety of products makes your choice somewhat flexible, or at least it seems that way. In reality, having so many processor styles to choose from, your decision becomes much tougher. If you are a beginner, it may be particularly difficult to make an intelligent choice. The purpose of this article is to provide you with some guidelines in making this important decision. The emphasis is on how to choose the best microprocessor for you when purchasing a personal computer. [...] »
#Association
#BASIC #Assembly #Book
Fooling with the Stack Pointer
More on Varistors
#Book
Extract : « Instant Freeze-Dried Computer Programming in BASIC by Jerald R Brown Dymax, POB 310, Menlo Park CA 94025 $6.95 [...] »