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n°5 january 1976

Foreground

p.26 LET THERE BE LIGHT PENS

[theme Hardware] [author Loomis]

p.32 LIFE Line 4

[theme Applications] [author Helmers]

p.46 GOLF HANDICAPPING

[theme Applications] [author Haller]

p.56 PHOTOGRAPHIC NOTES ON WIRE WRAPPING

[theme Techniques] [author Helmers]

Background

p.12 NEW MINI-MICROCOMPUTER SYSTEM

[theme Processors] [author Baker]

p.31 HORROR STORY

[theme Problems] [author Warren]

p.42 TOTAL KITCHEN INFORMATION SYSTEM

[theme Systems] [author Lau]

p.50 INTEL 8080 OP CODE TABLE

[theme Reference] [author Dittrich]

p.52 MORE TO BLINKING LIGHTS THAN MEETS THE EYE

[theme Applications] [author Helmers]

p.60 TAKING ADVANTAGE OF MEMORY ADDRESS SPACE

[theme System Design] [author Luscher]

p.64 K OR k ?

[theme System Style] [author Peshka]

p.92 THE CT-1024 KIT

[theme Review] [author Hogenson]

Nucleus

p.4 In This BYTE

p.9 Beach Ball Software

p.10 BOMB

p.67 For the Joules, It's a Steal

p.68 Clubs, Newsletters

p.73 MITS Computer Caravan

p.74 That Didn't Take Long at All

p.74 Classified Ads

p.77 BYTE's Bugs

p.77 Answers to December Word Hunt

p.80 Sphere Rolls Into Town

p.82 Letters

p.88 Book Reviews

p.96 The BYTE Questionnaire

p.96 Reader's Service

In This BYTE

On the cover, artist Robert Tinney has provided a scene depicting the combination of computers and golf handicapping described by Dr. George Haller in his article.

How would you like a PDP-ll/40 in your basement computer room? The price would probably be too high for the typical amateur. But Digital Equipment Corporation also makes the LSI-ll, a microcomputer which implements the PDP-ll/40 instruction set and inherits a wealth of existing PDP-ll software. Turn to Bob Baker's article on the LSI-ll for a summary.

How do you draw a picture on an oscilloscope display? Add a Light Pen as described by Sumner Loomis, and you will be able to add and delete points of light.

When the LIFE program can't figure out a key code, it calls DEFAULT, as described in LIFE Line 3. This issue's LIFE Line 4 specifies the DEFAULT routine used to enter cursor motion control data and numeric data for the KEYBOARD INTERPRETER. As a combined hardware and software system, the LIFE application enters the realm of hardware for the first time with a simple circuit to interface the cursor motion control keyboard and an ASCII keyboard via the same input port.

Wire wrapping is a technique often used to assemble circuits. Turn to Photographic Notes on Wire Wrapping for some pointers for your own custom computer interfaces .

According to tradition, no computer is ever complete without blinking lights. But There's More to Blinking Lights Than Meets the Eye, or the control panel designer's utilitarian motives. This issue provides a few ideas for using simple and inexpensive LED indicators in ways far removed from the traditional control panel application.

In the October BYTE, Richard Gardner commented on the application of personal computers in household situations. In this issue, Ted Lau continues on that theme with an article of "structured speculation" on the Total Kitchen Information System (TKIS).

Computers solve problems, right? One problem which golfers have is calculating handicaps so that duffers can play against pros in the same tournament. In Golf Handicapping (or: Buy a New Peripheral with Money Earned from Your Local Duffers), Dr. George Haller describes a program he concocted to serve as the bas is for a part time business calculating golf handicaps at his country club. For readers with teenage children, this might make a great opportunity for the kids to make some money to help pay for college expenses while learning how to run a business.

Computer systems have many resources which can be used by the person who assembles or modifies the design . One resource which is very important is the memory address space inherent in the design of the computer. Taking Advantage of Memory Address Spaces by James Luscher can provide important improvements in speed and function of your system.

What is style? In his article K or k?, Manfred Peshka describes some notational conventions which apply to BYTE's unique combination of hardware and software information. While the change of these standards is incomplete in this issue, future BYTEs will employ the standard abbreviations and units throughout.

What is one of the most useful peripherals? Why , the television set of course. To use the TV you need an interface. One such interface is the CT-l024 product by SWTPC reviewed by Jim Hogenson.

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n°6 february 1976

Foreground

p.16 KEYBOARD MODIFICATION

[theme Surplus] [author Macomber]

p.54 LEDs LIGHT UP YOUR LOGIC

[theme Techniques] [author Gray]

p.58 BUILD A TTL PULSE CATCHER

[theme Test Equipment] [author Walde]

p.60 DRESSING UP FRONT PANELS

[theme Techniques] [author Walters]

Background

p.18 MY DEAR AUNT SALLY

[theme Algorithms] [author Grappel]

p.26 PROCESSING ALGEBRAIC EXPRESSIONS

[theme Algorithms] [author Maurer]

p.32 DATA PATHS

[theme Hardware] [author Liming]

p.42 THE NEW ALTAIR 680

[theme New Product] [author Vice]

p.46 HOW TO SAVE THE BYTES

[theme Man-Machine Interface] [author McIntire]

p.50 MORE ON THE SWTPC 6800 SYSTEM

[theme New Product] [author Kay]

p.62 TV COLOR GRAPHICS

[theme Hardware] [author Lancaster]

p.76 COULD A COMPUTER TAKE OVER?

[theme Speculation] [author Rush]

Nucleus

p.2 In This BYTE

p.4 Join the Club

p.10 Letters

p.14 Our New Offices

p.31, 83 BYTE's Bits

p.41 Chips Found Floating Down Silicon Slough

p.61 Classified Ads

p.69 Numbers

p.70 Clubs, Newsletters

p.72 Audio Cassette Standards Symposium

p.74 View From Silicon Valley

p.84 8080 Op Code Table

p.92 Book Reviews

p.95 BOMB

p.96 The BYTE Questionnaire

p.96 Reader's Service

In This BYTE

How does a computer evaluate a complicated mathematical expression? There are many ways to accomplish this function. One technique is to use the My Dear Aunt Sally Algorithm which is described by Robert Grappel.

There is more than one way to Process Algebraic Expressions, of course. In his article on the subject, W.D. Maurer describes the Bauer-Samelson algorithm, which uses an operator stack and an operand stack to parse algebraic expressions.

How do bits get from one place to another? The design of Data Paths to convey information is an important consideration in any system. Gary Liming provides some background information on the subject.

MITS makes a 6800 product, too. James B. Vice of MITS describes his company's design in an article on The New Altair 680.

Hard copy can be created in many ways. Its purpose is to record information in a form which humans can interpret unaided. In How to Save the Bytes, Thomas Mcintire proposes a multiple-segment character set which might be useful for an inexpensive print mechanism.

Gary Kay continues a presentation of information on the Southwest Technical Products Corporation's 6800 system which was begun in BYTE No.4. This month's installment presents information about the memory boards, serial interface, control interface, parallel interface, power supply and case. The information is completed with a short discussion of available software and future additions to the system.

BYTE has published a few examples of LEDs used in test probes and diagnostic equipment. In his article E. W. Gray provides some basic information on the use of LEDs. After incorporating his suggestions you can have LEDs Light Up Your Logic in more ways than one.

One way to monitor digital data lines is simply to drive an LED based upon the steady state of the line. But what if you are dealing with occasional pulses? A simple indicator is the TTL Pulse Catcher described by Bill Walde, a test instrument which can be built from one IC, one LED, two switches and two resistors.

How do you generate graphics patterns for TV raster scanning? One answer is provided by Don Lancaster's discussion of Color Graphics Techniques.

Could a Computer Take Over? Ed Rush provides us with some thoughts on the subject with ample references to the speculative fiction of computer technology. We'll let readers draw their own conclusions.

Getting Information from Joysticks and Slide Pots is a problem which must be solved for interactive game purposes. One solution to the problem is shown in this issue.

And on the cover, artist Robert Tinney shows My Dear Aunt Sally at work tutoring a computer on the subject of interpreting arithmetic expressions.

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n°7 march 1976

Foreground

p.10 THE COMPLEAT TAPE CASSETTE INTERFACE

[theme Systems] [author Hemenway]

p.30 BUILD THE BIT BOFFER

[theme Hardware] [author Lancaster]

p.40 DIGITAL DATA ON CASSETTE RECORDERS

[theme Hardware] [author Mauch]

p.52 ASSEMBLING PROGRAMS BY HAND

[theme Software] [author Helmers]

p.79 POT POSITION DIGITIZING IDEA

[theme Hardware] [author Schulein]

Background

p.18 MAGNETIC RECORDING FOR COMPUTERS

[theme Hardware] [author Manly]

p.46 MICROPROCESSOR UPDATE : CP1600

[theme Hardware] [author Baker]

p.62 PROCESSING ALGEBRAIC EXPRESSIONS, PART 2

[theme Software] [author Maurer]

p.78 WHAT'S IN A VIDEO DISPLAY TERMINAL

[theme Systems] [author Walters]

Nucleus

p.2 In This BYTE

p.6 Magnetic Recording Technology

p.29 Technology Update

p.68 Letters

p.74 Clubs, Newsletters

p.77 Space Ace, Numbers Answer

p.71, 80, 82, 84, 88 What's New

p.86, 90 BYTE's Bits

p.86 Classified Ads

p.88 BYTE's Bugs

p.92 Book Reviews

p.96 BOMB

p.96 Reader's Service

In this BYTE

One result of the BYTE Audio Cassette Symposium last November was a provisional standard for audio recording, essentially identical to that described by Don Lancaster in issue No. 1 of BYTE last September. In this issue, Don presents an updated design and describes how to Build The Bit Boffer. Then, to show that there's more than one way to spin a tape, Harold Mauch gives some details of a second system compatible with the standard in his article Digital Data on Cassette Recorders.

Jack Hemenway uses Don Lancaster's Bit Boffer desi gn to wire up The COMPLEAT Tape Cassette Interface using an ACIA attached to his 6800. But completeness requires more than hardware, so Jack provides software of six subroutines for the control and transfer of data with this interface.

Creating programs can be done with a variety of tools. The best way is to use an interactive terminal with "mass storage available and a good high level language. But, when you move up country or have other reasons to be away from convenient access to monster machines, at first things have to be done the hard way using a new home brew machine. This makes the techniques of Assembling Programs by Hand invaluable for your bag of tricks.

In the previous issue, information on joysticks and slide pots was presented. In this issue, John Schulein supplies a short note on another Pot Position Digitizing Idea.

It is one thing to tell how to do something, but why it works is often a separate topic. William A Manly provides answers to a lot of the "whys" of magnetic mass storage in h is article on the physics of Magnetic Recording for Computers.

One of the newer microprocessor designs is the General Instrument CP1600. In his Microprocessor Update, Bob Baker summarizes the technical information about this chip design.

Last month, Prof W Douglas Maurer described some salient points about processing algebraic expressions. In this issue, he continues the discussion with Part 2 of Processing Algebraic Expressions. This includes a simplified explanation of what it means to generate code as in a compiler.

Peek inside a video display terminal with Don Walters' quick summary of What's in a Video Display Terminal.

And to round out the theme of magnetic recording technology, the cover shows a typical Philips style audio cartridge.

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n°8 april 1976

Foreground

p.20 BIORHYTHM FOR COMPUTERS

[theme Application] [author Fox-Fox]

p.28 HOW TO BUILD A MEMORY WITH ONE LAYER PRINTED CIRCUITS

[theme Hardware] [author Lancaster]

p.34 AARGH! (or, HOW TO AUTOMATE PROM BURNING WITHOUT EML)

[theme Hardware] [author P Helmers]

p.42 CONTROLLING EXTERNAL DEVICES WITH HOBBYIST COMPUTERS

[theme Hardware] [author Bosen]

p.46 INTERFACE AN ASCII KEYBOARD TO A 60 mA TTY LOOP

[theme Hardware] [author Cotton]

p.56 DESIGN AN ON LINE DEBUGGER

[theme Software] [author Wier-Brown]

p.79 IO STROBES FOR THE ALTAIR 8800

[theme Hardware] [author Schulein]

p.80 SAVE MONEY USING MINI WIRE WRAP

[theme Hardware] [author Thompson]

Background

p.16 PROGRAMMING THE IMPLEMENTATION

[theme Software] [author Crayne]

p.24 THE MAGIC OF COMPUTER LANGUAGES

[theme Software] [author Nelson]

p.36 THE SR-52: ANOTHER WORLD'S SMALLEST

[theme Systems] [author Flippin]

p.50 FRANKENSTEIN EMULATION

[theme Speculations] [author Murray]

p.64 MICROPROCESSOR UPDATE: TEXAS INSTRUMENTS TMS9900

[theme Hardware] [author Baker]

Nucleus

p.2 In This BYTE

p.4 Customization-The Expression of Individuality

p.6 Letters

p.12 Space Ace Revisited

p.14, 18, 78 What's New

p.32, 77, 84 BYTE's Bits

p.55 Technology Update

p.74 BYTE's Bugs

p.74 Classified Ads

p.76 Book Review

p.90 Clubs, Newsletters

p.96 BOMB

p.96 Reader's Service

In this BYTE

Curiosity, experimentation and imagination are great aids to the user of a computer system. Charles A Crayne describes two in struction set variations he found while Programming the Implementation of an 8008 processor as a SCELBI 8H minicomputer.

Can a computer predict your state of mind? A better question would be: Is there a theory which can be computationally verified to predict your state of mind? Biorhythm for Computers is an article by Joy and Richard Fox on the use of a BASIC calculation to provide predictions based upon the pseudo science of a simple biorhythm hypothesis.

A key element of computing is the expression of ideas in the form of programs and algorithms. It takes the Magic of Languages to make such expressions in a form the computer can understand . Turn to Theodor Nelson's article for an introduction to some basic concepts of computer languages.

Ho hum, another memory article? Not quite. When Don Lancaster adds a twist of ingenuity, you find out How to Build a Memory With One Layer Printed Circuits, saving the trouble of using many wire jumpers or figuring out how to make double layer boards in the kitchen PC laboratory.

Aargh! (or, How to Automate PROM Burning Without EML) was Peter Helmers' reaction to a suggestion that relays be used to control a circuit. Study his figures for technical information and learn about the exciting new field of EML [sic] logic in the accompanying text.

It could not take long to find another contender in the marketplace for compact computer systems. In this issue, J Bradley Flippin discusses The SR-52: Another "World's Smallest Computer System."

Input is often done with a switch contact when simple on off states of electrom echanical systems are considered. But suppose you want to program stage lighting or drive a keyboard machine with so lenoids. Then you'll need information on Controlling External Devices with Hobbyist Computers. Robert J Bosen presents some ideas on the subject.

Computers require a large dose of that arcane ar t, interfacing. Jay A Cotton shows one example of that art in his discussion of how to Interface an ASCII Keyboard to a 60 mA TTY Loop.

Introspection is a prime technique for analyzing the human consciousness. Many parallels can be drawn between the design of camplicated computer networks and knowledge of human mental functions. While not purporting to be a complete or final model of human mental functions, Joe Murray's article on Frankenstein Emulation provides some good inputs on the ultimate hobby: modeling human behavior.

Minicomputers and microcomputers are really quite similar. The former are simply faster and more expensive than the current versions of the latter. Thus when you Design an On Line Debugger for a minicomputer, as Robert Wier and James Brown have done, the same general interactive design can be used as the control panel interface for any microcomputer as well. Add an on line debugger to your computer and you'll make it a much easier device to use.

What's better than an 8 bit processor in a 40 pin package? Why, a 16 bit processor in a 64 pin package, of course. In his Microprocessor Update: Texas Instruments TMS9900, Robert Baker provides readers with an overview of this exciting new computer which is sure to find its way into personal computing systems over the next year or so.

Ingenuity is an old American tradition. Roger W Thompson makes his contribution to that tradition in his description of how to Save Money Using Mini Wire Wrap, a socketless penny pinching way of wiring integrated circuit projects.

On the cover, at the suggestion of Tully Peschke, Robert Tinney created a fantasy on a theme of BYTE. First aid has already been applied and it is expected that the banner will be fixed in time for the May issue.

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n°9 may 1976

Foreground

p.28 MORE INFORMATION ON PROMs

[theme Hardware] [author Smith]

p.36 SERIALIZE THE BITS FROM YOUR MYSTERY KEYBOARD

[theme Hardware] [author Haller]

p.38 AN OCTAL FRONT PANEL

[theme Hardware] [author DeMonstoy]

p.42 SHOOTING STARS

[theme Applications] [author Nico]

p.50 BUILD A SERIAL ASCII WORD GENERATOR

[theme Hardware] [author Finger]

p.70 MICROPROCESSOR BASED ANALOG/DIGITAL CONVERSION

[theme Interface Techniques] [author Frank]

Background

p.8 A DATE WITH KIM

[theme New Product] [author Simpson]

p.18 N SOURCE

[theme Systems] [author Boudinot]

p.24 ROMs IN MICROCOMPUTER MEMORY ADDRESS SPACE

[theme Systems] [author Eichbauer]

p.60 "CHIP" OFF THE OLDE PDP-8/E: THE INTERSIL IM6100

[theme Hardware] [author Nelson]

p.74 SIMPLIFY YOUR HOMEMADE ASSEMBLER

[theme Software] [author Jewell]

Nucleus

2 In This BYTE

4 Trends in Applications

14 Letters

35 Classified Ads

41, 58 What's New?

54 Clubs and Newsletters

56 BYTE's Bugs

84 Puzzle Time, Space Ace Answer

88 Book Review

96 BOMB

96 Reader's Service

In this BYTE

Richard Simpson descr ibes his first Date With KIM, the new product from MOS Technology which comes assembled and ready to use. This product, wh ich is the basis of his system, marks the first direct entry of a semiconductor manufacturer into the personal systems field .

Are different microcomputers equivalent? In n Source, RD Boudinot presents some excellent background information on multiple sources of components and systems, the mixing of products from different manufacturers and methods of evaluating products for use in a personal computing system.

Of what use is a nice friendly permanent memory? Dale Eichbauer contributes some ideas on the use of Read Only Memories in Microcomputer Memory Address Space.

Previous articles have covered programming and uses of some of the simpler fusible link read only memories. But how about erasable ROMs? Roger L Smith provides some More Information on PROMs including a method of programming the widely available 1702 parts.

One way to get a hard copy terminal is to use a receive only Teletype unit. Using an inexpensive ASCII keyboard and a UART circuit, Dr George Haller shows how to Serialize the Bits From Your Mystery Keyboard and achieve the same function as a keyboard send receive Teletype for·about half the cost.

Dissatisfied with toggle switches? Usc An Octal Front Panel similar to Hemran DeMonstoy's design to replace toggle switches with an octal keyboard.

You'll be SHOOTING STARS in a fascinating logical game when you implement a version of Will ard Nico's program on your computer. On the cover is artist Robert Tinney's impression of a SHOOTING STARS addict.

A simple signal generator might suffice for a radio man, but testing of computers and data communications hardware can require more sophisticated equipment. One such item is a Serial ASCII Word Generator such as the design Ronald Finger·describes.

How do you take advantage of a decade of software experience? One way is to emulate anothcr computer's architecture as Intersil has done with its IM6100. Robert Nelson describes a "Chip" Off the Olde PDP-8E in this first part of a two part article.

Can a computcr measure voltages with out hundreds of dollars worth of hardware? Of course it can. The secret is to use Microprocessor Based Analog/Digital Conversion Techniques of the sort described in Roger Frank's article on a very basic interface.

One of the keys to creating an assembler is defining exactly what the input source language will look like. An appropriate choice which simplifies writing the assembler will greatly speed up the process of implementing the program. In his article on the subject, Gregory Jewell shows how to Simplify Your Homemade Assembler using techniques which are applicable to most microcomputers.

1976/byte_1976_06.jpg 1976/byte_1976_06_index.jpg

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n°10 june 1976

Foreground

p.16 BUILD A TELEVISION DISPLAY

[theme Hardware] [author Gantt]

p.40 BUILDING AN M6800 MICROCOMPUTER

[theme Hardware] [author Abbott]

p.48 STRIKE A MATCH

[theme Applications Software] [author Hansford]

p.66 INTERACT WITH AN ELM

[theme Software] [author Gable]

Background

p.8 A SMALL BUSINESS ACCOUNTING SYSTEM

[theme Applications] [author Lehman]

p.22 PROGRAMMING FOR THE BEGINNER

[theme Software] [author Herman]

p.28 A HIGH SCHOOL COMPUTER SYSTEM

[theme Review] [author Lett]

p.32 SYSTEMS APPROACH TO A PERSONAL MICROPROCESSOR

[theme System Design] [author Suding]

p.58 "CHIP" OFF THE OLDE PDP 8/E-PART 2

[theme Hardware] [author Nelson]

p.76 AN INTRODUCTION TO ADDRESSING METHODS

[theme Hardware] [author Zarrella]

p.82 SCELBAL

[theme Product Description] [author Wadsworth-Arnold]

Nucleus

p.2 In This BYTE

p.4 Toward a Parallel Interface Standard

p.5 Call for Papers

p.6 About the Cover

p.14, 73, 81, 95, 96, 98, 100, 110 What's New?

p.36 The Albuquerque Happenings

p.52 Letters

p.64 Components and Parts (Puzzle)

p.87 Classified Ads

p.88 Book Reviews

p.90 Clubs, Newsletters

p.94 Programming Quickies

p.104 Software Bug of the Month

p.104 BYTE's Bugs

p.106 Systems of Note

p.112 BOMB

p.112 Reader's Service

In this BYTE

What does it take to make your microcomputer keep track of that small spare time "moonl igh tn business? For small businesses, one of the biggest problems is all the paperwork required of the entrepeneur. John A Lehman provides an introduction to the subject of automated accounting procedures in his description of A Small Business Accounting System.

Find out how to Build a Television Display which can be interfaced to your computer's memory address space by consulting C W Gantt Jr's article on a 15 IC controller for a 32 by 16 display.

Programming to a large extent is organizing your ideas about what the computer should do. Ronald T Herman gives some basic pointers on Programming for the Beginner, concerning the practice of structuring program designs into well defined verbal descriptions, before you generate a single line of code. This practice makes programming easier and less subject to nasty errors which interfere with the goal of a working application.

Is your high school's computing budget crimped ? Use Christopher Lett's experience with A High School Computing System as a way to show that a small budget does not necessarily rule out getting a system.

A Systems Approach to a Personal Microprocessor is the inaugural article in a new series of detailed design articles which is being prepared for BYTE by Dr Robert Suding. In this first instalment, you'll find some of Dr Suding's views on the philosophy of system design, to lay the groundwork.

Build a computer? Sure. Bob Abbott shows you the circuitry and some photos of a wire wrapped M6800 system in his article on Building an M6800 Microcomputer.

One of the principal uses of a computer is data processing. Phillip L Hansford describes one simple data processing application which he implemented with minimal equipment: How to Strike a MATCH between penpals for his penpal club.

Last month, Bob Nelson introduced "Chip" Off the Olde PDP 8/E. In Part 2, he discusses the interrupt structure, control panel features and support chips of the Intersil IM6100 design.

One key component of system software for any computer is a monitor program. You can find out how to program and Interact with an ELM (Eloquent Little Monitor) by reading G H Gable's article on his design of a handy piece of system software.

Techniques of developing the effective address for operands in memory vary with the choice of CPU. In An Introduction to Addressing Methods. John Zarrella discusses some of the classical ways computers use to calculate the address of operands in memory. You can use this background information in forming your own opinion about the instruction sets of the various miCrocomputers presently available.

What's in a language 7 Nat Wadsworth and Mark Arnold present some information on their interpretive language system, SCELBAL, in a product description article.

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n°11 july 1976

Foreground

p.6 COINCIDENT CURRENT FERRITE CORE MEMORIES

[theme Recycling] [author Jones]

p.22 EXPLORE AN 8080 WITH EDUCATOR-8080

[theme Software] [author Howerton]

p.38 THE "IGNORANCE IS BLISS" TV DRIVE CIRCUIT

[theme Hardware] [author Barbier]

p.46 WHY WAIT? BUILD A FAST CASSETTE INTERFACE

[theme Hardware] [author Suding]

Background

p.18 ASSEMBLING A SPHERE

[theme Review] [author Anderson]

p.30 MACHINE LANGUAGE PROGRAMMING FOR THE "8008"-Chapter 1

[theme Software] [author Wadsworth]

p.40 PUT THE "DO EVERYTHING" CHIP IN YOUR NEXT DESIGN

[theme Hardware] [author Baker]

p.54 SURPLUS ELECTRONICS IN TOKYO AND MANILA

[theme Travelogue] [author Hayes]

p.58 MAKE YOUR OWN PRINTED CIRCUITS

[theme Hardware] [author Hogenson]

p.64 A PLOT IS INCOMPLETE WITHOUT CHARACTERS

[theme Software] [author Lerseth]

Nucleus

p.2 In This BYTE

p.4 The Trend Toward Hassle Free Products

p.39 Tool Box

p.44, 79 BYTE's Bits

p.74 Good Grief!

p.76, 102 What's New?

p.81 Software Bug of the Month 2

p.83 What Happened at Trenton

p.86 Clubs, Newsletters

p.90 Letters

p.95 Ask BYTE

p.96 Reader's Service

p.98 Classified Ads

p.100 BYTE's Bugs

p.104 Book Reviews

p.112 BOMB

In this BYTE

Have you ever looked through the surplus catalogs and wondered whether those memory core planes and stacks advertised could be used for anything other than tea strainers? For theory and practical information on Coincident Current Ferrite Core Memories turn to James R Jones' article.

Bruce A Anderson describes his experiences Assembling a Sphere in his review of what rolled out of the production facilities in Bountiful UT last fall.

One of the most important questions people ask is "how do I learn about what a computer does? " One way to help out friends who are trying to get into the swing of things with programming is to implement a version of Charles Howerton's Educator-8080 program so that they can interactively Explore an 8080 with Educator-8080.

A thorough explanation of the instruction set should accompany any product intended for wide distribution. An example of such an explanation is provided by Nat Wadsworth's Machine Language Programming for the "8008" and Similar Microcomputers, a manual which is sold by Scelbi Computer Consulting Inc. In this issue is the first of three direct reprints from that manual: Chapter 1 which describes the 8008 instruction set.

One of the problems of interfacing unknown electronics is figuring out how to accomplish the match. Ken Barbier built a character generator, went out and bought a TV set, then faced the problem of building a driver for the TV. The result was The "Ignorance is Bliss" Television Drive Circuit.

While not really promising the entire big blue sky, when you Put the "Do Everything" Chip in your Next Design you'll end up with a computer that has five separate programmable real time clocks, standard serial communications data rates from 110 baud to 9600 baud, automatic generation of an 8080's RST n interrupt vectors, an 8 bit parallel output and an 8 bit parallel input port. Turn to Robert Baker's latest article to find out about this nifty chip.

Robert Suding asks "Why Wait?" in a rhetorical fashion, and proceeds to demonstrate his schematic of a fast cassette interface which uses software and a one bit 10 port to implement an audio cassette system.

What's it like to be isolated from bountiful US surplus markets? In a sense, it means a relative isolation from modern LSI products, as Dr Michael N Hayes reports on his experiences in Tokyo and Manila in December 1975. Read his report on Surplus Electronics in Tokyo and Manila in this issue.

There are many ways to wire a circuit. The most common manufacturing method is printed wiring. But you can also Make Your Own Printed Circuits at home, using techniques described by James Hogenson in his article.

One of the most interesting applications of computers is in the area of graphic outputs. Using a vector CRT or a plotter, drawing pictures of mathematically generated abstractions or simple cartoons can be the beginning of hours of fun. But A Plot Is Incomplete Without Characters so Richard J Lerseth concocted some software described in his article on the generation of an ASCII character set (or special characters) for a plotter or vector display device.

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n°12 august 1976

Foreground

p.44 TRUE CONFESSIONS: HOW I RELATE TO KIM

[theme Hardware] [author Gupta]

p.66 BUILD A TV READOUT DEVICE FOR YOUR MICROPROCESSOR

[theme Hardware] [author Suding]

p.96 INTERFACING THE 60 mA CURRENT LOOP

[theme Hardware] [author King]

Background

p.6 WHAT DO YOU DO WITH A VIDEO DISK?

[theme Speculation] [author Buchanan]

p.16 FRIENDS, HUMANS, COUNTRYROBOTS: LEND ME YOUR EARS

[theme Hardware] [author Rice]

p.26 THE TIME HAS COME TO TALK

[theme Voice Systems] [author Atmar]

p.34 MICROPROCESSOR UPDATE: ZILOG Z80

[theme Hardware] [author Hashizume]

p.40 MACHINE LANGUAGE PROGRAMMING FOR THE "8008"-Chapter 2

[theme Software] [author Wadsworth]

p.52 JACK AND THE MACHINE TALK (or, The Making of an Assembler)

[theme Software] [author Grappel-Hemenway]

p.84 WHAT'S AN I2L (I squared L)?

[theme Hardware] [author Steeden]

Nucleus

p.2 In This BYTE

p.4 Some Notes on Clubs

p.12 Letters

p.50, 78, 83, 86, 90, 98, 105, 122 What's New?

p.74 Book Review

p.76 BYTE's Bugs

p.77 Classified Ads

p.81 Software Bug of the Month 3

p.88 Systems of Note

p.95 Functional Specifications

p.100 Clubs, Newsletters

p.126 Tool Box Answers

p.128 BOMB

p.128 Reader's Service

In this BYTE

What's good for about four billion bytes on line capacity, 10 to 50 ms access time, and a system cost in the personal computing category? Find out by reading Martin Buchanan's article on What Do You Do With a Video Disk?

"Friends, Humans, and Countryrobots. Lend Me Your Ears." When you've reached a point in your audio output micro-experimentation where the computer can talk, you'll have quite an accomplishment. D Lloyd Rice describes some of the background information needed to create a human vocal tract model with computer control in his excellent tutorial on the subject. Imagine, Star Trek implemented with a real ship's computer output!

What plugs into one Altair or IMSAI compatible bus slot, eats serial phoneme snacks, talks back and won't shut up till you pull the plug? Find out by reading Wirt Atmar's historical background and description of a new Altair compatible plug-in voice synthesizer, a commercial version of the prototype which was demonstrated as a prize winning entry in the recent MITS World Altair Computer Convention. Once you get the hang of its accent, your talking computer will add a new dimension to conversational software.

What's wrong with the 8080 processor architecture? Ask a programmer for "features" and you'll get some answers. An analysis followed by definition of improvements resulted in the new Zilog Z80 microprocessor which is the ultimate in 8 bit microprocessors at this point in time. Find out what the Z80 is all about by reading Burt Hashizume's Microprocessor Update: Zilog Z80.

The act of programming, like any act of creation, requires a bit of organization and discipline on the part of the thinker. In the second reprint from Nat Wadsworth's Machine Language Programming for the "8008" (and similar microcomputers) you'll find some thoughts on the design and planning of programs.

In May BYTE, we had A Date With KIM. Here is the next chapter in the continuing story of True Confessions: How I Relate to KIM. Turn to Yogesh M Gupta's account of modifications to the KIM-1 system which achieve compatibility with slower memories, bus expansion, and a priority interrupt capability.

A sub theme of this BYTE is the idea of the talking personal computer system. Well, Jack Hemenway and Robert Grappel got together recently to concoct an allegorical tale of Jack's assembler. In Jack and the Machine Talk you'll see a dialogue with a computer personified. Which leads to the next step: Who'll be the first reader to create a program to implement the computer side of the dialogue, using one of the new voice output devices which are coming to market?

Want to experiment with high level languages (like APL) that require an extended character set? Want to simply build and utilize a convenient text display output device? Need upper and lower case displays for a text editor? If so, and if you can get by with a 32 character line on a standard TV set or monitor, then Dr Robert Suding's latest article will be of interest. Build a TV Readout Device for Your Microprocessor using his detailed design.

What's an I2L? Terry Steed en has written a short background summary of this relatively new logic family, one which has important manufacturing and power consumption advantages which assure its place in the stable of semiconductor fabrication methods.

Many readers have found real bargains in older Baudot Teletype machines such as the Model 15 and the Model 19. The main problem, though, is Interfacing the 60 mA Current Loop to the normal TTL level signals of a typical microcomputer. One solution to this problem is provided by Walter S King's short article in this issue.

And for the cover, Robert Tinney portrays a scene from the near future.

1976/byte_1976_09.jpg 1976/byte_1976_09_index.jpg

Lire la revue / Get this issue (archive.org)

n°13 september 1976

Foreground

p.26 BUILD THIS MATHEMATICAL FUNCTION UNIT-Part 1

[theme Hardware] [author Guthrie]

p.36 RANDOMIZE YOUR PROGRAMMING

[theme Software] [author Grappel]

p.40 A BASIC STAR TREK TRAINER

[theme Software] [author Herd]

p.50 HOW TO DO A NUMBER OF CONVERSIONS

[theme Software] [author Brown]

p.62 THE CIRCUIT FOR Z-80s

[theme Hardware] [author Suding]

p.104 A FLAMELESS IC RECYCLING TRICK

[theme Techniques] [author Bondy-Droms]

p.108 AMSAT 8080 STANDARD DEBUG MONITOR: AMS80 VERSION 2

[theme Systems Software] [author Allen-Kasser]

Background

p.16 ARE YOU AN AUTHOR?

[theme Software] [author Mooers]

p.44 THE MSC 8080+ MICROPROCESSOR AS A PERSONAL SYSTEM

[theme Product Description] [author Barbier]

p.76 MICROPROCESSOR UPDATE: SC/MP FILLS A GAP

[theme Hardware] [author Baker]

p.84 MACHINE LANGUAGE PROGRAMMING FOR THE "8008"-Chapter 3

[theme Software] [author Wadsworth]

Nucleus

p.4 In This BYTE

p.6 Come One, Come All!

p.12 Letters

p.61 Software Bug of the Month 4

p.73 BYTE's Bits

p.74, 81, 96 What's New?

p.92 Classified Ads

p.98 Clubs, Newsletters

p.124 Programming Quickies

p.128 BOMB

p.128 Reader's Service

In this BYTE

About the Cover

BYTE began with its first issue dated September 1975. Since that time, a 96 page magazine has grown into a 128 page monthly compendium of information with a reputation of which we're quite naturally proud. That first issue was assembled from scratch in seven weeks of hectic activity starting May 25 1975. At that time, we had no real estimate of the way in which you, our readers, would respond. The goal was simply to put out the best product possible given the constraints and problems of a new enterprise. Since that time, much has changed as the people who bring you this magazine have all grown and improved with experience. The principles upon which BYTE is based, technical excellence combined with a sense of humor and a spirit of fun, have not changed. As a celebration of that combination, we commissioned Robert Tinney to implement a fanciful picture of the BYTE 0.01 Centennial Celebration. With this very personal anniversary, we look forward to the developments and improvements of the coming year. In BNF notation, <we::= <We> <the contents of the BYTE staff listing, page 5>

Whatever your stand on the questions of free exchange of software, one thing is certain : To write software of any form is an act of creation. The decision as to what is done with. a work of software should reside with the creator. If you are a writer of software, find out about some of the legal aspects of your work by reading Calvin N Mooers' Are You an Author?

A multiprocessor system is a combination of two or more processors to accomplish more than what a single processor could do by itself. In his article Build This Mathematical Function Unit, author R Scott Guthrie describes a simple form of the multiprocessor concept: a scientific calculator unit controlled by an 8 bit microprocessor. The calculator comes preprogrammed with all the software you need to carry out floating point arithmetic operations and special functions, to say nothing of an arithmetic expression parser implicit in the parenthesis keys. The calculator peripheral in one fell swoop elimimites a lot of the software development required for an interpretive mathematically oriented computer language.

Learn how to Randomize Your Programming by reading Robert Grappel's discussion of pseudorandom number sequences along with practical software to implement 8 or 16 bit generators.

Well, here it is: the first version of Star Trek to be printed in full in BYTE. Gerald H Herd describes his version of A BASIC Star Trek Trainer as implemented on a Data General NOVA, but easily adaptable to any BASIC machine with about 5 K bytes of text area.

One of the choices open to readers familiar with the industrial OEM markets is to purchase computer products intended for systems engineering situations. In his product description article on The MSC 8080+ Microcomputer as a Personal System, BYTE reader Ken Barbier enthusiastically describes one such product and his experiences using it.

Binary, octal, hexadecimal or decimal? That is the question. Whatever your preference, however, James Brown will help you out with his article on How to do a Number of Conversions. By implementing the whole set of conversions, you can try each base on for size, depending upon your mood and idiosyncracies.

Last month, Burt Hashizume described the neat new architecture of the "super 8080" called Z-80 by its maker, Zilog Inc. In this issue, Dr Robert Suding brings the excitement down to earth with the complete details of The Circuit for Z-80s, a complete central processor with some programmable memory and a dash of systems software in an erasable ROM thrown in for good measure.

What's an SC/MP? Find out by reviewing Robert Baker's Microprocessor Update: SC/MP Fills a Gap.

In the final instalment of our series of three reprints from Nat Wadsworth's Machine Language Programming for the "8008" (and Similar Microcomputers), you'll find some information on the details of machine language programming in computers with limited resources.

Recycling pretested integrated circuits mounted on surplus printed circuit boards is an inexpensive way to obtain a good parts inventory. The main problem is getting the circuits off the board. Ralph Droms and Jonathan Bondy have dreamed up A Flameless IC Recycling Trick as one way to accomplish the recycling goal.

What does it take to program an 8080 debugging monitor? Joe Kasser and Richard Allen describe AMSAT's answer to this question in AMSAT 8080 Standard Debug Monitor: AMS80 Version 2. This is a complete assembly of a useful control program which can be adapted to any 8080 based microcomputer system.

1976/byte_1976_10.jpg 1976/byte_1976_10_index.jpg

Lire la revue / Get this issue (archive.org)

n°14 october 1976

Foreground

p.30 ADD THIS 6800 MORSER TO YOUR AMATEUR RADIO STATION

[theme Applications] [author Grappel-Hemenway]

p.42 IF ONLY SAM MORSE COULD SEE US NOW

[theme Applications] [author Sewell]

p.52 A MORSE CODE STATION DATA HANDLER

[theme Applications] [author Filgate]

p.74 BUILD THIS MATHEMATICAL FUNCTION UNIT- Part 2

[theme Software] [author Guthrie]

Background

p.12 THE COMPUTER ... VERSUS ... HAND SENT MORSE CODE

[theme Applications] [author Hickey]

p.26 A HAM'S APPLICATION DREAMS

[theme Speculation] [author Hosking]

p.36 EFFICIENT STORAGE OF MORSE CHARACTER CODES

[theme Applications] [author Krakauer]

p.82 KEEP PACE WITH THE TIMES

[theme Hardware] [author Baker]

p.90 HOMEBREWERY VS THE SOFTWARE PRIESTHOOD

[theme Philosophy] [author Fylstra-Wilber]

p.118 MEETING ACTIVITIES FOR COMPUTER CLUBS

[theme Organizations] [author Douds]

Nucleus

p.2 In This BYTE

p.9 The Concertina System

p.16 Letters

p.41 Software Bug of the Month 5

p.81 Some Historical Notes

p.86, 110, 126 What's New?

p.95 BYTE's Bits

p.96 Classified Ads

p.99 Programming Quickies

p.100 Book Reviews

p.106 Kil O'Byte

p.107 Travelogue

p.116 Excerpts from Future History

p.130 Clubs, Newsletters

p.144 BOMB

p.144 Reader Service

In this BYTE

About the Cover

As a way to highlight the history of electronic digital signalling, we dug up a picture of one of Jose ph Henry's original telegraphy keys, circa the early 1800s. Robert Tinney then placed the key in the frame and wall setting you see on the cover, using a photo supplied by Brian McCarthy.

The problem of decoding arbitrary hand generated Morse code is not a trivial one. It requires some care and thought in the design of adaptive algorithms. As one contribution to this issue's sub theme of computerized Morse code, Lt Willi am A Hickey, USN, provides some background information and suggestions on the subject.

W J Hosking, W7JSW, is an amateur radio operator in search of applications hardware and software. Read about A Ham's Application Dreams and find out how to implement one aspect of his dream with the Morse code input and output conversion technology described in detail in the balance of this issue ... .

A theme of this October issue is the application of microcomputers to the decoding of Morse code. One approach to the problem is detailed in Robert Grappel and Jack Hemenway's article on MORSER... a program to read Morse code, implemented with a Motorola 6800 computer. Lawrence Krakauer describes a technique to store Morse characters as a packed table of bit patterns for machine generated outputs - or for machine decoded inputs.

If Only Sam Morse Could See Us Now. He'd have a fistful of problems trying to copy radio transmissions at 1000 wpm generated by programs such as Way ne Sewell's CWBUFFER subroutine. But, using one of Wayne's set of sundry drivers for CWBUFFER, Mr Morse could potentially learn to copy - or at least have his computer copy - in a code practice mode.

One application of the Morse code problem solvers is documented in Bruce Fil gate's article on Morse Code Station Data Handler. This is an application program which handles direct sending of Morse outputs, from character text, adaptive interpretation of Morse inputs, storing of fixed messages (eg: ' CQ CQ CQ DE W1AW ') in a message buffer for later transmission or repetitive transmission, etc. Bruce has put it all together in the form of a comprehensive 1536 byte program for an 8008.

Once you sit down and Build This Mathematical Function Unit as described in part one of R Scott Guthrie's two part article, the world of high level mathematical functions is opened to your microcomputer. In part two this month, the software needed to interface with the calculator is described, as well as several test loops used to adjust timing parameters with an oscilloscope. As a final illustration of the calculator's use, the author provides a program called CALCULA which enables a Teletype (or other ASCII) port to drive the calculator and print results, simulating the ordinary hand calculator level of operation .

National Semiconductor announced the PACE computer some time ago, but until recently it has been somewhat hard to obtain . Now that this 16 bit minicomputer is beginning to enter its volume production stage, we Keep PACE With the Times by offering Robert Baker's Microprocessor Update on this processor. If you missed the convenience of your familiar 16 bit minicomputer when you started reading about and "dry run programming" for personal computing, then the PACE processor might be a logical choice for a homebrew or kit system.

The advent of the personal system portends a fundamental change in the ways computers are used. In Homebrewery vs the Software Priesthood, David Fylstra and Mike Wilber make some comments about the impact of widespread use and knowledge of computers.

Looking for ideas for meetings of your local computer group? Dr Charles F Douds has a few suggestions to make in his background article on the subject this month.

1976/byte_1976_11.jpg 1976/byte_1976_11_index.jpg

Lire la revue / Get this issue (archive.org)

n°15 november 1976

Foreground

p.26 BUILD THE BEER BUDGET GRAPHICS INTERFACE

[theme Graphics System] [author Nelson]

p.32 ADD THIS GRAPHICS DISPLAY TO YOUR SYSTEM

[theme Hardware] [author Buschbach]

p.42 AN ENTERPRISING DISPLAY DEVICE

[theme Hardware] [author Deres]

p.78 MAKE YOUR NEXT PERIPHERAL A REAL EYE OPENER

[theme Graphics Systems] [author Ciarcia]

p.106 BUILD THIS VIDEO DISPLAY TERMINAL

[theme Systems] [author Anderson]

Background

p.6 IT'S MORE FUN THAN CRAYONS

[theme Graphics] [author Rosner]

p.20 WHAT IS APL?

[theme Languages] [author Arnold]

p.40 A TIP FOR USING WIRING PENCILS

[theme Construction Techniques] [author Burhans]

p.56 SOME GRAPHICS BACKGROUND INFORMATION

[theme Graphics Systems] [author Rampil]

Nucleus

p.2 In This BYTE

p.10 A Proposed Standard for Publishing Binary Data in Machine Readable Form

p.16 The Address Space Saturation Problem

p.16 Outstanding Computer Hobbyist

p.54 Kil O'Byte

60, 67, 99, 140 What's New?

p.62 Description: MERLIN Video Interface

p.66 Something for Everyone

p.68 Letters

p.90 BYTE's Bugs

p.92 Clubs, Newsletters

p.104 Classified Ads

p.127 BYTE's Bits

p.132 Description: Astral 2000

p.144 BOMB

p.144 Reader's Service

In this BYTE

It's More Fun Than Crayons! Read how Mike and Alex Rosner, ages 7 and 5, discovered the joys of computet· art and incidentally proved the need for timesharing computers in the home. On the cover are super stats Mike and Alex at work.

If Isaac Newton were alive today, he'd be immersed in long and complicated physics manipulations, which are ultimately tested using calculations involving multidimensional matrices and matrix operations of linear algebra. Chances are he might be interacting with a computer, with an interpreter from the APL tree of languages. Read Mark Arnold's What Is APL? to find out a bit about APL, a language with a mathematical orientation but utility for general purpose programming as well.

How do you do graphics in a weekend, without spending a fortune? In Beer Budget Graphics, Peter Nelson tells all : how the synergistic combination of a couple of digital to analog converters and an output latch or two brings the world of point plotting to an oscilloscope for about $20 in parts.

In the July 1976 BYTE, we ran a functional specification for a graphics interface in answer to reader Paul Hyde Jr's letter. Practically before the ink had dried on the July press run (figure of speech) reader Thomas R Buschbach sent in this article on how he made just such a graphics interface for his Digital Group system using existing timing logic of the television display unit. Given an existing 8 K memory, processor and television display generator, this high resolution display can be added to a system for as little as $25 in additional semiconductors.

Star Trek freaks should turn to Joe Deres' article to find An Enterprising Display. In the article you'll find information on a design for a television graphics output which can be built from a kit (or your own parts) for less th an $100.

Ira Rampil provides Some Graphics Background Information, including a comparison of several display devices available to individuals.

Don't be satisfied with simple visual readouts. Make Your Next Peripheral a Real Eye Opener by implementing a true vector display using an XY oscilloscope, circuits and software similar to Steve Ciarcia's design. In his article you'll see how to draw a picture of a moderately high resolution Star Ship Enterprise.

Build This Video Display Terminal, advises Alfred Anderson, who took C W Gantt Jr's TV interface circuit described in the June 1976 BYTE, made a few changes, added a few goodies, and wrote a few lines of software. Now he tells you how you can do it.

What's NOT In This BYTE... Software Bug of the Month, Book Reviews, Ask BYTE, a slew of What's New and BYTE's Bits items we were dying to print, lots of good letters, and some dynamite articles. Even using smaller type in places didn't enable us to include much that we urgently wished to. If you missed it this month, watch for it next.

1976/byte_1976_12.jpg 1976/byte_1976_12_index.jpg

Lire la revue / Get this issue (archive.org)

n°16 december 1976

Foreground

THE CYBERNETIC CRAYON

p.24 [theme Graphics Systems] [author Dwyer-Sweer]

p.139 [theme Portfolio of Explorations] [author Critchfield]

p.30 THE BURIED GOLD IN THE SR-52

[theme Systems Programming] [author Penn]

p.42 STRETCH THAT 6800 CLOCK

[theme Hardware Modification] [author Henshaw]

p.58 DON'T WASTE MEMORY SPACE

[theme Software] [author Baker]

p.77 SIGNAL PROCESSING FOR OPTICAL BAR CODE SCANNING

[theme Hardware] [author Merkowitz]

p.98 THE DESIGNER'S EYE VIEW OF THE AC-30

[theme Product Description] [author Kay]

p.114 A UNIVERSAL TURING MACHINE

[theme Hardware] [author Millen]

Background

p.12 SAMPLES OF MACHINE READABLE PRINTED SOFTWARE

[theme PAPERBYTESTM] [author Banks-Sanderson]

p.18 SOFTWARE FOR READING BAR CODES

[theme Software] [author Regli]

p.36 PROCESSOR TECHNOLOGY VDM-1

[theme Product Review] [author Anderson]

p.62 DO IT YOURSELF WEATHER PREDICTIONS

[theme Applications] [author Firth]

p.110 BUILDING THE AC-30 CASSETTE INTERFACE

[theme Review] [author Liming]

Nucleus

p.2 In This BYTE

p.6 Caught by Surprise

p.48 Clubs, Newsletters

p.50 Letters

p.54 BYTE's Bugs

p.56 Ask BYTE

p.60,87 What's New?

p.70 About the Cover ... and the Contest

p.86 State of the Art Disk Technology

p.91 Software Bug of the Month 6

p.92 Desk Top Wonders

p.95 The First West Coast Computer Faire

p.60, 96 BYTE's Bits

p.108 Kil O'Byte

p.120 Book Reviews

p.128 Technical Forum

p.132 Programming Quickies

p.144 BOMB

p.144 Reader's Service

In this BYTE

If you're into programmable calculators, you've probably heard lots of rumors around the computer world about all those SR-52 hidden features, dug up by persistent and ingenious users who look upon the calculator as a puzzle. Well, confirm the rumors with Clif Penn's The Buried Gold in the SR-S2 written using "inside" information from Texas Instruments in Dallas where he works.

The information on machine readable printed software continues this month, with three articles. Introducing the subject for this issue is a short note by Walter Banks and Roger Sanderson presenting several detailed Samples of Machine Readable Printed Software at different densities, which our readers can use as test strings for experimental input hardware and software. In addition to the samples, Walter and Roger present some of their philosophical comments on the method and what led them to propose it.

Bar codes are an exciting new way to publish software in machine readable form. Turn to Keith Regli's article to find out about Software for Reading Bar Codes in the form of an algorithm specification for one approach to the problem.

Good things come in small packages. One such package was an envelope with nine excellent color slides by Margot Critchfield for our Computer Art Contest, along with an article by Thomas Dwyer and Leonard Sweer on The Cybernetic Crayon which was used by Margot to draw the pictures.

A key element of the complete computer system is a video display output device. In this issue, you'll find D Anderson's experiences with the Processor Technology VDM-1 summarized in the form of a Product Review and some software illustrating its use.

What happens when your speedy second generation microprocessor cannot keep pace with your turtle-like 1702 erasable read only memories? Why, buy some extra time with a slow memory interface circuit of course. Learn how to Stretch That 6800 Clock with Jerry Henshaw's article on an elegant modification to the Southwest Technical Products Corporation's 6800 processor.

If your memory space is limited, a bit of frugality in coding your character strings can save bits. Robert Baker shows One Way to Squeeze Fat Out of Text Strings in a bit packing scheme described in his article Don't Waste Memory Space.

Weather you do it or not, you'll enjoy Mike R Firth's ideas on how to create an automated weather station. Do It Yourself Weather predictions could conceivably be a whole field of home computer applications in itself.

To read a bar code requires a bit of signal processing in the analog world, prior to sending your processor a single bit TTL level signal. In his article on Signal Processing for Optical Bar Code Scanning, Fred Merkowitz provides some details on how to read the signals coming from photo diodes and photo transistors.

One of the signs of progress in the marketplace is the appearance of neat product concepts to service the peripherals needs of personal computing people. An excellent example of this is the new Southwest Technical Products AC-30 Cassette Interface, a modulator, demodulator and switching network which is designed to fit into an RS-232 communications line between the computer and a 300 baud terminal It adds the functions of tape recording and data recovery, with relays to control motor action automatically. Gary Kay, the designer of this interface, describes the circuit and its function in this issue.

One of the simplest and least expensive possible computer projects is a Universal Turing Machine or UTM. While hardly offering the UTMost in speed or performance, a UTM based on Jonathan K Millen's design would make an excellent tutorial project for a computer science laboratory course.

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