[editor : Carl T. Helmers Jr.] [publisher : Virginia Peschke, Manfred Peschke] [art : Matthew Arnorld, Noreen Bardsley, Mary Jane Frohlich, Lynn Malo, Bill Morello] #Magazine

#Abstract

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.

[author : Carl Helmers] #Edito

Extract : «  Sometimes it is fun to take an old Yankee attitude of smugness when one participates in a turn of events which is unexpected, which was not foreseen by many, and which seems to have been missed by established circles. This attitude is one which can be shared by all who participate in this field of personal computing, as designers, as entrepeneurs and as users of the products. Virtually overnight, we — you the reader, you the manufacturer, to say nothing of myself and associates at BYTE and other publications — have demonstrated the existence of supply and demand for products which were nearly completely overlooked by established circles. Elements of this attitude of achievement were present in my conversations with entrepeneurs Bob Marsh (Processor Technology), Chris Rutkowsky (Technical Design Labs), Steven Jobs (Apple Computer Co) and Paul Terrell (Byte Shops) on the floor of the WESCON show last September in Los Angeles CA. The attitude crystalized into immediate focus on September 23 when Virginia Peschke and I travelled to Connecticut on business which was followed by a social call at Scelbi Computer Consulting Inc to meet Nat Wadsworth and his associates. [For those unfamiliar with the history of the field, Nat Wadsworth is probably the first person ever to manufacture a general purpose computer kit, the Scelbi 8B and 8H products, based upon an 8008. His product was a real entry into the marketplace, advertised in amateur radio publications long before the Radio Electronics Mark-8 articles of 1974, and long before Ed Roberts, MITS and the Altair were launched on their present course in January 1975 thanks to another pioneer willing to take risks, Leslie Solomon of Popular Electronics. The Scelbi product was a well designed general purpose processor with ROM systems software, conceived shortly after Intel first announced the 8008. [...]  »

TABLE OF CONTENTS

[theme : Graphics Systems] [author : Dwyer-Sweer] #HowItWorks #Digitization #Graphics #Listing #Assembly

Extract : «  The Cromemco TV Dazzler (described in BYTE No. 10, June 1976, page 6) is one of the most interesting (as well as economical) peripherals available for displaying computer output. It literally puts a picture of what's in your computer's memory on a home color TV set. The simplicity of this idea cuts through all the complexities that expensive color graphics systems (some costing over $100,000) have presented to "ordinary" computer users in the past. The potential applications of low cost color graphics, especially in learning environments of the type we have been developing at Soloworks [The Soloworks lab is concerned with using computers in education as tools for supporting student creativity. A newsletter describing the project is available from author Dwyer.] , are almost endless. [...]  »

[theme : Portfolio of Explorations] [author : Critchfield] #Experience #Digitization #Graphics

Extract : «  The use of this system can lead to quite practical results for the artist. What called the Crayon System to our attention and resulted in this article was Margot Critchfield's first entry into the BYTE Computer Art Contest, the pastoral scene, photo 7. Here are several of the Art Contest entries which Margot Critch field has created using the Cybernetic Crayon system described by this article. The comments are based on Margot's notes with direct quotes as indicated. [...]  »

[theme : Systems Programming] [author : Penn] #HowItWorks #ComputerPortable #Listing #TI

Extract : «  In the April 1976 issue of BYTE, a good overview comparison of the programmable SR-52 and the HP-65 was presented by Bradley Flippin [page 36]. Now some hidden but powerful features of the SR-52 organization will be discussed. At this time these features have not yet appeared in the literature Texas Instruments supplies with the SR-52, but the capabilities are worth documenting for readers who use this calculator. [...]  »

[theme : Hardware Modification] [author : Henshaw] #Electronic #Memory

Extract : «  I recently completed construction of my Southwest Technical Products M6800 Computer System. One of my first projects was to build a slow memory interface to allow the M6800 microprocessor to communicate with memory devices that have slow access times. The SWTPC system runs at 895 kHz. This clock rate forces any memory element to have an access time of approximately 700 ns or less. The M6800 running at full speed (1 MHz) requires memory devices to have an access time of 575 ns or less. I wanted to use electrically erasable read only memories to store an audio cassette operating system. These EROMS have access times in the one microsecond range and are therefore too slow for a M6800 system running at maximum speed or at the SWTPC 6800 clock rate. [...]  »

[theme : Software] [author : Baker] #Encoding

Extract : «  If your system uses plenty of canned messages, chances are you're wasting valuable memory space. Most small systems are currently using a 7 bit ASCII code with one character per 8 bit byte of memory space. Why use a 7 bit code, capable of selecting 128 characters, when you really only need 64 or even 40 different characters for simple alphanumeric text? Your simple video display may only be able to handle 64 characters anyway, so why waste memory space needlessly? [...]  »

[theme : Hardware] [author : Merkowitz] #Electronic #Digitization #Optics

Extract : «  To input bar coded data into your system it is necessary to convert the printed variable width bars into logic level signals suitable for serial data entry. To convert the serial bit stream into parallel, byte organized data, pattern recognition techniques are necessary. This article outlines the basics of the hardware aspects of bar code scanning covering various optical systems, detector characteristics, and signal conditioning. The software aspects are covered in another article in this issue of BYTE. [...]  »

[theme : Product Description] [author : Kay] #HowItWorks #Interface #Storage #Electronic

Extract : «  Cassette tape is one of the most flexible and least expensive means of mass data storage for computer systems. When compared to paper tape readers and punches, you'll find that although the paper tape readers can be made rather inexpensively, the punches cannot. Paper tape systems are typically slower and the punched tapes cannot of course be repunched and used over and over again, as you can with cassettes. Disk systems on the other hand offer significant advantages over cassettes but are still too expensive for many applications, and for most low cost personal computer users. Even those lucky enough to have a disk system still need a more universal medium for exchanging programs. [...]  »

[theme : Hardware] [author : Millen] #Computer #HowItWorks #Electronic

Extract : «  Everyone who has had an elementary course in the mathematical foundations of computer science knows you don't actually build Turing machines, you just theorize about them. Besides, what about that infinite tape? Well, the temptation was too great to resist. After all, you can do anything with a Turing machine that you can with any other kind of computer. It just takes longer. As for the tape, only a finite amount could ever be used in your lifetime anyway. [...]  »

[theme : PAPERBYTESTM] [author : Banks-Sanderson] #Graphics #SoftwareDistribution

Extract : «  One of the papers at the standards session of Personal Computing 76 was our proposal that the popular magazines adopt a printed machine readable standard which would allow programs to be widely distributed. Following the Atlantic City conference the full impact of this proposal has been brought home. [...]  »

[theme : Software] [author : Regli] #Algorithm #Digitization

Extract : «  The problem of transferring programs and data from one computer system to another has long been a problem in industry, but for the hobbyist it is especially difficult. Paper tape and cassettes have solved the problem for communication between individuals, but what about a program published in BYTE magazine? Keying in a hexadecimal listing is painful and error prone, and machine readable forms such as phonograph record inserts are too expensive for regular use. A possible solution is at hand! [...]  »

[theme : Product Review] [author : Anderson] #Review #Interface #Display #Listing #Assembly

Extract : «  Processor Technology's Video Display Module for the Altair, IMSAI, and other Altair compatible machines is of excellent quality. The board has gold plated fingers, and solder resist (green lacquer) on both sides of the board. All component designations are silkscreened and are easily readable. The board displays 16 lines of 64 characters on a standard video monitor or modified TV. [...]  »

[theme : Applications] [author : Firth] #HowItWorks #Build #Electronic #Meteorology

Extract : «  One of the most challenging tasks for a computer owner can be working up the software and hardware to permit analysis of the weather and prediction of what is coming. Whether you wish to develop some software and take readings yourself or develop the hardware and do your own analysis or have the computer carry out both tasks, you can enter into a challenging and fascinating world of computer applications. [...]  »

[theme : Review] [author : Liming] #Experience #Build #Interface #Storage

Extract : «  Any hobbyist who has ever loaded a sizeable program on a bit by bit or byte by byte basis, only to have it wiped out when the power is removed, really understands the significance of mass storage. Cassette recorders are attractive mass storage devices to a hobbyist because they are inexpensive and can be interfaced easily. [...]  »

#Association

#Book

Extract : «  Scientific Analysis on the Pocket Calculator by Jon M Smith, John Wiley & Sons, New York, 1975, 392 pages and one errata sheet. $13.75. [...]

A Guided Tour of Computer Programming in BASIC by Thomas A Dwyer and Michael S Kaufman, Houghton Mifflin Company, Boston, 1973; 8 1/4 X 11, 156 pages. Paperback $3.60. [...]  »