[theme : Music Systems] [author : Struve]
[theme : Test Equipment] [author : Ciarcia]
[theme : Hardware] [author : Wenzlaff]
[theme : Interfacing] [author : McGahee]
[theme : Speculation] [author : Schmucker-Tarr]
[theme : Floppy Disks] [author : Rampil]
[theme : Software Techniques] [author : Grappel-Hemenway]
[theme : Software] [author : Higgins]
[theme : Modelling] [author : Smith]
[theme : Tutorial] [author : Wier]
[theme : Software] [author : Lahasky]
[theme : Hardware] [author : Libes]
[theme : Software] [author : McGath]
[theme : Software] [author : Gaskell]
[theme : Applications] [author : Lahore]
This month's cover is based on Kurt J Schmucker and Robert M Tarr's article, The Computers Of Star Trek (page 12). It is an appropriate topic for computer people, many of whom are science fiction aficionados, Trekkies, and users of the Force. The theme, interpreted by artist Robert Tinney, is: What would happen if the crew of the Enterprise visited a holographic museum of ancient technology that had an exhibit devoted to personal computing, circa 1977? Robert used Willard Nico and his 8080 based computer system with dual floppy disk, video terminal and DECwriter as models for the diorama. The cassette recorder, made obsolete by the disk drives, is shown unused.
The floppy disk can give your computer the extra storage power needed for many applications such as advanced music and voice synthesis, artificial intelligence and robotics. Find out more about the ubiquitous floppy in Ira Rampil's A Floppy Disk Tutorial.
Microprocessor operation code structure is sometimes incompletely documented, as is demonstrated in two articles: Gerry Wheeler's commentary on Undocumented M6800 Instructions and H T Gordon's commentary on The XF and X7 Instructions of the MOS Technology 6502. The effects of the undocumented op codes are interesting, even if you don't want to use them as part of normal coding practices.
In a neat combination of tutorial and practical information, Bill Struve's article A $19 Music Interface (and Some Music Theory for Computer Nuts) provides a way to generate square wave musical tones for four channels as a result of an investigation of the theory of harmony.
Transform your computer into a powerful 8 channel 3½ digit voltmeter. Steve Ciarcia shows you how in the latest installment of Ciarcia's Circuit Cellar. Let a BASIC program do all your calculations and get results that compare favorably with expensive digital voltmeters. Read On a Test Equipment Diet? Try an 8 Channel DVM Cocktail!
Once upon a time, Jack and the Machine Talked; now Jack and his friendly 6800 have moved onto better things like debugging the programs issued by the assembler described in an earlier article. Turn to Jack and the Machine Debug by Grappel and Hemenway for a humorous (but tutorial) account of the development of a program called Tracer 6800 which uses software breakpoint techniques to provide an instruction by instruction machine code execution trace on a terminal or hard copy device.
To write well conceived programs easily, you have to design them in a disciplined and structured fashion. David A Higgins begins describing one useful method in the article on Structured Programming with Warnier-Orr Diagrams, Part 1: Design Methodology.
As a second installment in a series of articles, Stephen P Smith turns to the problems of motion in which effects of the motion's current state feed back into the model. Turn to Simulation of Motion: An Automobile Suspension for a more detailed model which features damping (shock absorbers) and bounce (springs) in response to external conditions (bumps in a road).
The use of interrupts allows you to keep track of several devices at the same time. If you are not familiar with the use of interrupts read Robert Wier's article, A Little Bit on Interrupts.
Constructing and interfacing a PolyMorphics Video Interface is described by Wayne Wenzlaff. Wayne describes his experiences with his video interface and how he modified a television set for use as a monitor in Using the PolyMorphics Video Interface.
Multiprogramming allows your computer to seemingly perform several tasks at the same time. It can save processor time by always having a program executing while another program waits for some type of input. Prof Irwin Lahasky's article, Multiprogramming Simplified, explains the basics of multiprogramming.
Many experimenters, including the editors of this magazine, have discovered the real advantages of purchasing used but eminently usable gear. Sol Libes gives valuable pointers to frugal hackers in Where to Get Bargains in Used Computer Equipment.
As personal computer users acquire more and more memory for their processors, thoughts can be turned to more powerful languages for the expression of programs. Gary McGath feels that small computer users should have nonnumeric, symbolic data manipulation abilities in their langusages. In A Look at LISP, Gary describes one of the candidates for such symbolic manipulations in the small computer.
Relative addressing allows jumps within a program to be made independent of the location of the program in memory address space. But what about such position independent code in processors like the 8080 which have no relative branch addressing? Read James P Gaskell's Relative Addressing for the 8080 and learn how to simulate this feature for the 8080.
Handshaking is the process of coordinating two asynchronous processes, such as serial communication operations and a program. In a short article, Thomas McGahee shows how to Save Software: Use a UART for Serial IO.
What do you do if you're an oceanographer and want a microprocessor to help collect data at the bottom of the sea for eight weeks? One solution is to use a watertight titanium sphere and a battery powered processor. Henry Lahore shows how he did it in A User's Report on Intercept Jr.