TRSDOS 2.3 Decoded and Other Mysteries

written by Matthew Reed

Title:TRSDOS 2.3 Decoded and Other Mysteries
Author:James Lee Farvour
Publisher:IJG, Inc.
Publication date:1982
TRSDOS 2.3 Decoded and Other Mysteries

TRSDOS 2.3 Decoded and Other Mysteries was written by James Lee Farvour and published by IJG in 1982. It was volume six in the TRS-80 Information Series.

In a way, this book was a companion to James Lee Farvour’s earlier Microsoft Basic Decoded and Other Mysteries. That book analyzed TRS-80 Model I BASIC in great detail, describing how each part of the language worked. At the end of the book, it included the commented portion of a disassembly of the BASIC. It did not include the complete disassembly because Microsoft never gave permission for that to be published.

TRSDOS 2.3 Decoded and Other Mysteries, also by Farvour, provides the same type of detailed analysis of Model I TRSDOS. One difference from the previous book is that this book was published with Tandy’s permission and it includes a complete disassembly of TRSDOS 2.3! This disclaimer appears near the beginning of the book:

The TRSDOS 2.3 disk operating system, including the listing of the machine-readable hexadecimal code and assembly language code contained in Appendix II and reproduced in part elsewhere in this book, is owned and copyrighted by Tandy Corporation. Reproduction is by written authorization from Tandy Corporation.

TRSDOS 2.3 Decoded and Other Mysteries consists of ten chapters and two appendices:

  • Chapter 1 provides an introduction to the Model I hardware.
  • Chapter 2 contains an overview of TRSDOS.
  • Chapters 3 through 9 cover the six overlay files, SYS0/SYS through SYS6/SYS, which comprise the bulk of the operating system.
  • Chapter 10 covers the boot loader, BOOT/SYS.
  • Appendix I contains a very detailed look at data structures within TRSDOS.
  • Appendix II contains a complete, commented disassembly of TRSDOS 2.3.

The degree of detail in this book is amazing and every aspect of TRSDOS 2.3 is described in depth. Several bugs in TRSDOS 2.3 are pointed out, along with some possible fixes. It is a great book for anyone who has ever wondered just how TRS-80 operating systems worked.

Categories: Books


David Sutherland says:

The “Authorized” comment reminds me of this Bill Gates interview from Dennis Báthory-Kitsz which I’ve felt hasn’t gotten the attention in might have provoked if more widely heard:

the full audio which is really the more interesting way to hear it is now offline. Fortunately because of you can still get it:

Download and start listening around 27m15s to hear Gates talk about Harv Pennington’s Microsoft Basic Decoded and Other Mysteries book.

Bill Ford says:

How interesting!!

After all these years I stumble onto this web site and see many of the things I was directly involved with… particularly the “TRS-80” and “Other Mysteries” series as I was the advertising and publications director with IJG, Inc., the publisher of the series. We operated out of the entire second floor of the Foothill Independent Bank building in Upland Calif. “IJG” actually stands for International Jewlery Guild as Elton Krug ((owner -ChinoHills CA) was a certified gem appraiser (GIA) and owned the jewlery store named “The Vault” in Upland.

Our very first “programming” project was a graphic oriented “diamond appraisal” program that would print out an appraiser’s identification and diagram of the stone… producing an official GIA Certified Appraisal document and that program was done on a “TI-59” calculator with printer attached. Harv Pennington (deceased) and I went to a Chino RS “01” store to look at the alleged “whiz-bang” TRS-80 that had all of 4k stuffed in the keyboard enclosure and was “booted up” using RS cassette tape and an RCA b/w monitor. A few days later we purchased the “one” the store had on display — I cannot remember the actual cost now that my RAM is 74 years old, but it was in the low thousands by the time we collected numerous accessories and “software”. Harv spend 28 hours a day delving into how the thing worked and wrote a new diamond appraisal program — on cassette tape!! Soon after selling several “appraisal systems” to certain jewlery appraisers, Harv discovered this thing called a “disk drive” — and other mysteries which launched collaberating with Randy Cook and others… the rest is pretty much history.

Harv Pennington did all the graphics in the numerous publications, mostly in the form of creative cartoons as he was a former employee as a professional cartoonist for Hana Barbara. Harv was also a private pilot and loved to do aerobatics in a Citabria in which I took a back seat on several “unwind” and sometimes scary flights. The “Wizard”, as Harv called it, cartoon became an icon in itself.

BASIC decoded. One of the books published actually “decoded” the stuff and was printed in such a manner that the reader could print out the “code” on a dotmatrix, then tear out the book pages which would exactly align the “comments” to the lines of code. That way, we didn’t actually “publish” the code, just the comments.

When the MX-80 printer came into existance, we thought we were in 7th heaven buying them in bulk and reselling from our Upland location. Harv Pennington discovered how to cleverly rewind the ribbons in such a manner that would use the “upper” half of the ribbon that still contained enough ink for in-house printing needs.

We also had a heavy hand in the development of Apparat’s NEWDOS, which eventually became another “and other mysteries” book.

Elton (Al) Krug and I and a few other former IJG folks and authors still communicate mostly via email. This web site here will be well received by all as it is certain to evoke fond memories from nearly 35 years ago. KUDOS on this historic compilation.

Bill Ford

Joshua Tree California 40 miles north of Palm Springs in the Mojave Desert.

Mark McDougall says:

@Bill – A very interesting read – I love reading about the stories behind the companies that, as a kid, I saw advertising in the TRS-80 magazines! I’ve managed to hold onto three of the ‘Other Mysteries’ books (not this one unfortunately) and won’t be letting them go anytime soon.

On a totally unrelated note; my wife and I visited Joshua Tree in 2009 from Australia and loved it (it was actually my 2nd visit). Stayed at the High Desert Motel which no doubt you’d know. Hidden Valley Trail was the highlight for me. We’re huge fans of the US national parks! I think you’re lucky to live there!