LDOS and Me
LDOS and MeIn a previous life, I used to be an operating system programmer for the Radio Shack TRS-80 Model I and Model III. No, I didn't work for Radio Shack. I worked indirectly for Logical Systems, the company that produced LDOS and (later, after I left) Model 4 TRSDOS.
In 1980-81 when I worked there, Logical Systems was a new joint venture, just getting started. The principals were Misosys (Roy Soltoff's company, in Alexandria, VA), Galactic Software Ltd. (Bill Schroeder's company, in Mequon, WI), and Lobo Drives (in Goleta, CA, near Santa Barbara). The name was chosen because Logical starts with an "L," providing an alternative explanation for the name "LDOS," which originally stood for "Lobo Drives Operating System."
LDOS evolved from an operating system called VTOS 4.0, which was supplied to Lobo Drives by Randy Cook, the same programmer who wrote the original Model I TRSDOS (up through version 2.1) for Tandy. Lobo couldn't use Model I TRSDOS on their hardware, because they were selling an improved disk interface of their own design (the LX-80) that was not hardware compatible with Radio Shack's disk interface. VTOS had a second boot sector and additional code that enabled it to boot and run on both platforms.
Lobo became disgruntled with Cook when he proved unable or unwilling to fix the many serious bugs in VTOS, and they hired Galactic and Misosys to work on it. They obtained rights to the system from Cook, but were unable to persuade him to supply source code, so all the work had to be based on the raw machine code. Fortunately Roy had an excellent disassembler! The project soon expanded from an effort to fix up VTOS for use by LX-80 owners into a joint venture to produce a new operating system, LDOS, for sale to the TRS-80 public at large.
I got involved shortly after this process began. I was finishing college at the time. Just for fun I had been disassembling a copy of VTOS 4.0 that I had bought directly from Virtual Technology, Cook's company. I found a large pile of bugs and started posting fixes on CompuServe, then a very new service. After Cook stopped supporting VTOS, Dennis Brent, his main distributor, issued an updated release with many patches and some extra utilities from me and a few other folks. Dennis, who is a great guy, even sent me an unsolicited royalty check.
Bill Schroeder soon found out about my work on VTOS and offered me a job with Galactic to work on LDOS. Conveniently, I lived in Milwaukee, just a few miles south of Mequon. I became a major player on the team. There were five of us involved, four at Galactic (Bill, me, Chuck Jensen, and Dick Konop) and one at Misosys (Roy). We all did a mix of design, programming, debugging, documentation writing, writing for the LDOS Quarterly, phone support, and CompuServe bulletin board support, in varying proportions. Roy was the lead designer and programmer, while I probably had the second-largest role in those areas while I was there. I worked only on LDOS, while the others all had other Galactic or Misosys products to support as well.
I remember contributing PR/FLT, the Model III RS232 driver, parts of the Model I Doubler driver, extensions to Basic, a rewrite of the LX-80 ROM, CONV/CMD, bits of documentation, LDOS Quarterly articles, and many bug fixes. I gained a very thorough knowledge of Model I and III hardware, including such variants as the Percom and Radio Shack double density adaptors for the Model I, as well as the LX-80. I ended up replacing my Radio Shack Expansion Interface with an LX-80.
Our work resulted in an excellent operating system for stock Radio Shack hardware as well as Lobo hardware, and we soon started porting LDOS to the Radio Shack Model III as well. Unlike Radio Shack's Model I and III TRSDOS, LDOS provided full media interchangeability between Model I and III, allowed application programs to be easily written or patched to run on both systems, and supported hard drives.
While I was still there, Bill persuaded Tandy to license LDOS as its official hard drive operating system. This was an amazing coup for our tiny company. Later Logical Systems was selected to do TRSDOS 6 for the Model 4. Roy and the rest of the team started with the LDOS 5 code base, so I'm sure that some of my code survived.
I left after less than a year (in September '81) to work on a Ph.D. in computer science at Stanford. I still did some consulting for Logical Systems on the side for a year or two. Ironically, my first job after finishing my Ph.D. six years later paid less than Bill had been offering me to stay at Logical Systems in 1981. On the other hand, the company was nearly dead by 1987; they failed to find a new direction as Z-80 systems became outmoded. Eventually Misosys bought Logical Systems (which had earlier bought out Galactic), and Bill got out of the microcomputer business. A few years later Roy folded Misosys and got out of the business himself.