TRS-80 DOS - VTOS (Virtual Technology's Operating System)

VTOS (Virtual Technology's Operating System) was a TRS-80 Model I disk operating system written by Randy Cook, the original author of Model I TRSDOS versions 2.0 and 2.1. After parting ways with Tandy/Radio Shack over disputes regarding copyright ownership, royalties, and control of the source code, Cook formed his own company, Virtual Technology Inc. (based in Richardson, Texas), and continued development of his operating system independently.

Cook's agreement with Radio Shack allowed him to maintain ownership of the code he had written for TRSDOS. He used this original source code as the basis for VTOS, fixing the bugs that had plagued TRSDOS 2.1 and adding the features he had originally intended to include. Early advertisements sometimes referred to it as "TRS-80 DOS 3.0 Disk Operating System by the Original Author" before the VTOS name was consistently adopted.

There were no VTOS 1.0 or 2.0 releases. The version numbering started at 3.0 because Cook positioned VTOS as a direct continuation of TRSDOS 2.1 rather than a new product. VTOS was developed only for the Model I; there was never a Model III version.

VTOS was well-liked by many who used it. The advertisements boasted an endorsement by Lance Micklus and the "Scott Adams Seal of Approval." However, VTOS is remembered today primarily for two things: it was the only copy-protected TRS-80 operating system, and it was the direct ancestor of LDOS.

v3.0 Disk

v3.0 Bootup Screen

v3.0.1 Bootup Screen

VTOS 3.0 was the first commercial release from Virtual Technology, appearing in 1979 at a price of $49.95. It was marketed primarily as a bug-free, fully realized replacement for TRSDOS 2.1, fixing the infamous granule allocation flaws that destroyed files, the HIMEM bugs, and the unreliable keyboard debouncing that had plagued Tandy's official DOS.

VTOS 3.0 was designed to be compatible with software written for TRSDOS 2.1, ensuring users could transition without losing access to their existing programs. It used the same TRSDOS-style disk layout and directory structure: drives numbered :0 through :3, 8-character filenames with 3-character extensions, and slash separators.

While an improvement over TRSDOS 2.1, VTOS 3.0 had its own share of bugs and was hampered by aggressive copy protection that frustrated users. As Harv Pennington noted in TRS-80 Disk and Other Mysteries: he liked VTOS except for the protection features that made it difficult to use on an everyday basis and the difficulty in recovering a disk once it had been corrupted by the system. He did not recommend the use of VTOS 3.0 for those reasons.

v4.0.0 Disk

v4.0.0 Bootup Screen

v4.0.1 Bootup Screen

v4.0.2 Bootup Screen

VTOS 4.0 was the flagship release, appearing in early 1980. The price was increased to $99.95 for the operating system alone, or $125.00 including the Operator's Guide and Master Reference manual. It was a significant upgrade over 3.0: vastly improved and reliable, with none of the shortcomings of the earlier version.

VTOS 4.0 was the first TRS-80 operating system to store file dates, and the directory dating scheme it introduced became a de facto standard. The earliest possible TRS-80 file date is 1980 because VTOS 4.0 was introduced that year.

Key features of VTOS 4.0 included:

• File dating (the first TRS-80 DOS to support this)
• Keystroke multiplier (KSM)
• Job log
• High memory management
• Command line parameter parsing
• System configuration save/restore via SYSGEN command
• Dual-platform boot supporting both Radio Shack Expansion Interface and Lobo LX-80 hardware

VTOS 4.0 was distributed initially through PowerSoft (Dennis Brent) and later via other agreements, including Automated Computer Software (which went bankrupt amid disputes with Cook). Cook cited losses of over a million dollars from one bankrupt distributor.

VTOS holds the distinction of being the only copy-protected TRS-80 operating system, a decision that created significant frustration among users. The copy protection worked by leaving sector 4 of track 0 deliberately unformatted on the system disk. The VTOS loader checked for this special condition and would refuse to run if a copy attempted to normalize the track. Users who needed backup copies of their $99 operating system were effectively out of luck if their master disk went bad.

Tim Mann (who later became one of the five core LDOS developers) purchased a copy of VTOS 3.0, disassembled it, fixed bugs, and disabled the copy protection. During his disassembly work, Mann discovered hidden code within VTOS that could turn a normal disk into a "reproduction master." When booted, this modified disk would continuously scan all attached floppy drives for blank media. When a blank disk was inserted, the code would format it and create a copy-protected master disk that could itself produce further non-copyable system disks. Mann posted his bug fixes on CompuServe.

One commenter on your Easter Eggs page recalled: "I tried to copy it as a challenge. I succeeded once, when I opened and closed the disk drive while it made sounds as if it had reading errors. I believe the trick by Randy was to create defective sectors by a laser hole. Copies never had errors at that particular sector. That was how copies were identified."

In November 1980, Lobo Drives International signed a non-exclusive but broad-rights contract for VTOS 4.0. Lobo could not use Model I TRSDOS on their hardware because they were selling the LX-80 Expansion Interface, which used a different disk controller that was not hardware-compatible with Radio Shack's Expansion Interface. VTOS 4.0 had a second boot sector and additional code that enabled it to boot and run on both platforms, making it an ideal fit for Lobo's needs.

However, Lobo became disgruntled with Cook when he proved slow to deliver bug fixes and refused to release the VTOS source code. Unable to obtain the source, Lobo brought in Bill Schroeder of Galactic Software (Mequon, Wisconsin) and Roy Soltoff of Misosys (Alexandria, Virginia) to take over maintenance. They worked from the raw machine code, with Roy's disassembler proving essential to the effort. Tim Mann, who had already done significant disassembly work on VTOS 3.0, joined the team shortly after.

The project quickly expanded from a VTOS bug-fix effort into a joint venture to produce a completely new operating system. The result was LDOS (originally "Lobo Disk Operating System"), developed under the new company Logical Systems Inc. Cook was paid for rights to his work and was acknowledged in the LDOS manual.

The five core LDOS developers were Roy Soltoff (lead designer/programmer, Misosys), Bill Schroeder (Galactic Software), Tim Mann, Chuck Jensen, and Dick Konop. Their work produced an operating system that supported both Radio Shack and Lobo hardware, provided Model I/III media interchangeability, and supported hard drives. Bill Schroeder persuaded Tandy to license LDOS as its official hard drive operating system, and Logical Systems was later selected to develop TRSDOS 6 for the Model 4.

VTOS is remembered as a fascinating "what-if" in microcomputing history. It represents what TRSDOS would have been if Randy Cook had been allowed to finish his work under ideal circumstances. While it was eventually outclassed by NEWDOS/80 and LDOS in market share, VTOS's technical DNA lived on: through LDOS, and through LDOS's evolution into TRSDOS 6 (LS-DOS) for the Model 4, VTOS's code and design philosophy influenced TRS-80 operating systems throughout the entire product line's lifespan.

Several factors contributed to VTOS not becoming the dominant Model I DOS despite being authored by the creator of TRSDOS itself:

• The copy protection alienated power users who needed to make backup copies
• At $99.95, it was significantly more expensive than alternatives like NEWDOS ($49.95 and later free patches)
• Apparat's NEWDOS and NEWDOS/80 arrived quickly and were both cheaper and feature-rich
• LDOS, which evolved directly from VTOS, was eventually endorsed and sold by Radio Shack itself
• TRSDOS 2.3, provided free or at minimal cost by Tandy, was "good enough" for many users
• Recurring distribution and support issues plagued Virtual Technology's business operations

Randy Cook later worked on other projects, including DoubleDuty for the Model 4 in 1984. VTOS's direct story ends with its evolution into LDOS, but its influence extended far beyond its modest installed base.

• VTOS v4.0 Manual [PDF]
• VTOS v4.0 Manual [DOC]

• BOOT/SYS

• Passwords (ALL DOS'S)