Version Numbers

Computer software has always used version numbers, but there have been many different ways of managing them. (For an interesting history of version numbers, see the article The Amazing World of Version Numbers by Harry McCracken.)

Most personal computer software followed a consistent pattern of major and minor version numbers. I found this description of the Radio Shack approach to version numbering from the TRSDOS and DISK BASIC Reference Manual to be interesting:

Zorlof the Magnificent

Zorlof the Magnificent was a powerful word processor for the TRS‑80 Model I and III. It was written by Peter Ray and sold by Anitek Software Products of Melbourne, Florida. Released in 1982 for a price of $69.95, Zorlof was often described as a “second-generation word processor,” one generation beyond Electric Pencil and Scripsit.

Zorlof was a full-screen word processor that supported lowercase on the Model I. It provided 61 editing functions, which included common tasks such as deleting lines, global search and replace, and block moves. Word-wrapping and justification were automatically handled by Zorlof. As it stated in the manual:


MULTIDOS was one of the major TRS‑80 operating systems, described in advertisements as “the most compatible, user friendly operating system on the market.” It was written by Vernon Hester, the author of ULTRADOS, and was in some ways a continuation of that operating system. MULTIDOS was the least expensive TRS‑80 operating system and also the one with the most recent update (MULTIDOS 5.1 in 2005). It was also the only TRS‑80 operating system to offer software compatible versions for the TRS‑80 Model I, Model III, Model 4, and the Lobo MAX‑80.

ULTRADOS was an earlier TRS‑80 operating system for the Model I that was sold by Level IV Products. After Vernon Hester parted ways with Level IV Products in 1981, he began writing a completely new operating system. This operating system, which was briefly advertised as ULTRA-II, soon became known as MULTIDOS. Vernon Hester originally sold MULTIDOS through his company, Cosmopolitan Electronics Corporation. The Model I version of MULTIDOS was released in late 1981 and the Model III version was released in January 1982. The price started out at $79.95 but soon increased to $99.95. Later on, MAX‑80 MULTIDOS was released in late 1983 and Model 4 MULTIDOS (originally known as MULTIDOS 80/64) in 1985.


M-ZAL was a powerful disk-based editor assembler system for the TRS‑80 Model I and III. First introduced in 1981, M-ZAL (which stood for Modular Z80 Assembly Language) was written by Jeffrey Krantz and David Willen. It was sold by Computer Applications Unlimited (also known as CUA) for the price of $149.95.

Although expensive, M‑ZAL was one of the most advanced assemblers ever written for the TRS‑80 and it was used by many professional TRS‑80 developers. The advertisements contained endorsements from several TRS‑80 authors, including:

Mayday Uninterruptable Power Supplies

Mayday was a line of uninterruptible power supplies for the TRS‑80 and other computers. It was sold by Sun Research (originally Sun Technology), a division of Phase-R Corporation.

Phase-R Corporation was located in New Durham, New Hampshire and experienced frequent problems with poor power quality and frequent outages. They originally developed the Mayday to protect the office TRS‑80’s, describing it as “designed and developed using a complete TRS‑80 system.” Sun Research introduced the first Mayday model in 1980.

Echo-80 Speech Synthesizer

Street Electronics Corporation sold a variety of speech synthesizers with the Echo name. The Echo II, the Apple II version, was the most popular, but they also sold versions for other computers. As of 1982, there were four versions:

  • Echo-80 for the TRS‑80 Model I and III
  • Echo II for the Apple II
  • ECHO-100 for S-100 computers
  • ECHO GP (General Purpose) for any computer with a RS-232 or parallel printer port (including a TRS‑80)

TC-8 Cassette System

The TC-8 Cassette System was a hardware add-on from JPC Products that provided faster and more reliable cassette storage for the TRS‑80 Model I. Advertised as “The Poor Man’s Floppy”, the TC-8 provided features similar in many ways to the Exatron Stringy Floppy. The TC-8 could store up to 300K on an single 30 minute cassette tape. It increased the standard TRS‑80 cassette data rate from 500 baud to nearly 3000 baud. It also promised much greater reliability, “less than one bad load in a million bytes.”

The TC-8 was derived from the TC-3, a similar cassette system that JPC Products created in 1978 for 6800 computers. When introduced in 1980, the TC-8 cost $69.95 for a kit and a $99.95 for a fully assembled version. Those prices soon increased to $89.95 for the kit and $119.95 for the fully assembled version. The JPC Products advertisements recommended that buyers consider the kit version, saying:

Space Colony

Space Colony was a TRS‑80 adaptation of the 1978 Taito arcade game hit Space Invaders. It was written by Kim Watt and sold through his own company, Breeze Computing. Kim Watt was better known in the TRS‑80 world for his disk utility, Super Utility. Some sources say that Space Colony was also distributed by Adventure International, but I haven’t found it listed in any catalog.

Interestingly, Space Colony wasn’t the first version of Space Invaders that Kim Watt wrote for the TRS‑80. He had earlier written Invaders, a game distributed by Level IV Products. Space Colony was a good rendition of Space Invaders and had superior graphics and game play to Invaders. But it had one very unusual feature: it was one of the few commercial high-resolution Model I games.


The E/RAM was a high-resolution add-on for the TRS‑80 Model I. Introduced in 1980 for a price of $349.95, the E/RAM was designed and manufactured by Keyline Computer Products from Tulsa, Oklahoma. It was sold by Vern Street Products, also in Tulsa.

The E/RAM (an acronym for Extended Random Access Memory) contained 6K of video memory. It increased the TRS‑80 graphics resolution to 256 by 192, with the high-resolution graphics overlaying the text screen. The graphics could be enabled and disabled using either software or a hardware switch.

The E/RAM came in a steel case measuring 2 1/2″ high, 6″ wide, and 12″ deep. The self-contained unit sat next to the Model I and installed in a straightforward way:

Percom Data Company

Percom Data is one of the best remembered TRS‑80 hardware companies. Percom Data and its founder Harold Mauch were responsible for many of the most important TRS‑80 hardware products, including the Percom Separator and the Percom Doubler.

Percom had its origins in a symposium sponsored by BYTE magazine in November 1975. That event, held in Kansas City, Missouri, was about the “interchange of data on inexpensive consumer quality audio cassette drives.” The eighteen attendees (including Bill Gates) created a cassette storage format that became known as the “Kansas City Standard.” The final standard, published in the February 1976 issue of BYTE, was written by Lee Felsenstein and Harold Mauch. Harold Mauch also wrote an article, “Digital Data on Cassette Recorders” that was published in the March 1976 issue of BYTE.