The Holmes VID-80

The Holmes VID-80 was a popular add-on for the TRS‑80 Model I and III. Introduced by Holmes Engineering, Inc. in 1982, the VID-80 offered two related features:

  • It expanded the TRS‑80 screen from 64 characters wide by 16 characters high to the larger 80 characters wide by 24 characters wide.
  • It changed the TRS‑80 memory map to allow running the CP/M operating system.

The VS-100 Voice Synthesizer

The Alpha Products VS-100 was a popular voice synthesizer for the TRS‑80, selling thousand of units. Introduced in 1983 by Alpha Products for a price of $69.95, the VS-100 was available for the TRS‑80 Model I, Model III, Model 4, and also the Color Computer. Alpha Products lowered the price of the VS-100 several times; it was reduced to $49.95 in 1985 and $24.95 in 1987.

The VS-100 was a 3″ by 5″ unit that connected to the expansion port of the Model I, Model III, or Model 4. It came with a power adapter, but not the required external speaker. Alpha Products sold a “handsome speaker module” separately for $5.95.

An Exatron Stringy Floppy Primer

I recently added emulation of the Exatron Stringy Floppy to my TRS‑80 emulator for Windows. This has created some new interest in the Stringy Floppy, a storage device which was a popular add-on for the TRS‑80 back in the early 1980’s.

The Stringy Floppy is one of those items that many people remember, but they remain a little fuzzy on the details. Here is more information about the commands used on the Stringy Floppy.

The Holmes Expansion Mainframe

The Holmes Expansion Mainframe was a popular alternative to the Radio Shack Expansion Interface for the TRS‑80 Model I. Introduced in mid-1982, the Expansion Mainframe offered expansion options in a different manner than its competition. It provided extra features through the installation of special plug-in modules, also sold by Holmes Engineering. In addition to supporting the Model I, the Expansion Mainframe was also described as being compatible with the PMC‑80 when used with the PMC to TRS‑80 adapter sold by Personal Micro Computers.

The Expansion Mainframe was known as a very reliable unit, with gold-plated connectors and all data lines fully buffered. For maximum reliability, Holmes Engineering also recommended gold-plating the connector on the Model I itself using a product such as Gold Plug 80. The Expansion Mainframe was often paired with two earlier Holmes Engineering products, the SPRINTER speed-up board and the Internal Memory memory expansion.

The Expansion Mainframe was housed in an off-white metal enclosure, measuring 16 1/2″ by 9 1/8″ by 2 7/8″, which also served as a base for the Model I monitor. It came in two versions:

The Radio Shack Double-Density Disk Kit

The original TRS‑80 Model I, when paired with a Radio Shack Expansion Interface, was only capable of single-density floppy disk access. This limitation was addressed by the Percom Doubler, introduced in 1980, which modified the Expansion Interface to add double-density. The Percom Doubler soon became the de-facto standard for double-density interfaces on the Model I. Almost all companies that created double-density add-ons made them compatible with the Percom Doubler.

The Radio Shack Double-Density Disk Kit (catalog number 26-1143) was Radio Shack’s own double-density add-on for the Model I. Introduced on May 1, 1982 (nearly one and a half years after the Model I was discontinued), the Double-Density Disk Kit cost $149.95, not including installation. Despite the official name, many people referred to it as the Radio Shack Doubler.

Like the Percom Doubler, the Double-Density Disk Kit installed inside the Radio Shack Expansion Interface. It was described this way in the catalog:

The Stickeroo Joystick Interface

The Stickeroo Joystick Interface was an Atari-style joystick interface for the TRS‑80 Model I and System 80 computers. Introduced in 1982, the Stickeroo was sold by Micro-80, an Australian magazine dedicated to the TRS‑80 and System 80. (The System 80 was nearly identical to the computer sold in the United States as the PMC‑80.) The original advertisements also mentioned an upcoming TRS‑80 Model III version of the Stickeroo, but that was presumably never produced.

The “Micro-80 Product Catalogue” was a multiple page section of Micro-80 that sold TRS‑80 and System 80 hardware and software by mail-order to “customers throughout the Australian and Pacific region.” Many of the products were imported from the United States, but others, including the Stickeroo Joystick Interface, were products of Australia.

The CR-510 Card Reader

The Radio Shack CR-510 Card Reader was introduced in 1984 at a cost of $1595.00. Aimed primarily at schools, it appeared in the Radio Shack catalog under the headline “Automate Time-Consuming Tasks with a TRS‑80 Computer Card Reader.”

Administrators, teachers, and students can benefit from this new TRS‑80 input device. Automate data compilation, evaluate surveys and polls, or correct multiple choice tests. The CR-510 provides single, demand, or continuous feed operation and is controlled through manual switches or software. Cards must be at least 6 inches in length and can be either marked or punched (with standard keypunch).

The CR-510 communicated through the RS-232 port, so it could connect to any TRS‑80 computer. It came with 200 cards and a disk with sample drivers written in BASIC and COBOL. Those sample drivers must have been important when you consider that there was no software available for the CR-510!


VisiCalc is one of the most important programs ever created for microcomputers. It was not only the first spreadsheet program but is also generally regarded as the first “killer app.” It was the top selling program for four years, selling more than 200,000 copies in its first two years alone. Its popularity helped to drive early personal computer sales; many people bought a personal computer just to use VisiCalc.

Dan Bricklin came up with the idea for an “electronic spreadsheet” while still a graduate student at Harvard Business School. He and Bob Frankston founded Software Arts, Inc. in 1979 to explore the idea and VisiCalc was the result.

First demonstrated at the National Computer Conference in June 1979, the Apple II version of VisiCalc was shipped on October 17, 1979. Although developed by Software Arts, VisiCalc was sold by Personal Software (later VisiCorp), a company founded in 1976 by Dan Fylstra and Peter Jennings.

VisiCalc for the Apple II was so successful that versions for other computers were inevitable. The initial targets were the Commodore PET, the Atari 800, and the TRS‑80 Model I. The Commodore PET and the Atari 800 shared the same 6502 processor as the Apple II and could use the same VisiCalc code. But the TRS‑80 version required converting the VisiCalc code to use the Z80 processor, a project undertaken by Seth Steinberg. Despite this, both the Atari 800 and TRS‑80 versions were released in late 1980, almost a year after the release of the Apple II version.

H&E Computronics Magazine

H&E Computronics, Inc. was well known for their line of business software for the TRS‑80 and other computers, including programs such as VersaReceivables and VersaLedger. But they were probably best known for their TRS‑80 monthly magazine, which billed itself as “the original magazine for TRS‑80 owners.” It was called by a number of different names over its publication history, including TRS‑80 Monthly Newsletter, TRS‑80 Monthly Magazine, and H&E Computronics Monthly News Magazine. But most people knew it as H&E Computronics Magazine or just H&E Computronics.

The first issue was published in July 1978 as TRS‑80 Monthly Newsletter with this mission statement:

The purpose of the TRS‑80 Monthly Newsletter is to provide and exchange information related to the care, use, and application of the TRS‑80 computer system.


DOSPLUS was one of the most popular of the disk operating systems available for the TRS‑80. Sold by Micro-Systems Software based in Hollywood (later Boca Raton), Florida, there were eventually versions of DOSPLUS for the TRS‑80 Model I, Model III, Model II, and Model 4.

The people behind Micro-Systems Software were Larry Studdard, Mark Lautenschlager, Steve Pagliarulo, and later Todd Tolhurst. According to a 1981 interview in 80-U.S. Journal, DOSPLUS came about indirectly when they were writing software for Larry Studdard’s sheet metal business. Steve Pagliarulo developed a number of patches to TRSDOS to deal with bugs they had encountered. That experience led Pagliarulo to write his own TRSDOS-compatible replacement operating system, which became the first version of DOSPLUS. That original version was never publicly released and was used only with their business software.

In 1980, Micro-Systems Software introduced DOSPLUS 3.0, the first publicly available version of DOSPLUS, for $99.95. The name “DOSPLUS” presumably identified it as an improvement to the Radio Shack DOS or as “DOS Plus.” Although not actually the third version, it used a 3.0 version number to show that it followed TRSDOS 2.3. Advertisements described it as “the fastest, most reliable, and easy-to-use operating system available.”