Articles in the "FAQ" Category

What was the inspiration for TRSDOS?

Just about all computer software has taken inspiration from other software that has preceded it, and operating systems are no exception. For example, it is well known that MS-DOS was based on CP/M, with some ideas borrowed from TOPS-20. Windows has strong structural similarities to VMS (both were designed by Dave Cutler). CP/M was itself inspired by TOPS-10. UNIX was inspired by Multics. And the list goes on.

But what was the inspiration for TRSDOS, the disk operating system for the TRS-80? Randy Cook designed TRSDOS from scratch in 1978, but I think Datapoint DOS was his model. Datapoint DOS was the operating system for computers sold by Datapoint Corporation (originally CTC), such as the Datapoint 2200. Randy Cook had worked at Datapoint and it seems reasonable to assume that he was familiar with its concepts.

For example, here are three representative characteristics present in TRSDOS and all TRS-80 operating systems derived from it:

Why was the Model I uppercase only?

One of the biggest weaknesses of the TRS-80 Model I was the lack of lowercase characters on the screen. Although that omission was hardly unique to the Model I (many computers at the time lacked lowercase, including the Apple II), it was still a notable limitation that affected many applications, especially word processing.

The two people most responsible for the Model I (originally known as the Radio Shack TRS-80 Microcomputer System) were Don French and Steve Leininger. Don French, described as “the originator of the TRS-80 project,” was a buyer for Radio Shack who had long pushed for Radio Shack to manufacture a microcomputer. Steve Leininger was the engineer who designed almost all of the hardware of the Model I and created the original Level I BASIC.

Steve Leininger mentioned lowercase in a talk he gave to the San Diego Computer Society in September 1977, just one month after the TRS-80 was introduced:

Why was the Model I discontinued?

The TRS-80 Model I (originally known as the TRS-80 Microcomputer System) was introduced by Radio Shack on August 3, 1977. It was one of the first mass-marketed, fully-assembled microcomputers and quickly became the best-selling personal computer.

Yet despite continued demand, Radio Shack discontinued the Model I on January 1, 1981, slightly less than three and a half years after it was first introduced. The culprit was not customer demand (which remained high) but new radio interference regulations from the United States Federal Communications Commission (FCC) which took effect on that date.

How popular were the TRS-80 magazines?

80 Microcomputing, later 80 Micro, was the most popular of the TRS-80 magazines. It was ranked the seventh fastest growing magazine in 1982 and was the third thickest magazine that year. (Those figures were for all magazines, not just computer magazines.)

80 Microcomputing began publishing in 1980, and its circulation rose steadily until it topped 124,000 readers in 1983. Circulation began a slow decline after that although subscriptions picked up slightly in 1985.

Was the Model III created to replace the Model I?

The TRS-80 Model III, introduced in August 1980, is often described as a replacement for the TRS-80 Model I, introduced in August 1977. Considering that the Model I was discontinued just six months later due to its failure to meet new FCC regulations, it is easy to assume that the Model III was always intended to replace the Model I.

But Radio Shack showed no sign of any plans to discontinue the Model I after the introduction of the Model III. It remained in the catalog at a price $200 lower than the Model III. Jon Shirley, Vice President of the Computer Division at Radio Shack, wrote in his “View from the Seventh Floor” column in the September 1980 issue of the TRS-80 Microcomputer News:

Was the TRS-80 once the top-selling computer?

It is often stated that the Apple II dominated the computer market from its introduction in 1977 and that the TRS-80 and other competitors remained only minor players. Although often repeated, the numbers don’t bear out this assertion. Apple sold around six million Apple II’s between 1977 and 1993, but sales started slowly and built up over time.

What does S-80 mean?

“S-80” was a non-trademarked synonym for for the trademark “TRS-80.” It was usually used to refer to the TRS-80 expansion bus (“S-80 bus”), but sometimes it was used as an all-encompassing term for the TRS-80 and compatibles (“S-80 computers”). Other notable uses include the newsletters S-80 Bulletin (originally TRS-80 Bulletin) and S-80 Computing (originally TRS-80 Computing) and the magazine Softside: S-80 Edition.

One definition of the term appeared in the March/April 1980 issue of 80-U.S. Journal:

What did TRS-80 stand for?

The name TRS-80 stood for two things:

  • TRS stood for Tandy Radio Shack, the company that created the TRS-80.
  • 80 was taken from the Zilog Z80, the processor used in the original TRS-80 Model I.

Tandy continued to use the TRS-80 name for their future computers, even for ones that didn’t use a Z80. For example:

Was the Model I ever sold as a kit?

Some have claimed that Radio Shack offered the Model I as a kit before selling it as a fully-assembled computer. That is not true. From the very beginning, the TRS-80 was sold only fully assembled and there was never a TRS-80 kit option in any Radio Shack catalog.

Was the official name Model 3 or Model III?

Model III was the official name, although 3 and III were and are used interchangeably by many people.

The Model I, II, and III were the only three TRS-80 computers to be identified with Roman numerals in the Radio Shack catalogs. Although some pre-release information identified the “Model IV,” the Radio Shack catalogs always used “Model 4.” All future computer models used ordinary numbers.