The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer developed by American company Tandy Corporation and was sold through their Radio Shack stores.

While the software environment was stable, the cassette load/save process combined with keyboard bounce issues and a troublesome Expansion Interface contributed to the Model I's reputation as not well-suited for serious use.

The Model I was discontinued shortly thereafter, primarily due to stricter Federal Communications Commission (FCC) regulations on radio-frequency interference to nearby electronic devices.

[11][12][13][14] Tandy had 11 million customers that might buy a microcomputer, but it would be much more expensive than the US$30 median price of a Radio Shack product, and a great risk for the very conservative company.

Leininger persuaded Roach and French to include a better keyboard, a monitor, datacassette storage, and other features requiring a higher retail price to provide Tandy's typical profit margin.

When Charles Tandy asked who would buy the computer, company president Lewis Kornfeld admitted that they did not know if anyone would, but suggested that small businesses and schools might.

Knowing that demand was very strong for the US$795 Altair—which cost more than $1,000 with a monitor—Leininger suggested that Radio Shack could sell 50,000 computers,[17][13] but no one else believed him; Roach called the figure "horseshit", as the company had never sold that many of anything at that price.

[22][21][19][23][24][20][25][26][17][12][6][27][28] [excessive citations] A front-page Associated Press article discussed the novelty of a large consumer-electronics company selling a home computer that could "do a payroll for up to 15 people in a small business, teach children mathematics, store your favorite recipes or keep track of an investment portfolio.

Six sacks of mail arrived at Tandy headquarters asking about the computer, over 15,000 people called to purchase a TRS-80—paralyzing the company switchboard—and 250,000 joined the waiting list with a $100 deposit.

[29] Kornfeld stated when announcing the TRS-80, "This device is inevitably in the future of everyone in the civilized world—in some way—now and so far as ahead as one can think", and Tandy's 1977 annual report called the computer "probably the most important product we've ever built in a company factory".

[44] Selling computers did not change the company's "schlocky" image; the Radio Shack name embarrassed business customers, and Tandy executives disliked the "Trash-80" nickname for its products.

After some exhibitors at the 1979 Northeast Computer Show were forced to clarify that their products bearing the TRS-80 name were not affiliated with Radio Shack, publications and advertisers briefly began to use "S-80" generically rather than "TRS-80" under scare of legal action, though this never materialized.

Tandy cited one of the main reasons as being the prohibitive cost of redesigning it to meet stricter FCC regulations covering the significant levels of radio-frequency interference emitted by the original design.

[48] Radio Shack offered upgrades (double-density floppy controller, LDOS, memory, reliable keyboard with numeric keypad, lowercase, Level II, RS-232C) as late as its 1984 catalog.

[51] Dirt, cigarette smoke, or other contamination enters the unsealed key switches, causing electrical noise that the computer detects as multiple presses.

The bus arbitration logic blocks video display refresh (video-RAM reads) during CPU writes to the VRAM, causing a short black line.

Although the modification needs to be disabled for Level II BASIC, its design became the industry standard and was widely sold in kit form,[59] along with an eighth 2102 chip.

The E/I connects to the CPU/keyboard with a 6-inch ribbon cable which is unshielded against RF interference and its card edge connector tends to oxidize due to its base metal contacts.

Early TRSDOS neglects the required yet undocumented wait period, and thus false status often returns to the OS, generating random errors and crashes.

The magazine added, "Sadly, too, as with some other Radio Shack programs, the instructions seem to assume that the reader is either a child or an adult with the mentality of a slightly premature corned beef".

[83][43][84][81][85][13] Green stated in 1980 that although "there are more programs for the 80 than for all other systems combined" because of the computer's large market share, "Radio Shack can't advertise this because they are trying as hard as they can to keep this fact a secret from their customers.

[86][87] Broderbund, founded that year, began by publishing TRS-80 software, but by 1983 cofounder Doug Carlston said that the computer "turned out to be a terrible market because most of the distribution networks were closed, even though there were plenty of machines out there".

[42] An author wrote in a 1979 article on the computer's "mystery of machine language graphics control" that "Radio Shack seems to hide the neat little jewels of information a hobbyist needs to make a treasure of the TRS-80".

He stated that other than the "excellent" Level I BASIC manual "there has been little information until recently ... TRS-80 owners must be resourceful", reporting that the computer's "keyboard, video, and cassette" functionality were also undocumented.

[92] A full suite of office applications became available from the company and others, including the VisiCalc and Multiplan spreadsheets and the Lazy Writer, Electric Pencil, and from Radio Shack itself the Scripsit and SuperScripsit word processors.

Numerous alternative DOSes appeared, the most prominent being LDOS because Radio Shack licensed it from Logical Systems and adopted it as its official DOS for its Models I and III hard disk drive products.

It is a derivative of LDOS, enhanced to allow for the new Model 4 hardware such as its all-RAM architecture (no ROM), external 32 KB memory banks, bigger screen and keyboard, and featured new utilities such as a ram disk and a printer spooler.

Marketing director Ed Juge explained that their designers considered changing from the Model I's 64-column by 16-row video screen layout, but that they ultimately decided that maintaining compatibility was most important.

Although mostly intended as a disk-based computer, the Model III was available in a base cassette configuration with no disk hardware and only 16 KB of RAM with Level II BASIC.

Manufactured by Kyocera, the Model 100 features an LCD with 8 lines of 40 characters each, 8 kilobytes of RAM (expandable to 32KB), and is powered by AA cell batteries (or a plug-in adapter).