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Useful Notes / TRS-80

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Model I in its original bare-bones configuration. Data storage was via the cassette tape recorder. Graphics shown are maximum resolution.

The TRS-80 (short for Tandy Radio Shack Z-80) was Radio Shack's entry into the consumer microcomputer market; introduced in 1977, it was soon outselling the Apple ][ and Commodore PET. The first version offered, known as the Model I, had a black-and-white display with character mode graphics, and could not support a disk drive or more than 16K of memory without adding on a special "expansion interface" that normally sat beneath the monitor. It had no sound hardware, though games managed to produce sound effects by manipulating the cassette port with some sort of speaker plugged in.

Since the keyboard was built into the CPU cabinet — indeed, in the case of the Model I, the keyboard was the CPU cabinet — it was impossible to change out your keyboard if it went bad. This made the keyboard's susceptibility to "keybounce" paarticcullarlllly annnnoyyyingg.note  This and other "features", such as abysmally low-resolution graphics, led to the derisive nickname of "TRaSh-80"— which some fans have since reclaimed as a term of affection.

Tandy also capitalized on the TRS-80 brand name by using it to promote other, incompatible computers; the most popular of these were the TRS-80 Color Computer and the TRS-80 Model 100 Portable Computer (a battery-powered LCD-screen laptop).

This platform was the birthplace of the first home computer Interactive Fiction game, Scott Adams' Adventureland. It was also the first PC to which Infocom ported Zork, which had previously lived on Mainframes and Minicomputers.


Model I

  • Z80 CPU running at 1.77 MHz
  • CPU inside keyboard
  • Maximum of 16K RAM without the expansion interface, 48K with.
  • Level I BASIC, which fit entirely within 4K of ROM, capable of loading in data and programs off cassette at 250 bits per second.
  • Level II BASIC, capable of loading in data and programs off cassette at a (then) blistering 500 bits per second.
  • 64 x 16 character display.
  • Uppercase characters only. (A conversion chipset for lowercase letters came out a couple years after the Model I's introduction, but even then you had to install a hard switch so that you could disable lowercase for applications that didn't work well with it.)
  • 128x48 monochrome graphics implemented with special upper-ASCII graphics characters (6 giant rectangular pixels per character)
  • Add-on 5.25" floppy drives, available if the unit had an Expansion Interface installed.
  • "Supported" audio output, in the sense that software could ask the user to plug the cassette tape drive plug into a speaker when not loading data.

Model II

  • Z80 CPU running at 4 MHz
  • Built-in 8" (yes, eight-inch) floppy drive.
  • 80 x 25 character display.
  • Never terribly popular, as its internal memory map was not software-compatible with the Model I.

Model III

  • Basically, a Model I with an expansion interface and (optional) floppy drives built into the cabinet.
  • Slightly different ROM, though.
  • Native support for lowercase letters.
  • Could load data from cassette tape at a mind-numbing 1500 bits per second.
  • Mostly, but not entirely, software-compatible with the Model I.
  • Since the video display took its power from the same power supply as the floppy drives, the image on the display could noticeably shrink during disk access.

Model 4

  • Successor to the Model III. Backward compatible.
  • Had an optional "high resolution" monochrome graphics mode of up to 640x240 pixels, if you added hardware.

Model 12

  • Follow-on to the Model II.
  • Had "slim-line" half-height 8 inch floppy drives, instead of the one ginormous floppy drive of the Model II.

Model 16

  • Follow-on to the Model II.
  • Kept the Z80 CPU as an I/O processor only.
  • Main CPU was a 6 MHz 16-bit — yes, 16-bit! — Motorola 68000, the same CPU that would later appear in the Apple Macintosh. The 68000/Z80 pair would also appear in the Sega Genesis, Neo Geo, and several arcade boards.

Model 100

Model 102

Model 200

Pocket Computer



Original to the TRS-80

Ported, Cloned, or Concurrently Developed

  • The Eliminator (Defender clone)
  • Frogger
  • Brøderbund Software's Galactic saga, consisting of Galactic Empire, Galactic Trader, and Galactic Revolutionnote 
  • Galaxy Invasion (Galaxian clone)
  • Penetrator (another Defender clone, get your mind out of the gutter)




  • In Ready Player One, a TRS-80 is an important Plot Coupon.
  • In The Killing Star, to prevent alien signals from infecting them with a computer virus, the occupants of the "Cat" hook up their radio telescope to a TRS-80 with only 4K of RAM.

Live-Action TV

  • The iconic "Vicki's Birth" promotional image for Small Wonder shows Tiffany Brissette emerging from the screen of a TRS-80.
  • On the 4 April 2013 episode of The Daily Show, when describing the abysmal state of technology in the Veterans' Administration, Jon Stewart pointed out that a recommendation was made all the way back in 1982 to computerize their data. "Somewhere in a basement there's a guy hammering away on a TRS-80. And he's almost there."


  • MC Frontalot waxes nostalgic about this computer in his song "It Is Pitch Dark", already a love letter to old text-based adventures such as Zork:
    Did I battle a snake? Was the treasure intact?
    Or did the TRS-80 in my brain get hacked?
    Thanks, grandpa, for buying it; now my life's ruined
    Twenty-two years later, headís infested: got the grue in

Video Games

  • In Vampire: The Masquerade - Bloodlines the hacker Mitnick accuses an incompetent rival of using a "Trash-80" to run encryption, before stating that "incompetence always brings out the asshole in me."

Web Comics