Editing TRS-80 (section)

=== Keyboard ===
[[File:Radio Shack Tandy TRS-80 Model I Keyboard.JPG|thumb|Tandy/Radio Shack TRS{{nbhyph}}80 Model&nbsp;I Alps keyboard PCB]]

The TRS-80 Model I keyboard uses mechanical switches that suffer from "[[Contact bounce|keyboard bounce]]", resulting in multiple letters being typed per keystroke.<ref name="hoganm319810831">{{cite magazine |url=https://books.google.com/books?id=rD0EAAAAMBAJ&pg=PA35 |title=The Radio Shack TRS-80 Model III Computer |access-date=February 28, 2011 |author=Hogan, Thom |date=August 31, 1981 |magazine=[[InfoWorld]] |volume=3 |number=17 |pages=35–37}}</ref> The problem was described in [[Wayne Green]]'s editorial in the first issue of ''[[80&nbsp;Micro]]''.<ref name="green198001">{{cite news |url=https://archive.org/stream/80-microcomputing-magazine-1980-01/80Microcomputing_0180#page/n7/mode/2up |title=Where We're Coming From / Where We're Bound |work=[[80 Micro]] |date=January 1980 |access-date=October 17, 2013 |author=Green, Wayne |author-link=Wayne Green|pages=8}}</ref> Dirt, [[cigarette smoke]], or other contamination enters the unsealed key switches, causing [[electrical noise]] that the computer detects as multiple presses. The key switches can be cleaned, but the bounce recurs when the keyboard is reexposed to the contaminating environment.<ref name="reedkeybounce">{{Cite web |url=http://www.trs-80.org/model-1-keybounce/ |title=Model I Keybounce |last=Reed |first=Matthew |website=TRS-80.org |access-date=2019-05-20}}</ref>

Keyboard bounce only occurs in Model I computers with Level&nbsp;II BASIC [[firmware]]; Level&nbsp;I BASIC has a "debounce" delay to the keyboard driver to avoid the noisy switch contacts. Tandy's {{code|KBFIX}} utility, the Model&nbsp;III, the last Model&nbsp;I firmware, and most third-party operating systems also implement the software fix, and Tandy changed the keyboard during the Model&nbsp;III's lifetime to an [[Alps Electric]] design with sealed switches. The Alps keyboard was available as an upgrade for the Model&nbsp;I for $79.{{r|reedkeybounce}}

The keyboard is [[memory-mapped I/O|memory-mapped]] so that certain locations in the processor's memory space correspond to the status of a group of keys.