EMZETT.Keyboard
Image: NotFromUtrecht, CC BY-SA 3.0, Wikimedia Commons
In short: An input device with individual keys for text entry and control — alongside the mouse, the most important input device of a computer.
In more detail: A distinction is made, among other things, between membrane keyboards (cheap, quiet) and mechanical keyboards (individual switch per key, defined tactile feel, more durable). Layouts differ by language/region (e.g. QWERTZ in Germany vs. QWERTY in English-speaking regions).
In Depth
Membrane vs. mechanical switches
With membrane keyboards, all keys press onto a shared, rubberised contact layer beneath the row of keys — cheap to manufacture, but with a comparatively imprecise, “mushy” actuation point and a limited lifespan (typically a few million keystrokes per key before the rubber layer degrades). Mechanical keyboards, by contrast, use a separate electromechanical switch for each key, with a clearly defined actuation point and considerably longer lifespan (often specified at 50-100 million keystrokes). Common switch types differ in sound and feedback: “linear” switches (e.g. Cherry MX Red) with no perceptible actuation bump, consistent resistance across the entire key travel — popular for gaming, where fast double-tapping matters; “tactile” switches (e.g. MX Brown) with a perceptible click resistance at actuation, but no sound — a compromise between typing feedback and office suitability; and “clicky” switches (e.g. MX Blue) with an additional audible click sound, popular among typing enthusiasts, but unsuitable for open-plan offices because of the noise.
Connection type and latency
Besides pure switch technology, keyboards also differ in connection type: classically wired (lowest, most consistent latency), wireless via Bluetooth (convenient, but slightly higher and more variable latency due to radio transmission and encryption), or via a dedicated 2.4 GHz radio dongle (usually lower latency than Bluetooth, since a dedicated, low-latency-optimised protocol is used instead of the more general Bluetooth standard — popular for gaming peripherals).
Anti-ghosting and N-key rollover
A technical detail that’s often overlooked: keyboards are internally wired as a matrix of rows and columns, not with a dedicated line per key (that would be an impractical amount of wiring for 100+ keys). If certain key combinations are pressed at the same time, this matrix wiring can, in rare cases, lead to “ghosting” — a key that isn’t pressed is incorrectly detected as pressed, because it sits at the intersection of two actually pressed keys in the matrix. Anti-ghosting circuits (additional diodes per key) prevent this for certain key combinations; N-key rollover goes further and guarantees that truly ANY combination of simultaneously pressed keys is correctly detected — important, for example, in gaming, where several movement and action keys are often held at once.
Layout differences
Physical keyboard layouts differ internationally not just in character assignment (QWERTZ vs. QWERTY vs. AZERTY in France), but sometimes also in the number and arrangement of the keys themselves — German keyboards, for example, have an extra key next to the left Shift key (for the <> character) that’s missing on US layouts, which makes switching layouts between countries not just a software question, but sometimes a hardware one too.
See also: Mouse