Lesson plan

Scancode

Broadly speaking, a scancode (or scan code) is either a number or bit array that is used by a keyboard protocol to uniquely identify a keyboard key. Keyboards normally send scancodes to the computer to update the computer's internal keyboard state (which tracks what keys are being held down). The exact mechanism how, when and what scancodes are sent depends on the protocol. A keyboard protocol may use other means to update the computer's internal keyboard state, such as sending a bitmap that encodes the state of keys (pressed/released). This is partially the case for a keyboard using the HID protocol when the Boot Protocol is selected. It will send the states of modifier keys encoded in a bitmap (where each bit represents a key state) alongside a scancode array of pressed keys (excluding modifier keys).

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Article summary

Broadly speaking, a scancode (or scan code) is either a number or bit array that is used by a keyboard protocol to uniquely identify a keyboard key. Keyboards normally send scancodes to the computer to update the computer's internal keyboard state (which tracks what keys are being held down). The exact mechanism how, when and what scancodes are sent depends on the protocol. A keyboard protocol may use other means to update the computer's internal keyboard state, such as sending a bitmap that encodes the state of keys (pressed/released). This is partially the case for a keyboard using the HID protocol when the Boot Protocol is selected. It will send the states of modifier keys encoded in a bitmap (where each bit represents a key state) alongside a scancode array of pressed keys (excluding modifier keys).

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Discussion questions

  1. Summarise the article in your own words. Which single claim would you verify first, and why?
  2. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
  3. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

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Key claims and bibliography are generated from the same tracked claims and sources as the article page.