-# How keys are registered, and interpreted by computers
+# How Keys Are Registered, and Interpreted by Computers
In this file, you can will learn the concepts of how keyboards work over USB,
and you'll be able to better understand what you can expect from changing your
firmware directly.
-## Schematic view
+## Schematic View
Whenever you type on 1 particular key, here is the chain of actions taking
place:
## 2. What the Firmware Sends
-The [HID specification](http://www.usb.org/developers/hidpage/Hut1_12v2.pdf) tells what a keyboard can actually send through USB to have a chance to be properly recognised. This includes a pre-defined list of scancodes which are simple numbers from `0x00` to `0xE7`. The firmware assigns a scancode to each key of the keyboard.
+The [HID specification](https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf) tells what a keyboard can actually send through USB to have a chance to be properly recognised. This includes a pre-defined list of scancodes which are simple numbers from `0x00` to `0xE7`. The firmware assigns a scancode to each key of the keyboard.
-The firmware does not send actually letters or characters, but only scancodes.
-Thus, by modifying the firmware, you only can modify what scancode is sent over
+The firmware does not send actual letters or characters, but only scancodes.
+Thus, by modifying the firmware, you can only modify what scancode is sent over
USB for a given key.
## 3. What the Operating System Does
Once the keycode reaches the operating system, a piece of software has to have
it match an actual character thanks to a keyboard layout. For example, if your
-layout is set to QWERTY, a sample of the matching table is as follow:
+layout is set to QWERTY, a sample of the matching table is as follows:
| keycode | character |
|---------|-----------|
| 0x1D | z/Z |
| ... | ... |
-## Back to the firmware
+## Back to the Firmware
As the layout is generally fixed (unless you create your own), the firmware can actually call a keycode by its layout name directly to ease things for you. This is exactly what is done here with `KC_A` actually representing `0x04` in QWERTY. The full list can be found in [keycodes](keycodes.md).
## List of Characters You Can Send
-Putting aside shortcuts, having a limited set of keycodes mapped to a limited layout means that **the list of characters you can assign to a given key only is the ones present in the layout**.
+Putting aside shortcuts, having a limited set of keycodes mapped to a limited layout means that **the list of characters you can assign to a given key are only the ones present in the layout**.
-For example, this means that if you have a QWERTY US layout, and you want to assign 1 key to produce `€` (euro currency symbol), you are unable to do so, because the QWERTY US layout does not have such mapping. You could fix that by using a QWERTY UK layout, or a QWERTY US International.
+For example, this means that if you have a QWERTY US layout, and you want to assign one key to produce `€` (euro currency symbol), you are unable to do so, because the QWERTY US layout does not have such mapping. You could fix that by using a QWERTY UK layout, or a QWERTY US International.
-You may wonder why a keyboard layout containing all of Unicode is not devised then? The limited number of keycode available through USB simply disallow such a thing.
+You may wonder why a keyboard layout containing all of Unicode is not devised then? The limited number of keycodes available through USB simply disallows such a thing.
## How to (Maybe) Enter Unicode Characters