* **`default_layer_state`** indicates a base keymap layer (0-31) which is always valid and to be referred (the default layer).
* **`layer_state`** has current on/off status of each layer in its bits.
-Keymap layer '0' is usually `default_layer`, wither other layers initially off after booting up the firmware, although this can configured differently in `config.h`. It is useful to change `default_layer` when you completely switch a key layout, for example, if you want to switch to Colemak instead of Qwerty.
+Keymap layer '0' is usually the `default_layer`, with other layers initially off after booting up the firmware, although this can configured differently in `config.h`. It is useful to change `default_layer` when you completely switch a key layout, for example, if you want to switch to Colemak instead of Qwerty.
Initial state of Keymap Change base layout
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> This `fn_actions[]` interface is mostly for backward compatibility. In QMK, you don't need to use `fn_actions[]`. You can directly use `ACTION_FUNCTION(N)` or any other action code value itself normally generated by the macro in `keymaps[][MATRIX_ROWS][MATRIX_COLS]`. N in `F(N)` can only be 0 to 31. Use of the action code directly in `keymaps` unlocks this limitation.
+You can get a full list of Action Functions in [action_code.h](https://github.com/qmk/qmk_firmware/blob/master/tmk_core/common/action_code.h).
+
#### `action_function()`
To actually handle the keypress event we define an `action_function()`. This function will be called when the key is pressed, and then again when the key is released. We have to handle both situations within our code, as well as determining whether to send/release `KC_ESC` or `KC_GRAVE`.