+- `KC_LCTL` and `KC_RCTL` for Control
+- `KC_LSFT` and `KC_RSFT` for Shift
+- `KC_LALT` and `KC_RALT` for Alt
+- `KC_LGUI` and `KC_RGUI` for Windows key or Command key in Mac
+
+#### 1.3 Fn key
+`KC_FNnn` are `Fn` keys which not given any action at the beginning unlike most of keycodes has its own action. To use these keys in `KEYMAP` you need to assign action you want at first. Action of `Fn` is defined in `fn_actions[]` and index of the array is identical with number part of `KC_FNnn`. Thus `KC_FN0` designates action defined in first element of the array. ***32 `Fn` keys can be defined at most.***
+
+#### 1.4 Mousekey
+- `KC_MS_U`, `KC_MS_D`, `KC_MS_L`, `KC_MS_R` for mouse cursor
+- `KC_WH_U`, `KC_WH_D`, `KC_WH_L`, `KC_WH_R` for mouse wheel
+- `KC_BTN1`, `KC_BTN2`, `KC_BTN3`, `KC_BTN4`, `KC_BTN5` for mouse buttons
+
+#### 1.5 System & Media key
+- `KC_PWR`, `KC_SLEP`, `KC_WAKE` for Power, Sleep, Wake
+- `KC_MUTE`, `KC_VOLU`, `KC_VOLD` for audio volume control
+- `KC_MNXT`, `KC_MPRV`, `KC_MSTP`, `KC_MPLY`, `KC_MSEL` for media control
+- `KC_MAIL`, `KC_CALC`, `KC_MYCM` for application launch
+- `KC_WSCH`, `KC_WHOM`, `KC_WBAK`, `KC_WFWD`, `KC_WSTP`, `KC_WREF`, `KC_WFAV` for web browser operation
+
+#### Keycode Table
+ See [keycode table](doc/keycode.txt) in `doc/keycode.txt` or `common/keycode.h` for the detail or other keycodes.