HelenOS sources
KC_N4 129 uspace/drv/hid/adb-kbd/ctl.c [0x56] = KC_N4,
KC_N4 153 uspace/drv/hid/atkbd/atkbd.c [0x6b] = KC_N4,
KC_N4 142 uspace/drv/hid/usbhid/kbd/conv.c [0x5c] = KC_N4,
KC_N4 146 uspace/drv/hid/xtkbd/xtkbd.c [0x4b] = KC_N4,
KC_N4 189 uspace/srv/hid/input/ctl/sun.c [0x5b] = KC_N4,
KC_N4 187 uspace/srv/hid/input/layout/ar.c [KC_N4] = '4',
KC_N4 216 uspace/srv/hid/input/layout/cz.c [KC_N4] = '4',
KC_N4 195 uspace/srv/hid/input/layout/fr_azerty.c [KC_N4] = '4',
KC_N4 196 uspace/srv/hid/input/layout/us_dvorak.c [KC_N4] = '4',
KC_N4 190 uspace/srv/hid/input/layout/us_qwerty.c [KC_N4] = '4',
HelenOS homepage, sources at GitHub