A routine called I16Clip is called by Int 16h, services 00h,01h,10h,11h,13h and 14h. This routine acts to "filter" certain keycodes and translate others. If the service is 00h or 01h, keycodes will be discarded which satisfy either "AH > 84h" or "AH#0 AND AL=F0h". If the service is 10h,11h,13h, or 14h and the keycode satisfies "AH#0 AND AL=F0h" then AL will be reset to 00h.