Category: vendor-specific BIOS extensions
Flags: callout or callback (usually hooked rather than called)


	CF set
	AH = shift state (see #03247)
	AL = scan code (see #03214)
Return:	BX, CX, DI, ES may be destroyed
	various return methods are supported:
	    IRET, AX unchanged: process keystroke normally
	    IRET, AL = FFh: discard keystroke
	    IRET, AX changed: process modified keystroke
	    chain to old INT 5B: allow other handlers to look at (possibly
		  modified) keystroke in AX
	    RETF 2, CF clear: place returned AX into keyboard buffer without
		  any further processing
Notes:	invoked by the keyboard ISR, and used to remap the keyboard
	if CF is clear on entry, some other handler has processed the
	  keystroke and the current handler should not modify it, instead
	  performing a RETF 2 or IRET (after clearing CF on the stack)
	when requesting that a value be placed directly into the keyboard
	  buffer, AL and AH may not *both* be nonzero (the TI does not
	  return scan codes as part of the key code for non-extended keys)
SeeAlso: INT 15/AH=4Fh,INT 4A/AH=00h"TI",INT 59"TI Professional"
SeeAlso: INT 5C"TI Professional",INT 5D"TI Professional"
SeeAlso: INT 5E"TI Professional",INT 5F"TI Professional"