INT 16 - AAKEYS - GET KEY-EVENT BUFFER                                          
	AX = 0603h
Return:	ES:BX -> 256-byte circular key-event buffer
	ES:[AX] = offset of head of buffer
	ES:[AX+1] = offset of tail of buffer
SeeAlso: AX=0600h,AX=0601h,AX=0602h,AX=0604h