Bitfields for MS-DOS v6.22 KEYB flags B:
Bit(s)	Description	)
 15	INT 16/AH=1xh supported (INT 16h/AH=92h call returns AH<=80h)
	if clear, extended keyboard scan codes are immediately discarded
 14	INT 16/AH=2xh supported (INT 16h/AH=A2h call returns AH<=80h)
 13	unused (0)
 12	network installed (INT 2F/AX=B800h)
 11	original IBM PC (BIOS date 1981)
 10	PC or PC/XT (BIOS machine type byte of FBh or FEh)
 9	PC Convertible (BIOS machine type byte of F9h); use INT 15/AX=4104h
 8	unused (0)
 7	IBM PS/2 model 30 (BIOS machine type byte of FAh)
 6	IBM AT (BIOS machine type FCh)
 5	IBM PS/2 (BIOS machine type F8h)
 4	PS/2 and unknown only: non-standard 8042 reported by INT 15/AH=C0h
	=1: after keyboard self test resulting AAh, INT 09 handler will (re)set
	      keyboard code-set 1 and temporarily disable a PS/2 mouseport.
 3	temporary flag???
 2-0	???
SeeAlso: #02972,#02973