bit 2: SysReq key (currently down if 1)
bit 1: Left alt key (currently down if 1)
bit 0: Left ctrl key (currently down if 1)
BIOS uses this to compute the ASCII code for an alt-Keypad sequence.
Offset of start of keyboard buffer (1Eh). Note: this variable is not supported on
many systems, be careful if you use it.
Offset of end of keyboard buffer (3Eh). See the note above.
Miscellaneous keyboard flags.
Byte 40:19 AltKpd
Word 40:80 BufStart
Word 40:82 BufEnd
bit 7: Read of keyboard ID in progress
bit 6: Last char is first kbd ID character
bit 5: Force numlock on reset
Byte 40:96 KbdFlags3
bit 4: 1 if 101-key kbd, 0 if 83/84 key kbd.
bit 3: Right alt key pressed if 1
bit 2: Right ctrl key pressed if 1
bit 1: Last scan code was E0h
bit 0: Last scan code was E1h
More miscellaneous keyboard flags.
bit 7: Keyboard transmit error
bit 6: Mode indicator update
bit 5: Resend receive flag
Byte 40:97 KbdFlags4
bit 4: Acknowledge received
bit 3: Must always be zero
bit 2: Capslock LED (1=on)
bit 1: Numlock LED (1=on)
bit 0: Scroll lock LED (1=on)
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