INT 16h AH=10h / 11h: enhanced keyboard read and check — 8086 assembly guide

The enhanced versions of 00h and 01h: the same results, but F11, F12 and the grey keys of a 101-key keyboard come through unchanged.

Function 10h works like INT 16h AH=00h (wait for a key, take it, return AL = ASCII and AH = scan code) and 11h like INT 16h AH=01h (ZF = 1 if no key, otherwise AX = the next key, left in the buffer). The difference is what they do with the keys the 101-key keyboard added. The keyboard handler stores those with markers that 00h and 01h remove or filter out for the sake of programs written for the 84-key keyboard; 10h and 11h return them as stored.

Key	AH=10h / 11h	AH=00h / 01h
Up, keypad (Num Lock off)	4800h	4800h
Up, grey arrow block	48E0h	4800h
Enter, keypad	E00Dh	1C0Dh
/ on the keypad	E02Fh	352Fh
F11 / F12	8500h / 8600h	dropped
Alt+Up, Ctrl+Up, other new combinations	reported	dropped

E0h in AL marks a grey key; E0h in AH marks a key on the numeric keypad that has a twin in the main block. A program that does not care which copy was pressed treats AL = E0h like AL = 0. The example stores a grey Up and F11, reads them with the enhanced functions, then reads a grey Up the old way:

prints: 48E0 48E0 8500 4800

MOV     AH, 05h
MOV     CX, 48E0h     ; the grey Up arrow: scan 48h, E0h for "grey"
INT     16h
MOV     AH, 05h
MOV     CX, 8500h     ; F11: scan 85h
INT     16h
MOV     AH, 11h       ; enhanced check: is a key waiting?
INT     16h           ; ZF = 0, AX = 48E0h, left in the buffer
CALL    PHEX4
MOV     DL, " "
MOV     AH, 02h       ; DOS: print the character in DL
INT     21h
MOV     AH, 10h       ; enhanced read
INT     16h           ; 48E0h
CALL    PHEX4
MOV     DL, " "
MOV     AH, 02h       ; DOS: print the character in DL
INT     21h
MOV     AH, 10h
INT     16h           ; 8500h: F11
CALL    PHEX4
MOV     DL, " "
MOV     AH, 02h       ; DOS: print the character in DL
INT     21h
MOV     AH, 05h       ; the grey arrow once more...
MOV     CX, 48E0h
INT     16h
MOV     AH, 00h       ; ...read the old way
INT     16h           ; 4800h: it looks like the keypad arrow
CALL    PHEX4
 
PHEX4   PROC    NEAR  ; print AX as four hex digits; keeps every register
PUSH    AX
MOV     AL, AH
CALL    PHEX2         ; the high byte first
POP     AX
CALL    PHEX2         ; then the low byte
RET
PHEX4   ENDP
PHEX2   PROC    NEAR  ; print AL as two hex digits; keeps every register
PUSH    AX
PUSH    CX
PUSH    DX
MOV     DH, AL        ; keep the byte
MOV     CL, 4
SHR     AL, CL        ; the high nibble
CALL    HEXN1
MOV     AL, DH
AND     AL, 0Fh       ; the low nibble
CALL    HEXN1
POP     DX
POP     CX
POP     AX
RET
HEXN1:
ADD     AL, "0"
CMP     AL, "9"
JBE     HEXN2
ADD     AL, 7         ; past "9": "A".."F"
HEXN2:
MOV     DL, AL
MOV     AH, 02h
INT     21h
RET
PHEX2   ENDP

Which to use

On any machine with an enhanced keyboard BIOS (bit 4 of 0040:0096h set, every AT-class PC from the late 1980s, and DOSBox-X) prefer 10h/11h and decide yourself what a grey key means. On an older BIOS these function numbers do nothing useful, so careful programs check that bit first. Do not mix the families on the same keys: 01h removes F11 from the buffer when it sees it, so an 01h check followed by a 10h read can wait for a key that 01h has already thrown away. The matching shift-flag function is INT 16h AH=12h.