'===========================================================================
' Subject: QB SIMULTANEOUS KEY               Date: Unknown Date (00:00)   
' Author:  Brent Ashley                      Code: ASM, QB, PDS           
' Keys:    QB,SIMULTANEOUS,KEY             Packet: KEYBOARD.ABC
'===========================================================================
'BASIC test code:
DECLARE FUNCTION KeyPressed%(ScanCode%)
CALL InstKeyPress ' install resident code
CLS
DO
  LOCATE 1,1
  FOR i% = 2 TO 9 ' scancode of 1 to 8
    IF KeyPressed(i%) THEN PRINT CHR$(47+i%); ELSE PRINT " ";
  NEXT
  PRINT
LOOP UNTIL INKEY$=CHR$(27) ' escape to quit
CALL UnHookKeyPress ' unhook resident code - IMPORTANT!!!
END

; KeyPress.ASM by Brent Ashley
;   checks the "pressed" status of any key
.model medium, basic
.code
Old09        Label Dword       ;Label for to old Int 09h handler
Old09Offset  dw ?              ;Offset part
Old09Segment dw ?              ;Segment part
Hooked       db 0              ;Our installed flag
KeyMap       db 80 dup(0)      ;map of kybd, one byte per scancode
InstKeyPress proc uses ds ax dx ; From BASIC: CALL InstKeyPress
                               ; REMEMBER to call UnhookKeyPress!
        cmp cs:Hooked,0        ;Are we already hooked?
        jnz InstallExit        ;If so, exit
        mov ax,3509h           ;Get current vector for int 09h
        int 21h
        mov cs:Old09Segment,es ;Remember it for later
        mov cs:Old09Offset,bx
        mov ax,2509h
        push ds
        push cs
        pop ds                 ;Point int 09h handler to our code
        mov dx, offset OurInt09
        int 21h
        pop ds
        mov cs:Hooked,-1       ;Set our installed flag
InstallExit:
        ret
OurInt09:                      ;Our Int 09h handler
        push ax
        push bx
        push dx
        push si
        in al, 60h
        test al, 080h          ;is "released" bit set?
        jnz Released           ;yup - go to it
        mov dl, 0FFh           ;nope - set key pressed flag
        jmp PutFlag
Released:
        and al, 07Fh           ;yes - clear bit for index
        mov dl, 0              ;and set flag for release
PutFlag:
        xor ah, ah
        mov si, ax             ;assign index
        mov cs:KeyMap[si], dl  ;put flag in place
        pop si
        pop dx
        pop bx
        pop ax
Continue:
        jmp dword ptr cs:[Old09];Transfer ctrl to orig Int 09h
InstKeyPress endp
KeyPressed proc uses bx si, ScanCode:WORD
        ; from BASIC: TrueOrFalse% = KeyPressed(ScanCode%)
        mov bx, ScanCode       ;get scan code addr
        mov si, [bx]           ;load value as index
        mov al, cs:KeyMap[si]  ;put flag in al
        cbw                    ;convert to word for integer value
        ret
KeyPressed endp
UnhookKeyPress proc            ; from BASIC: CALL UnHookKeyPress
        cmp cs:Hooked,0        ; are we installed?
        jz UnHooked            ; nope - exit
        push ax
        push ds
        mov ax,2509h           ;Unhook ourself
        mov ds,Old09Segment
        mov dx,Old09Offset
        int 21h                ;Point Int 09h back to orig hndlr
        pop ds
        pop ax
        mov cs:Hooked,0        ;Set installed flag back to zero
UnHooked:
        ret
UnhookKeyPress endp
END