cseg     segment
         assume    cs:cseg
         org       100h
first:   jmp       init
hotkey   equ       30h                 ;Scan code for "B"
shftmsk  equ       00001000b           ;Shift mask
old8     label     word
oldloc8  dd        ?
old9     label     word
oldloc9  dd        ?
count    db        0

newint9  proc      near
         push      ax
         in        al,60h
         cmp       al,hotkey
         je        keygood
exit9:
         pop       ax
         jmp       oldloc9
keygood:
         mov       ah,2
         int       16h
         test      al,shftmsk
         jz        exit9
         inc       count
         jmp       exit9
newint9  endp

newint8  proc      near
         cmp       count,0
         je        exit8
         push      ax
         push      bx
         push      cx
         push      dx
         xor       cx,cx
         xor       dx,dx
         mov       ah,1
         int       1ah
         inc       count
         cmp       count,60h
         jne       all_done
         mov       count,0
all_done:pop       dx
         pop       cx
         pop       bx
         pop       ax
exit8:
         jmp      oldloc8
newint8  endp

init     proc      near
         mov       ax,3508h
         int       21h
         mov       old8,bx
         mov       old8[2],es
         mov       ax,3509h
         int       21h
         mov       old9,bx
         mov       old9[2],es
         mov       ax,2508h
         lea       dx,newint8
         int       21h
         mov       ax,2509h
         lea       dx,newint9
         int       21h
         mov       ax,ds:[2ch]
         mov       es,ax
         mov       ah,49h
         int       21h
         lea       dx,init
         int       27h
init     endp
cseg     ends
         end       first