ASM

 ; sample03
; illustrates setting of BIOS variable
; clears the NUMLock, CAPSLock, SCROLLLock flags
DOSSEG
.MODEL SMALL
.STACK

.DATA
aString db 'Lock keys reset !',13,10,'$'

.CODE
ProgramStart:
mov ax,SEG _DATA ; set data segment
mov ds,ax

mov ax,0040h ; set ES to point to BIOS Data Area
mov es,ax
mov byte ptr es:[0017h],0 ; reset keyboard flags

mov ah,09h ; output message
mov dx,OFFSET aString
int 21h

mov ah,4ch ; terminate program
int 21h
END ProgramStart