;this program waits for user input. if the user presses '1' it outputs a string, if '2' it exits
.model small
.stack 100h
.data

oneKey = 2
escKey = 3
key1 db 'Key 1 $'

.code      
init:   mov ax,@data       ;initialize data sector
        mov ds,ax
        mov ax,3           ;initialize video mode: text
        int 10h
        
top:    in al,64h          ;check port 64 - do nothing
        AND al,1           ;if no keys are pressed
        cmp al,1        
        jne top
        
        in al,60h          ;read in key pressed
        cmp al,escKey      
        je fin
        
        cmp al,oneKey      ;compare with a specific key
        jne top
        
        lea dx,key1        ;print out key1
        mov ah,9           ;
        int 21h            ;
        
        jmp top
fin:
mov ah,4ch                ;return control to OS
    int 21h
end