求助，in al,60h为什么不起作用

assume cs:cc,ds:qwer
qwer segment
tip1 db 10,13,'please input char,cr then end:'
db 10,13,36
qwer ends
cc segment
beg:
mov ax,qwer
mov ds,ax
mov dx,offset tip1
mov ah,9
int 21h
getkey:
;mov ah,7
;int 21h
in al,60h
cmp al,13
je exit
mov dl,al
cmp dl,'0'
jb getkey
cmp dl,'9'
jbe disp
cmp dl,'a'
jb getkey
cmp al,'z'
jbe dispx
cmp dl,'a'
jb getkey
cmp dl,'z'
ja getkey
dispx:mov dl,'*'
disp:mov ah,2
int 21h
jmp getkey
exit:mov ah,4ch
int 21h
cc ends
end beg