大小写转换

data segment
quit db "your put wrong num press any key to exit......",13,10,'$'
data ends
extra segment
max db 'z'
min db 'a'
extra ends
code segment
assume cs:code,ds:data,es:extra
start:
input:
mov ax,data
mov ds,ax
mov ax,extra
mov es,ax
mov ah,01h
int 21h
lea di,min
scas min
jb exit
ja judgez

exit: mov ah,9
lea dx,quit
int 21h

judgez:
lea di,max
scas max
ja exit
jb amend
amend:
sub al,20h
mov dx,ax
mov ah,2h
int 21h
mov ah,4ch
int 21h
code ends
end start