汇编 水题

data segment
output db 'Hello world! $'
data ends
code segment

start:
assume ds:data,cs:code
mov ax,data
mov ds,ax

mov dx,offset output
mov ah,09h
int 21h

mov ah,4ch
int 21h

code ends
end start
小写字母转大写字母

stack segment stack
db 1024 dup (?)
stack ends

data segment
data ends

code segment
assume ds:data,cs:code,ss:stack

start:  mov ax,data
mov ds,ax
getkey: mov ah, 01h
int 21h
cmp al, 'a'
jb getkey
cmp al, 'z'
ja getkey

sub al, 20h
mov ah, 02h
mov dl, al
int 21h

mov ah,4ch
int 21h

code ends
end start