编写一个汇编程序，要求对键盘输入的大写字母用小写字母显示出来…

assume ds:datasg, cs:code
datasg segment
db "Beginner's All-purpose Symbolic Instruction Code.",0
datasg ends

code segment
begin:
mov ax, datasg
mov ds, ax
mov si, 0
call letterc

mov ax, 4c00h
int 21h

letterc:
mov cl, byte ptr ds:[si]
jcxz back
cmp cl, 61h
jna s ;用于判断是否在A~Z之间
cmp cl, 7ah
jnb s
or byte ptr ds:[si], 11111111b
s:
inc si
jmp short letterc
back:ret
code ends
end begin

抱歉没留意到你说要键盘输入。。。。本回答被提问者和网友采纳

var s:string; i:longint;
begin
readln(s);
for i:=1 to length(s) do s[i]:=chr(ord(s[i])-ord('A')+ord('a'));
writeln(s);
end.