;名称：letterc
;功能：将以0结尾的字符串中的小写字母转变成大写字母
;参数：ds:si指向字符串首地址
;应用举例：
assume cs codesg
datasg segment
db "Beginner's All-purpose Symbolic Instruction Code.",0
datasg ends
codesg segment
begin: mov ax,datasg
mov ds,ax
mov si,0
call letterc
mov ax,4c00H
int 21H
letterc:
s0: mov cl,ds:[si]
mov ch,0
jcxz ok_letterc
cmp cl,61H
jb s1
cmp cl,7aH
ja s1
and cl,11011111B
mov ds:[si],cl
inc si
loop s0
s1: inc si
loop s0
ok_letterc:
ret
codese ends
end begin |
