大小字母写转换.docx

文档介绍：大小字母写转换
CODES SEGMENT
ASSUME CS:CODES
START:
mov ah,01h ;键入字符
int 21h ;申请dos调用
cmp al,03h ;比较字符是不是a到z
jz exit ;不是的话跳出
cmp al,'a'
jb START
cmp al,'z'
ja START
sub al,20h
mov dl,al
mov ah,02h
int 21h
jmp start
exit:
MOV AH,4CH
INT 21H
CODES ENDS
END START
响铃
CODES SEGMENT
ASSUME CS:CODES
START:
mov ah,01h
int 21h
cmp al,03h
jz exit
sub al,1
jb START
sub al,9
ja START
sub al,30h
mov cl,al
bell: mov dl,01h
mov ah,02h
int 21h
dec cl
jnz bell
jmp start
exit:
MOV AH,4CH
INT 21H
CODES ENDS
END START