assume cs:code
data segment
str db "Beginner's All-purpose Symbolic Insturnction Code.",0,'$'
data ends
code segment
letterc:
push si ；保存si
s0: mov al,[si]
cmp al,0
jz done ；为零结束
cmp al,61h ；如果≥a
jge s1 ；则转至s1
inc si ；否则返回继续下一字符
jmp s0 ；
s1: cmp al,7ah ；如果≤z
jle s2 ；则开始转换
s2: sub al,20h ；减20h得到大写字母
mov [si],al
inc si
loop s0
done: pop si ；恢复si
ret
;
start:
mov ax,data
mov ds,ax
mov si,0
call letterc
；输出验证一下
mov dx,offset str
mov ah,09h
int 21h
；
mov ah,4ch
int 21h
code ends
end start
d:\asm> |
