第一次来晒一晒作业代码哈~

assume cs:code,ds:data

data segment
        db "Beginner's All-purpose Symbolic Instruction Code.",0
data ends

code segment
begin:
        mov ax,data
        mov ds,ax
        mov si,0
        call letterc
        
        mov ax,4c00h
        int 21h
        
letterc:
        pushf                        ;保护现场
        pusha                        ;保护所有寄存器
        mov cx,[si]
        jcxz ok                        ;cx=0则结束
        mov al,[si]                ;传到al中
        cmp al,61h                ;与61(a)比较
        jb s0                        ;若小于a 则跳至s0
        cmp al,7Ah                ;与7A(z)比较
        ja s0                        ;若大于z 则跳至s0
        sub al,20h                ;小写转大写(and al,11011111B)
        mov [si],al

 s0:
        inc si
        loop letterc
        
 ok:
        popa
        popf
        ret
        
code ends
end begin