将前4个转化为大写

;******************
;将前4个转化为大写
;
;******************
assume cs:code,ds:data,ss:stack

data segment
    db '1. display      '
    db '2. brows        '
    db '3. replace      '
    db '4. modify       '
data ends

stack segment
    dw 0,0,0,0,0,0,0,0
stack ends

code segment
  start:mov ax,data
    mov ds,ax
    mov bx,3
    mov si,0
    mov ax,stack
    mov ss,ax
    mov sp,10h    ;以上为初始化工作

    mov cx,4
 s:push cx
    mov cx,4
 s0:mov al,[bx+si]
    and al,11011111b
    mov [bx+si],al
    inc si
    loop s0
    add bx,12
    pop cx
    loop s

    mov ax,4c00h
    int 21h        
code ends
end start