[汇编] 从键盘输入一个一位数字，然后响铃n声

; multi-segment executable file template.

data segment

ends

stack segment
    dw   128  dup(0)
ends

code segment
start:
; set segment registers:
    mov ax, data
    mov ds, ax
    mov es, ax

    ; add your code here 
    BEGIN:        
    MOV    AH, 1            ;从键盘输入一个字符的DOS调用AL存放输入的字符
    INT        21H
    SUB        AL, '0'     ;输入的是字符需要转化为数字
    JB        STOP                    ;输入字符<'0'吗？;below
    CMP    AL, 9                         ;输入字符>'9'吗？;above
    JA        STOP
    CBW                             ;AL扩展到AH
    MOV    CX, AX                        ;响铃次数N
    JCXZ    STOP
        BELL:        
        MOV    DL, 07H                    ;准备响铃
        MOV    AH, 2                    ;显示一个字符的DOS调用，实际为响铃
        INT        21H
        LOOP    BELL
    STOP:        RET

    ; wait for any key....    
    mov ah, 1
    int 21h
    
    mov ax, 4c00h ; exit to operating system.
    int 21h    
ends

end start ; set entry point and stop the assembler.