如何测试输入字符是否在1-9之间？

Question

我正在写一个8086汇编语言的程序，要求1-9之间的单个数字，然后存储它。如果它不在1-9之间，则应该循环回去。

什么是一种很好的方式来测试它，并让它循环回来（并允许你输入另一个数字），直到满足要求为止？

我迄今为止代码：

section .data 
    prompt1 db "Enter a single digit digit between 1-9 --> $" 
section .text 
    ;Display prompt 
    mov ah,9  ; print prompt 
    mov dx,prompt1 ; load register with prompt1 
    int 21h   ; display it 
    ; Input character and store. 
    mov ah,1  ; reach char fcn 
    int 21h   ; read character into al 
    mov bl,al  ; store character into bl 

Answer 1

我没有测试过，但总的来说，代码应该检查是否BL比39H小于31H或更大。这些是1和9的ASCII值。

所以一些示例代码看起来是这样的：

; Input character and store. 
loop1:    ; added label 
    mov ah,1  ; read char fcn 
    int 21h   ; read character into AL 
    mov bl, al  ; store character into BL 
    ; now comes the additional code 
    cmp bl, 31h  ; compare BL to the ASCII value of '1' 
    jb loop1  ; jump back if ASCII value is less than '1' = 31h 
    cmp bl, 39h  ; compare BL to the ASCII value of '9' 
    ja loop1  ; jump back if ASCII value is greater than '9' = 39h 
    ; BL contains an ASCII value between '1' and '9' which integer value can be acquired by subtracting the value 30h