阅读使用INT 21H（DOS）及一些; 8086 assmebly [英] Reading a number using INT 21h (DOS) & 8086 assmebly

问题描述

我要提示用户味精，告诉他写一个数字，然后我保存这个数字，做它的一些操作
在INT 21H搜索后，我发现这一点：

I need to prompt to user a msg that tells him to write a number , then I store this number and do some operation on it After searching in INT 21h I found this :

INT 21h / AH=1 - read character from standard input, with echo, result is stored in AL.
if there is no character in the keyboard buffer, the function waits until any key is pressed. 

example:

    mov ah, 1
    int 21h

的主要问题，这只能读取一个字符，再present它作为ASCII
所以如果我需要写数字357
我会读它为3，5，7

The main problem that this only reads one character and represent it as ASCII so If I need to write the number "357" I will read it as 3 , 5 , 7

和这不是我的目标。
任何想法？

and this is not my goal . any ideas ?

推荐答案

当设法让用户输入，把它的指针在ESI（ESI =地址字符串）

When you managed to get the user input, put the its pointer in ESI (ESI = address to the string)

.DATA
myNumber BYTE "12345",0        ;for test purpose I declare a string '12345'

Main Proc
    xor ebx,ebx                ;EBX = 0
    mov  esi,offset myNumber   ;ESI points to '12345'

loopme:

    lodsb                      ;load the first byte pointed by ESI in al

    cmp al,'0'                 ;check if it's an ascii number [0-9]
    jb noascii                 ;not ascii, exit
    cmp al,'9'                 ;check the if it's an ascii number [0-9]
    ja noascii                 ;not ascii, exit

    sub al,30h                 ;ascii '0' = 30h, ascii '1' = 31h ...etc.
    cbw                        ;byte to word
    cwd                        ;word to dword
    push eax
    mov eax,ebx                ;EBX will contain '12345' in hexadecimal
    mov ecx,10
    mul ecx                    ;AX=AX*10
    mov ebx,eax
    pop eax
    add ebx,eax
    jmp loopme                 ;continue until ESI points to a non-ascii [0-9] character
    noascii:
    ret                        ;EBX = 0x00003039 = 12345
Main EndP

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