1

我正在学习汇编语言。我在 MASM 中编写了一个程序，并希望提示用户给我一个数学问题的答案。我的程序可以正常工作，只是一个变量没有正确更新。

示例：第一次尝试：用户输入：123/变量值应为 123 - 程序显示值，123 第二次尝试：用户输入：1/变量值应为 1 - 程序显示值，1231

这是一些与我编写的程序相关的代码。有人可以看看并给我一些关于如何更新变量（input_dec）的提示吗？在此先感谢您的帮助。

    .data

new_prb1        BYTE    "Another problem? (y/n): ", 0
input_str       BYTE    21 DUP(0)   ;string to be entered
input_dec       DWORD   ?

.code
main PROC

; prompt and get user's answer
push OFFSET input_str   ;ebp+12
push OFFSET input_dec   ;ebp+8
call getData


; play again?
; the program repeats until the user chooses to quit
;push   OFFSET again_resp   ;ebp+8
;call   play_again  

play_again:
        displayString new_prb1

        ;get user input
        mov     edx, OFFSET again_resp       ;move OFFSET of again_resp to receive 
user response
        mov     ecx, 12 
        call    ReadString
        cmp     eax, 1
        jg      input_notOK

        mov     esi,edx         ;point at char in string 

        convert_str:
            mov     al,[esi]        ;move value of char into al register
            inc     esi             ;point to next char
            cmp     al,121          ; 'y' is character 121
            je      next_game
            cmp     al,110          ; 'n' is character 110
            je      game_over
            jmp     convert_str
        input_notOK:
            displayString error_msg
            jmp     play_again
        next_game:

            push OFFSET input_str
            push OFFSET input_dec
            call getData

            jmp     play_again
        game_over:
            displayString   good_bye
            call    CrLf


    exit    ; exit to operating system
main ENDP



; ***************************************************************
;Procedure to prompt and get an answer from the user.
;receives: addresses of parameters on the system stack
;returns: user input value for the reference
;preconditions:  none
;registers changed: eax, ebx, ecx, edx, esi
; ***************************************************************
getData PROC
    push ebp
    mov  ebp, esp

    again:
        displayString prompt_1
        mov     edx, [ebp+12]       ;move OFFSET of input_str to receive string of integers
        mov     ecx, 12 
        call    ReadString
        cmp     eax, 10
        jg      input_notOK

        mov     ecx, eax        ;loop for each char in string
        mov     esi,[ebp+12]    ;point at char in string

        pushad
        convert_str:
            mov     ebx,[ebp+8]
            mov     eax,[ebx]       ;move address of input_dec into eax
            mov     ebx,10d         ;10d     
            mul     ebx             ;multiply answer by 10 - eax=x*10
            mov     ebx,[ebp+8]     ;move address of input_dec into ebx
            mov     [ebx],eax       ;add product to answer
            mov     al,[esi]        ;move value of char into al register 
            mov     eax, [esi]
            inc     esi             ;point to next char
            sub     al,48d          ;subtract 48 from ASCII value of char to get integer  
            cmp     al,0            ;error checking to ensure values are digits 0-9 
            jl      input_notOK
            cmp     al,9            ;error checking to ensure values are digits 0-9 
            jg      input_notOK

            mov     ebx,[ebp+8]    ;move address of input_dec into ebx  
            add     [ebx],al       ;add int to value in input_dec   
            loop    convert_str  
        popad
        jmp     continue
        input_notOK:                  
            popad     
            displayString   error_msg
            jmp     again
        continue:
            pop     ebp
            ret     8
getData ENDP
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2 回答 2

3

input_dec开头清晰getData。像这样的东西：

getData PROC
push ebp
mov  ebp, esp

mov eax, [ebp+8]
mov dword ptr [eax],0  ; input_dec = 0
于 2013-05-30T17:14:39.793 回答
0

我认为您仍在将结果乘以寄存器。尝试在每次打印操作后重置该寄存器。

于 2013-05-30T17:08:54.977 回答