更新：

好吧，我写了这个proc TextManipulations。我认为它是工作。正确的值是在缓冲区，但问题是这一部分：

Save_to_res_txt:        
    mov ah, 40h
    mov bx, outputFD
    mov cx, 9; filesize                           
    mov dx, offset buffer
    int 21h

字符串
filesize是从文件data.txt读取的字节数。字符串操作程序后，应使用ah = 40h, int 21h从缓冲区写入相同数量的字节到文件res.txt。编译器显示所有寄存器中的良好值，但在int 21 h后，res.txt 慡硡䙅G扸扢中出现随机字符。
如果程序写入超过9个字节，则在文件res.txt中存在随机字符。如果小于或等于9，则文件包含良好值（12个中的9个）。

如果我将输出从文件更改为控制台mov bx, 2程序显示正确的字符串。

我不知道该怎么做，所以我使用标准输出来显示最终结果。

第一个答案

我在调试器里检查过了。是的，问题出在TextManipulations里面。
例如data.txt包含以下字符aaaxabcdxbbb。
buffer = aaaxabcdxbbbstring1 = abcd
第一次比较就OK了

mov al, byte ptr [si]               ; 61 | 61
    mov ah, byte ptr [di]               ; 61 | 62
    cmp al, ah

型
CheckForString将di移动到string1中的下一个位置。字符保存到tmpBuffer，程序跳转到检查下一个字符。
现在我们有a和b，所以这是不匹配的。
mov ah, 40h从tmpBuffer向res.txt写入1个字符（cx = 1）。
下一部分停止调试器，返回系统。

mov cx, 1
    mov dx, si
    int 21h

型
如果我把input改为abaxabcdxbbb，输出里面只有b。字符总是存储在tmpBuffer的同一个地方，因为di总是等于offset tempBuf。

产品代码：

.MODEL small
.STACK 256
.DATA
    help db "Hello,", 10, 13, "provide arguments like in the example: program.exe data.txt abcd EFG res.txt", 10, 13, "$"
    FileProblem db "Provided file wasn't found.", 10, 13, "Provide arguments like in the example: program.exe data.txt abcd EFG res.txt", 10, 13, "$"
    input db 255 dup(0)
    inputFD dw ?               
    filesize dw 0                   
    string1 db 255 dup(0)
    string2 db 255 dup(0)
    output db 255 dup(0)
    outputFD dw ?              
    buffer db 512 dup(?)
    tempBuf db 255 dup(?) 
      
.CODE
Start:
    mov ax, @data
    mov ds, ax

    xor cx, cx
    xor ah, ah
    mov cl, [es:0080h]
    cmp cx, 4                           ; 4 parameters, 26 characters total, skip Helpmsg
    jbe Helpmsg
    jne SkipHelp

SkipHelp:

    xor di, di                          ; di = 0
    mov bx, 82h                         ; bx = parameter area(81h) + 1 (skip space)
    mov si, offset input                ; save argument in input / data.txt - input file ... offset 00c7
    call SaveArgument                   ; data.txt copied to ds:00c7
    mov si, offset string1              ; save argument in string1 / abcd ... offset 01ca
    call SaveArgument                   ; abcd copied to ds:01ca
    mov si, offset string2              ; save argument in string2 / EFG ... offset 02c9
    call SaveArgument                   ; EFG copied to ds:02c9
    mov si, offset output               ; save argument in output / res.txt - output file ... offset 03c8
    call SaveArgument                   ; res.txt copied to ds:03c8

    xor ax, ax                          
    mov ah, 3Dh                         ; open file
    mov al, 00                          ; read-only
    mov dx, offset input                ; data.txt
    int 21h                     
    jc MissingFile
    mov inputFD, ax                     ; data.txt handle

    mov ah, 3Fh                         ; read from data.txt
    mov bx, inputFD                     ; data.txt handle
    mov cx, 200                         ; read 200 bytes    
    mov dx, offset buffer               ; read here, ds:04c9
    int 21h                             ; return ax = 12 bytes read
                                        ; data.txt = aaaxabcdxbbb
    mov filesize, ax                    ; save file size, we use this later
    
    mov ah, 3Ch                         ; create / open file
    mov cx, 2                           ; read-only
    mov dx, offset output               ; file name "res.txt"
    int 21h
    mov outputFD, ax                    ; res.txt handle
    
    call TextManipulations              
    
    mov ah, 3Eh                         ; close file
    mov bx, outputFD
    int 21h

Final:
    mov ah, 4Ch                         ; bye
    int 21h

Helpmsg:
    mov ah, 09h
    mov dx, offset help
    int 21h
    JMP Final

MissingFile:
    mov ah, 09h
    mov dx, offset FileProblem
    int 21h
    jmp Final

SaveArgument PROC
Begin:
    mov dx, es:[bx]                     ; dx = character from parameter area            
    inc bx                              ; move to next character
    cmp dl, 20h                         ; space separates parameters
    je StopSpace
    cmp dl, 13                          ; we reached end of parameters area
    je StopEnter
    mov byte ptr [si], dl               ; insert character to [si]
    inc si                              ; next position in memory area pointed by si
    jmp Begin                           ; repeat
StopSpace:                              
    inc di                              ; increment number of parameters or count spaces between params ?
    ret                                 ; we are done here
StopEnter:
    cmp di, 3                           ; 3 spaces separates 4 params, if less we have error
    jb Helpme
    ret
Helpme:
    mov ah, 09h
    mov dx, offset help
    int 21h
    mov ah, 4Ch                         ; see You next time
    int 21h
    ret
SaveArgument ENDP

TextManipulations PROC
    mov si, offset buffer               ; buffer = aaaxabcdxbbb, 04c9
    mov di, offset string1              ; string1 = abcd, 01c6
    xor cx, cx                          ; matching letters counter
    mov dx, di                          ; save offset of the first character in string1 

    Read:   
        cmp byte ptr [si], 0            ; end of buffer ?
        je Return                       ; yes, no more characters in buffer, return
    
        Characters_cmp:
            mov al, byte ptr [si]       ; 61 | 61
            mov ah, byte ptr [di]       ; 61 | 62
            cmp al, ah
            je Characters_are_equal
    
        Reset_strings:                  ; characters are diffrent
            cmp dx,di                   ; if first letter in string1 is diffrent from letter in buffer
            jz next_in_buffer           ; take another letter from buffer to avoid infinity loop    
        
            mov di, offset string1      ; else just reset position in string1
            jmp Reset_counter
        
        next_in_buffer:
            inc si      

        Reset_counter:
            xor cx, cx                  ; reset counter
            jmp Characters_cmp

    Characters_are_equal:
        inc cx                          ; increase counter
        inc si                          ; next character in buffer
        inc di                          ; we want to check next character in string1
        cmp byte ptr [di], 0            ; we checked all characters ?
        je ReplaceString                ; yes, we found matching string

        jmp Read

    ReplaceString:
        sub si,cx                           ; move to start of the matching string
        mov bx, offset string2              ; copy this to buffer
        
        Copy_new_string:
            mov al,[bx]
            mov [si],al
            inc si
            inc bx
            loop Copy_new_string
    
    
        Save_to_res_txt:        
            mov ah, 40h
            mov bx, 2             ;[outputFD]
            mov cx, [filesize]    ; 9                           
            mov dx, offset buffer
            int 21h

    Return:
        ret
TextManipulations ENDP
END Start

型