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我这里有一个 TASM 代码，当我再次运行程序时它不会附加新字符串。我要感谢us2012帮助我达到这个“状态”。

; This example program creates a file and then writes to it.
.model small
.stack

.data 
CR equ 13
LF equ 10

StartMessage DB "This program creates a file called NEW.TXT"
         DB ,"on the C drive.$"

EndMessage DB CR,LF,"File create OK, look at file to"
       DB ,"be sure.$"

WriteMessage  DB "An error has occurred (WRITING)$"
OpenMessage   DB "An error has occurred (OPENING)$"
CreateMessage DB "An error has occurred (CREATING)$"

WriteMe  DB "HELLO, THIS IS A TEST, HAS IT WORKED?",0
FileName DB "new.txt",0 ; name of file to open 
Handle   DW ?   ; to store file handle 

.code 
START:
mov ax,@data    ; base address of data segment
mov ds,ax   ; put it in ds
mov dx,offset StartMessage 
mov ah,09h 
int 21h 

mov si,offset FileName  ; put offset of filename in dx 
xor cx,cx       ; clear cx - make ordinary file
mov ah,6Ch      ; function 3Ch - create a file
mov al, 0
int 21h         ; call DOS service
mov bx, Handle
xor cx, cx
xor dx, dx
mov ah, 42h
mov al, 02h
int 21h


jc CreateError      ; jump if there is an error



mov si,offset FileName  ; put offset of filename in dx
mov al,2        ; access mode -read and write
mov ah,3Dh      ; function 3Dh - open the file
int 21h         ; call dos service



jc OpenError        ; jump if there is an error



mov Handle,ax       ; save value of handle 
mov bx, Handle
xor cx, cx
xor dx, dx
mov ah, 42h
mov al, 02h
int 21h



mov dx,offset WriteMe   ; address of information to write 
mov bx,Handle       ; file handle for file
mov cx,38       ; 38 bytes to be written
mov ah,40h      ; function 40h - write to file
int 21h         ; call dos service

jc WriteError       ; jump if there is an error
cmp ax,cx       ; was all the data written?
jne WriteError      ; no it wasn't - error!

mov bx,Handle       ; put file handle in bx 
mov ah,3Eh      ; function 3Eh - close a file
int 21h         ; call dos service

mov dx,offset EndMessage 
mov ah,09h 
int 21h 

ReturnToDOS:

mov ax,4C00h        ; terminate program 
int 21h 

WriteError:
mov dx,offset WriteMessage 
jmp EndError

OpenError:
mov dx,offset OpenMessage 
jmp EndError

CreateError:
mov dx,offset CreateMessage 

EndError:
mov ah,09h 
int 21h 
mov ax,4C01h 
int 21h 

END START

如果我使用3Ch，程序可以工作，但它不会附加到文件的末尾。通过使用6Ch而不是3Ch，这表示它不会将现有文件截断为零字节，但是每当我运行代码时，创建文件时都会出错（未创建文件）。请帮我修复代码。非常感谢你！

编辑2：

; This example program creates a file and then writes to it.
.model small
.stack

.data 
CR equ 13
LF equ 10

StartMessage DB "This program creates a file called NEW.TXT"
         DB ,"on the C drive.$"

EndMessage DB CR,LF,"File create OK, look at file to"
       DB ,"be sure.$"

WriteMessage  DB "An error has occurred (WRITING)$"
OpenMessage   DB "An error has occurred (OPENING)$"
CreateMessage DB "An error has occurred (CREATING)$"

WriteMe  DB "HELLO, THIS IS A TEST, HAS IT WORKED?",0
FileName DB "new3.txt",0 ; name of file to open 
Handle   DW ?   ; to store file handle 

.code 
START:
mov ax,@data    ; base address of data segment
mov ds,ax   ; put it in ds
mov dx,offset StartMessage 
mov ah,09h 
int 21h 

mov si, offset FileName     ; put offset of filename in dx 
xor cx,cx       ; clear cx - make ordinary file
mov ah,6Ch      ; function 3Ch - create a file
mov bx, 3
mov dx, 12h
int 21h         ; call DOS service

jc CreateError      ; jump if there is an error

mov ah,3Eh      ; function 3Eh - close a file
int 21h         ; call dos service


mov dx, offset FileName     ; put offset of filename in dx
mov al,2        ; access mode -read and write
mov ah,3Dh      ; function 3Dh - open the file
int 21h         ; call dos service

jc OpenError        ; jump if there is an error

mov Handle,ax       ; save value of handle
mov bx, Handle
xor cx, cx
xor dx, dx
mov ah, 42h
mov al, 02h
int 21h

mov dx,offset WriteMe   ; address of information to write 
mov bx,Handle       ; file handle for file
mov cx,38       ; 38 bytes to be written
mov ah,40h      ; function 40h - write to file
int 21h         ; call dos service

jc WriteError       ; jump if there is an error
cmp ax,cx       ; was all the data written?
jne WriteError      ; no it wasn't - error!

mov bx,Handle       ; put file handle in bx 
mov ah,3Eh      ; function 3Eh - close a file
int 21h         ; call dos service

mov dx,offset EndMessage 
mov ah,09h 
int 21h 

ReturnToDOS:

mov ax,4C00h        ; terminate program 
int 21h 

WriteError:
mov dx,offset WriteMessage 
jmp EndError

OpenError:
mov dx,offset OpenMessage 
jmp EndError

CreateError:
mov dx,offset CreateMessage 

EndError:
mov ah,09h 
int 21h 
mov ax,4C01h 
int 21h 

END START
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1 回答 1

1

看这部分：

mov dx,offset FileName  ; put offset of filename in dx 
xor cx,cx       ; clear cx - make ordinary file
mov ah,6Ch      ; function 3Ch - create a file
mov al, 0
int 21h         ; call DOS service

并在相关文档中：

AX = 6C00h
BL = open mode as in AL for normal open (see also AH=3Dh)
...
BH = flags
...
CX = create attribute (see #01769).
DL = action if file exists/does not exist (see #01770).
DH = 00h (reserved).
DS:SI -> ASCIZ file name

Return:
CF set on error AX = error code (see #01680 at AH=59h/BX=0000h)
CF clear if successful AX = file handle
CX = status (see #01768)

该函数期望si并且没有dx文件名的偏移量。

你不设置bx。

你不设置dx。

你不检查错误。

您不保存文件句柄。

看这部分：

mov bx, Handle
xor cx, cx
xor dx, dx
mov ah, 42h
mov al, 02h
int 21h

Handle此时未初始化，因为您从未将句柄保存到此变量中。

现在，这里：

mov dx,offset FileName  ; put offset of filename in dx
mov al,2        ; access mode -read and write
mov ah,3Dh      ; function 3Dh - open the file
int 21h         ; call dos service

您正在尝试再次打开打开的文件。您需要在打开之前将其关闭。或者，如果您有句柄，请继续使用该文件，不要关闭并重新打开它。

于 2013-03-31T08:07:25.157 回答