在程序集中附加到文本文件

Question

美好的一天！我这里有一个TASM代码，当我再次运行该程序时，它不会追加新的字符串。追加的代码行是什么？非常感谢！

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

jc CreateError      ; jump if there is an error

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 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

而且，在将字符串放入文件之前，是否需要终止程序？非常感谢！

编辑@ us2012：按照您的回答，我应该替换

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

with

mov dx,offset WriteMe   ; address of information to write 
mov bx,Handle       ; file handle for file
mov cx,38       ; 38 bytes to be written
;xor dx, dx
mov ah,40h      ; function 40h - write to file
mov al, 02h
int 21h         ; call dos service

？当我再次运行该程序时，它仍然没有追加。仍然是单个HELLO, THIS IS A TEST, HAS IT WORKED?。

Answer 1

int21h参考资料指出，要移动文件指针，可以使用函数42h。详细信息为here，因此应在写入前查找以下文件末尾：

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

Answer 2

.data
filename db 'myfile.txt',0
handler dw ?
msg db "hello$"
buffer db 1000 dup (?)
writeme db "world$"
.code
;;;;;;;;;;APPENDING
    append proc
        mov dx,offset writeme
        mov bx,handler
        mov cx,5  ;length of appended string
        mov ah,42h
        mov ah,09h
        int 21h
    append endp
end