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<TITLE>Int 21/AH=40h
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Int 21/AH=40h - DOS 2+ - WRITE - WRITE TO FILE OR DEVICE -
AH = 40h
BX = file handle
CX = number of bytes to write
DS:DX - data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see #01680 at AH=59h/BX=0000h)
Notes: if CX is zero, no data is written, and the file is truncated or
extended to the current position
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<h2>Int 21/AH=40h
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<h3><font color=#C00040>DOS 2+ - WRITE - WRITE TO FILE OR DEVICE</font></h3>
<PRE>
AH = 40h
BX = file handle
CX = number of bytes to write
DS:DX -> data to write<br>
<p><b>Return:</b><br>CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) <a href="javascript:if(confirm('http://www.ctyme.com/intr/rb-0000.htm \n\nThis file was not retrieved by Teleport Pro, because it was unavailable, or its retrieval was aborted, or the project was stopped too soon. \n\nDo you want to open it from the server?'))window.location='http://www.ctyme.com/intr/rb-0000.htm#Table0'" tppabs="http://www.ctyme.com/intr/rb-0000.htm#Table0"></a>(see #01680 at AH=59h/BX=0000h)
</PRE>
<p><b>Notes:</b>
If CX is zero, no data is written, and the file is truncated or
extended to the current position.
Data is written beginning at the current file position, and the file
position is updated after a successful write.
For FAT32 drives, the file must have been opened with AX=6C00h with
the "extended size" flag in order to expand the file beyond 2GB;
otherwise the write will fail with error code 0005h (access denied).
The usual cause for AX < CX on return is a full disk
<p><b>BUG:</b>
A write of zero bytes will appear to succeed when it actually failed
if the write is extending the file and there is not enough disk
space for the expanded file (DOS 5.0-6.0); one should therefore check
whether the file was in fact extended by seeking to 0 bytes from
the end of the file (INT 21/AX=4202h/CX=0000h/DX=0000h).
Under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
<p><b>See Also:</b>
<a href="rb-2684.htm" tppabs="http://www.ctyme.com/intr/rb-2684.htm">AH=28h</a> - <a href="rb-2783.htm" tppabs="http://www.ctyme.com/intr/rb-2783.htm">AH=3Fh"DOS"</a> - <a href="rb-3268.htm" tppabs="http://www.ctyme.com/intr/rb-3268.htm">AH=93h</a> - <a href="rb-4313.htm" tppabs="http://www.ctyme.com/intr/rb-4313.htm">INT 2F/AX=1109h
<p>
<b>Category: <a href="cat-010.htm" tppabs="http://www.ctyme.com/intr/cat-010.htm">
DOS Kernel</a>
- <a href="int-21.htm" tppabs="http://www.ctyme.com/intr/int-21.htm">
Int 21h</a>
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