Emacs doesn't write with the encoding it used for reading

[Rommerskirchen Heinrich]

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In GNU Emacs 21.2.1 (i386-msvc-nt4.0.1381)
 of 2002-03-19 on buffy
configured using `configure --with-msvc (12.00)'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: DEU
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

If a file contains a mixture of German DOS-encoded text (cp850) and
German Windows-encoded text it is read as latin1 but emacs will not
write it back as latin1.

Simple Example:
A file contains the 4 Bytes 0xE4 0x84 0x0D 0x0A. (Umlaut-a in DOS and Windows
encoding followed by CR LF).

Emacs unter German Windows reads it as latin1. If I now type a
character and delete it again, so that I have the same content,
emacs will not write it back as latin1 but instead suggests a few
encodings with default utf8.

Saving with utf8 gives a file with 6 bytes, which emacs again reads as latin1, 
but doesn't
write as latin1, choosing again utf8 gives a file with 10 bytes and this doesn't
change anymore, but contains neither of the original two characters.

Saving the original file (4 bytes) with raw-text gives a file with 5 bytes which
doesn't change anymore on reading and writing (emacs uses encoding 
raw-text-dos), it contains
the original bytes plus a spurious \201 (Umlaut-u in DOS encoding)

Recent input:
C-x C-f / t e m p / x x <return> <end> SPC <backspace> 
C-x C-s C-g <menu-bar> <help-menu> <report-emacs-b
ug>

Recent messages:
(C:\bin\emacs-21.2\bin\emacs.exe -q --no-site-file)
For information about the GNU Project and its goals, type C-h C-p.
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Regards

Heinz