Re: emacs-unicode-2: cpNNN and ibmNNN coding systems

[Kenichi Handa]

In article <address@hidden>, Reiner Steib <address@hidden> writes:

> Hi,
> in emacs-unicode-2, the coding systems ibm437 and cp437 are aliases:

> ,----[ M-x describe-coding-system RET ibm437 RET ]
> | D -- ibm437 (alias of cp437)
> | 
> | DOS codepage 437
> | Type: charset (charset)
> | EOL type: Automatic selection from:
> |     [cp437-unix cp437-dos cp437-mac]
> | This coding system encodes the following charsets:
> |   cp437
> `----

> However, according to
> <ftp://ftp.unicode.org/Public/MAPPINGS/VENDORS/IBM/README.TXT>, there
> are minor (?) differences between the Microsoft and IBM mappings:

> ,----[ <ftp://ftp.unicode.org/Public/MAPPINGS/VENDORS/IBM/README.TXT> ]
> | Code Pages 00437 (US etc.)
> |            00860 (Portugal)
> |            00861 (Iceland)
> |            00862 (Israel)
> |            00863 (Canadian French)
> |            00865 (Nordic)
> | 
> |       Microsoft                         IBM
> |       ---------                       -----
> | 0x1A      U001A                       U001C
> | 0x1C      U001C                       U007F
> | 0x7F      U007F                       U001A
> | 0xE6      U00B5 (MICRO SIGN)          U03BC (GREEK SMALL LETTER MU)
> | 
> | The "rotation" of the control characters at 0x1A, 0x1C and
> | 0x7F is due to the frequent use of 0x1A as end-of-file by
> | PC file systems and applications.
> `----

> I don't know if these and the differences in other code pages
> mentioned there are worth to make different coding systems instead of
> aliases.

I just followed the behaviour of iconv (and thus that of
glib).  It treats ibm437 the same as cp437.

http://www.openi18n.org/subgroups/sa/locnameguide/final/CodesetAliasTable.html

But, ummm, it seems that it is right to treat them as
different ones.  I'll fix charsets in emacs-unicode-2.


> If not, would it make sense to add aliases for ibmNNN in the trunk as
> well?

> [ Background: Today there was a posting with "charset=IBM437" in
>   de.comp.text.tex (<news:address@hidden>).  I thought
>   of adding an alias (ibm437 . cp437) in `mm-charset-synonym-alist'
>   (Gnus), but I wasn't sure if it's correct. ]

> Bye, Reiner.
> -- 
>        ,,,
>       (o o)
> ---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/



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