From: Philippe Verdy (verdy_p@wanadoo.fr)
Date: Fri Oct 10 2003 - 18:43:26 CST
Note that IBM ICU data for DEC-MCS is based on the glibc implementation, but
this is not authoritative for this DEC charset, as the glibc "fills the
holes" by mapping ISO-8859-1 characters in unassigned positions. This
corresponds to a common practice, that maximizes the compatibility with
ISO-8859-1 (and thus Unicode code points in range U+0000 to U+00FF).
The listed incompatibilities of DEC-MCS with ISO-8859-1 are only those 3:
<!--
<OE> /xD7 <U0152> LATIN CAPITAL LIGATURE OE,
instead of:
<??> /xD7 <U+00D7> MULTIPLICATION SIGN
-->
<a u="0152" b="D7"/>
<!--
<oe> /xF7 <U0153> LATIN SMALL LIGATURE OE
instead of:
<??> /xF7 <U+00F7> DIVISION SIGN)
-->
<a u="0153" b="F7"/>
<!--
<Y:> /xDD <U0178> LATIN CAPITAL LETTER Y WITH DIAERESIS
instead of:
<??> /xDD <U+00DD> LATIN CAPITAL LETTER Y WITH ACUTE
-->
<a u="0178" b="DD"/>
In the original DEC-MCS set, the following positions were normally not
assigned (except in some extension found in more recent versions of VMS???)
like they are in the iconv tables for glibc:
<??> /xA0 <U+00A0 in iconv???>
<??> /xA4 <U+00A4 in iconv???>
<??> /xA6 <U+00A6 in iconv???>
<??> /xAC <U+00AC in iconv???>
<??> /xAD <U+00AD in iconv???>
<??> /xAE <U+00AE in iconv???>
<??> /xAF <U+00AF in iconv???>
<??> /xB4 <U+00B4 in iconv???>
<??> /xB8 <U+00B8 in iconv???>
<??> /xBE <U+00BE in iconv???>
<??> /xD0 <U+00D0 in iconv???>
<??> /xDE <U+00DE in iconv???>
<??> /xF0 <U+00F0 in iconv???>
<??> /xFD <U+00FD in iconv???>
<??> /xFE <U+00FE in iconv???>
Additionally some characters were at other places (adding another
incompatibility...):
<??> /xA8 <U+00A4>
I have also found extensions of DEC-MCS built for DBCS handling, but I don't
have the details about how they work (for Japanese?) or if they used the
ISO2022 encoding model, or some DEC VT controls in the encoded range /x80 to
/x9F, which includes two PUA positions at /x91 and /x92...
If someone has kept the technical references of those old DEC VT terminals
using them, may he could answer more precisely... Ask now to Compaq or to
HP?
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