Re: DEC-MCS mapping, anyone?

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?



This archive was generated by hypermail 2.1.5 : Thu Jan 18 2007 - 15:54:24 CST