[Info-vax] 8-bit characters

[Michael Moroney]

On 11/11/2021 12:42 AM, Phillip Helbig (undress to reply) wrote:
> In article <smh1k8$ul5$1 at dont-email.me>, Stephen Hoffman
> <seaohveh at hoffmanlabs.invalid> writes:
> 
>> On 2021-11-10 09:44:34 +0000, Phillip Helbig (undress to reply said:
>>
>>> Having to write some Icelanding words in a DECterm (as one does), I
> 
> "Icelandic" of course.
> 
>>> notice that COMPOSE-T-H and COMPOSE-t-h create upper and lower case
>>> thorn (Þ þ if those characters get through).  If entered by cboth
>>> create the character, unless it is at the beginning of a line, in which
>>> case one sees <XDE> or <XFE> (one character, displayed as several).
>>> ASCII values are 222 and 254.  Refreshing the screen also causes the
>>> mnenonics to appear.  Also, they are not displayed via HELP FORTRAN
>>> CHAR DEC.
>>>
>>> Any deeper reason or just flaky instrumentation?
>>>
>>> I also notice that × (COMPOSE-x-x) works fine in a DECterm but not on a
>>> real VT220 (where most or all other composed characters work).  Again,
>>> deeper meaning or just flaky?
>>
>> You're definitely not looking at ASCII, and AFAIK Þ and þ aren't
>> in DEC
>> MCS,
> 
> At least HELP FORTRAN CHAR DEC doesn't show them.
> 
>> which likely means you're looking at inconsistent handling of or
>> inconsistent configuration of ISO 8859-1 among your apps and OS and
>> hardware; I'd guess some here is MCS, and some 8859-1.
> 
> Only LK411, Alpha hardware and DECterm (under CDE, but that's probably
> irrelevant).  Maybe they are inconsistent.  :-|
> 
>> You've asked variations of this question over the years too, usually
>> involving trying to use EDT past ASCII or maybe past DEC MCS.
> 
> Yes.  :-)
> 
The character set ISO-8859-1 is almost the same as DEC-MCS with some of 
the undefined DEC-MCS characters being defined in ISO-8859-1.  The 
exceptions are a few rarely used characters such as Œ and Ÿ. 
Specifically, ISO-8859-1 has Icelandic Þ and þ, these positions are 
undefined in DEC-MCS. 99% of the time one can use ISO-8859-1 instead of 
DEC-MCS and get away with it.

There is an EDT patch which makes it more ISO-8859-1 friendly, actually 
prompted by a customer who used EDT for strictly ASCII except for a 
character at the 'þ' position (but not þ).  EDT fans may want the patch 
for its ability to understand terminals with more than 24 lines.