From: Jim Allan (email@example.com)
Date: Sat Apr 11 2009 - 13:48:41 CDT
Jukka K. Korpela wrote:
> I'm not sure what you mean by "such" here, but in fact, even in the
> 1980s and early 1990s, DECsystem-10 and -20 (PDP-10 and -20) used a
> word length of 36 bits, packing five 7-bit ASCII characters in one
> word (and using the spare bit for special purposes).
> ASCII was surely designed to allow implementations where 7 bits are
> used for one character. Don't confuse this with the current situation
> where such implementations are obsolete and "everyone" uses at least 8
> bits for a character, even when working with ASCII only.
From http://www.neurophys.wisc.edu/comp/docs/ascii/ :
"It was therefore decided to use 7 bits to store the new ASCII code,
with the eighth bit being used as a parity bit to detect transmission
From http://czyborra.com/charsets/iso646.html :
"ASCII uses only 7 bits and allows the most significant eighth bit to be
used as parity bit, highlight bit, end-of-string bit (all of which are
considered bad practice nowadays) or to include additional characters
for internationalization <http://czyborra.com/charsets/iso8859.html>
(i18n for which we need 8bit-clean programs that do none of
afore-mentioned silly tricks) but ASCII defined no standard
<http://czyborra.com/charsets/iso8859.html> for this and many
manufacturers invented their own proprietary codepages
For an original ASCII definition see
"This character set is the first of a family of sets. Higher-order sets
will enlarge the repertoire for both 'graphics' and 'controls'."
Though not defined in the original standard, from the beginning it was
understood that ASCII would normally run in an 8-bit environment and
that the 8th bit could be used to define additional characters, and that
the standards committee expected to define higher-order sets.
This archive was generated by hypermail 2.1.5 : Sun Apr 12 2009 - 10:52:38 CDT