--On Tuesday, 08 January, 2008 11:40 -0500 Jeffrey Hutzelman
<jhutz(_at_)cmu(_dot_)edu> wrote:
The following sentence appears near the beginning of section 4:
In retrospect, one of the
advantages of ASCII [X3.4-1978] when it was chosen was that
the code space was full when the Standard was first
published. There was no practical way to add characters or
change code point assignments without being obviously
incompatible.
I don't think I've seen this observation made in writing
before, and it is interesting. However, I see a couple of
problems. Particularly, the fact that there was no way to
change code point assignments without being obviously
incompatible did not in fact prevent such changes. While that
change is little more than a footnote today (few people have
documents lying around whose meaning depends on the left-arrow
and up-arrow and are destroyed by using underscore and caret
instead), a similar change today to either ASCII or Unicode
could be disastrous, depending on the code points changed.
My recollection is that the left-arrow and up-arrow changes were
made between BCD and ASCII. Unless my memory is gone, the 1968
version of ASCII and the first terminal device to natively
implement it (the TTY-38)already used underscore and carat
although some printers continued to use the earlier forms.
There is a better example of the comment you are making, and it
is precisely the reason that key Internet standards continue to
reference X3.4-1968 rather than the current ANSI INCITS 4-1986
(R2007). The 1968 version was (again, I'm doing this from
memory -- I have a copy, but it is too deeply buried for me to
get to right now-- was clear that LF provided only what we now
call an index function (contributing to the network use of
CRLF). Later versions more or less permitted implementations to
make up their minds how they wanted to interpret it.
Secondly, the reference tag [X3.4-1978] is wrong, as the
target of the reference is actually X3.4-1968 (and in fact the
references section uses the wrong tag, but the correct
citation).
Sorry. I misread this when the note first went past me, hence
the late response. Thanks for catching this stupid typographic
error... fixed in -09.
john
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