9 Feb
2017
9 Feb
'17
5:51 p.m.
jnc(a)mercury.lcs.mit.edu (Noel Chiappa) wrote:
|> From: Michael Kjorling
|> That wouldn't have anything to do with how ^@ is a somewhat common
|> representation of 000, would it? .. I've always kind of wondered where
|> that notation came from.
|
|Well, CTRL-<*> is usually just the <*> character with the high bits \
|cleared.
|So, to have a printing representation of NULL, you have two character \
|choices
|- SPACE, and '@'. Printing "^ " is not so hot, so "^@" is
better.
|
|Also, if you look at an ASCII table, usually people just take the @-_ \
|column,
|and use that, since every character in that column has a printing
|representation. The ' '-? column is missing the ' ', and
`-<DEL> is missing
|the DEL. So if you just take a CTRL character and set the 0100 bit, \
|and print
|it as "^<char>", you get something readable.
You xor it via toupper(X)^0x40, yes of course. My code is right,
it is just the manual that is incomplete or even false: i will
clarify it. It is just that i know that many people which use
free software don't know what a xor operation is, at least without
looking into Wikipedia. (And even though i use it frequently
myself, that is often contaminated by politics, just yesterday
i had a hard time with some paragraphs on the German Wikipedia
page on intellectual properties.)
|(Note that CTRL-' ' _is_ usually used when one needs to _input_ a NUL
|character.)
|
| Noel
--steffen