9 Feb
2017
9 Feb
'17
3:44 p.m.
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.
(Note that CTRL-' ' _is_ usually used when one needs to _input_ a NUL
character.)
Noel