[TUHS] // comment in C++

Noel Chiappa jnc at mercury.lcs.mit.edu
Fri Feb 10 00:44:15 AEST 2017


    > 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


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