'#' as comment character vs. '#' as erase character

[Guy Harris]

> > >	2) Why were the '#' and '@' characters used as editing characters,
> > >	   other than nostalgia for Multics (which used lots of weird IBM
> > >	   2741 printing terminals over half-duplex lines, and couldn't
> > >	   do much better)...
> > 
> The older UNIXes in cooked mode would echo everything one typed,
> including control characters.  About the only safe characters to
> use for "magic" things were printable characters such as \ # @.
> This works out better on hardcopy terminals, too, which is what
> most of the original UNIX terminals were.

OK, then, we rephrase the question as "why did the older UNIXes echo
everything one typed?"  The DEC OSes which echoed things sanely already
existed - they even handle hardcopy terminals about as well as one can (they
echo the characters being erased between backslashes).  The policy of
echoing things blindly also forced the policy of suppressing the output of
the EOT character, which policy tends to upset certain terminals which
accept positioning information in the form of 7-bit binary numbers (yes,
that's dumb, but those terminals do exist and we had to deal with them at
CCI).

	Guy Harris