On Mon, Jan 6, 2020 at 3:51 PM Dave Horsfall <dave@horsfall.org> wrote:
On Mon, 6 Jan 2020, Brian Walden wrote:

> csh(1) was wrtten around 1978 and yes # as a comment was only for
> scrtipts, think it was why would you need to comment interactively?

Why would you *not* want to?  You've just made "#" asymmetric in its
behaviour; in the meantime the parser just sees an unescaped "#" and
ignores everything after that, without regard to context.

You might also be using "script" e.g.

     script
     blah blah
     # Now here I do something funky
     *really* funky stuff
     ^D

Or you might have cut and paste the commands from a script to test something, or to redo something by hand that failed for some reason.

Warner
 
[...]

> Also before you say wait! ALGOL uses # as comment and is older than
> Kernighan' ratfor(1). [...]

Funny; I recall ALGOL using "comment ... ;" or was that ALGOLW (which I
loved using; I wish I still had my ALGOLW book)?

-- Dave