> On Thu, 9 Feb 2017, Michael Kjörling wrote:
>
> > I didn't know that // was now accepted to begin a comment in C, but I 
> > strongly suspect that any compiler modern enough to know about that will 
> > know just as well about #if 0.

Dave Horsfall <dave at horsfall.org> wrote:
> // isn't in ANSI C, but I've been using it for years on quite a few 
> platforms (I see that even M$ supports it); I don't know where I first saw 
> it.

It was added in C99.

Arnold