This is from long ago as an escape character to enable you to have consts for control characters in a more readable way.
const
CtrlC = ^C;
begin
Write(Ord(CtrlC));
end.
This defines a Char constant with value #3
, then writes 3
in Borland Pascal 7, and I remember seeing it years before that too.
I just checked the Turbo Pascal 5.0 and Borland Pascal 7.0 languages guides, but could not find it, so it seems undocumented.
Edit: I do remember this was a Borland thing, and just [WayBack] checked: it is not part of the ISO Pascal standard (formerly this was ANSI Pascal Standard, thanks Sertac for noticing this).
It [WayBack] is documented in the Free Pascal documentation [WayBack].
SGI uses the backslash as escape character, as per their docs [WayBack].
More Edit: I found it [WayBack] documented in Delphi in a Nutshell and the [WayBack] Delphi Basics site.
Found it: Just found it on page 37 of the Turbo Pascal 3 Reference Manual [WayBack].