trigraphs in X3J11

[Martin Minow THUNDR::MINOW ML3-5/U26 223-9922]

Perhaps one of the trigraphs experts could anser a simple question:
Suppose I've written a fully-compliant C compiler (that handles trigraphs)
that I sell to my friend in Visby, Sweden who needs trigraphs since his
language has national letters replacing the "[\]{|}" of US ASCII.  He writes
his first program as:

	??= include <stdio.h>
	main() ??<
		printf("H{lsningar fr}n Visby p} \land!??/n");
	??>

When he runs my compiler, How does it know that the charcter whose value
is decimal 92 is a national letter, and not a backslash that crept in?
Do I need command line arguments or a ??=pragma?  Are they permitted by
the standard?

Will all ??=include files be required to be distributed in their
trigraphed format?

Martin Minow
minow%thundr.dec at decwrl.dec.com