Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!unmvax!indri!aplcen!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: Dumb question: What IS a trigraph?
Message-ID: <10762@smoke.BRL.MIL>
Date: 17 Aug 89 15:09:42 GMT
References: <3566@uwovax.uwo.ca>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 14

In article <3566@uwovax.uwo.ca> 2014_5001@uwovax.uwo.ca writes:
>Every so often someone mentions a trigraph.  What is a trigraph???

There's one (the "???").  Standard C requires that, very early in
the phases of translation, certain sequences of three source characters
starting with "??" be mapped into equivalent single characters.  This
is intended to allow C programs to be expressed entirely using the
ISO-646 basic character set, which does not include {, |, and several
other essential C source characters.  It is not expected that real
programming environments would ever require programmers to type these
trigraph sequences; they're intended primarily for program interchange
among different sites.  Unless you're importing a lot of code from
European sites or are implementing a C compiler, you shouldn't have to
be concerned about trigraphs, since you'll never use nor see them.