c/language/operator alternative

C source code may be written in any 8-bit character set that includes the invariant character set, even non-ASCII ones. However, several C operators and punctuators require characters that are outside of the ISO 646 codeset:. To be able to use character encodings where some or all of these symbols do not exist (such as the German ), there are two possibilities: alternative spellings of operators that use these characters or special combinations of two or three ISO 646 compatible characters that are interpreted as if they were a single non-ISO 646 character.

Operator macros
There are alternative spellings for the operators that use non-ISO646 characters, defined in as macros:

The characters and  are invariant under ISO-646, but alternatives are provided for the operators that use these characters anyway to accommodate even more restrictive historical charsets.

There is no alternative spelling (such as ) for the equality operator because the character  was present in all supported charsets.

Alternative tokens
The following alternative tokens are part of the core language, and, in all respects of the language, each alternative token behaves exactly the same as its primary token, except for its spelling (the stringification operator can make the spelling visible). The two-letter alternative tokens are sometimes called "digraphs" (even though it is four letters long is also considered a digraph).


 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }

Trigraphs
The following three-character groups (trigraphs) are, and each appearance of a trigraph is replaced by the corresponding primary character:


 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }
 * }

Because trigraphs are processed early, a comment such as will effectively comment out the following line, and the string literal such as  is parsed as.