Digraphs and trigraphs (programming)

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In computer programming, digraphs and trigraphs are sequences of two and three characters, respectively, that appear in source code and, according to a programming language's specification, should be treated as if they were single characters. Trigraphs have been removed from the C++ language, and will be from C as of C23, thus likely aren't used much in practice in C already, nor in any other mainstream language (use of them in the language J is an exception). In the modern world of Unicode/UTF-8 (even just with ASCII) there's no need for trigraphs in language design, which were considered a burden, and neither really digraphs, that likely have very few users, at least in those languages.

Various reasons exist for using digraphs and trigraphs: keyboards may not have keys to cover the entire character set of the language, input of special characters may be difficult, text editors may reserve some characters for special use and so on. Trigraphs might also be used for some EBCDIC code pages that lack characters such as { and }.