CentralNotice From Wikipedia, the free encyclopedia Jump to: navigation , search For other uses, see Digraph (disambiguation) and Trigraph (disambiguation) . This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed. (September 2008) In computer programming , digraphs and trigraphs are sequences of two and three characters respectively, appearing in source code , which a programming language specification requires an implementation of that language to treat as if they were one other character. 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....