5.1 Write Programs in English!

In principle, you can write the function and variable names in a program, and the comments, in any human language. C allows any kinds of characters in comments, and you can put non-ASCII characters into identifiers with a special prefix. However, to enable programmers in all countries to understand and develop the program, it is best given today’s circumstances to write identifiers and comments in English.

English is the one language that programmers in all countries generally study. If a program’s names are in English, most programmers in Bangladesh, Belgium, Bolivia, Brazil, and Bulgaria can understand them. Most programmers in those countries can speak English, or at least read it, but they do not read each other’s languages at all. In India, with so many languages, two programmers may have no common language other than English.

If you don’t feel confident in writing English, do the best you can, and follow each English comment with a version in a language you write better; add a note asking others to translate that to English. Someone will eventually do that.

The program’s user interface is a different matter. We don’t need to choose one language for that; it is easy to support multiple languages and let each user choose the language to use. This requires writing the program to support localization of its interface. (The gettext package exists to support this; see The GNU C Library in The GNU C Library Reference Manual.) Then a community-based translation effort can provide support for all the languages users want to use.