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 Unicode characters in comments, and you can put them into identifiers with a special prefix (see Unicode Character Codes). However, to enable programmers in all countries to understand and develop the program, it is best under today’s circumstances to write all identifiers and comments in English.

English is the common language of programmers; in all countries, programmers generally learn English. If names and comments in a program are written in English, most programmers in Bangladesh, Belgium, Bolivia, Brazil, Bulgaria and Burundi can understand them. In all those countries, most programmers 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 for display. 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.