Question

I have always wondered how OSs such as Windows or Mac OS X can just change languages in 1 click and all a sudden, all message boxes, buttons etc are changed.

How are these sorts of mechanisms implemented?

Thanks

Answer 1

The key to internationalization is to avoid hard-coding any text that will be seen by the user. Instead, call a function that checks the locale and chooses the text appropriately.

A contrived example:

// A "database" of the word "hello" in various languages.
struct _hello {
  char *language;
  char *word;
} hello[] = {
  { "English", "Hello" },
  { "French", "Bon jour" },
  { "Spanish", "Buenos dias" },
  { "Japanese", "Konnichiwa" },
  { null, null }
};

// Print, e.g. "Hello, Milo!"
void printHello(char *name) {
  printf("%s, %s!\n", say_hello(), name);
}

// Choose the word for "hello" in the appropriate language,
// as set by the (fictitious) environment variable LOCALE
char *say_hello() {
  // Search until we run out of languages.
  for (struct _hello *h = hello; h->language != null; ++h) {
    // Found the language, so return the corresponding word.
    if (strcmp(h->language, getenv(LOCALE)) == 0) {
      return h->word;
    }
  }
  // No language match, so default to the first one.
  return hello->word;
}