An advanced "Hello world!" program (source files)
The GNU Hello program produces a familiar, friendly greeting. Yes, this is another implementation of the classic program that prints "Hello, world!" when you run it. However, unlike the minimal version often seen, GNU Hello processes its argument list to modify its behavior, supports greetings in many languages, and so on. The primary purpose of GNU Hello is to demonstrate how to write other programs that do these things; it serves as a model for GNU coding standards and GNU maintainer practices.