Source : Free On-Line Dictionary of Computing

hello, world
     
        The canonical minimal test message in the {C}/{Unix} universe
        or any of the minimal programs that emit this message.
        Traditionally, the first program a C coder writes in a new
        environment is one that just prints "hello, world" to standard
        output (and indeed it is the first example program in {K&R}).
        Environments that generate an unreasonably large executable
        for this trivial test or which require a {hairy}
        compiler-linker invocation to generate it are considered bad
        (see {X}).