Do DVD-RW discs need to be formated?

DVD-RW DVD-RW discs can be used by some operating systems like MS Vista as regular recordable discs, meaning that you cannot alter what is recorded on them without erasing and recording new alter version of the same file. They cab be also used almost identically as hard drive, where you can record for example MS Word and alter it by opening it by Word application. In situation when you are using it as hard drive (or old fashion floppy disc for that matter), it has to be formated before such use.