The .au file format--``au'' is short for ``audio''--was developed by Sun for use with telephone transmissions processed by Unix computers, and it became one of the earliest formats commonly used for audio files on personal computers. It is now primarily only of historical interest. The extension .snd is used for files in this format on Sun, NeXT, and Silicon Graphics computers. Although .au files usually contain PCM audio, the format can also handle several compressed formats.3.4