DAT file is a file format written to save sounds, midi, wave, pallets, images, and levels. In short, this file format contains vital information for specific software, and the data is usually in either binary or plain text. In rare cases, DAT files may include a video file. DAT files are opened using text editors like Notepad++ and TextEdit.
AU is an audio format standard in early web pages NEXT systems. It is also called u-law or Sparc-audio format. Typically, AU files can store audio data and annotation blocks. Initially, it was a headerless audio format, but newer versions have a header, thanks to the six unsigned 32.bit words.