You can use the text editor that comes with your computer, such as Microsoft's Notepad or OS X's TextEdit. Sometimes, even if it's filled with unreadable characters, a DAT file will include some text that provides clues as to what type of file it is.  For example, if you suspect a DAT file is actually a video file, you can try to open it in a video player. If you edit a DAT file with unreadable characters and then save it, it will break the DAT file, making it unusable even if you opened it in the correct program. Make changes to the DAT file like you would any other text file, and then save the file.

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Write a summary of the previous text in Indonesian:
Buka berkas DAT menggunakan editor teks. Lihat petunjuk tentang asal-usul berkas itu. Sunting berkas DAT.