The .pde file is the source code in Processing, a dialect of Java that simplifies writing applets.

The .java file is Processing's translation or wrapping in Java.

The .jar file is the compiled applet.

The data directory contains a font and an image used by the applet. It must be in the same directory as the .jar file to run the applet.

$line\n";
   } else {
      echo "$line\n";
   }
}
?>

This ls -l style index was made with a php script.