Closed-loop systems are able to correct in order to meet target results. Normally a sensor is used to look at the output and adjust the process accordingly. This is called feedback.
A file with an extension of .DAT is known as a Data (General). These .DAT files can be opened on Windows and Apple using programs ...
Since most DAT files are tucked away from view in an application's data folders, you'll probably see DAT files most often if a video file is being stored this way, or if you've received a malformed email attachment with the extension.