System file

A system file in computers is a critical computer file without which a computer system may not operate correctly. These files may come as part of the operating system, a third-party device driver or other sources. Microsoft Windows and MS-DOS mark their more valuable system files with a "system" attribute to protect them against accidental deletion. (Although the system attribute can be manually put on any arbitrary file; these files do not become system files.)

Specific example of system files include the files with  filename extension in MS-DOS. In Windows NT family, the system files are mainly under the folder. In Mac OS they are in the System suitcase. And in Linux system the system files are located under folders  (the kernel itself),   (system utilities) and   (kernel device drivers).