A system file in computers is a critical computer file without which a computer system may not operate correctly.[1][2] 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. (The system attribute can be manually put on any arbitrary file, but setting the system attribute n a file does not cause the file to become a system files)
Specific example of system files include the files with .sys filename extension in MS-DOS and Windows. In Windows NT family, the system files are mainly under the folder C:\Windows\System32. In the classic Mac OS they are in the System suitcase. In Unix-like systems the system files are located in the folder / or under folders such as /boot (Linux), /System/Library (macOS), /sbin and /usr/sbin (system utilities) and /usr/lib/modules (Linux loadable kernel modules).
References
- ^ “System Files”. www.ibm.com. Retrieved 2025-10-30.
[…] system files. These files are created and maintained by the operating system and are necessary for the system to perform its many functions. System files are used by many commands and subroutines to perform operations. These files can only be changed by a user with root authority. […]
- ^ “Use the System File Checker tool to repair missing or corrupted system files – Microsoft Support”. support.microsoft.com. Retrieved 2025-10-30.
When critical Windows system files are missing or corrupted, some Windows features may stop working correctly or Windows may stop responding altogether.