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Check Disk is a system tool provided in Windows, OS/2 and DOS to verify the file system integrity of a volume as well as for fixing logical file errors. Similar to the fsck command in UNIX, it also helps in checking damaged sectors in a physical disk and recovers data from them.
For the Check Disk tool to be used, the autochk.exe file needs to be present in the computer system. In most operating systems, admins have the options for what switches to execute with the Check Disk command. The main functionality of Check Disk is to ensure the system or administrative information regarding files, folders and similar data stored in a physical disk is correct. Most operating systems are designed to ensure this information is correct from start to shutdown of the computer. However, improper shutdown of the machine, removal of USB devices without safely removing them as well as malware or hardware errors could cause this information to be corrupted. In such cases, Check Disk steps in to sort out the errors and fix them. It performs an analysis and repairs errors on disks which are not in use. For disks which are in use, such as the C: drive in most Windows operating systems, Check Disk provides a prompt asking for permission to schedule the procedure for the next time the system is restarted. If the answer is Yes, the Check Disk is performed at the start of the next system run.
One of the many methods by which Check Disk locates errors is by making use of a volume bitmap with the disk sectors allocated to files. However, Check Disk is incapable of repairing corrupted data which appear to be structurally intact. If the /r command is used with Check Disk, it looks for and recovers any readable data in the disk’s bad sectors. If the /f command is used with Check Disk, it fixes any errors it finds.