Definition - What does ScanDisk mean?
ScanDisk is a DOS utility application used to check and correct errors on hard and floppy disks. It was first shipped in DOS 6.2 and was included with Windows 95, 98 and ME.
The utility scans disk surfaces for defects and marks those sections to prevent the rewriting of data and data loss. ScanDisk saves recovered lost clusters as .chk files.
Techopedia explains ScanDisk
Microsoft originally purchased ScanDisk from Symantec (formerly known as Norton). At the time, ScanDisk was packaged for use in Microsoft's DOS and Windows systems. It is no longer shipped in post ME versions of Windows, as ScanDisk is not able to check new technology file system (NTFS) disk drives, which became increasingly common in computer systems running post ME versions of Windows. ScanDisk's close cousin, CHKDSK, which has similar functions and can check NTFS disks, is still used and has shipped with each version of Windows, to date (Windows 8).
ScanDisk is automatically activated when rebooting a computer that is not properly shut down, or if it detects initial disk problems from the Power On Self Test (POST).