Microsoft KB Archive/105075

= Microsoft Knowledge Base =

FastTips: MS-DOS 6.2 ScanDisk Questions and Answers
Last reviewed: November 23, 1994

Article ID: Q105075

The information in this article applies to:


 * Microsoft MS-DOS operating system versions 6.2, 6.21, 6.22

1. Q. What does ScanDisk do?

A. ScanDisk detects, diagnoses, and repairs disk errors on     uncompressed drives and DoubleSpace compressed drives. ScanDisk can repair file system errors such as crosslinked files and lost clusters as well as physical disk errors.

ScanDisk keeps a log of the repairs it makes and allows you to     undo any of the changes it makes. When you compress a drive, DoubleSpace runs ScanDisk to check the reliability of your disk before it begins compressing the drive. You can also run ScanDisk yourself by typing "scandisk" (without the quotation     marks) at the MS-DOS command prompt.

For more information, type "help scandisk" (without the     quotation marks) at the MS-DOS command prompt and then press ENTER.

2. Q. ScanDisk found and repaired an error on my hard disk drive during the surface scan, but not all of the affected file was fully recovered. What happened to my file?"

A. When ScanDisk encounters a bad sector in a file, it repairs the file by mapping in a new sector. Because the data in the original sector is unreadable, ScanDisk fills the new sector with zeros. This repair makes the file fully readable, but any data that was in the defective sector is still lost.

If you have a data file that was repaired by ScanDisk, your application usually can read most of the file. If a program file was repaired, you should restore the file from the original program disks. For more information, contact your software vendor.

3. Q. Why does ScanDisk perform a surface scan on my compressed drive when it has just finished scanning the host drive? Is it really necessary to perform a surface scan on both drives?

A. There is a difference between a surface scan on a compressed drive versus a host drive. To thoroughly check the drives, the surface scan should be performed on both the compressed drive and its host.

When ScanDisk performs a surface scan on a uncompressed drive, it is checking the physical integrity of each sector on the drive. When ScanDisk performs a surface scan on a compressed drive, it is verifying the data on the drive can be uncompressed without error.