Check Physical Media Defects in MS-DOS 6.22

In MS-DOS 6.22, the primary utility used to detect and mark physical media defects on storage drives is Microsoft ScanDisk (SCANDISK.EXE). Introduced to replace the more limited capabilities of CHKDSK, ScanDisk provides a comprehensive surface scan feature that reads and tests every cluster on a disk to identify damaged or unreliable sectors.

Overview of Microsoft ScanDisk

Prior to ScanDisk, the standard CHKDSK utility only checked the logical integrity of the File Allocation Table (FAT) and directory structure. It could not test the magnetic media for physical damage. ScanDisk addresses this limitation by offering two levels of analysis: a standard file-structure test and a thorough surface scan.

During a surface scan, ScanDisk reads data from each sector. If a sector fails the read or write verification, the utility flags it as a "bad cluster" within the FAT. This ensures MS-DOS will not attempt to write data to those physically compromised locations in the future. If readable data is currently trapped on a failing sector, ScanDisk attempts to recover it and move it to a healthy sector.

Running ScanDisk for Media Testing

To launch the utility interactively from the command prompt, type:

SCANDISK

This opens a menu-driven interface that prompts the user to perform a surface scan after the initial logical file structure check completes.

Command-Line Switches for Surface Scans

For direct or automated media inspection, ScanDisk can be run with specific command-line switches:

• Perform a surface scan on a specific drive:

  SCANDISK C: /SURFACE

• Scan all local drives automatically without prompting to fix errors:

  SCANDISK /ALL /AUTOFIX /SURFACE

• Perform a scan and exit automatically when done:

  SCANDISK C: /SURFACE /EXIT

Using the /SURFACE switch bypasses the prompt asking whether to perform a physical media check and immediately begins testing the storage sectors.