---

About Validity(chkdsk)Command...

---

The DOS function chkdsk analyzes a FAT-12 disk and reports any problems.  You should use chkdsk to validate your file manager implementation.  Here are some checks and error messages that the chkdsk program will look for:

·        lost chains – Allocated sectors not belonging to any directory or file.

·        cross-linked chains – two entries in the FAT table are "pointing" to the same cluster.

·        invalid directory entry

• invalid name – directory entries padded with zeros instead of spaces or lowercase.
• invalid extended attribute handle – "reserved" field of directory entry not zeroed out.
• invalid attribute – combination of attribute bits not recognizable.
• invalid date – date in future (or before 2000).
• invalid file size – file size impossible or file size 0 with non-zero start cluster.
• invalid file start cluster – start cluster out of bounds.
• zombie long name directory entry – long short names differ.

·        invalid directory

• dot/dotdot invalid – dot or dotdot entries invalid or missing.
• invalid format – directory entries after “last” entry.

·        improperly formatted disk

• invalid boot sector – corrupted data or constants.
• invalid fat tables – fat tables have not been or cannot be reconciled.