| The Windows 9x space allocation system (not to | | | | hardware damage in one part of the disk, these |
| mention DOS) is the File Allocation Table (FAT). | | | | are sector not found errors. |
| The FAT and the directory structures enables | | | | These can be rectified by telling the disk to ignore |
| Windows (and DOS) to keep track of the data | | | | that area and reloading backup of files affected in |
| stored on the disk and where and how that data | | | | that area. There is no assurance that you can |
| is stored. FAT troubles are tasks for CHKDSK | | | | recover data that has been "cratered" from that |
| programme. | | | | area. |
| CHKDSK and Scan Disk are similar, but CHKDSK | | | | Further actions of the CHKDSK are as follows: |
| checks the FAT file counting bad clusters and | | | | (a) It counts up the available clusters, used |
| multiplying the bad clusters by the number of | | | | clusters and bad clusters. |
| bytes per cluster. It then reports the number of | | | | (b) It searches the directory structure to ensure |
| bad bytes on the hard disk. While Scan Disk | | | | that it makes sense and all subdirectories have |
| performs surface testing of the Disk. | | | | the proper format for example the *.* and "." files |
| The easier of problems are those directory or | | | | must be in place examining the entire subdirectory |
| FAT related such as where the directory or FAT | | | | tree. |
| has been damaged or where a file has been | | | | (c) It examines all files directory entries and FAT |
| mistakenly deleted. A deleted file can be undeleted | | | | chains. The directory entry records how many |
| while a formatted disk can be unformatted. | | | | clusters a file uses. Those two numbers must |
| You can rectify these problems by manipulating | | | | agree. There have to be enough clusters allocated |
| the FAT and/or directory structure without | | | | in the FAT to accommodate the number of |
| touching the data. However problems that are | | | | bytes referenced in the directory. |
| difficult to repair are problems that come from | | | | |