-----------------DISK STRUCTURE CONTD. 4.DATA AREA: After the root directory area finishes comes the data area. This area dose not come under system area because it dose not hold system information. The data area holds the actual file contents and subdirectory entry tables in form of clusters. The first cluster number in the data area is cluster 2 which is immediatly after the root directory area. Any damage in the data area can be fixed by marking that area as bad in FAT. There no much technical information about data area execpt that it holds the actual contents of the diskette. How to mark a bad cluster in the FAT ? weve discussed that FAT holds information about each and every cluster, so a bad cluster can be marked by changing the contents of the FAT entry corresponding to the cluster number. We know how to find the correct FAT entry byte given the cluster number. Now change the FAT entry to FF7h for FAT12 or FFF7h for FAT16. The change will look like this shown below F0__FF__FF__f7__7f__ff .. .. --> FAT12 ________^ ________| cluster 2 information F8__FF__FF__ff__f7__ff__f7 .. .. --> FAT16 ________^ ________| cluster 2 information From the above examples for FAT12 and FAT16 it is clear that cluster 2 and 3 are bad clusters since the FAT entry bytes are FF7h for FAT12 and FFF7h for FAT16. General information : Any damage in the data area can be fixed by marking it bad in the FAT but is any system area is damaged then the problem is serious. The disk may become unusable.
Posted on: Wed, 03 Sep 2014 06:55:52 +0000
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