FAT file system allows for files to be undeleted because of the way that it deletes files.

Contrary to what many people believe, deleting a file does not result in the contents of the file actually being removed from the disk. All that the system does is mark the file as deleted.

When you delete a file, the system doesn’t really delete the file. It places the hex byte code E5h into the first letter of the file name of the file. This is a special tag that tells the system “this file has been deleted”. The space that was formerly used by the file is available for use by other files, but it is not cleared. It is just sort of “left there”.

Over time, these clusters will eventually probably be reused by other files as they request more clusters for storage. However, if you accidentally delete a file you can very often recover it if you act quickly. If you run a utility like DOS’s UNDELETE or Norton Utilities’ UNERASE immediately, it can identify and recover the deleted files in a directory. As long as you provide it with the missing first character of the file name (which was overwritten by the E5h code when the file was deleted), it may be able to recover all or most of the file.

The less you do between the time the file is deleted and the time when you try to undelete it, the more likely you will be able to recover the file. Obviously, if you defragment your disk or do some other large-scale disk work, you will most likely lose the file’s contents forever. Finally, many utilities will protect your files after being deleted so they can be recovered easily without worrying about the disk space being reused. For example, Windows 95 sends all deleted files initially to its “Recycle Bin”, from which they can be restored if needed. Norton Utilities also includes a form of protection for recently-deleted files.

By PCguide
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