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Using a diskeditor

Posted on 1998-09-10
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I want to get some experience with using a diskeditor, for example that of Norton Utilities. Is there any workshop or howto or even collection of tips available?
Thanks for answer.
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Question by:mitoda
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by:mitoda
ID: 1010430
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mark2150 earned 100 total points
ID: 1010431
If you are going to use a disk editor you need to have a through understanding of the structure of FAT type disks. Peter Norton has writting several books about DOS and disk internals and Que has a DOS programmers reference guide that analyzes FAT structures byte-by-byte.

If you're going to tinker with a disk editor *PRACTICE ON FLOPPYS*.

It is *VERY* easy to destroy a disk, if you drill a hole in your hard drive you will be well and truely hosed. (I had a friend who was tinkering with a program and inadvertantly wrote sequential data to his HD FAT - this linked the entire drive into ONE LARGE FILE! - no recovery except from backup!)

You can practice with floppies as their structure is the same as the HD with the exception of the cluster size being small. You can also make bootable floppies that are essentially identical to bootable HD's.

If you have to do HD experiments, add a 2nd drive and work on THAT so your primary disk won't get clobbered when you screw with the partition data.

If your system is windows based you'll have to shut down to DOS and run LOCK to allow you low level access to the drive.

M

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by:mitoda
ID: 1010432
Thankyou mark2150 for your comment.
Of course I know that it is dangerous and could lead to data loss.
But what I wanted to know is: is there any step by step introduction for a first experience available, may be with examples how to handle special tasks or problems. May be this could be got online too. Or how to manage the first steps? Besides knowledge about FAT, are there others absolute conditions?
Thanks.

m
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by:mark2150
ID: 1010433
FAT knowledge *IS* the key to how the disk operates. It's really not that complex. The FAT is a table of the clusters and each cluster's entry tells if it's used, free, bad, etc. Files are chains of clusters. The Directory is a reserved area with a file name, time/date stamp, flags, and pointer to first cluster. Each cluster has pointer to next. That, in a nutshell, is that.

You get into Clynder/head/sectors and such, but overall the disk structure is fairly straight forward. I'ts a real thrill the first time you manually recover an "erased" file by changing the first char of the file name and *pow* the file is back!

The exact "step by step" process depends on what you're trying to learn. I've manually gone into the FAT and marked a cluster BAD and then seen it appear that way on DEFRAG. You can rename files by editing the directory entries and changing the attribute flags - fun stuff. Chase a file across the disk from the directory entry to the tail, one cluster at a time.
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