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What Does Microsoft's
(Win 9x)
FORMAT.COM

do to a Hard Disk?


Copyright©2004, 2007 by Daniel B. Sedory


The very first comment that should be made about MS-FORMAT is this:

A hard drive is not required to have been set up by MS-FDISK in order for Microsoft's™ FORMAT.COM to work correctly. That is an important point in trying to ascertain why MS-FDISK acts the way it does. To be specific, the F6-byte sectors that MS-FDISK writes to a drive, are never checked by the MS-FORMAT programs. At one time I had assumed that was the case, simply thinking, "Well, they must be writing all those F6-bytes so that MS-FORMAT can find them, right?" Wrong! You can just as easily use the FreeFDISK tool or even edit the MBR with a disk editor, and MS-FORMAT could care less. However, MS-FDISK itself does check that it can write to/read from a number of sectors that MS-FORMAT will be using; thus, for someone using both programs, a check has been made.

NOTE: MS-FORMAT will zero-out  the existing FAT data from any healthy (perfectly operational) FAT partition without checking any of the sectors there!

On our FDISK98 page, we began with a rather small experimental drive of 540 MB (1046 Cyl., 16 Hd., 63 Sectors), and completed the FDISK process on it. 92,260 consecutive sectors were filled with 5Eh bytes; the (^) character, so we'd know where/when FORMAT.COM writes any zero-byte sectors to the drive. The drive has 1,054,368 sectors (giving us a total size of: 514.828125 BinaryMB).

Here's what you'll see on the screen after entering the command:

Here's how that Volume Label appears in a disk editor (at the beginning of the Directory, since it was the very first item entered):

 Absolute sector 2149 (cylinder 1, head 2, sector 8)
 0000:  56 4F 4C 54 45 53 54 4E 41 4D 45 28 00 00 00 00  VOLTESTNAME(....
 0010:  00 00 94 2D 00 00 C6 0C 94 2D 00 00 00 00 00 00  ...-.....-......

The longer you wait to give your drive a volume label, such as after using SYS.COM on the drive or even after installing an OS, the further down the list of files and subdirectories you'd need to look for its entry.

In yet another test (with a different drive), I left the volume label blank and started the FORMAT command with the /S (System) switch which caused it to transfer System Files from the boot diskette to the drive volume. The FORMAT session appeared like this on my screen:

And here's how the Directory appeared after running this test:

The system files added to the drive by use of the '/S' option are shown inside the GREEN line. It should now be obvious that a Volume Label (if it exists) can appear almost anywhere in the Root Directory just like any filename found there.

 

Created: 19 DEC 2002.
Revised: 15 February 2004.
Updated: 15 May 2007.


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