Low Level Format

From: Fred N. van Kempen <waltje_at_pdp11.nl>
Date: Mon Aug 25 15:08:00 2003

On Mon, 25 Aug 2003, chris wrote:

> I've used /Q when formatting hard drives as well. I think it does pretty
> much the same thing as when formatting a floppy with /Q, it just zaps the
> FAT and goes under the assumption that the drive format itself is good.

DOS Format tries to READ every sector (in bunches of clusters) so it
can tell which clusters are to be marked BAD. That is why it takes
so long to format a disk under DOS.

Starting with (I believe) 4.0, DOS added the volume serial number biz,
and options to ease un-recovery of deleted files, as has been stated
before. These include keeping a copy of the root dir and FAT around
towards the end of the disk[partition], and a change in allocating
directory entries (from overwriting the first "available" one to
the first one that was not previously deleted; if available).

The /U specifier to Format changes this back to the old behavior,
meaning, just read all sectors, and dont try to keep the FAT and
root dir around.

There is some changing behavior between versions with regard to
formatting a previously formatted drive... some versions will take
on the previous format (and "skip" to using "new style" format),
others really do the /U, even when a valid format is already there.

cheers,
        Fred
Received on Mon Aug 25 2003 - 15:08:00 BST