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BFormat4.lha
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1991-02-11
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BFormat, Version 4.0
Purpose
-------
Normally, AmigaDos only allows the formatting of 'perfect' diskettes.
If you have a formatting error anywhere on the diskette (it may only
be a single track that appears to be bad) AmigaDos will kindly inform
you that the disk is totally un-useable. I never felt comfortable with
that limitation. I had hoped that Dos 1.2 would address this problem
Bformat allows for the formatting of any track disk type device as
long as it is mounted. Therefore, it now supports:
* Fast File System.
* Any Type of Floppy Diskette.
* Hard Drive Partitions.
* RAD: devices.
Limitations
-----------
Bformat does require the ability to successfully format the first
track of the named partition (track 0 on a floppy) and the middle
track of the partition (track 80 on a 3.5 inch floppy). Disks with
formatting errors on tracks other than these should pose no problems.
Bformat only works on any specified drive. At this time Bformat is
only executable from the CLI environment.
As in the case of AmigaDos' Format, any formatted device looses all
data and is unrecoverable. Therefore, use the BFormat program
carefully.
How it Works (overview)
-----------------------
Bformat uses the standard device ('trackdisk.device' for floppies)
calls for disk formatting. After a device is formatted 3 important
blocks are written to the disk. The first block written is what I will
call the 'ID' block (block 0). In order for AmigaDos to recognize the
disk as useable for file storage, the first three bytes must contain
the ascii codes for 'DOS', followed by either a \0 or \1 to indicate
the file system type. The second block required by Dos is the 'root'
block in the middle of the device. This block contains information on
the disk file structure, as defined in the AmigaDos Manual. The third
block required is the 'Block Allocation Map' (bam). The physical block
number for this map can vary and is obtained as a pointer from the
'root block'. The bam is a bit-mapped structure which defines all of
the available blocks on the disk. When files are created by AmigaDos,
it adjusts the content of this map to reflect which blocks are used by
the file system. (More info on the bitmap is present in the source
code). Bformat works by dynamically creating this bitmap structure.
When Bformat comes across a block that cannot be correctly formatted,
it marks this block as 'in use'. Since the blocks marked by Bformat
are not attached to any AmigaDos file, the AmigaDos file system will
not attempt to use these 'bad' blocks. Bformat effectively hides any
bad blocks from AmigaDos.
Usage
-----
BFormat DRIVE <drive> NAME <name> [FFS|NOFFS] [FAST|QUICK|SLOW] [QuIeT]
The FFS and NOFFS options pertain to the file system specified as in
use, by the mountlist entry. The FFS option marks the disk as being
used with the FastFileSystem. The NOFFS option marks the disk as
being used with the default file system. Since BFormat checks to see
if an alternate file system is specified, the the FFS option is
automatically used. If another file system is in the MountList, the
NOFFS option is used.
The FAST, QUICK and SLOW options pertain to the type of verification
to be performed. Fast reads only the first sector of each track and
is therefore the fastest. It can be accurately used with floppies or
Rad: type devices. The Quick option instructs the verification
routine to read all data on every track. This option should be used
with hard-disks at minimum. The Slow option writes and verifies
every track with four different patterns. This is the most robust
verification, but also is quite slow.
The QuIeT option allows the formatting of devices with no requests for
verification or progress indication. Use this option carefully. It
was included to allow the formatting of Rad: devices in the startup-
sequence, automatically. Due to the risk of using this option, the
case of the option is important and was chosen to make the invocation
as safe as possible.