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1994-08-26
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DCP v4.1 (c) 1993 by Michael Stal
The Disk Imaging and Copying Utility
alternative address:
Michael Stal SIEMENS AG
Auenstrasse 34 research & development
D-80469 Muenchen ZFE BT SE 31
Tel: +49 89 2021276 Otto-Hahn-Ring 6
Fax. +49 89 2021958 D-81739 Muenchen
Tel: +49 89 636-49380
Fax: +49 89 636-40757
Email: Michael.Stal@zfe.siemens.de
or: michael_stal@omg.org
What is DCP?
============
DCP was the first utility available for the creation of physical disk
images. Such an image contains the complete physical structure of a
floppy disk. Since images are ordinary files, you are able to backup
disks by backing up their images. You could use compression software
like pkzip or arj for the same purpose, but this would have two great
disadvantages:
(1) Archivers are not capable of storing the physical structure of a
disk, so they won't allow to keep track of bootable or copy pro-
tected disks. Another problem arises, because archivers are not
able to recognize special files (files with read-only, system or
hidden attribute).
(2) Archivers are too slow in most circumstances. If the disk to be
backed up consists of many files and subdirectories it would be a
tedious job to create or restore an image using pkzip, arj or
lharc.
DCP now includes a compression algorithm that makes image files
considerably smaller.
How does DCP work?
==================
If DCP is used to create an image file from a floppy disk, DCP will
generate a header block (with a size of 512 bytes), which contains
information like floppy disk characteristics, optional comments and
other attributes. This data is needed to retrieve the original
physical structure of a disk. The header is followed by the list of
sector contents read from the source disk. Obviously the size of an
image file depends on the floppy disk format. It can be calculated by
adding the capacity of the floppy disk to the 512 bytes used by the
header block. Therefore you should not be surprised by the fact that
the size of the generated image file must exceed the capacity of the
source disk. However, when you use the -D switch, a data-compression
algorithm will compress the image file.
Remark: For more information about the structure of DCP-files look at
the addendum of this document.
Using DCP
=========
DCP is called with the following command line:
DCP src dst [optional switches]
where you can use the following switches:
optional switches := -F
:= -D
:= -I
:= -C
:= -S=xx/x/xx
:= -V
src and dst must specify a floppy disk (A: or B:) or an image file.
Examples:
(a) DCP A: C:\MYPATH\MYFILE -D
The physical structure of the floppy disk in A: is stored in
the file named "MYFILE" using data compression.
(b) DCP C:\NYIMAGE B:
The image backed up in the file "MYIMAGE" is used to restore
the physical structure of a floppy disk. For this purpose a
diskette must be available in drive B:.
(C) DCP X: Y: or DCP X: X:
The physical structure of the disk in drive X: is copied to
the disk in drive Y:. This means that you can use DCP as a
better DISKCOPY, since there is no need to change the
source disk during the operation: DCP uses the DOS partition
to store the image of the source disk in a temporary file.
DCP will allow you to store the image to as many destination
disks as you want.
Some optional switches are available to modify the behaviour of DCP:
-C (Comment)
Set/display comment line
-D (Data Compression)
When a physical disk image is stored into a file and
the D-flag is specified, DCP will use a compression
algorithm in order to make the resulting image-file as
small as possible. DCP can automatically recognize
compressed image-files, so that you don't need to use
the D-flag for restoring physical images.
-I (Ignore)
Ignore defective sectors. Even if a disk contains
bad sectors it is often very useful to save all the
sectors (good or bad) to a image file.
-S=xx/x/xx (Specify diskette type)
Some times it is necessary to create or restore images
using floppy disks with NON-DOS formats. Usually DCP
reads the boot sector of the (source or destination)
disk to determine the disk format by the so-called
media-byte. If the media-byte contains a NON-DOS-value
DCP aborts with a message that it cannot handle this
kind of disk format. It is possible to specify the
necessary information yourself using the S-option, so
that DCP won't use auto-detection of disk formats, but
take the specified parameters instead.
-F (Do format)
In the case this switch is not specified by the user,
DCP does automatically check if the inserted diskette
is formatted. If it isn't, DCP will format it without
further user confirmation, otherwise the diskette will
not be reformatted. With the option -F the user can
force to format the disk even if it is already format-
ted.
-V (Do verify format)
Whenever a disk is formatted, DCP will not verify the
format operation per default. If you want DCP to check
for integrity, you must specify the -V option.
Additional utility DCPINFO.EXE:
The utility DCPINFO is called with the filename of a image file
as command line argument. DCPINFO checks the image and displays
its characteristics.
DCP - updates and copyright
===========================
DCP is absolutely free of charge. It may be distributed and copied
as often as you want, unless it is used for commercial products.
Any companies and institutions interested in adding DCP to their SW-
packages can contact the author for registration prices.
In contrast to other comparable utilities any new version of DCP will
work with your old DCP-files.
Suggestions, hints, ideas
=========================
If you're interested in improving and enhancing DCP according to your
own needs you are invited to send me any suggestions and ideas. I
appreciate all feedback from programmers and users. Programmers might
get a copy of the DCP source code (DCP 4.0 was written in BORLAND C++
3.1).
Future Plans:
=============
In the future there will be some additional enhancements to DCP v4.0:
- WinDCP (for MS-Windows)
- Further tools for use with DCP-files
Addendum: Structure of a DCP file
=================================
DCP-Files are structured as follows:
-----------------------------------------------
| Adress Size Description |
|----------------------------------------------
| 0 WORD number of sectors per track |
| 2 WORD number of sides |
| 4 WORD number of tracks |
| 6 BYTE comment |
| . |
| . |
| . |
| 88 BYTE major number of version |
| 89 BYTE minor number of version |
| 90 WORD data compression flag |
| 91 BYTE signature char #1 |
| . |
| . |
| 94 BYTE signature char #4 |
| 95 BYTE reserved for future use |
| . |
| . |
| . |
| 511 BYTE reserved for future use |
-----------------------------------------------
| 512 |
| |
| physical blocks of diskette |
| |
| end of file |
-----------------------------------------------
Remark (1)
The physical blocks of the diskette are read/written in the sequence
(where N specifies the number of sectors per track):
1st track
side 0 : sector_1 ... sector_N
side 1 : sector_1 ... sector_N
2nd track
side 0 : sector_1 ... sector_N
side 1 : sector_1 ... sector_N
.
.
.
last track
side 0 : sector_1 ... sector_N
side 1 : sector_1 ... sector_N
This data may be compressed.
Remark(2)
If the major version number equals 0, then the DCP-file was created
with a DCP-version smaller or equal version 2.1.
Remark(3)
The data compression flag is 0 for all DCP-versions <= 3.0; otherwise
(version >= 4.0) this flag indicates whether the stored image is
compressed or not.
Remark(4)
The DCP-signature is not set for DCP-version <= 3.0. For newer
versions it contains the null-terminated string "DCP".
///////////////////// END OF DOCUMENTATION //////////////////////////