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1990-07-03
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======================= CompDisk & DecompDisk ========================
======================================================================
CompDisk & DecompDisk © Copyright 1990 by MXM, written by Olaf
Barthel. We make no guarantees that the programs CompDisk &
DecompDisk are fully reliable and your data will be 100% safe. Use
use these programs on your own risk!
============================ Hintergrund =============================
======================================================================
At present, more than enough programs exist which compress the
contents of entire disks. The resulting files are either amazingly
short or take ages to create (so not all that glitters seems to be
gold). Here's another program of this kind that's waiting to be used
by you.
This program does not try to:
- Work three hours on a single disk to produce an output file of
thirteen bytes in size.
- Reproduce long tracks, exotic synchronizing formats or other copy
protections 1:1.
- To force the user to get along with a complex user interface.
If you expect this program to have these features, you will have to
rewrite parts of the accompanying source code or to delete the
programs.
============================ Features ================================
======================================================================
Both programs will operate from Shell, as well from Workbench.
Unfortunately the Lattice Arp support code cannot create 'pure'
programs; 'ARes' will still make them resident, but a second call to
one of them will report a checksum error. Both programs use functions
to be found in arp.library and req.library, they need to be present in
your current LIBS: directory.
CompDisk and DecompDisk use the Lempel-Ziv algorithm for data
compression/decompression. Disks are read and compressed track by
track (0-79) to usually about 50% of their original size. If a track
doesn't become smaller during the compression, it is stored 'as is'.
A 16-bit CRC checksum is calculated over each track. During
decompression the checksum is verified. If it doesn't match the
original value, an error message will be displayed.
To speed up compression, unused blocks will be zeroed (note:
this can be turned off).
In worst cases disk compression takes about six minutes,
decompression four minutes. Standard values for compression are
between three and four minutes.
Note: Files created by CompDisk aren't compatible with any
other disk compression utilities. DecompDisk will not be able to read
the output files of other utilities either.
=============================== Usage ================================
======================================================================
If called from Shell, CompDisk and DecompDisk will accept the
following parameters:
FILE .......... The name of the file to be created/decompressed.
DRIVE ......... The disk drive (DF0: - DF3: or RAD:) to read the
data to be compressed/to write the decompressed data
to. At present only the four drives mentioned above
are supported.
NOCLEAR ....... Only the program CompDisk supports this switch. If
selected, unused disk blocks will not be cleared.
If started from Shell, both programs will not open req.library.
Double-clicking the icon of either program will bring up a window
containing six gadgets:
Stringgadget... The name of the path to create the output files at
(e.g. RAM:, DH0:, etc.). DecompDisk will display the
name of the file currently decompressed in the gadget.
Drives......... Here the disk drive to be read is to be selected.
CompDisk will wait for you to select the drive before
you insert the disk. DecompDisk wants you to insert
the disk first before you click on the drive in which
you have inserted it.
If possible, CompDisk will create an icon for each disk it compresses.
To decompress the resulting file from Workbench, this icon must not be
deleted.
A file is decompressed from Workbench by double-clicking its
icon or holding down the shift-key, selecting its icon and
double-clicking the icon of DecompDisk.
We strongly recommend to run both programs on an Amiga with
accelerator-board. On an A2000B with 33 MHz GVP-68030 board CompDisk
will take about 1.07 minutes to compress a whole disk (which takes
about as much time as 'DiskCopy DF0: to RAD:'.
================== Author's request, copy fee, etc. ==================
======================================================================
It took more blood, sweat and tears to develop these programs than we
had expected. If you like them and use them frequently send at least
US$ 10 or DM 15,- to
Olaf Barthel, MXM
Brabeckstraße 35
D-3000 Hannover 71
CompDisk & DecompDisk are SHAREWARE and must not be sold commercially.
A small copy fee is still allowed. Inclusion of one or both programs
in a Public-Domain software selection (which seems to be quite popular
in Germany -> you usually pay too much for a lot of old junk) must be
arranged with us.
============================== Credits ===============================
======================================================================
Credits go to Arp Programmers for Arp 1.3, Stephen Satchell & Chuck
Forsberg for the 16-Bit CRC-routines, Bruce Dawson & Colin Fox for
req.library and last but not least to the author(s) of the
compression/decompression routines whose name I could not discover in
the source code.
============= Program history (most recent change first) =============
======================================================================
V1.6 First international release.
V1.0 Before written history.