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Date:         Thu, 21 Jan 1993 15:43:13 -0600
From:         Cliff Manis <cmanis@CSOFTEC.CSF.COM>
Organization: CompSofTech, POB 33937, San Antonio, Texas 78265-3937
Subject: GENEALOG: New File: comp430d
Comments: To: Genealogy Information <ROOTS-L@VM1.NoDak.EDU>

I have just uploaded the following GENEALOG files:

  GENEALOG comp430d     Compress/Decompress of the .Z files


This is a UUENCODED and ZIPPED - DOS file and is available now.

I have also downloaded the file which I uploaded, and it works.  If you
have a problem in reading the attached docs then have a friend
help you.  This program will uncompress the files which were just
announced available via ftp about the Census in the British Isles.
I only post it, but do not guarantee it.  I have had it on this
system for about 1 year.

See end of this message for a description of the file.

GENEALOG is an area on the LISTSERV computer which is used for storage
of many, many textual files which pertain to genealogy.

You may request a listing of the file be mailed to you by simply
sending the following line to: LISTSERV@vm1.nodak.edu as the only
text of a message.

/files roots-L

It normally only takes about ten minutes for the LISTSERV computer to
reply, sending you a message with the entire listing of files.

(Please note, there is NO SPACE between the slash and the word files)

You may pick & choose the filenames of interest and to request
a file just simply send the following line back
to: LISTSERV@vm1.nodak.edu as the only text of a message.

GET GENEALOG filename

   (please replace the "filename" with the filename of interest)


Below is the "documentation" that comes with the program.  I don't
know who wrote it.  This is the way I received it about 1 year ago.

/docs below/

COMPRESS 1 local

NAME compress, uncompress, zcat - compress and expand data

SYNOPSIS

     compress [-cCdDf?hkKvV][-b maxbits][-Iinpath][-Ooutpath][filenames...]
     uncompress [-fCcvVkK?h][-Iinpath][-Ooutpath][filenames...]
     zcat [-CvV?h][-Iinpath][-Ooutpath][filenames...]

     Argument Processing..case is significant:
     MUST use '-' for switch character, all flags are optional.

     [options]
     -V => print Version
     -d => do_decomp default = off
     -v => verbose
     -f => force overwrite of output file default = off
     -n => no header: useful to uncompress old files
     -c => cat all output to stdout default = off
     -C => generate output compatible with compress 2.0
     -k => %s input file, default = keep
     -K => %s output file on error, default = kill
     -b maxbits  => default = 16  bits
     -I pathname => infile path  = none
     -O pathname => outfile path = none
     -? -h => help, print full usage message

DESCRIPTION

This is the MS-DOS executable version 4.3d of compress don release.
Compatible with release joe, version 4.0 compression.  This version
supports 16 bits.  Works with DOS 2.x, but on 3.x+ it will understand
the program name and set defaults.  Otherwise, must use options.
Rename file to compress.exe.  Copy to zcat.exe and uncomp.exe for
auto recognition features.  This version supports full UNIX option
compatibility.

The compression and decompression routines are modified from the current
version 4.0 joe release.  However, the compressed output is cross compatible.

Compress reduces the size of the named files using adaptive Lempel-Ziv coding.
Whenever possible, each file is replaced by one with the extension .Z,
while keeping the same ownership modes, access and modification times.
If no files are specified, the standard input is compressed to the
standard output.Compressed files can be restored to their original form
using uncompress or zcat.

The -f option will force compression of name. This is useful for compressing
an entire directory, even if some of the files do not actually shrink.
If -f is not given and compress is run in the foreground, the user is
prompted as to whether an existing file should be overwritten.

The -c option makes compress/uncompress write to the standard output;
no files are changed.  The nondestructive behavior of zcat is identical
to that of uncompress -c.

Compress uses the modified Lempel-Ziv algorithm popularized in
"A Technique for High Performance Data Compression", Terry A. Welch,
"IEEE Computer," vol. 17, no. 6 (June 1984), pp. 8-19.

Common substrings in the file are first replaced by 9-bit codes 257 and up.
When code 512 is reached, the algorithm switches to 10-bit codes and
continues to use more bits until the limit specified by the -b flag
is reached (default 16). Bits must be between 9 and 16.  The default can
be changed in the source to allow compress to be run on a smaller machine.

After the bits limit is attained, compress periodically checks the compression
ratio.  If it is increasing, compress continues to use the existing code
dictionary.  However, if the compression ratio decreases, compress
discards the table of substrings and rebuilds it from scratch.  This allows
the algorithm to adapt to the next "block" of the file.

Note that the -b flag is omitted for uncompress, since the bits
parameter specified during compression is encoded within the output,
along with a magic number to ensure that neither decompression of random
data nor recompression of compressed data is attempted.

The amount of compression obtained depends on the size of the input, the
number of bits per code, and the distribution of common substrings.
Typically, text such as source code or English is reduced by 50-60%.
Compression is generally much better than that achieved by Huffman coding
(as used in pack), or adaptive Huffman coding (compact), and takes less
time to compute.

Under the -v option, a message is printed yielding the percentage of
reduction for each file compressed.

If the -V option is specified, the current version and compile options
are printed on stderr.

DIAGNOSTICS
        Usage: compress [\-dfvcV] [\-b maxbits] [file ...]
                Invalid options were specified on the command line.

--
Cliff Manis            K4ZTF           Manis/Manes Family History
Researching: MANIS MANES MANESS MANAS WHITEHORN CANTER BIRD CORBETT NEWMAN
    USMAIL:   P. O. Box 33937, San Antonio, Texas  78265-3937
               INTERNET: cmanis@csoftec.csf.com
Standard Disclaimer:  We are not associated with anyone. (PERIOD). (.)
--
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU