PIBLZW.ARC contains two Turbo Pascal v4.0 programs which implement
the Lempel-Zev-Welch (LZW) compression technique:
PIBCOMPR.PAS --- Compresses files using LSZ
PIBDCOMP.PAS --- Decompress files compressed with PIBCOMPR.PAS
In addition to those two files, PIBLZW.ARC should also contain these
PIBLZW.DEF --- Common global declarations for PIBCOMPR/PIBDCOMP
PIBLSZ.INC --- Common routines for PIBCOMPR/PIBDCOMP
README.1ST --- This file you're reading now.
The LZW technique is well explained in the following reference:
"A Technique for High Performance Data Compression",
Terry A. Welch, IEEE Computer,
vol. 17, no. 6 (June 1984), pp. 8-19.
Variants of LZW compression are used in the popular Unix and VMS COMPRESS
utilities and the MS DOS "ARC" utilities, among others.
PIBCOMPR.PAS and PIBDCOMP.PAS are not meant to be highly efficient
production codes. These programs are designed to illustrate the basic
LZW technique using Turbo Pascal, following the Welch reference above.
Once you understand the basic algorithm, you should be able to understand
the variable bit size and adaptive compression variants of LZW which
are used by more sophisticated programs.
Also note that these routines as they stand cannot be used to extract
files from MS-DOS ".ARC" files.
RESTRICTIONS ON USE
You may use these programs for any purpose whatsover; I am contributing
them to the public domain. If you do adapt these routines for use in
your own programs, I'd appreciate your mentioning that.
ADDRESSES FOR ELECTRONIC LETTER BOMBS
You may leave me messages on the following BBSs:
Gene Plantz's BBS (312) 882 4145
Northwestern Univerity OPUS BBS (312) 491 3892
Gene's BBS is registration only ($25 a year) and well worth it.
The Northwestern University BBS is run by my colleague Roger Safian.
You can use the OPUS/FIDONET remote mail/networking facility to send me
messages from another OPUS local to your dialing area. The net address
of Roger's OPUS BBS system is 115/419.
For all three BBS systems, my user name is PHILIP BURNS.
CompuServe users can reach me at:
University users can reach me at: [email protected]
(BITNET) [email protected]
-- Phil "Pib" Burns
April 30, 1988.