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1989-11-26
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Interior File Listing Utility 11/26/89 Version 1.50
IFL
Interior File Listing Utility
Copyright 1989 by Martin Pollard. All rights reserved.
This program may be freely copied and distributed, provided it is for
personal, non-profit use only. I am asking for no monetary donations;
thus, this program is truly Freeware. I only ask that, if distributed,
the program and documentation not be altered in any way. Your
cooperation with this simple request will be an incentive for newer and
better versions of this program.
Although I have tried to make this program as bug-free as possible, I
will not be liable for any damages caused, either directly or
indirectly, by the use of this program. This program is distributed
without warranty, either expressed or implied.
NOTE: Throughout this documentation, the term "archive file" is used
to describe any file that contains multiple files. Likewise,
the term "archiving program" is used to describe any program
that creates and/or maintains an archive file.
If you encounter any problems while using the program, or if you have
any suggestions to improve the operation of IFL, you may contact me at
any of these bulletin board systems (leave messages to "Silicon Wizard",
my handle):
The Pointe BBS Warp Speed BBS
313-885-1779 313-544-0405
300/1200/2400 baud 300/1200/2400 baud
24 hours 8pm to 8am nightly
or drop me a line through the mail to 27825 Hoover, Apt. 4, Warren, MI,
48093. Please include a self-addressed stamped envelope to ensure a
speedy reply. Letters that do not include an SASE will not necessarily
be ignored; they just won't be replied to as quickly!
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Interior File Listing Utility 11/26/89 Version 1.50
A SHORT HISTORY OF ARCHIVING PROGRAMS
What exactly is an archiving program? It is a program that takes a
group of files and stores them into one single file, called an archive
file. Such an archiving program may or may not compress the files
before storing them in the archive file. (Compression means to read the
file, perform mathematical and probability calculations on the data --
which can be either text or binary data -- and write a new file
containing the compressed information.)
The first of these kinds of programs originated under the CP/M operating
system. They were LU, SQ and USQ, which stood for Library Utility,
Squeeze, and Unsqueeze. LU was a very primitive archiving program: It
simply took files and placed them into an archive file (LU called them
"library" files), with no compression performed on the data at all. The
SQ program was usually used to compress files before they were stored by
LU. (SQ used a method call Huffman encoding to compress the
information. USQ, as you may have guessed, simply reversed the
process.) LU-created files can usually be identified by the ".LBR"
extension (although this was not required; the .LBR extension was
usually used to maintain consistency) or the ".LQR" extension (if the
library file was squeezed AFTER files were stored in it). For years,
the combination of LU, SQ and USQ -- and its derivatives -- were the
best thing since sliced bread.
When the IBM PC appeared, these programs were, naturally, ported over to
the MS-DOS operating system. However, users quickly felt the
limitations of LU, SQ and USQ. These programs were originally written
for slow 8-bit 8080- and Z80-based systems with a maximum of 64K of
memory; the 16-bit 8088-based IBM PC was faster by comparison, and could
access up to 640K of memory. Users figured there HAD to be a better
way.
System Enhancement Associates (SEA) came up with the better mousetrap
with ARC, which essentially combined the functions of LU, SQ, and USQ by
compressing files before storing them in the archive file. Even here,
ARC took a different approach, replacing LU's fixed directory (which was
at the beginning of each library file) with a "distributive" directory
(files stored in the archive are preceded by a "header" describing the
file in detail). Over the years, ARC has been improved with more user
options and more advanced compression methods (like Dynamic Lempel-Zev-
Welch, or "Crunching"), and has been ported to other operating systems
(such as UNIX and VAX).
Unfortunately, ARC had the big problem that plagued the early CP/M
programs: It was very slow, especially on 8088-based systems. To solve
this, Phil Katz of PKWARE created PKARC, an ARC "clone" that was so fast
that it began to surpass ARC in popularity. Later enhancements to PKARC
also included a Dynamic LZW variant called "Squashing". The combination
of all these features catapulted PKARC right to the "top of the charts,"
as it were. (PKARC was later renamed to PKPAK.)
SEA filed a lawsuit against PKWARE in 1988, charging unlawful use of
ARC's source code and unfair business practices. (The details of the
-- 2 --
Interior File Listing Utility 11/26/89 Version 1.50
lawsuit have been discussed elsewhere, so I will not go into them here.)
The out-of-court settlement between Phil Katz and SEA ended production
of PKARC; unfortunately, it also alienated many users and bulletin board
system (BBS) operators. (The feeling was that SEA was trying to "win in
the courtroom" because it was losing to PKARC in the marketplace.) That
action, plus the rapidly-growing shift to PKZIP and LHARC, has probably
spelled the end of the ARC format, despite SEA's release of an improved
version of ARC.
In the midst of the scuffle between SEA and PKWARE, NoGate Consulting
released its own ARC-compatible program called PAK. PAK uses an even
more advanced Dynamic LZW variant dubbed "Crushing" (later versions
introduced another compression method, "Distilling", which gives PKZIP
and LHARC a run for their money). PAK has created a sizable following
of users, but has not caught on for two reasons: It is slower than
PKARC, and the new compression methods, plus the various "enhancements"
to the ARC format, make it incompatible with programs that process ARC
files.
After the lawsuit that ended production of PKARC, PKWARE introduced a
totally new compression program, PKZIP. PKZIP, with its enhanced file
format (including a second directory to assist in recovery of corrupt
archives) and enhanced compression methods (tighter than almost all
current archiving programs), has gained a large following. Animosity
towards SEA, and the widespread popularity of PKARC, have also helped
tremendously.
Along with the main contenders, three other archiving programs exist
that have each gained their own following of users: DWC by Dean W.
Cooper, LHARC by Haruyasu Yoshizaki, and ZOO by Rahul Dhesi. DWC was
introduced around the time of ARC's period of popularity, but due to an
incompatible file format, it was never accepted i