Einleitung
ARC
File Archive Utility
Version 5.20
(C)COPYRIGHT 1985,86
by
System Enhancement Associates, Inc.
ALL RIGHTS RESERVED
This document describes version 5.20 of the ARC file
utility, which was created by System Enhancement
Associates, Inc. in October of 1986.
TABLE OF CONTENTS
Section Page
Introduction .................................... 1
Using ARC ....................................... 3
ARC commands .................................... 5
Adding files ................................ 5
Extracting files ............................ 7
Deleting files .............................. 8
Listing archive entries ..................... 8
Running files ............................... 10
Printing files .............................. 11
Testing an archive .......................... 11
Converting an archive ....................... 12
ARC options ..................................... 13
Suppressing compression ..................... 13
Backup retention ............................ 14
Message suppression ......................... 15
Encryption/Decryption ....................... 17
RAMdisk support ................................. 18
MARC ............................................ 19
ARCE ............................................ 20
Version numbers ................................. 21
Common questions and answers .................... 22
Maintenance contracts ........................... 24
Revision history ................................ 25
Changes in version 3 ........................ 25
Changes in version 4 ........................ 25
Changes in version 4.1 ...................... 26
Changes in version 4.3 ...................... 26
Changes in version 4.4 ...................... 27
Changes in version 4.5 ...................... 27
Changes in version 5.0 ...................... 28
Changes in version 5.1 ...................... 29
Changes in version 5.2 ...................... 30
Program history and credits ..................... 31
Bulletin boards ................................. 33
Site licenses ................................... 34
INTRODUCTION
ARC is the copyrighted property of System Enhancement
Associates, Inc. You are granted a limited license to
use ARC, and to copy it and distribute it, provided
that the following conditions are met:
1) No fee may be charged for such copying and
distribution.
2) ARC may ONLY be distributed in its original,
unmodified state.
3) ARC may *not* be distributed, in whole or in part, as
part of any commercial product or service without
the express written permission of System
Enhancement Associates.
Contributions for the use of this program will be
appreciated, and should be sent to:
System Enhancement Associates, Inc.
21 New Street, Wayne NJ 07470
You may not use this product in a commercial
environment or a governmental organization without
paying a license fee of $35. Site licenses and
commercial distribution licenses are available. A
program disk and printed documentation are available
for $50. See the order form enclosed with this manual
for more details.
ARC is user supported software. This means that you
may copy it freely and give the copies away to anyone
you wish, at no cost. They are in turn requested to
send in a contribution if they decide to use it.
The user supported software concept (often referred to
as "shareware") is an attempt to provide software at low
cost. The cost of offering a new product by
conventional means is staggering, and hence dissuades
many independent authors and small companies from
developing and promoting their ideas. User supported
software is an attempt to develop a new marketing
channel, where products can be introduced at low cost.
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If user supported software works, then everyone will
benefit. The user will benefit by receiving quality
products at low cost, and by being able to "test
drive" software thoroughly before purchasing it. The
author benefits by being able to enter the commercial
software arena without first needing large sources of
venture capital.
But it can only work with your support. We're not
just talking about ARC here, but about all user
supported software. If you obtain a user supported
program from a friend or colleague, and are still
using it after a couple of weeks, then it is obviously
worth something to you, and a contribution should be
sent.
And now, back to ARC:
ARC is used to create and maintain file archives. An
archive is a group of files collected together into
one file in such a way that the individual files may
be recovered intact.
ARC is different from other archive and library
utilities in that it automatically compresses the
files being archived, so that the resulting archive
takes up a minimum amount of space.
When ARC is used to add a file to an archive it
analyzes the file to determine which of three storage
methods will result in the greatest savings. These
three methods are:
1) No compression; the file is stored as is.
2) Repeated-character compression; repeated sequences
of the same byte value are collapsed into a three-
byte code sequence.
3) Dynamic Lempel-Zev compression; the file is stored
as a series of variable size bit codes which
represent character strings, and which are created
"on the fly".
Note that since one of the three methods involves no
compression at all, the resulting archive entry will
never be larger than the original file.
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USING ARC
ARC is invoked with a command of the following format:
ARC x arcname [template . . .]
Where:
x is an ARC command letter (see below), in
either upper or lower case.
arcname is the name of the archive to act on,
with or without an extension. If no extension is
supplied, then ".ARC" is assumed. The archive
name may include path and drive specifiers.
template> is one or more file name templates.
The "wildcard" characters "*" and "?" may be used.
A file name template may include a path or drive
specifier, though it isn't always meaningful.
If ARC is invoked with no arguments (by typing "ARC",
and pressing "enter"), then a brief command summary is
displayed.
Following is a brief summary of the available ARC
commands:
a = add files to archive
m = move files to archive
u = update files in archive
f = freshen files in archive
d = delete files from archive
x,e = extract files from archive
r = run files from archive
p = copy files from archive to standard output
l = list files in archive
v = verbose listing of files in archive
t = test archive integrity
c = convert entry to new packing method
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Following is a brief summary of the available ARC
options, which may alter how a command works:
b = retain backup copy of archive
s = suppress compression (store only)
w = suppress warning messages
n = suppress notes and comments
o = overwrite existing files when extracting
g = encode or decode archive entry
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ARC COMMANDS
This section describes each of the commands. ARC will
accept any one command at a time. If no commands are
given, then a brief command list is displayed.
ADDING FILES
Files are added to an archive using the "A" (Add), "M"
(Move), "U" (Update), or "F" (Freshen) commands. Add
always adds the file. Move differs from Add in that
the source file is deleted once it has been added to
the archive.
Update differs from Add in that the file is only added
if it is not already in the archive, or if it is newer
that the corresponding entry in the archive.
Freshen is similar to Update, except that new files
are not added to the archive; only files already in
the archive are updated.
For example, if you wish to add a file named
"TEST.DAT" to an archive named "MY.ARC", you would use
a command of the form:
ARC a my test.dat
If you wanted to add all files with a ".C" extension,
and all files named "STUFF" to an archive named
"JUNK.ARC", you could type:
ARC a junk *.c stuff.*
If you wanted to move all files in your current
directory into an archive named "SUM.ARC", you could
use a command of the form:
ARC m sum *.*
If you have an archive named "TEXT.ARC", and you
wanted to add to it all of your files with an
extension of ".TXT" which have been created or changed
since they were last archived, then you would type:
ARC u text *.txt
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If you have a bunch of files in your current
directory, with backup copies being stored in an
archive named "SAFE.ARC", then if you wanted to make
sure that every file in the archive is the latest
version of that file, you would type:
ARC f safe
A word about Update and Freshen: These are similar in
that they look at the date and time of last change on
the file, and only add it if the file has been changed
since it was last archived. They differ in that
Update will add new files, while Freshen will not.
In other words, Update looks for the files on disk,
and adds them if they are new or have changed, while
Freshen looks in the archive, and tries to update the
files which are already there.
Archive entries are always maintained in alphabetic
order. Archive entries may not have duplicate names.
If you add a file to an archive that already contains
a file by that name, then the existing entry in the
archive is replaced. Also, the archive itself and its
backup will not be added.
You may also add a file which is in a directory other
than your current directory. For example, it is
perfectly legal to type:
ARC a junk c:\dustbin\stuff.txt
You cannot add two files with the same name. In other
words, if you have a file named "C:\DUSTBIN\STUFF.TXT"
and another file named "C:\BUCKET\STUFF.TXT", then
typing:
arc a junk c:\dustbin\*.* c:\bucket\*.*
will not work.
ARC does not save the path name. In other words, if
you specify a drive and/or path when adding a file,
only the actual file name is stored in the archive.
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ARC will never add an archive to itself, nor will it
add the temporary copy or a backup copy of the
archive.
An interesting note: It has been brought to our
attention that BASIC programs compress to a smaller
size when they are *not* tokenized. If you are more
concerned with space than speed, you may wish to
convert your BASIC programs to ASCII form before
adding them to an archive. Your BASIC manual should
give instructions on how to do this.
EXTRACTING FILES
Archive entries are extracted with the "E" (Extract)
and "X" (eXtract) commands. For example, if you had
an archive named "JUNK.ARC", and you wanted all files
in it with an extension of ".TXT" or ".DOC" to be
recreated on your disk, you could type:
ARC x junk *.txt *.doc
If you wanted to extract all of the files in an
archive named "JUNK.ARC", you could simply type:
ARC x junk
Whatever method of file compression was used in
storing the files is reversed, and uncompressed copies
are created in the current directory.
You can also specify a path name, in which case the
decompressed copy is placed in the specified
directory. For example, if you had an archive named
"JUNK.ARC", and you wanted all files in it with an
extension of ".TXT" to be placed in the directory
"C:\WASTE\LAND", then you could type:
ARC x junk c:\waste\land\*.txt
If you wanted to put the file "TRASH.TXT" on your A:
drive, and the file "LITTER.TXT" on your B: drive, you
could type:
ARC x junk a:trash.txt b:litter.txt
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If you give more than one path for a file, then only
the first one is used. For example, if you typed:
ARC x junk a:trash.txt b:trash.txt
then TRASH.TXT will be placed on your A: drive.
DELETING FILES
Archive entries are deleted with the "D" (Delete)
command. For example, if you had an archive named
"JUNK.ARC", and you wished to delete all entries in it
with a filename extension of ".C", you could type:
ARC d junk *.c
LISTING ARCHIVE ENTRIES
You can obtain a list of the contents of an archive by
using the "L" (List) command or the "V" (Verbose list)
command. For example, to see what is in an archive
named "JUNK.ARC", you could type:
ARC l junk
If you are only interested in files with an extension
of ".DOC", then you could type:
ARC l junk *.doc
ARC prints a short listing of an archive's contents
like this:
Name Length Date
============ ======== =========
ALPHA.TXT 6784 16 May 85
BRAVO.TXT 2432 16 May 85
COCO.TXT 256 16 May 85
==== ========
Total 3 9472
"Name" is simply the name of the file.
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"Length" is the unpacked file length. In other words,
it is the number of bytes of disk space which the file
would take up if it were extracted.
"Date" is the date on which the file had last been
modified, as of the time when it was added to the
archive.
"Total" is pretty obvious, I think.
ARC prints a verbose listing of an archive's contents
like this:
Name Length Stowage SF Size now Date Time CRC
============ ======== ======== ==== ======== ========= ====== ====
ALPHA.TXT 6784 Crunched 35% 4413 16 May 85 11:53a 8708
BRAVO.TXT 2432 Crunched 41% 1438 16 May 85 11:53a 5BD6
COCO.TXT 256 Packed 5% 244 16 May 85 11:53a 3AFB
==== ======== ==== ========
Total 3 9472 27% 6095
"Name", "Length", and "Date" are the same as for a
short listing.
"Stowage" is the compression method used. The
following compression methods are currently known:
-- No compression.
Packed Runs of repeated byte values are
collapsed.
Crunched Lempel-Zev compression technique
employed.
Squeezed Huffman encoding compression
technique, as employed by an
earlier version of ARC.
"SF" is the stowage factor. In other words, it is the
percentage of the file length which was saved by
compression. The total stowage factor is the stowage
factor for the archive as a whole, not counting
archive overhead.
"Size now" is the number of bytes the file is
occupying while in the archive.
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"Time" is the time of last modification, and is
associated with the date of last modification.
"CRC" is the CRC check value which has been stored
with the file. Another CRC value will be calculated
when the file is extracted or tested to ensure data
integrity. There is no especially good reason for
displaying this value.
RUNNING FILES
Archive entries may be run without being extracted by
use of the "R" (Run) command. For example, if you had
an archive named "JUNK.ARC" which contained a file
named "LEMON.COM", which you wished to run, you could
type:
ARC r junk lemon
You can run any file from an archive which has an
extension of ".COM", ".EXE", ".BAT", or ".BAS". You
do not have to specify the extension, but all matching
files are run if you do not. In other words, if you
had an archive named "JUNK.ARC" which contained the
files "LEMON.COM", "LEMON.EXE", and "LEMON.BAS", and
you typed:
ARC r junk lemon
Then all three programs will be run. You can avoid
this by specifying an extension in this case.
You can give arguments to the program you are running
by appending them to the command line. For example,
if you have an archive named "JUNK.ARC" which contains
a program named "LEMON.COM", and you wanted to run it
giving it the argument "JUICE", you would type:
ARC r junk lemon juice
You will need a fair amount of memory to run a program
from an archive. It probably cannot be done with less
than 256k.
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In practice, the file to be run is extracted, run, and
then deleted. In other words, the above example is
equivalent to:
ARC x junk lemon.com
lemon juice
erase lemon.com
If you have an archive which contains a program that
you will be running often, then you should probably
extract the program from the archive and use it
normally.
PRINTING FILES
Archive entries may be examined with the "P" (Print)
command. This works the same as the Extract command,
except that the files are not created on disk.
Instead, the contents of the files are written to
standard output. For example, if you wanted to see
the contents of every ".TXT" file in an archive named
"JUNK.ARC", but didn't want them saved on disk, you
could type:
ARC p junk *.txt
If you wanted them to be printed on your printer
instead of on your screen, you could type:
ARC p junk *.txt >prn
TESTING AN ARCHIVE
The integrity of an archive may be tested by use of
the "T" (Test) command. This checks to make sure that
all of the file headers are properly placed, and that
all of the files are in good shape.
This can be very useful for critical archives, where
data integrity must be assured. When an archive is
tested, all of the entries in the archive are unpacked
(without saving them anywhere) so that a CRC check
value may be calculated and compared with the recorded
CRC value.
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For example, if you just received an archive named
"JUNK.ARC" over a phone line, and you want to make
sure that you received it properly, you could type:
ARC t junk
It defeats the purpose of the T command to combine it
with N or W.
CONVERTING AN ARCHIVE
The "C" (Convert) command is used to convert an
archive entry to take advantage of newer compression
techniques. This is occasionally desirable when a new
version of ARC is released. Please refer to the
revision history section for details on when new
compression methods were implemented.
For example, if you had an archive named "JUNK.ARC",
and you wanted to make sure that all files with an
extension of ".DOC" were encoded using the very latest
methods, you could type:
ARC c junk *.doc
Or if you wanted to convert every file in the archive,
you could type:
ARC c junk
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ARC OPTIONS
This section describes the options which are available
to modify how ARC works. Any of these options can be
combined with any of the commands, though the result
may not always be something you'd want to do.
SUPPRESSING COMPRESSION
The "S" (Suppress compression) option can be combined
with any command that updates archive entries. These
include Add, Move, Update, Freshen, and Convert. The
effect of the S option is to prevent any compression
techniques from being employed. This is intended to
allow you to add a few files at a time to an archive
quickly, and then later convert the archive to
compress everything at once.
For example, over the course of a day you might give
each of the following commands:
ARC as junk *.txt
ARC as junk *.mac
ARC as junk *.doc
At the end of the day, when you have finished adding
things to the archive, you could have all of the
archive entries compressed at once by typing:
ARC c junk
You could also decompress the archive by typing:
ARC cs junk
though I can't imagine why you'd want to.
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BACKUP RETENTION
When ARC changes an archive (during an Add, Move,
Update, Freshen, Delete, or Convert) it creates a new
archive with the same name, but with an extension of
".$$$". For example, if you add a file to an archive
named STUFF.ARC, then ARC will create a new archive
named STUFF.$$$. ARC will read from your existing
archive and write out the new archive with any changes
to the ".$$$" copy.
Normally when ARC is finished it deletes the original
and renames the new archive to the original name (ie.
STUFF.ARC goes away, and STUFF.$$$ becomes the new
STUFF.ARC). Among other things, this means that if
anything goes wrong and ARC is unable to finish, then
your original archive will still be intact.
In some circumstances you may wish to retain the
original version of the archive as a backup copy. You
can do this easily by using the Backup option. Add
the letter "B" to your command, and ARC will rename
your original archive to have an extension of ".BAK"
instead of deleting it.
In other words, if you wanted to add "WASTE.TXT" to an
archive named "JUNK.ARC", but wanted to keep a backup
copy, then you would type:
ARC ab junk waste.txt
Your original archive would become "JUNK.BAK", while
"JUNK.ARC" would contain the new "WASTE.TXT" file.
If you keep a backup of an archive which already has a
backup, then the older backup copy is deleted.
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MESSAGE SUPPRESSION
ARC prints three types of messages: warnings,
comments, and errors.
Warnings are messages about suspected error
conditions, such as when a file to be extracted
already exists, or when an extracted file fails the
CRC error check. Warnings may be suppressed by use of
the "W" (Warn) command. You should use this command
sparingly. In fact, you should probably not use this
command at all.
Comments (or notes) are informative messages, such as
naming each file as it is added to the archive.
Comments and notes may be suppressed by use of the "N"
(Note) command.
Errors are actual system problems, such as running out
of disk space. You cannot suppress errors.
For example, suppose you extracted all files with an
extension of ".BAS" from an archive named "JUNK.ARC"
Then, after making some changes which you decide not
to keep, you decide that you want to extract them all
again, but you don't want to be asked to confirm every
one. In this case, you could type:
ARC xw junk *.bas
Or, if you are going to add a hundred files with an
extension of ".MSG" to an archive named "TRASH.ARC",
and you don't want ARC to list them as it adds them,
you could type:
ARC an trash *.msg
Or, if you want to extract the entire contents of an
archive named "JUNK.ARC", and you don't want to hear
anything, then type:
ARC xnw junk
A special case is provided when extracting files from
an archive. One of the various warnings that can
occur is when a file being extracted already exists on
disk. Normally, ARC will stop and ask you if you want
to overwrite the file. This can be suppressed with
the "W" command, but that will also suppress any
ARC Page 15
warnings about other things, like failed CRC checks
and such.
The "O" (Overwrite) option suppresses *only* the warning
that the file already exists. For example, in our
earlier case of extracting all the ".BAS" files from
"JUNK.ARC", a much safer way to do it is to type:
ARC xo junk *.BAS
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ENCRYPTION/DECRYPTION
Archive entries may be encrypted and decrypted by
using the "G" (Garble) option. The Garble option
takes the remainder of the command string as the
password to use, so it must be the *last* option.
For example, if you wanted to add a file named
"WASTE.TXT" to an archive named "JUNK.ARC", and you
wanted to encrypt it using the password "DEBRIS", then
you would type:
ARC agdebris junk waste.txt
Later on, when you want to extract it again, you would
type:
ARC xgdebris junk waste.txt
The password you supply is used to encrypt (or
decrypt) the archive entry by performing an exclusive
OR between each byte of the packed data and each byte
of the password. The password can be any length, and
each of its bytes is used in rotation. The password
is converted to uppercase before it is used, so it is
*not* case sensitive. Since the encryption is performed
on the packed data, it has no effect on stowage
factors.
This is not a particularly sophisticated means of
encryption, and it is theoretically possible to crack.
Still, since it is performed on the packed data, the
result should be quite sufficient for casual use.
You can, if you wish, use different passwords for
different files in an archive, but we advise against
it. If you are going to encrypt an archive, we
suggest you use the same password for every file, and
give the password whenever you do anything at all with
the archive. It is possible to list the entries in an
encrypted archive using the "L" and "V" commands
without giving the password, but nothing else will
work properly.
We advise that you use this option sparingly, if at
all. If you should forget or mistype your password,
it is highly unlikely that you will ever recover your
data.
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RAMDISK SUPPORT
If you have a RAMdisk, or other high-speed storage,
then you can speed up ARC somewhat by telling it to
put its temporary files on the RAMdisk. You do this
by setting the ARCTEMP environment string with the MS-
DOS SET command. For example, if drive B: is your
RAMdisk, then you would type:
set ARCTEMP=B:
Refer to the MS-DOS manual for more details about the
SET command. You need only set the ARCTEMP string
once, and ARC will use it from then on until you
change its value or reboot your system.
If ARC does not find an environment string named
ARCTEMP, then it looks for one named TEMP to use
instead. Several packages already use the TEMP string
for exactly this purpose. If you have need of an
environment string named TEMP for something else, then
you should be sure to define ARCTEMP.
There are a limited number of temporary files created
by ARC. The Convert command uses a file named
"$ARCTEMP.CVT" to hold each file as it is being
converted. The Run command also creates a temporary
file, which has the name "$ARCTEMP", and whose
extension matches that of the file being run.
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MARC
MARC is a separate program which is used to merge
archives created by ARC. MARC moves files from one
archive to another without unpacking them.
MARC is used as follows:
MARC target source [template . . .]
Where:
target is the name of the archive to add files
to.
source> is the name of the archive to read files
from.
template> is one or more file name templates.
The wildcard characters "*" and "?" may be used.
If no template is supplied, then all of the files
in source> are added to target>.
It is not necessary for the target to exist. If it
does not exist, then it is created. Thus, MARC can be
used as an "extractor" as well as a "merger".
For example, if you wanted to create an archive named
"JUNK.ARC", which is to contain all of the files with
an extension of ".TXT" which are currently contained
in another archive named "WASTE.ARC", then you could
type:
MARC junk waste *.txt
If you wanted to create an archive named "JUNK.ARC",
which is to contain all of the files currently in the
archives "WASTE.ARC" and "TRASH.ARC", you could type:
MARC junk waste
MARC junk trash
If MARC is invoked with no arguments, then it gives
brief directions in its use.
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ARCE
ARCE is a program which is used to extract files from
an archive. It will *only* extract files, and it will
*not* extract encrypted files. It doesn't do anything
that ARC can't do, but it is highly optimized for the
sole purpose of archive extraction, so it is very
small and very fast.
ARCE is used in a fashion very similar to the "ARC E"
command (hence the name). The first argument is the
name of the archive to extract files from, and may
include a drive and path specifier. Up to sixteen
additional arguments can be supplied, which specify
the files to extract. The wildcard characters "*" and
"?" are allowed, as with ARC. If no files are named,
then all files are extracted from the archive. If the
file being extracted already exists, you are asked
whether or not you want to overwrite it. You can use
the "/R" option to bypass this.
For example, if you had an archive named "WASTE.ARC"
that you wanted to extract everything from, then you
could type:
ARCE waste
Or if you just wanted to extract the files with a
filename extension of ".ASM", you could type:
ARCE waste *.asm
If you already have a few files from the archive that
you want replaced, then you could type:
ARCE waste *.asm /R
If you run ARCE with no arguments at all, then it will
give you a brief reminder of how to use it.
NOTICE:
NOTICE: ARCE is the copyrighted property of Vernon D.
Buerg and Wayne Chin. It is included on the
ARC program disk as a service to ARC users.
Vernon D. Buerg
456 Lakeshire Drive
Daly City, CA 94015
RBBS: (415) 994-2944
ARC Page 20
VERSION NUMBERS
There seems to be some confusion about our version
numbering scheme. All of our version numbers are
given as a number with two decimal places.
The units indicate a major revision, such as adding a
new packing algorithm.
The first decimal place (tenths) indicates a minor
revision that is not essential, but which may be
desired.
The second decimal place (hundredths) indicates a
trivial revision that will probably only be desired by
specific individuals or by die-hard "latest version"
fanatics.
ARC also displays its date and time of last edit. A
change of the date and time without a corresponding
change in version number indicates a truly trivial
change, such as fixing a spelling error.
To sum up: If the units change, then you should get
the newer version as soon as you can. If the tenths
change, then you may want to get the newer version,
but there's no hurry. If anything else changes, then
you probably shouldn't bother.
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COMMON QUESTIONS AND ANSWERS
Here are some of the more common questions we've
received about ARC, along with their answers:
Q: Why does ARC run out of room if I make an archive
bigger than about 180k?
A: Because you are working on a floppy disk. ARC
creates a copy of your archive, incorporating any
new files as it goes. When it is done, it deletes
the original and renames the new one. There are a
number of reasons for doing it this way, one being
that your original archive is still intact if
anything happens while ARC is running.
You can save some space by using drive specifiers
and having the archive and the files to add on
separate disks, but you still won't be able to make
an archive larger than about 180k. If you need to
make a larger archive, and if you have a fixed
disk, then you can create the archive on the fixed
disk and then copy it to the floppy.
Q: I've seen an ARC.COM and an ARC.EXE. Which one is
the right one?
A: ARC.EXE. One or more people have been running ARC
through a utility that converts an ".EXE" file to a
".COM" file. But this utility is designed to save
space, not speed. On ARC it saves about 250 bytes,
and makes no measurable difference in program
speed. We've decided that the savings are not
worth the extra step in development in this case.
Q: How can I get the latest version of ARC?
A: ARC updates are distributed through normal
shareware channels, and by FidoNet. We also ship a
program update disk on every order of $50 or more.
Also, please refer to the next section for
information about our maintenance contracts.
ARC Page 22
Q: Can I use ARC to distribute my public domain or
shareware program?
A: Yes, of course.
Q: Can I use ARC to distribute my commercial software
package?
A: Yes, provided that you obtain a commercial
distribution license from us. Please contact us
for details.
Q: I'm a commercial user. Why should I pay for
shareware that others get for free?
A: Because you cannot credibly plead poverty.
___
Shareware, all shareware, is an attempt to develop
a new marketing channel to the benefit of everyone.
You can still "test drive" shareware for a short
period, but if you decide to use it in your
business, then you should pay for it.
Q: Why not allow me to select which method of
compression I want ARC to use?
A: It would needlessly complicate ARC, both internally
and in use. The exact nature of the compression
methods used are complex, and quite different. The
only sure way to tell which will be best in any
given case is to analyze the data, as ARC does.
The method chosen may not always be what you
expect.
ARC Page 23
MAINTENANCE CONTRACTS
Registered users of ARC receive 90 days of telephone
support at no extra charge. If you wish, you can
extend this by pruchasing a maintenance contract.
A maintenance contract costs $50 per year and entitles
you to unlimited telephone support, as well as free
updates to ARC as they come out.
ARC Page 24
REVISION HISTORY
CHANGES IN VERSION 3
The function used to calculate the CRC check value in
previous versions has been found to be in error. It
has been replaced with the proper function. ARC will
still read archives created with earlier versions of
ARC, but it will report a warning that the CRC value
is in error. All archives created prior to version
3.0 should be unpacked and repacked with the latest
version of ARC.
Transmitting a file with XMODEM protocol rounds the
size up to the next multiple of 128 bytes, adding
garbage to the end of the file. This used to confuse
ARC, causing it to think that the end of the archive
was invalidly formatted. This has been corrected in
version 3.01. Older archives may still be read, but
ARC may report them to be improperly formatted. All
files can be extracted, and no data is lost. In
addition, ARC will automatically correct the problem
when it is encountered.
CHANGES IN VERSION 4
ARC is adding another data compression technique in
this version. We have been looking for some technique
that could improve on Huffman squeezing in at least a
few cases. So far, Lempel-Zev compression seems to be
fulfilling our fondest hopes, often achieving
compression rates as much as 20% better than
squeezing, and sometimes even better. Huffman
squeezing depends on some bytes being more "popular"
than others, taking the file as a whole. Lempel-Zev
compression is instead looking for strings of bytes
which are repeated at various points (such as an end
of line followed by spaces for indentation). Lempel-
Zev compression is therefore looking for repetition at
a more "macro" level, often achieving impressive
packing rates.
In the typical case a file is added to an archive once
and then extracted many times, so the increased time
for an update should more than pay for itself in
increased disk space and reduced transmission time.
ARC Page 25
CHANGES IN VERSION 4.1
Lempel-Zev coding has been improved somewhat by
performing non-repeat compression on the data before
it is coded (as was already done with Huffman
squeezing). This has the two fold advantage of (a)
reducing to some extent the amount of data to be
encoded, and (b) increasing the time it takes for the
string table to fill up. Performance gains are small,
but noticeable.
The primary changes are in internal organization. ARC
is now much "cleaner" inside. In addition to the
aesthetic benefits to the author, this should make
life easier for the hackers out there. There is also
a slight, but not noticeable, improvement in overall
speed when doing an update.
CHANGES IN VERSION 4.3
Version 4.3 adds the much-demanded feature of using
pathnames when adding files to an archive.
Version 4.3 is also using a slightly different
approach when adding a file to an archive. The end
result is twofold:
1) Slightly more disk space is required on the drive
containing the archive. This should only be
noticeable to those creating very large archives on
a floppy based system.
2) A 30% reduction in packing time has been achieved
in most cases. This should be noticeable to
everyone.
As always, version 4.3 is still fully upwards
compatible, and is backwards compatible as far as
version 4.1.
ARC Page 26
CHANGES IN VERSION 4.4
The temporary file introduced in version 4.3
occasionally caused problems for people who had not
added a FILES= statement to their CONFIG.SYS file.
This has now been corrected. Also, support of the
ARCTEMP environment string was added to allow placing
of the temporary file on a RAMdisk.
A bug was reported in the Run command, which has been
fixed. From the nature of the bug, and the extreme
time required before the bug was reported, it is
deduced that the Run command is probably the least
used feature of ARC.
The Update command was changed. It is no longer a
straight synonym for Add. Instead, Update now only
adds a file if it is newer than the version already in
the archive, as shown by the MS-DOS date/time stamp.
CHANGES IN VERSION 4.5
The Convert command was not making use of RAMdisk
support. Now it is.
The Freshen command was added. Our first choice for a
name was Refresh, but we already had a Run command.
Assuming that you have an archive which already
contains everything you want in it (for software
distribution, perhaps), then Freshen would be used to
update the archive. It was pointed out to us that ARC
already knows what is in the archive, so it should be
able to look on disk for newer versions. Now it can.
The Suppress compression option was added by popular
demand. It allows files to be added quickly to an
archive, since the files are not analyzed or
compressed, but merely stored straight. The intent is
to allow users to build an archive "in pieces", and
then compress all of the entries at once with the
Convert command. The conversion is much faster if you
take advantage of RAMdisk support.
A minor bug was detected in our handling of date/time
stamps which occasionally resulted in stamping an
archive with the wrong date and time. This has been
corrected.
ARC Page 27
CHANGES IN VERSION 5.0
The Move command used to delete the files as it went.
It now waits until it is finished updating the
archive, and deletes them all at once. (You *did* know
that Move is just an Add where the file gets deleted,
didn't you?) This, along with the changes made in
version 4.5, means that it is now much safer to
interrupt ARC while it is working.
The Print command no longer prints the name of each
file. Instead, it prints a formfeed after each file.
The Run command now supports BASICA programs. Also,
the filename extension is no longer required on the
Run command.
The Garble option was added. It provides a convenient
means of low level data security for the casual user.
Use it sparingly, if at all.
ARC no longer tests for the presence of $ARCTEMP.CRN
before creating a new one. If you interrupt ARC a
lot, you'll find this much more convenient. If you
happen to have a file named $ARCTEMP.CRN which you
want to keep, too bad.
Improved error recovery was added when reading an
archive. ARC now has a good chance of recovering the
data from a corrupted archive (the corrupted entry is
still lost, of course).
Path support has been added for all commands, though
it doesn't do anything on most of them. For example,
there isn't much we can do with a path in the List
command. But many users will be glad to know that a
path can be used when extracting a file, and specifies
where the file is to be placed.
Support for the TEMP environment string was added. If
ARC doesn't find an environment string named ARCTEMP,
then it looks for one named TEMP to use instead.
Several packages already use the TEMP string for
exactly this purpose. With any luck, maybe we can get
a standard going.
ARC Page 28
ARC is now using a different variation of Lempel-Zev
coding, courtesy of Kent Williams, who found it on
USENET and adapted it to the IBM PC. The new method
differs from the old in several respects. The most
significant differences are:
1) Where our previous implementation used a fixed code
size of twelve bits, the new one starts with a code
size of nine bits and increases it as it needs to.
2) The earlier method tended to "choke" on large files
when its string table filled up. The new method
has a rather ingenious scheme its authors call
"adaptive reset." When it notices that its string
table has filled, and its compression ratio is
starting to suffer, it clears the table and starts
defining new strings.
Our benchmarks show an improvement in compression on
the order of 10% when crunching is used.
Additionally, ARC 5.0 is on the order of 23% faster at
adding a file when crunching is used, or 13% faster
when squeezing is used. Extracting a file crunched
with the new method is 27% faster than it is with the
old method. Extraction of any other type of file
(including those crunched with the older method) is no
faster than before. These figures are based on our
own benchmark tests; your results may vary.
The previous implementation of Lempel-Zev coding is no
longer used to pack files. The "V" (Verbose listing)
command distinguishes between the two by referring to
the older method as "crunched" (with a lower-case
"c"), and the newer method as "Crunched" (with a
capital "C").
ARC 5.0 can still read archives created by earlier
versions of ARC, but once again it creates archives
which older versions cannot read.
CHANGES IN VERSION 5.1
Rick Moore discovered that ARC was occasionally adding
an archive to itself. This would only happen when the
archive is in the same directory as the files being
added, and its name comes last. This bug has been
fixed, though it is still possible to fool ARC into
adding an archive to itself by getting tricky with
path names.
ARC Page 29
Dana Montgomery found the upper limit on how many
files can be added to an archive. There's always been
an upper limit, but it depends on memory, and used to
be larger than anyone could possibly want (knock on
wood). However, the added memory requirements in
version 5.0 lowered this limit into the realm of
possibility, somewhere around 300 files. We change
some things around, and effectively, there is no
longer a limit on how many files you can add at once.
ARC will add the files in batches of as many as it can
handle at one time.
We've also introduced a new packaging method for ARC
and its documentation, since we are in the unique
position of being unable to use ARC for this purpose.
We've created a program called ARC51.COM which, when
executed, attempts to create the ARC program and
manual. You must be in the same directory as
ARC51.COM when you run it.
CHANGES IN VERSION 5.2
We've made some changes to Lempel-Zev coding to
further improve its compression ability on "poor fit"
files (mainly .EXE and .COM files). The result is
that crunching now works better than squeezing on
almost all files, and comes close on most of the rest
(within 5%, by our benchmarks). Accordingly, we have
dropped Huffman encoding in this version. Our
benchmarks show a speed improvement of around 14% when
adding a file to an archive.
A low-level file copy routine was implemented to speed
up bulk data moves. Deleting or adding a file to a
large existing archive is now much faster.
The Run command has been modified to allow passing
command line arguments to the program being run.
The temporary file introduced in version 4.3 has been
eliminated. Crunched output generated in the analysis
phase is now placed directly in the output archive,
and is rewritten if crunching turns out not to be the
best choice. This can, in rare circumstances, cause
an archive to be slightly larger than it should be,
but it also makes ARC considerably faster at adding
files to an archive.
ARC Page 30
PROGRAM HISTORY AND CREDITS
In its short life thus far, ARC has astounded us with
its popularity. We first wrote it in March of 1985
because we wanted an archive utility that used a
distributive directory approach, since this has
certain advantages over the then popular central
directory approach. We added automatic squeezing in
version 2 at the prompting of a friend. In version
2.1 we added the code to test for the best compression
method. In less than a year we found that our humble
little program had spread across the country, and
seems to have become a new institution.
We are thankful for the support and appreciation we
have received. We hope that you find this program of
use.
If we have achieved greatness, it is because we have
stood upon the shoulders of giants. Nothing is
created as a thing unto itself, and ARC is no
exception. Therefore, we would like to give credit to
the following people, without whose efforts ARC could
not exist:
Brian W. Kernighan and P. J. Plauger, whose book
"Software Tools" provided many of the ideas behind the
distributive directory approach used by ARC.
Dick Greenlaw, who wrote the public domain SQ and USQ
programs, in which the Huffman squeezing algorithm was
first developed.
Robert J. Beilstein, who adapted SQ and USQ to
Computer Innovations C86 (the language we use), thus
providing us with important parts of our squeezing
logic.
Kent Williams, who graciously allowed us to use his
LZWCOM and LZWUNC programs as a basis for our Lempel-
Zev compression logic, and who continues to make
valuable contributions.
David Schwaderer, whose article in the April 1985
issue of PC Tech Journal provided us with the logic
for calculating the CRC 16 bit polynomial.
ARC Page 31
Terry A. Welch, whose article "A Technique for High
Performance Data Compression", IEEE Computer Vol 17 No
6 (June 1984) seems to have started all the research
on Lempel-Zev coding.
Spencer W. Thomas, Jim McKie, Steve Davies, Ken
Turkowski, James A. Woods, and Joe Orost, who are the
authors of the UNIX compress utility.
Alex Jacobs, who in June of 1985 sent us the very
first shareware contribution we ever received.
And many, many others whom we could not identify.
ARC Page 32
BULLETIN BOARDS
ARC is distributed mainly through shareware channels.
Among other things, this means that ARC is available
from many bulletin board systems. In fact, the system
operators (sysops) of many bulletin boards have taken
to storing almost all of their downloadable files in
archives to save themselves disk space and to save
their users time.
This also makes things more convenient for the
bulletin board users, since one archive may contain
several programs, any related data files, and the
documentation. Many shareware authors have taken to
distributing their software in archives to help ensure
that the users receive everything.
Obviously, we can't do that with ARC. As a result,
many of our users have ARC, but don't have the manual.
Most of our customer support calls come from people
who have never seen the manual, and in many cases
didn't even know that one exists!
To solve this problem we developed what is in essence
a self-unpacking archive. We distribute this as
"ARCxxx.COM", where "xxx" is the current version
number. For example, ARC version 5.20 would be
distributed as "ARC520.COM". This program, when run,
unpacks itself into a copy of ARC plus its
documentation.
Now that we've gone to all that work, we'd really
appreciate it if you would use this program when you
distribute ARC.
ARC Page 33
SITE LICENSES
Corporate users may wish to obtain a site license for
the use of ARC. Please use the order form in this
manual to order a site license. Site licenses are
granted as of when we receive your payment. License
fees vary depending on the number of computers on
which ARC will be used, as follows:
1 to 9 machines $35 each
10 to 24 machines $25 each
25 to 49 machines $20 each
50 to 99 machines $15 each
over 99 machines $1500 one time fee
Enclosed is a site license agreement, which should be
signed and sent with your payment when ordering a
commercial site license.
A commercial site license does not include additional
copies of the ARC program disk and the ARC manual.
Instead, you make your own copies of the disk and
manual as you need them. If you wish, you can order
additional program disks and manuals from us.
Additional program disks cost $10 each. Additional
manuals cost $20 each. If you wish, you can order
program sets for $40 each. A "program set" is a
program disk and manual enclosed in a vinyl binder.
There is a $50 minimum on all orders.
ARC Page 34
SITE LICENSE APPLICATION
The use of ARC in a commercial environment or government organization
is granted under the following terms:
1. Payment of the license fee must be made to System Enhancement
Associates, Inc. The fee is based on the number of computers
which will be used to run ARC, as follows:
1 to 9 machines $35 each
10 to 24 machines $25 each
25 to 49 machines $20 each
50 to 99 machines $15 each
over 99 machines $1500 one time fee
2. You may use ARC on the number of computers included in the license
fee. If you have paid the fee for over 99 machines, then you may
use ARC on any number of computers within your organization.
3. You may make copies of the program and documentation, in their
original, unmodified form, without restriction. You may
distribute these copies without restriction.
4. If these copies are distributed outside of your organization, you
have no obligation to control the use of those copies which are
outside of your organization.
5. You may make copies of the program documentation, in both its
printed form and machine readable form, without restriction.
6. You may use all future versions of ARC under this license.
7. You may *not* modify the program or charge a fee for copying or
distributing the program or its documentation.
8. It is your responsibility to make the necessary copies and to
deliver them to the computers which they will be used on. If you
wish, you can order additional ARC program disks and manuals.
9. We are not responsible for *anything* that may happen or not happen
if you use ARC. You're on your own.
I agree to abide by the terms and conditions of this license.
_____________________________ __________________________
Signature Date
_____________________________
Name (please print or type)
_____________________________
Title
_____________________________
Company
ORDER FORM
Check which items you wish to purchase:
[] Noncommercial license for the use of ARC.
[] Commercial license for the use of ARC on ___ computers (see
attached price schedule and terms).
[] Program disk and documentation (only on orders of $50 or more,
not counting maintenance contracts).
[] ____ additional program disks at $10 per disk.
[] ____ additional manuals at $20 per manual
[] ____ additional program sets (disk, manual, and binder) at $40
per program set.
[] One year maintenance agreement at $50 per year.
[] Payment of $_____ is enclosed (check or money order).
[] Please charge $_____ to my [] Visa or [] MasterCard:
Card number: _______________________________
Expiration date: ___________________________
Signature: _________________________________
_______________________________________________
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Address
______________________ ________ ____________
City State Zip
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FidoNet address
Send this completed form to:
System Enhancement Associates, Inc.
21 New Street, Wayne NJ 07470
For program disk orders outside the U.S., please add an additional $5,
and enclose an international money order payable in U.S. currency.
For commercial site license orders, please enclose a signed copy of
the site license agreement.
