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ARC
File Archive Utility
Version 6.00
COPYRIGHT 1985,86,87,88,89
by
System Enhancement Associates, Inc.
ALL RIGHTS RESERVED
This document describes version 6.00 of the ARC file
utility, which was created by System Enhancement
Associates, Inc. in January of 1989.
� LIMITED WARRANTY
IMPORTANT NOTICE:
IMPORTANT NOTICE: Any use of this software for any
period of time for any purpose whatsoever constitutes
your unqualified acceptance of this LICENSE and
subjects you to all of the terms and conditions set
forth below:
System Enhancement Associates, Inc. ("SEA") warrants
to any Licensee that acquires the program from SEA or
an authorized SEA representative ONLY that:
1) All diskettes SEA provides constitute an accurate
duplication of the software and SEA will replace
any diskette found to be defective within 30 days
from date of acquisition. SEA will not honor this
warranty if the diskette has been subjected to
physical abuse, or used in defective or non-
compatible equipment.
2) SEA's software will perform substantially as
described in the documentation SEA regularly
supplies with that software, if operated as
prescribed in such documentation including the
hardware and software environment specified.
3) If a significant defect in any program is found,
Licensee's only remedy shall be to receive refund
of the actual fee Licensee paid for such defective
program. In no event will such a refund exceed
the fee SEA charges for such program.
4) SEA makes no warranty or representation that the
software will be error free nor that its use by
Licensee will be uninterrupted.
Except as provided above, SEA disclaims all other
warranties, either express or implied, including but
not limited to any implied warranty of merchantability
or fitness for any particular purpose.
Licensee agrees to take full responsibility for the
selection of and any use whatsoever made of the
software.
IN NO EVENT WILL SEA BE LIABLE FOR ANY DAMAGES
WHATSOEVER (INCLUDING WITHOUT LIMITATION DAMAGES FOR
LOSS OF BUSINESS PROFITS, BUSINESS INTERRUPTION, LOSS
OF BUSINESS INFORMATION OR THE LIKE) ARISING OUT OF
THE USE OF, INTERRUPTION IN THE USE OF, OR INABILITY
TO USE THIS SOFTWARE, EVEN IF SEA HAS BEEN ADVISED OF
ANY POSSIBILITY OR LIKELYHOOD OF SUCH DAMAGES.
� TABLE OF CONTENTS
_______ ____
Section Page
Introduction .................................... 1
Using ARC ....................................... 3
ARC commands .................................... 5
Adding files ................................ 5
Extracting files ............................ 8
Deleting files .............................. 9
Listing archive entries ..................... 9
Running files ............................... 12
Printing files .............................. 13
Testing an archive .......................... 13
Converting an archive ....................... 14
ARC options ..................................... 15
Directories ................................. 15
Level 5 compatibility ....................... 15
Verbose mode ................................ 16
Backup retention ............................ 16
Suppressing compression ..................... 17
Message suppression ......................... 18
Encryption/Decryption ....................... 19
Indirection ..................................... 21
RAMdisk support ................................. 22
Version numbers ................................. 23
Common questions and answers .................... 24
Maintenance contracts ........................... 26
Revision history ................................ 27
Changes in version 5 ........................ 27
Changes in version 5.3 ...................... 29
Changes in version 6.0 ...................... 29
Program history and credits ..................... 31
Bulletin boards ................................. 33
Site licenses ................................... 34
� BLANK PAGE
ARC Page 0
� 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.
ARC Page 1
�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 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-Ziv 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.
ARC Page 2
� 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 storage method
ARC Page 3
�Following is a brief summary of the available ARC
options, which may alter how a command works:
m = move files to archive
z = include subdirectories in archive
v = verbose mode
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
5 = produce only level 5 compatable archives
g = encode or decode archive entry
ARC Page 4
� 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), "U"
(Update), or "F" (Freshen) commands.
Add always adds the file.
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 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
ARC Page 5
�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.
The Add, Update, and Freshen commands may be modified
by the "M" (Move) option. The Move option tells ARC
to delete the file on disk once it is safely tucked
away in the archive. For example, 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 am sum *.*
When Move is combined with Update or Freshen, it
deletes the files that are in the archive, even if it
does not need to compress them again. For example,
suppose you extracted several files from an archive
named "STUFF.ARC" and then made changes to a few of
them. Now you want to pack away the new versions of
what you changed, and clean up the mess (that is,
delete all the files you extracted). You can do it
easily by using the command:
ARC fm stuff
If the Move option is given by itself, it acts like an
"Add and Move". So in our earlier example of moving
everything in your current directory into an archive
named "SUM.ARC", you could also use the command:
ARC m sum *.*
ARC Page 6
� If you don't say which files to add, ARC adds
everything in your current directory. So we could
shorten that to:
ARC m sum
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 this case. 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.
___
However, you can store a subdirectory in an archive,
but you have to tell ARC that you want to do that.
When you add the "Z" option to an Add, Update, or
Freshen, ARC will store subdirectories and their
contents in such a way that it can later recreate
them.
For example, suppose you have a directory name
C:\WASTE that you wish to place in an archive named
"TRASHCAN.ARC". You could do this with the command:
ARC az trashcan c:\waste
This would cause ARC to place the C:\WASTE directory
(and all of its contents, including any subdirec-
tories) into the TRASHCAN.ARC archive. The directory
ARC Page 7
�is stored in such a way that it can be extracted
anywhere. It could, for example, be extracted as
D:\JUNKYARD\WASTE if you so desired.
If you combine the "Z" and "M" options, then the
directories are removed from your disk once they are
safely stored in the archive.
ARC will not 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)
or "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
ARC Page 8
� 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
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
ARC Page 9
�"Name" is simply the name of the file.
"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-Ziv compression technique
employed.
Squeezed Huffman encoding compression
technique, as employed by an
earlier version of ARC.
Deviant A nonstandard variant of Lempel-Ziv
was employed. Files compressed
with this method should be
converted (with the "C" command).
Subdir A subdirectory. The files within
the subdirectory may be viewed by
using the "Z" option.
ARC Page 10
� "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.
"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.
ARC follows a verbose listing with a report giving the
overall compression for everything in the archive and
for anything specific you selected, along with a
prediction of whether or not the files would fit on
your disk if you tried to extract them.
For example, if you wanted to know if all of the files
with an extension of ".TXT" in an archive named
"WASTE.ARC" would fit on your D: drive, you would give
the command:
ARC v waste d:*.txt
At the end of the listing ARC would give its
prediction of whether or not your D: drive has room
for those files.
ARC Page 11
�_____________
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.
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.
ARC Page 12
� ______________
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.
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.
ARC Page 13
�_____________________
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
ARC Page 14
� 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.
___________
DIRECTORIES
The "Z" option tells ARC that you wish to act on
directories as well as files. When combined with Add,
Update, Freshen, or Move it tells ARC to add
directories to the archive. When combined with List
or Verbose it tells ARC to list directory contents.
(The Extract command will always extract directories,
and does not need to be told to do so.)
A directory is treated as a unit by ARC. This means
that when you add a directory to an archive you add
the whole thing, including all of its files and
subdirectories. Likewise, when you extract a
directory from an archive you get all of it.
If you wish to make a change to a directory that is in
an archive, you should extract it, then make whatever
changes you want on disk, and then put the directory
back into the archive.
_____________________
LEVEL 5 COMPATIBILITY
The "5" (level 5 compatibility) option can be combined
with any comand that alters an archive. It tells ARC
that the resulting archive should be fully compatible
with ARC version 5. This is mostly necessary for
creating archives that are to be extracted on other
operating systems where the version of ARC available
for that system does not yet support the ARC version 6
extensions.
When given the level 5 compatibility option, ARC will
ensure that the resulting archive does not contain any
directories, comments, or any extended data fields for
non-MS-DOS operating systems.
ARC Page 15
�____________
VERBOSE MODE
The "V" (Verbose) option can be used with any command,
though it isn't always meaningful.
When used with the List command it causes ARC to
display a "verbose listing" of the archive contents.
In fact, this is its most common use, so you can use
the Verbose option as a command for this purpose.
When used with any command that creates a new archive
(generally during an Add or a Move), it tells ARC to
add a note to the archive saying which version of ARC
created the archive. This note is then automatically
updated every time the archive is modified, and is
displayed during a verbose listing.
Normally when ARC adds files to an archive or deletes
files from an archive it doesn't say anything about
the files it isn't changing. When you use the verbose
option ARC will report them.
________________
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.
ARC Page 16
� 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.
_______________________
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.
ARC Page 17
�___________________
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 18
� 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
_____________________
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. Still, since it is performed on the
packed data, the result should be quite sufficient for
casual use.
ARC Page 19
�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.
ARC Page 20
� INDIRECTION
The list of filenames given to ARC may include
indirect references. If a filename begins with an "at
sign" ("@"), it is taken to be the name of a file
which contains a list of file names. The list of file
names may include further indirection. For example,
the command:
arc a waste junk.txt @trash
would cause ARC to add JUNK.TXT plus all files listed
in the file TRASH to an archive named WASTE.ARC. If
no file is specified, then the list is read from
standard input.
When the N option (suppress Notes) is used with the L
(List files) command, it causes a terse listing of
filenames only, suitable for use with pipes and
redirection. This can be combined with indirection to
easily perform many tasks.
For example, the command:
arc ln waste | arc a trash @
would cause ARC to add files to TRASH.ARC based on the
names of the files stored in WASTE.ARC.
If by some chance you want to archive a file whose
____
name really does begin with an at sign, then preceed
the name with a forward slash ("/"). For example, to
add a file named "@DUST.DAT" to an archive named
"TRASHCAN.ARC", you would type:
arc a trashcan /@dust.dat
The MARC program also allows for indirection.
ARC Page 21
� 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.
ARC Page 22
� 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.
ARC Page 23
� 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. 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 24
� Q: Can I distribute my public domain or shareware
program in an ARC format archive?
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: 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.
Q: ARC keeps giving me an odd error message. It says
"Drive not ready. Abort, Retry, Ignore?" What
does this mean?
A: Close the latches ("doors") on your floppy disk
drives, then press the "R" key.
Q: How can I tell ARC to make an archive that goes on
more than one floppy disk?
A: Create the archive on your fixed disk, and then use
the BACKUP command (or other backup utility).
ARC Page 25
� MAINTENANCE CONTRACTS
Registered users of ARC receive 30 days of telephone
support at no extra charge. If you wish, you can
extend this by purchasing a maintenance contract.
A maintenance contract costs $50 per year. In
addition to telephone support you also receive free
updates to ARC as soon as they are available, and a
______ _____
free subscription to Making Waves, the SEA customer
support newsletter.
ARC Page 26
� REVISION HISTORY
____________________
CHANGES IN VERSION 5
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.
ARC Page 27
�ARC is now using a different variation of Lempel-Ziv
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.
The previous implementation of Lempel-Ziv 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").
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.
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 as of
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.
The Run command has been modified to allow passing
command line arguments to the program being run.
Indirection was added, and the List command was
modified to give a terse listing suitable for use with
indirection when the N option is employed.
ARC Page 28
� A bug was found that would keep an archive entry from
being encrypted if it was stored without compression.
This has now been fixed.
If changes are made to a corrupted archive, the
corrupted entries are discarded. This makes it
possible to lose data accidentally. ARC will now only
make changes to a corrupted archive if the W (suppress
Warnings) option has been given.
Support for a nonstandard variation of Lempel-Ziv was
added.
Two new utilities, SCANDISK and SQDIR, were added to
the ARC program disk. Full program sources for both
are included in UNDEL.ARC on the ARC source disk.
______________________
CHANGES IN VERSION 5.3
A minor bug caused earlier versions of ARC to output
an extra carriage return on an end of line when
dumping text to standard output with the "P" command.
This has now been fixed.
Greatly enhanced error recovery has been added to deal
with corrupted or partially damaged archives. The
corrupted data itself is still lost, of course, but
ARC will recover everything possible.
ARC has been fully ported to Microsoft C version 5.1.
This has resulted in a small speed improvement, and
should make it easier to port ARC to other operating
systems.
A new utility, MKSARC, was added to the ARC program
disk. Regretfully, we cannot release the program
sources for MKSARC.
______________________
CHANGES IN VERSION 6.0
Version 6.0 is a major upgrade for ARC. It is a
substantial rewrite that greatly improves overall
performance. ARC is now as fast as any comparable
program, or faster. The changes are primarily in
internal organization of the code, so that versions
ported to other operating systems should experience a
substantial performance boost as well.
ARC Page 29
�We've also added support for directories, allowing
entire directory trees to be added or moved into an
archive, and later extracted.
We've also designed and implemented a method whereby
versions of ARC ported to other operating systems can
record system-specific information in a compatible
manner. This includes provisions for longer
filenames, more date/time stamps, and even icon
bitmaps. Contact us for details or see the comments
in the ARC sources if you are interested in using this
capability in a version of ARC for a different
operating system.
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.
Kent Williams, who graciously allowed us to use his
LZWCOM and LZWUNC programs as a basis for our Lempel-
Ziv 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.
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-Ziv coding.
ARC Page 31
�Spencer W. Thomas, Jim McKie, Steve Davies, Ken
Turkowski, James A. Woods, and Joe Orost, who are the
authors of the UNIX compress utility.
Karl Schinke, who is the friend that suggested that we
add compression to ARC.
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.EXE", where "xxx" is the current version
number. For example, ARC version 6.00 would be
distributed as "ARC600.EXE". 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 machine $50
2 to 9 machines $35 per machine
10 to 24 machines $25 per machine
25 to 49 machines $20 per machine
50 or more machines $15 per machine
100 or more machines at one location $1500
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.
ARC Page 34
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