ARC

                              File Archive Utility
                                   Version 5.1

















     (C) COPYRIGHT 1985, 1986 by System Enhancement Associates;
         ALL RIGHTS RESERVED





     This document describes the ARC file utility, version 5.1, which was
     created by System Enhancement Associates in February of 1986.











                                Table of Contents
                                Table of Contents



     Introduction  ....................................................   1
     Using ARC  .......................................................   3
     ARC commands  ....................................................   4
         Adding files  ................................................   4
         Extracting files  ............................................   6
         Deleting files  ..............................................   6
         Listing archive entries  .....................................   7
         Printing files  ..............................................   9
         Running files  ...............................................   9
         Testing an archive  ..........................................  10
         Converting an archive  .......................................  10
     ARC options  .....................................................  11
         Suppressing compression  .....................................  11
         Backup retention  ............................................  12
         Message suppression  .........................................  13
         Encryption/decryption  .......................................  14
     RAMdisk support  .................................................  15
     MARC  ............................................................  16
     XARC  ............................................................  17
     Version numbers  .................................................  18
     Program update service  ..........................................  19
     Common questions and answers  ....................................  20
     Revision history  ................................................  22
         Changes in version 3  ........................................  22
         Changes in version 4  ........................................  22
         Changes in version 4.1  ......................................  23
         Changes in version 4.3  ......................................  23
         Changes in version 4.4  ......................................  24
         Changes in version 4.5  ......................................  24
         Changes in version 5.0  ......................................  25
         Changes in version 5.1  ......................................  26
     Program history and credits  .....................................  27
     Site license  ....................................................  28
     Order form  ......................................................  30






















                                  INTRODUCTION



     ARC is the copyrighted property of System Enhancement Associates.
     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.


     Contributions for the use of this program will be appreciated, and
     should be sent to:

                          System Enhancement Associates
                                  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 in the back of 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.

     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.






     ARC                                                           Page   1
     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 four storage methods will result in the greatest
     savings.  These four 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) Huffman squeezing; the file is compressed into variable length bit
        strings, similar to the method used by the SQ programs.

     4) 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 four methods involves no compression at
     all, the resulting archive entry will never be larger than the
     original file.


     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.























     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 packing method



     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
         g   = encode or decode archive entry






     ARC                                                           Page   3

                                  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

     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






     ARC                                                           Page   4
     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.


     ARC will never add an archive to itself, nor will it add the temporary
     copy or a backup copy of the archive.






















     ARC                                                           Page   5

     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

     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











     ARC                                                           Page   6

     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.

     "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  Squeezed   35%      4413  16 May 85  11:53a  8708
     BRAVO.TXT         2432  Squeezed   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 employed:

            --          No compression.
          Packed        Runs of repeated byte values are collapsed.
         Squeezed       Huffman squeeze technique employed.
         Crunched       Lempel-Zev compression technique employed.


     ARC                                                           Page   7

     "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                                                           Page   8
     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



     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 cannot give arguments to a program you are running from an
     archive.  Also, 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.
















     ARC                                                           Page   9

     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.



     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  10

                                   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.




















     ARC                                                           Page  11

     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.

























     ARC                                                           Page  12

     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























     ARC                                                           Page  13

     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.
















     ARC                                                           Page  14

                                 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 one
     most often used is "$ARCTEMP.CRN", which is created (if possible) when
     adding a file to an archive.  The Convert command uses a file named
     "$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  15

                                      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

     Though it would probably be faster to type:

         COPY waste.arc junk.arc
         MARC junk trash


     If MARC is invoked with no arguments, then it gives brief directions
     in its use.








     ARC                                                           Page  16

                                      XARC



     XARC is a separate program which is used to extract all files from one
     or more archives.  It doesn't do anything that ARC doesn't do, and it
     isn't any faster, but it may be preferred in certain cases, as it is
     much smaller than ARC.


     XARC is used as follows:

         XARC <arcname> . . .

     Where <arcname> is the name of one or more archives.  The wildcard
     characters "*" and "?" may be used.  All files are extracted from the
     named archives.


     For example, if you wanted to extract everything from two archives
     named "WASTE.ARC" and "JUNK.ARC", you could type:

         XARC waste junk

     If you wanted to extract every file from every archive in a
     subdirectory named "TRASH", you could type:

         XARC trash\*.arc


     If XARC is invoked with no arguments, then it gives brief directions
     in its use.


























     ARC                                                           Page  17

                                 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.  This is reflected by our own
     habit of referring to "version 4.5" instead of "version 4.52".






























     ARC                                                           Page  18

                             PROGRAM UPDATE SERVICE



     A license to ARC entitles you to use all future versions of ARC.  New
     versions are generally available through normal freeware distribution
     channels, and we prefer that you obtain them that way.  However, many
     users of ARC have written to ask us about an update service.

     A program disk containing the latest version is returned on every
     order of $50 or more.  If you wish to purchase a single-user license
     and want an update disk, please enclose a check or money order for $50
     instead of $35.

     For a fee of $50 per year you can subscribe to our program update
     service.  Subscribers get up to five program updates per year mailed
     to them as new versions come out.  This does not include trivial
     releases.








































     ARC                                                           Page  19

                          COMMON QUESTIONS AND ANSWERS



     Here are some of the more common questions we've received about ARC,
     along with their answers:


     Q: Why do you bother with squeezing when crunching is so much faster?

     A: Because crunching isn't really as fast as it looks.  Crunching is a
        one pass operation, while squeezing requires two passes.  ARC
        actually does the crunching during the analysis pass, and puts the
        crunched output in a file named "$ARCTEMP.CRN".  If crunching turns
        out to be the best method, then this temporary file is copied into
        the new archive.  In other words, when ARC says "crunching" it
        isn't really crunching, it's just copying a file.

        Also, there are a lot of files out there that squeeze MUCH better
        than they crunch.


     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.  ARC also needs room for the temporary file used in
        crunching.

        You can save some space by using the ARCTEMP environment string to
        put the temporary file on another disk, as well as 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.








     ARC                                                           Page  20
     Q: Can I use ARC to distribute my public domain or freeware program?

     A: Yes, of course.


     Q: Can I use ARC to distribute my commercial software package?

     A: Yes.  Please contact us for a commercial distribution license.


     Q: I'm a commercial user.  Why should I pay for freeware that others
        get for free?

     A: Because you cannot credibly plead poverty.  Freeware, ALL freeware,
        is an attempt to develop a new marketing channel to the benefit of
        everyone.  You can still "test drive" freeware 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.


     Q: How can I get the latest version of ARC?

     A: ARC updates are distributed through normal freeware channels, and
        by FidoNet.  We also ship a program update disk on every order of
        $50 or more.  In addition, we also offer an update subscription
        service.  See the previous section for more details.























     ARC                                                           Page  21

                                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 file
     transmission time.

     As usual, ARC version 4.0 is completely upward compatible.  That is,
     it can deal properly with any archive created by any earlier version
     of ARC.  It is NOT reverse compatible.  Archives created by ARC 4.0
     will generally not be usable by earlier versions of ARC.










     ARC                                                           Page  22
     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.

     Version 4.1 is still fully upward compatible.  But regretfully, it is
     again not downward compatible.  Version 4.1 can handle any existing
     archive, but creates archives which older versions (including 4.0)
     cannot unpack.



     CHANGES IN VERSION 4.3

     Version 4.3 adds the much-demanded feature of using pathnames when
     adding files to an archive.  For obscure technical reasons, files
     being extracted still go in the current directory on the current
     drive.  Pathnames are also not supported for any of the other
     commands, because it would make no sense.

     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  23
     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  24
     CHANGES IN VERSION 5.0

     Several users of ARC have written us to suggest that we should put an
     order form in the documentation.  It seems that several types of
     organizations require something like that or they cannot pay no matter
     how much they'd like to.  While doing that, we also went over the
     documentation from top to bottom and "slicked it up".  It's now a bit
     more of an actual manual.  We think you'll appreciate the table of
     contents as well; we sure do!

     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  25
     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.

     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 documen-
     tation, 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.



     ARC                                                           Page  26

                           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 more 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.  Now (in October of 1985) we find that our humble
     little program has 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.

     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.


     And many, many others whom we could not identify.





     ARC                                                           Page  27

                                  SITE LICENSE



     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 copies  $35 each
         10 to 24 copies  $25 each
         25 to 49 copies  $20 each
         50 to 99 copies  $15 each
         over  99 copies  $1500 one time fee



     The following page is a site license agreement, which should be signed
     and sent with your payment when ordering a commercial site license.






































     ARC                                                           Page  28

     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.  The fee is based on the number of computers which
         will be used to run ARC, as follows:

               1 to  9 copies  $35 each
              10 to 24 copies  $25 each
              25 to 49 copies  $20 each
              50 to 99 copies  $15 each
              over  99 copies  $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 copies, 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.  The
         latest version is available from System Enhancement Associates for
         a small service charge.

     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.

     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



     ARC                                                           Page  29

                                   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
             price schedule and terms on preceding page).

         (_) Program disk and documentation (only on orders of $50 or
             more).

         (_) Program update subscription service (not more than five
             updates, does not include trivial changes), $50/year.

         (_) Payment of $_____ is enclosed (check or money order).

         (_) Please charge $_____ to my (_) Visa or (_) MasterCard:

             Card number: ______________________________

             Expiration date: __________________________

             Signature: ________________________________

         _______________________________________________
         Name

         _______________________________________________


         _______________________________________________
         Address

         ______________________   ________  ____________
         City                     State     Zip

         _______/_______
         FidoNet address


     Send this completed form to:

                          System Enhancement Associates
                                  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.




     ARC                                                           Page  30