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                    RAR Frequently Asked Questions (FAQ)

            Copyright 1994 Eugene Roshal.  All rights reserved.

                               16-Dec-1994

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Published by Eugene Roshal with assistance from the users of RAR, UNRAR,
related utilities, and the RAR support sites.  This document may be freely
distributed for non-commercial and information purposes.  This document 
may not, under any circumstance, be traded, sold, or otherwise used for 
commercial gain or purposes without prior written consent of Eugene 
Roshal.
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Q: While I can see that RAR is a great program with a terrific user 
   interface, there appear to be no facilities available to convert my 
   existing archived files to RAR format.

A: There are no built-in facilities in RAR to handle this, in order to 
   keep the code size small.  A number of batch files are available from
   your local RAR support site which can assist in this process, but for 
   more complex situations we would recommend the "MTA" program by Robert 
   van Hoeven.  Robert may be contacted via electronic mail and his 
   programs are available on all good BBSs.  Look for "MTA*.*".
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Q: RAR incorporates a number of different compression "methods", what are
   the advantages and disadvantages of using them and which one would you 
   recommend for daily use?

A: RAR contains 6 different methods of compressing files, which one you 
   use would depend upon your requirements.  i.e. how much you demand the 
   file be compressed balanced against how much time you are willing to 
   devote to the compression process.  There is always a trade-off and the 
   final choice must be yours.  Our recommendation is to leave compression
   as "Normal" unless you have good reason to change it. 

     Store         No compression is used at all, the files are simply 
                   collected into the archive.  This method is quite fast
                   and is useful for simply copying files from one place 
                   to another.
     Fastest       The fastest compression method is applied.  This is
                   slower than the "store" method.
     Fast          A slightly better compression method is used, resulting
                   in a smaller file.
     Normal        A better compression method is used to achieve (almost)
                   optimal compression, at a slight cost in time.
     Good          A better compression method gains another increase of 
                   (0.1 - 0.3%) 
     Best          Uses the best compression method of all at the cost of
                   20% - 100% more time, for the purists only.

   Here are the results of a compression test:

    Method used   Time taken     %    Compressed size     %

       -m0          16.75     104.5        376824      100.00
       -m1          15.38     100.0        226846       60.20
       -m2          15.66     101.8        223515       59.30
       -m3          16.20     105.3        221282       58.70
       -m4          17.41     113.2        220774       58.57
       -m5          18.23     118.5        220720       58.57

   As you can see, as the packing method improves, the time required 
   increases, but the increase in time is proportionally much greater than 
   the gain acheived.  This why the default and recommended method is set
   to -m3    
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Q: I've heard a lot about "Solid" archives.  What are they and how can I use 
   them?

A: It has been well known, for a long time, that one method of increasing 
   the efficiency of compression, was to copy all the files to be compressed
   into a single file, before compressing them. This is called creating a
   "Solid" file before compressing. There are programs around which indeed
   perform this operation and act as a pre-processor to another archiver.
   RAR handles this function internally and invisibly to the user, it
   simply "sees" all files together as a single data stream, with the
   end result that the final output is significantly smaller than it would
   otherwise be.  The gain to be had from this type of archive can be
   significant and can be 10% - 60% of the size of the original archive.

   As with any other gain, there is a price to be paid and that price should 
   be taken into consideration before creating a "Solid" archive.  The best 
   way to understand if using a solid archive is best for you is to answer 
   the following questions:

   Q: How often are you going to update or modify the archive?

   A: Probably never       ..  Use a solid archive

      Rarely               ..  Use a solid archive

      Frequently           ..  Use a normal archive

   Q: Are you using RAR as a packer for an electronic mail system?

   A: Yes                  ..  Use a solid archive

   Note:  Use RAR versions 1.52 or greater to manipulate solid archives.
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Q: How could a user of my BBS (E-mail system, FTP server etc) extract
   files from RAR archives while RAR is shareware and one must register
   after a 40 day evaluation period?

A: The RAR distribution archive contains a free unRAR utility, UNRAR.EXE,
   which can be used, without paying a license fee, by anyone wanting to 
   extract archives created by RAR.
   Besides, there is the unRAR portable source code available.
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end of file "RAR_faq.txt"


