-------------------------------------------------------------------------- RAR Frequently Asked Questions (FAQ) Copyright 1994 Eugene Roshal. All rights reserved. 15-Aug-1994 -------------------------------------------------------------------------- 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. -------------------------------------------------------------------------- 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*.*". -------------------------------------------------------------------------- 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 likely to be much faster than the "store" method, as there will be much less information to write. 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 -------------------------------------------------------------------------- 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. -------------------------------------------------------------------------- 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. -------------------------------------------------------------------------- end of file "RAR_faq.txt"