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  Frequently Asked Questions PART II (F.A.Q.)

  This section lists some common questions about PKZIP and related subjects.
  We hope you will find this information helpful.

  I forgot my password, what do I do?

     1. Read the chapter "Using Data Encryption"
     2. Try to remember the password.
     3. Try passwords that are "close" to what you think it was.
     4. Try mixed upper and lower case versions of your password.

  There really is nothing that can be done if you lose or forget your
  password.  Don't forget or lose your passwords! PKWARE has no special
  means for "getting around" the encryption and may not be able to assist in
  the recovery of an encrypted file.

    | PLACE.  DO NOT TRUST YOUR MEMORY ALONE.                        |

  What does "Don't Know How to Handle" mean?

  There are many different methods of compression.  In the history of PKZIP
  alone there have been seven different methods to date.  The .ZIP file
  format was designed so that additional methods of compression can be added
  as they are developed.  In this way the .ZIP file format will never need
  to be abandoned.  If you attempt to extract a .ZIP file that was created
  with version 2.0 or higher with a lower version of PKUNZIP you will
  receive the message "Don't Know How to Handle" for every file compressed
  with a more advanced algorithm.

  If you attempt to extract a .ZIP file created with a version of PKZIP that
  includes a method PKZIP 2.0 does not use, you will receive a warning that
  will tell you what version of PKUNZIP you need.

  What is a CRC and why did it fail?

  CRC is short for Cyclic Redundancy Check.  A CRC is a value computed to
  represent the data content of a file.  The CRC is computed by PKZIP when
  it archives the file, and computed a second time when the file is
  extracted.  If the second CRC does not match the first CRC, then a change
  has occurred in the data.  The cause of a CRC failure can vary.  Here are
  some possible causes for CRC failures.

  I.  Failure on the machine that created the .ZIP file.

    A.  Failure immediately after creation.

      1.  On a 386/486 or higher there may be an obsolete or poorly written
          TSR or device driver interfering with PK(UN)ZIP.  Use the -3
          option with both PKZIP and PKUNZIP to see if this is the problem.
          Consult the Trouble Shooting section for more information.

      2.  "Clean boot" your machine.  Either re-name your autoexec.bat and
          config.sys files so that they are not loaded, or insert a DOS boot
          floppy and reset your machine.  Attempt extraction and compression
          of the file again.

      3.  The floppy/hard disk controller may be failing.  See if there is
          any difference in behavior if you compress to/from the hard disk
          or floppy drive.

      4.  Failing diskette media.

      5.  A bad memory chip.

      6.  Your computer is suffering from the "cache flaw".  This is caused
          by problems with the external CPU cache on your computer's
          motherboard.  See the Trouble Shooting section, -( option.

    B.  Failure after a period of time.

      1.  Any the above causes.

      2.  The file has been damaged during the time it was stored on the
          hard disk.  The can be caused by cross-linking or "lost" clusters.
          Some faulty disk-defragmenters and deletion recovery programs may
          cause this.

      3.  Deleting and then undeleting a .ZIP file.  "Undelete" programs are
          by no means flawless.  An undeleted or recovered file is very
          likely to fail, as most disk recovery programs are imperfect at

  II. Failure on a network server.

    A.  Some network server software does not run properly on 386/486
        machines.  If PKZIP is used on the server CPU running this faulty
        network software, it will be interfered with by the network

  III. Failure after transfer of a file by modem.

    A.  Any of the problems cited in section I may be the cause of a

    B.  There was an error in the transfer of the file.  Use an "error-
        correcting" protocol such as ZMODEM to avoid these types of

    C.  The file was transferred with "Kermit".  If you use Kermit you must
        set it to Binary mode.  PKZIP files are binary.

    D.  One of the computers or modems involved in the transfer has a

  IV. Failure after transfer by disk.

    A.  Any of the problems cited in section I may be the cause of a

    B.  Faulty disk controller/floppy drive.

    C.  Faulty floppy disk.

      1.  The drive alignment between the two computers may be off enough to
          cause a data error.  Normally you will get a "disk failure"
          message from DOS.

      2.  The disk was damaged by a magnetic or heat source.

      3.  The disk media is worn out or defective.

  What do "Bad Table" and "Inconsistent Local Header" mean?

  If you receive either or both of the above messages, the .ZIP file is
  damaged or has been tampered with.  These messages may also be accompanied
  by a CRC failure.

  All of the physical causes listed for CRC failures apply as possible
  causes of these errors.

  How can I make PKZIP run faster?

  PKZIP defaults to a compression method that is average in both compression
  amount and speed.  If you want to get the most speed out of PKZIP there
  are several things you can do:

    1.  Specify a faster compression method with the -ef or -es option.

    2.  Use a large RAM disk as your temporary files drive.
        PKTMP=(RAM disk drive letter)

    3.  If you are creating the .ZIP file on a network drive, set your PKTMP
        equal to a drive on the same server.

    4.  Make as much conventional memory available as possible.

  How many files can be in a .ZIP file?

  A .ZIP file may contain a maximum of 16,383 file entries under MS-DOS.
  Due to memory limitations this limit cannot actually be realized.  Under
  the current memory scheme of DOS the largest number of files which may be
  in a .ZIP file is approximately 9000 files.

  The maximum number of files you can handle with a .ZIP file operation can
  be calculated by the following formulas:

  With No EMS or UMB's available:

     (Free Conventional RAM - 375k) / 64 bytes = Maximum # of Files

  With EMS available:

     (Free Conventional RAM - 85k) / 64 bytes = Maximum # of Files

  The "Super Fast" algorithm uses 32k less RAM than the other methods in
  PKZIP 2.  You will be able to compress an additional 500 files when using
  the "Super Fast" method.

  Note that the value of 64 bytes per file is approximate and may vary.

  When a .ZIP file is being updated, you must not only take into account the
  files being added, but allow 70 bytes per file in the original .ZIP file.

  Can I send a .ZIP file to a different type of computer?

  As of the publication of this manual, PKWARE currently supports PKZIP on
  MS-DOS and OS/2 platforms, PKWARE intends to support additional platforms
  and will announce these as they become available.

  Because PKWARE has dedicated the .ZIP file format to the public domain, it
  is possible for other people to write programs which can read .ZIP files.


  We are currently aware of PKUNZIP compatible programs for a number of
  different platforms.  A .ZIP file can be transferred to any platform for
  which you can find a compatible extraction program.

  Extraction and Compression programs not developed by PKWARE may not be
  completely compatible with the .ZIP file standard.

  Contact PKWARE for a list of platforms for which PKZIP and PKZIP
  compatible software is available.

  What is the difference between -b and pktmp?

  PKZIP creates two different types of temporary files, and allows you to
  specify the location for these two types separately.  The two situations
  where PKZIP creates temp files are:

     * When a file is being added to a .ZIP file.

     * When a .ZIP file is being modified.

  It is advantageous to have the temporary files for the first instance
  written on the fastest drive on your system, unless you are creating a
  .ZIP file on a Novell Network.

  The location for the temporary .ZIP file created when a .ZIP file is
  modified is normally the same as the location of the original file.  In
  some cases you may not have enough room on that drive.  When this occurs
  use the -b option to relocate the temp file.

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