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

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

  Why do I get the message "Bad Command or Filename"?

  If you see this message, DOS is telling you it can't find the program you
  are referring to.  This can happen because you are either not spelling the
  name of the program properly, or you didn't put a space between the
  program name and its options, or the program is not in your path.

  Please see the Installation section and your DOS manual for more

  Why is this program so complicated?

  PKZIP initially was used to compress files that would be sent by modem.
  The people using PKZIP were mostly hobbyists with a fair amount of
  computer experience.  PKZIP was designed to be powerful and fast.

  Someone who is familiar with the workings of PKZIP can be very efficient
  with the command line.  The command line interface is vital for automated
  or batch use of PKZIP.

  Although PKZIP may seem very complex at first, it is easy to master if you
  take one step at a time.  Start simply by following the Tutorial, then
  experiment and build on that knowledge as you need more features.

  Users who prefer using Graphical User Interfaces may wish to consider the
  "PKZMENU" product from PKWARE.  This easy to use menu-driven program
  offers PKZIP compatibility.  It features drop-down menus and a simple
  point and shoot interface.

  Why didn't the files I Zipped get any smaller?

  On occasion, you may find that the files you add to a .ZIP file do not
  compress.  These files will be "stored".  This will happen when a file is
  either already compressed or encrypted.

  In both cases the redundancy of the file will be gone, making compression
  difficult if not impossible.  If the file is encrypted you should first
  save it without encryption, and then use the encryption feature of PKZIP.

  You will often find that files distributed with commercial applications
  are already compressed.  A common example would be the graphic data files
  that come with games like Leisure Suit Larry or Ultima.

  I zipped up a bunch of files but now I have LESS disk space!?

  When PKZIP compresses files, it makes a copy of the original file.  The
  original file(s) are still present.  If you wish to recover space that was
  taken up by the original file(s), you must either delete them yourself, or
  instruct PKZIP to delete the file(s) with the -m option.

  What's the difference between -u and -f?

  The update and freshen options are very similar.  This may be confusing at
  first, but the difference between them is fairly easy to understand.

  The freshen option will tell PKZIP to archive any files which match those
  already in the .ZIP file.  These files will only be re-compressed if they
  are newer than the files already in the .ZIP file.  Each file is evaluated

  The update option will archive all files, with one distinction.  If the -u
  is not used, all files specified will be compressed and added to the .ZIP
  file, even if they already exist in the .ZIP file.  By using the -u
  option, you instruct PKZIP to compare what is already in the .ZIP file
  against what it was asked to compress.  If a file is already present in
  the .ZIP file and is also in the source directory, PKZIP will compress a
  file only if it is newer than the copy of the file within the .ZIP file.
  If a file in the source directory is not already present in the target
  .ZIP file, PKZIP will add it to the .ZIP file.

  Is PKZIP compression "lossy" or "lossless"?

  PKZIP uses a "lossless" compression scheme.  This means that 100% of the
  original data is preserved and re-created.  There is absolutely no
  difference between the data that you put in and the data which you get
  back out.

  There are other compression methods that are known as "lossy".  The idea
  behind these compression methods is that if you throw away some of the
  data, it becomes less complex and therefore can be compressed more.  This
  type of compression is only useful for data that need not be precise.
  This applies to some applications that use pictures and sound.

  How do I zip up subdirectories?

  In order to ZIP up subdirectories you must both recurse subdirectories and
  preserve path names.  This is done with the -r and -p options in
  combination.  The options may be placed together as -rp.

  When a .ZIP file is created with paths stored, these paths will be visible
  in a view of the file (-v).

  To re-create these subdirectories, or to place files into their original
  subdirectories, the -d option must be used with PKUNZIP.

  Please see the tutorial for more information.

  I zipped up some subdirectories, but I can't get them to come back?

  Did you remember to use the -p option in addition to the -r option? You
  may have stored files that are in subdirectories but not preserved the
  path names as part of the .ZIP file.  To check if there are paths in the
  .ZIP file, do a view of the file:

     pkunzip -v

  If you do not see paths as part of the file names within the .ZIP file,
  then paths were not stored and cannot be recovered.  If you do see paths
  all you need to do is use the -d (directory creation) option when you
  extract the files.

  How do I unzip a single file that is in a subdirectory in the .ZIP file?

  Extracting a particular file from a .ZIP file is simple.  You type PKUNZIP
  with the name of the .ZIP file and the name of the particular file you
  want.  With a .ZIP file that contains paths the procedure is basically the

  Let's assume a "test" .ZIP file with these files in it:


  To extract only "file2.txt" from this .ZIP file you must specify the
  complete name.  This would include the path.

     pkunzip apple\file2.txt

  Note there is no leading slash.  This is how PKUNZIP differentiates
  between the files you are extracting with paths, and the target directory.
  "file2.txt" would be extracted to the current directory.  If you wanted to
  extract it with its subdirectory simply include the -d option on the
  command line.

  How do I unzip a directory without also extracting its subdirectories?

  Using the above "test" .ZIP file we could extract the entire contents of
  the apple subdirectory easily:

     pkunzip apple\*.* -d

  If we did it as shown above we would not only extract all the files in the
  "apple" subdirectory, but also the "banana" subdirectory below it and any
  files it contains.

  To extract only the "apple" subdirectories contents, and nothing else, we
  must exclude those directories we do not wish to extract:

     pkunzip apple\*.* -d -xapple\banana\*.*

  If the "apple" subdirectory had multiple subdirectories off it you would
  need to exclude each one individually on the command line.

  What is an AV?

  AV is short for "Authenticity Verification".  AV is a process whereby a
  copy of PKZIP has unique codes and information contained in it identifying
  the owner of the copy of PKZIP.  This information is then encoded into a
  .ZIP file when it is created.

  When the file is extracted by PKUNZIP, this information is checked.  If
  the .ZIP file has been modified by a copy of PKZIP other than the one
  which initially created it, PKUNZIP will report that the file has been
  tampered with.

  The advantage of this feature is to offer a layer of protection between
  the creator of an archive and the recipient.  The recipient knows that the
  file received is the file that was sent, as well as being able to identify
  the creator if it is not known.

  Where is my AV number?

  As a licensed user of PKZIP you are entitled to one AV number.  In order
  to receive an AV number, you must apply for it.

  If you have a need to create AV encoded .ZIP files, fill out the form
  contained in the file "authveri.frm" found in your PKZIP archive.  Mail or
  fax this form to PKWARE.  Please allow up to four weeks for processing
  time, plus mail delays.  The codes needed to install your AV number will
  be returned to you via US Mail.  AV codes will not be returned by FAX,
  telephone, or any means other than US Mail.

  Please note that although the initial AV code is included with your
  purchase of a PKZIP license, changes or re-issues of an AV code may be at
  an additional cost.

  You must apply for your AV number.  The serial number on the disk PKWARE
  sent to you has no relation to the AV number.  The AV number is based
  solely on the information you provide for your AV identification string on
  the AV application form.

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