0) Perple_X on OSX is a pain in the neck and you can thank Apple for that. The
   instructions (1) below assume that someone has compiled the most recent 
   release and that this release will run on your computer. Often this is 
   not true, the compiled versions usually lag the current release and
   may also require that you install the quadmath library. Alternative ways of 
   getting and/or running Perple_X on OSX include:

   A) Clone github.com/jadconnolly/Perple_X, install GFortran, and 
      compile the programs yourself. This is not as bad as it sounds and 
      no more complicated than trying to install a missing quadmath library.
 
   B) Extract the precompiled OSX binaries from the Julia package manager as 
      described at: github.com/jadconnolly/Perple_X?tab=readme-ov-file#perple_x.
      This also sounds complicated but people have done it successfully.

   C) Use a WINDOWS emulator to run the WINDOWS release.

1) Go to www.perplex.ethz.ch/perplex/ibm_and_mac_archives/OSX

   The program archives are named Perple_X_#.#.#_***.zip where #.#.# is the release
   number (e.g., 6.8.6) and *** indicates compiler, system and/or author information.

   The OSX versions are provided courtesy of third parties. As of Feb 22, 2019
   the two third party authors/versions are both compiled with GFortran:

   JS - John Schumacher, Bristol - is dynamically linked.

   MC - Mark Caddick, Virginia Tech - is statically linked.

   The compiler options used to generate these versions can have major performance
   consequences. Perhaps more importantly, dynamically linked versions will (usually)
   require that you install the gcc libraries. To install these libraries refer
   to groups.io/g/PerpleX/message/1658, also check for more recent discussion of
   the topic.

   The OSX versions may not be current. Check the update file:

   www.perplex.ethz.ch/perplex_updates.html

   to establish whether the archive contains programs with bugs that may have 
   consequences for you.

   Choose and extract the programs from the archive of your choice to a single directory. 

   If you wish to compile your own version of Perple_X, contact me and I will provide
   you with the current link for the FORTRAN sources. 

2) Extract the Perple_X data files in:
 
   www.perplex.ethz.ch/perplex/ibm_and_mac_archives/Perple_X_#.#.#_data_files.zip 

   to the same directory as in step 1. Select the version #.#.# closest to the
   program version #.#.# in step 1, but do not use data files with a higher release
   number than the program release number.

3) Run Perple_X programs from a shell (aka terminal window). Configure the shell 
   so that the directory in step 1 is the default current working directory. Running 
   Perple_X by clicking on the program icons can cause confusion, but, if you
   insist, then refer to the instructions at:

   www.perplex.ethz.ch/perplex/ibm_and_mac_archives/OSX/DoubleClickPerplex.pdf

   additional useful Apps are at:

   www.perplex.ethz.ch/perplex/ibm_and_mac_archives/OSX/Perple_X_OSX_Apps.zip 

4) Follow the remaining instructions at 

   www.perplex.ethz.ch/perplex/ibm_and_mac_archives/README_COMMON_INSTRUCTIONS.txt