                        ---------------------------------
                          LAYER1xx.EXE and LAYER2xx.EXE
                        ---------------------------------


AUTHOR
------
L. J. Barbour
Department of Chemistry
University of Missouri
Columbia, MO
65211
chemlb@mizzou1.missouri.edu


HARDWARE REQUIREMENTS 
---------------------
IBM compatible PC running at least DOS version 3.
VGA or SVGA graphics card and monitor (uses 640x480 resolution)
Hard disk
Mouse
(486 or faster PC preferable, but not necessary)


USAGE
-----
The programs read intensity data and will plot precession photo type pictures on screen.
Both programs are mouse-menu-driven and the menu options are activated by pointing to the 
option and clicking the left mouse button.  The menu options are pretty self-explanatory,
so I won't go into great detail describing them.  Since you're probably a scientist,
I encourage you to experiment with the menu selections.


LAYER1xx.EXE    (xx indicates version and will be incremented as updates are made)
-------------
Reads a SHELX-type HKL file which MUST have the .HKL extension.
The HKL file has to be edited to include a b c alpha beta gamma as the first line.
All numbers must be in free format with at least on space between them.
Reflection data follow from the 2nd line as:

h k l F sF
h k l F sf
h k l F sF
etc.

I use F and sF here, but of course it is preferable to have F^2 and sF^2 (SHELX type 4 data)
since they are a measure of the Intensity and its standard deviation.
However, if you only have SHELX type 3 data, the program can be made to square F for you.
The automatic generation of Friedels can be switched on and off.
The program is more informative if a hemisphere (or even better, a complete sphere - but who 
collects a sphere, anyway?) of data is contained in the HKL file.
Sometimes, if you are using F^2 data, the value for F^2 is so large that it is placed right next
to the L Miller index with no space in between.  If this occurs, the program will not be able 
to make sense of this reflection and it will be ignored.  However, a message will appear on 
screen telling you how many errors were encountered during the read.


LAYER2xx.EXE    (xx indicates version and will be incremented as updates are made)
-------------
Reads a CAD4 DAT file which MUST have the .DAT extension.
The cell parameters are extracted from the orientation matrix of the DAT file.
In addition, the filter factor for the machine is also extracted.
This value is not contained in DAT files written by older versions of the CAD4 control software,
and so will default to 15 for such data files.  However, if you know the value, you can change 
it from 15.


UPDATES
-------
As the programs get used, it is almost inevitable that bugs will be discovered.
I would be very grateful for any bug reports or comments about the program.  
Whenever I fix or update a program, I'll replace its predecessor in 
pub/xtallography/precess on sol.dmp.csiro.au and also increment xx in its name.  
I will also leave a note describing the update or bug-fix in this directory.


FUTURE PLANS
--------------
I will at some stage implement the use of a transformation matrix so that different settings
of the crystal can be explored.
I will also consider suggestions from users regarding modifications and additions to the programs.
The programs eflect that I only use CAD4 diffractometers and SHELX structure refinement software.
However, I may be willing to customise the programs for other sysems if so requested.
When I get time, I'll also put in a routine to allow hardcopy output as an HPGL file or
as a direct screen dump to an Epson compatible dot-matrix printer.



DISCLAIMER
----------
The author does not accept responsibility for the loss of life, limb or anything else 
resulting in the use of these programs.  However, should such an event occur, I
would appreciate being notified and will be happy to make changes in order to avoid
further disasters.



