date:     December 7, 1984
           
          to:       HGraph DECUS Users
           
          from:     Dennis V. Jensen
                    Ames Laboratory
                    310 Metallurgy
                    Ames, Iowa  50011     515/294-4823
           
          subject:  HGraf3 - An HGraph DECUS Release for REGIS.


               The initial DECUS release of HGraph was at the Fall
          1983  Symposium.   Release one was coded entirely in DEC
          Fortran 66 compatible  code.   The  second  release  was
          distributed  at  the Spring 1984 symposium.  Included in
          the second  release  was  a  new  WRTSTR  (extracted  as
          WRTST2.*)  which  would  generate  characters as vectors
          (stroke font);  it was not dependent on  any  particular
          terminal's  character  generator.   Also, included was a
          cubic  spline   interpolation   line   drawing   routine
          (extracted  as  SMOOTH.*)  which was compatible with the
          DASHLN  calling  convention.   HGR550  files   on   this
          distribution are the same as the second release (Hgraf2)
          files which support the Visual 550 (TEK4014  compatible)
          and the Bausch and Lomb DMPL plotters.

               This  third  release  includes  support  for  REGIS
          compatible  terminals.   It  was initially developed for
          the VT-125 terminal although it should work  with  other
          REGIS compatible terminals.  Refer to the VT125.DOC file
          for information on which modules were modified to  adapt
          Hgraph to this terminal;  it includes insights as to the
          conversion for other terminals if users  would  like  to
          make changes.  The HGR125 files support a REGIS terminal
          and the Bausch and Lomb DMPL plotters.

               Hgraph is coded in FLECS.  This structured  Fortran
          code   is  contained  in  the  .FLX  files.   The  FLECS
          generated Fortran 66 code is in  the  .FOR  files.   The
          HGraph  document  is  in  the  HGraph.DOC  file with the
          associated Runoff file as HGraph.RNO.   An  RT-11  FLECS
          translator  FLECS.*  (RE:   RT SIG Fall 81 Tape) is also
          included for reference.  Refer to the VAX  Fall  82  SIG
          Tape  [VAX82B.FORDAERO.UTIL.FORDUTIL]  (or  something to
          this effect) for a VMS FLECS  translator.   Other  Flecs
          translators  are  available from SIG tapes and the DECUS
          library.

               PLOT3D.FOR is included as a separate file.  A FLECS
          version is not included as it does not exist.  PLOT3D is
          known to have bugs, but will work for  many  of  the  3D
          plots   you  may  wish  to  do.   Although  considerable


          HGraf3 - HGraph DECUS Release - REGIS support.    PAGE 2



          development is occuring at the Ames Laboratory on the 2D
          versions  of  HGraph,  no  additional  work is currently
          planned for the 3D code;  PLOT3D should  be  treated  as
          unsupported.

               In general, you will find that the source  code  is
          quite   transportable   to   other   operating  systems,
          especially if you transport the .FOR files.  Hgraph  was
          designed  to  provide  graphics support on small systems
          but is quite extendable to larger systems.  

               You can look forward to a new interactive  graphics
          editor  called  UGraph  which is based on Hgraph.  It is
          menu   driven   and   requires   no   programming.    It
          unfortunately  is  getting  larger  though  and is being
          developed on the VAX.  An overlayed  version  for  small
          systems  may be possible, though.  It is running in test
          mode now and will likely be available in the  Spring  of
          1985.

               The following notes relate primarily to  Hgraph  on
          RT-11  (small)  systems.   They are included as they may
          help you isolate setup problems:

               When using HGRAPH it is  common  to  encounter  the
          message  "LINK-F-Library  list  overflow".  Increase the
          library list size with the /P switch when linking.   For
          example:
          		r link
          		prog/P:400=prog,sy:hgraph

               A  commonly  occuring  run-time  error  when  using
          HGRAPH is "?MON-F-Trap to 4 NNNNNN" or "Stack Overflow".
          This message likely indicates a lack  of  program  stack
          space.   The  solution  is  to  increase  the  amount of
          program stack space using the  /B  linker  option.   For
          example:
          		r link
          		prog/B:1400/P:400=prog,sy:hgraph
          The default value of B is 1000 octal.  This problem will
          undoubtedly be encountered when using threaded code.

               All code included in this distribution  is  in  the
          public  domain  and  may not be marketed for profit.  It
          may be altered without the explicit  permission  of  the
          authors.   Any  corrections or significant modifications
          to HGraph are of interest to  the  authors  and  may  be
          communicated  to  the  address  above.   The authors and
          their  employers  assume  no  responsibility   for   the
          correctness   or  the  appropriatness  of  the  software
          included in this distribution.