******************************************************************
**                                                              **
**                IBM PC Installation of GCL                    **
**                                                              **
**  Contents:  1.)  Introduction                                **
**             2.)  Check the Contents of the Disks             **
**             3.)  Installation of GCL                         **
**             4.)  Using Super VGA Cards                       **
**                                                              **
**  Date   :   30.11.1996                                       **
**  Version:   2.1     /  MS-DOS                                **
**  Author :   Helmut Michels, MPI fuer Aeronomie,              **
**             Postfach 20, D-37189 Katlenburg-Lindau           **
**             E-mail: michels@linax1.mpae.gwdg.de              **
******************************************************************

1.)  Introduction
   
     This file describes the installation of the  graphics command
     language  GCL  which is an interpreter  based on the graphics
     software DISLIN.  All  DISLIN  statements can be written to a
     script file and then be executed with GCL,  or can be entered
     in an interactive mode.

     Similar to programming languages such as Fortran and C, high-
     level language elements can be used within GCL. These are va-
     riables, operators, expressions, array operations, loops,  if
     and switch statements,  user-defined  subroutines and functi-
     ons, and file I/O routines.

     An easy to use  interface  for data input is given to include
     data into  GCL jobs.  The format of data files is very simple
     and useful for most DISLIN plotting routines.

     Several quickplots are offered by  GCL  which are collections 
     of DISLIN statements to display data with one command.

     Notes: 

      - An installation of DISLIN is not necessary for GCL.

      - The source code is compiled with GNU GCC 2.7.2  ported for
        IBM PCs  from  DJ Delory.  You must have installed GNU GCC 
        version 2.0 to run GCL (GCL needs the extender).

      - This version of GCL is free software;  you can make copies
        and redistribute it.  The software is  distributed  in the
        hope that it will be useful, but WITHOUT ANY WARRANTY.

2.)  Check the Contents of the Disks

     The GCL distribution disk contains the following files:

     DISLIN.INF
     README.INF
     GCL_21.ZIP      
     UNZIP.EXE
 

3.)  Installation of GCL

     The  MS-DOS  version of  GCL  is distributed as a  .zip  file 
     created with the file packaging utility ZIP (version 1.9).
     The .zip file has the file name  GCL_nn.ZIP  where  nn is the
     current version number of GCL.

     To install GCL, make the following steps:

  a) Create a temporary directory and copy all files from the
     distribution disk to the directory:

     for example:   md  c:\temp
                    cd  c:\temp
                    copy a:\*.*  *.*

  b) Extract GCL files with the command:

                    unzip -o GCL_21 

  c) Run the install program with the command

                    INSTALL c:   (or INSTALL d:)

     The program INSTALL installs GCL in the directory c:\DISLIN
     (or d:\DISLIN).

  d) Reconfigure the System

     Add the DISLIN\DJGPP directory to the PATH environment in the
     file AUTOEXEC.BAT

     for example:  PATH C:\BIN;C:\DISLIN\DJGPP;C:\DJGPP\BIN

     Define the environment variable DISLIN in the file
     AUTOEXEC.BAT:

     for example: SET DISLIN=c:\dislin

  e) Check the installation by running the examples

     Type:    gcl  curve
       or:    gcl  surface
       or:    gcl  pie
       or:    gcl  bars
       or:    gcl  world
       or:    gcl  contour

     The examples can be found in the directory:  \dislin\gcl


4.)  Using Super VGA Cards
     
  a) If the environment variable GRX20DRV is defined, DISLIN uses the
     GRX20 library to display graphics on the screen.

     For example: set GRX20DRV=et4000 gw 1024 gh 768 nc 256

     This method is fast and should be used for Super VGA cards.    

  b) If the environment variable GRX20DRV is not defined, DISLIN uses BIOS
     calls to display graphics on the screen.  Special graphic modes can
     be defined with the utility program  DISVID (see DISVID).

     This method is slow and can be used if method a) is not available.

   

  Notes: 

  -  Elementary image routines such as rtiff, rimage and wpixls can only
     be used with method a) and with a full colour mode (nc 256 in GRX20DRV).


