CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C                                                               C
C               F  O R T  _ S U B . F                           C
C                                                               C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C
C  Here is a module that contains an example of a FORTRAN subroutine
C  and its unit test driver. The pre-processor is used to handle
C  #defines and conditional compilation.

C
C Uncomment the following #define if you want DEBUG info.
C
/* #define DEBUG */

C
C Include some global constants. The Pre-processor can be used to 
C physically include the text from another file at the location of
C the '#include'. Here we're loading in a file of constants that
C might be used in this routine. Using this 'include' feature allows
C you to collect all of your #defines together in one file rather than
C having then sprinkeled along in the tops of lots of files.
C
#include "const.h"

#define  OUTFILE     'fout.dat'          /* Fortran Data Output File */
#define  NPTS        3

  
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C  								C
C UNIT Test driver to test the subroutine fort_sub		C
C								C
C Standalone main program to test routine: 'fort_sub'		C
C								C
C Parameter: 							C
C								C
C								C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
#ifdef UNIT_TEST

      PROGRAM SUB_UNIT
      REAL     PARAM1
      INTEGER  UNIT

 
      UNIT   = 6
      PARAM1 = 666.0

      write(6,*)'------------- FORTRAN SUBROUTINE UNIT TEST ROUTINE -----------'
      write(6,*)'Unit Testing the Fortran subroutine with parameter: ',PARAM1
      write(6,*) ''

C
C    Call the subroutine being tested with a variety of arguments
C      
      CALL FORT_SUB(PARAM1, UNIT)
      write(6,*)'Subroutine returned'


      END
#endif



  
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C  								C
C SUBROUTINE FORTRAN_SUBROUTINE					C
C								C
C Test subroutine to illustrate FORTRAN code			C
C								C
C Parameter: 							C
C								C
C    arg  - The first argument passed into the routine....      C
C    unit - The unit where the output should go   		C
C								C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

      SUBROUTINE FORT_SUB(arg, c_unit)
      REAL  arg                 
      INTEGER c_unit  
      REAL*8 X(NPTS)
      INTEGER I
 
C/*
C * Write some stuff to the ouput unit specified in the calling sequence. 
C * If the output unit hasn't been associated with a filename, this 
C * f77 compiler uses the convention of creating a file named, 'fort.#'
C * where the number is specified in the calling sequence.
C */ 

      write(c_unit,*)'-------------'
      write(c_unit,*)'Entering the Fortran routine with parameter: ',arg
      write(c_unit,*) ''
      arg = COS(arg)
      write(c_unit,*)'Replacing the argument with its cosine: ',arg
      write(c_unit,*)'-------------'

C
C   Here's a swatch of debugging code hidden behind the pre-processor 
C   directive 'DEBUG'. If this directive is set with '#define DEBUG' or set with the
C   compiler flag '-DDEBUG' , then this code will become active.
C
 
#ifdef DEBUG
C/*
C * Here some debugging code...
C */

500  CONTINUE
      write(c_unit,*) 'Put your debugging code in here'
      DO 510 I  = 1, NPTS
        write(c_unit,*) x(i)
510  CONTINUE
#endif


      RETURN

      END