Summary:
  Use calls to Windows API I/O functions to avoid 2 problems:
    Fortran DLLs cannot read or write to binary or unformatted files
    Files opened in a DLL called from VB 2.0 may not close consistently

This file contains:

   fortio.def   Example module definitions file
   fortio.for   Example Fortran DLL file
   fortio.mak   Make file for example
   huge.def     Module definitions file for hread and hwrite API
   legal.txt
   readme.txt   This file
   test.for     Test program to use fortio.dll
   dll-io.zip   Zip file containing all the other files

More Information:

The following Fortran code 'fortio.for' demonstrates how to access files
using the Windows API for file I/O.

Binary Data I/O:
  The example below defines 'bfread' and 'bfwrite' to use a REAL*4 data
  buffer (in the interfaces to the Windows API functions '_hread' and
  '_hwrite'). Additional interfaces could be used to define function
  names which use buffers of different data types (compare the interface
  statements for 'bfread' and 'hread', and read the comments in
  FORTIO.FOR).

File I/O in a DLL called from Visual Basic 2.0 or later:
  A file which is opened and closed with standard Fortran I/O statements
  may not be accessable by anything until the VB application exits. A
  file which is opened/created, accessed, and closed using the Windows
  API I/O functions can be read or written by VB or any other
  application as soon as it is closed.

This example contains interfaces to '_hread' and '_hwrite' rather than
'_lread' and '_lwrite' (which can only access data items less than 64K,
but may be slightly more efficient for small data items). The library
'huge.lib' created from 'huge.def' is required to reference the huge
version of 'read' and 'write' defined in version 3.1 of the Windows API.
Only references to Windows 3.0 functions are provided in LDLLFEW.

The Windows API functions return -1 if an error occurs.

To run the example: type
  nmake -f fortio.mak
at the dos prompt, and then run 'test.exe' from File Manager in Windows.


NOTE: The following line in 'FORTIO.MAK' may need to be modified to
reflect the actual path-name for 'FL.DEF'.

   link /NOD test.obj,,nul,llibfew+fortio.lib,c:\fortran\binb\fl.def;

This assumes the default directory name for the 'FL.DEF' file. If 'FL.DEF'
is not in 'c:\fortran\binb', the following error will occur:

   LINK : fatal error L1092: cannot open module-definition file


For additional information on the Windows API functions, look in any
reference manual of Windows Functions (such as the Windows SDK
Programmer's Reference Volume 2: Functions).