Intel(R) Fortran Compiler for Linux* Systems User's Guide Volume I ...

Intel® Fortran Compiler for Linux* Systems User's Guide, Volume I: Building
Applications
FORT_CONVERT.dat, FORT_CONVERT_dat, or F_UFMTENDIAN indicates native
little endian data for unit 20.)
OPEN (CONVERT='VAXD', FILE='graph3.dat', FORM='UNFORMATTED', UNIT=15
.
OPEN (FILE='graph3_t.dat', FORM='UNFORMATTED', UNIT=20)
A hard-coded OPEN statement CONVERT keyword value cannot be changed
after compile time. However, to allow selection of a particular format at run time,
equate the CONVERT keyword to a variable and provide the user with a menu
that allows selection of the appropriate format (menu choice sets the variable)
before the OPEN occurs.
You can also select a particular format at run time for a unit number by using one
of the environment variable methods (FORT_CONVERTn,
FORT_CONVERT.ext, FORT_CONVERT_ext, or F_UFMTENDIAN), which take
precedence over the OPEN statement CONVERT keyword method.
OPTIONS Statement Method
You can only specify one numeric file format for all unformatted file unit numbers
using this method unless you also use one of the environment variable methods
or OPEN statement CONVERT keyword method.
You specify the numeric format at compile time and must compile all routines
under the same OPTIONS statement CONVERT keyword qualifier. You could
use one source program and compile it using different ifort commands to
create multiple executable programs that each read a certain format.
The environment variable methods and the OPEN statement CONVERT method
take precedence over this method. For instance, you might use the environment
variable FORT_CONVERTn method or OPEN statement CONVERT method to
specify each unit number that will use a format other than that specified using the
ifort option method.
This method takes precedence over the convert keyword compiler option
method.
You can use OPTIONS statements to specify the appropriate floating-point
formats (in memory and in unformatted files) instead of using the corresponding
ifort command qualifiers. For example, to use VAX F_floating and G_floating as
the unformatted file format, specify the following OPTIONS statement:
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