IOSTAT

 Designates a variable to store a value indicating the status of a
 data transfer operation.  It takes the following form:

 IOSTAT = ios

 ios   Is a scalar default integer variable.

 If no error exists, "ios" is defined as zero.  If an error exists,
 "ios" is defined as a positive integer.

 IOSTAT applies only to the OPEN statement in which it appears and
 not to subsequent I/O operations on the logical unit that is
 opened.  However, you can use the IOSTAT parameter in subsequent
 I/O statements to perform a similar function.

 Secondary operating system messages do not display when IOSTAT is
 specified.  To display these messages, remove IOSTAT or use a
 platform-specific method such as a VMS condition handler.  (For
 more information, see the HP Fortran for OpenVMS User Manual.)