DECC$FIXED_LENGTH_SEEK_TO_EOF

   With DECC$FIXED_LENGTH_SEEK_TO_EOF enabled, lseek, fseeko, and
   fseek with the direction parameter set to SEEK_END will position
   relative to the last byte in the file for files with fixed-length
   records.

   With DECC$FIXED_LENGTH_SEEK_TO_EOF disabled, lseek, fseek, and
   fseeko when called with SEEK_EOF on files with fixed-length
   records, will position relative to the end of the last record
   in the file.