You can access regular operating-system files and blocked special files by using either sequential-access or direct-access methods.
You can only access pseudo-devices, pipes, and character special files by using sequential-access methods.
When you link files together, you can use their names interchangeably, as shown in the following example:
OPEN (4, FILE="file1") OPEN (4, FILE="link_to_file1", PAD="NO") ! Modify connection
Do not specify the POSITION= specifier as REWIND or APPEND for pipes. REWIND is allowed for tapes, but APPEND is not. To open a tape file at a specific location, use the tctl command to position the tape before running the Fortran program, and specify POSITION='ASIS' in the program.
Do not specify ACTION='READWRITE' for a pipe.
Do not use the BACKSPACE statement on files that are pseudo-devices or character special files (such as tapes).
Do not use the REWIND statement on files that are pseudo-devices or pipes. If used on a tape, it rewinds to the beginning of the file, not the beginning of the tape.