The OPEN statement causes the referenced file or subfile to be opened.

<open statement>

── OPEN ── ( ──<open file part>─┬────────────────┬─ ) ─────────────────┤
                                └─<open options>─┘

<open file part>

──┬─<file designator>─┬───────────────────────────────────────┬────────┤
  │                   └─ [ ── SUBFILE ──<subfile index>── ] ──┤
  └─<task designator>── . ──<file-valued task attribute name>─┘

The OPEN statement can be used as an arithmetic function. You cannot use an OPEN statement inside another file I/O statement. For information on the values returned, see the File Attributes Programming Reference Manual.

The subfile index specifies the subfile to be opened. For more information on the subfile index, see CLOSE Statement. For more information on the file designator, see SWITCH FILE Declaration. For more information on the task designator, see TASK and TASK ARRAY Declarations.