The READWRITE specifier asks whether a file can be both read and written to. It takes the following form:

READWRITE = rdwr

rdwr

Is a scalar default character variable that is assigned one of the following values:

' YES '	If the file can be both read and written to
' NO '	If the file cannot be both read and written to
' UNKNOWN '	If the processor cannot determine whether the file can be both read and written to

The RECL specifier asks the maximum record length for a file. It takes the following form:

RECL = rcl

rcl

Is a scalar integer variable that is assigned a value as follows:

• If the file or unit is connected, the value assigned is the maximum record length allowed.
• If the file is not connected, the value assigned is the maximum record length allowed in the file. However, if the maximum record length is zero, the value assigned is the length of the longest record in the file.
  If inquiring about a file that has no maximum record size, see Section 12.6.25.
• If the file is segmented, the value assigned is the longest segment length in the file.
• If the file does not exist, the value assigned is zero.

The assigned value is expressed in 4-byte units if a file is currently (or was previously) connected for unformatted data transfer; otherwise, the value is expressed in bytes.

12.5.25 RECORDTYPE Specifier

The SEQUENTIAL specifier asks whether a file is connected for sequential access. It takes the following form:

SEQUENTIAL = seq

seq

Is a scalar default character variable that is assigned one of the following values:

' YES '	If the file is connected for sequential access
' NO '	If the file is not connected for sequential access
' UNKNOWN '	If the processor cannot determine whether the file is connected for sequential access

The UNFORMATTED specifier asks whether a file is connected for unformatted data transfer. It takes the following form:

UNFORMATTED = unf

unf

Is a scalar default character variable that is assigned one of the following values:

' YES '	If the file is connected for unformatted data transfer
' NO '	If the file is not connected for unformatted data transfer
' UNKNOWN '	If the processor cannot determine whether the file is connected for unformatted data transfer

The WRITE specifier asks whether a file can be written to. It takes the following form:

WRITE = wr

wr

Is a scalar default character variable that is assigned one of the following values:

' YES '	If the file can be written to
' NO '	If the file cannot be written to
' UNKNOWN '	If the processor cannot determine whether the file can be written to

The OPEN statement connects an external file to a unit, creates a new file and connects it to a unit, creates a preconnected file, or changes certain properties of a connection.

The OPEN statement takes the following form:

OPEN ([UNIT=]io-unit [,FILE=name] [,ERR=label] [,IOSTAT=i-var], slist)

io-unit

Is an external unit specifier.

name

Is a character or numeric expression specifying the name of the file to be connected. For more information, see Section 12.6.14.

label

Is the label of the branch target statement that receives control if an error occurs.

i-var

Is a scalar integer variable that is defined as a positive integer if an error occurs and zero if no error occurs.

slist

Is one or more OPEN specifiers in the form specifier=value or specifier. Each specifier can appear only once.

The OPEN specifiers and their acceptable values are summarized in Table 12-1.

The OPEN specifiers are described individually in the following sections. The control specifiers that can be specified in an OPEN statement (UNIT, ERR, and IOSTAT) are discussed in Section 10.2.1.

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Table 12-1 OPEN Statement Specifiers and Values

Specifier	Values	Function	Default
ACCESS	' SEQUENTIAL ' ' DIRECT ' ' KEYED ' ' APPEND '	Access mode	' SEQUENTIAL '
ACTION	' READ ' ' WRITE ' ' READWRITE '	File access	' READWRITE '
ASSOCIATEVARIABLE	var	Next direct access record	No default
BLANK	' NULL ' ' ZERO '	Interpretation of blanks	' NULL '
BLOCKSIZE	n_expr	Physical block size	System default
BUFFERCOUNT	n_expr	Number of I/O buffers	System default
BUFFERED	' YES ' ' NO '	Buffering for WRITE operations	' NO '
CARRIAGECONTROL	' FORTRAN ' ' LIST ' ' NONE '	Print control	Formatted: ' FORTRAN ' Unformatted: ' NONE '
CONVERT	' LITTLE_ENDIAN ' ' BIG_ENDIAN ' ' CRAY ' ' FDX ' ' FGX ' ' IBM ' ' VAXD ' ' VAXG ' ' NATIVE '	Numeric format specification	' NATIVE '
DEFAULTFILE	c_expr	Default file specification	Current working directory
DELIM	' APOSTROPHE ' ' QUOTE ' ' NONE '	Delimiter for character constants	' NONE '
DISPOSE (or DISP)	' KEEP ' or ' SAVE ' ' DELETE ' ' PRINT ' ' PRINT/DELETE ' ' SUBMIT ' ' SUBMIT/DELETE '	File disposition at close	' KEEP '
ERR	label	Error transfer control	No default
EXTENDSIZE	n_expr	File allocation increment	Volume or system default
FILE (or NAME)	c_expr	File specification (file name)	FORnnn.DAT 1
FORM	' FORMATTED ' ' UNFORMATTED '	Format type	Depends on ACCESS setting
INITIALSIZE	n_expr	File allocation	No default
IOSTAT	var	I/O status	No default
KEY	(e1:e2[:dt[:dr]],...)	Key field definitions	CHARACTER ASCENDING
MAXREC	n_expr	Direct access record limit	No limit
NOSPANBLOCKS	No value	Records do not span blocks	No default
ORGANIZATION	' SEQUENTIAL ' ' RELATIVE ' ' INDEXED '	File organization	' SEQUENTIAL '
PAD	' YES ' ' NO '	Record padding	' YES '
POSITION	' ASIS ' ' REWIND ' ' APPEND '	File positioning	' ASIS '
READONLY	No value	Write protection	No default
RECL (or RECORDSIZE)	n_expr	Record length	Depends on RECORDTYPE, ORGANIZATION, and FORM settings
RECORDTYPE	' FIXED ' ' VARIABLE ' ' SEGMENTED ' ' STREAM ' ' STREAM_CR ' ' STREAM_LF '	Record type	Depends on ORGANIZATION, ACCESS, and FORM settings
SHARED	No value	File sharing allowed	No default 2
STATUS (or TYPE)	' OLD ' ' NEW ' ' SCRATCH ' ' REPLACE ' ' UNKNOWN '	File status at open	' UNKNOWN ' 3
UNIT	n_expr	Logical unit number	No default; an io-unit must be specified
USEROPEN	func	User program option	No default

c _expr: A scalar default character expression
dr: A direction, ASCENDING or DESCENDING
dt: A data type, INTEGER or CHARACTER
e1: The first byte position of a key
e2: The last byte position of a key
func: An external function
label: A statement label
n _expr: A scalar numeric expression
var: A scalar integer variable

Rules and Behavior

The control specifiers ([UNIT=]io-unit, ERR=label, and IOSTAT=i-var) and OPEN specifiers can appear anywhere within the parentheses following OPEN. However, if the UNIT specifier is omitted, the io-unit must appear first in the list.

Specifier values that are scalar numeric expressions can be any integer or real expression. The value of the expression is converted to integer data type before it is used in the OPEN statement.

Only one unit at a time can be connected to a file, but multiple OPENs can be performed on the same unit. If an OPEN statement is executed for a unit that already exists, the following occurs:

• If FILE is not specified, or FILE specifies the same file name that appeared in a previous OPEN statement, the current file remains connected.
  If the file names are the same, the values for the BLANK, CONVERT, CARRIAGECONTROL, DELIM, DISPOSE, ERR, IOSTAT, and PAD specifiers can be changed. Other OPEN specifier values cannot be changed, and the file position is unaffected.
• If FILE specifies a different file name, the previous file is closed and the new file is connected to the unit.