TOPS-20 PASCAL Language Manual - Bitsavers

INPUT AND OUTPUT
7.7 THE OPEN PROCEDURE
The OPEN procedure does not actually open a file but rather allows you
to specify file attributes. You cannot use OPEN on a file th~t has
had a RESET or REWRITE done, or on the predeclared file INPUT.
Fo rma t 1
Format 2
OPEN (file variable [ ,file name E [,history E
IT ,record length E [,record-access-method E
[ ,record type E [,carriage control E );
OPEN
(FILE VARIABLE := file variable
[ ,FILE NAME := file name E
[ ,HISTORY := history status E
[ ,RECORD LENGTH := positive integer E
[ ,RECORD-ACCESS METHOD := record-access-mode E
[ ,RECORD-TYPE :~ record type E
[ CARRIAGE CONTROL .= carriage control D );
where:
file variabJe
specifies the PASCAL file variable associated
with the file. You cannot open the
predeclared file variable INPUT.
(internal files)
This parameter is ignored for internal files.
The system creates a unique name for each
internal file.
(external files)
file name
provides information about the file to
TOPS-20. The file name can be a variable or
constant identifier defined as type PACKED
ARRAY (l .• n] OF CHAR, or a file specification
enclosed in apostrophes (for example,
'PS:(MASELLA)BOOKS.DAT') .
If you omit the file name, PASCAL will first
attempt to use the file variable identifier
as a logical name. If that name is not
defined, PASCAL will use the defaults shown
in Table 7-1.
The file variable and the file name parameters designate the file to
be opened. The remaining parameters specify attributes for the file
and are summarized in Table 7-2, in Section 7.7.5. Except for the
file variable name, all parameters are optional. Any parameters you
specify, however, must be in the order shown above unless you use
keywo rd syn tax.
You can specify either the value of the parameter or the keyword and
the value of the parameter. You can also use a combination.
7-8