TOPS-20 PASCAL Language Manual - Bitsavers

INPUT AND OUTPUT
You must call REWRITE before writing any file except the predeclared
file OUTPUT. If you call REWRITE for the predeclared file INPUT or
OUTPUT, a run-time error occurs.
The REWRITE procedure sets the file to length zero and sets EOF to
TRUE. You can then write new components into the file with the PUT,
WRITE, or WRITELN procedure (WRITELN is defined only for text files).
After the file is open, successive calls to REWRITE close and
supersede the existing file; that is, they create new versions of the
file.
To update an existing file, you must
file, specifying new values for
upda te.
copy its contents to another
the components that you need to
Example I
BEGIN
REWRITE (Storffis)~
END;
If the file variable Storms is already open, this statement enables
writing and sets the file position to the beginning of the file. If
Storms is not open, a new version is created with the same defaults as
for the OPEN procedure.
Example 2
BEGIN
OPEN (f~t:'sult~;" 'F'~:;:ISSUES+DAT' , OLD" ,FIXED);
REWRITE (Hesults),
END,
The OPEN procedure sets defaults for the file variable Results, which
is associated with the file ISSUES.DAT in directory PS:. The
REWRITE procedure discards the current contents of the file Results
and sets the file position at the beginning of the file. After
execution of this statement, EOF(Results) is TRUE.
7.14 THE WRITE PROCEDURE
The WRITE procedure writes data into a file.
Fo rma t
WRITE [ file variable,] print list);
7-21