TOPS-20 PASCAL Language Manual - Bitsavers

INPUT AND OUTPUT
where:
file variable
integer expression
specifies a file that is open for direct
access. The file must have fixed-length
records.
specifies the positive integer
expression indicating the component at
which to position the file. The
component number must not be less than
or equal to zero.
The FIND procedure allows you to directly access the components of a
file. You can use the FIND procedure to move forward or backward in a
file. The file must be open for direct access. That is, you must
have specified DIRECT in the OPEN statement for that file. In
addition, the file must have fixed-length records.
After execution of the FIND procedure, the file is positioned at the
specified component. The file buffer variable assumes the value of
the component, for example:
FIN D (A 1 b 1.1 III S, 4) ~
As the result of this statement, the file position moves to the fourth
component in the file Albums. The file buffer variable Albumsassumes
the value of the fourth component.
If you specify a component beyond the end of the file, no error
occurs.
You can use the FIND procedure only when reading a file. If the file
is open for output (that is, with REWRITE), a call to FIND results in
a run-time error.
Example I
BEGIN
FIND (Albums, Current + 2);
END;
If the value of Current is 6, this statement causes the file position
to move to the eighth component. The file buffer variable Albumsassumes
the value of the component.
Example 2
BEGIN
FIN D (A 1 b U IT! S, C U l'r e n t .. -1 ) ;
END~
If the value of Current is 6, this statement causes the file position
to move backward one component to the fifth component.
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