Control Data Corporation 3300 Reference Manual page 132

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• Standard ending reel label procedure and user's ending reel label
procedure, if specified, by the USE statement. The order of
execution is specified by the USE statement.
• Tape swap.
• Standard beginning reel label procedure and user's beginning reel
label procedure, if specified. The order of execution is specified
by the USE statement.
• First data record on the new reel is made available.
Format 2:
The READ statement implicitly performs the functions of a SEEK statement
for a specific mass storage file, unless a SEEK statement for the file is
executed prior
to
the READ. Records in the file are read in accordance with
the contents of the ACTUAL KEY data item. The user is responsible for
setting the contents of this data item prior to execution of the READ statement
(ACTUAL KEY, chapter 2). If an attempt is made to read a mass storage
record and contents of the associated ACTUAL KEY data item are outside the
allocated file area, the INVALID KEY phrase is executed. The allocated area
of a file is the number of blocks assigned to it by the ALLOCATE request of
the MASTER *DEF function (section 7. 3. 3) .
Regardless of the method used to overlap access time with processing time,
the concept of the READ statement is unchanged in that a record is available
prior to the execution of any statement following the READ statement.
Examples:
READ MASTER-FILE AT END MOVE 1 TO MASTER-ENDED-IND
GO TO END-MASTER.
READ DETAIL-FILE AT END GO TO END-DETAIL.
READ INVENT-FILE AT END ADD 1 TO INVENT-IND GO TO END-
INVENT.
READ DATA-FILE INTO ITEM-l INVALID KEY DISPLAY "END DATA".
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