Xerox 701P21091 - Manual (Page 210)

Using logical processing
3-30 Using LCDS Print Description Language
The contents of the first byte of each tape block (offset=0,
length=1) is examined for the character constant 'P'. When a 'P'
is detected, the entire block is selected (BSELECT) for printing.
When the first byte of any block does not contain a 'P', that block
is bypassed and not printed. In this example, only block 1 is
printed.
The following figure shows a sample of how BSELECT and
BDELETE commands are used.
Figure 3-2. Sample BSELECT and BDELETE command
usage
Example 2
The following example shows a BDELETE command that will
delete from the tape any blocks that contain $$11:
T1: TABLE CONSTANT=('$$11');
C1: CRITERIA CONSTANT=(4,4,EQ,T1);
BDELETE TEST=C1;