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SYSTEM
DESCRIPTION
24.2 -- File Structure
F
F
The
following
diagrams
illustrate
the
format
of
a
segment descriptor word and the
te~minator.
SEGMENT DESCRIPTOR WORD
E
D
c
B
A
9
8
7
6
5
4
3
2
1
o
(------- Starting cluster number
------>
Number of contiguous clusters
1
Zero (Non-terminator bit)
TERMINATOR
E
D
c
B
A
9
8
7
6
5
4
3
2
1
o
: <-------
Logical,sector number of logical end-of-file
----->
•
One (Terminator bit)
The
SDW
terminator
is
used
to
monitor
the logical
end-or-file.
It contains the logical sector
number
of
the
end-or-file.
The
sector
which is the end of a rile may be
partially filled
with
null
characters.
Thus,
no
actual
end-or-file record will be found
~ithin
a
file.
This feature
allows files to be merged
together
without
having
to
read
through
the
entire file looking
rOT
an end-or-file record.
The
actual
format
of
a
RIB
is shown in the following
diagram.
For non-memory-image filesl
the bytes following the
terminator
must
all
be
zero.
Only memory-image files can
have non-zero bytes following the terminator,
and then
those
bytes must meet the six criteria listed above.
Page
24-09
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