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DUMP COMMAND
11. 1 -- Use
enough
to
accommodate one sector from diskette.
The sector
change buffer can be used in either mode
or
operation.
The
contents
of
the sector change buffer will not be destroyed or
altered unless the operator issues a command to do so.
Associated with the sector change buffer
is
a
"sector
address validity flag
ll
•
This flag indicates whether or not
a
critical command
has
been
executed
between
the
time
the
sector
change
burfer
wa~
read
into and the time that the
sector change buffer is written back to diskette.
When
the
sector
change
buffe~
is
read
into,
a
sector address is
specified.
This
address is retained so that if the sector is
to
be
written
back
to
diskette~
the address need not be
speciried again;
however,
certain
actions,
described
under
the
separat'e c emmand d escr
i p
t
i
ens that fo
11
ow,
can cause th e
sec tor
add
res s to
b
e i nv
ali
d ate d .
Th
en
I
the wr
i
tin
9
0
f
the
sector
change
buffer
requi~es
a
respecification
o~
the
sector'address into which the buffer is to be WTitten.
The sector change buffer is
very
useful
in
modifying
sectors.
Most
-FrettuentlYI
the sector change buf-Fer is used
in conjunction with "the
REPAIR
command (Chapter
22)
to
Tix
critical
system
tables
which have been round in error.
Or
course,
this procedure is not recommended unless the operator
has
detailed
knowledge
of
the
system
table
structure.
Situations
do
arise when critical file information
can
only
bel" e c
0
v ere
d
t
h
r
0
ugh
the
ma n
u a 1 .
r e con s t r u c t ion
0
f c
e
r t a
i n
system tables.
1he
DUMP
command's
s~ctor
change
buffer
p~ovides
the ideal means for doing this.
11.2 DUMP Command Set
Each
command
to
DUMP
must be entered
by
the operator
after the
input
prompt'" (:)
is
displayed
on
the
system
console.
Like
all
MDOS
input,
all
DUMP
commands must
be
terminated by a carriage return.
In
the
following
command
desc~iptions
these symbols are used:
Symbol
Meaning
m,
n
Bot
h
II
In "
and
II
n
II
a r,e on e to
f
0
u
r dig
i
t
hexadecimal
numbe~s
used for specifying a
sector number or a cluster number,
i
b
"in
is
a
one
digit
number
used
for
referring to the logical unit number.
"b" is
a
one
or
two
digit
hexadecimal
number
used as an offset into the sector
change buffer.
Page
11-03
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