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This
function
is
called
once
at
the beginning
of formatting.
It
specifies the location
of
a
sector
buffer
for
use
in
transferring
a
boot sector
to
the
newly
formatted
disk.
The
data placed
into
this
sector
buffer
will
be
provided
in
the
Format
Disk
function
call
for
placement on
the
formatted
disk.
The
parameter
string
specified
in
ES:DI
is
a zero terminated
ASCII
character
string.
It
is
specified
by
the user
from
within
the
FORMAT
application
program.
The
actual
contents
of
this
string
is
OEM
specified,
and
may
have any meaning
desired. Microsoft
does
not
make
use
of
this
string
in
any
way.
The
BIOS-ROM
allows the
foflowing
two parameters:
V
=
verify
option:
Verify
formatted
disk.
The
formatting
takes longer
with the
verify
option,
however,
it
gives higher
reliability.
B =
Copy
boot sector
option:
Usually only the
BPB
table
is
copied
into
the boot sector
of
a
formatted
disk,
however,
all
data
of
the
boot sector
is
copied
if
this
option
is
specified.
Change
disk flag:0FFh
is
returned
if
this
option
is
specified.
The change
disk
flag
on
exit
specifies
whether
to
prompt
the user
to
place a
new
disk
in
the
drive
before
formatting
is
begun.
If
this flag
is
set
on
return
from
the
function,
the
user
will
be
prompted
to
change
the disk before function
7
is
called.
The
scratch
buffer specified
in
DS:SI
will
be a
sector sized block
of
memory
which
may
be
used
in
any
way.
The
size
of
this
block
is
determined from
the
BPB
array returned
via
Function
1
(Initialize
Disk Device)
and
will
be
the
same
size
as the
largest
sector
size
in
the
BPB
array.
This sector
may
be used
in
any
way
desired.
INT
57h,
Function 7
-
Format
Disk
Entry:
AH
= 7
(function
code)
AL =
drive
number
(starting
with
0)
DS:SI
=
Boot
sector
buffer
ES:DI
- Format
table buffer
Exit:
AL
=
Standard
BIOS
error
code
BX
= Bad
sector
number
CX
= Number
of
consecutive
bad
sectors
This
routine
is
called
to
format the
disk.
If
a bad
sector or
group
of
bad
sectors
is
encountered,
this
function
should
return
with the
bad
sector
number and
the
count
of
consecutive
bad
sectors.
This information
is
used
in
building
a
list
of
bad
sectors
in
the FAT.
This
function
will
be
called
repeatedly
until
a
final
return
occurs
in
which
CX
=
(no
bad
sectors)
is
reported.
At
that time,
it
is
assumed
that
the
entire
disk
has been
formatted.
The
scratch sector
buffer
passed
in
DS:SI
is
the
same
buffer
as
was
passed
in
Function
6
(Initialize
for
Disk Formatting).
161
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