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Boot Sector Format
B.P.B.
Optional
B.P.B.
3-bytes
JUMP
Code
to
BOOTER
8-bytes
OEM
name
and
version
"Tandy 600"
W:
Bytes per
Sector:
512
B:
Sectors per
allocation
unit:
W:
Reserved
Sectors:
B;
Number
of
FATs:
W: Number
of root
DIR
entries:
112
W:
Total
number
of
Sectors
includes reserved sectors
720
B:
Media
descriptor:
W
W
W
W
Number
of
Sectors per
FAT
F8 hex
2
Sectors per
Track:
Number
of
Head:
Number
of
hidden
Sectors:
BOOTER CODE
If
the
JUMP
instruction
is
not
on
here,
the
BIOS assumes
that
this
is
not
its
original diskette.
INT
57h,
Function 9
-
Deactivate Disk
Device
Entry:
Exit:
AH
=
9
(function
code)
AL
=
Standard
BIOS
error
code
The Tandy 600
supports only
one
MS-
DOS
standard
disk format.
Another
MS-
DOS
machine can
read/write
to
this
diskette
because
it
has
BPB
on
the boot
sector.
If
there are
two
NOP
(90 hex)
codes
instead
of
BOOTER
code
here, the
BIOS
assumes
that
this
diskette
is
not
an
uncooperative
system
diskette.
This
function
is
called
once
after
access
to
the disk device
is
completed.
It
should perform
any
clean
up necessary
before the
disk
device
is
released.
163
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