<s>
In	O
computing	O
,	O
a	O
rigid	B-Application
disk	I-Application
block	I-Application
(	O
RDB	O
)	O
is	O
the	O
block	O
on	O
a	O
hard	B-Device
disk	I-Device
where	O
the	O
Amiga	B-Device
series	O
of	O
computers	O
store	O
the	O
disk	O
's	O
partition	O
and	O
filesystem	O
information	O
.	O
</s>
<s>
The	O
IBM	B-Device
's	I-Device
PC	I-Device
equivalent	O
of	O
the	O
Amiga	B-Device
's	O
RDB	O
is	O
the	O
master	B-Device
boot	I-Device
record	I-Device
(	O
MBR	O
)	O
.	O
</s>
<s>
Instead	O
it	O
points	O
to	O
a	O
linked	B-Data_Structure
list	I-Data_Structure
of	O
partition	O
blocks	O
,	O
which	O
contain	O
the	O
actual	O
partition	O
data	O
.	O
</s>
<s>
Additionally	O
,	O
it	O
may	O
point	O
to	O
additional	O
filesystem	O
drivers	O
,	O
allowing	O
the	O
Amiga	B-Device
to	O
boot	O
from	O
filesystems	O
not	O
directly	O
supported	O
by	O
the	O
ROM	O
,	O
such	O
as	O
PFS	B-Application
or	O
SFS	B-Application
.	O
</s>
<s>
The	O
data	O
in	O
the	O
rigid	B-Application
disk	I-Application
block	I-Application
must	O
start	O
with	O
the	O
ASCII	B-Protocol
bytes	O
"	O
RDSK	B-Application
"	O
.	O
</s>
<s>
Thus	O
it	O
could	O
safely	O
coexist	O
with	O
a	O
master	B-Device
boot	I-Device
record	I-Device
,	O
which	O
is	O
forced	O
to	O
be	O
found	O
at	O
block	O
0	O
.	O
</s>
<s>
Nearly	O
all	O
Amiga	B-Device
hard	B-Device
disk	I-Device
controllers	O
support	O
the	O
RDB	O
standard	O
,	O
enabling	O
the	O
user	O
to	O
exchange	O
disks	O
between	O
controllers	O
.	O
</s>
