<s>
In	O
computing	O
,	O
an	O
address	B-General_Concept
space	I-General_Concept
defines	O
a	O
range	O
of	O
discrete	O
addresses	O
,	O
each	O
of	O
which	O
may	O
correspond	O
to	O
a	O
network	B-Device
host	I-Device
,	O
peripheral	B-Device
device	I-Device
,	O
disk	B-Application
sector	I-Application
,	O
a	O
memory	B-General_Concept
cell	O
or	O
other	O
logical	O
or	O
physical	O
entity	O
.	O
</s>
<s>
For	O
software	B-Application
programs	I-Application
to	O
save	O
and	O
retrieve	O
stored	O
data	O
,	O
each	O
datum	O
must	O
have	O
an	O
address	O
where	O
it	O
can	O
be	O
located	O
.	O
</s>
<s>
The	O
number	O
of	O
address	B-General_Concept
spaces	I-General_Concept
available	O
depends	O
on	O
the	O
underlying	O
address	O
structure	O
,	O
which	O
is	O
usually	O
limited	O
by	O
the	O
computer	B-General_Concept
architecture	I-General_Concept
being	O
used	O
.	O
</s>
<s>
Often	O
an	O
address	B-General_Concept
space	I-General_Concept
in	O
a	O
system	O
with	O
virtual	B-Architecture
memory	I-Architecture
corresponds	O
to	O
a	O
highest	O
level	O
translation	O
table	O
,	O
e.g.	O
,	O
a	O
segment	B-General_Concept
table	I-General_Concept
in	O
IBM	B-Device
System/370	I-Device
.	O
</s>
<s>
Address	B-General_Concept
spaces	I-General_Concept
are	O
created	O
by	O
combining	O
enough	O
uniquely	O
identified	O
qualifiers	O
to	O
make	O
an	O
address	O
unambiguous	O
within	O
the	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
For	O
a	O
person	O
's	O
physical	B-General_Concept
address	I-General_Concept
,	O
the	O
address	B-General_Concept
space	I-General_Concept
would	O
be	O
a	O
combination	O
of	O
locations	O
,	O
such	O
as	O
a	O
neighborhood	O
,	O
town	O
,	O
city	O
,	O
or	O
country	O
.	O
</s>
<s>
Some	O
elements	O
of	O
a	O
data	O
address	B-General_Concept
space	I-General_Concept
may	O
be	O
the	O
same	O
,	O
but	O
if	O
any	O
element	O
in	O
the	O
address	O
is	O
different	O
,	O
addresses	O
in	O
said	O
space	O
will	O
reference	O
different	O
entities	O
.	O
</s>
<s>
For	O
example	O
,	O
there	O
could	O
be	O
multiple	O
buildings	O
at	O
the	O
same	O
address	O
of	O
"	O
32	O
Main	O
Street	O
"	O
but	O
in	O
different	O
towns	O
,	O
demonstrating	O
that	O
different	O
towns	O
have	O
different	O
,	O
although	O
similarly	O
arranged	O
,	O
street	O
address	B-General_Concept
spaces	I-General_Concept
.	O
</s>
<s>
An	O
address	B-General_Concept
space	I-General_Concept
usually	O
provides	O
(	O
or	O
allows	O
)	O
a	O
partitioning	O
to	O
several	O
regions	O
according	O
to	O
the	O
mathematical	O
structure	O
it	O
has	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
total	O
order	O
,	O
as	O
for	O
memory	B-General_Concept
addresses	O
,	O
these	O
are	O
simply	O
chunks	O
.	O
</s>
<s>
Like	O
the	O
hierarchical	O
design	O
of	O
postal	O
addresses	O
,	O
some	O
nested	O
domain	O
hierarchies	O
appear	O
as	O
a	O
directed	O
ordered	O
tree	O
,	O
such	O
as	O
with	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
or	O
a	O
directory	B-Architecture
structure	I-Architecture
.	O
</s>
<s>
In	O
the	O
Internet	O
,	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
allocates	O
ranges	O
of	O
IP	B-Protocol
addresses	I-Protocol
to	O
various	O
registries	O
so	O
each	O
can	O
manage	O
their	O
parts	O
of	O
the	O
global	O
Internet	B-Protocol
address	I-Protocol
space	O
.	O
</s>
<s>
Memory	B-General_Concept
addresses	O
for	O
main	O
memory	B-General_Concept
,	O
memory-mapped	B-Architecture
I/O	I-Architecture
,	O
as	O
well	O
as	O
for	O
virtual	B-Architecture
memory	I-Architecture
;	O
</s>
<s>
Device	O
addresses	O
on	O
an	O
expansion	B-Device
bus	I-Device
;	O
</s>
<s>
Sector	B-Device
addressing	O
for	O
disk	B-Device
drives	I-Device
;	O
</s>
<s>
File	O
names	O
on	O
a	O
particular	O
volume	B-Application
;	O
</s>
<s>
Various	O
kinds	O
of	O
network	B-Device
host	I-Device
addresses	O
in	O
computer	B-Architecture
networks	I-Architecture
;	O
</s>
<s>
Another	O
common	O
feature	O
of	O
address	B-General_Concept
spaces	I-General_Concept
are	O
mappings	B-Algorithm
and	I-Algorithm
translations	I-Algorithm
,	O
often	O
forming	O
numerous	O
layers	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
file	B-Application
system	I-Application
on	O
a	O
logical	B-General_Concept
disk	I-General_Concept
operates	O
using	O
linear	O
sector	B-Device
numbers	O
,	O
which	O
have	O
to	O
be	O
translated	O
to	O
absolute	O
LBA	B-Device
sector	B-Device
addresses	O
,	O
in	O
simple	O
cases	O
,	O
via	O
addition	O
of	O
the	O
partition	O
's	O
first	O
sector	B-Device
address	O
.	O
</s>
<s>
Then	O
,	O
for	O
a	O
disk	B-Device
drive	I-Device
connected	O
via	O
Parallel	B-Protocol
ATA	I-Protocol
,	O
each	O
of	O
them	O
must	O
be	O
converted	O
to	O
logical	O
cylinder-head-sector	B-Device
address	O
due	O
to	O
the	O
interface	O
historical	O
shortcomings	O
.	O
</s>
<s>
It	O
is	O
converted	O
back	O
to	O
LBA	B-Device
by	O
the	O
disk	B-General_Concept
controller	I-General_Concept
,	O
then	O
,	O
finally	O
,	O
to	O
physical	O
cylinder	O
,	O
head	B-Device
and	O
sector	B-Device
numbers	O
.	O
</s>
<s>
The	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
maps	O
its	O
names	O
to	O
and	O
from	O
network-specific	O
addresses	O
(	O
usually	O
IP	B-Protocol
addresses	I-Protocol
)	O
,	O
which	O
in	O
turn	O
may	O
be	O
mapped	O
to	O
link	B-Protocol
layer	I-Protocol
network	O
addresses	O
via	O
Address	O
Resolution	O
Protocol	O
.	O
</s>
<s>
Network	B-Protocol
address	I-Protocol
translation	I-Protocol
may	O
also	O
occur	O
on	O
the	O
edge	O
of	O
different	O
IP	O
spaces	O
,	O
such	O
as	O
a	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
and	O
the	O
Internet	O
.	O
</s>
<s>
An	O
iconic	O
example	O
of	O
virtual-to-physical	O
address	O
translation	O
is	O
virtual	B-Architecture
memory	I-Architecture
,	O
where	O
different	O
pages	B-General_Concept
of	O
virtual	B-General_Concept
address	I-General_Concept
space	I-General_Concept
map	O
either	O
to	O
page	B-Architecture
file	I-Architecture
or	O
to	O
main	O
memory	B-General_Concept
physical	B-General_Concept
address	I-General_Concept
space	O
.	O
</s>
<s>
It	O
is	O
possible	O
that	O
several	O
numerically	O
different	O
virtual	O
addresses	O
all	O
refer	O
to	O
one	O
physical	B-General_Concept
address	I-General_Concept
and	O
hence	O
to	O
the	O
same	O
physical	O
byte	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
that	O
a	O
single	O
virtual	B-General_Concept
address	I-General_Concept
maps	O
to	O
zero	O
,	O
one	O
,	O
or	O
more	O
than	O
one	O
physical	B-General_Concept
address	I-General_Concept
.	O
</s>
