<s>
In	O
computing	O
,	O
a	O
logical	B-General_Concept
address	I-General_Concept
is	O
the	O
address	O
at	O
which	O
an	O
item	O
(	O
memory	B-General_Concept
cell	I-General_Concept
,	O
storage	O
element	O
,	O
network	O
host	O
)	O
appears	O
to	O
reside	O
from	O
the	O
perspective	O
of	O
an	O
executing	O
application	B-Application
program	I-Application
.	O
</s>
<s>
A	O
logical	B-General_Concept
address	I-General_Concept
may	O
be	O
different	O
from	O
the	O
physical	B-General_Concept
address	I-General_Concept
due	O
to	O
the	O
operation	O
of	O
an	O
address	O
translator	O
or	O
mapping	O
function	O
.	O
</s>
<s>
Such	O
mapping	O
functions	O
may	O
be	O
,	O
in	O
the	O
case	O
of	O
a	O
computer	O
memory	O
architecture	O
,	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
(	O
MMU	O
)	O
between	O
the	O
CPU	B-Device
and	O
the	O
memory	O
bus	O
.	O
</s>
<s>
The	O
physical	B-General_Concept
address	I-General_Concept
of	O
computer	O
memory	O
banks	O
may	O
be	O
mapped	O
to	O
different	O
logical	O
addresses	O
for	O
various	O
purposes	O
.	O
</s>
<s>
In	O
a	O
system	O
supporting	O
virtual	B-Architecture
memory	I-Architecture
,	O
there	O
may	O
actually	O
not	O
be	O
any	O
physical	O
memory	O
mapped	O
to	O
a	O
logical	B-General_Concept
address	I-General_Concept
until	O
an	O
access	O
is	O
attempted	O
.	O
</s>
<s>
The	O
access	O
triggers	O
special	O
functions	O
of	O
the	O
operating	O
system	O
which	O
reprogram	O
the	O
MMU	O
to	O
map	O
the	O
address	O
to	O
some	O
physical	O
memory	O
,	O
perhaps	O
writing	O
the	O
old	O
contents	O
of	O
that	O
memory	O
to	O
disk	O
and	O
reading	O
back	O
from	O
disk	O
what	O
the	O
memory	O
should	O
contain	O
at	O
the	O
new	O
logical	B-General_Concept
address	I-General_Concept
.	O
</s>
<s>
In	O
this	O
case	O
,	O
the	O
logical	B-General_Concept
address	I-General_Concept
may	O
be	O
referred	O
to	O
as	O
a	O
virtual	B-General_Concept
address	I-General_Concept
.	O
</s>
