<s>
There	O
are	O
three	O
different	O
addressing	B-General_Concept
schemes	I-General_Concept
for	O
display	B-Device
devices	I-Device
:	O
direct	O
,	O
matrix	B-Architecture
,	O
and	O
raster	O
.	O
</s>
<s>
The	O
purpose	O
of	O
each	O
scheme	O
is	O
to	O
set	O
(	O
or	O
maintain	O
)	O
the	O
state	O
of	O
a	O
pixel	B-Algorithm
to	O
either	O
black/white	O
or	O
,	O
more	O
commonly	O
,	O
a	O
grayscale	O
level	O
.	O
</s>
<s>
A	O
direct	O
addressed	O
display	O
runs	O
individual	O
control	O
signals	O
to	O
each	O
pixel	B-Algorithm
.	O
</s>
<s>
This	O
allows	O
the	O
state	O
,	O
whether	O
on/off	O
or	O
grayscale	O
,	O
to	O
be	O
set	O
and	O
maintained	O
on	O
each	O
pixel	B-Algorithm
.	O
</s>
<s>
For	O
a	O
screen	O
size	O
of	O
m×n	O
pixels	B-Algorithm
,	O
this	O
scheme	O
would	O
require	O
m×n	O
control	O
signals	O
.	O
</s>
<s>
A	O
matrix	B-Architecture
addressed	O
display	O
runs	O
control	O
signals	O
only	O
to	O
the	O
rows	O
and	O
columns	O
of	O
the	O
display	O
.	O
</s>
<s>
(	O
See	O
also	O
:	O
matrix	B-Architecture
)	O
For	O
a	O
screen	O
size	O
of	O
m×n	O
pixels	B-Algorithm
,	O
this	O
scheme	O
would	O
require	O
m+n	O
control	O
signals	O
.	O
</s>
<s>
In	O
active	B-General_Concept
matrix	I-General_Concept
addressing	I-General_Concept
,	O
some	O
sort	O
of	O
capacitor	O
(	O
external	O
to	O
the	O
cell	O
proper	O
)	O
is	O
used	O
to	O
maintain	O
the	O
state	O
of	O
the	O
cell	O
.	O
</s>
<s>
Passive	B-Device
matrix	I-Device
addressing	I-Device
is	O
used	O
when	O
cell	O
itself	O
has	O
a	O
bistability	O
,	O
so	O
no	O
external	O
capacitor	O
is	O
needed	O
.	O
</s>
<s>
In	O
some	O
situations	O
passive	B-Device
matrix	I-Device
addressing	I-Device
is	O
used	O
with	O
the	O
help	O
of	O
persistence	O
of	O
vision	O
of	O
the	O
(	O
usually	O
human	O
)	O
eye	O
so	O
the	O
cell	O
need	O
not	O
be	O
bistable	O
.	O
</s>
<s>
A	O
raster	O
addressed	O
display	O
(	O
e.g.	O
,	O
a	O
CRT	B-Device
)	O
works	O
by	O
scanning	O
across	O
the	O
entire	O
display	O
in	O
sequence	O
while	O
modulating	O
control	O
signal	O
to	O
activate	O
each	O
pixel	B-Algorithm
as	O
it	O
is	O
scanned	O
.	O
</s>
<s>
This	O
display	O
uses	O
persistence	O
of	O
the	O
pixel	B-Algorithm
element	O
(	O
e.g.	O
,	O
phosphor	O
)	O
to	O
maintain	O
the	O
pixel	B-Algorithm
state	O
until	O
the	O
scan	O
can	O
visit	O
that	O
pixel	B-Algorithm
again	O
.	O
</s>
