<s>
Reading	O
is	O
an	O
action	O
performed	O
by	O
computers	O
,	O
to	O
acquire	O
data	O
from	O
a	O
source	O
and	O
place	O
it	O
into	O
their	O
volatile	B-General_Concept
memory	I-General_Concept
for	O
processing	B-Operating_System
.	O
</s>
<s>
Computers	O
may	O
read	O
information	O
from	O
a	O
variety	O
of	O
sources	O
,	O
such	O
as	O
magnetic	B-Architecture
storage	I-Architecture
,	O
the	O
Internet	O
,	O
or	O
audio	O
and	O
video	O
input	O
ports	B-Protocol
.	O
</s>
<s>
Reading	O
is	O
one	O
of	O
the	O
core	O
functions	O
of	O
a	O
Turing	B-Architecture
machine	I-Architecture
.	O
</s>
<s>
A	O
read	B-General_Concept
cycle	I-General_Concept
is	O
the	O
act	O
of	O
reading	O
one	O
unit	O
of	O
information	O
(	O
e.g.	O
</s>
<s>
A	O
read	B-General_Concept
channel	I-General_Concept
is	O
an	O
electrical	O
circuit	O
that	O
transforms	O
the	O
physical	O
magnetic	O
flux	O
changes	O
into	O
abstract	O
bits	O
.	O
</s>
<s>
A	O
read	B-General_Concept
error	I-General_Concept
occurs	O
when	O
the	O
physical	O
part	O
of	O
the	O
process	O
fails	O
for	O
some	O
reason	O
,	O
such	O
as	O
dust	O
or	O
dirt	O
entering	O
the	O
drive	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
computer	O
may	O
read	O
information	O
off	O
a	O
floppy	B-Device
disk	I-Device
and	O
store	O
it	O
temporarily	O
in	O
random-access	B-Architecture
memory	I-Architecture
before	O
it	O
is	O
written	O
to	O
the	O
hard	B-Device
drive	I-Device
to	O
be	O
processed	O
at	O
a	O
future	O
date	O
.	O
</s>
<s>
Complementary	O
metal	B-Architecture
–	I-Architecture
oxide	I-Architecture
–	I-Architecture
semiconductor	I-Architecture
(	O
CMOS	O
)	O
is	O
a	O
non-volatile	B-General_Concept
medium	I-General_Concept
.	O
</s>
<s>
It	O
is	O
used	O
in	O
microprocessors	B-Architecture
,	O
microcontrollers	B-Architecture
,	O
static	B-Architecture
RAM	I-Architecture
,	O
and	O
other	O
digital	O
logic	O
circuits	O
.	O
</s>
<s>
Memory	O
is	O
read	O
through	O
the	O
use	O
of	O
a	O
combination	O
of	O
p-type	O
and	O
n-type	O
metal	B-Architecture
–	I-Architecture
oxide	I-Architecture
–	I-Architecture
semiconductor	I-Architecture
field-effect	I-Architecture
transistors	I-Architecture
(	O
MOSFETs	B-Architecture
)	O
.	O
</s>
<s>
In	O
CMOS	O
logic	O
,	O
a	O
collection	O
of	O
n-type	O
MOSFETs	B-Architecture
are	O
arranged	O
in	O
a	O
pull-down	O
network	O
between	O
the	O
output	O
node	O
and	O
the	O
lower-voltage	O
power	O
supply	O
rail	O
,	O
named	O
Vss	O
,	O
which	O
often	O
has	O
ground	O
potential	O
.	O
</s>
<s>
Flash	O
memory	O
stores	O
information	O
in	O
an	O
array	O
of	O
memory	O
cells	O
made	O
from	O
floating-gate	B-Algorithm
transistors	I-Algorithm
.	O
</s>
<s>
In	O
NOR	O
gate	O
flash	O
,	O
each	O
cell	O
resembles	O
a	O
standard	O
MOSFET	B-Architecture
,	O
except	O
the	O
transistor	O
has	O
two	O
gates	O
instead	O
of	O
one	O
.	O
</s>
<s>
On	O
top	O
is	O
the	O
control	O
gate	O
(	O
CG	O
)	O
,	O
as	O
in	O
other	O
MOS	B-Architecture
transistors	I-Architecture
,	O
but	O
below	O
this	O
,	O
there	O
is	O
a	O
floating	B-Algorithm
gate	I-Algorithm
(	O
FG	O
)	O
insulated	O
all	O
around	O
by	O
an	O
oxide	O
layer	O
.	O
</s>
<s>
The	O
FG	O
is	O
interposed	O
between	O
the	O
CG	O
and	O
the	O
MOSFET	B-Architecture
channel	O
,	O
and	O
because	O
the	O
FG	O
is	O
electrically	O
isolated	O
by	O
its	O
insulating	O
layer	O
,	O
any	O
electrons	O
placed	O
on	O
it	O
are	O
trapped	O
there	O
and	O
,	O
under	O
normal	O
conditions	O
,	O
will	O
not	O
discharge	O
for	O
many	O
years	O
.	O
</s>
<s>
When	O
current	O
flow	O
through	O
the	O
MOSFET	B-Architecture
channel	O
binary	O
code	O
is	O
generated	O
,	O
reproducing	O
the	O
stored	O
data	O
.	O
</s>
<s>
NAND	O
flash	O
memory	O
forms	O
the	O
core	O
of	O
the	O
removable	O
USB	B-Protocol
storage	I-Protocol
devices	I-Protocol
known	O
as	O
USB	B-Protocol
flash	O
drives	O
,	O
as	O
well	O
as	O
most	O
memory	B-Device
card	I-Device
formats	O
available	O
today	O
.	O
</s>
<s>
The	O
magnetic	B-Architecture
medium	I-Architecture
is	O
found	O
in	O
magnetic	O
tape	O
,	O
hard	B-Device
disk	I-Device
drives	I-Device
,	O
floppy	B-Device
disks	I-Device
,	O
and	O
so	O
on	O
.	O
</s>
<s>
This	O
medium	O
uses	O
different	O
patterns	O
of	O
magnetization	O
in	O
a	O
magnetizable	O
material	O
to	O
store	O
data	O
and	O
is	O
a	O
form	O
of	O
non-volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Magnetic	B-Architecture
storage	I-Architecture
media	O
can	O
be	O
classified	O
as	O
either	O
sequential	B-General_Concept
access	I-General_Concept
memory	I-General_Concept
or	O
random-access	B-Architecture
memory	I-Architecture
.	O
</s>
<s>
Punched	B-Architecture
cards	I-Architecture
were	O
a	O
common	O
storage	O
medium	O
for	O
computers	O
from	O
1900	O
to	O
1950	O
.	O
</s>
<s>
Optical	O
discs	O
refer	O
to	O
the	O
non-volatile	B-General_Concept
flat	O
,	O
circular	O
,	O
usually	O
polycarbonate	O
discs	O
.	O
</s>
<s>
Random-access	B-Architecture
memory	I-Architecture
(	O
RAM	B-Architecture
)	O
is	O
a	O
form	O
of	O
computer	B-General_Concept
data	I-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
In	O
contrast	O
,	O
other	O
data	O
storage	O
media	O
such	O
as	O
hard	B-Device
disks	I-Device
,	O
CDs	O
,	O
DVDs	O
and	O
magnetic	O
tape	O
,	O
as	O
well	O
as	O
early	O
primary	O
memory	O
types	O
such	O
as	O
drum	O
memory	O
,	O
read	O
and	O
write	O
data	O
only	O
in	O
a	O
predetermined	O
order	O
,	O
consecutively	O
,	O
because	O
of	O
mechanical	O
design	O
limitations	O
.	O
</s>
<s>
Today	O
,	O
random-access	B-Architecture
memory	I-Architecture
takes	O
the	O
form	O
of	O
integrated	O
circuits	O
.	O
</s>
<s>
Strictly	O
speaking	O
,	O
modern	O
types	O
of	O
DRAM	O
are	O
not	O
random	O
access	O
,	O
as	O
data	O
is	O
read	O
in	O
bursts	O
,	O
although	O
the	O
name	O
DRAM	O
/	O
RAM	B-Architecture
has	O
stuck	O
.	O
</s>
<s>
RAM	B-Architecture
is	O
normally	O
associated	O
with	O
volatile	O
types	O
of	O
memory	O
(	O
such	O
as	O
DRAM	O
memory	O
modules	O
)	O
,	O
where	O
its	O
stored	O
information	O
is	O
lost	O
if	O
the	O
power	O
is	O
removed	O
.	O
</s>
<s>
Many	O
other	O
types	O
of	O
non-volatile	B-General_Concept
memory	I-General_Concept
are	O
RAM	B-Architecture
as	O
well	O
,	O
including	O
most	O
types	O
of	O
ROM	O
and	O
a	O
type	O
of	O
flash	O
memory	O
called	O
NOR-Flash	O
.	O
</s>
<s>
The	O
first	O
RAM	B-Architecture
modules	O
to	O
come	O
into	O
the	O
market	O
were	O
created	O
in	O
1951	O
and	O
were	O
sold	O
until	O
the	O
late	O
1960s	O
and	O
early	O
1970s	O
.	O
</s>
