<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
a	O
stream	O
is	O
a	O
sequence	O
of	O
data	O
elements	O
made	O
available	O
over	O
time	O
.	O
</s>
<s>
Streams	O
are	O
processed	O
differently	O
from	O
batch	B-General_Concept
data	I-General_Concept
–	O
normal	O
functions	O
cannot	O
operate	O
on	O
streams	O
as	O
a	O
whole	O
,	O
as	O
they	O
have	O
potentially	O
unlimited	O
data	O
,	O
and	O
formally	O
,	O
streams	O
are	O
codata	O
(	O
potentially	O
unlimited	O
)	O
,	O
not	O
data	O
(	O
which	O
is	O
finite	O
)	O
.	O
</s>
<s>
Functions	O
that	O
operate	O
on	O
a	O
stream	O
,	O
producing	O
another	O
stream	O
,	O
are	O
known	O
as	O
filters	B-Application
,	O
and	O
can	O
be	O
connected	O
in	O
pipelines	B-General_Concept
,	O
analogously	O
to	O
function	B-Application
composition	I-Application
.	O
</s>
<s>
Filters	B-Application
may	O
operate	O
on	O
one	O
item	O
of	O
a	O
stream	O
at	O
a	O
time	O
,	O
or	O
may	O
base	O
an	O
item	O
of	O
output	O
on	O
multiple	O
items	O
of	O
input	O
,	O
such	O
as	O
a	O
moving	O
average	O
.	O
</s>
<s>
"	O
Stream	O
editing	O
"	O
,	O
as	O
with	O
sed	B-Application
,	O
awk	B-Application
,	O
and	O
perl	B-Language
.	O
</s>
<s>
On	O
Unix	B-Application
and	O
related	O
systems	O
based	O
on	O
the	O
C	B-Language
language	I-Language
,	O
a	O
stream	O
is	O
a	O
source	O
or	O
sink	B-Application
of	O
data	O
,	O
usually	O
individual	O
bytes	O
or	O
characters	O
.	O
</s>
<s>
Streams	O
are	O
an	O
abstraction	O
used	O
when	O
reading	O
or	O
writing	O
files	O
,	O
or	O
communicating	O
over	O
network	B-Protocol
sockets	I-Protocol
.	O
</s>
<s>
The	O
standard	B-Operating_System
streams	I-Operating_System
are	O
three	O
streams	O
made	O
available	O
to	O
all	O
programs	O
.	O
</s>
<s>
In	O
object-oriented	B-Language
programming	I-Language
,	O
input	B-Architecture
streams	I-Architecture
are	O
generally	O
implemented	O
as	O
iterators	O
.	O
</s>
<s>
In	O
the	O
Scheme	B-Language
language	I-Language
and	O
some	O
others	O
,	O
a	O
stream	O
is	O
a	O
lazily	O
evaluated	O
or	O
delayed	O
sequence	O
of	O
data	O
elements	O
.	O
</s>
<s>
In	O
the	O
Smalltalk	B-Application
standard	B-Library
library	I-Library
and	O
in	O
other	O
programming	O
languages	O
as	O
well	O
,	O
a	O
stream	O
is	O
an	O
external	O
iterator	O
.	O
</s>
<s>
Stream	B-Application
processing	I-Application
—	O
in	O
parallel	B-Operating_System
processing	I-Operating_System
,	O
especially	O
in	O
graphic	O
processing	O
,	O
the	O
term	O
stream	O
is	O
applied	O
to	O
hardware	B-Architecture
as	O
well	O
as	O
software	O
.	O
</s>
<s>
There	O
it	O
defines	O
the	O
quasi-continuous	O
flow	O
of	O
data	O
that	O
is	O
processed	O
in	O
a	O
dataflow	B-Application
programming	I-Application
language	I-Application
as	O
soon	O
as	O
the	O
program	O
state	O
meets	O
the	O
starting	O
condition	O
of	O
the	O
stream	O
.	O
</s>
<s>
Streams	O
can	O
be	O
used	O
as	O
the	O
underlying	O
data	O
type	O
for	O
channels	B-Operating_System
in	O
interprocess	B-Operating_System
communication	I-Operating_System
.	O
</s>
<s>
The	O
term	O
"	O
stream	O
"	O
is	O
also	O
applied	O
to	O
file	B-Application
system	I-Application
forks	B-Application
,	O
where	O
multiple	O
sets	O
of	O
data	O
are	O
associated	O
with	O
a	O
single	O
filename	O
.	O
</s>
<s>
Most	O
often	O
,	O
there	O
is	O
one	O
main	O
stream	O
that	O
makes	O
up	O
the	O
normal	O
file	O
data	O
,	O
while	O
additional	O
streams	O
contain	O
metadata	B-Language
.	O
</s>
<s>
Here	O
"	O
stream	O
"	O
is	O
used	O
to	O
indicate	O
"	O
variable	O
size	O
data	O
"	O
,	O
as	O
opposed	O
to	O
fixed	O
size	O
metadata	B-Language
such	O
as	O
extended	B-Application
attributes	I-Application
,	O
but	O
differs	O
from	O
"	O
stream	O
"	O
as	O
used	O
otherwise	O
,	O
meaning	O
"	O
data	O
available	O
over	O
time	O
,	O
potentially	O
infinite	O
"	O
.	O
</s>
