<s>
CAL	O
(	O
the	O
Cal	B-Language
Actor	I-Language
Language	I-Language
)	O
is	O
a	O
high-level	B-Language
programming	I-Language
language	I-Language
for	O
writing	O
(	O
dataflow	B-Application
)	O
actors	O
,	O
which	O
are	O
stateful	O
operators	O
that	O
transform	O
input	O
streams	O
of	O
data	O
objects	O
(	O
tokens	O
)	O
into	O
output	O
streams	O
.	O
</s>
<s>
CAL	O
has	O
been	O
compiled	O
to	O
a	O
variety	O
of	O
target	O
platforms	O
,	O
including	O
single-core	O
processors	O
,	O
multicore	O
processors	O
,	O
and	O
programmable	O
hardware	B-Architecture
.	O
</s>
<s>
It	O
has	O
been	O
used	O
in	O
several	O
application	O
areas	O
,	O
including	O
video	O
and	O
processing	O
,	O
compression	B-General_Concept
and	O
cryptography	O
.	O
</s>
<s>
The	O
MPEG	O
Reconfigurable	B-Algorithm
Video	I-Algorithm
Coding	I-Algorithm
(	O
RVC	O
)	O
working	O
group	O
has	O
adopted	O
CAL	O
as	O
part	O
of	O
their	O
standardization	O
efforts	O
.	O
</s>
<s>
The	O
CAL	B-Language
Actor	I-Language
Language	I-Language
was	O
developed	O
in	O
2001	O
as	O
part	O
of	O
the	O
Ptolemy	O
II	O
project	O
at	O
University	O
of	O
California	O
at	O
Berkeley	O
.	O
</s>
<s>
CAL	O
is	O
a	O
dataflow	B-Application
language	I-Application
geared	O
towards	O
a	O
variety	O
of	O
application	O
domains	O
,	O
such	O
as	O
multimedia	O
processing	O
,	O
control	O
systems	O
,	O
network	B-General_Concept
processing	I-General_Concept
etc	O
.	O
</s>
<s>
Another	O
common	O
reason	O
for	O
choosing	O
dataflow	B-Application
is	O
that	O
the	O
goal	O
is	O
an	O
efficient	O
parallel	O
implementation	O
which	O
would	O
be	O
difficult	O
or	O
impossible	O
to	O
achieve	O
using	O
a	O
sequential	B-Architecture
programming	I-Architecture
language	O
.	O
</s>
<s>
A	O
CAL	O
dataflow	B-Application
program	O
provides	O
simple	O
,	O
understandable	O
,	O
and	O
powerful	O
abstractions	O
that	O
allow	O
the	O
specification	O
of	O
as	O
much	O
or	O
as	O
little	O
parallelism	B-Operating_System
as	O
is	O
required	O
,	O
enabling	O
tools	O
to	O
produce	O
sophisticated	O
implementations	O
that	O
exploit	O
the	O
concurrent	B-Operating_System
structure	O
of	O
a	O
computation	O
.	O
</s>
<s>
When	O
programming	O
in	O
dataflow	B-Application
,	O
the	O
programmer	B-Application
is	O
typically	O
constructing	O
a	O
concurrent	B-Operating_System
description	O
of	O
a	O
computational	O
system	O
,	O
which	O
is	O
different	O
from	O
a	O
common	O
sequential	O
program	O
.	O
</s>
<s>
Rather	O
than	O
being	O
concerned	O
with	O
the	O
step-by-step	O
execution	O
of	O
an	O
algorithm	O
,	O
a	O
dataflow	B-Application
programmer	B-Application
builds	O
a	O
system	O
of	O
asynchronously	B-Architecture
communicating	O
entities	O
called	O
actors	O
.	O
</s>
<s>
The	O
main	O
purpose	O
of	O
actor	O
parameters	O
is	O
to	O
allow	O
programmers	B-Application
to	O
specify	O
families	O
of	O
related	O
actors	O
,	O
without	O
having	O
to	O
duplicate	O
a	O
lot	O
of	O
code	O
.	O
</s>
<s>
This	O
part	O
of	O
the	O
language	O
is	O
similar	O
to	O
what	O
can	O
be	O
found	O
in	O
many	O
procedural	O
programming	O
languages	O
(	O
such	O
as	O
C	B-Language
,	O
Pascal	O
,	O
Java	B-Language
,	O
Ada	B-Language
)	O
,	O
so	O
we	O
will	O
focus	O
on	O
areas	O
that	O
might	O
be	O
slightly	O
different	O
in	O
CAL	O
.	O
</s>
<s>
Unlike	O
languages	O
such	O
as	O
C	B-Language
,	O
CAL	O
makes	O
a	O
strong	O
distinction	O
between	O
statements	O
and	O
expressions	O
.	O
</s>
