<s>
Handel-C	B-Language
is	O
a	O
high-level	B-Language
programming	I-Language
language	I-Language
which	O
targets	O
low-level	O
hardware	O
,	O
most	O
commonly	O
used	O
in	O
the	O
programming	O
of	O
FPGAs	B-Architecture
.	O
</s>
<s>
It	O
is	O
a	O
rich	O
subset	O
of	O
C	B-Language
,	O
with	O
non-standard	O
extensions	O
to	O
control	O
hardware	O
instantiation	O
with	O
an	O
emphasis	O
on	O
parallelism	B-Operating_System
.	O
</s>
<s>
Handel-C	B-Language
is	O
to	O
hardware	O
design	O
what	O
the	O
first	O
high-level	B-Language
programming	I-Language
languages	I-Language
were	O
to	O
programming	O
CPUs	O
.	O
</s>
<s>
Unlike	O
many	O
other	O
design	O
languages	O
that	O
target	O
a	O
specific	O
architecture	O
Handel-C	B-Language
can	O
be	O
compiled	O
to	O
a	O
number	O
of	O
design	O
languages	O
and	O
then	O
synthesised	O
to	O
the	O
corresponding	O
hardware	O
.	O
</s>
<s>
The	O
subset	O
of	O
C	B-Language
includes	O
all	O
common	O
C	B-Language
language	I-Language
features	O
necessary	O
to	O
describe	O
complex	O
algorithms	O
.	O
</s>
<s>
Like	O
many	O
embedded	O
C	B-Language
compilers	O
,	O
floating	B-Algorithm
point	I-Algorithm
data	O
types	O
were	O
omitted	O
.	O
</s>
<s>
Floating	B-Algorithm
point	I-Algorithm
arithmetic	I-Algorithm
is	O
supported	O
through	O
external	O
libraries	O
that	O
are	O
very	O
efficient	O
.	O
</s>
<s>
In	O
order	O
to	O
facilitate	O
a	O
way	O
to	O
describe	O
parallel	B-Operating_System
behavior	I-Operating_System
some	O
of	O
the	O
CSP	O
keywords	O
are	O
used	O
,	O
along	O
with	O
the	O
general	O
file	O
structure	O
of	O
Occam	B-Language
.	O
</s>
<s>
Channels	B-Operating_System
provide	O
a	O
mechanism	O
for	O
message	B-Architecture
passing	I-Architecture
between	O
parallel	B-Operating_System
threads	I-Operating_System
.	O
</s>
<s>
Channels	B-Operating_System
can	O
be	O
defined	O
as	O
asynchronous	O
or	O
synchronous	O
(	O
with	O
or	O
without	O
an	O
inferred	O
storage	O
element	O
respectively	O
)	O
.	O
</s>
<s>
A	O
thread	O
writing	O
to	O
a	O
synchronous	O
channel	O
will	O
be	O
immediately	O
blocked	B-Operating_System
until	O
the	O
corresponding	O
listening	O
thread	O
is	O
ready	O
to	O
receive	O
the	O
message	O
.	O
</s>
<s>
Asynchronous	O
channels	B-Operating_System
provide	O
a	O
specified	O
amount	O
of	O
storage	O
for	O
data	O
passing	O
through	O
them	O
in	O
the	O
form	O
of	O
a	O
FIFO	B-Operating_System
.	O
</s>
<s>
Whilst	O
this	O
FIFO	B-Operating_System
neither	O
full	O
nor	O
empty	O
,	O
both	O
sending	O
and	O
receiving	O
threads	O
may	O
proceed	O
without	O
being	O
blocked	B-Operating_System
.	O
</s>
<s>
However	O
,	O
when	O
the	O
FIFO	B-Operating_System
is	O
empty	O
,	O
the	O
receiving	O
thread	O
will	O
block	O
at	O
the	O
next	O
read	O
.	O
</s>
<s>
A	O
thread	O
may	O
simultaneously	O
wait	O
on	O
multiple	O
channels	B-Operating_System
,	O
synchronous	O
or	O
asynchronous	O
,	O
acting	O
upon	O
the	O
first	O
one	O
available	O
given	O
a	O
specified	O
order	O
of	O
priority	O
or	O
optionally	O
executing	O
an	O
alternate	O
path	O
if	O
none	O
is	O
ready	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
effects	O
the	O
standard	O
semantics	O
of	O
C	B-Language
have	O
on	O
the	O
timing	O
of	O
the	O
program	O
,	O
the	O
following	O
keywords	O
are	O
reserved	O
for	O
describing	O
the	O
practicalities	O
of	O
the	O
FPGA	B-Architecture
environment	O
or	O
for	O
the	O
language	O
elements	O
sourced	O
from	O
Occam	B-Language
:	O
</s>
<s>
In	O
Handel-C	B-Language
,	O
assignment	O
and	O
the	O
delay	O
command	O
take	O
one	O
cycle	O
.	O
</s>
<s>
This	O
allows	O
programmers	O
to	O
manually	O
schedule	O
tasks	O
and	O
create	O
effective	O
pipelines	B-General_Concept
.	O
</s>
<s>
By	O
arranging	O
loops	O
in	O
parallel	O
with	O
the	O
correct	O
delays	O
,	O
pipelines	B-General_Concept
can	O
massively	O
increase	O
data	O
throughput	O
,	O
at	O
the	O
expense	O
of	O
increased	O
hardware	O
resource	O
use	O
.	O
</s>
<s>
The	O
historical	O
roots	O
of	O
Handel-C	B-Language
are	O
in	O
a	O
series	O
of	O
Oxford	O
University	O
Computing	O
Laboratory	O
hardware	O
description	O
languages	O
developed	O
by	O
the	O
hardware	O
compilation	O
group	O
.	O
</s>
<s>
Handel	O
HDL	O
evolved	O
into	O
Handel-C	B-Language
around	O
early	O
1996	O
.	O
</s>
<s>
Handel-C	B-Language
was	O
adopted	O
by	O
many	O
University	O
Hardware	O
Research	O
groups	O
after	O
its	O
release	O
by	O
ESL	O
,	O
as	O
a	O
result	O
was	O
able	O
to	O
establish	O
itself	O
as	O
a	O
hardware	O
design	O
tool	O
of	O
choice	O
within	O
the	O
academic	O
community	O
,	O
especially	O
in	O
the	O
United	O
Kingdom	O
.	O
</s>
<s>
In	O
early	O
2008	O
,	O
Celoxica	O
's	O
ESL	O
business	O
was	O
acquired	O
by	O
Agility	O
,	O
which	O
developed	O
and	O
sold	O
,	O
among	O
other	O
products	O
,	O
ESL	O
tools	O
supporting	O
Handel-C	B-Language
.	O
</s>
<s>
In	O
January	O
2009	O
,	O
Mentor	O
Graphics	O
acquired	O
Agility	O
's	O
C	B-Language
synthesis	O
assets	O
.	O
</s>
