<s>
Charm	B-Device
is	O
a	O
computer	O
programming	O
language	O
devised	O
in	O
the	O
early	O
1990s	O
with	O
similarities	O
to	O
the	O
RTL/2	B-Language
,	O
Pascal	B-Application
and	O
C	B-Language
languages	I-Language
in	O
addition	O
to	O
containing	O
some	O
unique	O
features	O
of	O
its	O
own	O
.	O
</s>
<s>
The	O
Charm	B-Device
language	O
is	O
defined	O
by	O
a	O
context-free	O
grammar	O
amenable	O
to	O
being	O
processed	O
by	O
recursive	B-Application
descent	I-Application
parser	I-Application
as	O
described	O
in	O
seminal	O
books	O
on	O
compiler	B-Language
design	O
.	O
</s>
<s>
A	O
set	O
of	O
Charm	B-Device
tools	O
including	O
a	O
compiler	B-Language
,	O
assembler	O
and	O
linker	O
was	O
made	O
available	O
for	O
Acorn	O
's	O
RISC	B-Operating_System
OS	I-Operating_System
platform	O
.	O
</s>
<s>
Charm	B-Device
reworked	O
for	O
RISC	B-Operating_System
OS	I-Operating_System
platforms	O
has	O
subsequently	O
been	O
reviewed	O
in	O
Archive	O
magazine	O
.	O
</s>
<s>
Charm	B-Device
is	O
further	O
described	O
in	O
the	O
e-book	O
Programming	O
in	O
Charm	B-Device
on	O
the	O
Raspberry	B-Operating_System
Pi	I-Operating_System
.	O
</s>
<s>
The	O
definition	O
of	O
the	O
Charm	B-Device
grammar	O
in	O
Backus	O
–	O
Naur	O
form	O
along	O
with	O
descriptive	O
examples	O
of	O
Charm	B-Device
constructs	O
is	O
defined	O
on	O
the	O
Charm	B-Device
.	O
</s>
<s>
Each	O
grammatically	O
conforming	O
text	O
represents	O
a	O
collection	O
of	O
executable	O
code	O
and	O
associated	O
data	O
which	O
can	O
be	O
used	O
by	O
a	O
Charm	B-Device
tool	O
set	O
as	O
a	O
component	O
when	O
assembling	O
a	O
program	O
that	O
can	O
be	O
run	O
under	O
an	O
operating	O
system	O
utilising	O
the	O
services	O
it	O
provides	O
to	O
do	O
useful	O
work	O
such	O
as	O
data	O
processing	O
or	O
interacting	O
with	O
users	O
through	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
.	O
</s>
<s>
Charm	B-Device
is	O
a	O
strongly	O
typed	O
language	O
,	O
but	O
does	O
allow	O
some	O
implicit	O
conversions	O
between	O
numeric	O
and	O
floating	O
point	O
types	O
.	O
</s>
<s>
Modules	O
may	O
also	O
define	O
a	O
constructor	O
procedure	O
to	O
initialise	O
dynamic	O
data	O
and	O
corresponding	O
deconstructor	O
procedure	O
to	O
release	O
resources	O
in	O
a	O
similar	O
manner	O
to	O
the	O
C++	O
language	O
.	O
</s>
<s>
If	O
a	O
module	O
wishes	O
to	O
reference	O
a	O
procedure	O
or	O
data	O
from	O
another	O
Charm	B-Device
module	O
,	O
it	O
does	O
so	O
using	O
the	O
keyword	O
.	O
</s>
<s>
The	O
original	O
classic	O
Hello	O
world	O
program	O
written	O
in	O
Charm	B-Device
is	O
:	O
</s>
<s>
Tool	O
set	O
implementations	O
are	O
expected	O
to	O
provide	O
a	O
compiler	B-Language
and	O
an	O
assembler	O
to	O
generate	O
object	O
files	O
from	O
Charm	B-Device
source	O
code	O
and	O
assembler	O
source	O
code	O
,	O
which	O
can	O
then	O
be	O
linked	O
together	O
along	O
with	O
library	O
and	O
run	O
time	O
support	O
files	O
to	O
generate	O
an	O
executable	O
program	O
.	O
</s>
<s>
At	O
the	O
time	O
of	O
writing	O
only	O
one	O
Charm	B-Device
tool	O
set	O
installation	B-Application
is	O
available	O
(	O
free	O
of	O
charge	O
)	O
for	O
download	O
.	O
</s>
<s>
The	O
tools	O
are	O
themselves	O
written	O
in	O
the	O
Charm	B-Device
language	O
,	O
and	O
the	O
source	O
code	O
is	O
available	O
under	O
the	O
terms	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
They	O
run	O
on	O
RISC	B-Operating_System
OS	I-Operating_System
PCs	O
and	O
platforms	O
with	O
ARM	O
CPUs	O
(	O
such	O
as	O
the	O
Raspberry	B-Operating_System
Pi	I-Operating_System
)	O
and	O
on	O
emulators	O
for	O
RISC	B-Operating_System
OS	I-Operating_System
which	O
are	O
hosted	O
on	O
Windows	O
or	O
Linux	O
platforms	O
(	O
such	O
as	O
RPCEmu	O
)	O
.	O
</s>
<s>
Code	O
generation	O
for	O
hardware	O
assisted	O
double	O
precision	O
floating	O
point	O
operations	O
is	O
supported	O
for	O
platforms	O
based	O
on	O
ARM	B-Architecture
chips	I-Architecture
that	O
support	O
the	O
VFP	O
version	O
2	O
coprocessor	O
architecture	O
.	O
</s>
<s>
The	O
Charm	B-Device
compiler	B-Language
is	O
a	O
recursive	B-Application
descent	I-Application
single	O
pass	O
compiler	B-Language
which	O
parses	O
Charm	B-Device
source	O
code	O
to	O
generate	O
quadruples	O
of	O
the	O
form	O
result	O
:=	O
lhs	O
op	O
rhs	O
in	O
an	O
intermediate	O
language	O
that	O
supports	O
arithmetic	O
,	O
logical	O
and	O
flow	O
of	O
control	O
operations	O
.	O
</s>
<s>
Data	O
is	O
stored	O
in	O
temporaries	O
which	O
are	O
assigned	O
to	O
registers	O
and	O
memory	O
locations	O
in	O
the	O
back	O
end	O
of	O
the	O
compiler	B-Language
.	O
</s>
<s>
Two	O
back	O
ends	O
are	O
currently	O
in	O
existence	O
,	O
one	O
generating	O
Motorola	B-Device
68000	I-Device
assembly	O
language	O
,	O
and	O
the	O
other	O
generating	O
ARM	B-Architecture
architecture	I-Architecture
.	O
</s>
<s>
In	O
more	O
recent	O
releases	O
of	O
Charm	B-Device
,	O
the	O
I/O	O
procedures	O
have	O
been	O
split	O
into	O
their	O
own	O
modules	O
In	O
and	O
Out	O
.	O
</s>
<s>
One	O
and	O
only	O
one	O
of	O
the	O
Charm	B-Device
modules	O
linked	O
to	O
form	O
an	O
executable	O
program	O
must	O
contain	O
a	O
procedure	O
matching	O
one	O
of	O
the	O
signatures	O
:	O
</s>
<s>
This	O
is	O
analogous	O
to	O
the	O
main	O
function	O
in	O
the	O
C	B-Language
and	O
Java	B-Language
languages	I-Language
.	O
</s>
