<s>
In	O
programming	O
languages	O
,	O
particularly	O
the	O
compiled	O
ones	O
like	O
C	O
,	O
C++	B-Language
,	O
and	O
D	O
,	O
linkage	B-Language
describes	O
how	O
names	O
can	O
or	O
can	O
not	O
refer	O
to	O
the	O
same	O
entity	O
throughout	O
the	O
whole	O
program	O
or	O
one	O
single	O
translation	B-Language
unit	I-Language
.	O
</s>
<s>
The	O
static	O
keyword	O
is	O
used	O
in	O
C	O
to	O
restrict	O
the	O
visibility	O
of	O
a	O
function	O
or	O
variable	O
to	O
its	O
translation	B-Language
unit	I-Language
.	O
</s>
<s>
This	O
is	O
also	O
valid	O
in	O
C++	B-Language
.	O
</s>
<s>
(	O
C++	B-Language
98/03	O
deprecated	O
this	O
usage	O
in	O
favor	O
of	O
anonymous	O
namespaces	O
,	O
but	O
is	O
no	O
longer	O
deprecated	O
in	O
C++	B-Language
11	O
.	O
)	O
</s>
<s>
Also	O
,	O
C++	B-Language
implicitly	O
treats	O
any	O
const	O
namespace-scope	O
variable	O
as	O
having	O
internal	B-Language
linkage	I-Language
unless	O
it	O
is	O
explicitly	O
declared	O
extern	O
,	O
unlike	O
C	O
.	O
</s>
<s>
A	O
name	O
's	O
linkage	B-Language
is	O
related	O
to	O
,	O
but	O
distinct	O
from	O
,	O
its	O
scope	B-Language
.	O
</s>
<s>
The	O
scope	B-Language
of	O
a	O
name	O
is	O
the	O
part	O
of	O
a	O
translation	B-Language
unit	I-Language
where	O
it	O
is	O
visible	O
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
name	O
with	O
global	O
scope	B-Language
(	O
which	O
is	O
the	O
same	O
as	O
file-scope	O
in	O
C	O
and	O
the	O
same	O
as	O
the	O
global	O
namespace-scope	O
in	O
C++	B-Language
)	O
is	O
visible	O
in	O
any	O
part	O
of	O
the	O
file	O
.	O
</s>
<s>
Its	O
scope	B-Language
will	O
end	O
at	O
the	O
end	O
of	O
the	O
translation	B-Language
unit	I-Language
,	O
whether	O
or	O
not	O
that	O
name	O
has	O
been	O
given	O
external	O
or	O
internal	B-Language
linkage	I-Language
.	O
</s>
<s>
If	O
the	O
name	O
has	O
external	B-Language
linkage	I-Language
,	O
the	O
entity	O
that	O
name	O
denotes	O
may	O
be	O
referred	O
to	O
from	O
another	O
translation	B-Language
unit	I-Language
using	O
a	O
distinct	O
declaration	O
for	O
that	O
same	O
name	O
,	O
and	O
from	O
other	O
scopes	O
within	O
the	O
same	O
translation	B-Language
unit	I-Language
using	O
distinct	O
declarations	O
.	O
</s>
<s>
Were	O
the	O
name	O
given	O
internal	B-Language
linkage	I-Language
,	O
such	O
a	O
declaration	O
would	O
denote	O
a	O
distinct	O
entity	O
,	O
although	O
using	O
the	O
same	O
name	O
,	O
but	O
its	O
entity	O
could	O
be	O
referred	O
to	O
by	O
distinct	O
declarations	O
within	O
the	O
same	O
translation	B-Language
unit	I-Language
.	O
</s>
<s>
A	O
name	O
that	O
has	O
no	O
linkage	B-Language
at	O
all	O
cannot	O
be	O
referred	O
to	O
from	O
declarations	O
in	O
different	O
scopes	O
,	O
not	O
even	O
from	O
within	O
the	O
same	O
translation	B-Language
unit	I-Language
.	O
</s>
<s>
The	O
details	O
differ	O
between	O
C	O
(	O
where	O
only	O
objects	O
and	O
functions	O
-	O
but	O
not	O
types	O
-	O
have	O
linkage	B-Language
)	O
and	O
C++	B-Language
and	O
between	O
this	O
simplified	O
overview	O
.	O
</s>
<s>
Linkage	B-Language
between	O
languages	O
must	O
be	O
done	O
with	O
some	O
care	O
,	O
as	O
different	O
languages	O
adorn	B-Language
their	O
external	O
symbols	O
differently	O
.	O
</s>
<s>
A	O
common	O
idiom	O
uses	O
extern	O
"	O
C	O
"	O
to	O
link	O
C++	B-Language
and	O
C	O
code	O
.	O
</s>
<s>
Definition	O
of	O
'	O
linkage	B-Language
 '	O
quoted	O
from	O
ISO/IEC	O
9899:TC3	O
(	O
C99	O
Standard	O
)	O
.	O
</s>
<s>
C	O
uses	O
the	O
term	O
"	O
identifier	O
"	O
where	O
this	O
article	O
uses	O
"	O
name	O
"	O
(	O
the	O
latter	O
of	O
which	O
is	O
what	O
C++	B-Language
uses	O
to	O
formalize	O
linkage	B-Language
)	O
:	O
</s>
<s>
An	O
identifier	O
declared	O
in	O
different	O
scopes	O
or	O
in	O
the	O
same	O
scope	B-Language
more	O
than	O
once	O
can	O
be	O
made	O
to	O
refer	O
to	O
the	O
same	O
object	O
or	O
function	O
by	O
a	O
process	O
called	O
linkage.ISO/IEC	O
9899	O
.	O
</s>
<s>
The	O
following	O
is	O
a	O
common	O
example	O
of	O
linkage	B-Language
:	O
</s>
<s>
Via	O
linkage	B-Language
,	O
foo	O
called	O
in	O
main( )	O
inside	O
demo1.c	O
refers	O
to	O
foo	O
in	O
demo2.c	O
.	O
</s>
<s>
This	O
is	O
an	O
example	O
of	O
external	B-Language
linkage	I-Language
for	O
a	O
function	O
.	O
</s>
