<s>
ObjectARX	B-Application
(	O
AutoCAD	B-Algorithm
Runtime	O
eXtension	O
)	O
is	O
an	O
API	B-General_Concept
for	O
customizing	O
and	O
extending	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
The	O
ObjectARX	B-Application
SDK	B-Application
is	O
published	O
by	O
Autodesk	O
and	O
freely	O
available	O
under	O
license	O
from	O
Autodesk	O
.	O
</s>
<s>
The	O
ObjectARX	B-Application
SDK	B-Application
consists	O
primarily	O
of	O
C++	B-Language
headers	O
and	O
libraries	O
that	O
can	O
be	O
used	O
to	O
build	O
Windows	O
DLLs	O
that	O
can	O
be	O
loaded	O
into	O
the	O
AutoCAD	B-Algorithm
process	O
and	O
interact	O
directly	O
with	O
the	O
AutoCAD	B-Algorithm
application	O
.	O
</s>
<s>
ObjectARX	B-Application
modules	O
use	O
the	O
file	O
extensions	O
.arx	O
and	O
.dbx	O
instead	O
of	O
the	O
more	O
common	O
.dll	O
.	O
</s>
<s>
ObjectARX	B-Application
is	O
the	O
most	O
powerful	O
of	O
the	O
various	O
AutoCAD	B-Algorithm
APIs	B-General_Concept
,	O
and	O
the	O
most	O
difficult	O
to	O
master	O
.	O
</s>
<s>
The	O
typical	O
audience	O
for	O
the	O
ObjectARX	B-Application
SDK	B-Application
includes	O
professional	O
programmers	O
working	O
either	O
as	O
commercial	O
application	O
developers	O
or	O
as	O
in-house	O
developers	O
at	O
companies	O
using	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
New	O
versions	O
of	O
the	O
ObjectARX	B-Application
SDK	B-Application
are	O
released	O
with	O
each	O
new	O
AutoCAD	B-Algorithm
release	O
,	O
and	O
ObjectARX	B-Application
modules	O
built	O
with	O
a	O
specific	O
SDK	B-Application
version	O
are	O
typically	O
limited	O
to	O
running	O
inside	O
the	O
corresponding	O
version	O
of	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
Recent	O
versions	O
of	O
the	O
ObjectARX	B-Application
SDK	B-Application
include	O
support	O
for	O
the	O
.NET	B-Application
platform	I-Application
by	O
providing	O
managed	O
wrapper	O
classes	O
for	O
native	O
objects	O
and	O
functions	O
.	O
</s>
<s>
The	O
native	O
classes	O
and	O
libraries	O
that	O
are	O
made	O
available	O
via	O
the	O
ObjectARX	B-Application
API	B-General_Concept
are	O
also	O
used	O
internally	O
by	O
the	O
AutoCAD	B-Algorithm
code	O
.	O
</s>
<s>
As	O
a	O
result	O
of	O
this	O
tight	O
linkage	O
with	O
AutoCAD	B-Algorithm
itself	O
,	O
the	O
libraries	O
are	O
very	O
compiler	O
specific	O
,	O
and	O
work	O
only	O
with	O
the	O
same	O
compiler	O
that	O
Autodesk	O
uses	O
to	O
build	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
Historically	O
,	O
this	O
has	O
required	O
ObjectARX	B-Application
developers	O
to	O
use	O
various	O
versions	O
of	O
Microsoft	B-Application
Visual	I-Application
Studio	I-Application
,	O
with	O
different	O
versions	O
of	O
the	O
SDK	B-Application
requiring	O
different	O
versions	O
of	O
Visual	B-Application
Studio	I-Application
.	O
</s>
<s>
Although	O
ObjectARX	B-Application
is	O
specific	O
to	O
AutoCAD	B-Algorithm
,	O
Open	O
Design	O
Alliance	O
announced	O
in	O
2008	O
a	O
new	O
API	B-General_Concept
called	O
DRX	O
(	O
included	O
in	O
their	O
DWGdirect	O
library	O
)	O
that	O
attempts	O
to	O
emulate	O
the	O
ObjectARX	B-Application
API	B-General_Concept
in	O
products	O
like	O
IntelliCAD	B-Algorithm
that	O
use	O
the	O
DWGdirect	O
libraries	O
.	O
</s>
