<s>
AutoLISP	B-Algorithm
is	O
a	O
dialect	O
of	O
the	O
programming	O
language	O
Lisp	B-Language
built	O
specifically	O
for	O
use	O
with	O
the	O
full	O
version	O
of	O
AutoCAD	B-Algorithm
and	O
its	O
derivatives	O
,	O
which	O
include	O
AutoCAD	B-Algorithm
Map	I-Algorithm
3D	I-Algorithm
,	O
AutoCAD	B-Algorithm
Architecture	I-Algorithm
and	O
AutoCAD	B-Algorithm
Mechanical	I-Algorithm
.	O
</s>
<s>
Neither	O
the	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
nor	O
the	O
interpreter	B-Application
to	O
execute	O
AutoLISP	B-Algorithm
code	O
are	O
included	O
in	O
the	O
AutoCAD	B-Algorithm
LT	O
product	O
line	O
(	O
up	O
to	O
Release	O
2023	O
,	O
AutoCAD	B-Algorithm
LT	O
2024	O
includes	O
AutoLISP	B-Algorithm
)	O
.	O
</s>
<s>
A	O
subset	O
of	O
AutoLISP	B-Algorithm
functions	O
is	O
included	O
in	O
the	O
browser-based	O
AutoCAD	B-Algorithm
web	O
app	O
.	O
</s>
<s>
AutoLISP	B-Algorithm
is	O
a	O
small	O
,	O
dynamically	B-Language
scoped	I-Language
,	O
dynamically	O
typed	O
Lisp	B-Language
language	I-Language
dialect	O
with	O
garbage	B-General_Concept
collection	I-General_Concept
,	O
immutable	O
list	O
structure	O
,	O
and	O
settable	O
symbols	O
,	O
lacking	O
in	O
such	O
regular	O
Lisp	B-Language
features	O
as	O
macro	O
system	O
,	O
records	O
definition	O
facilities	O
,	O
arrays	O
,	O
functions	O
with	O
variable	O
number	O
of	O
arguments	O
or	O
let	O
bindings	O
.	O
</s>
<s>
Aside	O
from	O
the	O
core	O
language	O
,	O
most	O
of	O
the	O
primitive	O
functions	O
are	O
for	O
geometry	O
,	O
accessing	O
AutoCAD	B-Algorithm
's	O
internal	O
DWG	O
database	O
,	O
or	O
manipulation	O
of	O
graphical	O
entities	O
in	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
The	O
properties	O
of	O
these	O
graphical	O
entities	O
are	O
revealed	O
to	O
AutoLISP	B-Algorithm
as	O
association	B-Data_Structure
lists	I-Data_Structure
in	O
which	O
values	O
are	O
paired	O
with	O
AutoCAD	B-Algorithm
group	O
codes	O
that	O
indicate	O
properties	O
such	O
as	O
definitional	O
points	O
,	O
radii	O
,	O
colors	O
,	O
layers	O
,	O
linetypes	O
,	O
etc	O
.	O
</s>
<s>
AutoCAD	B-Algorithm
loads	O
AutoLISP	B-Algorithm
code	O
from	O
.LSP	O
files	O
.	O
</s>
<s>
AutoLISP	B-Algorithm
code	O
can	O
interact	O
with	O
the	O
user	O
through	O
AutoCAD	B-Algorithm
's	O
graphical	O
editor	O
by	O
use	O
of	O
primitive	O
functions	O
that	O
allow	O
the	O
user	O
to	O
pick	O
points	O
,	O
choose	O
objects	O
on	O
screen	O
,	O
and	O
input	O
numbers	O
and	O
other	O
data	O
.	O
</s>
<s>
AutoLisp	B-Algorithm
also	O
has	O
a	O
built-in	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
mini	O
-	O
or	O
domain-specific	B-Language
language	I-Language
(	O
DSL	O
)	O
,	O
the	O
Dialog	B-Language
Control	I-Language
Language	I-Language
,	O
for	O
creating	O
modal	O
dialog	O
boxes	O
with	O
automated	O
layout	O
,	O
within	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
AutoLISP	B-Algorithm
was	O
derived	O
from	O
an	O
early	O
version	O
of	O
XLISP	B-Language
,	O
which	O
was	O
created	O
by	O
David	O
Betz	O
.	O
</s>
<s>
The	O
language	O
was	O
introduced	O
in	O
AutoCAD	B-Algorithm
Version	O
2.18	O
in	O
January	O
1986	O
,	O
and	O
continued	O
to	O
be	O
enhanced	O
in	O
successive	O
releases	O
up	O
to	O
release	O
13	O
in	O
February	O
1995	O
.	O
</s>
<s>
After	O
that	O
,	O
its	O
development	O
was	O
neglected	O
by	O
Autodesk	O
in	O
favor	O
of	O
more	O
fashionable	O
development	O
environments	O
like	O
Visual	B-Language
Basic	I-Language
for	I-Language
Applications	I-Language
(	O
VBA	B-Language
)	O
,	O
.NET	B-Application
Framework	I-Application
,	O
and	O
ObjectARX	B-Application
.	O
</s>
<s>
However	O
,	O
it	O
has	O
remained	O
AutoCAD	B-Algorithm
's	O
main	O
user	O
customizing	O
language	O
.	O
</s>
<s>
Vital-LISP	O
,	O
a	O
considerably	O
enhanced	O
version	O
of	O
AutoLISP	B-Algorithm
including	O
an	O
integrated	B-Application
development	I-Application
environment	I-Application
(	O
IDE	O
)	O
,	O
debugger	B-Application
,	O
compiler	B-Language
,	O
and	O
ActiveX	B-Application
support	O
,	O
was	O
developed	O
and	O
sold	O
by	O
third-party	O
developer	O
Basis	O
Software	O
.	O
</s>
<s>
Vital	B-Algorithm
LISP	I-Algorithm
was	O
a	O
superset	O
of	O
the	O
existing	O
AutoLISP	B-Algorithm
language	O
that	O
added	O
VBA-like	O
access	O
to	O
the	O
AutoCAD	B-Algorithm
object	O
model	O
,	O
reactors	O
(	O
event	O
handling	O
for	O
AutoCAD	B-Algorithm
objects	O
)	O
,	O
general	O
ActiveX	B-Application
support	O
,	O
and	O
some	O
other	O
general	O
Lisp	B-Language
functions	O
.	O
</s>
<s>
Autodesk	O
purchased	O
this	O
,	O
renamed	O
it	O
Visual	B-Algorithm
LISP	I-Algorithm
,	O
and	O
briefly	O
sold	O
it	O
as	O
an	O
add-on	O
to	O
AutoCAD	B-Algorithm
release	O
14	O
released	O
in	O
May	O
1997	O
.	O
</s>
<s>
It	O
was	O
incorporated	O
into	O
AutoCAD	B-Algorithm
2000	I-Algorithm
released	O
in	O
March	O
1999	O
,	O
as	O
a	O
replacement	O
for	O
AutoLISP	B-Algorithm
.	O
</s>
<s>
Since	O
then	O
,	O
Autodesk	O
has	O
ceased	O
major	O
enhancements	O
to	O
Visual	B-Algorithm
LISP	I-Algorithm
and	O
focused	O
more	O
effort	O
on	O
VBA	B-Language
and	O
.NET	B-Application
,	O
and	O
C++	B-Language
.	O
</s>
<s>
,	O
Autodesk	O
no	O
longer	O
supports	O
VBA	B-Language
versions	O
older	O
than	O
7.1	O
.	O
</s>
<s>
This	O
is	O
part	O
of	O
a	O
long-term	O
process	O
of	O
changing	O
from	O
VBA	B-Language
to	O
.NET	B-Application
for	O
user	O
customizing	O
.	O
</s>
<s>
AutoLISP	B-Algorithm
has	O
such	O
a	O
strong	O
following	O
that	O
other	O
computer-aided	B-Application
design	I-Application
(	O
CAD	B-Application
)	O
application	O
vendors	O
add	O
it	O
to	O
their	O
products	O
.	O
</s>
<s>
Bricscad	B-Language
,	O
IntelliCAD	B-Algorithm
,	O
DraftSight	O
and	O
others	O
have	O
AutoLISP	B-Algorithm
functionality	O
,	O
so	O
that	O
AutoLISP	B-Algorithm
users	O
can	O
consider	O
using	O
them	O
as	O
an	O
alternative	O
to	O
AutoCAD	B-Algorithm
.	O
</s>
<s>
Most	O
development	O
involving	O
AutoLISP	B-Algorithm
since	O
AutoCAD	B-Algorithm
2000	I-Algorithm
is	O
performed	O
within	O
Visual	B-Algorithm
LISP	I-Algorithm
since	O
the	O
original	O
AutoLISP	B-Algorithm
engine	O
was	O
replaced	O
with	O
the	O
Visual	B-Algorithm
LISP	I-Algorithm
engine	O
.	O
</s>
<s>
There	O
are	O
thousands	O
of	O
utilities	O
and	O
applications	O
that	O
have	O
been	O
developed	O
using	O
AutoLISP	B-Algorithm
or	O
Visual	B-Algorithm
LISP	I-Algorithm
(	O
distributed	O
as	O
LSP	O
,	O
FAS	O
and	O
VLX	O
files	O
)	O
.	O
</s>
<s>
A	O
simple	O
Hello	O
world	O
program	O
in	O
AutoLISP	B-Algorithm
would	O
be	O
:	O
</s>
<s>
Note	O
the	O
final	O
line	O
inside	O
the	O
function	O
definition	O
:	O
when	O
evaluated	O
with	O
no	O
arguments	O
,	O
the	O
princ	O
function	O
returns	O
a	O
null	O
symbol	O
,	O
which	O
is	O
not	O
displayed	O
by	O
the	O
AutoCAD	B-Algorithm
command-line	B-Application
interface	I-Application
.	O
</s>
<s>
As	O
the	O
AutoCAD	B-Algorithm
command	B-Application
line	I-Application
functions	O
as	O
a	O
read	B-Application
–	I-Application
eval	I-Application
–	I-Application
print	I-Application
loop	I-Application
(	O
REPL	B-Application
)	O
,	O
this	O
would	O
normally	O
print	O
"	O
Hello	O
World	O
!	O
"	O
</s>
<s>
to	O
the	O
command	B-Application
line	I-Application
,	O
followed	O
immediately	O
by	O
the	O
return	O
value	O
of	O
the	O
call	O
to	O
princ	O
.	O
</s>
<s>
The	O
above	O
code	O
defines	O
a	O
new	O
function	O
which	O
generates	O
an	O
AutoCAD	B-Algorithm
point	O
object	O
at	O
a	O
given	O
point	O
,	O
with	O
a	O
one-line	O
text	O
object	O
displaying	O
the	O
X	O
and	O
Y	O
coordinates	O
beside	O
it	O
.	O
</s>
<s>
The	O
name	O
of	O
the	O
function	O
includes	O
a	O
special	O
prefix	O
'	O
c	O
:	O
'	O
,	O
which	O
causes	O
AutoCAD	B-Algorithm
to	O
recognize	O
the	O
function	O
as	O
a	O
regular	O
command	O
.	O
</s>
<s>
The	O
user	O
,	O
upon	O
typing	O
'	O
pointlabel	O
 '	O
at	O
the	O
AutoCAD	B-Algorithm
command	B-Application
line	I-Application
,	O
would	O
be	O
prompted	O
to	O
pick	O
a	O
point	O
,	O
either	O
by	O
typing	O
the	O
X	O
and	O
Y	O
coordinates	O
,	O
or	O
clicking	O
a	O
location	O
in	O
the	O
drawing	O
.	O
</s>
<s>
The	O
above	O
example	O
could	O
also	O
be	O
written	O
using	O
built-in	O
AutoCAD	B-Algorithm
commands	O
to	O
achieve	O
the	O
same	O
result	O
,	O
however	O
this	O
approach	O
is	O
susceptible	O
to	O
changes	O
to	O
the	O
command	O
prompts	O
between	O
AutoCAD	B-Algorithm
releases	O
.	O
</s>
