<s>
Maclisp	B-Language
(	O
or	O
MACLISP	B-Language
,	O
sometimes	O
styled	O
MacLisp	B-Language
or	O
MacLISP	B-Language
)	O
is	O
a	O
programming	O
language	O
,	O
a	O
dialect	O
of	O
the	O
language	O
Lisp	B-Language
.	O
</s>
<s>
It	O
originated	O
at	O
the	O
Massachusetts	O
Institute	O
of	O
Technology	O
's	O
(	O
MIT	O
)	O
Project	O
MAC	O
(	O
from	O
which	O
it	O
derived	O
its	O
prefix	O
)	O
in	O
the	O
late	O
1960s	O
and	O
was	O
based	O
on	O
Lisp	B-Language
1.5	I-Language
.	O
</s>
<s>
Richard	O
Greenblatt	O
was	O
the	O
main	O
developer	O
of	O
the	O
original	O
codebase	O
for	O
the	O
PDP-6	B-Device
;	O
Jon	O
L	O
.	O
White	O
was	O
responsible	O
for	O
its	O
later	O
maintenance	O
and	O
development	O
.	O
</s>
<s>
The	O
name	O
Maclisp	B-Language
began	O
being	O
used	O
in	O
the	O
early	O
1970s	O
to	O
distinguish	O
it	O
from	O
other	O
forks	B-Application
of	O
PDP-6	B-Device
Lisp	B-Language
,	O
notably	O
BBN	B-Language
Lisp	I-Language
.	O
</s>
<s>
Maclisp	B-Language
is	O
a	O
descendant	O
of	O
Lisp	B-Language
1.5	I-Language
.	O
</s>
<s>
Maclisp	B-Language
departs	O
from	O
Lisp	B-Language
1.5	I-Language
by	O
using	O
a	O
value	O
cell	O
to	O
access	O
and	O
store	O
the	O
dynamic	O
values	O
of	O
variables	O
;	O
Lisp	B-Language
1.5	I-Language
used	O
a	O
linear	O
search	O
of	O
an	O
association	O
list	O
to	O
determine	O
a	O
variable	O
's	O
value	O
.	O
</s>
<s>
The	O
Maclisp	B-Language
variable	O
evaluation	O
is	O
faster	O
but	O
has	O
different	O
variable	O
semantics	O
.	O
</s>
<s>
Maclisp	B-Language
also	O
employed	O
reader	O
macros	O
to	O
make	O
more	O
readable	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
,	O
termed	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
.	O
</s>
<s>
Instead	O
of	O
entering	O
(	O
QUOTE	O
A	O
)	O
,	O
one	O
could	O
enter	O
'	O
A	O
to	O
get	O
the	O
same	O
s-expression	B-Protocol
.	O
</s>
<s>
Although	O
both	O
implementations	O
put	O
functions	O
on	O
the	O
property	O
list	O
,	O
Maclisp	B-Language
uses	O
different	O
syntax	O
to	O
define	O
functions	O
.	O
</s>
<s>
Maclisp	B-Language
also	O
has	O
a	O
load-on-demand	O
feature	O
.	O
</s>
<s>
Maclisp	B-Language
began	O
on	O
Digital	O
Equipment	O
Corporation	O
PDP-6	B-Device
and	O
PDP-10	B-Device
computers	O
running	O
the	O
Incompatible	B-Application
Timesharing	I-Application
System	I-Application
(	O
ITS	O
)	O
;	O
later	O
it	O
was	O
ported	O
to	O
all	O
other	O
PDP-10	B-Device
operating	O
systems	O
,	O
for	O
example	O
,	O
Timesharing	O
/	O
Total	O
Operating	O
System	O
,	O
TOPS-10	B-Operating_System
and	O
TOPS-20	B-Operating_System
.	O
</s>
<s>
The	O
original	O
implementation	O
was	O
in	O
assembly	B-Language
language	I-Language
,	O
but	O
a	O
later	O
implementation	O
on	O
Multics	B-Application
used	O
PL/I	B-Language
.	O
</s>
<s>
Maclisp	B-Language
developed	O
considerably	O
in	O
its	O
lifetime	O
.	O
</s>
<s>
Maclisp	B-Language
was	O
used	O
to	O
implement	O
the	O
Macsyma	B-Language
computer	B-General_Concept
algebra	I-General_Concept
system	I-General_Concept
(	O
CAS	O
)	O
or	O
symbolic	B-General_Concept
algebra	I-General_Concept
program	O
.	O
</s>
<s>
Macsyma	B-Language
's	O
development	O
also	O
drove	O
several	O
features	O
in	O
Maclisp	B-Language
.	O
</s>
<s>
The	O
SHRDLU	O
blocks-world	O
program	O
was	O
written	O
in	O
Maclisp	B-Language
,	O
and	O
so	O
the	O
language	O
was	O
in	O
widespread	O
use	O
in	O
the	B-Application
artificial	I-Application
intelligence	I-Application
(	O
AI	B-Application
)	O
research	O
community	O
through	O
the	O
early	O
1980s	O
.	O
</s>
<s>
It	O
was	O
also	O
used	O
to	O
implement	O
other	O
programming	O
languages	O
,	O
such	O
as	O
Planner	B-Application
and	O
Scheme	B-Language
.	O
</s>
<s>
Multics	B-Application
Maclisp	B-Language
was	O
used	O
to	O
implement	O
the	O
first	O
Lisp-based	O
Emacs	B-Application
.	O
</s>
<s>
Maclisp	B-Language
was	O
an	O
influential	O
Lisp	B-Language
implementation	O
,	O
but	O
is	O
no	O
longer	O
maintained	O
actively	O
.	O
</s>
<s>
It	O
now	O
runs	O
on	O
PDP-10	B-Device
emulators	B-Application
and	O
can	O
be	O
used	O
for	O
experimenting	O
with	O
early	O
AI	B-Application
programs	O
.	O
</s>
<s>
Maclisp	B-Language
began	O
with	O
a	O
small	O
,	O
fixed	O
number	O
of	O
data	O
types	O
:	O
cons	B-Protocol
cell	O
,	O
atom	O
(	O
later	O
termed	O
symbol	O
)	O
,	O
integer	O
,	O
and	O
floating-point	B-Algorithm
number	I-Algorithm
.	O
</s>
<s>
Later	O
additions	O
included	O
:	O
arrays	O
,	O
which	O
were	O
never	O
first-class	O
data	O
types	O
;	O
arbitrary-precision	B-Algorithm
integers	I-Algorithm
(	O
bignums	B-Algorithm
)	O
;	O
strings	O
;	O
and	O
tuples	B-Application
.	O
</s>
<s>
Programs	O
could	O
be	O
interpreted	B-Application
or	O
compiled	B-Language
.	O
</s>
<s>
Compiled	B-Language
behavior	O
was	O
the	O
same	O
as	O
interpreted	B-Application
except	O
that	O
local	O
variables	O
were	O
lexical	O
by	O
default	O
in	O
compiled	B-Language
code	O
,	O
unless	O
declared	O
SPECIAL	O
,	O
and	O
no	O
error	O
checking	O
was	O
done	O
for	O
inline	O
operations	O
such	O
as	O
CAR	O
and	O
CDR	O
.	O
</s>
<s>
The	O
Ncomplr	O
compiler	B-Language
(	O
mid-1970s	O
)	O
introduced	O
fast	O
numeric	B-Algorithm
support	O
to	O
Lisp	B-Language
languages	I-Language
,	O
generating	O
machine	B-Language
code	I-Language
(	O
instructions	O
)	O
for	O
arithmetic	O
rather	O
than	O
calling	O
interpretive	O
routines	O
which	O
dispatched	O
on	O
data	O
type	O
.	O
</s>
<s>
This	O
made	O
Lisp	B-Language
arithmetic	O
comparable	O
in	O
speed	O
to	O
Fortran	B-Application
for	O
scalar	O
operations	O
(	O
though	O
Fortran	B-Application
array	O
and	O
loop	O
implementation	O
remained	O
much	O
faster	O
)	O
.	O
</s>
<s>
The	O
original	O
version	O
was	O
limited	O
by	O
the	O
18-bit	O
word	O
memory	B-General_Concept
address	I-General_Concept
of	O
the	O
PDP-10	B-Device
,	O
and	O
considerable	O
effort	O
was	O
expended	O
in	O
keeping	O
the	O
implementation	O
lean	O
and	O
simple	O
.	O
</s>
<s>
Multics	B-Application
Maclisp	B-Language
had	O
a	O
far	O
larger	O
address	O
space	O
,	O
but	O
was	O
costly	O
to	O
use	O
.	O
</s>
<s>
When	O
the	O
memory	O
and	O
processing	O
power	O
of	O
the	O
PDP-10	B-Device
were	O
exceeded	O
,	O
the	O
Lisp	B-Operating_System
Machine	I-Operating_System
was	O
invented	O
:	O
Lisp	B-Language
Machine	I-Language
Lisp	I-Language
is	O
the	O
direct	O
descendant	O
of	O
Maclisp	B-Language
.	O
</s>
<s>
Several	O
other	O
Lisp	B-Language
dialects	O
were	O
also	O
in	O
use	O
,	O
and	O
the	O
need	O
to	O
unify	O
the	O
community	O
resulted	O
in	O
the	O
modern	O
Common	B-Language
Lisp	I-Language
language	I-Language
.	O
</s>
<s>
Maclisp	B-Language
was	O
named	O
for	O
Project	O
MAC	O
,	O
and	O
is	O
unrelated	O
to	O
Apple	O
's	O
Macintosh	B-Device
(	O
Mac	O
)	O
computer	O
,	O
which	O
it	O
predates	O
by	O
decades	O
or	O
to	O
John	O
McCarthy	O
.	O
</s>
<s>
The	O
various	O
Lisp	B-Language
systems	O
for	O
the	O
Macintosh	B-Device
have	O
no	O
particular	O
similarity	O
to	O
Maclisp	B-Language
.	O
</s>
