<s>
CMUCL	B-Language
is	O
a	O
free	B-Application
Common	B-Language
Lisp	I-Language
implementation	O
,	O
originally	O
developed	O
at	O
Carnegie	O
Mellon	O
University	O
.	O
</s>
<s>
CMUCL	B-Language
runs	O
on	O
most	O
Unix-like	B-Operating_System
platforms	O
,	O
including	O
Linux	B-Application
and	O
BSD	B-Operating_System
;	O
there	O
is	O
an	O
experimental	O
Windows	B-Application
port	O
as	O
well	O
.	O
</s>
<s>
Steel	B-Language
Bank	I-Language
Common	I-Language
Lisp	I-Language
is	O
derived	O
from	O
CMUCL	B-Language
.	O
</s>
<s>
The	O
Scieneer	O
Common	B-Language
Lisp	I-Language
is	O
a	O
commercial	O
derivative	O
from	O
CMUCL	B-Language
.	O
</s>
<s>
The	O
earliest	O
implementation	O
predates	O
Common	B-Language
Lisp	I-Language
and	O
was	O
part	O
of	O
Spice	B-Language
Lisp	I-Language
,	O
around	O
1980	O
.	O
</s>
<s>
In	O
1985	O
Rob	O
MacLachlan	O
started	O
re-writing	O
the	O
compiler	B-Language
to	O
what	O
would	O
become	O
the	O
Python	B-Language
compiler	B-Language
and	O
CMUCL	B-Language
was	O
ported	O
to	O
Unix	B-Application
workstations	O
such	O
as	O
the	O
IBM	O
PC	O
RT	O
,	O
MIPS	O
and	O
SPARC	O
.	O
</s>
<s>
Early	O
CMUCL	B-Language
releases	O
did	O
not	O
support	O
Intel	O
's	O
x86	O
architecture	O
due	O
to	O
a	O
lack	O
of	O
registers	O
.	O
</s>
<s>
CMUCL	B-Language
strictly	O
separated	O
type-tagged	O
and	O
immediate	O
data	O
types	O
and	O
the	O
garbage	B-General_Concept
collector	I-General_Concept
would	O
rely	O
on	O
knowing	O
that	O
one	O
half	O
of	O
the	O
CPU	O
registers	O
could	O
only	O
hold	O
tagged	O
types	O
and	O
the	O
other	O
half	O
only	O
untagged	O
types	O
.	O
</s>
<s>
This	O
did	O
not	O
leave	O
enough	O
registers	O
for	O
a	O
Python	B-Language
backend	O
.	O
</s>
<s>
After	O
CMU	O
canceled	O
the	O
project	O
(	O
in	O
favor	O
of	O
a	O
Dylan	B-Language
implementation	O
using	O
some	O
of	O
CMUCL	B-Language
's	O
compiler	B-Language
base	O
)	O
maintenance	O
has	O
been	O
taken	O
over	O
by	O
a	O
group	O
of	O
volunteers	O
.	O
</s>
<s>
Around	O
the	O
same	O
time	O
a	O
port	O
to	O
Intel	O
's	O
x86	O
architecture	O
was	O
completed	O
,	O
first	O
running	O
on	O
FreeBSD	B-Operating_System
,	O
later	O
Linux	B-Application
.	O
</s>
<s>
The	O
problem	O
of	O
lacking	O
registers	O
was	O
solved	O
by	O
a	O
new	O
conservative	O
garbage	B-General_Concept
collector	I-General_Concept
.	O
</s>
<s>
This	O
new	O
garbage	B-General_Concept
collector	I-General_Concept
accepts	O
any	O
value	O
of	O
any	O
type	O
in	O
the	O
registers	O
,	O
and	O
treats	O
anything	O
that	O
might	O
be	O
a	O
pointer	O
as	O
a	O
pointer	O
for	O
the	O
purpose	O
of	O
not	O
collecting	O
or	O
moving	O
its	O
target	O
.	O
</s>
<s>
CMUCL	B-Language
features	O
an	O
interpreter	O
that	O
is	O
mainly	O
used	O
for	O
the	O
REPL	B-Application
,	O
but	O
can	O
be	O
used	O
for	O
faster	O
loading	O
of	O
Lisp	O
files	O
that	O
do	O
n't	O
need	O
compilation	B-Language
.	O
</s>
<s>
A	O
machine	O
to	O
interpret	O
compact	O
bytecode	O
(	O
which	O
can	O
be	O
emitted	O
from	O
the	O
compiler	B-Language
)	O
.	O
</s>
<s>
This	O
is	O
rarely	O
used	O
now	O
,	O
but	O
was	O
popular	O
in	O
early	O
CMUCL	B-Language
releases	O
because	O
image	O
sizes	O
were	O
drastically	O
reduced	O
at	O
a	O
time	O
where	O
download	O
bandwidth	O
on	O
the	O
Internet	O
was	O
low	O
.	O
</s>
<s>
A	O
native	O
code	B-Language
compiler	I-Language
named	O
"	O
Python	B-Language
"	O
(	O
not	O
to	O
be	O
confused	O
with	O
the	B-Language
Python	I-Language
programming	I-Language
language	I-Language
)	O
.	O
</s>
<s>
If	O
Common	B-Language
Lisp	I-Language
source	O
code	O
has	O
been	O
written	O
with	O
appropriate	O
declarations	O
and	O
is	O
organized	O
with	O
speed	O
in	O
mind	O
the	O
Python	B-Language
compiler	B-Language
generates	O
code	O
that	O
is	O
almost	O
free	B-Application
from	O
overhead	O
compared	O
to	O
code	O
compiled	B-Language
from	O
languages	O
like	O
C++	O
.	O
</s>
<s>
Some	O
inefficiencies	O
such	O
as	O
function	O
call	O
interfaces	O
and	O
lack	O
of	O
pointer-free	O
arrays	O
of	O
user-defined	O
data	O
types	O
are	O
dictated	O
by	O
the	O
Common	B-Language
Lisp	I-Language
standard	O
and	O
still	O
need	O
to	O
be	O
worked	O
around	O
(	O
e.g.	O
</s>
<s>
The	O
Python	B-Language
compiler	B-Language
also	O
features	O
powerful	O
type	O
inferences	O
,	O
helping	O
the	O
programmer	O
in	O
writing	O
overhead-free	O
code	O
by	O
either	O
inferring	O
types	O
automatically	O
or	O
issuing	O
hints	O
about	O
missed	O
optimization	O
opportunities	O
.	O
</s>
<s>
Generational	O
garbage	B-General_Concept
collection	I-General_Concept
and	O
multiprocessing	O
capability	O
on	O
the	O
x86	O
ports	O
.	O
</s>
<s>
A	O
foreign	B-Application
function	I-Application
interface	I-Application
which	O
allows	O
interfacing	O
with	O
C	O
code	O
and	O
system	O
libraries	O
,	O
including	O
shared	O
libraries	O
on	O
most	O
platforms	O
,	O
and	O
direct	O
access	O
to	O
Unix	B-Application
system	I-Application
calls	O
.	O
</s>
<s>
Support	O
for	O
interprocess	B-Operating_System
communication	I-Operating_System
and	O
remote	B-Operating_System
procedure	I-Operating_System
calls	I-Operating_System
.	O
</s>
<s>
An	O
implementation	O
of	O
CLOS	B-Application
,	O
the	O
Common	B-Application
Lisp	I-Application
Object	I-Application
System	I-Application
,	O
which	O
includes	O
multimethods	O
and	O
a	O
metaobject	O
protocol	O
.	O
</s>
<s>
A	O
graphical	O
source-level	O
debugger	O
using	O
a	O
Motif	B-Application
interface	I-Application
,	O
and	O
a	O
code	O
profiler	O
.	O
</s>
<s>
An	O
interface	O
to	O
the	O
X11	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
(	O
CLX	B-Language
)	O
,	O
and	O
a	O
sophisticated	O
graphical	O
widget	O
library	O
(	O
Garnet	O
)	O
.	O
</s>
<s>
Hemlock	B-Application
,	O
an	O
Emacs-like	O
editor	O
implemented	O
in	O
Common	B-Language
Lisp	I-Language
.	O
</s>
