<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
a	O
quaject	B-Operating_System
is	O
an	O
object-like	O
data	B-General_Concept
structure	I-General_Concept
containing	O
both	O
data	O
and	O
code	O
(	O
or	O
pointers	O
to	O
code	O
)	O
,	O
exposed	O
as	O
an	O
interface	O
in	O
the	O
form	O
of	O
callentries	B-Language
,	O
and	O
can	O
accept	O
a	O
list	O
of	O
callentries	B-Language
to	O
other	O
quajects	B-Operating_System
for	O
callbacks	O
and	O
callouts	O
.	O
</s>
<s>
The	O
origin	O
of	O
the	O
term	O
'	O
qua	O
 '	O
is	O
unclear	O
;	O
Massalin	O
claims	O
humorously	O
that	O
it	O
is	O
a	O
sound	O
made	O
by	O
koalas	B-Operating_System
.	O
</s>
<s>
The	O
main	O
purpose	O
of	O
quajects	B-Operating_System
is	O
to	O
provide	O
an	O
abstraction	B-Application
to	O
manage	O
self-modifying	B-Application
code	I-Application
,	O
by	O
allowing	O
runtime	O
code	O
optimizing	O
on	O
a	O
per-object	O
basis	O
.	O
</s>
<s>
While	O
the	O
original	O
Synthesis	O
kernel	O
required	O
quajects	B-Operating_System
to	O
be	O
written	O
in	O
hand-developed	O
assembly	B-Language
language	I-Language
,	O
this	O
was	O
done	O
to	O
avoid	O
developing	O
a	O
complex	O
compiler	O
;	O
Massalin	O
noted	O
that	O
just-in-time	O
compilation	O
(	O
JIT	O
)	O
for	O
a	O
high-level	B-Language
programming	I-Language
language	I-Language
that	O
permits	O
runtime	B-Application
code	I-Application
generation	I-Application
,	O
as	O
in	O
Lisp	B-Language
or	O
Smalltalk	B-Application
,	O
can	O
also	O
apply	O
this	O
approach	O
,	O
though	O
she	O
also	O
asserted	O
that	O
the	O
complexity	O
of	O
such	O
a	O
compiler	O
was	O
likely	O
to	O
be	O
prohibitive	O
.	O
</s>
<s>
Quajects	B-Operating_System
differ	O
from	O
more	O
conventional	O
objects	O
in	O
two	O
key	O
ways	O
:	O
first	O
,	O
they	O
always	O
use	O
a	O
form	O
of	O
the	O
dependency	B-Library
injection	I-Library
pattern	O
to	O
manage	O
both	O
interfaces	O
to	O
other	O
quajects	B-Operating_System
,	O
and	O
continuations	O
out	O
of	O
the	O
quaject	B-Operating_System
;	O
the	O
list	O
of	O
callentry	O
references	O
for	O
this	O
is	O
part	O
of	O
quaject	B-Operating_System
creation	O
,	O
and	O
may	O
be	O
updated	O
during	O
the	O
quaject	B-Operating_System
's	O
lifetime	O
.	O
</s>
<s>
Second	O
,	O
and	O
more	O
critically	O
,	O
a	O
given	O
quaject	B-Operating_System
's	O
set	O
of	O
methods	O
can	O
be	O
unique	O
to	O
the	O
specific	O
quaject	B-Operating_System
;	O
methods	O
for	O
a	O
type	O
or	O
class	O
of	O
quajects	B-Operating_System
are	O
stored	O
as	O
one	O
or	O
more	O
templates	O
,	O
rather	O
than	O
as	O
fixed	O
code	O
.	O
</s>
<s>
While	O
shared	O
methods	O
can	O
be	O
accessed	O
through	O
a	O
common	O
table	O
of	O
pointers	O
,	O
individual	O
quajects	B-Operating_System
can	O
also	O
have	O
methods	O
that	O
are	O
generated	O
specifically	O
to	O
tailor	O
the	O
performance	O
for	O
that	O
quaject	B-Operating_System
's	O
behavior	O
.	O
</s>
