<s>
In	O
computing	O
,	O
a	O
system	B-Operating_System
image	I-Operating_System
is	O
a	O
serialized	B-Application
copy	O
of	O
the	O
entire	O
state	B-Application
of	O
a	O
computer	O
system	O
stored	O
in	O
some	O
non-volatile	O
form	O
such	O
as	O
a	O
file	B-Operating_System
.	O
</s>
<s>
A	O
system	O
is	O
said	O
to	O
be	O
capable	O
of	O
using	O
system	B-Operating_System
images	I-Operating_System
if	O
it	O
can	O
be	O
shut	O
down	O
and	O
later	O
restored	O
to	O
exactly	O
the	O
same	O
state	B-Application
.	O
</s>
<s>
In	O
such	O
cases	O
,	O
system	B-Operating_System
images	I-Operating_System
can	O
be	O
used	O
for	O
backup	B-Protocol
.	O
</s>
<s>
Hibernation	O
is	O
an	O
example	O
that	O
uses	O
an	O
image	O
of	O
the	O
entire	O
machine	O
's	O
RAM	B-Architecture
.	O
</s>
<s>
If	O
a	O
system	O
has	O
all	O
its	O
state	B-Application
written	O
to	O
a	O
disk	O
,	O
then	O
a	O
system	B-Operating_System
image	I-Operating_System
can	O
be	O
produced	O
by	O
simply	O
copying	O
that	O
disk	O
to	O
a	O
file	B-Operating_System
elsewhere	O
,	O
often	O
with	O
disk	B-Application
cloning	I-Application
applications	O
.	O
</s>
<s>
On	O
many	O
systems	O
a	O
complete	O
system	B-Operating_System
image	I-Operating_System
cannot	O
be	O
created	O
by	O
a	O
disk	B-Application
cloning	I-Application
program	O
running	O
within	O
that	O
system	O
because	O
information	O
can	O
be	O
held	O
outside	O
of	O
disks	O
and	O
volatile	O
memory	O
,	O
for	O
example	O
in	O
non-volatile	O
memory	O
like	O
boot	O
ROMs	O
.	O
</s>
<s>
A	O
process	B-Operating_System
image	O
is	O
a	O
copy	O
of	O
a	O
given	O
process	B-Operating_System
's	O
state	B-Application
at	O
a	O
given	O
point	O
in	O
time	O
.	O
</s>
<s>
It	O
is	O
often	O
used	O
to	O
create	O
persistence	B-Application
within	O
an	O
otherwise	O
volatile	O
system	O
.	O
</s>
<s>
A	O
common	O
example	O
is	O
a	O
database	B-Application
management	I-Application
system	I-Application
(	O
DBMS	O
)	O
.	O
</s>
<s>
Most	O
DBMS	O
can	O
store	O
the	O
state	B-Application
of	O
its	O
database	O
or	O
databases	B-Application
to	O
a	O
file	B-Operating_System
before	O
being	O
closed	O
down	O
(	O
see	O
database	O
dump	B-General_Concept
)	O
.	O
</s>
<s>
Here	O
,	O
the	O
state	B-Application
of	O
all	O
RAM	B-Architecture
memory	I-Architecture
is	O
stored	O
to	O
disk	O
,	O
the	O
computer	O
is	O
brought	O
into	O
an	O
energy	O
saving	O
mode	O
,	O
then	O
later	O
restored	O
to	O
normal	O
operation	O
.	O
</s>
<s>
Some	O
emulators	B-Application
provide	O
a	O
facility	O
to	O
save	O
an	O
image	O
of	O
the	O
system	O
being	O
emulated	B-Application
.	O
</s>
<s>
Another	O
use	O
is	O
code	B-Operating_System
mobility	I-Operating_System
:	O
a	O
mobile	B-Operating_System
agent	I-Operating_System
can	O
migrate	O
between	O
machines	O
by	O
having	O
its	O
state	B-Application
saved	O
,	O
then	O
copying	O
the	O
data	O
to	O
another	O
machine	O
and	O
restarting	O
there	O
.	O
</s>
<s>
Some	O
programming	O
languages	O
provide	O
a	O
command	O
to	O
take	O
a	O
system	B-Operating_System
image	I-Operating_System
of	O
a	O
program	O
.	O
</s>
<s>
This	O
is	O
normally	O
a	O
standard	O
feature	O
in	O
Smalltalk	B-Application
(	O
inspired	O
by	O
)	O
and	O
Lisp	B-Language
,	O
among	O
other	O
languages	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
Lisp	B-Language
the	O
programmer	O
may	O
load	O
packages	O
or	O
other	O
code	O
into	O
a	O
running	O
Lisp	B-Language
implementation	O
using	O
the	O
read-eval-print	B-Application
loop	I-Application
,	O
which	O
usually	O
compiles	O
the	O
programs	O
.	O
</s>
<s>
Data	O
is	O
loaded	O
into	O
the	O
running	O
Lisp	B-Language
system	O
.	O
</s>
<s>
The	O
programmer	O
may	O
then	O
dump	B-General_Concept
a	O
system	B-Operating_System
image	I-Operating_System
,	O
containing	O
that	O
pre-compiled	O
and	O
possibly	O
customized	O
code	O
—	O
and	O
also	O
all	O
loaded	O
application	O
data	O
.	O
</s>
<s>
This	O
system	B-Operating_System
image	I-Operating_System
can	O
be	O
the	O
form	O
in	O
which	O
executable	O
programs	O
are	O
distributed	O
—	O
this	O
method	O
has	O
often	O
been	O
used	O
by	O
programs	O
(	O
such	O
as	O
TeX	B-Application
and	O
Emacs	B-Application
)	O
largely	O
implemented	O
in	O
Lisp	B-Language
,	O
Smalltalk	B-Application
,	O
or	O
idiosyncratic	O
languages	O
to	O
avoid	O
spending	O
time	O
repeating	O
the	O
same	O
initialization	O
work	O
every	O
time	O
they	O
start	O
up	O
.	O
</s>
<s>
Similar	O
,	O
Lisp	B-Operating_System
Machines	I-Operating_System
were	O
booted	O
from	O
Lisp	B-Language
images	O
,	O
called	O
Worlds	O
.	O
</s>
<s>
The	O
World	O
contains	O
the	O
complete	O
operating	O
system	O
,	O
its	O
applications	O
and	O
its	O
data	O
in	O
a	O
single	O
file	B-Operating_System
.	O
</s>
<s>
Before	O
saving	O
the	O
World	O
,	O
the	O
Lisp	B-Operating_System
Machine	I-Operating_System
operating	O
system	O
could	O
optimize	O
the	O
contents	O
of	O
memory	O
(	O
better	O
memory	O
layout	O
,	O
compacting	O
data	O
structures	O
,	O
sorting	O
data	O
,	O
...	O
)	O
.	O
</s>
<s>
Although	O
its	O
purpose	O
is	O
different	O
,	O
a	O
"	O
system	B-Operating_System
image	I-Operating_System
"	O
is	O
often	O
similar	O
in	O
structure	O
to	O
a	O
core	B-Error_Name
dump	I-Error_Name
.	O
</s>
