<s>
In	O
computing	O
,	O
rebooting	B-Device
is	O
the	O
process	O
by	O
which	O
a	O
running	O
computer	O
system	O
is	O
restarted	O
,	O
either	O
intentionally	O
or	O
unintentionally	O
.	O
</s>
<s>
Reboots	B-Device
can	O
be	O
either	O
a	O
cold	O
reboot	B-Device
(	O
alternatively	O
known	O
as	O
a	O
hard	O
reboot	B-Device
)	O
in	O
which	O
the	O
power	O
to	O
the	O
system	O
is	O
physically	O
turned	O
off	O
and	O
back	O
on	O
again	O
(	O
causing	O
an	O
initial	B-Operating_System
boot	I-Operating_System
of	O
the	O
machine	O
)	O
;	O
or	O
a	O
warm	O
reboot	B-Device
(	O
or	O
soft	O
reboot	B-Device
)	O
in	O
which	O
the	O
system	O
restarts	O
while	O
still	O
powered	O
up	O
.	O
</s>
<s>
The	O
term	O
restart	O
(	O
as	O
a	O
system	O
command	O
)	O
is	O
used	O
to	O
refer	O
to	O
a	O
reboot	B-Device
when	O
the	O
operating	B-General_Concept
system	I-General_Concept
closes	O
all	O
programs	O
and	O
finalizes	O
all	O
pending	O
input	O
and	O
output	O
operations	O
before	O
initiating	O
a	O
soft	O
reboot	B-Device
.	O
</s>
<s>
Early	O
electronic	O
computers	O
(	O
like	O
the	O
IBM	B-Device
1401	I-Device
)	O
had	O
no	O
operating	B-General_Concept
system	I-General_Concept
and	O
little	O
internal	O
memory	O
.	O
</s>
<s>
The	O
input	O
was	O
often	O
a	O
stack	O
of	O
punch	B-Architecture
cards	I-Architecture
or	O
via	O
a	O
Switch	B-Device
Register	I-Device
.	O
</s>
<s>
This	O
process	O
was	O
likened	O
to	O
an	O
old	O
saying	O
,	O
"	O
picking	B-Application
yourself	I-Application
up	I-Application
by	I-Application
the	I-Application
bootstraps	I-Application
"	O
,	O
referring	O
to	O
a	O
horseman	O
who	O
lifts	O
himself	O
off	O
the	O
ground	O
by	O
pulling	O
on	O
the	O
straps	O
of	O
his	O
boots	O
.	O
</s>
<s>
This	O
set	O
of	O
initiating	O
punch	B-Architecture
cards	I-Architecture
was	O
called	O
"	O
bootstrap	O
cards	O
"	O
.	O
</s>
<s>
Thus	O
a	O
cold	B-Application
start	I-Application
was	O
called	O
booting	B-Operating_System
the	O
computer	O
up	O
.	O
</s>
<s>
If	O
the	O
computer	O
crashed	B-General_Concept
,	O
it	O
was	O
rebooted	O
.	O
</s>
<s>
The	O
boot	B-Operating_System
reference	O
carried	O
over	O
to	O
all	O
subsequent	O
types	O
of	O
computers	O
.	O
</s>
<s>
For	O
IBM	O
PC	O
compatible	O
computers	O
,	O
a	O
cold	B-Operating_System
boot	I-Operating_System
is	O
a	O
boot	B-Operating_System
process	I-Operating_System
in	O
which	O
the	O
computer	O
starts	O
from	O
a	O
powerless	O
state	O
,	O
in	O
which	O
the	O
system	O
performs	O
a	O
power-on	B-Device
self-test	I-Device
(	O
POST	O
)	O
.	O
</s>
<s>
Both	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
third-party	O
software	O
can	O
initiate	O
a	O
cold	B-Operating_System
boot	I-Operating_System
;	O
the	O
restart	O
command	O
in	O
Windows	O
9x	O
initiates	O
a	O
cold	O
reboot	B-Device
,	O
unless	O
Shift	O
key	O
is	O
held	O
.	O
</s>
<s>
A	O
warm	O
boot	B-Operating_System
is	O
initiated	O
by	O
the	O
BIOS	B-Operating_System
,	O
either	O
as	O
a	O
result	O
of	O
the	O
Control-Alt-Delete	B-Device
key	O
combination	O
or	O
directly	O
through	O
BIOS	B-Operating_System
interrupt	O
INT	B-Device
19h	O
.	O
</s>
<s>
Malware	O
may	O
prevent	O
or	O
subvert	O
a	O
warm	O
boot	B-Operating_System
by	O
intercepting	O
the	O
Ctrl	O
+	O
Alt	O
+	O
Delete	O
key	O
combination	O
and	O
prevent	O
it	O
from	O
reaching	O
BIOS	B-Operating_System
.	O
</s>
<s>
The	O
Windows	B-Device
NT	I-Device
family	I-Device
of	O
operating	B-General_Concept
systems	I-General_Concept
also	O
does	O
the	O
same	O
and	O
reserves	O
the	O
key	O
combination	O
for	O
its	O
own	O
use	O
.	O
</s>
<s>
The	O
Linux	B-Application
family	O
of	O
operating	B-General_Concept
systems	I-General_Concept
supports	O
an	O
alternative	O
to	O
warm	O
boot	B-Operating_System
;	O
the	O
Linux	B-Application
kernel	O
has	O
optional	O
support	O
for	O
kexec	B-Application
,	O
a	O
system	B-Operating_System
call	I-Operating_System
which	O
transfers	O
execution	O
to	O
a	O
new	O
kernel	O
and	O
skips	O
hardware	O
or	O
firmware	O
reset	B-General_Concept
.	O
</s>
<s>
The	O
kernel	O
being	O
executed	O
does	O
not	O
have	O
to	O
be	O
a	O
Linux	B-Application
kernel	O
.	O
</s>
<s>
Outside	O
the	O
domain	O
of	O
IBM	O
PC	O
compatible	O
computers	O
,	O
the	O
types	O
of	O
boot	B-Operating_System
may	O
not	O
be	O
as	O
clear	O
.	O
</s>
<s>
According	O
to	O
Sue	O
Loh	O
of	O
Windows	B-Operating_System
CE	I-Operating_System
Base	O
Team	O
,	O
Windows	B-Operating_System
CE	I-Operating_System
devices	O
support	O
three	O
types	O
of	O
boots	O
:	O
Warm	O
,	O
cold	O
and	O
clean	O
.	O
</s>
<s>
A	O
warm	O
boot	B-Operating_System
discards	O
program	O
memory	O
.	O
</s>
<s>
A	O
cold	B-Operating_System
boot	I-Operating_System
additionally	O
discards	O
storage	O
memory	O
(	O
also	O
known	O
as	O
the	O
"	O
object	O
store	O
"	O
)	O
,	O
while	O
a	O
clean	O
boot	B-Operating_System
erases	O
all''	O
forms	O
of	O
memory	O
storage	O
from	O
the	O
device	O
.	O
</s>
<s>
However	O
,	O
since	O
these	O
areas	O
do	O
not	O
exist	O
on	O
all	O
Windows	B-Operating_System
CE	I-Operating_System
devices	O
,	O
users	O
are	O
only	O
concerned	O
with	O
two	O
forms	O
of	O
reboot	B-Device
:	O
one	O
that	O
resets	B-General_Concept
the	O
volatile	O
memory	O
and	O
one	O
that	O
wipes	O
the	O
device	O
clean	O
and	O
restores	O
factory	O
settings	O
.	O
</s>
<s>
For	O
example	O
,	O
for	O
a	O
Windows	O
Mobile	O
5.0	O
device	O
,	O
the	O
former	O
is	O
a	O
cold	B-Operating_System
boot	I-Operating_System
and	O
the	O
latter	O
is	O
a	O
clean	O
boot	B-Operating_System
.	O
</s>
<s>
A	O
hard	O
reboot	B-Device
means	O
that	O
the	O
system	O
is	O
not	O
shut	O
down	O
in	O
an	O
orderly	O
manner	O
,	O
skipping	O
file	O
system	O
synchronisation	O
and	O
other	O
activities	O
that	O
would	O
occur	O
on	O
an	O
orderly	O
shutdown	O
.	O
</s>
<s>
This	O
can	O
be	O
achieved	O
by	O
either	O
applying	O
a	O
reset	B-General_Concept
,	O
by	O
cycling	O
power	O
,	O
by	O
issuing	O
the	O
command	O
in	O
most	O
Unix-like	B-Operating_System
systems	I-Operating_System
,	O
or	O
by	O
triggering	O
a	O
kernel	B-Operating_System
panic	I-Operating_System
.	O
</s>
<s>
The	O
term	O
"	O
restart	O
"	O
is	O
used	O
by	O
the	O
Microsoft	B-Application
Windows	I-Application
and	O
Linux	B-Application
families	O
of	O
operating	B-General_Concept
systems	I-General_Concept
to	O
denote	O
an	O
operating	O
system-assisted	O
reboot	B-Device
.	O
</s>
<s>
In	O
a	O
restart	O
,	O
the	O
operating	B-General_Concept
system	I-General_Concept
ensures	O
that	O
all	O
pending	O
I/O	O
operations	O
are	O
gracefully	O
ended	O
before	O
commencing	O
a	O
reboot	B-Device
.	O
</s>
<s>
Users	O
may	O
deliberately	O
initiate	O
a	O
reboot	B-Device
.	O
</s>
<s>
Rationale	O
for	O
such	O
action	O
may	O
include:Troubleshooting	O
:	O
Rebooting	B-Device
may	O
be	O
used	O
by	O
users	O
,	O
support	O
staff	O
or	O
system	O
administrators	O
as	O
a	O
technique	O
to	O
work	O
around	O
bugs	O
in	O
software	O
,	O
for	O
example	O
memory	B-Error_Name
leaks	I-Error_Name
or	O
processes	O
that	O
hog	B-Algorithm
resources	O
to	O
the	O
detriment	O
of	O
the	O
overall	O
system	O
,	O
or	O
to	O
terminate	O
malware	O
.	O
</s>
<s>
While	O
this	O
approach	O
does	O
not	O
address	O
the	O
root	O
cause	O
of	O
the	O
issue	O
,	O
resetting	O
a	O
system	O
back	O
to	O
a	O
good	O
,	O
known	O
state	O
may	O
allow	O
it	O
to	O
be	O
used	O
again	O
for	O
some	O
period	O
until	O
the	O
issue	O
next	O
occurs.Switching	O
operating	B-General_Concept
systems	I-General_Concept
:	O
On	O
a	O
multi-boot	B-Operating_System
system	I-Operating_System
without	O
a	O
hypervisor	B-Operating_System
,	O
a	O
reboot	B-Device
is	O
required	O
to	O
switch	O
between	O
installed	O
operating	O
systems.Offensive	O
:	O
As	O
stated	O
earlier	O
,	O
components	O
lose	O
power	O
during	O
a	O
cold	O
reboot	B-Device
;	O
therefore	O
,	O
components	O
such	O
as	O
RAM	B-Architecture
that	O
require	O
power	O
lose	O
the	O
data	O
they	O
hold	O
.	O
</s>
<s>
However	O
,	O
in	O
a	O
cold	B-Operating_System
boot	I-Operating_System
attack	O
,	O
special	O
configurations	O
may	O
allow	O
for	O
part	O
of	O
the	O
system	O
state	O
,	O
like	O
a	O
RAM	B-Architecture
disk	O
,	O
to	O
be	O
preserved	O
through	O
the	O
reboot	B-Device
.	O
</s>
<s>
The	O
means	O
of	O
performing	O
a	O
deliberate	O
reboot	B-Device
also	O
vary	O
and	O
may	O
include:Manual	O
,	O
hardware-based	O
:	O
A	O
power	O
switch	O
or	O
reset	B-Application
button	I-Application
can	O
cause	O
the	O
system	O
to	O
reboot	B-Device
.	O
</s>
<s>
Doing	O
so	O
,	O
however	O
,	O
may	O
cause	O
the	O
loss	O
of	O
all	O
unsaved	O
data.Manual	O
,	O
software-based	O
:	O
Computer	O
software	O
and	O
operating	B-General_Concept
system	I-General_Concept
can	O
trigger	O
a	O
reboot	B-Device
as	O
well	O
;	O
more	O
specifically	O
,	O
Microsoft	B-Application
Windows	I-Application
operating	I-Application
systems	I-Application
are	O
outfitted	O
with	O
a	O
restart	O
command	O
that	O
closes	O
open	O
programs	O
and	O
eliminates	O
data	O
loss	O
due	O
to	O
reboot.Automated	O
:	O
'''	O
Software	O
can	O
be	O
scheduled	O
to	O
run	O
at	O
a	O
certain	O
time	O
and	O
date	O
;	O
therefore	O
,	O
it	O
is	O
possible	O
to	O
schedule	O
a	O
reboot	B-Device
.	O
</s>
<s>
Unexpected	O
loss	O
of	O
power	O
for	O
any	O
reason	O
(	O
including	O
power	O
outage	O
,	O
power	O
supply	O
failure	O
or	O
depletion	O
of	O
battery	O
on	O
a	O
mobile	O
device	O
)	O
forces	O
the	O
system	O
user	O
to	O
perform	O
a	O
cold	B-Operating_System
boot	I-Operating_System
once	O
the	O
power	O
is	O
restored	O
.	O
</s>
<s>
Some	O
BIOSes	O
have	O
an	O
option	O
to	O
automatically	O
boot	B-Operating_System
the	O
system	O
after	O
a	O
power	O
failure	O
.	O
</s>
<s>
"	O
Random	B-Operating_System
reboot	I-Operating_System
"	O
is	O
a	O
non-technical	O
term	O
referring	O
to	O
an	O
unintended	O
(	O
and	O
often	O
undesired	O
)	O
reboot	B-Device
following	O
a	O
system	B-General_Concept
crash	I-General_Concept
,	O
whose	O
root	O
cause	O
may	O
not	O
immediately	O
be	O
evident	O
to	O
the	O
user	O
.	O
</s>
<s>
Such	O
crashes	B-General_Concept
may	O
occur	O
due	O
to	O
a	O
multitude	O
of	O
software	O
and	O
hardware	O
problems	O
,	O
such	O
as	O
triple	B-Error_Name
faults	I-Error_Name
.	O
</s>
<s>
They	O
are	O
generally	O
symptomatic	O
of	O
an	O
error	O
in	O
ring	B-Operating_System
0	I-Operating_System
that	O
is	O
not	O
trapped	O
by	O
an	O
error	B-General_Concept
handler	I-General_Concept
in	O
an	O
operating	B-General_Concept
system	I-General_Concept
or	O
a	O
hardware-triggered	O
non-maskable	B-General_Concept
interrupt	I-General_Concept
.	O
</s>
<s>
Systems	O
may	O
be	O
configured	O
to	O
reboot	B-Device
automatically	O
after	O
a	O
power	O
failure	O
,	O
or	O
a	O
fatal	B-Error_Name
system	I-Error_Name
error	I-Error_Name
or	O
kernel	B-Operating_System
panic	I-Operating_System
.	O
</s>
<s>
The	O
method	O
by	O
which	O
this	O
is	O
done	O
varies	O
depending	O
on	O
whether	O
the	O
reboot	B-Device
can	O
be	O
handled	O
via	O
software	O
or	O
must	O
be	O
handled	O
at	O
the	O
firmware	O
or	O
hardware	O
level	O
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
in	O
the	O
Windows	B-Device
NT	I-Device
family	I-Device
(	O
from	O
Windows	B-Device
NT	I-Device
3.1	I-Device
through	O
Windows	B-Device
7	I-Device
)	O
have	O
an	O
option	O
to	O
modify	O
the	O
behavior	O
of	O
the	O
error	B-General_Concept
handler	I-General_Concept
so	O
that	O
a	O
computer	O
immediately	O
restarts	O
rather	O
than	O
displaying	O
a	O
Blue	O
Screen	O
of	O
Death	O
(	O
BSOD	O
)	O
error	O
message	O
.	O
</s>
<s>
The	O
introduction	O
of	O
advanced	B-Device
power	I-Device
management	I-Device
allowed	O
operating	B-General_Concept
systems	I-General_Concept
greater	O
control	O
of	O
hardware	O
power	O
management	O
features	O
.	O
</s>
<s>
With	O
Advanced	B-Device
Configuration	I-Device
and	I-Device
Power	I-Device
Interface	I-Device
(	O
ACPI	B-Device
)	O
,	O
newer	O
operating	B-General_Concept
systems	I-General_Concept
are	O
able	O
to	O
manage	O
different	O
power	O
states	O
and	O
thereby	O
sleep	O
and/or	O
hibernate	O
.	O
</s>
<s>
While	O
hibernation	O
also	O
involves	O
turning	O
a	O
system	O
off	O
then	O
subsequently	O
back	O
on	O
again	O
,	O
the	O
operating	B-General_Concept
system	I-General_Concept
does	O
not	O
start	O
from	O
scratch	O
,	O
thereby	O
differentiating	O
this	O
process	O
from	O
rebooting	B-Device
.	O
</s>
<s>
A	O
reboot	B-Device
may	O
be	O
simulated	O
by	O
software	O
running	O
on	O
an	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
For	O
example	O
:	O
the	O
Sysinternals	O
BlueScreen	O
utility	O
,	O
which	O
is	O
used	O
for	O
pranking	O
;	O
or	O
some	O
modes	O
of	O
the	O
XScreenSaver	B-General_Concept
"	O
hack	O
"	O
,	O
for	O
entertainment	O
(	O
albeit	O
possibly	O
concerning	O
at	O
first	O
glance	O
)	O
.	O
</s>
<s>
Malware	O
may	O
also	O
simulate	O
a	O
reboot	B-Device
,	O
and	O
thereby	O
deceive	O
a	O
computer	O
user	O
for	O
some	O
nefarious	O
purpose	O
.	O
</s>
<s>
As	O
part	O
of	O
the	O
sequencing	O
process	O
,	O
it	O
will	O
detect	O
when	O
an	O
installer	O
requires	O
a	O
reboot	B-Device
,	O
interrupt	O
the	O
triggered	O
reboot	B-Device
,	O
and	O
instead	O
simulate	O
the	O
required	O
reboot	B-Device
by	O
restarting	O
services	O
and	O
loading/unloading	O
libraries	O
.	O
</s>
<s>
Windows	B-Application
8	I-Application
&	O
10	B-Operating_System
enable	O
(	O
by	O
default	O
)	O
a	O
hibernation-like	O
"	O
Fast	O
Startup	O
"	O
(	O
a.k.a.	O
</s>
<s>
"	O
Fast	O
Boot	B-Operating_System
"	O
)	O
which	O
can	O
cause	O
problems	O
(	O
including	O
confusion	O
)	O
for	O
users	O
accustomed	O
to	O
turning	O
off	O
computers	O
to	O
(	O
cold	O
)	O
reboot	B-Device
them	O
.	O
</s>
