<s>
iOS	B-Operating_System
4	I-Operating_System
is	O
the	O
fourth	B-Operating_System
major	I-Operating_System
release	I-Operating_System
of	O
the	O
iOS	B-Application
mobile	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
developed	O
by	O
Apple	O
Inc.	O
,	O
being	O
the	O
successor	O
to	O
iPhone	B-Operating_System
OS	I-Operating_System
3	I-Operating_System
.	O
</s>
<s>
It	O
was	O
announced	O
at	O
the	O
Apple	O
Special	O
Event	O
on	O
April	O
8	O
,	O
2010	O
,	O
and	O
was	O
released	O
on	O
June	O
21	O
,	O
2010	O
.	O
iOS	B-Operating_System
4	I-Operating_System
is	O
the	O
first	O
iOS	B-Application
version	O
issued	O
under	O
the	O
"	O
iOS	B-Application
"	O
rebranding	O
,	O
dropping	O
the	O
"	O
iPhone	B-Operating_System
OS	I-Operating_System
"	O
naming	O
convention	O
of	O
previous	O
versions	O
.	O
</s>
<s>
It	O
was	O
succeeded	O
by	O
iOS	B-Operating_System
5	I-Operating_System
on	O
October	O
12	O
,	O
2011	O
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
introduced	O
folders	O
on	O
the	O
home	O
screen	O
,	O
significantly	O
increasing	O
the	O
number	O
of	O
apps	O
that	O
can	O
be	O
displayed	O
.	O
</s>
<s>
The	O
operating	O
system	O
also	O
added	O
a	O
multitasking	O
feature	O
,	O
letting	O
apps	O
dealing	O
with	O
Internet	B-Application
calling	I-Application
,	O
location	O
and	O
audio	O
playback	O
function	O
in	O
the	O
background	O
,	O
whereas	O
a	O
similar	O
but	O
more	O
restricted	O
"	O
Fast	O
App	O
Switching	O
"	O
technology	O
enabled	O
any	O
app	O
to	O
be	O
left	O
inactive	O
in	O
the	O
background	O
while	O
users	O
switch	O
to	O
other	O
apps	O
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
also	O
added	O
a	O
system-wide	O
spell	B-Application
checking	I-Application
feature	O
,	O
enabled	O
iBooks	B-Application
on	O
iPhone	B-Operating_System
,	O
unified	O
the	O
Mail	B-Operating_System
inbox	O
to	O
combine	O
content	O
from	O
different	O
email	O
providers	O
,	O
and	O
introduced	O
both	O
Game	B-Operating_System
Center	I-Operating_System
for	O
social	O
gaming	O
and	O
FaceTime	B-Operating_System
for	O
video	B-Application
calling	I-Application
.	O
</s>
<s>
The	O
iOS	B-Operating_System
4	I-Operating_System
update	O
introduced	O
performance	O
and	O
battery	O
problems	O
on	O
iPhone	B-Operating_System
3G	I-Operating_System
devices	O
,	O
with	O
Apple	O
investigating	O
the	O
matter	O
and	O
promising	O
then-upcoming	O
updates	O
.	O
</s>
<s>
Around	O
the	O
same	O
time	O
,	O
the	O
release	O
of	O
iPhone	B-Operating_System
4	I-Operating_System
and	O
its	O
subsequent	O
antenna	O
problems	O
made	O
Apple	O
focus	O
on	O
unsuccessfully	O
attempting	O
to	O
patch	O
the	O
issues	O
with	O
software	O
updates	O
.	O
</s>
<s>
This	O
is	O
also	O
the	O
final	O
iOS	B-Application
operating	O
system	O
to	O
have	O
,	O
on	O
iPhones	B-Operating_System
,	O
an	O
iPod	O
app	O
for	O
music	O
and	O
videos	O
;	O
starting	O
with	O
iOS	B-Operating_System
5	I-Operating_System
,	O
iPhones	B-Operating_System
have	O
the	O
same	O
separate	O
Music	O
and	O
Videos	O
apps	O
as	O
do	O
iPod	B-Device
Touch	I-Device
and	O
iPad	B-Device
models	O
.	O
</s>
<s>
iPhone	B-Operating_System
OS	I-Operating_System
4	I-Operating_System
was	O
introduced	O
at	O
the	O
Apple	O
Special	O
Event	O
on	O
April	O
8	O
,	O
2010	O
.	O
</s>
<s>
At	O
the	O
WWDC	O
keynote	O
address	O
on	O
June	O
7	O
,	O
2010	O
,	O
it	O
was	O
renamed	O
to	O
iOS	B-Operating_System
4	I-Operating_System
in	O
order	O
to	O
be	O
more	O
inclusive	O
to	O
the	O
iPod	B-Device
Touch	I-Device
and	O
iPad	B-Device
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
was	O
officially	O
released	O
on	O
June	O
21	O
,	O
2010	O
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
raised	O
the	O
maximum	O
number	O
of	O
home	O
screen	O
apps	O
from	O
180	O
to	O
2,160	O
due	O
to	O
the	O
addition	O
of	O
folders	O
.	O
</s>
<s>
These	O
folders	O
would	O
automatically	O
be	O
named	O
based	O
on	O
the	O
containing	O
apps	O
 '	O
respective	O
App	B-Application
Store	I-Application
category	O
.	O
</s>
<s>
The	O
ability	O
to	O
add	O
custom	O
wallpapers	O
to	O
the	O
home	O
screen	O
was	O
also	O
added	O
,	O
though	O
the	O
feature	O
was	O
notably	O
absent	O
from	O
iPhone	B-Operating_System
3G	I-Operating_System
and	O
the	O
second-generation	O
iPod	B-Device
Touch	I-Device
due	O
to	O
poor	O
performance	O
of	O
icon	O
animations	O
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
introduced	O
multitasking	O
.	O
</s>
<s>
Multitasking	O
was	O
limited	O
to	O
apps	O
dealing	O
with	O
Internet	B-Application
calling	I-Application
,	O
location	O
,	O
and	O
audio	O
playback	O
,	O
while	O
a	O
similar	O
"	O
Fast	O
App	O
Switching	O
"	O
technology	O
meant	O
users	O
could	O
leave	O
an	O
app	O
and	O
enter	O
another	O
,	O
with	O
the	O
original	O
app	O
remaining	O
in	O
the	O
background	O
until	O
the	O
user	O
returns	O
.	O
</s>
<s>
This	O
feature	O
was	O
notably	O
absent	O
from	O
iPhone	B-Operating_System
3G	I-Operating_System
and	O
the	O
second-generation	O
iPod	B-Device
Touch	I-Device
due	O
to	O
performance	O
issues	O
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
introduced	O
a	O
spell	B-Application
checking	I-Application
feature	O
that	O
underlined	O
misspelled	O
words	O
in	O
red	O
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
introduced	O
iPhone	B-Operating_System
and	O
iPod	B-Device
Touch	I-Device
support	O
in	O
iBooks	B-Application
,	O
which	O
was	O
already	O
included	O
on	O
iPad	B-Device
.	O
</s>
<s>
Though	O
not	O
a	O
default	O
app	O
,	O
it	O
was	O
available	O
through	O
App	B-Application
Store	I-Application
.	O
</s>
<s>
The	O
Mail	B-Operating_System
app	O
featured	O
a	O
unified	O
inbox	O
on	O
iOS	B-Operating_System
4	I-Operating_System
,	O
allowing	O
users	O
to	O
see	O
messages	O
from	O
all	O
of	O
their	O
email	O
accounts	O
displayed	O
together	O
in	O
a	O
single	O
inbox	O
.	O
</s>
<s>
It	O
also	O
gained	O
support	O
for	O
MobileMe	B-Application
e-mail	O
aliases	O
and	O
multiple	O
Exchange	B-Operating_System
accounts	O
for	O
business	O
users	O
.	O
</s>
<s>
iOS	O
4.1	O
added	O
a	O
new	O
app	O
called	O
Game	B-Operating_System
Center	I-Operating_System
,	O
an	O
online	O
multiplayer	O
social	O
gaming	O
network	O
,	O
which	O
allows	O
users	O
to	O
invite	O
friends	O
to	O
play	O
games	O
and	O
to	O
compare	O
their	O
scores	O
on	O
a	O
leaderboard	O
.	O
</s>
<s>
It	O
was	O
not	O
available	O
on	O
the	O
iPhone	B-Operating_System
3G	I-Operating_System
.	O
</s>
<s>
iOS	B-Operating_System
4	I-Operating_System
introduced	O
FaceTime	B-Operating_System
,	O
a	O
videotelephony	B-Application
app	O
that	O
uses	O
the	O
device	O
's	O
camera	O
to	O
allow	O
the	O
user	O
to	O
make	O
video	B-Application
calls	I-Application
with	O
other	O
FaceTime	B-Operating_System
users	O
.	O
</s>
<s>
This	O
feature	O
was	O
absent	O
from	O
the	O
iPhone	B-Operating_System
3G	I-Operating_System
,	O
second-generation	O
iPod	B-Device
Touch	I-Device
,	O
iPhone	B-Operating_System
3GS	I-Operating_System
,	O
and	O
third-generation	O
iPod	B-Device
Touch	I-Device
due	O
to	O
the	O
lack	O
of	O
required	O
features	O
,	O
such	O
as	O
a	O
front-facing	O
camera	O
.	O
</s>
<s>
The	O
Safari	B-Application
mobile	I-Application
web	B-Application
browser	I-Application
on	O
iOS	B-Operating_System
4	I-Operating_System
added	O
Bing	B-Application
as	O
a	O
search	O
option	O
in	O
addition	O
to	O
Google	B-Application
and	O
Yahoo	B-Application
!	I-Application
.	O
</s>
<s>
iPhone	B-Operating_System
3G	I-Operating_System
users	O
reported	O
performance	O
and	O
battery	O
issues	O
after	O
upgrading	O
to	O
iOS	B-Operating_System
4	I-Operating_System
.	O
</s>
<s>
In	O
all	O
versions	O
of	O
iOS	B-Operating_System
4	I-Operating_System
,	O
the	O
alarm	O
clock	O
in	O
the	O
clock	O
app	O
had	O
a	O
problem	O
in	O
DST	O
when	O
it	O
would	O
go	O
off	O
an	O
hour	O
too	O
early	O
or	O
too	O
late	O
.	O
</s>
<s>
Upon	O
its	O
release	O
,	O
some	O
iPhone	B-Operating_System
4	I-Operating_System
users	O
reported	O
having	O
technical	O
problems	O
with	O
the	O
phone	O
's	O
antennas	O
.	O
</s>
<s>
The	O
first-generation	B-Operating_System
iPhone	I-Operating_System
and	O
the	O
first-generation	B-Device
iPod	I-Device
Touch	I-Device
cannot	O
run	O
iOS	B-Operating_System
4	I-Operating_System
and	O
above	O
due	O
to	O
hardware	O
limitations	O
,	O
though	O
the	O
iPhone	B-Operating_System
3G	I-Operating_System
did	O
receive	O
iOS	B-Operating_System
4	I-Operating_System
,	O
despite	O
it	O
having	O
the	O
same	O
processor	O
as	O
the	O
iPhone	B-Operating_System
2G	I-Operating_System
.	O
</s>
<s>
iPhone	B-Operating_System
3GS	I-Operating_System
and	O
iPhone	B-Operating_System
4	I-Operating_System
only	O
:	O
</s>
<s>
iPhone	B-Operating_System
4	I-Operating_System
only	O
:	O
</s>
<s>
Exclusive	O
to	O
iPhone	B-Operating_System
3GS	I-Operating_System
,	O
iPhone	B-Operating_System
4	I-Operating_System
,	O
and	O
iPod	B-Device
touch	I-Device
(	O
3rd	O
generation	O
)	O
:	O
</s>
<s>
Adds	O
all	O
features	O
added	O
in	O
iOS	B-Operating_System
4.0	I-Operating_System
for	O
iPhones	B-Operating_System
to	O
the	O
iPad	B-Device
(	O
1st	O
generation	O
)	O
Feature	O
Update4.2.18C1488C148aJasperLast	O
version	O
of	O
iOS	B-Application
to	O
run	O
on	O
iPhone	B-Operating_System
3G	I-Operating_System
and	O
iPod	B-Device
Touch	I-Device
(	O
2nd	O
generation	O
)	O
due	O
to	O
hardware	O
and	O
performance	O
issues	O
.	O
</s>
<s>
Fixes	O
a	O
bug	O
that	O
caused	O
code	O
running	O
as	O
user	O
to	O
gain	O
system	O
privilegesBug	O
Fixes4.3.58L1July	O
25	O
,	O
2011Fixes	O
a	O
bug	O
that	O
allowed	O
an	O
attacker	O
in	O
a	O
privileged	O
network	O
position	O
to	O
capture	O
and/or	O
modify	O
data	O
in	O
SSL/TLS	O
-protected	O
network	O
sessionsBug	O
FixesiPhone	O
4	O
(	O
CDMA	O
)	O
only4.2.58E128UnknownJanuary	O
11	O
,	O
2011Preview	O
release	O
on	O
iPhone	B-Operating_System
4	I-Operating_System
(	O
CDMA	O
)	O
.	O
</s>
<s>
Adds	O
personal	B-Application
Wi-Fi	I-Application
hotspot	I-Application
supportPreview	O
Release4.2.68E200PhoenixJanuary	O
31	O
,	O
2011Initial	O
release	O
on	O
iPhone	B-Operating_System
4	I-Operating_System
(	O
CDMA	O
)	O
,	O
as	O
while	O
4.2.5	O
also	O
came	O
with	O
the	O
device	O
,	O
4.2.6	O
was	O
the	O
first	O
public	O
version	O
.	O
</s>
