<s>
Cocoa	B-Operating_System
Touch	I-Operating_System
is	O
the	O
application	O
development	O
environment	O
for	O
building	O
software	O
programs	O
to	O
run	O
on	O
iOS	B-Application
for	O
the	O
iPhone	B-Device
and	O
iPod	B-Device
Touch	I-Device
,	O
iPadOS	B-Operating_System
for	O
the	O
iPad	B-Device
,	O
watchOS	B-Device
for	O
the	O
Apple	B-Device
Watch	I-Device
,	O
and	O
tvOS	B-Operating_System
for	O
the	O
Apple	B-Device
TV	I-Device
,	O
from	O
Apple	O
Inc	O
.	O
</s>
<s>
Cocoa	B-Operating_System
Touch	I-Operating_System
provides	O
an	O
abstraction	B-Architecture
layer	I-Architecture
of	O
iOS	B-Application
,	O
the	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
iPhone	B-Device
,	O
iPod	B-Device
Touch	I-Device
,	O
and	O
iPad	B-Device
.	O
</s>
<s>
Cocoa	B-Operating_System
Touch	I-Operating_System
is	O
based	O
on	O
the	O
macOS	B-Application
Cocoa	B-Operating_System
API	I-Operating_System
toolset	O
and	O
,	O
like	O
it	O
,	O
is	O
primarily	O
written	O
in	O
the	O
Objective-C	B-Language
language	O
.	O
</s>
<s>
Cocoa	B-Operating_System
Touch	I-Operating_System
allows	O
the	O
use	O
of	O
hardware	O
and	O
features	O
that	O
are	O
not	O
found	O
in	O
macOS	B-Application
computers	O
and	O
are	O
thus	O
unique	O
to	O
the	O
iOS	B-Application
range	O
of	O
devices	O
.	O
</s>
<s>
Just	O
like	O
Cocoa	B-Operating_System
,	O
Cocoa	B-Operating_System
Touch	I-Operating_System
follows	O
a	O
Model	O
–	O
View	O
–	O
Controller	O
(	O
MVC	O
)	O
software	O
architecture	O
.	O
</s>
<s>
Cocoa	B-Operating_System
Touch	I-Operating_System
contains	O
a	O
different	O
set	O
of	O
graphical	O
control	O
elements	O
from	O
Cocoa	B-Operating_System
.	O
</s>
<s>
Tools	O
for	O
developing	O
applications	O
based	O
on	O
Cocoa	B-Operating_System
Touch	I-Operating_System
are	O
included	O
in	O
the	O
iOS	B-Operating_System
SDK	I-Operating_System
.	O
</s>
<s>
iOS	B-Application
,	O
watchOS	B-Device
,	O
and	O
tvOS	B-Operating_System
technologies	O
can	O
be	O
seen	O
as	O
a	O
set	O
of	O
layers	O
,	O
with	O
Cocoa	B-Operating_System
Touch	I-Operating_System
at	O
the	O
highest	O
level	O
and	O
the	O
Core	O
OS/kernel	O
at	O
the	O
bottom	O
.	O
</s>
<s>
A	O
hierarchical	O
view	O
of	O
the	O
iOS	B-Application
,	O
watchOS	B-Device
,	O
and	O
tvOS	B-Operating_System
technologies	O
can	O
be	O
shown	O
as	O
follows	O
:	O
</s>
<s>
Some	O
of	O
the	O
main	O
features	O
and	O
technologies	O
of	O
Cocoa	B-Operating_System
Touch	I-Operating_System
are	O
:	O
</s>
<s>
Cocoa	B-Operating_System
Touch	I-Operating_System
provides	O
the	O
key	O
frameworks	O
for	O
developing	O
applications	O
on	O
devices	O
running	O
iOS	B-Application
.	O
</s>
<s>
Microsoft	O
's	O
WinObjC	O
,	O
the	O
GNUstep-based	O
iOS	B-Application
bridge	O
for	O
the	O
Universal	B-Device
Windows	I-Device
Platform	I-Device
,	O
contains	O
a	O
working	O
implementation	O
of	O
Cocoa	B-Operating_System
Touch	I-Operating_System
frameworks	O
like	O
Foundation	O
,	O
UIKit	B-Operating_System
,	O
and	O
MapKit	O
released	O
under	O
the	B-License
MIT	I-License
License	I-License
.	O
</s>
<s>
One	O
of	O
the	O
UIKit	B-Operating_System
implementations	O
is	O
based	O
on	O
XAML	B-Device
.	O
</s>
<s>
Various	O
efforts	O
have	O
tried	O
to	O
bring	O
UIKit	B-Operating_System
,	O
the	O
modified	O
AppKit	B-Operating_System
from	O
Cocoa	B-Operating_System
Touch	I-Operating_System
,	O
to	O
macOS	B-Application
:	O
</s>
<s>
Chameleon	O
is	O
a	O
port	O
of	O
UIKit	B-Operating_System
to	O
macOS	B-Application
from	O
2014	O
.	O
</s>
<s>
ZeeZide	O
's	O
UXKit	O
is	O
a	O
more	O
recent	O
port	O
of	O
UIKit	B-Operating_System
to	O
macOS	B-Application
.	O
</s>
<s>
It	O
exists	O
a	O
layer	O
above	O
AppKit	B-Operating_System
and	O
UIKit	B-Operating_System
.	O
</s>
<s>
Apple	O
used	O
a	O
"	O
UXKit	O
"	O
private	O
framework	B-Architecture
for	O
a	O
2015	O
version	O
of	O
Photos.app	O
.	O
</s>
<s>
Apple	O
made	O
the	O
bridge	O
more	O
official	O
with	O
the	O
"	O
iosMac	O
"	O
or	O
"	O
Marzipan	O
"	O
project	O
in	O
2018	O
,	O
which	O
put	O
an	O
"	O
iOSSupport	O
"	O
directory	O
full	O
of	O
iOS	B-Application
frameworks	O
in	O
macOS	B-Device
Mojave	I-Device
.	O
</s>
