<s>
Core	B-Operating_System
Foundation	I-Operating_System
(	O
also	O
called	O
CF	O
)	O
is	O
a	O
C	B-Language
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
written	O
by	O
Apple	O
for	O
its	O
operating	O
systems	O
,	O
and	O
is	O
a	O
mix	O
of	O
low-level	O
routines	O
and	O
wrapper	O
functions	O
.	O
</s>
<s>
Most	O
Core	B-Operating_System
Foundation	I-Operating_System
routines	O
follow	O
a	O
certain	O
naming	O
convention	O
that	O
deal	O
with	O
opaque	O
objects	O
,	O
for	O
example	O
CFDictionaryRef	O
for	O
functions	O
whose	O
names	O
begin	O
with	O
CFDictionary	O
,	O
and	O
these	O
objects	O
are	O
often	O
reference	O
counted	O
(	O
manually	O
)	O
through	O
CFRetain	O
and	O
CFRelease	O
.	O
</s>
<s>
Internally	O
,	O
Core	B-Operating_System
Foundation	I-Operating_System
forms	O
the	O
base	O
of	O
the	O
types	O
in	O
the	O
Objective-C	B-Language
standard	O
library	B-Library
and	O
the	O
Carbon	B-Operating_System
API	I-Operating_System
.	O
</s>
<s>
The	O
most	O
prevalent	O
use	O
of	O
Core	B-Operating_System
Foundation	I-Operating_System
is	O
for	O
passing	O
its	O
own	O
primitive	O
types	O
for	O
data	O
,	O
including	O
raw	O
bytes	B-Application
,	O
Unicode	O
strings	O
,	O
numbers	O
,	O
calendar	O
dates	O
,	O
and	O
UUIDs	O
,	O
as	O
well	O
as	O
collections	O
such	O
as	O
arrays	B-Data_Structure
,	O
sets	O
,	O
and	O
dictionaries	B-Algorithm
,	O
to	O
numerous	O
macOS	B-Application
C	B-Language
routines	O
,	O
primarily	O
those	O
that	O
are	O
GUI-related	O
.	O
</s>
<s>
At	O
the	O
operating	O
system	O
level	O
Core	B-Operating_System
Foundation	I-Operating_System
also	O
provides	O
standardized	O
application	O
preferences	O
management	O
through	O
CFPropertyList	O
,	O
bundle	B-Application
handling	O
,	O
run	O
loops	O
,	O
interprocess	B-Operating_System
communication	I-Operating_System
through	O
CFMachPort	O
and	O
CFNotificationCenter	O
,	O
and	O
a	O
basic	O
graphical	B-Application
user	I-Application
interface	I-Application
message	O
dialog	O
through	O
CFUserNotification	O
.	O
</s>
<s>
Other	O
parts	O
of	O
the	O
API	B-Application
include	O
utility	O
routines	O
and	O
wrappers	O
around	O
existing	O
APIs	B-Application
for	O
ease	O
of	O
use	O
.	O
</s>
<s>
Utility	O
routines	O
perform	O
such	O
actions	O
as	O
file	B-Application
system	I-Application
and	O
network	B-Architecture
I/O	B-General_Concept
through	O
CFReadStream	O
,	O
CFWriteStream	O
,	O
and	O
CFURL	O
and	O
endianness	O
translation	O
(	O
Byte	B-Application
Order	O
Utilities	O
)	O
.	O
</s>
<s>
Some	O
examples	O
of	O
wrapper	O
routines	O
include	O
those	O
for	O
Core	B-Operating_System
Foundation	I-Operating_System
's	O
wrapper	O
routines	O
for	O
Unix	O
sockets	O
,	O
the	O
CFSocket	O
API	B-Application
.	O
</s>
<s>
Some	O
types	O
in	O
Core	B-Operating_System
Foundation	I-Operating_System
are	O
"	O
toll-free	O
bridged	O
"	O
,	O
or	O
interchangeable	O
with	O
a	O
simple	O
cast	O
,	O
with	O
those	O
of	O
their	O
Foundation	B-Operating_System
Kit	I-Operating_System
counterparts	O
.	O
</s>
<s>
For	O
example	O
,	O
one	O
could	O
create	O
a	O
CFDictionaryRef	O
Core	B-Operating_System
Foundation	I-Operating_System
type	O
,	O
and	O
then	O
later	O
simply	O
use	O
a	O
standard	O
C	B-Language
cast	O
to	O
convert	O
it	O
to	O
its	O
Objective-C	B-Language
counterpart	O
,	O
NSDictionary	O
*	O
,	O
and	O
then	O
use	O
the	O
desired	O
Objective-C	B-Language
methods	O
on	O
that	O
object	O
as	O
one	O
normally	O
would	O
.	O
</s>
<s>
Core	B-Operating_System
Foundation	I-Operating_System
has	O
a	O
plug-in	O
model	O
(	O
)	O
that	O
is	O
based	O
on	O
the	O
Microsoft	B-Application
Component	I-Application
Object	I-Application
Model	I-Application
.	O
</s>
<s>
Apple	O
used	O
to	O
release	O
most	O
of	O
CF	O
as	O
an	O
open-source	B-Application
project	O
called	O
CFLite	O
that	O
can	O
be	O
used	O
to	O
write	O
cross-platform	O
applications	O
for	O
macOS	B-Application
,	O
Linux	B-Application
,	O
and	O
Windows	B-Application
.	O
</s>
<s>
A	O
third-party	O
open-source	B-Application
implementation	O
called	O
OpenCFLite	O
extends	O
the	O
Apple	O
CFLite	O
for	O
building	O
on	O
32-bit	B-Application
Windows	I-Application
and	O
Linux	B-Application
environments	O
.	O
</s>
<s>
It	O
is	O
maintained	O
by	O
one	O
of	O
the	O
WebKit	B-Language
developers	O
,	O
but	O
was	O
stalled	O
by	O
2015	O
.	O
</s>
<s>
This	O
version	O
,	O
by	O
its	O
programmer	O
David	O
M	O
.	O
Cotter	O
,	O
supports	O
64-bit	O
systems	O
and	O
has	O
a	O
CFNetwork	O
implementation	O
with	O
LibreSSL-based	O
TLS	O
.	O
</s>
<s>
The	O
Swift	B-Application
Corelib	O
Foundation	O
,	O
a	O
fallback	O
version	O
of	O
the	O
Foundation	B-Operating_System
Kit	I-Operating_System
for	O
the	O
Swift	B-Application
programming	I-Application
language	I-Application
for	O
non-Apple	O
platforms	O
,	O
contains	O
a	O
near-full	O
version	O
of	O
the	O
Core	B-Operating_System
Foundation	I-Operating_System
released	O
under	O
Apache	B-Application
License	I-Application
2.0	I-Application
.	O
</s>
<s>
GNUstep	B-Application
includes	O
a	O
version	O
of	O
the	O
Core	B-Operating_System
Foundation	I-Operating_System
called	O
"	O
libs-corebase	O
"	O
.	O
</s>
