<s>
The	O
Foundation	B-Operating_System
Kit	I-Operating_System
,	O
or	O
just	O
Foundation	O
for	O
short	O
,	O
is	O
an	O
Objective-C	B-Language
framework	B-Architecture
in	O
the	O
OpenStep	B-Operating_System
specification	O
.	O
</s>
<s>
It	O
provides	O
basic	O
classes	O
such	O
as	O
wrapper	O
classes	O
and	O
data	B-General_Concept
structure	I-General_Concept
classes	O
.	O
</s>
<s>
This	O
framework	B-Architecture
uses	O
the	O
prefix	O
NS	O
(	O
for	O
NeXTSTEP	B-Application
)	O
.	O
</s>
<s>
It	O
is	O
also	O
part	O
of	O
Cocoa	B-Operating_System
and	O
of	O
the	O
Swift	B-Application
standard	O
library	O
.	O
</s>
<s>
This	O
class	O
is	O
the	O
most	O
common	O
base	O
class	O
for	O
Objective-C	B-Language
hierarchies	O
and	O
provides	O
standard	O
methods	O
for	O
working	O
with	O
objects	O
by	O
managing	B-General_Concept
the	I-General_Concept
memory	I-General_Concept
associated	O
with	O
them	O
and	O
querying	O
them	O
.	O
</s>
<s>
NSValue	O
is	O
a	O
wrapper	O
class	O
for	O
C	B-Language
data	I-Language
types	I-Language
,	O
and	O
NSNumber	O
is	O
a	O
wrapper	O
class	O
for	O
C	B-Language
number	O
data	O
types	O
such	O
as	O
int	O
,	O
double	O
,	O
and	O
float	O
.	O
</s>
<s>
The	O
data	B-General_Concept
structures	I-General_Concept
in	O
Foundation	B-Operating_System
Kit	I-Operating_System
can	O
only	O
hold	O
objects	O
,	O
not	O
primitive	O
types	O
,	O
so	O
wrappers	O
such	O
as	O
NSValue	O
and	O
NSNumber	O
are	O
used	O
in	O
those	O
data	B-General_Concept
structures	I-General_Concept
.	O
</s>
<s>
The	O
Foundation	B-Operating_System
Kit	I-Operating_System
is	O
part	O
of	O
the	O
macOS	B-Application
Cocoa	B-Operating_System
API	I-Operating_System
.	O
</s>
<s>
Beginning	O
as	O
the	O
successor	O
to	O
OPENSTEP/Mach	O
,	O
this	O
framework	B-Architecture
has	O
deviated	O
from	O
OpenStep	B-Operating_System
compliance	O
,	O
and	O
is	O
in	O
some	O
places	O
incompatible	O
.	O
</s>
<s>
The	O
Foundation	B-Operating_System
Kit	I-Operating_System
is	O
in	O
the	O
iOS	O
Cocoa	B-Operating_System
Touch	I-Operating_System
API	O
.	O
</s>
<s>
This	O
framework	B-Architecture
is	O
based	O
on	O
the	O
macOS	B-Application
Cocoa	B-Operating_System
.	O
</s>
<s>
The	O
Foundation	B-Operating_System
Kit	I-Operating_System
is	O
implemented	O
in	O
GNUstep	B-Application
's	O
Base	O
Package	O
(	O
libs-base	O
)	O
.	O
</s>
<s>
This	O
implementation	O
is	O
mostly	O
comparable	O
(	O
4	O
classes	O
are	O
missing	O
)	O
and	O
aims	O
to	O
be	O
comparable	O
with	O
both	O
the	O
OpenStep	B-Operating_System
API	O
and	O
later	O
macOS	B-Application
additions	O
.	O
</s>
<s>
The	O
Foundation	B-Operating_System
Kit	I-Operating_System
is	O
implemented	O
in	O
,	O
an	O
open-source	O
implementation	O
of	O
Cocoa	B-Operating_System
.	O
</s>
<s>
It	O
is	O
also	O
a	O
part	O
of	O
Darling	B-Language
.	O
</s>
<s>
is	O
an	O
open-source	O
implementation	O
of	O
Foundation	O
that	O
implements	O
Foundation	O
by	O
wrapping	O
Core	B-Operating_System
Foundation	I-Operating_System
,	O
just	O
like	O
in	O
Cocoa	B-Operating_System
,	O
rather	O
than	O
create	O
a	O
separate	O
Foundation	O
from	O
scratch	O
like	O
GNUstep	B-Application
and	O
Cocotron	O
.	O
</s>
<s>
SwiftFoundation	O
(	O
swift-corelibs-foundation	O
)	O
is	O
Apple	O
's	O
open-source	O
Swift	B-Application
implementation	O
of	O
the	O
Foundation	O
API	O
for	O
platforms	O
where	O
there	O
is	O
no	O
Objective-C	B-Language
runtime	O
.	O
</s>
<s>
It	O
also	O
includes	O
an	O
implementation	O
of	O
Core	B-Operating_System
Foundation	I-Operating_System
.	O
</s>
<s>
ApportableFoundation	O
is	O
an	O
implementation	O
of	O
Foundation	B-Operating_System
Kit	I-Operating_System
(	O
Foundation	O
,	O
CoreFoundation	B-Operating_System
,	O
and	O
CFNetwork	O
)	O
based	O
on	O
Apple	O
's	O
CFLite	O
release	O
.	O
</s>
<s>
It	O
works	O
on	O
Android	B-Application
and	O
other	O
Linux	B-Application
systems	O
,	O
and	O
makes	O
up	O
part	O
of	O
the	O
Darling	B-Language
macOS	B-Application
translation	O
layer	O
for	O
Linux	B-Application
.	O
</s>
