<s>
Windows	B-Language
UI	I-Language
Library	I-Language
(	O
WinUI	B-Language
codenamed	O
"	O
Jupiter	O
"	O
,	O
and	O
also	O
known	O
as	O
UWP	B-Language
XAML	I-Language
and	O
WinRT	B-Language
XAML	I-Language
)	O
is	O
a	O
user	B-Application
interface	I-Application
API	B-General_Concept
that	O
is	O
part	O
of	O
the	O
Windows	O
Runtime	O
programming	O
model	O
that	O
forms	O
the	O
backbone	O
of	O
Universal	O
Windows	O
Platform	O
apps	O
(	O
formerly	O
known	O
as	O
Metro-style	O
or	O
Immersive	O
)	O
for	O
the	O
Windows	B-Application
8	I-Application
,	O
Windows	B-Device
8.1	I-Device
,	O
Windows	B-Operating_System
10	I-Operating_System
and	O
Windows	B-Protocol
Phone	I-Protocol
8.1	I-Protocol
operating	O
systems	O
.	O
</s>
<s>
It	O
enables	O
declaring	O
user	B-Application
interfaces	I-Application
using	O
Extensible	B-Device
Application	I-Device
Markup	I-Device
Language	I-Device
(	O
XAML	B-Device
)	O
technology	O
.	O
</s>
<s>
WinUI	B-Language
is	O
one	O
of	O
the	O
multiple	O
UI	O
frameworks	O
provided	O
built-in	O
for	O
the	O
Windows	O
Runtime	O
;	O
the	O
others	O
being	O
HTML5	B-Application
(	O
e.g.	O
,	O
via	O
WinJS	B-Language
)	O
and	O
DirectX	B-Application
.	O
</s>
<s>
WinUI	B-Language
3	I-Language
decouples	O
WinRT	B-Language
XAML	I-Language
from	O
the	O
operating	O
system	O
as	O
a	O
separate	O
package	O
to	O
be	O
updated	O
quickly	O
and	O
make	O
new	O
features	O
work	O
on	O
older	O
versions	O
of	O
Windows	O
.	O
</s>
<s>
It	O
is	O
part	O
of	O
Windows	B-Application
App	I-Application
SDK	I-Application
(	O
codenamed	O
"	O
Project	B-Application
Reunion	I-Application
"	O
)	O
,	O
a	O
Microsoft	O
effort	O
to	O
reconcile	O
the	O
Windows	O
desktop	O
(	O
Win32	O
)	O
and	O
the	O
UWP	O
low	O
IL	O
app	O
model	O
.	O
</s>
<s>
Up	O
to	O
Windows	O
Phone	O
8.0	O
WinRT	B-Language
XAML	I-Language
was	O
not	O
supported	O
and	O
XAML	B-Device
applications	O
were	O
based	O
on	O
Silverlight	B-Application
XAML	B-Device
and	O
deployed	O
in	O
XAP	B-Application
format	O
.	O
</s>
<s>
In	O
Windows	B-Protocol
Phone	I-Protocol
8.1	I-Protocol
WinRT	B-Language
XAML	I-Language
is	O
available	O
along	O
with	O
improved	O
Windows	O
Runtime	O
support	O
.	O
</s>
<s>
This	O
convergence	O
between	O
platforms	O
enable	O
Universal	O
apps	O
that	O
can	O
target	O
both	O
Windows	B-Device
8.1	I-Device
and	O
Windows	B-Protocol
Phone	I-Protocol
8.1	I-Protocol
while	O
sharing	O
most	O
of	O
the	O
code	O
,	O
including	O
user	B-Application
interface	I-Application
.	O
</s>
<s>
WinUI	B-Language
is	O
related	O
to	O
Windows	B-Device
Presentation	I-Device
Foundation	I-Device
(	O
WPF	O
)	O
and	O
Silverlight	B-Application
(	O
WPF/E	B-Application
)	O
—	O
similar	O
XAML-based	O
UI	O
frameworks	O
used	O
for	O
desktop	O
applications	O
and	O
portable	O
applications	O
respectively	O
.	O
</s>
<s>
WinUI	B-Language
uses	O
a	O
lot	O
of	O
the	O
same	O
names	O
for	O
its	O
APIs	B-General_Concept
as	O
both	O
of	O
these	O
older	O
technologies	O
—	O
especially	O
Silverlight	B-Application
,	O
but	O
its	O
use	O
is	O
limited	O
to	O
the	O
Windows	O
(	O
specifically	O
Windows	B-Application
8	I-Application
and	O
later	O
)	O
as	O
with	O
WPF	O
.	O
</s>
<s>
The	O
major	O
difference	O
is	O
that	O
WPF	O
and	O
Silverlight	B-Application
are	O
written	O
in	O
C#	B-Application
and	O
require	O
using	O
.NET	B-Language
languages	I-Language
such	O
as	O
C#	B-Application
or	O
Visual	B-Language
Basic	I-Language
,	O
while	O
WinRT	B-Language
XAML	I-Language
is	O
part	O
of	O
the	O
Windows	O
Runtime	O
,	O
written	O
in	O
C++	B-Language
and	O
available	O
to	O
native	B-Language
code	I-Language
,	O
and	O
has	O
tools	O
for	O
development	O
,	O
with	O
C++	B-Language
/CX	I-Language
or	O
C++	B-Language
/WinRT	I-Language
.	O
</s>
