<s>
C++	B-Language
/WinRT	I-Language
is	O
a	O
C++	B-Language
library	O
for	O
Microsoft	O
's	O
Windows	O
Runtime	O
platform	O
,	O
designed	O
to	O
provide	O
access	O
to	O
modern	O
Windows	B-Library
APIs	I-Library
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
is	O
provided	O
as	O
a	O
standard	O
C++17	O
header	O
file	O
library	O
,	O
unlike	O
C++	B-Language
/CX	I-Language
,	O
which	O
is	O
an	O
extension	O
to	O
C++	B-Language
and	O
requires	O
a	O
recent	O
version	O
of	O
Microsoft	B-Application
Visual	I-Application
C++	I-Application
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
was	O
introduced	O
as	O
part	O
of	O
the	O
Microsoft	B-Application
Windows	I-Application
SDK	I-Application
in	O
version	O
10.0.17134.0	O
(	O
Windows	O
10	O
,	O
version	O
1803	O
)	O
and	O
is	O
a	O
component	O
of	O
Windows	B-Application
App	I-Application
SDK	I-Application
(	O
formerly	O
known	O
as	O
Project	B-Application
Reunion	I-Application
)	O
.	O
</s>
<s>
Microsoft	B-Application
Visual	I-Application
Studio	I-Application
support	O
for	O
C++	B-Language
/WinRT	I-Language
is	O
provided	O
by	O
an	O
officially-supported	O
extension	O
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
was	O
originally	O
released	O
in	O
2015	O
by	O
Kenny	O
Kerr	O
,	O
who	O
shortly	O
afterward	O
joined	O
Microsoft	O
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
is	O
now	O
Microsoft	O
's	O
recommended	O
replacement	O
for	O
both	O
the	O
Windows	O
Runtime	O
C++	B-Language
Template	O
Library	O
(	O
WRL	O
)	O
,	O
and	O
for	O
C++	B-Language
/CX	I-Language
.	O
</s>
<s>
Microsoft	O
's	O
Windows	O
Runtime	O
is	O
based	O
on	O
Component	B-Application
Object	I-Application
Model	I-Application
(	O
COM	O
)	O
APIs	B-General_Concept
,	O
and	O
is	O
designed	O
to	O
be	O
accessed	O
through	O
language	O
projections	O
.	O
</s>
<s>
For	O
C++	B-Language
developers	O
,	O
C++	B-Language
/WinRT	I-Language
is	O
the	O
officially	O
supported	O
,	O
modern	O
C++	B-Language
language	I-Language
projection	O
.	O
</s>
<s>
As	O
of	O
version	O
10.0.17134.0	O
(	O
Windows	O
10	O
,	O
version	O
1803	O
)	O
,	O
the	O
Microsoft	B-Application
Windows	I-Application
SDK	I-Application
contains	O
a	O
header-file-based	O
standard	O
C++	B-Language
library	O
for	O
consuming	O
first-party	O
Windows	B-Library
APIs	I-Library
(	O
that	O
is	O
,	O
Windows	O
Runtime	O
APIs	B-General_Concept
in	O
Windows	O
namespaces	O
)	O
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
also	O
ships	O
with	O
the	O
cppwinrt.exe	O
tool	O
,	O
which	O
can	O
be	O
pointed	O
at	O
a	O
Windows	O
Runtime	O
metadata	O
(	O
.winmd	O
)	O
file	O
to	O
generate	O
a	O
header-file-based	O
standard	O
C++	B-Language
library	O
that	O
projects	O
the	O
APIs	B-General_Concept
described	O
in	O
the	O
metadata	O
for	O
consumption	O
from	O
C++	B-Language
/WinRT	I-Language
code	O
.	O
</s>
<s>
Windows	O
Runtime	O
metadata	O
(	O
.winmd	O
)	O
files	O
provide	O
a	O
canonical	O
way	O
of	O
describing	O
a	O
Windows	O
Runtime	O
API	B-General_Concept
surface	O
.	O
</s>
<s>
With	O
C++	B-Language
/WinRT	I-Language
,	O
users	O
can	O
also	O
implement	O
their	O
own	O
runtime	O
classes	O
using	O
standard	O
C++	B-Language
,	O
without	O
resorting	O
to	O
COM-style	O
programming	O
.	O
</s>
<s>
Alternatively	O
,	O
users	O
can	O
just	O
implement	O
interfaces	O
by	O
deriving	O
from	O
a	O
base	O
class	O
that	O
's	O
part	O
of	O
the	O
C++	B-Language
/WinRT	I-Language
header	O
library	O
.	O
</s>
<s>
These	O
techniques	O
employ	O
the	O
curiously	B-Language
recurring	I-Language
template	I-Language
pattern	I-Language
for	O
function-calling	O
via	O
static	O
dispatch	O
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
makes	O
use	O
of	O
a	O
host	O
of	O
modern	O
ISO	O
C++11	O
(	O
and	O
later	O
)	O
language	O
features	O
to	O
increase	O
productivity	O
and	O
run-time	O
performance	O
;	O
these	O
features	O
were	O
not	O
available	O
when	O
WinRT	O
's	O
predecessors	O
(	O
and	O
C++	B-Language
/CX	I-Language
)	O
were	O
designed	O
.	O
</s>
<s>
Standard	O
C++	B-Language
data	O
types	O
,	O
algorithms	O
,	O
and	O
keywords	O
are	O
used	O
with	O
C++	B-Language
/WinRT	I-Language
;	O
however	O
,	O
the	O
projection	O
also	O
has	O
its	O
own	O
custom	O
data	O
types	O
.	O
</s>
<s>
C++	B-Language
/WinRT	I-Language
produces	O
smaller	O
binaries	O
than	O
other	O
language	O
options	O
for	O
the	O
Windows	O
Runtime	O
.	O
</s>
<s>
Design	O
and	O
development	O
of	O
C++	B-Language
/WinRT	I-Language
was	O
begun	O
in	O
2014	O
by	O
the	O
then-independent	O
software	O
developer	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
the	O
prevailing	O
way	O
for	O
developers	O
to	O
call	O
Windows	O
Runtime	O
APIs	B-General_Concept
using	O
C++	B-Language
was	O
with	O
the	O
C++	B-Language
/CX	I-Language
language	O
projection	O
.	O
</s>
<s>
C++	B-Language
/CX	I-Language
adds	O
non-standard	O
extensions	O
to	O
the	O
C++	B-Language
language	I-Language
,	O
such	O
as	O
the	O
ref	O
new	O
and	O
^	O
(	O
hat	O
)	O
notation	O
inherited	O
from	O
C++	B-Language
/CLI	O
.	O
</s>
<s>
It	O
had	O
n't	O
been	O
fully	O
appreciated	O
then	O
that	O
advances	O
in	O
ISO	O
C++	B-Language
language	I-Language
features	O
meant	O
that	O
it	O
had	O
become	O
possible	O
to	O
design	O
a	O
Windows	O
Runtime	O
language	O
projection	O
for	O
standard	O
C++	B-Language
,	O
without	O
extensions	O
.	O
</s>
<s>
"	O
There	O
are	O
a	O
lot	O
of	O
very	O
experienced	O
C++	B-Language
developers	O
at	O
Microsoft	O
who	O
have	O
spent	O
decades-long	O
careers	O
working	O
with	O
C++	B-Language
and	O
COM	O
,	O
"	O
Kerr	O
says	O
.	O
</s>
<s>
"	O
I	O
had	O
had	O
some	O
previous	O
experience	O
projecting	O
COM	O
APIs	B-General_Concept
into	O
modern	O
C++	B-Language
,	O
so	O
I	O
decided	O
to	O
see	O
whether	O
I	O
could	O
apply	O
those	O
same	O
techniques	O
to	O
the	O
Windows	O
Runtime.	O
"	O
</s>
<s>
One	O
early	O
challenge	O
in	O
developing	O
C++	B-Language
/WinRT	I-Language
was	O
managing	O
the	O
trade-offs	O
that	O
the	O
Windows	O
Runtime	O
makes	O
to	O
support	O
projections	O
for	O
JavaScript	B-Language
and	O
managed	O
.NET	O
languages	O
out	O
of	O
the	O
box	O
.	O
</s>
<s>
The	O
complexity	O
in	O
the	O
way	O
that	O
generic	O
collections	O
work	O
across	O
language	O
projections	O
is	O
another	O
example	O
of	O
these	O
design	O
challenges	O
,	O
as	O
was	O
coming	O
up	O
with	O
an	O
efficient	O
way	O
for	O
standard	O
C++	B-Language
to	O
handle	O
the	O
Windows	O
Runtime	O
's	O
interface-versioning	O
model	O
.	O
</s>
<s>
"	O
It	O
really	O
pushed	O
my	O
understanding	O
of	O
C++	B-Language
at	O
that	O
time	O
,	O
and	O
it	O
's	O
since	O
pushed	O
the	O
Microsoft	B-Application
Visual	I-Application
C++	I-Application
compiler	O
to	O
more	O
efficiently	O
handle	O
such	O
techniques	O
at	O
this	O
scale.	O
"	O
</s>
