<s>
In	O
Win32	B-Library
application	O
programming	O
,	O
WindowProc	B-Library
(	O
or	O
window	O
procedure	O
)	O
is	O
a	O
user-defined	O
callback	O
function	O
that	O
processes	O
messages	O
sent	O
to	O
a	O
window	O
.	O
</s>
<s>
This	O
function	O
is	O
specified	O
when	O
an	O
application	O
registers	O
its	O
window	B-Library
class	I-Library
and	O
can	O
be	O
named	O
anything	O
(	O
not	O
necessarily	O
WindowProc	B-Library
)	O
.	O
</s>
<s>
The	O
function	O
prototype	O
of	O
WindowProc	B-Library
is	O
given	O
by	O
:	O
</s>
<s>
An	O
application	O
usually	O
calls	O
DefWindowProc	O
at	O
the	O
end	O
of	O
its	O
own	O
WindowProc	B-Library
function	O
so	O
that	O
whatever	O
messages	O
it	O
has	O
not	O
processed	O
are	O
passed	O
on	O
to	O
the	O
default	O
procedure	O
.	O
</s>
