<s>
The	O
Windows	B-Library
API	I-Library
,	O
informally	O
WinAPI	B-Library
,	O
is	O
Microsoft	O
's	O
core	O
set	O
of	O
application	B-Application
programming	I-Application
interfaces	I-Application
(	O
APIs	B-Application
)	O
available	O
in	O
the	O
Microsoft	B-Application
Windows	I-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
The	O
name	O
Windows	B-Library
API	I-Library
collectively	O
refers	O
to	O
several	O
different	O
platform	O
implementations	O
that	O
are	O
often	O
referred	O
to	O
by	O
their	O
own	O
names	O
(	O
for	O
example	O
,	O
Win32	B-Library
API	I-Library
)	O
;	O
see	O
the	O
versions	O
section	O
.	O
</s>
<s>
Almost	O
all	O
Windows	B-Application
programs	O
interact	O
with	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
On	O
the	O
Windows	B-Device
NT	I-Device
line	O
of	O
operating	B-General_Concept
systems	I-General_Concept
,	O
a	O
small	O
number	O
(	O
such	O
as	O
programs	O
started	O
early	O
in	O
the	O
Windows	B-Operating_System
startup	I-Operating_System
process	I-Operating_System
)	O
use	O
the	O
Native	B-Application
API	I-Application
.	O
</s>
<s>
Developer	O
support	O
is	O
available	O
in	O
the	O
form	O
of	O
a	O
software	B-Application
development	I-Application
kit	I-Application
,	O
Microsoft	B-Application
Windows	I-Application
SDK	I-Application
,	O
providing	O
documentation	O
and	O
tools	O
needed	O
to	O
build	O
software	O
based	O
on	O
the	O
Windows	B-Library
API	I-Library
and	O
associated	O
Windows	B-Application
interfaces	O
.	O
</s>
<s>
The	O
Windows	B-Library
API	I-Library
(	O
Win32	B-Library
)	O
is	O
focused	O
mainly	O
on	O
the	O
programming	B-Language
language	I-Language
C	I-Language
in	O
that	O
its	O
exposed	O
functions	O
and	O
data	O
structures	O
are	O
described	O
in	O
that	O
language	O
in	O
recent	O
versions	O
of	O
its	O
documentation	O
.	O
</s>
<s>
However	O
,	O
the	O
API	B-Application
may	O
be	O
used	O
by	O
any	O
programming	B-Language
language	I-Language
compiler	I-Language
or	O
assembler	B-Application
able	O
to	O
handle	O
the	O
(	O
well-defined	O
)	O
low-level	O
data	O
structures	O
along	O
with	O
the	O
prescribed	O
calling	O
conventions	O
for	O
calls	O
and	O
callbacks	O
.	O
</s>
<s>
Similarly	O
,	O
the	O
internal	O
implementation	O
of	O
the	O
API	B-Application
's	O
function	O
has	O
been	O
developed	O
in	O
several	O
languages	O
,	O
historically	O
.	O
</s>
<s>
Despite	O
the	O
fact	O
that	O
C	B-Language
is	O
not	O
an	O
object-oriented	B-Language
programming	I-Language
language	I-Language
,	O
the	O
Windows	B-Library
API	I-Library
and	O
Windows	B-Application
have	O
both	O
historically	O
been	O
described	O
as	O
object-oriented	B-Language
.	O
</s>
<s>
There	O
have	O
also	O
been	O
many	O
wrapper	O
classes	O
and	O
extensions	O
(	O
from	O
Microsoft	O
and	O
others	O
)	O
for	O
object-oriented	B-Language
languages	I-Language
that	O
make	O
this	O
object-oriented	B-Language
structure	O
more	O
explicit	O
(	O
Microsoft	B-Language
Foundation	I-Language
Class	I-Language
Library	I-Language
(	O
MFC	O
)	O
,	O
Visual	B-Library
Component	I-Library
Library	I-Library
(	O
VCL	O
)	O
,	O
GDI+	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
For	O
instance	O
,	O
Windows	B-Application
8	I-Application
provides	O
the	O
Windows	B-Library
API	I-Library
and	O
the	O
WinRT	O
API	B-Application
,	O
which	O
is	O
implemented	O
in	O
C++	B-Language
and	O
is	O
object-oriented	B-Language
by	O
design	O
.	O
</s>
<s>
The	O
functions	O
provided	O
by	O
the	O
Windows	B-Library
API	I-Library
can	O
be	O
grouped	O
into	O
eight	O
categories	O
:	O
</s>
<s>
Base	O
Services	O
Provide	O
access	O
to	O
the	O
basic	O
resources	O
available	O
to	O
a	O
Windows	B-Application
system	O
.	O
</s>
<s>
Included	O
are	O
things	O
like	O
file	B-Application
systems	I-Application
,	O
devices	B-Architecture
,	O
processes	B-Operating_System
,	O
threads	B-Operating_System
,	O
and	O
error	B-General_Concept
handling	I-General_Concept
.	O
</s>
<s>
These	O
functions	O
reside	O
in	O
kernel.exe	O
,	O
krnl286.exe	O
or	O
krnl386.exe	O
files	O
on	O
16-bit	B-Library
Windows	I-Library
,	O
and	O
kernel32.dll	O
and	O
KernelBase.dll	O
on	O
32	O
and	O
64	B-Device
bit	I-Device
Windows	B-Application
.	O
</s>
<s>
These	O
files	O
reside	O
in	O
the	O
folder	O
\Windows\System32	O
on	O
all	O
versions	O
of	O
Windows	B-Application
.	O
</s>
<s>
Included	O
are	O
things	O
like	O
the	O
Windows	B-Protocol
registry	I-Protocol
,	O
shutdown/restart	O
the	O
system	O
(	O
or	O
abort	O
)	O
,	O
start/stop/create	O
a	O
Windows	B-Application
service	O
,	O
manage	O
user	O
accounts	O
.	O
</s>
<s>
These	O
functions	O
reside	O
in	O
advapi32.dll	O
and	O
advapires32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
.	O
</s>
<s>
Graphics	B-Operating_System
Device	I-Operating_System
Interface	I-Operating_System
Provides	O
functions	O
to	O
output	O
graphics	O
content	O
to	O
monitors	B-Device
,	O
printers	O
,	O
and	O
other	O
output	B-Device
devices	I-Device
.	O
</s>
<s>
It	O
resides	O
in	O
gdi.exe	O
on	O
16-bit	B-Library
Windows	I-Library
,	O
and	O
gdi32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
in	O
user-mode	O
.	O
</s>
<s>
User	O
Interface	O
Provides	O
the	O
functions	O
to	O
create	O
and	O
manage	O
screen	O
windows	B-Application
and	O
most	O
basic	O
controls	O
,	O
such	O
as	O
buttons	O
and	O
scrollbars	O
,	O
receive	O
mouse	O
and	O
keyboard	O
input	O
,	O
and	O
other	O
functions	O
associated	O
with	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
part	O
of	O
Windows	B-Application
.	O
</s>
<s>
This	O
functional	O
unit	O
resides	O
in	O
user.exe	O
on	O
16-bit	B-Library
Windows	I-Library
,	O
and	O
user32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
.	O
</s>
<s>
Since	O
Windows	B-Application
XP	I-Application
versions	I-Application
,	O
the	O
basic	O
controls	O
reside	O
in	O
comctl32.dll	O
,	O
together	O
with	O
the	O
common	O
controls	O
(	O
Common	O
Control	O
Library	O
)	O
.	O
</s>
<s>
The	O
library	O
resides	O
in	O
a	O
file	O
called	O
commdlg.dll	O
on	O
16-bit	B-Library
Windows	I-Library
,	O
and	O
comdlg32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
.	O
</s>
<s>
It	O
is	O
grouped	O
under	O
the	O
User	O
Interface	O
category	O
of	O
the	O
API	B-Application
.	O
</s>
<s>
Common	O
Control	O
Library	O
Gives	O
applications	O
access	O
to	O
some	O
advanced	O
controls	O
provided	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
library	O
resides	O
in	O
a	O
dynamic-link	O
library	O
(	O
DLL	O
)	O
file	O
called	O
commctrl.dll	O
on	O
16-bit	B-Library
Windows	I-Library
,	O
and	O
comctl32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
.	O
</s>
<s>
It	O
is	O
grouped	O
under	O
the	O
User	O
Interface	O
category	O
of	O
the	O
API	B-Application
.	O
</s>
<s>
Windows	B-Application
Shell	O
Component	O
of	O
the	O
Windows	B-Library
API	I-Library
allows	O
applications	O
to	O
access	O
functions	O
provided	O
by	O
the	O
operating	B-Operating_System
system	I-Operating_System
shell	I-Operating_System
,	O
and	O
to	O
change	O
and	O
enhance	O
it	O
.	O
</s>
<s>
The	O
component	O
resides	O
in	O
shell.dll	O
on	O
16-bit	B-Library
Windows	I-Library
,	O
and	O
shell32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
.	O
</s>
<s>
It	O
is	O
grouped	O
under	O
the	O
User	O
Interface	O
category	O
of	O
the	O
API	B-Application
.	O
</s>
<s>
Network	O
Services	O
Give	O
access	O
to	O
the	O
various	O
networking	B-Architecture
abilities	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Its	O
subcomponents	O
include	O
NetBIOS	B-Protocol
,	O
Winsock	B-Application
,	O
NetDDE	O
,	O
remote	B-Operating_System
procedure	I-Operating_System
call	I-Operating_System
(	O
RPC	O
)	O
and	O
many	O
more	O
.	O
</s>
<s>
This	O
component	O
resides	O
in	O
netapi32.dll	O
on	O
32-bit	B-Application
Windows	I-Application
.	O
</s>
<s>
The	O
Internet	B-Application
Explorer	I-Application
(	O
IE	O
)	O
web	O
browser	O
also	O
exposes	O
many	O
APIs	B-Application
that	O
are	O
often	O
used	O
by	O
applications	O
,	O
and	O
as	O
such	O
could	O
be	O
considered	O
a	O
part	O
of	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
IE	O
has	O
been	O
included	O
with	O
the	O
operating	B-General_Concept
system	I-General_Concept
since	O
Windows	B-Application
95	I-Application
OSR2	O
and	O
has	O
provided	O
web-related	O
services	O
to	O
applications	O
since	O
Windows	B-Device
98	I-Device
.	O
</s>
<s>
An	O
embeddable	O
web	O
browser	O
control	O
,	O
contained	O
in	O
shdocvw.dll	O
and	O
mshtml.dll	B-Application
.	O
</s>
<s>
The	O
URL	O
moniker	O
service	O
,	O
held	O
in	O
urlmon.dll	O
,	O
which	O
provides	O
COM	B-Application
objects	I-Application
to	O
applications	O
for	O
resolving	O
URLs	O
.	O
</s>
<s>
DirectX	B-Application
Transforms	O
,	O
a	O
set	O
of	O
image	O
filter	O
components	O
.	O
</s>
<s>
Access	O
to	O
the	O
Windows	B-Application
Address	O
Books	O
.	O
</s>
<s>
The	O
classic	O
Windows	B-Application
Multimedia	O
API	B-Application
is	O
placed	O
in	O
winmm.dll	O
and	O
contains	O
functions	O
to	O
play	O
sound	O
files	O
,	O
to	O
send	O
and	O
receive	O
MIDI	O
messages	O
,	O
to	O
access	O
joysticks	O
,	O
and	O
to	O
facilitate	O
all	O
other	O
features	O
of	O
the	O
so-called	O
MCI	O
subsystem	O
of	O
Windows	B-Application
,	O
which	O
originates	O
from	O
the	O
Multimedia	O
Extensions	O
available	O
for	O
Windows	B-Application
3.0	O
separately	O
and	O
as	O
an	O
integral	O
part	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
since	O
Windows	B-Application
3.1	O
,	O
at	O
which	O
time	O
they	O
were	O
located	O
in	O
mmsystem.dll	O
.	O
</s>
<s>
Apart	O
from	O
that	O
,	O
as	O
part	O
of	O
every	O
Windows	B-Application
version	O
since	O
Windows	B-Application
95	I-Application
OSR2	O
,	O
Microsoft	O
has	O
provided	O
the	O
DirectX	B-Application
APIs	B-Application
—	O
a	O
loosely	O
related	O
set	O
of	O
graphics	O
and	O
gaming	O
services	O
,	O
which	O
includes	O
:	O
</s>
<s>
Direct2D	B-Library
for	O
hardware-accelerated	O
2D	O
vector	O
graphics	O
.	O
</s>
<s>
Direct3D	B-Application
for	O
hardware-accelerated	O
3D	O
graphics	O
.	O
</s>
<s>
DirectSound	B-Device
for	O
low-level	O
hardware-accelerated	O
sound	O
card	O
access	O
.	O
</s>
<s>
DirectInput	O
for	O
communication	O
with	O
input	O
devices	B-Architecture
such	O
as	O
joysticks	O
and	O
gamepads	O
.	O
</s>
<s>
DirectPlay	B-Protocol
as	O
a	O
multiplayer	O
gaming	O
infrastructure	O
.	O
</s>
<s>
This	O
component	O
has	O
been	O
deprecated	O
as	O
of	O
DirectX	B-Application
9	I-Application
,	O
and	O
Microsoft	O
no	O
longer	O
recommends	O
its	O
use	O
for	O
game	O
development	O
.	O
</s>
<s>
DirectDraw	B-Device
for	O
2D	O
graphics	O
in	O
earlier	O
DirectX	B-Application
versions	O
,	O
now	O
deprecated	O
and	O
replaced	O
with	O
Direct2D	B-Library
.	O
</s>
<s>
WinG	O
for	O
2D	O
graphics	O
in	O
16-bit	B-Device
games	O
written	O
for	O
Windows	B-Application
3.x	O
versions	O
.	O
</s>
<s>
Deprecated	O
with	O
Windows	B-Application
95	I-Application
release	O
.	O
</s>
<s>
Microsoft	O
also	O
provides	O
several	O
APIs	B-Application
for	O
media	O
encoding	O
and	O
playback	O
:	O
</s>
<s>
DirectShow	B-Library
,	O
which	O
builds	O
and	O
runs	O
generic	O
multimedia	O
pipelines	O
.	O
</s>
<s>
It	O
is	O
comparable	O
to	O
the	O
GStreamer	B-Language
framework	O
and	O
often	O
used	O
to	O
render	O
in-game	O
videos	O
and	O
build	O
media	B-Device
players	I-Device
(	O
Windows	B-Device
Media	I-Device
Player	I-Device
is	O
based	O
on	O
it	O
)	O
.	O
</s>
<s>
DirectShow	B-Library
is	O
no	O
longer	O
recommended	O
for	O
game	O
development	O
.	O
</s>
<s>
Media	B-Device
Foundation	I-Device
,	O
a	O
newer	O
digital	O
media	O
API	B-Application
intended	O
to	O
replace	O
DirectShow	B-Library
.	O
</s>
<s>
The	O
Windows	B-Library
API	I-Library
is	O
designed	O
mostly	O
for	O
the	O
interaction	O
between	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
an	O
application	O
.	O
</s>
<s>
For	O
communication	O
among	O
different	O
Windows	B-Application
applications	I-Application
,	O
Microsoft	O
has	O
developed	O
a	O
series	O
of	O
technologies	O
alongside	O
the	O
main	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
This	O
started	O
out	O
with	O
Dynamic	B-Operating_System
Data	I-Operating_System
Exchange	I-Operating_System
(	O
DDE	O
)	O
,	O
which	O
was	O
superseded	O
by	O
Object	B-Operating_System
Linking	I-Operating_System
and	I-Operating_System
Embedding	I-Operating_System
(	O
OLE	O
)	O
and	O
later	O
by	O
the	O
Component	B-Application
Object	I-Application
Model	I-Application
(	O
COM	B-Application
)	O
,	O
Automation	B-Application
Objects	I-Application
,	O
ActiveX	B-Application
controls	I-Application
,	O
and	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
Automation	O
specifically	O
relates	O
to	O
exporting	O
the	O
function	O
of	O
an	O
application	O
or	O
component	O
(	O
as	O
an	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
)	O
so	O
that	O
it	O
can	O
be	O
controlled	O
by	O
other	O
applications	O
instead	O
of	O
by	O
human	O
users	O
only	O
,	O
.NET	B-Application
is	O
a	O
self-contained	O
general	O
methodology	O
and	O
technology	O
to	O
develop	O
desktop	O
and	O
web	O
applications	O
written	O
in	O
a	O
variety	O
of	O
just-in-time	O
(	O
JIT	O
)	O
compiled	B-Language
languages	O
.	O
</s>
<s>
Windows.pas	B-Library
is	O
a	O
Pascal/Delphi	O
unit	O
which	O
contains	O
the	O
Windows-specific	O
API	B-Application
declarations	O
.	O
</s>
<s>
It	O
is	O
the	O
Pascal	B-Application
equivalent	O
to	O
windows.h	B-Language
,	O
used	O
in	O
C	B-Language
.	O
</s>
<s>
Various	O
wrappers	B-Library
were	O
developed	O
by	O
Microsoft	O
that	O
took	O
over	O
some	O
of	O
the	O
more	O
low	O
level	O
functions	O
of	O
the	O
Windows	B-Library
API	I-Library
,	O
and	O
allowed	O
applications	O
to	O
interact	O
with	O
the	O
API	B-Application
in	O
a	O
more	O
abstract	O
manner	O
.	O
</s>
<s>
Microsoft	B-Language
Foundation	I-Language
Class	I-Language
Library	I-Language
(	O
MFC	O
)	O
wrapped	O
Windows	B-Library
API	I-Library
functionality	O
in	O
C++	B-Language
classes	O
,	O
and	O
thus	O
allows	O
a	O
more	O
object-oriented	B-Language
way	O
to	O
interact	O
with	O
the	O
API	B-Application
.	O
</s>
<s>
The	O
Active	B-Language
Template	I-Language
Library	I-Language
(	O
ATL	O
)	O
is	O
a	O
template	B-Application
oriented	O
wrapper	O
for	O
COM	B-Application
.	O
</s>
<s>
The	O
Windows	B-Application
Template	I-Application
Library	I-Application
(	O
WTL	O
)	O
was	O
developed	O
as	O
an	O
extension	O
to	O
ATL	O
,	O
and	O
intended	O
as	O
a	O
smaller	O
alternative	O
to	O
MFC	O
.	O
</s>
<s>
Most	O
application	B-Application
frameworks	I-Application
for	O
Windows	B-Application
(	O
at	O
least	O
partly	O
)	O
wrap	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
Thus	O
,	O
the	O
.NET	B-Application
Framework	I-Application
and	O
Java	B-Language
,	O
likewise	O
any	O
other	O
programming	O
languages	O
under	O
Windows	B-Application
,	O
are	O
(	O
or	O
contain	O
)	O
wrapper	B-Library
libraries	I-Library
.	O
</s>
<s>
The	O
Windows	B-Library
API	I-Library
has	O
always	O
exposed	O
a	O
large	O
part	O
of	O
the	O
underlying	O
structure	O
of	O
the	O
Windows	B-Application
systems	O
to	O
programmers	O
.	O
</s>
<s>
This	O
had	O
the	O
advantage	O
of	O
giving	O
them	O
much	O
flexibility	O
and	O
power	O
over	O
their	O
applications	O
,	O
but	O
also	O
creates	O
great	O
responsibility	O
in	O
how	O
applications	O
handle	O
various	O
low-level	O
,	O
sometimes	O
tedious	O
,	O
operations	O
that	O
are	O
associated	O
with	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
.	O
</s>
<s>
For	O
example	O
,	O
a	O
beginning	O
C	B-Language
programmer	O
will	O
often	O
write	O
the	O
simple	O
"	O
hello	O
world	O
"	O
as	O
their	O
first	O
assignment	O
.	O
</s>
<s>
The	O
Windows	B-Application
version	O
was	O
still	O
only	O
one	O
working	O
line	O
of	O
code	O
but	O
it	O
required	O
many	O
,	O
many	O
more	O
lines	O
of	O
overhead	O
.	O
</s>
<s>
Charles	O
Petzold	O
,	O
who	O
wrote	O
several	O
books	O
about	O
programming	O
for	O
the	O
Windows	B-Library
API	I-Library
,	O
said	O
:	O
"	O
The	O
original	O
hello	O
world	O
program	O
in	O
the	O
Windows	B-Application
1.0	I-Application
SDK	O
was	O
a	O
bit	O
of	O
a	O
scandal	O
.	O
</s>
<s>
HELLO.C	O
was	O
about	O
150	O
lines	O
long	O
,	O
and	O
the	O
HELLO.RC	O
resource	O
script	O
had	O
another	O
20	O
or	O
so	O
more	O
lines	O
.	O
</s>
<s>
(	O
...	O
)	O
Veteran	O
programmers	O
often	O
curled	O
up	O
in	O
horror	O
or	O
laughter	O
when	O
encountering	O
the	O
Windows	B-Application
hello-world	O
program.	O
"	O
</s>
<s>
Over	O
the	O
years	O
,	O
various	O
changes	O
and	O
additions	O
were	O
made	O
to	O
Windows	B-Application
systems	O
,	O
and	O
the	O
Windows	B-Library
API	I-Library
changed	O
and	O
grew	O
to	O
reflect	O
this	O
.	O
</s>
<s>
The	O
Windows	B-Library
API	I-Library
for	O
Windows	B-Application
1.0	I-Application
supported	O
fewer	O
than	O
450	O
function	O
calls	O
,	O
whereas	O
modern	O
versions	O
of	O
the	O
Windows	B-Library
API	I-Library
support	O
thousands	O
.	O
</s>
<s>
However	O
,	O
in	O
general	O
,	O
the	O
interface	O
remained	O
fairly	O
consistent	O
,	O
and	O
an	O
old	O
Windows	B-Application
1.0	I-Application
application	O
will	O
still	O
look	O
familiar	O
to	O
a	O
programmer	O
who	O
is	O
used	O
to	O
the	O
modern	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
Microsoft	O
has	O
made	O
an	O
effort	O
to	O
maintain	O
backward	B-General_Concept
compatibility	I-General_Concept
.	O
</s>
<s>
To	O
achieve	O
this	O
,	O
when	O
developing	O
new	O
versions	O
of	O
Windows	B-Application
,	O
Microsoft	O
sometimes	O
implemented	O
workarounds	O
to	O
allow	O
compatibility	O
with	O
third-party	O
software	O
that	O
used	O
the	O
prior	O
version	O
in	O
an	O
undocumented	O
or	O
even	O
inadvisable	O
way	O
.	O
</s>
<s>
Raymond	O
Chen	O
,	O
a	O
Microsoft	O
developer	O
who	O
works	O
on	O
the	O
Windows	B-Library
API	I-Library
,	O
has	O
said	O
:	O
"	O
I	O
could	O
probably	O
write	O
for	O
months	O
solely	O
about	O
bad	O
things	O
apps	O
do	O
and	O
what	O
we	O
had	O
to	O
do	O
to	O
get	O
them	O
to	O
work	O
again	O
(	O
often	O
in	O
spite	O
of	O
themselves	O
)	O
.	O
</s>
<s>
If	O
any	O
application	O
failed	O
to	O
run	O
on	O
Windows	B-Application
95	I-Application
,	O
I	O
took	O
it	O
as	O
a	O
personal	O
failure.	O
"	O
</s>
<s>
One	O
of	O
the	O
largest	O
changes	O
to	O
the	O
Windows	B-Library
API	I-Library
was	O
the	O
transition	O
from	O
Win16	B-Library
(	O
shipped	O
in	O
Windows	B-Application
3.1	O
and	O
older	O
)	O
to	O
Win32	B-Library
(	O
Windows	B-Device
NT	I-Device
and	O
Windows	B-Application
95	I-Application
and	O
up	O
)	O
.	O
</s>
<s>
While	O
Win32	B-Library
was	O
originally	O
introduced	O
with	O
Windows	B-Device
NT	I-Device
3.1	I-Device
and	O
Win32s	B-Library
allowed	O
use	O
of	O
a	O
Win32	B-Library
subset	O
before	O
Windows	B-Application
95	I-Application
,	O
it	O
was	O
not	O
until	O
Windows	B-Application
95	I-Application
that	O
widespread	O
porting	O
of	O
applications	O
to	O
Win32	B-Library
began	O
.	O
</s>
<s>
To	O
ease	O
the	O
transition	O
,	O
in	O
Windows	B-Application
95	I-Application
,	O
for	O
developers	O
outside	O
and	O
inside	O
Microsoft	O
,	O
a	O
complex	O
scheme	O
of	O
API	B-Application
thunks	B-Application
was	O
used	O
that	O
could	O
allow	O
32-bit	O
code	O
to	O
call	O
into	O
16-bit	B-Device
code	O
(	O
for	O
most	O
of	O
Win16	B-Library
APIs	B-Application
)	O
and	O
vice	O
versa	O
.	O
</s>
<s>
Flat	O
thunks	B-Application
allowed	O
32-bit	O
code	O
to	O
call	O
into	O
16-bit	B-Device
libraries	O
,	O
and	O
the	O
scheme	O
was	O
used	O
extensively	O
inside	O
Windows	B-Application
95	I-Application
's	O
libraries	O
to	O
avoid	O
porting	O
the	O
whole	O
OS	O
to	O
Win32	B-Library
in	O
one	O
batch	O
.	O
</s>
<s>
In	O
Windows	B-Device
NT	I-Device
,	O
the	O
OS	O
was	O
pure	O
32-bit	O
,	O
except	O
parts	O
for	O
compatibility	O
with	O
16-bit	B-Device
applications	O
,	O
and	O
only	O
generic	O
thunks	B-Application
were	O
available	O
to	O
thunk	B-Application
from	O
Win16	B-Library
to	O
Win32	B-Library
,	O
as	O
for	O
Windows	B-Application
95	I-Application
.	O
</s>
<s>
The	O
Platform	B-Application
SDK	I-Application
shipped	O
with	O
a	O
compiler	B-Language
that	O
could	O
produce	O
the	O
code	O
needed	O
for	O
these	O
thunks	B-Application
.	O
</s>
<s>
Versions	O
of	O
64-bit	B-Device
Windows	B-Application
are	O
also	O
able	O
to	O
run	O
32-bit	O
applications	O
via	O
WoW64	B-Application
.	O
</s>
<s>
The	O
SysWOW64	B-Application
folder	O
located	O
in	O
the	O
Windows	B-Application
folder	O
on	O
the	O
OS	O
drive	O
contains	O
several	O
tools	O
to	O
support	O
32-bit	O
applications	O
.	O
</s>
<s>
Almost	O
every	O
new	O
version	O
of	O
Microsoft	B-Application
Windows	I-Application
has	O
introduced	O
its	O
own	O
additions	O
and	O
changes	O
to	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
The	O
name	O
of	O
the	O
API	B-Application
,	O
however	O
,	O
remained	O
consistent	O
between	O
different	O
Windows	B-Application
versions	O
,	O
and	O
name	O
changes	O
were	O
kept	O
limited	O
to	O
major	O
architectural	O
and	O
platform	O
changes	O
for	O
Windows	B-Application
.	O
</s>
<s>
Microsoft	O
eventually	O
changed	O
the	O
name	O
of	O
the	O
then	O
current	O
Win32	B-Library
API	I-Library
family	O
into	O
Windows	B-Library
API	I-Library
and	O
made	O
it	O
into	O
a	O
catch-all	O
term	O
for	O
both	O
past	O
and	O
future	O
API	B-Application
versions	O
.	O
</s>
<s>
Win16	B-Library
is	O
the	O
API	B-Application
for	O
the	O
first	O
,	O
16-bit	B-Device
versions	O
of	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
These	O
were	O
initially	O
referred	O
to	O
as	O
simply	O
the	O
Windows	B-Library
API	I-Library
,	O
but	O
were	O
later	O
renamed	O
to	O
Win16	B-Library
in	O
an	O
effort	O
to	O
distinguish	O
them	O
from	O
the	O
newer	O
,	O
32-bit	O
version	O
of	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
The	O
functions	O
of	O
Win16	B-Library
API	B-Application
reside	O
in	O
mainly	O
the	O
core	O
files	O
of	O
the	O
OS	O
:	O
kernel.exe	O
(	O
or	O
krnl286.exe	O
or	O
krnl386.exe	O
)	O
,	O
user.exe	O
and	O
gdi.exe	O
.	O
</s>
<s>
Win32	B-Library
is	O
the	O
32-bit	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
for	O
32-bit	O
versions	O
of	O
Windows	B-Application
(	O
NT	O
,	O
95	O
,	O
and	O
later	O
versions	O
)	O
.	O
</s>
<s>
The	O
API	B-Application
consists	O
of	O
functions	O
implemented	O
,	O
as	O
with	O
Win16	B-Library
,	O
in	O
system	O
DLLs	O
.	O
</s>
<s>
The	O
core	O
DLLs	O
of	O
Win32	B-Library
are	O
kernel32.dll	O
,	O
user32.dll	O
,	O
and	O
gdi32.dll	O
.	O
</s>
<s>
Win32	B-Library
was	O
introduced	O
with	O
Windows	B-Device
NT	I-Device
.	O
</s>
<s>
The	O
version	O
of	O
Win32	B-Library
shipped	O
with	O
Windows	B-Application
95	I-Application
was	O
initially	O
referred	O
to	O
as	O
Win32c	O
,	O
with	O
c	B-Language
meaning	O
compatibility	O
.	O
</s>
<s>
This	O
term	O
was	O
later	O
abandoned	O
by	O
Microsoft	O
in	O
favor	O
of	O
Win32	B-Library
.	O
</s>
<s>
Win32s	B-Library
is	O
an	O
extension	O
for	O
the	O
Windows	B-Application
3.1x	O
family	O
of	O
Microsoft	B-Application
Windows	I-Application
that	O
implemented	O
a	O
subset	O
of	O
the	O
Win32	B-Library
API	I-Library
for	O
these	O
systems	O
.	O
</s>
<s>
Win64	O
is	O
the	O
variant	O
of	O
the	O
API	B-Application
implemented	O
on	O
64-bit	B-Device
platforms	O
of	O
the	O
Windows	B-Application
architecture	O
(	O
,	O
x86-64	B-Device
and	O
AArch64	B-Architecture
)	O
.	O
</s>
<s>
Both	O
32-bit	O
and	O
64-bit	B-Device
versions	O
of	O
an	O
application	O
can	O
be	O
still	O
compiled	B-Language
from	O
one	O
codebase	B-General_Concept
,	O
although	O
some	O
older	O
APIs	B-Application
have	O
been	O
deprecated	O
,	O
and	O
some	O
of	O
the	O
APIs	B-Application
that	O
were	O
already	O
deprecated	O
in	O
Win32	B-Library
were	O
removed	O
.	O
</s>
<s>
All	O
memory	O
pointers	O
are	O
64-bit	B-Device
by	O
default	O
(	O
the	O
LLP64	O
model	O
)	O
,	O
so	O
the	O
source	O
code	O
must	O
be	O
checked	O
for	O
compatibility	O
with	O
64-bit	B-Device
pointer	O
arithmetic	O
and	O
rewritten	O
as	O
necessary	O
.	O
</s>
<s>
WinCE	B-Operating_System
is	O
the	O
implementation	O
of	O
the	O
Windows	B-Library
API	I-Library
for	O
the	O
Windows	B-Operating_System
CE	I-Operating_System
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
Wine	B-Application
project	I-Application
provides	O
a	O
Win32	B-Library
API	I-Library
compatibility	B-General_Concept
layer	I-General_Concept
for	O
Unix-like	B-Operating_System
platforms	O
,	O
between	O
Linux	O
kernel	O
API	B-Application
and	O
programs	O
written	O
for	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
ReactOS	B-Application
goes	O
a	O
step	O
further	O
and	O
aims	O
to	O
implement	O
the	O
full	O
Windows	B-Application
operating	I-Application
system	I-Application
,	O
working	O
closely	O
with	O
the	O
Wine	B-Application
project	I-Application
to	O
promote	O
code	O
re-use	O
and	O
compatibility	O
.	O
</s>
<s>
DosWin32	B-Device
and	O
HX	B-Device
DOS	I-Device
Extender	I-Device
are	O
other	O
projects	O
which	O
emulate	O
the	O
Windows	B-Library
API	I-Library
to	O
allow	O
executing	O
simple	O
Windows	B-Application
programs	O
from	O
a	O
DOS	B-Device
command	O
line	O
.	O
</s>
<s>
Odin	B-General_Concept
is	O
a	O
project	O
to	O
emulate	O
Win32	B-Library
on	O
OS/2	B-Application
,	O
superseding	O
the	O
original	O
Win-OS/2	B-Application
emulation	O
which	O
was	O
based	O
on	O
Microsoft	O
code	O
.	O
</s>
<s>
Other	O
minor	O
implementations	O
include	O
the	O
MEWEL	O
and	O
Zinc	B-Library
libraries	O
which	O
were	O
intended	O
to	O
implement	O
a	O
subset	O
of	O
the	O
Win16	B-Library
API	B-Application
on	O
DOS	B-Device
(	O
see	O
List	B-Operating_System
of	I-Operating_System
platform-independent	I-Operating_System
GUI	I-Operating_System
libraries	I-Operating_System
)	O
.	O
</s>
<s>
Windows	B-Device
Interface	I-Device
Source	I-Device
Environment	I-Device
(	O
WISE	O
)	O
was	O
a	O
licensing	O
program	O
from	O
Microsoft	O
which	O
allowed	O
developers	O
to	O
recompile	B-Language
and	O
run	O
Windows-based	O
applications	O
on	O
Unix	B-Application
and	O
Macintosh	B-Device
platforms	O
.	O
</s>
<s>
WISE	O
SDKs	O
were	O
based	O
on	O
an	O
emulator	O
of	O
the	O
Windows	B-Library
API	I-Library
that	O
could	O
run	O
on	O
those	O
platforms	O
.	O
</s>
<s>
Efforts	O
toward	O
standardization	O
included	O
Sun	O
's	O
Public	O
Windows	B-Application
Interface	O
(	O
PWI	O
)	O
for	O
Win16	B-Library
(	O
see	O
also	O
:	O
Sun	B-General_Concept
Windows	I-General_Concept
Application	I-General_Concept
Binary	I-General_Concept
Interface	I-General_Concept
(	O
Wabi	B-General_Concept
)	O
)	O
,	O
Willows	O
Software	O
's	O
Application	B-Application
Programming	I-Application
Interface	I-Application
for	O
Windows	B-Application
(	O
APIW	O
)	O
for	O
Win16	B-Library
and	O
Win32	B-Library
(	O
see	O
also	O
:	O
Willows	O
TWIN	O
)	O
,	O
and	O
ECMA-234	O
,	O
which	O
attempted	O
to	O
standardize	O
the	O
Windows	B-Library
API	I-Library
bindingly	O
.	O
</s>
<s>
To	O
develop	O
software	O
that	O
uses	O
the	O
Windows	B-Library
API	I-Library
,	O
a	O
compiler	B-Language
must	O
be	O
able	O
to	O
use	O
the	O
Microsoft-specific	O
DLLs	O
listed	O
above	O
(	O
COM-objects	O
are	O
outside	O
Win32	B-Library
and	O
assume	O
a	O
certain	O
vtable	O
layout	O
)	O
.	O
</s>
<s>
The	O
compiler	B-Language
must	O
either	O
handle	O
the	O
header	O
files	O
that	O
expose	O
the	O
interior	O
API	B-Application
function	I-Application
names	O
,	O
or	O
supply	O
such	O
files	O
.	O
</s>
<s>
For	O
the	O
language	O
C++	B-Language
,	O
Zortech	O
(	O
later	O
Symantec	O
,	O
then	O
Digital	B-Language
Mars	I-Language
)	O
,	O
Watcom	O
and	O
Borland	O
have	O
all	O
produced	O
well	O
known	O
commercial	O
compilers	B-Language
that	O
have	O
been	O
used	O
often	O
with	O
Win16	B-Library
,	O
Win32s	B-Library
,	O
and	O
Win32	B-Library
.	O
</s>
<s>
Some	O
of	O
them	O
supplied	O
memory	O
extenders	O
,	O
allowing	O
Win32	B-Library
programs	O
to	O
run	O
on	O
Win16	B-Library
with	O
Microsoft	O
's	O
redistributable	O
Win32s	B-Library
DLL	O
.	O
</s>
<s>
The	O
Zortech	O
compiler	B-Language
was	O
probably	O
one	O
of	O
the	O
first	O
stable	O
and	O
usable	O
C++	B-Language
compilers	B-Language
for	O
Windows	B-Application
programming	O
,	O
before	O
Microsoft	O
had	O
a	O
C++	B-Language
compiler	B-Language
.	O
</s>
<s>
For	O
certain	O
classes	O
of	O
applications	O
,	O
the	O
compiler	B-Language
system	O
should	O
also	O
be	O
able	O
to	O
handle	O
interface	B-General_Concept
description	I-General_Concept
language	I-General_Concept
(	O
IDL	O
)	O
files	O
.	O
</s>
<s>
Collectively	O
,	O
these	O
prerequisites	O
(	O
compilers	B-Language
,	O
tools	O
,	O
libraries	O
,	O
and	O
headers	O
)	O
are	O
known	O
as	O
the	O
Microsoft	B-Application
Platform	I-Application
SDK	I-Application
.	O
</s>
<s>
For	O
a	O
time	O
,	O
the	O
Microsoft	B-Application
Visual	I-Application
Studio	I-Application
and	O
Borland	O
's	O
integrated	O
development	O
system	O
were	O
the	O
only	O
integrated	B-Application
development	I-Application
environments	I-Application
(	O
IDEs	O
)	O
that	O
could	O
provide	O
this	O
(	O
although	O
,	O
the	O
SDK	O
is	O
downloadable	O
for	O
free	O
separately	O
from	O
the	O
entire	O
IDE	O
suite	O
,	O
from	O
)	O
.	O
</s>
<s>
,	O
the	O
MinGW	B-Application
and	O
Cygwin	B-Language
projects	O
also	O
provide	O
such	O
an	O
environment	O
based	O
on	O
the	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
(	O
GCC	B-Application
)	O
,	O
using	O
a	O
stand-alone	O
header	O
file	O
set	O
,	O
to	O
make	O
linking	O
against	O
the	O
Win32-specific	O
DLLs	O
simple	O
.	O
</s>
<s>
LCC-Win32	B-Language
is	O
a	O
C	B-Language
compiler	B-Language
maintained	O
by	O
Jacob	O
Navia	O
,	O
freeware	B-License
for	O
non-commercial	O
use	O
.	O
</s>
<s>
Pelles	O
C	B-Language
is	O
a	O
freeware	B-License
C	B-Language
compiler	B-Language
maintained	O
by	O
Pelle	O
Orinius	O
.	O
</s>
<s>
Free	B-Operating_System
Pascal	I-Operating_System
is	O
a	O
free	B-Application
software	I-Application
Object	B-Language
Pascal	I-Language
compiler	B-Language
that	O
supports	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
The	O
MASM32	O
package	O
is	O
a	O
mature	O
project	O
providing	O
support	O
for	O
the	O
Windows	B-Library
API	I-Library
under	O
Microsoft	B-Application
Macro	I-Application
Assembler	I-Application
(	O
MASM	B-Application
)	O
by	O
using	O
custom	O
made	O
or	O
converted	O
headers	O
and	O
libraries	O
from	O
the	O
Platform	B-Application
SDK	I-Application
.	O
</s>
<s>
Flat	B-Application
assembler	I-Application
FASM	B-Application
allows	O
building	O
Windows	B-Application
programs	O
without	O
using	O
an	O
external	O
linker	O
,	O
even	O
when	O
running	O
on	O
Linux	O
.	O
</s>
<s>
Windows	B-Application
specific	O
compiler	B-Language
support	O
is	O
also	O
needed	O
for	O
Structured	O
Exception	B-General_Concept
Handling	I-General_Concept
(	O
SEH	O
)	O
.	O
</s>
<s>
This	O
system	O
serves	O
two	O
purposes	O
:	O
it	O
provides	O
a	O
substrate	O
on	O
which	O
language-specific	O
exception	B-General_Concept
handling	I-General_Concept
can	O
be	O
implemented	O
,	O
and	O
it	O
is	O
how	O
the	O
kernel	O
notifies	O
applications	O
of	O
exceptional	O
conditions	O
such	O
as	O
dereferencing	O
an	O
invalid	O
pointer	O
or	O
stack	O
overflow	O
.	O
</s>
<s>
The	O
Microsoft/Borland	O
C++	B-Language
compilers	B-Language
had	O
the	O
ability	O
to	O
use	O
this	O
system	O
as	O
soon	O
as	O
it	O
was	O
introduced	O
in	O
Windows	B-Application
95	I-Application
and	O
NT	O
,	O
however	O
the	O
actual	O
implementation	O
was	O
undocumented	O
and	O
had	O
to	O
be	O
reverse	O
engineered	O
for	O
the	O
Wine	B-Application
project	I-Application
and	O
free	O
compilers	B-Language
.	O
</s>
<s>
SEH	O
is	O
based	O
on	O
pushing	O
exception	B-General_Concept
handler	I-General_Concept
frames	O
onto	O
the	O
stack	O
,	O
then	O
adding	O
them	O
to	O
a	O
linked	O
list	O
stored	O
in	O
thread-local	O
storage	O
(	O
the	O
first	O
field	O
of	O
the	O
thread	B-Operating_System
environment	O
block	O
)	O
.	O
</s>
<s>
Eventually	O
,	O
every	O
exception	O
unhandled	O
by	O
the	O
application	O
will	O
be	O
dealt	O
with	O
by	O
the	O
default	O
backstop	O
handler	O
,	O
which	O
pops	O
up	O
the	O
Windows	B-Application
common	O
crash	O
dialog	O
.	O
</s>
