<s>
The	O
Internet	B-Library
Server	I-Library
Application	I-Library
Programming	I-Library
Interface	I-Library
(	O
ISAPI	B-Library
)	O
is	O
an	O
N-tier	B-Operating_System
API	B-Application
of	O
Internet	B-Application
Information	I-Application
Services	I-Application
(	O
IIS	O
)	O
,	O
Microsoft	O
's	O
collection	O
of	O
Windows-based	O
web	B-Application
server	I-Application
services	O
.	O
</s>
<s>
The	O
most	O
prominent	O
application	O
of	O
IIS	O
and	O
ISAPI	B-Library
is	O
Microsoft	O
's	O
web	B-Application
server	I-Application
.	O
</s>
<s>
The	O
ISAPI	B-Library
has	O
also	O
been	O
implemented	O
by	O
Apache	B-Application
's	O
module	O
so	O
that	O
server-side	O
web	O
applications	O
written	O
for	O
Microsoft	O
's	O
IIS	O
can	O
be	O
used	O
with	O
Apache	B-Application
.	O
</s>
<s>
Other	O
third-party	O
web	B-Application
servers	I-Application
like	O
Zeus	B-Protocol
Web	I-Protocol
Server	I-Protocol
offer	O
ISAPI	B-Library
interfaces	O
,	O
too	O
.	O
</s>
<s>
Microsoft	O
's	O
web	B-Application
server	I-Application
application	O
software	O
is	O
called	O
Internet	B-Application
Information	I-Application
Services	I-Application
,	O
which	O
is	O
made	O
up	O
of	O
a	O
number	O
of	O
"	O
sub-applications	O
"	O
and	O
is	O
very	O
configurable	O
.	O
</s>
<s>
ASP.NET	B-Application
is	O
one	O
such	O
slice	O
of	O
IIS	O
,	O
allowing	O
a	O
programmer	O
to	O
write	O
web	O
applications	O
in	O
their	O
choice	O
of	O
programming	O
language	O
(	O
VB.NET	B-Language
,	O
C#	B-Application
,	O
F#	B-Operating_System
)	O
that	O
's	O
supported	O
by	O
the	O
Microsoft	O
.NET	O
CLR	O
.	O
</s>
<s>
ISAPI	B-Library
is	O
a	O
much	O
lower-level	O
programming	O
system	O
,	O
giving	O
much	O
better	O
performance	O
,	O
at	O
the	O
expense	O
of	O
simplicity	O
.	O
</s>
<s>
ISAPI	B-Library
consists	O
of	O
two	O
components	O
:	O
Extensions	O
and	O
Filters	O
.	O
</s>
<s>
These	O
are	O
the	O
only	O
two	O
types	O
of	O
applications	O
that	O
can	O
be	O
developed	O
using	O
ISAPI	B-Library
.	O
</s>
<s>
Both	O
Filters	O
and	O
Extensions	O
must	O
be	O
compiled	O
into	O
DLL	O
files	O
which	O
are	O
then	O
registered	O
with	O
IIS	O
to	O
be	O
run	O
on	O
the	O
web	B-Application
server	I-Application
.	O
</s>
<s>
ISAPI	B-Library
applications	O
can	O
be	O
written	O
using	O
any	O
language	O
which	O
allows	O
the	O
export	O
of	O
standard	O
C	O
functions	O
,	O
for	O
instance	O
C	O
,	O
C++	B-Language
,	O
Delphi	O
.	O
</s>
<s>
There	O
are	O
a	O
couple	O
of	O
libraries	O
available	O
which	O
help	O
to	O
ease	O
the	O
development	O
of	O
ISAPI	B-Library
applications	O
,	O
and	O
in	O
Delphi	O
Pascal	O
the	O
Intraweb	O
components	O
for	O
web-application	O
development	O
.	O
</s>
<s>
MFC	B-Language
includes	O
classes	O
for	O
developing	O
ISAPI	B-Library
applications	O
.	O
</s>
<s>
Additionally	O
,	O
there	O
is	O
the	O
ATL	B-Language
Server	I-Language
technology	O
which	O
includes	O
a	O
C++	B-Language
library	O
dedicated	O
to	O
developing	O
ISAPI	B-Library
applications	O
.	O
</s>
<s>
ISAPI	B-Library
Extensions	O
are	O
true	O
applications	O
that	O
run	O
on	O
IIS	O
.	O
</s>
<s>
ISAPI	B-Library
extensions	O
are	O
implemented	O
as	O
DLLs	O
that	O
are	O
loaded	O
into	O
a	O
process	O
that	O
is	O
controlled	O
by	O
IIS	O
.	O
</s>
<s>
Clients	O
can	O
access	O
ISAPI	B-Library
extensions	O
in	O
the	O
same	O
way	O
they	O
access	O
a	O
static	O
HTML	O
page	O
.	O
</s>
<s>
Certain	O
file	O
extensions	O
or	O
a	O
complete	O
folder	O
or	O
site	O
can	O
be	O
mapped	O
to	O
be	O
handled	O
by	O
an	O
ISAPI	B-Library
extension	O
.	O
</s>
<s>
ISAPI	B-Library
filters	O
are	O
used	O
to	O
modify	O
or	O
enhance	O
the	O
functionality	O
provided	O
by	O
IIS	O
.	O
</s>
<s>
They	O
always	O
run	O
on	O
an	O
IIS	B-Application
server	I-Application
and	O
filter	O
every	O
request	O
until	O
they	O
find	O
one	O
they	O
need	O
to	O
process	O
.	O
</s>
<s>
Filters	O
are	O
implemented	O
as	O
DLLs	O
and	O
can	O
be	O
registered	O
on	O
an	O
IIS	B-Application
server	I-Application
on	O
a	O
site	O
level	O
or	O
a	O
global	O
level	O
(	O
i.e.	O
,	O
they	O
apply	O
to	O
all	O
sites	O
on	O
an	O
IIS	B-Application
server	I-Application
)	O
.	O
</s>
<s>
Common	O
tasks	O
performed	O
by	O
ISAPI	B-Library
filters	O
include	O
:	O
</s>
<s>
This	O
is	O
a	O
list	O
of	O
common	O
ISAPI	B-Library
applications	O
implemented	O
as	O
ISAPI	B-Library
extensions	O
:	O
</s>
<s>
PHP	B-Application
,	O
available	O
for	O
free	O
to	O
install	O
,	O
not	O
maintained	O
anymore	O
.	O
</s>
<s>
ISAPI	B-Library
applications	O
can	O
be	O
developed	O
using	O
any	O
development	O
tool	O
that	O
can	O
generate	O
a	O
Windows	B-Library
DLL	O
.	O
</s>
<s>
Wizards	O
for	O
generating	O
ISAPI	B-Library
framework	O
applications	O
have	O
been	O
available	O
in	O
Microsoft	O
development	O
tools	O
since	O
Visual	O
C++	B-Language
4.0	O
.	O
</s>
