<s>
A	O
cross-platform	B-General_Concept
support	I-General_Concept
middleware	I-General_Concept
(	O
CPSM	O
)	O
is	O
a	O
software	O
abstraction	B-Architecture
layer	I-Architecture
that	O
guarantees	O
the	O
existence	O
,	O
and	O
correct	O
implementation	O
,	O
of	O
a	O
set	O
of	O
services	O
on	O
top	O
a	O
set	O
of	O
platforms	B-Device
.	O
</s>
<s>
The	O
abstraction	O
method	O
in	O
the	O
CPSM	O
development	O
is	O
the	O
method	O
used	O
to	O
compile	O
the	O
concrete	O
source	O
code	O
for	O
a	O
given	O
platform	O
without	O
compromising	O
the	O
abstract	B-Architecture
interfaces	I-Architecture
provided	O
.	O
</s>
<s>
The	O
most	O
commonly	O
used	O
abstraction	O
methods	O
in	O
CPSM	O
development	O
are	O
:	O
conditional	B-Application
compilation	I-Application
and	O
directory	O
separation	O
of	O
sources	O
.	O
</s>
<s>
The	O
second	O
method	O
takes	O
advantage	O
of	O
the	O
filesystem	B-Application
organization	O
to	O
divide	O
the	O
source	O
code	O
in	O
different	O
folders	O
,	O
one	O
for	O
each	O
incompatible	O
platform	O
.	O
</s>
<s>
Thus	O
delegating	O
the	O
selection	O
problem	O
to	O
the	O
build	B-Application
system	I-Application
.	O
</s>
<s>
Some	O
distributions	O
like	O
MSYS	B-Application
and	O
Cygwin	B-Language
may	O
help	O
build	O
the	O
cross-platform	O
code	O
in	O
a	O
Unix-like	B-Operating_System
environment	O
even	O
on	O
Microsoft	O
Windows	O
.	O
</s>
