Multiplatform Development?

From: Artificer (
Date: 11/05/05

Date: 4 Nov 2005 19:11:52 -0800

I wonder how huge projects like OpenOffice and MySQL can be developed
to run on so many platforms. To be more specific I want to know if they
code different versions of the software or there is a specific set of
library that are known to run exactly the same way on different
platforms so you can write the code only once and compile it

Of course I know about Java but I am more interested in the kind of
software that usually will be developed on a more low level language
like a database server.