Newbie question

Hi.
ummm....I wondering
if I #include many many file in C++,
or import many many package in JAVA,
what will happen?

Will my file become bigger bigger?
even if got function never use?
Or will compiler auto remove all the never use function?

Thank u BBS!

I don't even program, but I post on /frog/ because all other text boards (even non-world4ch ones) are pretty much dead