Copy File Function in Linux Kernel

Hi everybody , I'm Sultan

Linux and Ubuntu beginner.

I downloaded the source code from this link: http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.18.1.tar.bz2

I want to see when i press on a file: copy .. and paste in another place.

how is it work ?

i think using C language .. read and create .. etc

where can i find the source code for this function ( copy file )

Thanks ,, Sultan