Multi file programming

hello

tell me about your experiences with programming projects that use multiple files.

How do you organize code, how do you make sure ecah file is able to see the symbols defined in the other ones? what kindof module systems are you using and what ways are they good or bad? Do you have any visions for a radical change in the way to manage stuff like this?

I use the time-tested '1 file = 1line of code' paradigm. I put everything in a single directory in an alphabetic order and then build my project based on this ENTERPRISE build script:
cat * | $COMPILER_OR_INTERPRETER