[ILUG] Very basic C question

[Máirtín O Sullivan]

This is probably very simple but I've just started to learn to program C on
an old Linux box (distribution is SuSE from about four years ago). Problem
is gcc (which I'm assuming is the right compiler) doesn't seem to be
recognising any of the .h files. I've included them in the code correctly
but any functions relating to them are going unrecognised by the compiler
and it spits out an error.
The problem in question is math.h and the fmod function.

Is there a path which must be set for gcc?

I'm guessing this is incredibly simple but it's been a long time since I've
been using linux so hopefully you lot should be able to sort is out.

Cheers