Programming :: Get Eclipse C Compiler To Work - Warning: Implicit Declaration Of Function Strlen

I have the plugin installed ok and have pasted in a C source file that I know works and am getting the following errors, I think because the linker options need to be set in some way. I cannot copy the errors but they all complain of implicit declaration of functions like this: -

warning: implicit declaration of function strlen

But I have the headers included, is this a linker problem? Here is the code -

#include <stdio.h>
#include <math.h>
int main(){

[code]...