have you added the required link libraries to the project? Select Add Library(s) in the Project Menu.
I don't know with stormC demo, but with the full versions you should check that you have storm.lib and amiga.lib in the project.
In the project preferences the first include path is usually StormC:Include
ummm and your hello world should be:
#include
int main(void)
{
printf("Amiga Rules!\n");
return(0);
}
that should compile without any errors or warnings.