Compiling unit gives ld error

I am running gpc version 20030830, based on gcc-3.3.2 on Mac OS 10.3. When attmpting to compile any unit, I get the following error: /usr/bin/ld: Undefined symbols: _main collect2: ld returned 1 exit status Any way for me to solve this problem by RTFM? I apologize if I missed it in my (as yet) futile but lengthy search of the GPC mail archive/documentation. Thanks so much, Frank