Thanks, I believe you are saying, in a different way , what I concluded. Each source (.cpp) is being compiled interdependently therefore HAS to have all of the "parameters" In my case #define DEBUG use namespace std; and #include (there is another discussion about using namesapce std and cout). I did added -v for verbose output from both compiler and linker and with little patience ( few lines of output ) I can see both processes. Appreciate all who participated in discussion of actually very fundamental process as comping and linking. Thanks everybody. Cheers Vaclav