Hi, I have three c++ files: main.cpp, and querystring.{h,cpp} querystring.h contains the definition for the QueryString class and querystring.cpp contains the implementation. querystring.cpp and main.cpp both have the statement #include "querystring.h" Now when I run the compiler, I get a weird error- $ g++ main.cpp querystring.cpp -o out /tmp/ccxJ7C28.o: In function `main': main.cpp:(.text+0x3e): undefined reference to `QueryString::QueryString()' collect2: ld returned 1 exit status How am I supposed to compile the program? i.e. in general a multifile program having .hs and .cpps -- Regards, Nilesh Govindarajan Facebook: http://www.facebook.com/nilesh.gr Twitter: http://twitter.com/nileshgr Website: http://www.itech7.com VPS Hosting: http://www.itech7.com/a/vps