Hi, Having realised (courtesy of Prof Ripley) that I was using the wrong compiler, I have now switched to MINGW. However, when I try and compile my .cc file using Rcmd SHLIB fileGT.cc I get the following error... Cannot export data_in: symbol not defined Cannot export dim: symbol not defined Cannot export k: symbol not defined Cannot export m_pts: symbol not defined Cannot export rapidFileGT: symbol not defined Cannot export readDataPt: symbol not defined Could anyone shed light on what this means? Thanks in advance, Sam. [[alternative HTML version deleted]]