Hi there, the subject says it all. Under Cygwin, c_interface.h is installed in $PREFIX/include/Yap. However, c_interface.h immediately includes YapInterface.h, and this is not installed. Here is the relevant excerpt from the output of `make install': ... /usr/bin/install -c ./H/TermExt.h ./H/Atoms.h ... /usr/bin/install -c ./include/c_interface.h /usr/local/include/Yap/c_interface.h /usr/bin/install -c config.h /usr/local/include/Yap/config.h (cd library/random; make install) make[1]: Entering directory `/usr/local/distrib/Yap-5.0.0/library/random' /usr/bin/install -c random.dll /usr/local/lib/Yap ... All the best, Roberto -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it