https://community.intel.com/t5/Software-Archive/Using-external-DLL-s-with-Visual-Fortran/m-p/973398#M24536 It looks to me as if the linker thinks that you're trying to build your own DLL with the .DEF file. You shouldn't need both the .DEF and .LIB - just use the .LIB and remove the .DEF from the project.<BR /><BR />Steve Sat, 10 Nov 2001 10:48:23 GMT Steven_L_Intel1 2001-11-10T10:48:23Z https://community.intel.com/t5/Software-Archive/Using-external-DLL-s-with-Visual-Fortran/m-p/973397#M24535 Hi, <BR /> I'm trying to write some code to download information from a piece of hardware. The manufacturers provided a .dll file with its associated .def and .lib files containing commands to download the data from the serial port. I can compile the code that I have written, but when I try to build the executable file I get the following error message: <BR /> <BR />Linking... <BR /> Creating library Debug/cloud.lib and object Debug/cloud.exp <BR />cloud.exp : warning LNK4070: /OUT:VANTAGEPRO.exe directive in .EXP differs from output filename "Debug/cloud.exe"; ignoring directive <BR />Debug/cloud.exe : warning LNK4086: entrypoint "_mainCRTStartup" is not __stdcall with 12 bytes of arguments; image may not run <BR />cloud.obj : error LNK2001: unresolved external symbol _OPENCOMMPORT_V@0 <BR />cloud.obj : error LNK2001: unresolved external symbol _LOADCURRENTVANTAGEDATA_V@0 <BR />cloud.obj : error LNK2001: unresolved external symbol _GETOUTSIDETEMP_V@0 <BR />cloud.obj : error LNK2001: unresolved external symbol _CLOSECOMMANDPORT_V@0 <BR />Debug/cloud.exe : fatal error LNK1120: 4 unresolved externals <BR />Error executing link.exe. <BR /> <BR />cloud.exe - 5 error(s), 2 warning(s) <BR /> <BR />I think that this may suggest that there's a line in the manufacturers files which is wrongly directing the output, but I can't find it. Can anyone help? Sat, 10 Nov 2001 07:58:35 GMT https://community.intel.com/t5/Software-Archive/Using-external-DLL-s-with-Visual-Fortran/m-p/973397#M24535 Intel_C_Intel 2001-11-10T07:58:35Z https://community.intel.com/t5/Software-Archive/Using-external-DLL-s-with-Visual-Fortran/m-p/973398#M24536 It looks to me as if the linker thinks that you're trying to build your own DLL with the .DEF file. You shouldn't need both the .DEF and .LIB - just use the .LIB and remove the .DEF from the project.<BR /><BR />Steve Sat, 10 Nov 2001 10:48:23 GMT https://community.intel.com/t5/Software-Archive/Using-external-DLL-s-with-Visual-Fortran/m-p/973398#M24536 Steven_L_Intel1 2001-11-10T10:48:23Z