You should also remember to export your functions from the DLL and import them into the program that uses the DLL. Generally, this is done using preprocessor definitions in the header file:
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#ifdef MYDLL_PROJECT // this symbol is defined inside the DLL's project, it won't be defined anywhere else
#define MYDLL_API __declspec(dllexport)
#else
#define MYDLL_API __declspec(dllimport)
#endif
//Now, prototype the functions.
MYDLL_API void someFunc();
MYDLL_API int someFunc(char c);
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Include this header file in the DLL's project and in any other projects that will use the functions inside the DLL.