Description

   The dlopen function provides an interface to the dynamic library
   loader to allow shareable images to be loaded and called at run
   time.

   This function does not load a shareable image but rather saves
   its pathname argument for subsequent use by the dlsym function.
   dlsym is the function that actually loads the shareable image
   through a call to LIB$FIND_IMAGE_SYMBOL.

   The pathname argument of the dlopen function must be the name
   of the shareable image. This name is passed as-is by the dlsym
   function to the LIB$FIND_IMAGE_SYMBOL routine as the filename
   argument. No image-name argument is specified in the call
   to LIB$FIND_IMAGE_SYMBOL, so default file specification of
   SYS$SHARE:.EXE is applied to the image name.

   The dlopen function returns a handle that is used by a dlsym or
   dlclose call. If an error occurs, a NULL pointer is returned.