RAND_file_name() generates a default path for the random seed
file. B<buf> points to a buffer of size B<num> in which to store the
-filename. The seed file is $RANDFILE if that environment variable is
-set, $HOME/.rnd otherwise. If $HOME is not set either, or B<num> is
+filename.
+
+On Windows the seed file is %RANDFILE% if that environment variable is set.
+Otherwise the file is called ".rnd" in one of the following locations (in order
+of preference): %TMP%, %TEMP%, %USERPROFILE%, %SYSTEMROOT%, %HOME%, "C:".
+
+On all other systems the seed file is $RANDFILE if that environment variable is
+set, $HOME/.rnd otherwise.
+
+If $HOME (on non Windows systems) is not set either, or B<num> is
too small for the path name, an error occurs.
RAND_load_file() reads a number of bytes from file B<filename> and