-extern int startTicker( nat ms, TickProc handle_tick );
-extern int stopTicker ( void );
+#pragma GCC visibility push(hidden)
+
+typedef void (*TickProc)(int);
+
+void initTicker (nat ms, TickProc handle_tick);
+void startTicker (void);
+void stopTicker (void);
+void exitTicker (void);
+
+#pragma GCC visibility pop