diff --git a/README.md b/README.md
index 80c9f9c..646aed0 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 `cytolib` provides the c++ headers for users to use and interact with the `GatingSet` (the gated cytometry data structure) at c++ level.
 
-
+###Installation
 The **cytolib** package is installed via `R CMD INSTALL ...`. 
 
 R packages wishing to use the libraries in `cytolib` only need to:
@@ -13,5 +13,7 @@ e.g.
 ```
 LinkingTo: cytolib
 ```
+###Usage
+Make sure to call `CYTOLIB_INIT()` in user c code
 
 See **flowWorkspace** package for the example of using `cytolib`.
diff --git a/inst/include/cytolib/global.hpp b/inst/include/cytolib/global.hpp
index 63363ad..087e740 100644
--- a/inst/include/cytolib/global.hpp
+++ b/inst/include/cytolib/global.hpp
@@ -13,8 +13,6 @@
 #define POPULATION_LEVEL 3
 #define GATE_LEVEL 4
 
-extern unsigned short g_loglevel;
-extern bool my_throw_on_error;
 
 #ifdef ROUT
 #include <R_ext/Print.h>
@@ -29,6 +27,9 @@ using namespace std;
 
 extern unsigned short g_loglevel;// debug print is turned off by default
 extern bool my_throw_on_error;//can be toggle off to get a partially parsed gating tree for debugging purpose
+#define CYTOLIB_INIT() \
+		bool my_throw_on_error = true;\
+		unsigned short g_loglevel = 0;\
 
 inline void PRINT(string a){
 #ifdef ROUT