diff --git a/version1.2/nasal_runtime.h b/version1.2/nasal_runtime.h
index b5d7b7f..67cd1dc 100644
--- a/version1.2/nasal_runtime.h
+++ b/version1.2/nasal_runtime.h
@@ -117,58 +117,10 @@ class var
 		}
 };
 
-class var_scope
-{
-	private:
-		std::list<var> var_list;
-	public:
-		var_scope()
-		{
-			var_list.clear();
-			var null_var;
-			std::string null_name_str="$";
-			null_var.set_name(null_name_str);
-			var_list.push_back(null_var);
-			return;
-		}
-		var_scope(const var_scope& p)
-		{
-			var_list=p.var_list;
-			return;
-		}
-		void add_var(var& tmp)
-		{
-			for(auto i=var_list.begin();i!=var_list.end();++i)
-				if(i->get_name()==tmp.get_name())
-				{
-					std::cout<<">>[Runtime-error] redeclaration of '"<<tmp.get_name()<<"'."<<std::endl;
-					return;
-				}
-			var_list.push_back(tmp);
-			return;
-		}
-		void del_latest_var()
-		{
-			var_list.pop_back();
-			return;
-		}
-		std::list<var>& get_list()
-		{
-			return var_list;
-		}
-		var& search_var(std::string& str)
-		{
-			for(auto i=var_list.begin();i!=var_list.end();++i)
-				if(i->get_name()==str)
-					return *i;
-			std::cout<<">>[Runtime-error] '"<<str<<"' is not delclared in this scope."<<std::endl;
-			return *var_list.begin();
-		}
-};
 class var_scope_manager
 {
 	private:
-		std::list<var_scope> scope_list;
+		std::list<std::list<var>> scope_list;
 		var error_var;
 	public:
 		var_scope_manager()
@@ -185,8 +137,8 @@ class var_scope_manager
 		}
 		var& search_var(std::string str)
 		{
-			for(std::list<var_scope>::iterator i=scope_list.begin();i!=scope_list.end();++i)
-				for(std::list<var>::iterator j=i->get_list().begin();j!=i->get_list().end();++j)
+			for(std::list<std::list<var>>::iterator i=scope_list.begin();i!=scope_list.end();++i)
+				for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
 					if(j->get_name()==str)
 						return *j;
 			std::cout<<">>[Runtime] could not find the var named '"<<str<<"' ."<<std::endl;
@@ -194,18 +146,18 @@ class var_scope_manager
 		}
 		void add_var(var new_var)
 		{
-			for(std::list<var_scope>::iterator i=scope_list.begin();i!=scope_list.end();++i)
-				for(std::list<var>::iterator j=i->get_list().begin();j!=i->get_list().end();++j)
+			for(std::list<std::list<var>>::iterator i=scope_list.begin();i!=scope_list.end();++i)
+				for(std::list<var>::iterator j=i->begin();j!=i->end();++j)
 					if(j->get_name()==new_var.get_name())
 					{
-						std::cout<<">>[Runtime] redefinition of var '"<<new_var.get_name()<<"' ."<<std::endl;
+						std::cout<<">>[Runtime] redeclaration of var '"<<new_var.get_name()<<"' ."<<std::endl;
 						return;
 					}
 			if(!scope_list.empty())
 			{
-				std::list<var_scope>::iterator i=scope_list.end();
+				std::list<std::list<var>>::iterator i=scope_list.end();
 				--i;
-				i->get_list().push_back(new_var);
+				i->push_back(new_var);
 			}
 			else
 				std::cout<<">>[Runtime] empty scope list."<<std::endl;
@@ -213,8 +165,8 @@ class var_scope_manager
 		}
 		void add_new_scope()
 		{
-			var_scope new_scope;
-			scope_list.push_back(new_scope);
+			std::list<var> new_list;
+			scope_list.push_back(new_list);
 			return;
 		}
 		void pop_last_scope()
@@ -231,6 +183,7 @@ class nasal_runtime
 {
 	private:
 		abstract_syntax_tree root;
+		var_scope_manager scope;
 	public:
 		nasal_runtime()
 		{
@@ -254,7 +207,7 @@ class nasal_runtime
 			std::cout<<">>[Runtime] runtime got the ast-root: "<<((void *)&tree)<<"->"<<((void *)&root)<<"."<<std::endl;
 			return;
 		}
-		var run_definition(abstract_syntax_tree& tree);
+		void run_definition(abstract_syntax_tree& tree);
 		void run_assignment(abstract_syntax_tree& tree);
 		void run_loop(abstract_syntax_tree& tree);
 		void run_if_else(abstract_syntax_tree& tree);
@@ -268,6 +221,7 @@ class nasal_runtime
 
 void nasal_runtime::run_root(abstract_syntax_tree& tree)
 {
+	scope.add_new_scope();
 	if(!tree.get_children().empty())
 	{
 		for(std::list<abstract_syntax_tree>::iterator i=tree.get_children().begin();i!=tree.get_children().end();++i)
@@ -316,29 +270,80 @@ void nasal_runtime::run_root(abstract_syntax_tree& tree)
 				case __number:
 				case __string:
 					scalar_call(*i);
-					return;
+					break;
 				default:
 					std::cout<<">>[Debug] error occurred."<<std::endl;
+					scope.pop_last_scope();
+					return;
 					break;
 			}
 		}
 	}
+	scope.pop_last_scope();
 	return;
 }
 
-var nasal_runtime::run_definition(abstract_syntax_tree& tree)
+void nasal_runtime::run_definition(abstract_syntax_tree& tree)
 {
 	var new_var;
 	std::list<abstract_syntax_tree>::iterator iter=tree.get_children().begin();
-	new_var.set_name(iter->get_var_name());
+	std::string var_name=iter->get_var_name();
 	++iter;
 	if(iter==tree.get_children().end())
 	{
 		new_var.set_type(__null_type);
-		
-		return new_var;
+		new_var.set_name(var_name);
+		scope.add_var(new_var);
+		return;
 	}
-	return new_var;
+	else
+	{
+		switch(iter->get_type())
+		{
+			case __add_operator:
+			case __sub_operator:
+			case __mul_operator:
+			case __div_operator:
+			case __link_operator:
+			case __and_operator:
+			case __or_operator:
+			case __nor_operator:
+			case __cmp_equal:
+			case __cmp_not_equal:
+			case __cmp_less:
+			case __cmp_less_or_equal:
+			case __cmp_more:
+			case __cmp_more_or_equal:
+				new_var=run_calculation(*iter);
+				break;
+			case __call_function:
+				new_var=run_function(*iter);
+				break;
+			case __id:
+			case __hash_search:
+			case __list_search:
+				new_var=identifier_call(*iter);
+				break;
+			case __number:
+			case __string:
+				new_var=scalar_call(*iter);
+				break;
+			case __function:
+				;
+				break;
+			case __list:
+				break;
+			case __hash:
+				break;
+			default:
+				std::cout<<">>[Debug] error occurred."<<std::endl;
+				return;
+				break;
+		}
+		new_var.set_name(var_name);
+		scope.add_var(new_var);
+	}
+	return;
 }
 void nasal_runtime::run_assignment(abstract_syntax_tree& tree)
 {
@@ -354,6 +359,9 @@ void nasal_runtime::run_if_else(abstract_syntax_tree& tree)
 }
 void nasal_runtime::run_block(abstract_syntax_tree& tree)
 {
+	scope.add_new_scope();
+	
+	scope.pop_last_scope();
 	return;
 }