diff --git a/version2.0/main.cpp b/version2.0/main.cpp
index f651301..8983f1e 100644
--- a/version2.0/main.cpp
+++ b/version2.0/main.cpp
@@ -5,8 +5,7 @@ nasal_lexer lexer;
 nasal_parse parser;
 abstract_syntax_tree libroot;
 abstract_syntax_tree root;
-
-nasal_symbol_table symtable;
+abstract_syntax_tree linker;
 
 std::string command;
 
@@ -40,7 +39,6 @@ int main()
 			std::cout<<">> [lex   ] turn code into tokens."<<std::endl;
 			std::cout<<">> [par   ] turn tokens into abstract syntax tree."<<std::endl;
 			std::cout<<">> [ast   ] check the abstract syntax tree."<<std::endl;
-			std::cout<<">> [sym   ] generate symbol table and print the information of it."<<std::endl;
 			std::cout<<">> [run   ] run code."<<std::endl;
 			std::cout<<">> [info  ] print lexer,parser and ast on screen."<<std::endl;
 			std::cout<<">> [exit  ] quit nasal interpreter."<<std::endl;
@@ -62,8 +60,8 @@ int main()
 			resource.delete_all_source();
 			lexer.delete_all_tokens();
 			parser.delete_all_elements();
-			symtable.set_scope_clear();
 			root.set_clear();
+			linker.set_clear();
 			std::cout<<">> [Delete] complete."<<std::endl;
 		}
 		else if(command=="lib")
@@ -82,14 +80,13 @@ int main()
 					std::cout<<">> [Lib] loaded."<<std::endl;
 				}
 				else
-					std::cout<<">> [Lib-error] lib files have parse error(s),stop."<<std::endl;
+					std::cout<<">> [Lib] lib files have parse error(s),stop."<<std::endl;
 			}
 			else
-				std::cout<<">> [Lib-error] lib files have lexer error(s),stop."<<std::endl;
+				std::cout<<">> [Lib] lib files have lexer error(s),stop."<<std::endl;
 			resource.delete_all_source();
 			lexer.delete_all_tokens();
 			parser.delete_all_elements();
-			symtable.set_scope_clear();
 		}
 		else if(command=="rs")
 		{
@@ -126,33 +123,7 @@ int main()
 				parser.get_token_list(lexer.get_detail_token_list());
 				parser.main_generate();
 				if(!parser.get_error())
-				{
-					symtable.set_scope_clear();
-					symtable.symbol_table_main_generate(parser.get_root());
 					parser.get_root().print_tree();
-				}
-				else
-					std::cout<<">> [Parse] error occurred,stop."<<std::endl;
-			}
-			else
-				std::cout<<">> [Lexer] error occurred,stop."<<std::endl;
-		}
-		else if(command=="sym")
-		{
-			lexer.scanner(resource.get_source());
-			lexer.generate_detail_token();
-			if(!lexer.get_error())
-			{
-				parser.get_token_list(lexer.get_detail_token_list());
-				parser.main_generate();
-				if(!parser.get_error())
-				{
-					symtable.set_scope_clear();
-					symtable.symbol_table_main_generate(parser.get_root());
-					symtable.print_symbol_table();
-					if(symtable.get_error())
-						std::cout<<">> [Symbol] error occurred,stop."<<std::endl;
-				}
 				else
 					std::cout<<">> [Parse] error occurred,stop."<<std::endl;
 			}
@@ -169,12 +140,11 @@ int main()
 				parser.main_generate();
 				if(!parser.get_error())
 				{
-					symtable.set_scope_clear();
-					symtable.symbol_table_main_generate(parser.get_root());
-					if(!symtable.get_error())
-						root=parser.get_root();// run code
-					else
-						std::cout<<">> [Symbol] error occurred,stop."<<std::endl;
+					linker.set_clear();
+					linker=libroot;
+					linker.merge_children(parser.get_root());
+					root=linker;
+					root.print_tree();
 				}
 				else
 					std::cout<<">> [Parse] error occurred,stop."<<std::endl;
diff --git a/version2.0/nasal.h b/version2.0/nasal.h
index e4aefdc..46d3cef 100644
--- a/version2.0/nasal.h
+++ b/version2.0/nasal.h
@@ -9,12 +9,17 @@
 //#include <thread>
 #include <list>
 #include <stack>
+#include <vector>
+#include <map>
 
-#include "numeral_misc.h"
+#include "nasal_misc.h"
 #include "nasal_enum.h"
-#include "abstract_syntax_tree.h"
+#include "nasal_ast.h"
 #include "nasal_lexer.h"
 #include "nasal_parse.h"
-#include "nasal_symbol_table.h"
+#include "nasal_scalar.h"
+#include "nasal_gc.h"
+#include "nasal_sym.h"
+#include "nasal_runtime.h"
 
-#endif
+#endif
\ No newline at end of file
diff --git a/version2.0/nasal_ast.h b/version2.0/nasal_ast.h
new file mode 100644
index 0000000..7ed6026
--- /dev/null
+++ b/version2.0/nasal_ast.h
@@ -0,0 +1,223 @@
+#ifndef __NASAL_AST_H__
+#define __NASAL_AST_H__
+
+class abstract_syntax_tree
+{
+	private:
+		// basic elements
+		int line;
+		int node_type;
+		std::list<abstract_syntax_tree> children;
+
+		// is this node is a number|string|identifier node
+		// then the three elements below is of great use
+		// var_name is set for __id
+		double      var_number;
+		std::string var_string;
+		std::string var_name;
+	public:
+		/* basic */
+		abstract_syntax_tree();
+		abstract_syntax_tree(const abstract_syntax_tree&);
+		~abstract_syntax_tree();
+		abstract_syntax_tree& operator=(const abstract_syntax_tree&);
+		
+		/* main functions */
+		// print
+		void print_tree();
+		void print_tree_block(const int);
+
+		// set
+		void set_clear();
+		void set_node_line(const int);
+		void set_node_type(const int);
+		void set_var_number(std::string);
+		void set_var_string(std::string);
+		void set_var_name(std::string);
+		void add_children(abstract_syntax_tree);
+
+		// get
+		int         get_node_line();
+		int         get_node_type();
+		double      get_var_number();
+		std::string get_var_string();
+		std::string get_var_name();
+		std::list<abstract_syntax_tree>& get_children();
+
+		// merge
+		void merge_children(abstract_syntax_tree&);
+};
+
+abstract_syntax_tree::abstract_syntax_tree()
+{
+	node_type=__null_type;
+	line=0;
+	var_number=0;
+	var_string="";
+	var_name="";
+	children.clear();
+	return;
+}
+
+abstract_syntax_tree::abstract_syntax_tree(const abstract_syntax_tree& tmp)
+{
+	node_type=tmp.node_type;
+	line=tmp.line;
+	var_number=tmp.var_number;
+	var_string=tmp.var_string;
+	var_name=tmp.var_name;
+	children=tmp.children;
+	return;
+}
+
+abstract_syntax_tree::~abstract_syntax_tree()
+{
+	node_type=__null_type;
+	line=0;
+	var_number=0;
+	var_string.clear();
+	var_name.clear();
+	children.clear();
+	return;
+}
+
+abstract_syntax_tree& abstract_syntax_tree::operator=(const abstract_syntax_tree& tmp)
+{
+	node_type=tmp.node_type;
+	line=tmp.line;
+	var_number=tmp.var_number;
+	var_string=tmp.var_string;
+	var_name=tmp.var_name;
+	children.clear();
+	children=tmp.children;
+	return *this;
+}
+
+void abstract_syntax_tree::print_tree()
+{
+	std::cout<<">> [Abstract-syntax-tree] get tree root: "<<(this)<<""<<std::endl;
+	print_tree_block(1);
+	return;
+}
+
+void abstract_syntax_tree::print_tree_block(const int n)
+{
+	std::string __str="";
+	for(int i=0;i<n;++i)
+		__str+="| ";
+	std::cout<<__str;
+	print_parse_token(node_type);
+	switch(node_type)
+	{
+		case __number:  std::cout<<": "<<var_number;break;
+		case __string:  std::cout<<": "<<var_string;break;
+		case __id:
+		case __dynamic_id:
+		case __call_hash: std::cout<<": "<<var_name;break;
+		case __call_vector:
+		case __call_function: break;
+		default: break;
+	}
+	std::cout<<std::endl;
+	if(!children.empty())
+	{
+		for(std::list<abstract_syntax_tree>::iterator i=children.begin();i!=children.end();++i)
+			i->print_tree_block(n+1);
+	}
+	return;
+}
+
+void abstract_syntax_tree::set_clear()
+{
+	node_type=__null_type;
+	line=0;
+	var_number=0;
+	var_string="";
+	var_name="";
+	children.clear();
+	return;
+}
+
+void abstract_syntax_tree::set_node_type(const int __node_type)
+{
+	node_type=__node_type;
+	return;
+}
+
+void abstract_syntax_tree::set_node_line(const int __line)
+{
+	if(__line>=0)
+		line=__line;
+	else
+	{
+		std::cout<<">> [Abstract-syntax-tree-warning] incorrect line under 0: "<<__line<<"."<<std::endl;
+		line=0;
+	}
+	return;
+}
+
+void abstract_syntax_tree::set_var_string(std::string __str)
+{
+	var_string=__str;
+	return;
+}
+
+void abstract_syntax_tree::set_var_number(std::string __str)
+{
+	var_number=trans_string_to_number(__str);
+	return;
+}
+
+void abstract_syntax_tree::set_var_name(std::string __str)
+{
+	var_name=__str;
+	return;
+}
+
+void abstract_syntax_tree::add_children(abstract_syntax_tree p)
+{
+	// use abstract_syntax_tree instead of abstract_syntax_tree&
+	// because when this function get a 'p' from returned value of
+	// another function,this may result in s SIGSEGV.
+	children.push_back(p);
+	return;
+}
+
+int abstract_syntax_tree::get_node_type()
+{
+	return node_type;
+}
+
+int abstract_syntax_tree::get_node_line()
+{
+	return line;
+}
+
+double abstract_syntax_tree::get_var_number()
+{
+	return var_number;
+}
+
+std::string abstract_syntax_tree::get_var_string()
+{
+	return var_string;
+}
+
+std::string abstract_syntax_tree::get_var_name()
+{
+	return var_name;
+}
+
+std::list<abstract_syntax_tree>& abstract_syntax_tree::get_children()
+{
+	return children;
+}
+
+void abstract_syntax_tree::merge_children(abstract_syntax_tree& tmp)
+{
+	for(std::list<abstract_syntax_tree>::iterator i=tmp.children.begin();i!=tmp.children.end();++i)
+		this->children.push_back(*i);
+	return;
+}
+
+#endif
\ No newline at end of file
diff --git a/version2.0/nasal_gc.h b/version2.0/nasal_gc.h
new file mode 100644
index 0000000..cea2723
--- /dev/null
+++ b/version2.0/nasal_gc.h
@@ -0,0 +1,143 @@
+#ifndef __NASAL_GC_H__
+#define __NASAL_GC_H__
+
+struct gc_unit
+{
+	// collected: If gc collected this item,it'll be set to true.Otherwise it is false.
+	// elem:      Item that this unit stores
+	// refcnt:    Reference counter
+	bool collected;
+	nasal_scalar elem;
+	int refcnt;
+	gc_unit()
+	{
+		collected=true;
+		//elem=0;
+		refcnt=0;
+		return;
+	}
+	gc_unit(const gc_unit& tmp)
+	{
+		collected=tmp.collected;
+		//elem=tmp.elem;
+		refcnt=tmp.refcnt;
+		return;
+	}
+};
+
+class gc_manager
+{
+	private:
+		// free_space list is used to store space that is not in use.
+		std::list<int> free_space;
+		std::vector<gc_unit> memory;
+	public:
+		gc_manager()
+		{
+			memory.clear();
+			free_space.clear();
+			return;
+		}
+		~gc_manager()
+		{
+			memory.clear();
+			free_space.clear();
+			return;
+		}
+		void gc_init()
+		{
+			// this function must be called in class nasal_runtime
+			// before running any codes
+			std::vector<gc_unit> tmp_vec;
+			memory.clear();
+			memory.swap(tmp_vec);
+			// clear the memory capacity by using tmp_vec.~vector<gc_unit>()
+			free_space.clear();
+			return;
+		}
+		void gc_scanner()
+		{
+			int memory_size=memory.size();
+			for(int i=0;i<memory_size;++i)
+				if((memory[i].refcnt<=0) && (!memory[i].collected))
+				{
+					memory[i].collected=true;
+					free_space.push_back(i);
+					std::cout<<">> [Gc] collected ";
+					prt_hex(i);
+					std::cout<<"."<<std::endl;
+				}
+			return;
+		}
+		int gc_alloc()
+		{
+			if(free_space.empty())
+			{
+				gc_unit new_unit;
+				memory.push_back(new_unit);
+				free_space.push_back(memory.size()-1);
+			}
+			int alloc_plc=free_space.front();
+			free_space.pop_front();
+			memory[alloc_plc].collected=false;
+			memory[alloc_plc].refcnt=1;
+			return alloc_plc;
+		}
+		bool place_check(const int place)
+		{
+			// check if this place is in memory
+			// and this place is uncollected
+			return (place<memory.size()) && (!memory[place].collected);
+		}
+		void reference_add(const int place)
+		{
+			if(place<memory.size())
+				++memory[place].refcnt;
+			else
+			{
+				std::cout<<">> [Gc] fatal error: unexpected memory place ";
+				prt_hex(place);
+				std::cout<<" ."<<std::endl;
+			}
+			return;
+		}
+		void reference_delete(const int place)
+		{
+			if(place<memory.size())
+				--memory[place].refcnt;
+			else
+			{
+				std::cout<<">> [Gc] fatal error: unexpected memory place ";
+				prt_hex(place);
+				std::cout<<" ."<<std::endl;
+			}
+			return;
+		}
+		void info_print()
+		{
+			std::cout<<">> [Gc] memory size:"<<memory.size()*sizeof(gc_unit)<<" byte."<<std::endl;
+			std::cout<<">> [Gc] memory capacity:"<<memory.capacity()*sizeof(gc_unit)<<" byte."<<std::endl;
+			std::cout<<">> [Gc] memory usage: "<<std::endl;
+			int cnt=0;
+			for(int i=0;i<memory.size();++i)
+				if(!memory[i].collected)
+				{
+					prt_hex(i);
+					std::cout<<"["<<memory[i].refcnt<<"]";
+					// cnt is used to check if it is the right time to output in the next line
+					++cnt;
+					if(!(cnt%8))
+						std::cout<<std::endl;
+					else
+						std::cout<<" ";
+				}
+			if(cnt%8)
+				std::cout<<std::endl;
+			return;
+		}
+};
+gc_manager nasal_gc;
+// this object is used in "nasal_sym.h" and "nasal_runtime.h"
+// because there must be only one gc when running a program
+
+#endif
diff --git a/version2.0/nasal_misc.h b/version2.0/nasal_misc.h
new file mode 100644
index 0000000..9677b05
--- /dev/null
+++ b/version2.0/nasal_misc.h
@@ -0,0 +1,168 @@
+#ifndef __NASAL_MISC_H__
+#define __NASAL_MISC_H__
+
+bool check_numerable_string(std::string str)
+{
+	if(str.length()>1 && str[0]=='-')
+	{
+		// in lexer this statements are useless
+		// because lexer judge a number that begins with 0~9 (or 0x for hex & 0o for oct)
+		std::string temp="";
+		int str_len=str.length();
+		for(int i=1;i<str_len;++i)
+			temp+=str[i];
+		str=temp;
+	}
+	if(str.length()==1 && '0'<=str[0] && str[0]<='9')
+		return true;
+	else if(str.length()>2 && str[0]=='0' && str[1]=='x')
+	{
+		int str_len=str.length();
+		for(int i=2;i<str_len;++i)
+			if(!(('0'<=str[i] && str[i]<='9') || ('a'<=str[i] && str[i]<='f') || ('A'<=str[i] && str[i]<='F')))
+				return false;
+		return true;
+	}
+	else if(str.length()>2 && str[0]=='0' && str[1]=='o')
+	{
+		int str_len=str.length();
+		for(int i=2;i<str_len;++i)
+			if(!('0'<=str[i] && str[i]<='7'))
+				return false;
+		return true;
+	}
+	else
+	{
+		int str_len=str.length();
+		int float_dot_cnt=0;
+		for(int i=0;i<str_len;++i)
+		{
+			if(str[i]=='.')
+				++float_dot_cnt;
+			else if(!('0'<=str[i] && str[i]<='9'))
+				return false;
+		}
+		if((float_dot_cnt>1) || (str[0]=='.') || (!float_dot_cnt && str[0]=='0'))
+			return false;
+		return true;
+	}
+	return false;
+}
+
+double trans_string_to_number(std::string str)
+{
+	bool is_negative=false;
+	if(str.length()>1 && str[0]=='-')
+	{
+		// in parse this statements are useless
+		// because lexer recognizes a number that begins with a '0'~'9' char
+		std::string temp="";
+		int str_len=str.length();
+		for(int i=1;i<str_len;++i)
+			temp+=str[i];
+		str=temp;
+		is_negative=true;
+	}
+	double trans_str_number=0;
+	if(str.length()==1)
+		trans_str_number=(double)(str[0]-'0');
+	else if(str[0]=='0' && str[1]=='x')
+	{
+		long long int hex_number=0,bit_pow=1;
+		for(int i=str.length()-1;i>1;--i)
+		{
+			if('0'<=str[i] && str[i]<='9')
+				hex_number+=bit_pow*(str[i]-'0');
+			else if('a'<=str[i] && str[i]<='f')
+				hex_number+=bit_pow*(10+str[i]-'a');
+			else
+				hex_number+=bit_pow*(10+str[i]-'A');
+			bit_pow<<=4;
+		}
+		trans_str_number=(double)hex_number;
+	}
+	else if(str[0]=='0' && str[1]=='o')
+	{
+		long long int oct_number=0,bit_pow=1;
+		for(int i=str.length()-1;i>1;--i)
+		{
+			oct_number+=bit_pow*(str[i]-'0');
+			bit_pow<<=3;
+		}
+		trans_str_number=(double)oct_number;
+	}
+	else
+	{
+		int float_dot_place=str.length();
+		int str_len=str.length();
+		double pow;
+		for(int i=0;i<str_len;++i)
+			if(str[i]=='.')
+			{
+				float_dot_place=i;
+				break;
+			}
+		pow=0.1;
+		for(int i=float_dot_place+1;i<str_len;++i)
+		{
+			trans_str_number+=pow*(double(str[i]-'0'));
+			pow/=10;
+		}
+		pow=1;
+		for(int i=float_dot_place-1;i>=0;--i)
+		{
+			trans_str_number+=pow*(double(str[i]-'0'));
+			pow*=10;
+		}
+	}
+	if(is_negative)
+		trans_str_number*=-1;
+	return trans_str_number;
+}
+
+std::string trans_number_to_string(double number)
+{
+	std::string trans_num_string="";
+	if(number<0)
+	{
+		trans_num_string+='-';
+		number*=-1;
+	}
+	double integer_bit=1;
+	while(number>=integer_bit)
+		integer_bit*=10;
+	integer_bit/=10;
+	while(integer_bit!=0.1)
+	{
+		trans_num_string+=(char)('0'+(int(number/integer_bit)));
+		number-=(double)(int(number/integer_bit))*integer_bit;
+		integer_bit/=10;
+	}
+	if(number!=0)
+		trans_num_string+='.';
+	while(number!=0)
+	{
+		trans_num_string+=(char)('0'+int(number*10));
+		number*=10;
+		number-=(double)(int(number));
+	}
+	return trans_num_string;
+}
+
+void prt_hex(const int ptr)
+{
+	// transform int to hex and print it (std::cout)
+	char hex[9];
+	hex[8]=0;
+	int tmp_plc=ptr;
+	for(int j=7;j>=0;--j)
+	{
+		int tmp=(tmp_plc & 0x0000000f);
+		hex[j]=tmp<10? (char)('0'+tmp):(char)('a'+tmp-10);
+		tmp_plc>>=4;
+	}
+	std::cout<<"0x"<<hex;
+	return;
+}
+
+#endif
diff --git a/version2.0/nasal_runtime.h b/version2.0/nasal_runtime.h
new file mode 100644
index 0000000..e9d43dd
--- /dev/null
+++ b/version2.0/nasal_runtime.h
@@ -0,0 +1,33 @@
+#ifndef __NASAL_RUNTIME_H__
+#define __NASAL_RUNTIME_H__
+
+class nasal_runtime
+{
+    private:
+        sym_hash_map global;
+    public:
+        nasal_runtime()
+        {
+            global.set_clear();
+            nasal_gc.gc_init();
+            return;
+        }
+        ~nasal_runtime()
+        {
+            global.set_clear();
+            nasal_gc.gc_init();
+            return;
+        }
+        void before_running_init()
+        {
+            global.set_clear();
+            nasal_gc.gc_init();
+            return;
+        }
+        void main_proc(abstract_syntax_tree& root)
+        {
+            return;
+        }
+};
+
+#endif
\ No newline at end of file
diff --git a/version2.0/nasal_scalar.h b/version2.0/nasal_scalar.h
index ab9c967..ddf711c 100644
--- a/version2.0/nasal_scalar.h
+++ b/version2.0/nasal_scalar.h
@@ -1,14 +1,35 @@
 #ifndef __NASAL_SCALAR_H__
 #define __NASAL_SCALAR_H__
 
+class nasal_function
+{
+	private:
+		std::map<std::string,int> local_scope;
+		abstract_syntax_tree function_root;
+	public:
+		nasal_function()
+		{
+			local_scope.clear();
+			function_root.set_clear();
+			return;
+		}
+		~nasal_function()
+		{
+			local_scope.clear();
+			function_root.set_clear();
+			return;
+		}
+};
+
 class nasal_scalar
 {
 	private:
 		int type;
 		std::string var_string;
 		double var_number;
-		std::vector<nasal_scalar> var_array;
-		std::map<std::string,nasal_scalar> var_hash;
+		std::vector<int> var_array;
+		std::map<std::string,int> var_hash;
+		nasal_function var_func;
 	public:
 		nasal_scalar()
 		{
@@ -62,6 +83,19 @@ class nasal_scalar
 			var_string=tmp_str;
 			return;
 		}
+		void vector_add_new_member(const int addr)
+		{
+			var_array.push_back(addr);
+			return;
+		}
+		void hash_add_new_member(const std::string member_name,const int addr)
+		{
+			if(var_hash.find(member_name)!=var_hash.end())
+				std::cout<<">> [Runtime] "<<member_name<<" exists."<<std::endl;
+			else
+				var_hash[member_name]=addr;
+			return;
+		}
 		int get_type()          {return type;}
 		double get_number()     {return var_number;}
 		std::string get_string(){return var_string;}
diff --git a/version2.0/nasal_sym.h b/version2.0/nasal_sym.h
new file mode 100644
index 0000000..aa322d0
--- /dev/null
+++ b/version2.0/nasal_sym.h
@@ -0,0 +1,52 @@
+#ifndef __NASAL_SYM_H__
+#define __NASAL_SYM_H__
+
+// all symbol_map use a same gc system named nasal_gc
+// see detail of nasal_gc in "nasal_gc.h"
+class sym_hash_map
+{
+	private:
+		std::map<std::string,int> sym_map;
+	public:
+		sym_hash_map()
+		{
+			sym_map.clear();
+			return;
+		}
+		sym_hash_map(const sym_hash_map& tmp)
+		{
+			sym_map=tmp.sym_map;
+			for(std::map<std::string,int>::iterator i=sym_map.begin();i!=sym_map.end();++i)
+				nasal_gc.reference_add(i->second);
+			return;
+		}
+		~sym_hash_map()
+		{
+			for(std::map<std::string,int>::iterator i=sym_map.begin();i!=sym_map.end();++i)
+				nasal_gc.reference_delete(i->second);
+			sym_map.clear();
+			return;
+		}
+        void set_clear()
+        {
+            sym_map.clear();
+            return;
+        }
+		void add_new_symbol(std::string __sym_name)
+		{
+			if(sym_map.find(__sym_name)==sym_map.end())
+				sym_map[__sym_name]=nasal_gc.gc_alloc();
+			else
+				std::cout<<">> [Runtime] "<<__sym_name<<" exists."<<std::endl;
+			return;
+		}
+		int get_symbol_addr(std::string __sym_name)
+		{
+			if(sym_map.find(__sym_name)!=sym_map.end())
+				return sym_map[__sym_name];
+			else
+				return -1;
+		}
+};
+
+#endif
\ No newline at end of file