diff --git a/version2.0/main.cpp b/version2.0/main.cpp
index 46af052..f1769ca 100644
--- a/version2.0/main.cpp
+++ b/version2.0/main.cpp
@@ -3,6 +3,7 @@
 resource_file resource;
 nasal_lexer lexer;
 nasal_parse parser;
+nasal_symbol_table symtable;
 
 std::string command;
 
@@ -36,6 +37,7 @@ 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;
@@ -110,6 +112,29 @@ int main()
 			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());
+					if(!symtable.get_error())
+						symtable.print_symbol_table();
+					else
+						std::cout<<">>[Symbol] error occurred,stop."<<std::endl;
+				}
+				else
+					std::cout<<">>[Parse] error occurred,stop."<<std::endl;
+			}
+			else
+				std::cout<<">>[Lexer] error occurred,stop."<<std::endl;
+		}
 		else if(command=="run")
 		{
 			lexer.scanner(resource.get_source());
@@ -120,7 +145,12 @@ int main()
 				parser.main_generate();
 				if(!parser.get_error())
 				{
-					// run code
+					symtable.set_scope_clear();
+					symtable.symbol_table_main_generate(parser.get_root());
+					if(!symtable.get_error())
+						;// run code
+					else
+						std::cout<<">>[Symbol] error occurred,stop."<<std::endl;
 				}
 				else
 					std::cout<<">>[Parse] error occurred,stop."<<std::endl;
diff --git a/version2.0/nasal.h b/version2.0/nasal.h
index 944b54f..e4aefdc 100644
--- a/version2.0/nasal.h
+++ b/version2.0/nasal.h
@@ -11,10 +11,10 @@
 #include <stack>
 
 #include "numeral_misc.h"
-#include "nasal_scope.h"
 #include "nasal_enum.h"
 #include "abstract_syntax_tree.h"
 #include "nasal_lexer.h"
 #include "nasal_parse.h"
+#include "nasal_symbol_table.h"
 
 #endif
diff --git a/version2.0/nasal_parse.h b/version2.0/nasal_parse.h
index d6ac6dc..73d62de 100644
--- a/version2.0/nasal_parse.h
+++ b/version2.0/nasal_parse.h
@@ -166,7 +166,7 @@ int nasal_parse::get_error()
 
 abstract_syntax_tree& nasal_parse::get_root()
 {
-	std::cout<<">>[Abstract-syntax-tree] get root address: "<<(&root)<<" ."<<std::endl;
+	std::cout<<">>[Parse] output root address: "<<(&root)<<" ."<<std::endl;
 	return root;
 }
 
diff --git a/version2.0/nasal_symbol_table.h b/version2.0/nasal_symbol_table.h
new file mode 100644
index 0000000..93ae9d5
--- /dev/null
+++ b/version2.0/nasal_symbol_table.h
@@ -0,0 +1,217 @@
+#ifndef __NASAL_SYMBOL_TABLE_H__
+#define __NASAL_SYMBOL_TABLE_H__
+
+struct symbol_table_unit
+{
+    std::string symbol_name;
+    int symbol_number;
+    int symbol_line;
+    symbol_table_unit()
+    {
+        symbol_name="";
+        symbol_number=0;
+        symbol_line=-1;
+        return;
+    }
+    symbol_table_unit(const symbol_table_unit& tmp)
+    {
+        symbol_name=tmp.symbol_name;
+        symbol_number=tmp.symbol_number;
+        symbol_line=tmp.symbol_line;
+        return;
+    }
+    symbol_table_unit& operator=(const symbol_table_unit& tmp)
+    {
+        symbol_line=tmp.symbol_line;
+        symbol_name=tmp.symbol_name;
+        symbol_number=tmp.symbol_number;
+        return *this;
+    }
+};
+
+class nasal_symbol_table
+{
+    private:
+        int error;
+        std::list<symbol_table_unit> global_symbol_dictionary;
+        std::list<symbol_table_unit> global_scope;
+        std::list<symbol_table_unit> local_symbol_dictionary;
+        std::list<std::list<symbol_table_unit> > block_list;
+        void symbol_table_block_generate(abstract_syntax_tree&);
+    public:
+        nasal_symbol_table();
+        ~nasal_symbol_table();
+        void set_scope_clear();
+        void print_symbol_table();
+        void global_scope_add_symbol(symbol_table_unit);
+        void block_list_add_scope();
+        void block_list_del_scope();
+        void block_scope_add_symbol(symbol_table_unit);
+        int search_symbol_id(symbol_table_unit);
+        int get_error();
+        void symbol_table_main_generate(abstract_syntax_tree&);
+};
+
+nasal_symbol_table::nasal_symbol_table()
+{
+    error=0;
+    global_symbol_dictionary.clear();
+    global_scope.clear();
+    local_symbol_dictionary.clear();
+    block_list.clear();
+    return;
+}
+
+nasal_symbol_table::~nasal_symbol_table()
+{
+    error=0;
+    global_symbol_dictionary.clear();
+    global_scope.clear();
+    local_symbol_dictionary.clear();
+    block_list.clear();
+    return;
+}
+
+void nasal_symbol_table::set_scope_clear()
+{
+    error=0;
+    global_symbol_dictionary.clear();
+    global_scope.clear();
+    local_symbol_dictionary.clear();
+    block_list.clear();
+    return;
+}
+
+void nasal_symbol_table::print_symbol_table()
+{
+    if(!global_symbol_dictionary.empty())
+    {
+        std::cout<<">>[Symbol] global scope:"<<std::endl;
+        for(std::list<symbol_table_unit>::iterator i=global_symbol_dictionary.begin();i!=global_symbol_dictionary.end();++i)
+            std::cout<<"  line "<<i->symbol_line<<": "<<i->symbol_name<<"|"<<i->symbol_number<<std::endl;
+    }
+    else
+        std::cout<<">>[Symbol] empty global symbol list."<<std::endl;
+    if(!local_symbol_dictionary.empty())
+    {
+        std::cout<<">>[Symbol] local scope:"<<std::endl;
+        for(std::list<symbol_table_unit>::iterator i=local_symbol_dictionary.begin();i!=local_symbol_dictionary.end();++i)
+            std::cout<<"  line "<<i->symbol_line<<": "<<i->symbol_name<<"|"<<i->symbol_number<<std::endl;
+    }
+    else
+        std::cout<<">>[Symbol] empty local symbol list."<<std::endl;
+    return;
+}
+
+void nasal_symbol_table::global_scope_add_symbol(symbol_table_unit tmp)
+{
+    int symbol_number_gen=0;
+    for(std::list<symbol_table_unit>::iterator i=global_scope.begin();i!=global_scope.end();++i)
+    {
+        // this conditional expression is used to avoid wrong use of this function
+        if(i->symbol_name==tmp.symbol_name)
+            return;
+        symbol_number_gen=i->symbol_number;
+    }
+    tmp.symbol_number=symbol_number_gen+1;
+    global_scope.push_back(tmp);
+    global_symbol_dictionary.push_back(tmp);
+    return;
+}
+
+void nasal_symbol_table::block_list_add_scope()
+{
+    std::list<symbol_table_unit> new_scope;
+    block_list.push_back(new_scope);
+    return;
+}
+
+void nasal_symbol_table::block_list_del_scope()
+{
+    if(block_list.empty())
+    {
+        ++error;
+        std::cout<<">>[Symbol-error] fatal error: empty block_scope_list."<<std::endl;
+    }
+    else
+        block_list.pop_back();
+    return;
+}
+
+void nasal_symbol_table::block_scope_add_symbol(symbol_table_unit tmp)
+{
+    if(!block_list.empty())
+    {
+        int symbol_number_gen=0;
+        for(std::list<symbol_table_unit>::iterator i=block_list.back().begin();i!=block_list.back().end();++i)
+        {
+            // this conditional expression is used to avoid wrong use of this function
+            if(i->symbol_name==tmp.symbol_name)
+                return;
+            symbol_number_gen=i->symbol_number;
+        }
+        tmp.symbol_number=symbol_number_gen+1;
+        block_list.back().push_back(tmp);
+        local_symbol_dictionary.push_back(tmp);
+    }
+    else
+    {
+        ++error;
+        std::cout<<">>[Symbol-error] fatal error: empty block_scope_list."<<std::endl;
+    }
+    return;
+}
+
+int nasal_symbol_table::search_symbol_id(symbol_table_unit tmp)
+{
+    // in both global and local scope
+    // symbol_number begins with 1
+    int ret_number=-1;
+    if(!block_list.empty())
+        for(std::list<std::list<symbol_table_unit> >::iterator i=block_list.begin();i!=block_list.end();++i)
+            for(std::list<symbol_table_unit>::iterator j=i->begin();j!=i->end();++j)
+                if(j->symbol_name==tmp.symbol_name)
+                    ret_number=j->symbol_number;
+    if(ret_number==-1)
+        for(std::list<symbol_table_unit>::iterator i=global_scope.begin();i!=global_scope.end();++i)
+            if(i->symbol_name==tmp.symbol_name)
+                ret_number=i->symbol_number;
+    if(ret_number==-1)
+    {
+        ++error;
+        std::cout<<">>[Symbol-error] line "<<tmp.symbol_line<<": cannot find var named \'"<<tmp.symbol_name<<"\' ."<<std::endl;
+    }
+    return ret_number;
+}
+
+int nasal_symbol_table::get_error()
+{
+    return error;
+}
+
+void nasal_symbol_table::symbol_table_main_generate(abstract_syntax_tree& root)
+{
+    this->set_scope_clear();
+    for(std::list<abstract_syntax_tree>::iterator i=root.get_children().begin();i!=root.get_children().end();++i)
+    {
+        if(i->get_node_type()==__definition)
+        {
+            symbol_table_unit tmp;
+            tmp.symbol_line=i->get_children().front().get_node_line();
+            tmp.symbol_name=i->get_children().front().get_var_name();
+            this->global_scope_add_symbol(tmp);
+            this->symbol_table_block_generate(i->get_children().back());
+        }
+        else
+            this->symbol_table_block_generate(*i);
+    }
+    std::cout<<">>[Symbol] symbol table generating complete. "<<error<<" error(s)."<<std::endl;
+    return;
+}
+
+void nasal_symbol_table::symbol_table_block_generate(abstract_syntax_tree& node)
+{
+    return;
+}
+
+#endif
\ No newline at end of file