diff --git a/interpreter_lab.cpp b/interpreter_lab.cpp
new file mode 100644
index 0000000..656dedc
--- /dev/null
+++ b/interpreter_lab.cpp
@@ -0,0 +1,41 @@
+#include <iostream>
+#include "process_stack.h"
+#include "lexer.h"
+using namespace std;
+using namespace nasal;
+
+int main()
+{
+	
+	_unit.line=1;
+	_unit.type="function";
+	_unit.Name="__main()";
+	_unit.unitdata.Type="string";
+	_unit.unitdata.data=new std::string;
+	*((std::string *)_unit.unitdata.data)="in function main.";
+	_unit.global=true;
+	_test.stack_append(_unit);
+	
+	_unit.line=2;
+	_unit.type="int";
+	_unit.Name="NewInt";
+	_unit.global=true;
+	_unit.unitdata.Type="int";
+	_unit.unitdata.data=new int;
+	*((int *)_unit.unitdata.data)=2147483647;
+	_test.stack_append(_unit);
+	
+	_unit.line=3;
+	_unit.type="int";
+	_unit.Name="ptr";
+	_unit.global=true;
+	_unit.unitdata.Type="int";
+	*((int *)_unit.unitdata.data)=1073741824;
+	_test.stack_append(_unit);
+	//_test.stack_print(true);
+	_test.stack_print(false);
+	
+	
+	CommandProcess();
+	return 0;
+}
diff --git a/lexer.h b/lexer.h
new file mode 100644
index 0000000..d5cb091
--- /dev/null
+++ b/lexer.h
@@ -0,0 +1,183 @@
+#ifndef __LEXER_H__
+#define __LEXER_H__
+
+
+#include <iostream>
+#include <fstream>
+#include <cstring>
+#include "nasal.h"
+#include "process_stack.h"
+
+using namespace nasal;
+
+std::string text;
+process_stack _test;
+process_stack_unit _unit;
+
+void PrintProcess(std::string content)
+{
+	std::string Sentence="";
+	int len=(int)content.length();
+	for(int i=0;i<len;++i)
+	{
+		if(content[i]==',')
+			Sentence="";
+		else if(content[i]=='\"')//string mode
+		{
+			Sentence="";
+			for(int j=i+1;j<len;++j)
+			{
+				if(content[j]=='\\' && j+1<len)
+				{
+					Sentence+=content[j];
+					Sentence+=content[j+1];
+					++j;
+				}
+				else if(content[j]=='\"')
+				{
+					i=j;
+					break;
+				}
+				else
+					Sentence+=content[j];
+			}
+			PrintString(Sentence);
+		}
+		else if(content[i]!=' ' && content[i]!='\"' && content[i]!=',')//check var
+		{
+			Sentence="";
+			for(int j=i;j<len;++j)
+			{
+				if(content[j]!=' ' && content[j]!='\"' && content[j]!=',')
+					Sentence+=content[j];
+				if(content[j]==',' || content[j]==' ' || j==len-1)
+				{
+					i=j;
+					break;
+				}
+			}
+			if(_test.check_stack(Sentence))
+			{
+				_test.stack_content_print(Sentence);
+			}
+			else
+				std::cout<<std::endl<<"[Error] "<<Sentence<<" is not declared in this scope."<<std::endl;
+		}
+	}
+	std::cout<<std::endl;
+	return;
+}
+
+void FileProcess(const char *FileName)
+{
+	std::ifstream fin(FileName);
+	
+	fin.close();
+	return;
+}
+
+void CommandProcess()
+{
+	while(1)
+	{
+		std::cout<<">> ";
+		std::getline(std::cin,text);
+		int len=(int)text.length();
+		
+		int sharpDetected=0;
+		for(int i=len-1;i>=0;--i)
+		{
+			if(text[i]=='#')
+			{
+				//ignore sharp
+				len=i;
+				sharpDetected=i;
+			}
+			if(text[i]==';')
+			{
+				len=i+1;
+				//find the real end of the sentence
+				if(sharpDetected)
+				{
+					for(int j=sharpDetected-1;j>=len;--j)
+						if(text[j]!=' ')
+						{
+							len=j+1;
+							break;
+						}
+				}
+				else
+				{
+					for(int j=(int)text.length()-1;j>=len;--j)
+						if(text[j]!=' ')
+						{
+							len=j+1;
+							break;
+						}
+				}
+				break;
+			}
+		}
+		
+		if(text[len-1]==';')
+		{
+			for(int i=0;i<len;++i)
+			{
+				if(text[i]=='p' && i+1<len && text[i+1]=='r' && i+2<len && text[i+2]=='i' && i+3<len && text[i+3]=='n' && i+4<len && text[i+4]=='t')
+				{
+					//In this part every error leads to an error information and breaks the loop!
+					
+					//check the first char after print is '(' or not
+					int string_beg=len-1;
+					for(int j=i+5;j<len;++j)
+						if(text[j]!=' ')
+						{
+							string_beg=j;
+							break;
+						}
+						
+					if(text[string_beg]!='(')
+					{
+						std::cout<<std::endl<<"[Error] Missing \'(\' ."<<std::endl;
+						break;
+					}
+					
+					//check the ')' and the place 
+					int string_end=len-1;
+					for(int j=len-2;j>=0;--j)
+						if(text[j]!=' ')
+						{
+							string_end=j;
+							break;
+						}
+					if(text[string_end]!=')')
+					{
+						std::cout<<std::endl<<"[Error] Missing \')\' ."<<std::endl;
+						break;
+					}
+					
+					std::string content="";
+					for(int j=string_beg+1;j<string_end;++j)
+						content+=text[j];
+					
+					std::cout<<std::endl<<"Target string: "<<content<<std::endl;
+					PrintProcess(content);
+					break;
+				}
+				else if(text[i]=='v' && i+1<len && text[i+1]=='a' && i+2<len && text[i+2]=='r')
+				{
+					;
+				}
+				else if(i==len-1)
+					std::cout<<std::endl<<"[Error] Incorrect command."<<std::endl;
+			}
+		}
+		else
+		{
+			std::cout<<std::endl<<"[Error] Expected \';\' after this line."<<std::endl;
+		}
+	}
+	return;
+}
+
+#endif
diff --git a/nasal_list.cpp b/nasal_list.cpp
index 180d8aa..820f1f6 100644
--- a/nasal_list.cpp
+++ b/nasal_list.cpp
@@ -378,19 +378,19 @@ NasalList& NasalList::operator=(const NasalList &Source)
 	{
 		if(temp->Type=="int")
 			delete (int *)temp->data;
-		if(temp->Type=="float")
+		else if(temp->Type=="float")
 			delete (float *)temp->data;
-		if(temp->Type=="double")
+		else if(temp->Type=="double")
 			delete (double *)temp->data;
-		if(temp->Type=="char")
+		else if(temp->Type=="char")
 			delete (char *)temp->data;
-		if(temp->Type=="long long int")
+		else if(temp->Type=="long long int")
 			delete (long long int *)temp->data;
-		if(temp->Type=="string")
+		else if(temp->Type=="string")
 			delete (std::string *)temp->data;
-		if(temp->Type=="array")
+		else if(temp->Type=="array")
 			delete (NasalList *)temp->data;
-		if(temp->Type=="hash")
+		else if(temp->Type=="hash")
 			delete (NasalHash *)temp->data;
 	}
 	delete temp;
@@ -819,6 +819,51 @@ NasalList NasalList::Sort(const int SortType,const int _cmp)
 	return TempList;
 }
 
+var::var(var &p)
+{
+	Type=p.Type;
+	if(Type=="int")
+	{
+		data=new int;
+		*((int *)data)=*((int *)p.data);
+	}
+	else if(Type=="float")
+	{
+		data=new float;
+		*((float *)data)=*((float *)p.data);
+	}
+	else if(Type=="double")
+	{
+		data=new double;
+		*((double *)data)=*((double *)p.data);
+	}
+	else if(Type=="char")
+	{
+		data=new char;
+		*((char *)data)=*((char *)p.data);
+	}
+	else if(Type=="long long int")
+	{
+		data=new long long int;
+		*((long long int *)data)=*((long long int *)p.data);
+	}
+	else if(Type=="string")
+	{
+		data=new std::string;
+		*((std::string *)data)=*((std::string *)p.data);
+	}
+	else if(Type=="array")
+	{
+		data=new NasalList;
+		*((NasalList *)data)=*((NasalList *)p.data);
+	}
+	else if(Type=="hash")
+	{
+		data=new NasalHash;
+		*((NasalHash *)data)=*((NasalHash *)p.data);
+	}
+}
+
 var::~var()
 {
 	if(data)
@@ -842,6 +887,91 @@ var::~var()
 	}
 }
 
+var& var::operator=(const var &p)
+{
+	if(data)
+	{
+		if(Type=="int")
+			delete (int *)data;
+		else if(Type=="float")
+			delete (float *)data;
+		else if(Type=="double")
+			delete (double *)data;
+		else if(Type=="char")
+			delete (char *)data;
+		else if(Type=="long long int")
+			delete (long long int *)data;
+		else if(Type=="string")
+			delete (std::string *)data;
+		else if(Type=="array")
+			delete (NasalList *)data;
+		else if(Type=="hash")
+			delete (NasalHash *)data;
+	}
+	Type=p.Type;
+	if(Type=="int")
+	{
+		data=new int;
+		*((int *)data)=*((int *)p.data);
+	}
+	else if(Type=="float")
+	{
+		data=new float;
+		*((float *)data)=*((float *)p.data);
+	}
+	else if(Type=="double")
+	{
+		data=new double;
+		*((double *)data)=*((double *)p.data);
+	}
+	else if(Type=="char")
+	{
+		data=new char;
+		*((char *)data)=*((char *)p.data);
+	}
+	else if(Type=="long long int")
+	{
+		data=new long long int;
+		*((long long int *)data)=*((long long int *)p.data);
+	}
+	else if(Type=="string")
+	{
+		data=new std::string;
+		*((std::string *)data)=*((std::string *)p.data);
+	}
+	else if(Type=="array")
+	{
+		data=new NasalList;
+		*((NasalList *)data)=*((NasalList *)p.data);
+	}
+	else if(Type=="hash")
+	{
+		data=new NasalHash;
+		*((NasalHash *)data)=*((NasalHash *)p.data);
+	}
+	return *this;
+}
+
+void var::Print()
+{
+	if(Type=="int")
+		std::cout<<*((int *)data);
+	else if(Type=="float")
+		std::cout<<*((float *)data);
+	else if(Type=="double")
+		std::cout<<*((double *)data);
+	else if(Type=="char")
+		std::cout<<*((char *)data);
+	else if(Type=="long long int")
+		std::cout<<*((long long int *)data);
+	else if(Type=="string")
+		std::cout<<*((std::string *)data);
+	else if(Type=="array")
+		(*((NasalList *)data)).PrintList();
+	else if(Type=="hash")
+		(*((NasalHash *)data)).PrintHash();
+}
+
 }
 
 #endif
diff --git a/nasal_list.h b/nasal_list.h
index 06df4db..bc2ef3b 100644
--- a/nasal_list.h
+++ b/nasal_list.h
@@ -47,7 +47,10 @@ class var
 		{
 			data=NULL;
 		}
+		var(var &);
 		~var();
+		var& operator=(const var &);
+		void Print();
 };
 
 }
diff --git a/process_stack.h b/process_stack.h
index 0a43628..5c14f97 100644
--- a/process_stack.h
+++ b/process_stack.h
@@ -11,8 +11,10 @@ namespace nasal
 struct process_stack_unit
 {
 	int line;           //place the unit first appear
-	std::string content;//content of the unit or name of the var/class/function
+	std::string Name;//content of the unit or name of the var/class/function
 	std::string type;   //var class function
+	var unitdata;
+	bool global;
 	process_stack_unit *next;
 	process_stack_unit *last;
 };
@@ -25,8 +27,15 @@ class process_stack
 	public:
 		process_stack()
 		{
+			head=new process_stack_unit;
 			head->line=0;
-			head->content="# Nasal language for FlightGear.";
+			head->Name="InterpreterInfo";
+			head->global=false;
+			head->type="information";
+			head->unitdata.Type="string";
+			head->unitdata.data=new std::string;
+			*((std::string *)head->unitdata.data)="# Nasal language for FlightGear.";
+			
 			head->last=NULL;
 			head->next=NULL;
 			ptr=NULL;
@@ -48,18 +57,67 @@ class process_stack
 			process_stack_unit *last_node;
 			while(temp->next)
 			{
-				if(!temp->next->next)
-					last_node=temp;
 				temp=temp->next;
 			}
-			if(temp==head)
-				last_node=head;
-			temp=new process_stack_unit;
+			temp->next=new process_stack_unit;
+			
+			last_node=temp;
+			temp=temp->next;
+			
 			temp->last=last_node;
+			last_node->next=temp;
 			temp->next=NULL;
-			temp->content=p.content;
-			temp->line=p.last;
+			
+			temp->Name=p.Name;
+			temp->line=p.line;
 			temp->type=p.type;
+			temp->global=p.global;
+			temp->unitdata=p.unitdata;
+			
+			return;
+		}
+		void stack_print(bool reverse_mode_used)
+		{
+			process_stack_unit *temp=head;
+			std::cout<<"In stack: "<<std::endl;
+			std::cout<<temp->line<<": |"<<temp->type<<"| \""<<temp->Name<<"\""<<std::endl;
+			while(temp->next)
+			{
+				temp=temp->next;
+				std::cout<<temp->line<<": |"<<temp->type<<"| \""<<temp->Name<<"\""<<std::endl;
+			}
+			if(reverse_mode_used)
+				while(temp->last)
+				{
+					std::cout<<temp->line<<": |"<<temp->type<<"| \""<<temp->Name<<"\""<<std::endl;
+					temp=temp->last;
+				}
+			std::cout<<"End."<<std::endl;
+			return;
+		}
+		bool check_stack(std::string &ElementName)
+		{
+			process_stack_unit *temp=head;
+			while(temp->next)
+			{
+				temp=temp->next;
+				if(temp->Name==ElementName)
+					return true;
+			}
+			return false;
+		}
+		void stack_content_print(std::string &ElementName)
+		{
+			process_stack_unit *temp=head;
+			while(temp->next)
+			{
+				temp=temp->next;
+				if(temp->Name==ElementName)
+				{
+					temp->unitdata.Print();
+					return;
+				}
+			}
 			return;
 		}
 };