diff --git a/interpreter.cpp b/interpreter.cpp
new file mode 100644
index 0000000..d203650
--- /dev/null
+++ b/interpreter.cpp
@@ -0,0 +1,510 @@
+/*
+Grammar as follows:
+
+statement := 
+	| expression EOF
+	| VAR variable '=' expression EOF
+	| DEL variable EOF
+.
+
+expression :=
+	| term
+	| term '+' expression
+	| term '-' expression
+	| variable '=' expression
+.
+
+term := 
+	| atom
+	| atom '*' term
+	| atom '/' term
+.
+
+atom :=
+	| KEY '(' tuple ')'
+	| variable
+	| constant
+	| '(' expression ')'
+.
+
+tuple := 
+	| expression ',' tuple
+	| expression
+.
+
+variable :=
+	| [not spacial char]*
+.
+
+constant := 
+	| [0..9]*
+.
+
+EOF := 
+	| '\0'
+	| ';'
+
+*/
+#include"elliptic.h"
+#include<string.h>
+
+
+#define MAX_VAR 100000
+#define MAX_STR 1000
+
+
+lint global_p;
+
+char * TYPE[3] = {"num","felement","point"};
+char * KEY[10] = {"randomprime","modsqrt","modpower","select","mod","curve","remove","var"};
+
+typedef struct variable{
+	char * name;
+	int type,value,tag;
+	FPOINT * fvalue;
+	POINT * pvalue;
+	CURVE * c;
+}VAR;
+
+typedef struct valu{
+	int type;
+	int value;
+	FPOINT * fvalue;
+	POINT * pvalue;
+	CURVE * c;
+}VALU;
+
+char specialchar[30] = ".,\\{}[]()+-*/%$@#!?`~<>:|=^&\"";
+
+int CURRENT_VAR_NUM = 0;
+
+VAR * list[MAX_VAR];
+
+void statement(char * input, int header);
+
+VAR * expression(char * input, int start, int end);
+
+VAR * term(char * input, int start, int end);
+
+VAR * tuple(char * input, int start, int end);
+
+int MIN(int a,int b)
+{
+	return (a>b)?b:a;
+}
+
+int MAX(int a, int b)
+{
+	return (a>b)?a:b;
+}
+
+bool strcamp(char * a, char * b)
+{
+	int i = 0;
+	if(a==NULL || b==NULL)return false;
+	
+	while(i < MAX_STR){
+		if(a[i] != b[i])return false;
+		if(a[i] == '\0' && b[i] == '\0')return true;
+		i++;
+	}
+	return false;
+}
+
+char * substring(char * a, int start, int end)
+{
+	int i, len = strlen(a);
+	
+	end = MIN(end,len);
+	
+	if(end <= start)return NULL; 
+	
+	char * result = (char *)malloc((end-start)+2);
+	
+	for(i = start; i < MIN(len,end); i++){
+		result[i-start] = a[i];
+	}
+	
+	result[i-start] = '\0';
+	
+	return result;
+}
+
+
+
+VAR * findvariable(char * name)
+{
+	for(int i = 0;i < CURRENT_VAR_NUM; i++){
+		if(list[i]->tag== 1 && strcamp(name,list[i]->name))return list[i];
+	}
+	return NULL;
+}
+
+
+bool checknum(char c)
+{
+	if(c >= '0' && c <= '9')return true;
+	return false;
+}
+
+bool checkint(char * num)
+{
+	int len = strlen(num);
+	while(--len>=0){
+		if(!checknum(num[len]))return false;
+	}
+	return true;
+}
+
+lint parseint(char * num)
+{
+	lint len = strlen(num);
+	lint result = 0;
+	
+	if(len == 0 || len > 20)return 0;
+	
+	while(--len >= 0 && num[len] == '0');
+	
+	if(len < 0)return 0;
+	
+	result += num[len] - '0';
+	
+	while(--len >= 0){
+		result *= 10;
+		if(num[len] != '0')result += num[len] - '0';	
+	}
+	
+	return result;
+}
+
+int findavailablevariable()
+{
+	int i;
+	for(i = 0; i < CURRENT_VAR_NUM; i++){
+		if(list[i] != NULL && list[i]->tag == 0)break;
+	}
+	return i;
+}
+
+char * copystring(char * a)
+{
+	int len = strlen(a);
+	char * result = (char *)malloc(len+1);
+	result[len] = '\0';
+	while(--len >= 0)result[len] = a[len];
+	
+	return result;
+}
+
+bool putvariable(int type, char * name,lint value, FPOINT * fvalue, POINT * pvalue, CURVE * c)
+{
+	int i = findavailablevariable();
+	
+	if(i > MAX_VAR)return false;
+	
+	VAR * cu = list[i];
+	
+	if(cu == NULL)cu = (VAR *)malloc(sizeof(variable));
+	
+	cu->tag = 1;
+	cu->type = type;
+	
+	if(cu->name != NULL)free(cu->name);
+	if(cu->fvalue != NULL)free(cu->fvalue);
+	if(cu->pvalue != NULL)free(cu->pvalue);
+	if(cu->c != NULL)free(cu->c);
+	
+	cu->name = copystring(name);
+	
+	switch(type){
+		case 0:
+			cu->value = value;
+			cu->fvalue = NULL; cu->pvalue = NULL; cu->c = NULL;
+			break;
+		case 1:
+			cu->fvalue = fvalue;cu->pvalue = NULL;cu->c = NULL;
+			break;
+		case 2:
+			cu->fvalue = NULL;cu->pvalue = pvalue;cu->c = NULL;
+			break;
+		case 3:
+			cu->fvalue = NULL;cu->pvalue = pvalue;cu->c = c;
+		default:
+			break;
+	}
+	
+	CURRENT_VAR_NUM = i;
+	return true;
+}
+
+bool deletvariable(char * name)
+{
+	VAR * le = findvariable(name);
+	
+	if(le == NULL)return false;
+	
+	le->tag = 0;
+	
+	return true;
+}
+
+int checkkey(char * name)
+{
+	int i;
+	for(i = 0; i < 10; i++){
+		if(strcamp(name,KEY[i]))break;
+	}
+	return i;
+}
+
+bool transparentchar(char c)
+{
+	if(c == ' ' || c == '\t' || c == '\r' || c == '\n')return true;
+	return false;
+}
+
+bool isspacialchar(char c)
+{	
+	if(transparentchar(c))return true;
+	for(int i = 0;i < 30;i++){
+		if(c == specialchar[i])return true;
+	} 
+	return false;
+}
+
+int moveahead(char * input, int curren_head)
+{
+	int len = strlen(input);
+	
+	while(curren_head < len && transparentchar(input[curren_head++]));
+	
+	return curren_head - 1;
+}
+
+char * nextliteral(char * input, int curren_head, int * pos)
+{	
+	int len = strlen(input);
+	
+	int start = moveahead(input,curren_head);
+	
+	curren_head = start;
+	
+	while(curren_head <= len && !isspacialchar(input[curren_head++]));
+	
+	*pos = curren_head - 1;
+	
+	return substring(input,start,curren_head - 1);
+}
+
+int nexteof(char * input, int curren_head)
+{
+	while(input[curren_head] !=';' && input[curren_head++] !='\0');
+	return curren_head;
+}
+
+int nextchar(char * input, char c, int current_head)
+{
+	int len = strlen(input);
+	
+	while(current_head < len && input[current_head++] != c);
+	
+	if(input[current_head - 1] == c)return current_head - 1;
+	
+	return len;
+}
+
+void showvalue(VAR * v)
+{
+	if(v == NULL)return;
+	switch(v->type){
+		case 0:
+			printf("%lld\n",v->value);
+			break;
+		case 1:
+			printf("(%lld,%lld)\n",v->fvalue->x,v->fvalue->y);
+			break;
+		case 2:
+			printf("[(%lld,%lld),(%lld,%lld)]\n",v->pvalue->x->x,v->pvalue->x->y,v->pvalue->y->x,v->pvalue->y->y);
+			break;
+		case 3:
+			printf("Curve: y*y = x*x*x + %lld*x + %lld\n",v->c->A,v->c->B);
+			break;
+		default:
+			printf("unknow type.\n");
+	}
+}
+
+void statement(char * input, int header)
+{
+	int len = strlen(input);
+	VAR * newvar;
+	
+	if(len == 0){
+		return;
+	}
+	
+	header = moveahead(input,header);
+	if(header >= len){
+		return;
+	}
+	
+	if(checknum(input[header])){
+		int next = nextchar(input,';',header);
+		
+		newvar = expression(input,header,next);
+		
+		if(newvar == NULL){
+			statement(input,next+1);
+			return;
+		}
+		showvalue(newvar);
+		return;
+	}
+	
+	if(input[header] == ';'){
+		statement(input,header+1);
+		return;
+	}
+	
+	int next;
+	char * key = nextliteral(input,header,&next);
+	
+	if(strcamp(key,"var")){
+		
+		if(key != NULL)free(key);
+		key = nextliteral(input,next,&next);
+		next = moveahead(input,next);
+		
+		if(key == NULL){
+			printf("You should specify a name to the variable.\n");
+			return;
+		}
+		
+		if(checknum(key[0])){
+			printf("Variable should not start with an number.\n");
+			return;
+		}
+		
+		if(input[next] == '='){
+			if(findvariable(key) != NULL){
+				printf("Variable name '%s' has been use before, please specify a new one.\n",key);
+				if(key!=NULL)free(key);
+				return;
+			}
+			int end = nextchar(input,';',next);
+			newvar = expression(input,next,end);
+			
+			if(newvar == NULL){
+				printf("Can't build new variable beacause of nuknown expression value.\n");
+				free(key);
+				if(key!=NULL)free(key);
+				return;
+			}
+			putvariable(newvar->type,key,newvar->value,newvar->fvalue,newvar->pvalue,newvar->c);
+			free(key);
+			statement(input,end+1);
+			if(key!=NULL)free(key);
+			return;
+		}
+		printf("Error! You must specify the initial value when build a new variable.\n");
+		if(key!=NULL)free(key);
+		return;
+	}
+	
+	if(strcamp(key,"del")){
+		if(key != NULL)free(key);
+		key = nextliteral(input,next,&next);
+		next = moveahead(input,next);
+		
+		if(key == NULL){
+			printf("No variable been deleted.\n");
+			return;
+		}
+		
+		if(deletvariable(key)){
+			printf("%s has been deleted.\n",key);
+			int end = nextchar(input,';',next);
+			
+			statement(input,end);
+			
+			if(key!=NULL)free(key);
+			return;
+		}
+		printf("%s has not been defined yet.\n",key);
+		if(key!=NULL)free(key);
+		return;
+	}
+	
+}
+
+VAR * expression(char * input, int start,int end)
+{
+	//TODO
+	
+	return NULL;
+}
+
+void help()
+{
+	//TODO
+	
+	printf("No help currently.\n");
+}
+
+void init_system()
+{
+	system("cls");
+	printf("------------------------------------------------------------\n");
+	printf("    Welcome to use weil pairing demostration interpreter\n");
+	printf("------------------------------------------------------------\n");
+	printf("Version 2.7\n");
+	printf("Copyrigth (c) 2015. Wu Changlong<changlong1993@gmail.com>\n");
+	printf("\n");
+	printf("Hints:\n");
+	printf("1. type 'quit' to exit.\n");
+	printf("2. type 'clear' to clear the screen.\n");
+	printf("3. type 'reset' to set all the environment.\n");
+	printf("4. type 'help' to get the detailed help.\n");
+	printf("\n");
+}
+
+int main()
+{
+	char * worktap = (char *)malloc(MAX_STR);
+	char * token = NULL;
+	int pos;
+	
+	printf("------------------------------------------------------------\n");
+	printf("    Welcome to use weil pairing demostration interpreter\n");
+	printf("------------------------------------------------------------\n");
+	printf("Version 2.7\n");
+	printf("Copyrigth (c) 2015. Wu Changlong<changlong1993@gmail.com>\n");
+	printf("\n");
+	printf("Hints:\n");
+	printf("1. type 'quit' to exit.\n");
+	printf("2. type 'clear' to clear the screen.\n");
+	printf("3. type 'reset' to set all the environment.\n");
+	printf("4. type 'help' to get the detailed help.\n\n");
+	while(true){
+		printf("> ");
+		gets(worktap);
+		
+		if(token != NULL)free(token);
+		token = nextliteral(worktap,0,&pos);
+		
+		if(strcamp(token,"quit")||strcamp(token,"exit"))break;
+		if(strcamp(token,"help")){
+			help();
+		}else if(strcamp(token,"clear")){
+			system("cls");
+		}else if(strcamp(token,"reset")){
+			init_system();
+		}else
+			statement(worktap,0);
+	}
+	
+	free(worktap);
+	
+	return 0;
+}
+