diff --git a/bin/.gitignore b/bin/.gitignore
new file mode 100644
index 0000000..2079672
--- /dev/null
+++ b/bin/.gitignore
@@ -0,0 +1,2 @@
+/Spreadsheet.class
+/SpreadsheetTest.class
diff --git a/bin/Spreadsheet.class b/bin/Spreadsheet.class
index 92b411f..e41e0fb 100644
Binary files a/bin/Spreadsheet.class and b/bin/Spreadsheet.class differ
diff --git a/bin/SpreadsheetTest.class b/bin/SpreadsheetTest.class
index e7086bd..6c97b19 100644
Binary files a/bin/SpreadsheetTest.class and b/bin/SpreadsheetTest.class differ
diff --git a/src/Spreadsheet.java b/src/Spreadsheet.java
index e4f120b..53aab48 100644
--- a/src/Spreadsheet.java
+++ b/src/Spreadsheet.java
@@ -1,18 +1,87 @@
+import java.util.HashMap;
 
 public class Spreadsheet {
+	
+	static HashMap<String, String> hashMap = new HashMap<String, String>();
 
-	public String get(String cell) {
-		// to be implemented
-		return null;
+	public static String get(String cell) {
+		String value = hashMap.get(cell);
+		return value;
 	}
 	
 	public void set(String cell, String value) {
-		// to be implemented
+		hashMap.put(cell,value);
 	}
 	
 	public String evaluate(String cell) {
-		// to be implemented
-		return null;
+		String value = hashMap.get(cell);
+		int i = 0;
+		int j = value.length()-1; // j=2
+		//first char is "=" 
+		if(value.charAt(i)=='='){
+			//second or last char is "'"
+			if(value.charAt(i+1)=='\'' || value.charAt(value.length()-1)=='\''){
+				//second and last chars are both "'"
+				if(value.charAt(i+1)=='\'' && value.charAt(value.length()-1)=='\''){
+					//return chars between ''
+					return value.substring(2, value.length()-1);
+				}
+				//one of second and last char is not "'"
+				else
+					//return error
+					return "#Error";
+			}
+			//chars after "=" can be found in other cells
+			else if(hashMap.containsKey(value.substring(1,value.length()))){
+				//find its value in next cells
+				while(hashMap.containsKey(value.substring(1,value.length()))){
+					//this value become next cell to be found
+					value = hashMap.get(value.substring(1,value.length()));
+					//circular
+					if(value.substring(1,value.length()).equals(cell))
+						return "#Circular";
+					//value of this cell doesn't start with a "="
+					else if(value.charAt(i) != '='){
+						//value of this cell start or end with a "'"
+						if(value.charAt(i)=='\'' || value.charAt(value.length()-1)=='\''){
+							//first and last chars are both "'"
+							if(value.charAt(i)=='\'' && value.charAt(value.length()-1)=='\''){
+								//return chars between ''
+								return value.substring(1, value.length()-1);
+							}
+							//one of second and last char is not "'"
+							else
+								//return error
+								return "#Error";			
+						}
+						//value doesn't start with a "'"
+						else
+							//check every char in value
+							for(i=0;i<value.length();i++){
+								//there are illegal char in value
+								if( !(value.charAt(i)>='0' && value.charAt(i)<='9' || value.charAt(i)=='-'))
+									//return error
+									return "#Error";
+							}		
+						//there isn't illegal char in value
+						return value;
+					}
+				}
+			}
+			//including calculating
+			else
+				return value.substring(1, j);		
+		}
+		else if(value.charAt(i)=='\'' && value.charAt(j)=='\'')
+			return value.substring(1, j);
+		else if((value.charAt(i)=='\'' && value.charAt(j)!='\'') || (value.charAt(i)!='\'' && value.charAt(j)=='\''))
+			return "#Error";
+		else
+			for(i=0;i<value.length();i++){
+				if(! (value.charAt(i)>='0' && value.charAt(i)<='9' || value.charAt(i)=='-'))
+					return "#Error";
+			}
+		return value;
 	}
 	
 }
diff --git a/tests/SpreadsheetTest.java b/tests/SpreadsheetTest.java
index 9e0936a..41e6715 100644
--- a/tests/SpreadsheetTest.java
+++ b/tests/SpreadsheetTest.java
@@ -5,11 +5,89 @@
 
 
 public class SpreadsheetTest {
+	
+	Spreadsheet s = new Spreadsheet();
 
 	@Test
-	public void test() {
-		fail("Not yet implemented");
-		
+	public void test_1() {
+		s.set("A1","1");
+		String result = s.get("A1");
+		assertEquals("1",result);
 	}
+	
+	@Test
+	public void test_2() {
+		s.set("A1","-1");
+		String result = s.evaluate("A1");
+		assertEquals("-1",result);
+	}
+	
+	@Test
+	public void test_3() {
+		s.set("A1","5A");
+		String result = s.evaluate("A1");
+		assertEquals("#Error",result);
+	}
+	
+	@Test
+	public void test_4() {
+		s.set("A1","'a string'");
+		String result = s.evaluate("A1");
+		assertEquals("a string",result);
+	}
+	
+	@Test
+	public void test_5() {
+		s.set("A1","'a string");
+		String result = s.evaluate("A1");
+		assertEquals("#Error",result);
+	}
+	
+	@Test
+	public void test_6() {
+		s.set("A1","='a string'");
+		String result = s.evaluate("A1");
+		assertEquals("a string",result);
+	}
+	
+	@Test
+	public void test_7() {
+		s.set("A1","='a string");
+		String result = s.evaluate("A1");
+		assertEquals("#Error",result);
+	}
+	
+	@Test
+	public void test_8() {
+		s.set("A5","5");
+		s.set("A1","=A5");
+		String result = s.evaluate("A1");
+		assertEquals("5",result);
+	}
+	
+	@Test
+	public void test_9() {
+		s.set("A5","5A");
+		s.set("A1","=A5");
+		String result = s.evaluate("A1");
+		assertEquals("#Error",result);
+	}
+	
+	@Test
+	public void test_10() {
+		s.set("A5","=A1");
+		s.set("A1","=A5");
+		String result = s.evaluate("A1");
+		assertEquals("#Circular",result);
+	}
+	
+	@Test
+	public void test_11() {
+		s.set("A1","=1+1*2");
+		String result = s.evaluate("A1");
+		assertEquals("4",result);
+	}
+
+
 
 }