diff --git a/src/seedu/addressbook/Main.java b/src/seedu/addressbook/Main.java
index dd9f9aa65..c47268f34 100644
--- a/src/seedu/addressbook/Main.java
+++ b/src/seedu/addressbook/Main.java
@@ -107,7 +107,10 @@ private CommandResult executeCommand(Command command)  {
         try {
             command.setData(addressBook, lastShownList);
             CommandResult result = command.execute();
-            storage.save(addressBook);
+            if (command.isMutating()) {
+                storage.save(addressBook);
+            }
+           
             return result;
         } catch (Exception e) {
             ui.showToUser(e.getMessage());
diff --git a/src/seedu/addressbook/commands/AddCommand.java b/src/seedu/addressbook/commands/AddCommand.java
index 7ed3cf359..224d648c1 100644
--- a/src/seedu/addressbook/commands/AddCommand.java
+++ b/src/seedu/addressbook/commands/AddCommand.java
@@ -58,7 +58,7 @@ public ReadOnlyPerson getPerson() {
     }
 
     @Override
-    public CommandResult execute() {
+    public CommandResult execute() throws Exception{
         try {
             addressBook.addPerson(toAdd);
             return new CommandResult(String.format(MESSAGE_SUCCESS, toAdd));
@@ -67,4 +67,9 @@ public CommandResult execute() {
         }
     }
 
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
+
 }
diff --git a/src/seedu/addressbook/commands/ClearCommand.java b/src/seedu/addressbook/commands/ClearCommand.java
index f1bafb8a2..a8acc9395 100644
--- a/src/seedu/addressbook/commands/ClearCommand.java
+++ b/src/seedu/addressbook/commands/ClearCommand.java
@@ -22,4 +22,11 @@ public CommandResult execute() {
         addressBook.clear();
         return new CommandResult(MESSAGE_SUCCESS);
     }
+
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return true;
+    }
 }
diff --git a/src/seedu/addressbook/commands/Command.java b/src/seedu/addressbook/commands/Command.java
index 2e4708de9..3464a4e31 100644
--- a/src/seedu/addressbook/commands/Command.java
+++ b/src/seedu/addressbook/commands/Command.java
@@ -38,8 +38,9 @@ protected String getMessageForPersonListShownSummary(List<? extends ReadOnlyPers
 
     /**
      * Executes the command and returns the result.
+     * @throws Exception 
      */
-    public abstract CommandResult execute();
+    public abstract CommandResult execute() throws Exception;
 
     /**
      * Supplies the data the command will operate on.
@@ -65,4 +66,6 @@ public int getTargetIndex() {
     public void setTargetIndex(int targetIndex) {
         this.targetIndex = targetIndex;
     }
+    
+    public abstract boolean isMutating();
 }
diff --git a/src/seedu/addressbook/commands/CommandResult.java b/src/seedu/addressbook/commands/CommandResult.java
index cf4e72585..9db652fb7 100644
--- a/src/seedu/addressbook/commands/CommandResult.java
+++ b/src/seedu/addressbook/commands/CommandResult.java
@@ -11,7 +11,7 @@
 public class CommandResult {
 
     /** The feedback message to be shown to the user. Contains a description of the execution result */
-    public final String feedbackToUser;
+    private final String feedbackToUser;
 
     /** The list of persons that was produced by the command */
     private final List<? extends ReadOnlyPerson> relevantPersons;
@@ -32,5 +32,9 @@ public CommandResult(String feedbackToUser, List<? extends ReadOnlyPerson> relev
     public Optional<List<? extends ReadOnlyPerson>> getRelevantPersons() {
         return Optional.ofNullable(relevantPersons);
     }
+    
+    public String getFeedbackToUser() {
+    	return feedbackToUser;
+    }
 
 }
diff --git a/src/seedu/addressbook/commands/DeleteCommand.java b/src/seedu/addressbook/commands/DeleteCommand.java
index 493d75da6..14ebf10cf 100644
--- a/src/seedu/addressbook/commands/DeleteCommand.java
+++ b/src/seedu/addressbook/commands/DeleteCommand.java
@@ -39,4 +39,11 @@ public CommandResult execute() {
         }
     }
 
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return true;
+    }
+
 }
diff --git a/src/seedu/addressbook/commands/ExitCommand.java b/src/seedu/addressbook/commands/ExitCommand.java
index 2f280395c..06a7a0179 100644
--- a/src/seedu/addressbook/commands/ExitCommand.java
+++ b/src/seedu/addressbook/commands/ExitCommand.java
@@ -19,4 +19,10 @@ public CommandResult execute() {
     public static boolean isExit(Command command) {
         return command instanceof ExitCommand; // instanceof returns false if it is null
     }
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
 }
diff --git a/src/seedu/addressbook/commands/FindCommand.java b/src/seedu/addressbook/commands/FindCommand.java
index 8937e08da..4a58ce0cc 100644
--- a/src/seedu/addressbook/commands/FindCommand.java
+++ b/src/seedu/addressbook/commands/FindCommand.java
@@ -53,4 +53,10 @@ private List<ReadOnlyPerson> getPersonsWithNameContainingAnyKeyword(Set<String>
         return matchedPersons;
     }
 
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
+
 }
diff --git a/src/seedu/addressbook/commands/HelpCommand.java b/src/seedu/addressbook/commands/HelpCommand.java
index 8a36e8337..1bb956f9a 100644
--- a/src/seedu/addressbook/commands/HelpCommand.java
+++ b/src/seedu/addressbook/commands/HelpCommand.java
@@ -27,4 +27,10 @@ public CommandResult execute() {
                 + "\n" + ExitCommand.MESSAGE_USAGE
         );
     }
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
 }
diff --git a/src/seedu/addressbook/commands/IncorrectCommand.java b/src/seedu/addressbook/commands/IncorrectCommand.java
index 81abba7a1..546ead34a 100644
--- a/src/seedu/addressbook/commands/IncorrectCommand.java
+++ b/src/seedu/addressbook/commands/IncorrectCommand.java
@@ -17,4 +17,10 @@ public CommandResult execute() {
         return new CommandResult(feedbackToUser);
     }
 
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
+
 }
diff --git a/src/seedu/addressbook/commands/ListCommand.java b/src/seedu/addressbook/commands/ListCommand.java
index d76d48297..0e7b8593f 100644
--- a/src/seedu/addressbook/commands/ListCommand.java
+++ b/src/seedu/addressbook/commands/ListCommand.java
@@ -22,4 +22,11 @@ public CommandResult execute() {
         List<ReadOnlyPerson> allPersons = addressBook.getAllPersons().immutableListView();
         return new CommandResult(getMessageForPersonListShownSummary(allPersons), allPersons);
     }
+
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
 }
diff --git a/src/seedu/addressbook/commands/ViewAllCommand.java b/src/seedu/addressbook/commands/ViewAllCommand.java
index 0067304bb..10c81463a 100644
--- a/src/seedu/addressbook/commands/ViewAllCommand.java
+++ b/src/seedu/addressbook/commands/ViewAllCommand.java
@@ -37,4 +37,11 @@ public CommandResult execute() {
             return new CommandResult(Messages.MESSAGE_INVALID_PERSON_DISPLAYED_INDEX);
         }
     }
+
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
 }
diff --git a/src/seedu/addressbook/commands/ViewCommand.java b/src/seedu/addressbook/commands/ViewCommand.java
index 69335c849..cb67b9402 100644
--- a/src/seedu/addressbook/commands/ViewCommand.java
+++ b/src/seedu/addressbook/commands/ViewCommand.java
@@ -38,4 +38,11 @@ public CommandResult execute() {
         }
     }
 
+
+    @Override
+    public boolean isMutating() {
+        // TODO Auto-generated method stub
+        return false;
+    }
+
 }
diff --git a/src/seedu/addressbook/data/person/Printable.java b/src/seedu/addressbook/data/person/Printable.java
new file mode 100644
index 000000000..43e93d373
--- /dev/null
+++ b/src/seedu/addressbook/data/person/Printable.java
@@ -0,0 +1,5 @@
+package seedu.addressbook.data.person;
+
+public interface Printable {
+
+}
diff --git a/src/seedu/addressbook/ui/TextUi.java b/src/seedu/addressbook/ui/TextUi.java
index 39a2c6615..8442aa2fe 100644
--- a/src/seedu/addressbook/ui/TextUi.java
+++ b/src/seedu/addressbook/ui/TextUi.java
@@ -126,7 +126,7 @@ public void showResultToUser(CommandResult result) {
         if(resultPersons.isPresent()) {
             showPersonListView(resultPersons.get());
         }
-        showToUser(result.feedbackToUser, DIVIDER);
+        showToUser(result.getFeedbackToUser(), DIVIDER);
     }
 
     /**