diff --git a/04/src/PersistenceManager.java b/04/src/PersistenceManager.java
new file mode 100644
index 0000000..80a2f37
--- /dev/null
+++ b/04/src/PersistenceManager.java
@@ -0,0 +1,55 @@
+/**
+ * Persistence manager using the Singleton pattern.
+ */
+public class PersistenceManager
+{
+    private static PersistenceManager instance = null;
+    
+    /**
+     * Returns an instance of the persistence manager.
+     * @return instance
+     */
+    public static PersistenceManager getInstance()
+    {
+        if (instance == null) {
+            instance = new PersistenceManager();
+        }
+        
+        return instance;
+    }
+    
+    /**
+     * private constructor
+     */
+    private PersistenceManager()
+    {}
+    
+    /**
+     * Begins the transaction and returns the transaction ID.
+     * @return transaction ID
+     */
+    public int beginTransaction()
+    {
+        return 0;
+    }
+    
+    /**
+     * Commits the transaction specified by given ID.
+     * @param taid transaction ID
+     */
+    public void commit(int taid)
+    {
+    
+    }
+    
+    /**
+     * Writes given data into given page in given transaction.
+     * @param taid transaction ID
+     * @param pageid page ID
+     * @param data data
+     */
+    public void write(int taid, int pageid, String data)
+    {
+    
+    }
+}