added constants.php file and implemented constants for file system modes
diff --git a/user_guide/installation/upgrade_162.html b/user_guide/installation/upgrade_162.html
index 7fd01ea..66c498b 100644
--- a/user_guide/installation/upgrade_162.html
+++ b/user_guide/installation/upgrade_162.html
@@ -42,7 +42,7 @@
 <td id="breadcrumb">

 <a href="http://codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;

 <a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;

-Upgrading from 1.6.0 to 1.6.1

+Upgrading from 1.6.1 to 1.6.2

 </td>

 <td id="searchbox"><form method="get" action="http://www.google.com/search"><input type="hidden" name="as_sitesearch" id="as_sitesearch" value="codeigniter.com/user_guide/" />Search User Guide&nbsp; <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" />&nbsp;<input type="submit" class="submit" name="sa" value="Go" /></form></td>

 </tr>

@@ -80,8 +80,10 @@
 <h2>Step 2: Encryption Key</h2>

 <p>If you are using sessions, open up system/application/config.php and verify you've set an encryption key.</p>

 

+<h2>Step 3: Constants File</h2>

+<p>Copy /system/application/config/constants.php to your installation, and modify if necessary.</p>

 

-<h2>Step 3: Update your user guide</h2>

+<h2>Step 4: Update your user guide</h2>

 <p>Please also replace your local copy of the user guide with the new version.</p>

 

 </div>