How to deploy/retrieve an Apex Class using package.xml file in salesforce

Assume AccountUpdater is an apex class in salesforce.
Sample Xml file :
<?xml version="1.0" encoding="UTF-8"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
 <types>
        <members>AccountUpdater</members>
  <name>ApexClass</name>
 </types>
    <version>29.0</version>
</Package>