Traditional software development tools such as CVS and Subversion do not inform users about concurrent modifications while they work on shared pro jects in their local workspaces. We propose an awareness mechanism that informs users about location of concurrent changes at the level of class, method and line. Developers are provided with a preview of the concurrent changes made by other contributors on the pro ject. They can continue to change and test their code without the need to integrate concurrent changes. We present the underlying algorithms of our proposed awareness mechanism.