COMSOL Multiphysics version 4 is in many aspects an entirely new product. This document outlines the differences between version 3.5a and version 4.1. It also outlines additions that we intend to make in COMSOL Multiphysics version 4.2.
We have strived to achieve backward compatibility with the previous version and to include all functionality that is available there. COMSOL 4.1 is compatible with COMSOL 3.5a, COMSOL 4.0, and COMSOL 4.0a with a few exceptions. Those exceptions are listed in this document.
In the menu to the right you will find release notes for each product.