Update is CUMULATIVE (this mean that it includes all correction from previous updates).

1. Check your version
    Make sure that you run COMSOL version 4.2.0.150 or later. On the Help menu, click About COMSOL Multiphysics to check your version.
   If you have an earlier build number, contact your COMSOL sales representative to get the official release of COMSOL 4.2 before you proceed.

2. Install
    2.1 Install under Linux:
         Before you proceed with the installation, make sure to exit any running COMSOL process.

    Linux:
     1 Copy the downloaded .zip-file to the COMSOL 4.2 installation directory:
          cp Comsol42_Update3_Linux.zip [installdir]/comsol42
           where [installdir] is the root of the installation, for example /usr/local.

     2 Unzip it by the commands:
          cd [installdir]/comsol42
          unzip -o Comsol42_Update3_Linux.zip

     3 If you have not disabled SELinux, run the following command:
          chcon -t textrel_shlib_t [installdir]/comsol42/lib/[platform]/lib*
           where platform is glnx86 or glnxa64.


    2.2 Install under Macintosh:
         Double-click the Comsol42_Update3_MacOS.dmg file to mount the disk image.
         In the Finder, open the mounted disk and double-click the COMSOL installer icon.
         Select your COMSOL installation folder, usually called COMSOL42.

         Do the same thing with other two files (Comsol42_Update3_MacOS_Matlab.dmg and 
         Comsol42_Update3_MacOS_StructMech.dmg) to update "LiveLink with Matlab" and 
         "Structural Mechanics Module"

         NOTE: Files Comsol42_Update3_MacOS_Matlab.dmg and Comsol42_Update3_MacOS_Matlab.dmg
         are binary identical with Comsol42_Update2_MacOS_Matlab.dmg and Comsol42_Update2_MacOS_Matlab.dmg
         It mean that "LiveLink with Matlab" and "Structural Mechanics Module" has nothing new
         compared to Update2. These file are part of Update3 because one could whish to update
         Comsol from version prior to Comsol 4.2 Update2 and Update3 will do the job well!