The changes file is one of the four files normally used when working with Squeak. In the .changes file, all source code changes since the last major version (such as 3.0) are logged.
The command (use it after doing a backup of your image and changes file)
Smalltalk condenseChanges
produces a version of the changes file which only keeps the latest changes.
If your image or machine crashes and you haven't saved your image after making some code changes, you should be able to recover the changes from your .changes file. See What to do if Squeak crashes or freezes.
