3. Main achievements, main projects

Essential free software is presented here from the user's point of view. The aim is to provide an overview of what's available, without of course going into the details that are the responsibility of each software's manual. Generally speaking, the technical underpinnings of the software are fairly stable, but user functions are being added to at a rapid pace, and the presentation given here will inevitably become outdated very quickly. Readers should therefore refer to the project websites for an up-to-date overview.