Compass and Ruler (C.a.R.) is a mighty tool for teaching and experiencing geometry. It has been programmed by René Grothmann, professor of math at the University of Eichstätt, using Java. The program is free and open source.

This is the homepage of C.a.R. The user interface and the main help pages of the program has been translated in many languages. The program will switch to your local language by default. The current full documentation is in English. The German documentation is outdated.

The program is hosted on SourceForge and also on the private server of René Grothmann.