C.a.R. is open source by the GPL and free of charge. the GPL allows to change or modify the source, as long as the source remains open. Parts of the source may only be used in other GPL projects, and must be cited. Commercial applications are possible, but the source pages must be cited. You are welcome to distribute C.a.R. on CDs.

The Latex formatting in C.a.R. is based on code from HotEqn by VCLab  Software. This code is under GPL too. The PNG saving code is GPL code by David Eisenberg.


C.a.R. is a Java program and requires a runtime. It is essential to use the most recent Java version for your system. If the program does not start please update your Java version. I recommend to download and install the JDK from the following page.

The program will switch to your local language be default, even if you download the English packages below. For the German documenation you can refer to this web page.

Download and Installation

Get the zip file for all operating systems (, an executable installer for Windows (car.exe), or the jar-file (zirkel.jar). Start the jar-file with the command java -jar zirkel.jar. The zip file contains batch files for this.

Installation for Experts

For experts, it is possible to download the core program archive only.