On modern Java versions, you should be able to start the program by double clicking the program archive zirkel/doc/doc_en/zirkel.jar. If this does not work, try one of the following command lines

cd zirkel/doc/doc_en
java -jar zirkel.jar
java -cp zirkel.jar Zirkel

You find the documentation on zirkel/doc/doc_en/index.html.

Command line options for the program are.

    * "-l locale". This allows you to switch the locale. Try for "-l de" to see the German interface on an English system.
    * "-s". You will get simpler but faster graphics under Java 1.2 or better.
    * "-h file". Loads the configuration file from the specified location (default is "zir.cfg" in the home directory of the user).
    * "-r". Program runs in restricted school mode.
    * "file". All other parameters are file names of constructions. 

Java Web Start

A convenient way to start programs from the Net. The program will be updated automatically. So the user has the most recent versions at all times. The documentation should be read over the Net, but can be installed locally (see above for "Other Operating Systems"). You need Java 1.2 or better, and a system, which is supported by Java Web Start. Java Web Start is included in Java 1.4. Under Linux, you should use the Java from IBM.

See this page for details.
Intermediate Release, small Download or Update

This is for expert C.a.R. users needing new features of an intermediate release. To update from a stable version to an intermediate release, download the new program archive, and replace the old file "zirkel.jar" on your computer with the new version. The archive will also work, if you want a small download. On most systems, you can double click on the program archive to start the program.

Note, that it is preferable to update the documentation with each release. The homepage will show the most recent documentation, of course. Otherwise download this file, which contains the documentation and the program archive (see below for "Other Operating Systems")
Source

The program is freeware, and the source is available and free by the GNU General Public License.

To translate the sources, you need to unpack the zirkel.jar archive into the same directory, since the source of HotEqn is not available. Start with "javac Zirkel.java".