CATO is the self-explanatory user interface for several CAS on Windows, Linux/Unix and Mac/Ox. The principles of CATO are for example: packages realized as selection menus for the commands and extra windows for the input of multi-parameter commands.

The author has developed an application, CATO-Android, with the principles of CATO for smartphones with the operating system android. It is a user interface for guided input for CAS, at the moment only for Symja.

In the article below, the author describes this app and how he realized the principles of guided input.