JCAT: Collaborative Active Textbooks Using Java. This paper describes JCAT, a Java-based system for building Web-based collaborative active textbooks on algorithms. JCAT augments the expressive power of Web pages for publishing passive multimedia information with a full-fledged interactive algorithm animation system. The system is built in such a way that views of a running program may reside on different machines, thereby making JCAT particularly well-suited for electronic classrooms. In such a setting, an instructor controls the animation, while students view the animation by pointing their Web browsers at the appropriate page.