This collection of essays results from the second national conference of Computer Assisted Language Learning (CALL) held at the University of Exeter. The theme of the conference - program structure and principles in CALL - is reflected in the contributions. They form a handbook for the CALL enthusiast, a doing book, designed to assist the researchers and to indicate avenues that can be readily explored both in individual research and in the elaboration of other people's programs. As the first four chapters underline, future work in CALL must be based on practical pedagogical principles as there is a tremendous difference between devising programs that should help people learn and the writing of programs that take into account proven learning techniques and skills.