Written in ADA language, SAIDA, a Help System for Data Implementation, is an experimental teaching and learning environment which uses artificial intelligence techniques to teach a computer science course on abstract data representations. The application domain is teaching advanced programming concepts which have not received much attention from developers of intelligent tutoring systems, such as data abstraction and efficient implementation choices. The first part of the paper explains why a knowledge base approach is particularly suitable for this domain and briefly describes the architecture of the system. Part two presents a typology of the system's users and outlines the various SAIDA functions provided for each kind of user. The third part describes the importance of a meaningful structure of the knowledge domain and discusses several issues which emerge from the construction of knowledge bases for educational purposes. (5 references) (GL)