The Coach system, a computer simulation of a human tutor, was constructed with the goal of obtaining a better understanding about how a tutor interprets the student's behavior, diagnoses difficulties and gives advice to a student learning a simple computer programming language. Coach is based on a hierarchy of active schemas representing the tutor's general concepts, more specific information represented in a semantic network, and the coordination of data driven and conceptually guided processing which enable it to interpret behavior, recognize errors, and give advice. This paper describes the Coach system as it gives advice to a student learning FLOW, a simple computer programming language. (Author)