A user model can be roughly described as the information that a system keeps about an individual user. This paper address the problem of building a user model for an intelligent tutoring system. In this framework the main purpose of a learner model is to provide the instructional planning component with the information it needs to select a suitable instructional action. Our system, CAPRA, teaches novice students about program specification. The approach to building the student model relies on gathering a great deal of information about the student behavior in a non-intrusive way. CAPRA provides a problem solving environment with intermediate languages, a Spanish natural language interface for communication activities, and a knowledge-based debugger.