Practical experiencesare necessaryto balance the theory discussed in textbooks and in class meetings. Effective practicalexperiencesmust have a clear purpose and must motivate students to becomeinvolved as active learners. This paper presents some practical experiences for an introductory operating systems course. The experiences employ short programs with unexpected behaviors and open-endedquestions.Studentsusetheseas starting points to discover more about the concepts involved. The presentedexperiencesprovide effectivereinforcementof the underlying theory. Keywords operatingsystems,practicalexperience,discoverylearning