In this paper, we explore the potential important role that unannounced (or "pop") quizzes can play in CS-1. "Pop" quizzes generate continual feedback to both the student and the instructor of the course. They also encourage students to avoid missing class unless necessary. We present the results of a three year study on the effectiveness of "pop" quizzes in CS-1. Our results demonstrate that students who experience "pop" quizzes in CS-1 score higher on exams than do their counterparts who did not experience "pop" quizzes. This appears especially true for upperclassmen, particularly for juniors. The use of "pop" quizzes in CS-1 also improves performance on programming assignments for juniors. CS/IS majors and Math majors both receive a greater benefit from "pop" quizzes than do other non-majors.