Henry M. Walker has been an active member within the computing-education community for over two decades. Major activities include curricular development, innovative pedagogy, textbook writing, teaching, and service. Since 1974, he has been on the faculty at Grinnell College, currently as the Samuel R. and Marie-Louise Rosenthal Professor of Natural Science and Mathematics, and Professor of Computer Science. During some leaves and summers, he has taught 8 semesters at the University of Texas at Austin. Internationally, he has been a guest faculty member at Nanjing University in China and Unitec in New Zealand.Before this book, he wrote 8 undergraduate textbooks, published by Jones and Bartlett, Health Publishers, Little Brown, Scott Foresmann, and Winthrop Publishers (affiliated with Prentice Hall). He also has written several dozen articles on computing education, serves as co-editor for the SIGCSE Bulletin newsletter, writes columns on Classroom Vignettes and Curricular Syncopations for ACM Inroads, and serves as an Associate Editor for ACM Inroads.Over the years, Henry Walker has actively participated in the development of the Model Curricula for a Liberal Arts Degree in Computer Science, prepared by the Liberal Arts Computer Science Consortium, and he chaired Pedagogy Focus Group 2 on Supporting Courses for Computing Curricula 2001.