Jairo Guerrero was the first full-time professor in the Systems Department; in fact, he was its founder. He is a Systems Engineer from the Piloto University in Bogota (Colombia). He has a Master's Degree in Models on Problem-based Teaching (Colombia). Jairo Guerrero has served as Chair of the Systems Department, Dean of the Faculty of Engineering and the Director of the Planning Office in the University of Nariño. AcknowledgmentThe authors want to thank the Systems Department at the University of Nariño for their support in the creation of this series of textbooks. This series is dedicated to the students of the Systems Department, to give them reading material related to computer science in a second language. This book covers the Introduction to Computer Science, Computer Communications, Networking and Web Applications. PrefaceThis series of textbooks was created for the students of the Systems Engineering Program at the University of Nariño. They have been intentionally written in English to promote reading in a foreign language. The textbooks are a collection of reflections and workshops on specific situations in the field of computer science, based on the authors' experiences.The main purpose of these textbooks is essentially academic. The way in which the reflections and workshops were constructed follows a didactic structure, to facilitate teaching and learning, making use of English as a second language.The Authors. CONTENTS