In a knowledge and information based economy, Information Technology and systems take on great importance. For instance Information Technology constitutes more than 70 percent of the invested capital in service industries like finance, insurance and real estate. This means that for many managers (perhaps for most) decisions about Information Technology will be the most common investment decision. Because the productivity of employees will depend on the quality of the systems serving them, management decisions about Information Technology are critically important to the prosperity and survival of the enterprise. In order therefore, to ensure continued use of Information Systems, there is the urgent need to guarantee the required level of understanding and application through a more simple methods of acquisition of the required skills. This book is designed to provide the needed insight and guidance to students and workers from a beginner level and also to serve as a reference manual for the more experienced users.