"The book is written for the 1st year T.D.C. students of computer application for all Inidan Universities. However another students find it useful for their competitive examinations. In the present book not only a large number of solved problems of different types asked in the examination of various universities has been given but also the self explanatory diagrams have been included to understand the applications of various principles discussed in the chapter. It is hoped that above features of the book make it unique from other. We express our deepest sense of gratitude to all the professors and lecturers, who helped us in writing this book. Several books and journals on the subjects have been referred in preparation of this book. Gratitude is also expressed to them. It is hoped the students will find the book very helpful. Although every care has been taken to avoid mistakes and misprints, yet it is very difficult to claim perfection. Any suggestion for improvement from the readers will be gratefully acknowledged. "