In this fifth edition, some extra details of last edition have been deleted . At the same time, few more figures are added in different chapters. Further, a few figures and tables have been improved. In this fifth edition, important points are made into bold letters, so that students can grasp the subject easily. A question bank, given in the end of the book, contains essay questions and short note questions, as well as a few multiple choice questions (MCQs). These questions will be ideal for students for last-minute preparation for examinations. This book now gives the ?must know points?.