The first edition of the book with twenty four reprints spoke volumes of its success and was certainly an index of its popularity among the teaching and student community. However, knowledge never ceases to expand and there is always scope for improvement. The first edition aimed at providing the subject matter in a concise, lucid and simple manner for easy comprehension by all. However, in order to make the book more purposeful and acceptable to a wider section of users, the revised edition includes elegant methods involving vector and complex numbers usually preferred by those who excel in mathematical skills. Such methods frequently lead to computer-aided solutions of the problems. However, those who do not wish to adopt these methods can easily skip them while reading the book.

In the present edition, apart from rewriting some of the previous sections, several new sections have been added in almost all the chapters. Many new worked examples have been incorporated. The computer programs have been rewritten in C, the most widely used language today. Theoretical questions have been added to the exercises. Each chapter now has a summary at the end. Also, an appendix containing objective-type questions has been added. In spite of addition of a large amount of material, care has been taken to let the book remain concise and compact. All the previous figures have been redrawn. Effort has also been made to remove errors that had arisen due to misprinting in the earlier edition.

I acknowledge the efforts of the editorial and production staff of Tata McGraw-Hill Publishing Company Ltd. for bringing out the new edition in an excellent format. I am grateful to all the teachers and students who have provided several valuable suggestions for the improvement of the book.

Further comments and suggestions on the new edition are welcome.

S S RATTAN