Structural learning is essential for accurate and reliable knowledge acquisition. This book is doing that for more than two decades now. Currently in its 22nd edition, the book continues to be the one-stop solution for the aspirants preparing for various competitive examinations. This book has been the best-seller for more than 15 years now and is being thoroughly updated and revised to recent developments and trends in related examinations patterns. Special efforts have also been made to provide the widest coverage of facts and events in a concise and easy-to-understand manner.