This textbook has been primarily designed for B.Tech. students of Computer Science and Engineering (CSE) and Information Technology (IT). The entire text adheres to the latest syllabus of engineering prescribed by all major technical universities of India. Organized in twenty chapters, this book is aimed to give a solid introduction to distributed systems. The book works at four levels: as a textbook for readers; as a book for working IT professionals; as a reference book for the readers who look for an overview of the working of some particular type of systems, like COBRA, JINI, COM, etc.; and as an original scientific contribution which has tried to draw out the common principles that underline distributed systems.