This book is a complete description of vi, the popular display oriented interactive text editor on Unix systems. The thorough treatment of the vi editor applicable to both system V and 4.2 BSD Unix systems, helps the user learn and understand its features beginning from the fundamentals. It also helps the user to develop skills of a more sophisticated level and is not only for beginners but also for the more advanced users of Unix systems. The many examples and the quick reference guide are useful features of the book.