Well suited to medium-scale general purpose computing, the Unix time- sharing operating system is deservedly popular with academic institutions, research laboratories, and commercial establishments alike. Its user com- munity, until recently a brotherhood of experienced computer profes- sionals, it now attracting many people concerned with computer appli- cations rather than the computer systems themselves. This book is intended for that new audience, people who have never encountered the Unix system before but who do have some acquaintance with computing. While helping beginning users get started is the primary aim of this book, it is also intended to serve as a handy reference subsequently. However, it is not designed to replace the definitive Unix system docu- mentation. Unix operating systems now installed in computing centers, offices, and personal computers come in three related but distinct breeds: Seventh Edition Unix, Berkeley 4.2 BSD, and System V. These differ from each other in details, even though their family resemblance is strong. This book emphasizes System V, while paying heed to its two popular cousins. It also includes a few facilities in wide use, but not included in the normal system releases. Individual details, of course, must be found in the manuals supplied with each system.