The UNIX system is so successful. Why? First, because UNIX is portable, i.e., runs on a range of computers and adapts to particular requirements. Second, the UNIX programming environment is unusually rich and productive. The UNIX system has become very popular, and there are number of versions in wide use. Regardless of the version you run on your system, the difference in coding you find will be minor. The book’s small size is meant to keep your investment in time down to a minimum but with the greatest possible amount of knowledge. This book is organized as follows: Part I is an introduction to the most basic use of the system. It covers logging in, the file system, commonly used commands, and logging out. Part II contains 100 programs (including shell script and programs in C). The best way to learn something is by doing it. Kindly practice the programs and verify or contradict what we say. All the examples in this text are actual, runnable code tested on UNIX system. As a reader of this book, you are the most important critic and commentator. You can email or write to us directly to let us know what you did or didn’t like about this book – as well as what we can do to make our book stronger.