The name “UNIX” may be familiar to some of you. You may even use a UNIX system at work, in which case this chapter may not be very interesting.
For those of you who have never used a UNIX system, reading this chapter is absolutely necessary. Understanding the concepts which will be introduced here will answer a surprisingly large number of questions commonly asked by beginners in the GNU/Linux world. Similarly some of these concepts will likely answer most of the problems you may encounter in the future.