Learning the Unix Operating System, 5th Edition

Preface

The Unix Family of Operating Systems

An operating system (or “OS”) is a set of programs that controls a computer. It controls both hardware (things you can touch, like keyboards, screens, and disk drives) and software (application programs that you run, like a word processor).

Some computers have a single-user OS, which means that only one person can use the computer at a time. Many older OSes (such as MS-DOS) can also do only one job at a time. But almost any computer can do a lot more if it has a multiuser, multitasking operating system such as Unix. These powerful OSes let many people use the computer at the same time and let each user run several jobs at once.

Unix was invented more than 30 years ago for scientific and professional users who wanted a very powerful and flexible OS. It’s been significantly developed since then. Because Unix was designed for experts, it can be a bit overwhelming at first. But after you get the basics (from this book!) you’ll start to appreciate some of the reasons to use Unix:

• It comes with a huge number of powerful application programs. You can get many others for free on the Internet. (The GNU utilities, available from the Free Software Foundation, are very popular.) You can thus do much more at a much lower cost.

• Not only are the applications often free, but some Unix versions are also free. Linux is a good example. Like the free applications, most free Unix versions are of excellent quality. They’re maintained by volunteer programmers ...