Tutorials Center

1.4 A Brief Session Seeing is believing as they say, so without further ado, let’s get down to business and see what a UNIX session is really like. If you are migrating from the DOS/Windows environment, you have a bit of mental preparation to do before you start. UNIX isn’t very friendly, and the messages that it throws up on the screen can sometimes be confusing. Often, there are no message at all, and you’ll then have to figure out yourself whether the command worked properly. Absorb as much as you can from this session, think for a while, and then move on to the other chapters.

1.3.1 The Keyboard Before you start working, you need to know right now the functions of a number of keys on the keyboard. Many of these keys are either not used by DOS/Windows, or have different functions there. The portion of the keyboard at the left having the QWERTY layout resembles your typewriter. You need to be familiar with this section of the keyboard initially, in addition to some other keys in its immediate vicinity. If you know typing, you are on familiar terrain, and keyboard phobia should not get your way. Apart from the alphanumeric keys, you’ll observe a number of symbols as shown below: ` ~ ! @ # $ % ^ & * ( ) - _ = + \ | [ ] { } ; : ‘ “ , . < > / ? Each alphabet, number or symbol is known as a Character, which represents the smallest piece of information that you can deal with. All of these characters have unique values assigned to them, called the ASCII value (ASCII- American Standard Code for Information Interchange). For instance, the le...

1.3 Knowing Your Machine Unlike DOS and Windows, UNIX can be used by several users concurrently. In other words, a single copy of the operating system installed on disk can serve the needs of hundreds of users. If you have access to such a  multi-user  system, then in all probability you’ll be sitting with just a terminal or monitor, and a keyboard. Like you, there will be others working on similar terminals. The rest of the equipment will probably be located in a separate room with restricted access. In this arrangement, you are expected to hook on to your account, do your work, disconnect and leave quietly. Things are quite different, however, when you are the sole user of the system. This could happen of you work on a desktop machine that has its own CPU (the Central Processor Unit), RAM (Random Access Memory—the memory), hard disk, floppy and CD-ROM drives, printer and the controllers of these devices. If you own the machine, you are directly respon...

1.2 The UNIX Operating System Like DOS and Windows, there’s another operating system called UNIX. It arrived earlier than the other two, and stayed back late enough to give us the Internet. UNIX is a giant operating system, and is way ahead of them in sheer power. It has practically everything an operating system should have, and several features which other operating systems never had. Its richness and elegance go beyond the commands and tools that constitute it, while simplicity permeates the entire system. It runs on practically every hardware and provided inspiration to the Open Source movement. However, UNIX also makes many demands of the user. It requires a different type of commitment to understand the subject, even when the user is an experienced computer professional. It introduces certain concepts not known to the computing community before, and uses numerous symbols whose meanings are anything but obvious. It achieves unusual tasks with a few keystrokes, but i...

1.1 The Operating System We use computers freely, but most of us never bother to know what’s inside the box. Why should we? After all, we also use TV and never care to find out how this idiot box manages to convert invisible radio waves to real-life  colorful  pictures. Yes, you can certainly use spreadsheets and word processors without knowing how these programs access the machine’s resources. As long as you continue to get all those reports and charts, do you really need to know anything else? Then the inevitable happens. The great crash occurs, the machine refuses to boot. The expert tells you that the operating system has to be reloaded. You are taken in by surprise. You’ve heard of software, and you have used lots of them. But what is this thing called the operating system? Is it just another piece of software? Relax, it is. But it’s not just any ordinary software that helps you write letters, but a special one – one that gives life to a machine. Every...

          UNIX and the C language have changed the way people used and learned to program with computers. Even though technology changes fast, certain approaches to technology often remain unchanged. UNIX is one of them; it has survived the test of time. Enterprise managers today no longer need to justify the use of UNIX. Thanks partly to Linux, things should remain this way in the foreseeable future too.             Even though this book deals with an operating system in particular, it will help you understand operating systems in general. This fourth edition was written with this objective in mind. In fact, theoretical courses on operating systems often use the UNIX system to illustrate key features. Although we haven’t seen another notable system since the advent of UNIX, it shouldn’t surprise us if future operating systems adopt many of the key features of UNIX.             Many peo...

Getting Started                 Chapter – 1 This Chapter begins the tour of the  UNIX  universe.  To understand unix , we’ll first have to know what an operating system is, why a computer needs one and how unix is vastly different from other operating system that came before – and after.  Through a hands-on session, we’ll learn to play with UNIX system and acquire familiarity with some of its commands that are used every day for interacting with the system. The experience of the introductory session will help us understand the concepts presented in the next chapter. UNIX had had a rather turbulent background. Knowing this background will help us understand the objectives that guided its development. Even though UNIX owes its origin to AT & T, contributions made by the academic community and industry have also led to the enrichment and fragmentation of UNIX. The emergence of a windowi...