.:UNIX OPERATING SYSTEM

WHAT IS UNIX?

Unix is a powerful, multi-user environment that has been implemented on a variety of platforms. Once the domain of servers and advanced users, it has become accessible to novices as well through the popularity of Linux and Mac OS X. With the notable exception of Microsoft Windows, all current major operating systems have some kind of Unix at their cores.

Unix was developed at Bell Labs in 1969, but in the past three decades many others have contributed to its evolution. In reality, Unix is not so much a single operating system as it is a standard upon which organizations and companies base their own systems.

Examples of Unix implementations include Mac OS X/Darwin (Apple), GNU/Linux, AIX (IBM), Solaris (Sun), IRIX (SGI), and FreeBSD. They have different graphical interfaces, but from the Unix shell, a command line feature common to all versions, they are very similar.

A system is termed UNIX only if it complies fully with (and is certified by) the Single Unix Specification (SUS) standards. Similar systems that do not comply fully or are not certified are termed Unix-like operating systems. Examples of popular Unix-like systems include Linux and Xenix.

Unix and Windows:

(Two Major Classes of Operating Systems.)

And they have a competitive history and future. Unix has been in use for more than three decades. Originally it rose from the ashes of a failed attempt in the early 1960s to develop a reliable timesharing operating system. A few survivors from Bell Labs did not give up and developed a system that provided a work environment described as "of unusual simplicity, power, and elegance".

Since the 1980's Unix's main competitor Windows has gained popularity due to the increasing power of micro-computers with Intel-compatible processors. Windows, at the time, was the only major OS designed for this type of processors. In recent years, however, a new version of Unix called Linux, also specifically developed for micro-computers, has emerged. It can be obtained for free and is therefore a lucrative choice for individuals and businesses.

On the server front, Unix has been closing in on Microsoft's market share. In 1999, Linux scooted past Novell's Netware to become the No. 2 server operating system behind Windows NT. In 2001 the market share for the Linux operating system was 25 percent; other Unix flavors 12 percent. On the client front, Microsoft is currently dominating the operating system market with over 90% market share.

Because of Microsoft's aggressive marketing practices, millions of users who have no idea what an operating system is have been using Windows operating systems given to them when they purchased their PCs. Many others are not aware that there are operating systems other than Windows. But you are here reading an article about operating systems, which probably means that you are trying to make conscious OS decisions for home use or for your organizations. In that case, you should at least give Linux/Unix your consideration, especially if the following is relevant in your environment.

Advantages of Unix

• Unix is more flexible and can be installed on many different types of machines, including main-frame computers, supercomputers and micro-computers.


• Unix is more stable and does not go down as often as Windows does, therefore requires less administration and maintenance.


• Unix has greater built-in security and permissions features than Windows.


• Unix possesses much greater processing power than Windows.


• Unix is the leader in serving the Web. About 90% of the Internet relies on Unix operating systems running Apache, the world's most widely used Web server.


• Software upgrades from Microsoft often require the user to purchase new or more hardware or prerequisite software. That is not the case with Unix.


• The mostly free or inexpensive open-source operating systems, such as Linux and BSD, with their flexibility and control, are very attractive to (aspiring) computer wizards.
  Many of the smartest programmers are developing state-of-the-art software free of charge for the fast growing "open-source movement".


• Unix also inspires novel approaches to software design, such as solving problems by interconnecting simpler tools instead of creating large monolithic application programs.

Variants of Unix

AIX / AIXL
BSD
DUnix
DYNIX/ptx
HP-UX
IRIX
MINIX
OSF/1
QNX
SCO
Sun Solaris
System V
Tru64 Unix
Ultrix
Unisys
UnixWare
Xenix

LINUX

Introduction

Linux, originally created by Linus Torvalds, is an operating system that is freely distributed under the terms of the GNU Public License. It behaves like Unix, but does not come from the same source code base. Linux is available in both source code and binary form.

Linux offers standard Unix features, such as multiuser support, multitasking, networking, and POSIX compliance. It supports all the standard Unix utilities and can compile most major Unix packages with little effort. DOS emulation is also available, and an X Window System-based Microsoft Windows compatibility layer, called Wine, is in development.

The complete Linux operating system consists of the Linux core, or kernel, combined with the utilities and applications required for a fully functional operating system. There are several such combinations, called distributions, put out by various companies, and there is no such thing as an official version.

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