An Overview Of The Unix Operating System Computer Science Essay

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It is important because counting all of the various flavours of UNIX (freeBSD, openBSD, Solaris, HP-UX,etc. also sort of Mac OS-X) and all of the Linux Flavours (which are sort of descendants of UNIX systems) would make up a large portion of all of the computers in operation.

Unix is important in and of itself because it was designed to handle multiple stations connecting to a central hub which, in turn, may itself be connected to other hubs. This defines a network with a star topology which, amazingly enough, is the same as the basic structure of the entire internet.

In a nut shell UNIX is an operating system which at one point in time, was the most prevalent operating system in use. It is still widely used in scientific and professional circles.

Unix is one of the oldest but still most popular Operating Systems. It was invented in 1969 at AT&T Bell Labs by Ken Thompson and Dennis Ritchie. All the contemporary operating systems of Solaris, HP-UX, Linux, AIX are variants of Unix.

Unix is a family of multi-user operating systems. It was originally developed by AT&T in the 1970s. Unix has a very strong security and model and relatively simple design, making it popular and fairly easy to implement. Many operating systems are either based on or modelled after the first Unix systems, such as Linux, Solaris, or Mac OS X.

The new millennium has seen many changes in many areas of computing, from new forms of storage

with massive amounts of storage space, to systems that are far more powerful than the first computer users could have ever imagined. Designed and initially created more than 30 years ago, the Unix operating system has been part of the evolution of computers, so it's no accident that Unix is still one of the most popular operating systems for mission-critical tasks.

Unix is the basis for some of the most-used operating systems today, from Apple's Mac OS X to Linux to the more commonly known Unix versions, such as Sun's Solaris Unix and IBM's AIX. Today many of the versions of UNIX are available free to users and corporations, allowing for a larger use base than many had imagined when Unix was first being developed. Unix is now seen as a user-friendly, very secure, and robust operating system rather than the cold, command line-only operating system once thought to be useful only to computer experts. UNIX, like other operating systems, is a layer between the hardware and the applications that run on the computer. It has functions that manage the hardware and functions that manage executing applications. So what's the difference between UNIX and any other operating system? Basically two things: internal implementation and the interface that is seen and used by users. For the most part this book ignores the internal implementation.

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 flavours 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

UNIX for Mainframes and Workstations

Many mainframe and workstation vendors make a version of UNIX for their machines. The best way to get information on these is directly from the manufacturer.

UNIX for Intel Platforms

Thanks to the great popularity of personal computers, there are a great number of UNIX versions available for Intel platforms. Choosing from the versions and trying to find software for the version you have can be a tricky business because the UNIX industry has not settled on a complete binary standard for the Intel platform.

There are two basic categories of UNIX systems on Intel hardware, the SVR4-based systems and the older, more established SVR3.2 systems.

SVR4 vendors include NCR, IBM, Sequent, SunSoft (which sells Solaris for Intel), and Novell (which sells UnixWare). The Santa Cruz Operation (SCO) is the main vendor in the SVR3.2 camp. Vendors in the first camp are working toward cleaning up the standards to gain full "shrink-wrap portability" between their versions of UNIX. The goal is that this will make UNIX-on-Intel applications available, shrink-wrapped for any version of UNIX, just as you can now buy applications for MS-DOS or Microsoft Windows. SCO UNIX currently has a much larger base of available applications and is working to achieve binary compatibility with UnixWare.


- 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.

The Kernel and the Shell

As the shell of a nut provides a protective covering for the kernel inside, a UNIX shell provides a protective outer covering. When you turn on, or "boot up," a UNIX-based computer, the program Unix is loaded into the computer's main memory, where it remains until you shut down the computer. This program, called the kernel, performs many low-level and system-level functions.

The kernel is responsible for interpreting and sending basic instructions to the computer's processor. The kernel is also responsible for running and scheduling processes and for carrying out all input and output. The kernel is the heart of a UNIX system. There is one and only one kernel.

The Functions of a Shell

It doesn't matter which of the standard shells you choose, for all three have the same purpose: to provide a user interface to UNIX. To provide this interface, all three offer the same basic functions:

l Command line interpretation

l Program initiation

l Input-output redirection

l Pipeline connection

l Substitution of filenames

l Maintenance of variables

l Environment control

l Shell programming

Unix's role in the future

Almost half (47%) see Unix in 5 years as "an essential operating system with continued widespread deployment." One-third of the survey respondents selected the prediction that while not essential in 5 years Unix will still be important in some vertical market sectors. Just 11% selected predictions of migration and 5% envision it fading away.

When asked to select a statement describing their Unix strategy, more than half underlined the importance of Unix by selecting "Unix is an essential platform for us and will remain so indefinitely" (42%) or "We are increasing our use of Unix" (15%). Another 18% described Unix's role as shrinking, but not disappearing. 17% pointed to plans to migrate away from Unix.

Of those who said they were planning on migrating away from Unix, cost was the number one reason, followed by server consolidation, skills shortage and applications.