Unix & Linux - Two Powerful Systems That Are Often Misunderstood

UNIX AND LINUX

Two Powerful Systems That Are Often Misunderstood

By Paul

Operating Systems Concepts

October 9, 1999

Unix and Linux

There have been many-recorded eras throughout man's history. There was the Ice Age (BURR), the Stone Age, the Bronze Age, and the Industrial Age (revolution) just to name a few. Each of these eras marks pivotal advances in humankind. Here are some examples of our advancements, during the Ice Age, one of nature's first demonstrations of her power in population control, man presents his first fashion show focusing on the elegant features of Fur clothing and accessories. The Industrial Revolution mans first experience with assembly line manufacturing. It was dark and dingy when you went to work, it was dark and dingy at work, and it was dark and dingy after work. Hey is that the Sun! Thank goodness for the "EPA." Lucky for all, that's behind us now. Yes, man has moved on once again to a new era, the Information Age. Now instead of men (and women) working at the brewery to manually check and ensure that all the bottle caps have been placed correctly on our beer bottles, there are robot arms checking them and these advanced machines are run by computers. This example may trivialize mans advancements but it also simplifies the big picture. We can all classify ourselves as players in, victims of, or even products of, the Information Age. Success in the Information Age is based on a corporation's, a small business's, or a students ability to gather information (useful information) quickly and accurately then being able to store that information efficiently to draw upon when necessary. The primary tool for most of this wonderful work is the computer and chances are you can see one in almost every office from here to Harrisburg but the part of the computer that is seen on all the desks in all these offices is merely the hardware. There is much more to a computer than just its physical components. There is a very important component that most end users take for granted until something goes wrong and their computer screen image has not changed for twenty minutes. This other part of the computer, the mysterious and not as obvious component of the computer, is the called software.

Software can be placed in two categories either Application Software or Operating Systems Software. Application Software are programs that are developed to perform specific functions for the end user. The Operating System is a group of programs that control or instruct the hardware on how and when to perform routine operations, example: Printing. There are many operating systems in use today, a few examples are Windows 95/98, Windows NT, MS-DOS, UNIX and one you may not have heard of, LINUX. The focuses of this report are the operating systems UNIX and LINUX, two very interesting and powerful systems. The first is often labeled as too confusing and unfriendly, the later is relatively unknown to the novice user, but surprisingly they are very similar in design. A short history of the two operating systems may explain why they are so similar.

UNIX is a creation out of Bell Labs in the 1960's, in a project headed by Stephen Bourne. The idea was to create an operating system whose kernel (core part) was as tiny as possible. The main driving force, the small UNIX kernel, was that the developers were doing their work on what were considered in that day to be tiny computers. The severe limitation on RAM resulted in a small kernel with all the utilities implemented as separate, stand-alone programs. Each was itself tiny, and designed to accept input from the preceding program as well as provide output to succeeding programs. This process of using output from one program as input into another is referred to as piping and is central to UNIX operating systems today (UNIX & LINUX Answers! Certified Tech Support © 1998).

LINUX is a creation of Linus Torvalds, in 1991 when he was a computer-science student in Finland. Since then, hundreds of independent programmers across the Internet have contributed to the development of the UNIX-like software. This is possible because the LINUX source code, the computer instructions in the original form, is freely available to anyone who cares to download or modify it. LINUX is quickly growing in popularity among serious users because of its strong ties to UNIX and its powerful capabilities, in many publications referred to as "Little UNIX." LINUX is also growing in the corporate world with one of UNIX's largest venders "SCO" providing support assistance on their web site. Some other well-known LINUX distributors are Red Hat and Caldera (Communications News: Aug 1999, vol. 36). It is easy to see from the brief histories given that these two operating systems are very similar at their core (kernel), to see if the similarities continue as you work away from the kernel, a look at the multitasking, memory management, multiprocessing, and multi-user capabilities is needed.

Due to the fact that computer technology has not quite advanced enough to create machines with unlimited amounts of memory or number of processors, the kernel maps the demands of the application or user program to the resources available. Several programs may be executed at one time by scheduling each process to run for a fraction of a second; a round robin arrangement is used so that each process appears to be running continuously and the users see no indication that their program is spending most of its time in a state of suspension. The kernel keeps track of how much time each process spends running, so that no processes are ignored; however, the more processes that are running concurrently, the less time each process spends being attended to by the CPU, and the systems appear to run more slowly (www.sco.com: Professional Services).

Memory management is also the responsibility of the kernel. A computer capable of running a multi-tasking system may have to deal with widely varying demands for memory. At some point in time there may be no users logged on and the only tasks running are the kernel and a backup process. At other times there may be ten or more users logged on all trying to carryout complex operations that demand extensive amounts of memory. In this case both UNIX and LINUX systems provide what is called