The document provides an introduction to the Linux operating system, discussing its origins from the collaborative efforts of many programmers to create a free and open source alternative to commercial UNIX systems. It describes how Linus Torvalds created the initial Linux kernel in 1991 and how it has since been refined by numerous contributors. The summary concludes that Linux has grown from humble beginnings to become a widely used and respected operating system available across many computing platforms.

1. LINUX OPERATING SYSTEM

2. Introduction The revolutionary operating system LINUX , owes its existence to the cooperative efforts of a large number of people. The operating system kernel itself forms only a small part of a usable development system. Commercial UNIX systems traditionally come bundled with applications programs which provide system services and tools. For Linux systems, these additional programs have been written by many different programmers and have been freely contributed. The Linux community supports the concept of free software, subject to the GNU (General Public License). Although there may be a cost involved in obtaining the software, it can thereafter be used in any way desired, and is usually distributed in source form. The Free Software Foundation was set up by Richard Stallman , the author of GNU Emacs, one of the best known editors for UNIX and other systems. Stallman is a pioneer of the free software concept and started the GNU project, an attempt to create an operating system and development environment that will be compatible with UNIX. It may turn out to be very different from UNIX at the lowest level, but will support UNIX applications. The name GNU stands for GNU's Not Unix. The GNU Project has already provided the software community with many applications that closely mimic those found on UNIX systems.

3. Origin of Unix UNIX got its start when a group of researchers from AT&T Bell Laboratories , General Electric and the Massachusetts Institute of Technology worked together under the Multiplexed Information Computing System , or MULTICS , project in 1968 . AT&T Bell Laboratories researchers Ken Thompson and Dennis Ritchie developed UNIX with many of the developments of the MULTICS project. UNIX was intended to be an affordable multi-user and multi-tasking OS, and to help meet those goals, UNIX was rewritten in 1973 using the C programming language. This allowed the UNIX OS to become transportable to other hardware platforms without having to be specifically written for that hardware platform. This ease of transport is still evident today because versions of UNIX are available for practically every computing platform, from PC to Supercomputer. As UNIX grew, Bell Labs licensed it to several users, one of which was the Computer Science department of the University of California Berkeley, creators of the Berkeley Software Distribution (BSD). The development of UNIX over the years at Berkeley, with the support of the Defense Advanced Research Projects Agency (DARPA) , included the TCP/IP networking protocol suite that now powers the Internet. However, these various distributions of UNIX caused some compatibility problems. To resolve this issue, the Institute of Electrical and Electronics Engineers (IEEE) developed a new American National Standards Institute (ANSI) standard called the Portable Operating System Interface for Computer Environments (POSIX) . This standard defines how a UNIX-like system needs to operate; this standard also details system calls and interfaces. This ANSI standard resolved most of the compatibility issues and helped UNIX to expand even further. The longer that UNIX was in distribution and with all the advances that were being made, however, one thing became increasingly clear: UNIX was being developed for workstations and minicomputers. This meant that students at major universities were unable to use UNIX applications on their powerful PCs in the late 1980s and early 1990s. And even though Professor Andrew Tannebaum had created Minix , a UNIX-like OS, it didn’t have the functionality desired by some students like Linus Torvalds .

4. Linus and Linux Linus Torvalds started the Linux project while he was a student at the University of Helsinki . He worked to create a UNIX-like operating system equipped with more features than Minix. Torvalds created a Linux kernel that could work with UNIX applications, and in 1991 , he released his first kernel for the Intel x86 platform , which was widely distributed over the Internet. A kernel is the core of any operating system , and the Linux kernel was built to work like UNIX but doesn’t use any of the UNIX code — this is why Linux is not UNIX . The kernel is what allows most software to access the hardware that it is installed on. The key to Linux is its kernel because the kernel allows other programmers to refine it, add to it, and incorporate most of the features and applications of UNIX. Most standard UNIX applications have been ported to Linux, such as windows managers, Internet utilities, program development utilities, and just about every other tool used in computing today. The ability that other programmers have to work on and improve the Linux kernel is a result of the unique way Linus Torvalds distributed the kernel itself.

5. LINUX ??? Linux is a 32-bit operating system (OS) that can be used on every computer hardware platform. Originally designed for the Intel x86 platform , it is now available for Intel, Sparc, Alpha, embedded devices, and many more platforms . Linux is a UNIX-like OS that is very stable, reliable, and flexible . It is used on PCs , professional workstations , servers , routers , and practically every other computing platform. Linux works well in all these environments, and because it is multi-user and multi-tasking , it can perform virtually any job or group of jobs quickly and efficiently. Linux is as powerful as any other operating system, and most importantly, it is free . Linux was created to be a free alternative to UNIX and has become a competitor for all operating systems available today. This fact has enabled Linux to greatly increase its user base, and to be supported and used by the largest corporations and governments in the world. Because of its open nature and technical strengths, Enterprise use of Linux is best illustrated by its large-scale use on the Internet — it powers a majority of Internet applications, including the Apache Web server . Linux has sprung from humble beginnings to become a widely used and respected OS on essentially all computing platforms. Linux is a direct competitor with other high profile operating systems, such as UNIX and Microsoft Windows.

6. SOME BASIC FUNDAsss... GNU - GPL The availability of the Linux kernel is different from the UNIX kernel or even the Windows kernel because it is distributed under the GNU (which stands for GNU's Not UNIX ) - General Public License (GPL) . This license means that the source code is freely distributed and available to the general public, usually via the Internet. In 1983 , Richard Stallman announced the GNU project, an ambitious effort to create a free software "free" in the sense, everyone who received a copy would be free to use, study, modify, and redistribute it. The GNU project's own kernel development project, GNU Hurd, had not produced a working kernel, but in 1992 Linus Torvalds released the Linux kernel as free software under the GNU General Public License. In addition to their use in the GNU/Linux operating system, many GNU packages - such as the GNU Compiler Collection (and the rest of the GNU tool chain), the GNU C library and the GNU core utilities - have gone on to play central roles in other free Unix systems as well. The GNU GPL ensures that no one person or organization can make a change to the kernel without making those changes publicly available. The Free Software Foundation, through fund-raising, supports the GNU project.

7. Open Source The GNU GPL makes Linux Open Source because it is an acceptable license for Open Source Software. Open Source follows a similar path of the GNU GPL, but it also has many differences. Even though the Open Source Initiative strictly adheres to GNU GPL, it is not a specific license; rather, the Open Source Initiative supports the various types of open source licenses that are available. The idea behind the Open Source Initiative (OSI) is to gather corporate support behind open source. Companies that want to participate in Open Source are allowed to write their own license or use the GNU GPL and submit the license to the OSI for certification. This opens the door for all Open Source software and guarantees not only source code access but also follows the Open Source Definition. The Open Source Definition contains following points: . Free Distribution . Source Code . Derived Works . Integrity of The Author’s Source Code . No Discrimination Against Persons or Groups . No Discrimination Against Fields of Endeavor

8. Closed Source In Closed Source software, such as Microsoft products , the creators are the only ones who can access and modify the software source code. Of course, this also means that they are the only ones who are authorized to refine, add to, and fix bugs in the software. This is the most restrictive of the software licensing methods. Selecting Closed Source as the licensing method often draws the wrath of GNU GPL and Open Source supporters. The Open Source and GNU GPL supporters see Closed Source as a restriction that should be lifted to allow anyone to fix, improve, or change the software for the benefit of the software and its community of users. Companies that select Closed Source as the licensing method for the software that they release are often trying to protect “intellectual property,” and therefore see little benefit to opening the software to others. This is a major philosophical difference between Closed Source and Open Source software licenses.

9. Conclusion Thus, it can be said that in computer arena, you have to think beyond the limits. Linux is such an OS that permits you to jump at your horizons. Now, as we know, Linux is the part of Open Source Movement. The Linux operating system is free, but more important thing, Linux is open. That means the source code of OS is available to everyone and everyone contributes in its quality. Thousands of programmers do the improvisation within the code. When any bug or security hole is encountered, the programmers fix it, because it is in every system they have distributed. The improvisation is necessary to every copy and freely available as update on Internet. You just have to connect to the internet to update your system. These updates are available on the net within the few hours since the hole is discovered. We need not have to rely on some monolithic, large, closed source, bottom-line focused company to fix the problem. Also, this fixation gets a huge time to complete and the process is also tedious. So, in every way you get a benefit when you decide to contribute or keep your faith on the Open Source Movement. If we talk about the security measures, there are lots of considerations. Everyone requires security. But the security needs, they vary from the user and the type of his work. I will also like to mention a sentence here- ” The problem with keeping information secret is that when it is needed, the process of getting the information is time consuming” So why not you make the whole system secure then just hiding your information? And this thinking makes the difference of security levels. Hence, if I need the total benefit of my resources I will accept the Open Source guidelines. What you get on your system is up to you.

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