ITTABLES [A table where all the IT Professionals meet]: Linux

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LINUX

A Brief History of Linux

UNIX is one of the most popular operating systems worldwide because of its large support base and distribution. It was originally developed as a multitasking system for minicomputers and mainframes in the mid-1970's with its high performance and stability to support high cost computer with MIT and GE.

In 1965 Bell Labs was adopting third generation computer equipment and decided to join forces with General Electric and MIT to create Multics (Multiplexed Information and Computing Service).

In 1969 AT&T made a decision to withdraw Multics and go with GECOS (General Electric Comprehensive Operating Supervisor / System), with AT & T in Bells Lab when Multics was withdrawn some of the programmers named Ken Thompson and Dennis Ritchie decided to rewrite operating system in order to support low cost computer. The result was a system that a punning colleague called UNICS (UNiplexed Information and Computing Service)--an 'emasculated Multics'. It was given the name UNIX by Brian Kernighan as a pun on Multics. Hence Ken Thompson and Dennis Ritchie developed freeware operating system in assembly language. Later on in 1973 UNIX was rewritten in C programming language.

Richard Stallman

In 1984 Richard Stallman announces the GNU (Gnu is Not a Uniux) project to develop the GNU operating system a complete Unix like operating system which is a freeware for both Kernal and Program under FSF (Free Software Foundation) which licensed under GPL (General Public License).

Andrew Tanenbaum

In 1987, under GPL license Andrew Tanenbaum developed inexpensive minimal Unix like operating system named MINIX which is limiting it to educational use.

Linus Trovald

Hence in 1991 Linus Torvalds (16 yrs old) a Finnish student began to developed its own kernel as MINIX (GNU PROJECT) + NEW UNIX KERNAL(LINUS) = LINUX. Which is complete operating system. He launch this operating system on internet under GPL license for freeware distribution. So anyone can obtain this source codes and they can rewrite their own operating system.

Following are the companies who adopted Linux kernel’s and created its own operating system.

NAME OF THE COMPANY OPERATING SYSTEM

1. IBM AIX

2. HP HP / UX

3. SUN SOLARIS

What is an Operating System??

SIMPLE OPERATING SYSTEM DIAGRAM

The operating system is the most important type of system software in a computer system. A user cannot run an application program on the computer without an operating system, unless the application program is self-booting. An operating system (OS) is a resource manager. It takes the form of a set of software routines that allow users and application programs to access system resources (e.g. the CPU, memory, disks, modems, printers network cards etc.) in a safe, efficient and abstract way. An OS also provides convenient abstractions (such as files rather than disk locations) which isolate application programmers and users from the details of the underlying hardware. And Operating System is made up of two parts i.e. Shell and Kernal.

Shell or Software:-A Shell is a command interpreter and it can execute no of commands with in single command inlogical order known as shell script.The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs when they terminate, the shell gives the user another prompt.

Kernel :-The kernel is the hub of the operating system, it allocates time and memory to programs and handles the file store andcommunications in response to system calls. Kernel is a group of programs written in c language tointeract with hardware directly.The kernel is the central part of an operating system, that directly controls the computerhardware. Usually, the kernel is the first of the user-installed software on a computer, booting directly after the BIOS. Operating system kernels are specific to the hardware on which they are running, thus most operating systems are distributed with different kernel options that are configured when the system is installed.

Overview of the Linux System

Linux is multi user, multi process and multi task operating system. Linux is described as Kernel and Shell.Linux is a Unix-like computer Operating System (or OS) that uses the Linux kernel. Linux started out as a personal computer system used by individuals, and has since gained the support of several large corporations, such as Sun Microsystems, HP and IBM. It is now used mostly as a server operating system, with some large organizations using an enterprise version for desktops. Linux is a prime example of open-source development, which means that the source code is available freely for anyone to use.

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