OPERATING SYSTEMS
An operating system is a layer of software which takes care of technical aspects of a computer's operation.
An operating system processes system data and user input, and responds by allocating and managing tasks
The main functions of operating systems are:
(i) A technical layer of software for driving the hardware of the computer, like disk drives, prioritizing system requests, controlling input and output devices, facilitating networking.
(ii) A file system which provides a way of organizing files logically, and
(iii) A simple command language which enables users to run their own programs and to manipulate their files in a simple way i.e. the operating system forms a platform for other system software and for application software
Most operating systems come with an application that provides a user interface for managing the operating system, such as a command line interpreter or graphical user interface.
Ex: for the command line interface O/S is DOS.
Ex for the graphical user interface O/S is LINUX.
Operating system can be classified based on the No. of users the system is using & the no of tasks the system is performing i.e. multi user and multi tasking.
HISTORY OF LINUX
Ø The history of Operating System starts in 1950's, with simple schemes for running batch programs efficiently, minimizing idle time between programs. Then, in early 1960s, several people use the same computer at the same time, from different terminals. Such systems were called time-sharing systems. Some of these were university research projects, others were commercial ones.
Ø One such project was Multics, which was started on 1965 and quite innovative at the time. For example, a hierarchical file system, something taken for granted in modern operating systems. The developers of Multics were GE, Massachusetts Institute of Technology (MIT ) and AT&T Bell Labs.
Ø Multics was written in Assembly Language and Later it was dropped on 1969.
Ø Then Bell Labs people I.e. Kane Thompson (C++) & Dennis Ritchie(C) started redesigning the MULTICS and developed a new OS called UNICS (Uniplexed Information & computing system)
Ø It’s was written in C and Assembly Languages, but most of code is written in C i.e. nearly 80% C and remaining 20% in Assembly Language.
Ø Later in 1973 they totally written UNICS in C Language and named as UNIX. Kane Thompson (C++) & Dennis Ritchie(C) are developers of UNIX. Later, UNIX got an implementation of the TCP/IP protocol stack. By 1990, UNIX had a strong position in the server market. Then UNIX had become commercial and rather expensive.
Ø The only other alternative option to a common person is DOS.
Ø Richard. M. Stall man is a employee of Bell Labs, came out of that company due to conditions kept by Bell Labs & started a project named FSF(FREE SOFTWARE FOUNDATION) in 1985. He was the author of GCC (GNOME C Compiler) & emacs (Editor). This project framed guidelines of General Public License of the organization of GNU (GNOME NOT UNIX). GNU project aims to share the software and views of programmers who were spreaded all over world.
Ø In 1987 A Dutch professor Andrew. S. Tannenbaum wrote 12000 lines of code to demonstrate students how the internal usage of operating system works. It is given with the book “Operating System Internals”. Later he sold these 12000 lines of code to a company, Open BSD(Open Barkley Software Development)
Ø There was also 386BSD, a precursor Net BSD, Free BSD, and Open BSD, but that wasn't mature yet, and required higher end hardware than many had at home.
Ø Linus Torvalds who studied the book of Andrew. S. Tannenbaum, a student of University of Helsinki. He was inspired by Richard. M. Stallman and he developed Linux & gave this Linux as Free Operating System.
Ø Kernel is the part that makes all other programs run. It implements multitasking, and manages hardware devices, and generally enables applications to do their thing. Linux itself is only the kernel of an operating system.
Ø All the programs that the user or system administrator actually interacts with, are run on top of the kernel. Ex: A command line interpreter (or shell), which is used both interactively and to write shell scripts (corresponding to .BAT files).
Ø Linus did not write these programs himself, and used existing free versions instead. He often changed the kernel to make it easier to get the existing programs to run on Linux, instead of the other way around.
Ø Most of the critically important system software, including the C compiler, came from the FFS GNU project. To credit them, many people like to refer to a Linux system as a GNU/Linux system. (GNU has there own kernel as well.)
Ø During 1992 and 1993, the Linux kernel gathered all the necessary features it required to work as a replacement for UNIX workstations, including TCP/IP networking and a graphical windowing system.
Ø Version 1.0 of the Linux kernel was released in March, 1994. Since then, the kernel has gone through many development cycles, each culminating in a stable version.
Ø Each development cycle has taken 18 to 24 months and has involved redesigning and rewriting large parts of the kernel to deal with changes in hardware (for example, new ways to connect peripherals, such as USB).
Ø Linux was first written for an Intel 386 processor, and naturally works on all successive processors. After about three years of development, Linux to other processor families as well, the first one was the Alpha processor (Digital Equipment Corporation)
Ø Today, Linux also runs on Sun SPARC and UltraSPARC, Motorola 68000, Power PC, PowerPC64, ARM, Hitachi Super H, IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64 and CRIS processors.
Linux Distributions
Ø A Linux distribution is a member of the Linux family of Unix-like computer operating systems. Such systems are built from the Linux kernel and assorted other packages, such as the X Window System and software from the GNU project.
Ø There are over three hundred Linux distributions available in day to day life. Most of the kernels & supporting packages are some combination of free software and open source.
Ø Linux distributions have taken a wide variety of forms — from fully featured desktop and server operating systems to minimal environments.
Ex: for development of embedded programs they is separate Linux O/S i.e. Hard Hat Linux, AMSEL (Advanced Modular Secure Embedded Linux), & so on
Ø These Linux distributions are constantly revising and improving their respective distributions, in order to update with the new hardware as well solves the problems of the old versions.
Ø The Linux distributions are compared based on these factors:
a. Whether it is commercial or non-commercial.
b. Designed for enterprise or for home usage.
c. Designed for servers, desktops, or embedded devices.
d. General purpose or highly specialized toward specific machine functionalities, for example firewalls, network routers, and computer clusters.
e. Targeted at specific user groups, for example through inclusion of many music production or scientific computing packages.
Ø One can distinguish between commercially backed distributions, such as Fedora (Red Hat), SUSE Linux (Novell), Ubuntu (Canonical Ltd.), and Mandriva Linux and community distributions such as Debian and Gentoo.
Ø Some the popular distributions are: -
i. Centos: - It is community enterprise operating system. The source RPMS of the Centos is taken from Red hat. It can support all the servers as well as desktop users same as Red hat O/S, but in Centos the support is not provided if any problem occurs.
ii. Debian GNU/Linux: - Debian GNU/Linux is a distribution produced by the Debian Project. The O/S produced by Debian will be 100% free as determined by the Debian Free Software Guidelines (DFSG).
iii. Fedora Linux: - It is formally known as fedora core. This Linux distribution is from Red hat organization, but this distribution was Free but no Support was provided.
iv. Gentoo: -Gentoo Linux is perhaps the most-used source-based Linux distribution. "Source-based" means you compile the operating system and its applications from source code, rather than installing binary packages. As a result, you can build a system that's optimized for your individual machine. This distribution distribution targeted at power users.
v. Mandriva: - Mandriva Linux is a consumer-oriented distribution available in both freely downloadable form and as a boxed retail product. Its parent company Mandriva is a Russian based company represents the combined might of three once separate Linux distributors: Mandrake, Conectiva, and Lycoris
vi. Suse Linux: - SUSE Linux is developed by Novell. This Linux family includes the commercial distribution SUSE Linux Enterprise Desktop (often referred to as SLED), several commercial server products targeting businesses, and the completely free-of-charge openSUSE.
vii. Ubantu: - Ubuntu is a community developed Linux distribution with the slogan "Linux for human beings." Ubuntu is one of the most popular Linux distributions for laptops and desktop machines, and is also gaining popularity on servers. Ubuntu is based on Debian GNU/Linux. The name "Ubuntu" is an African word that can be translated as "humanity towards others,”
viii. Knoppix: - Knoppix, a LiveCD distribution that runs completely from removable media and without installation to a hard disk.
ix. Red hat Linux: - Up to 9.0 versions it is free; later on the Red hat versions became commercial. Nower day it is the most successful commercial Linux version. The company offers versions of Red Hat Enterprise Linux (RHEL) for server and workstation configurations.
x. The flavors of Red hat in EL-4 is AS (Advanced Server), EL (Enterprise Linux), WS (Workstation).
Ø Red Hat Enterprise Linux AS [EL4]: The top -of- line Red Hat enterprise Linux Solution, this product supports the largest x86 suitable servers with the highest levels of support.
Ø b) Red Hat Enterprise Linux ES [EL4]: This is for entry-level or mid-range departmental servers. Red Hat Enterprise Enterprise Linux ES provides the same core capabilities as AS, for systems with up to two Physical CPUs and up to 8 GB of main memory.
Ø c) Red Hat Enterprise Linux WS [EL4]: The desktop/client partner for AS and WS on x86 compatible systems. It doesn't include some network server applications. It is ideal for desktop deployments
xi. Red Hat Enterprise Linux -5 : Red Hat Enterprise Linux scales from laptops, small servers to Largest SMP(Symmetric Multi Processor) Servers and to range them as per the architectures supporting and applications and service providing they rated as follows
Ø Red Hat Application Platform Server:
Ø Red Hat Application Server:
Ø Main Frame Computing Server:
Ø Red Hat Enterprise Linux Desktop with Multi-OS option:.
xii. Red hat gives 7 years of supports (24*7) from the date of release of that version, but not from the date of purchase of that version.
xiii. The latest version of RHEL is Red Hat Enterprise Linux 5, released in March 2007, contains more than 1200 components. All Beta versions of Red hat comes with comes Fedora & it is freely distributed. It is meant for standardization.
xiv. Finally it is better to selecting Linux distribution based on the features available, becoz each distribution offers the same base Linux kernel and system tools, but differ on installation method and bundled applications. Each distribution has its own advantages as well as disadvantages.
Desktop Environments
Ø GNOME: GNOME is Free Software and part of the GNU project, dedicated to giving users and developers the ultimate level of control over their desktops, their software, and their data.
Ø KDE: KDE is an international technology team that creates Free Software for desktop and portable computing. Among KDE’s products are modern desktop systems for Linux and UNIX platforms. KDE software is translated into more than 60 languages and is built with ease of use and modern accessibility principles in mind. KDE4's full-featured applications run natively on Linux, BSD, Solaris, Windows and Mac OS X. KDE include KOffice, KDevelop, Amarok, K3b and many others.
Ø The first version of KDE is released on 1996 by Matthias Ettrich. The latest announcements are KDE 3.5.8 released on 16 of October 2007, then on Jan 11th 2008 they new KDE version 4.0, recently they have given updates for KDE 4.0 as KDE 4.0.1 on 5 Feb. 2008.
Ø XPde Desktop Environment: It’s a complete desktop environment for Linux on x86. It tries to make easier for Windows XP users to use a Linux box. On August 21st 2004, the XPde Team released XPde 0.5.1, the release that includes a Start Menu and completes the desktop paradigm.
Ø Beryl: It is “3D” environment Desktop
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