LINUX

Linux is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; typically all underlying source code can be freely modified, used, and redistributed by anyone.

The Linux kernel was first released to the public on 17 September 1991, for the Intel x86 PC architecture. The kernel was augmented with system utilities and libraries from the GNU project to create a usable operating system, which led to an alternative term, GNU/Linux. Linux is packaged for different uses in Linux distributions, which contain the sometimes modified kernel along with a variety of other software packages tailored to different requirements.

Predominantly known for its use in servers, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, supercomputers, video game systems, such as PlayStation 2, 3, several arcade games, and embedded devices, such as mobile phones and routers.

The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open source software. Linux is not the only such operating system, although it is the best-known and most widely used. Some free and open source software licences are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU GPL, is used for the Linux kernel and many of the components from the GNU project.

As an operating system underdog competing with mainstream operating systems, Linux cannot rely on a monopoly advantage; in order for Linux to be convenient for users, Linux aims for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX, SUS, ISO, and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.

Programming on Linux

Most Linux distributions support dozens of programming languages. The most common collection of utilities for building both Linux applications and operating system programs is found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for C, C++, Java, Ada and Fortran. The Linux kernel itself is written to be compiled with GCC.

Most also include support for Perl, Ruby, Python and other dynamic languages. Examples of languages that are less common, but still well-supported, are C# via the Mono project, and Scheme. A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM's J2SE RE, as well as many open-source projects like Kaffe. The two main frameworks for developing graphical applications are those of GNOME and KDE. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated development environments available including Anjuta, Code::Blocks, Eclipse, KDevelop, MonoDevelop, NetBeans, and Omnis Studio while the traditional editors Vim and Emacs remain popular.

Although free and open source compilers and tools are widely used under Linux, there are also proprietary solutions available from a range of companies, including the Intel C++ Compiler, PathScale, Micro Focus COBOL, Franz Inc and the Portland Group.

User interface

Linux is coupled to a text-based command line interface (CLI), though this is usually hidden on desktop computers by a graphical user interface (GUI). On small devices, input may be handled through controls on the device itself, and direct input to Linux might be hidden entirely.

The X Window System (X) is the predominant graphical subsystem used in Linux. X provides network transparency, enabling graphical output to be displayed on machines other than that which a program runs on. For desktop machines X runs locally.

Early GUIs for Linux were based on a stand-alone X window manager such as FVWM, Enlightenment, or Window Maker, and a suite of diverse applications running under it. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system. Because the X window managers only manage the placement of windows, their decoration, and some inter-process communication, the look and feel of individual applications may vary widely, especially if they use different graphical user interface toolkits.

This model contrasts with that of platforms such as Mac OS, where a single toolkit provides support for GUI widgets and window decorations, manages window placement, and otherwise provides a consistent look and feel to the user. For this reason, the use of window managers by themselves declined with the rise of Linux desktop environments. They combine a window manager with a suite of standard applications that adhere to human interface guidelines. While a window manager is analogous to the Aqua user interface for Mac OS X, a desktop environment is analogous to Aqua with all of the default Mac OS X graphical applications and configuration utilities. KDE, which was announced in 1996, along with GNOME and Xfce which were both announced in 1997, are the most popular desktop environments.

TOP LINUX DISTRIBUTIONS :

1. Red Hat

2. SuSE

3. Mandriva

4. Fedora

5. Debian

6. Gentoo

7. Knoppix

8. Ubuntu

9. Subuntu

10. Lycoris

11. Yellow Dog

12. Slackware