0 Linux Operating System

Linux ()is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released 5 October 1991 by Linus Torvalds.


Linux was originally developed as a free operating system for Intel x86-based personal computers. It has since been ported to more computer hardware platforms than any other operating system. It is a leading operating system on servers and other big iron systems such as mainframe computers and supercomputers:more than 90% of today's 500 fastest supercomputers run some variant of Linux, including the 10 fastest. Linux also runs on embedded systems (devices where the operating system is typically built into the firmware and highly tailored to the system) such as mobile phones, tablet computers, network routers, televisionsand video game consoles; the Android system in wide use on mobile devices is built on the Linux kernel.

Linux
Tux the penguin, mascot of Linux
Company /developer	Many
Programmed in	Various
OS family	Unix-like
Working state	Current
Source model	Free and open source software
Initial release	1991
Latest stable release	Kernel: 3.4.4  (22 June 2012; 3 days ago)
Latest unstable release	Kernel: 3.5-rc4  (24 June 2012; 1 day ago)
Marketing target	Personal computers, embedded devices, mobile devices, servers
Available language(s)	Multilingual
Available programming(s)	Many
Supported platforms	Alpha, ARM, AVR32, Blackfin,C6x, ETRAX CRIS, FR-V,H8/300, Hexagon, Itanium,M32R, m68k, Microblaze,MIPS, MN103, OpenRISC, PA-RISC, PowerPC, s390,S+core, SuperH, SPARC,TILE64, Unicore32, x86,Xtensa
Kernel type	Monolithic
User land	Various
Default user interface	Many
License	Many ("Linux" trademark owned by Linus Torvaldsand administered by the Linux Mark Institute)

Unix

The Unix operating system was conceived and implemented in 1969 at AT&T's Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. It was first released in 1971 and was initially entirely written in assembly language, a common practice at the time. Later, in a key pioneering approach in 1973, Unix was re-written in the programming language C by Dennis Ritchie (with exceptions to the kernel and I/O). The availability of an operating system written in a high-level language allowed easier portability to different computer platforms. With a legal glitch forcing AT&T to license the operating system's source code to anyone who asked, Unix quickly grew and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs. Free of the legal glitch requiring free licensing, Bell Labs began selling Unix as aproprietary product.

Richard Stallman, founder of the GNU project

GNU

The GNU Project, started in 1983 by Richard Stallman, had the goal of creating a "complete Unix-compatible software system" composed entirely of free software. Work began in 1984. Later, in 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete.Linus Torvalds has said that if theGNU kernel had been available at the time (1991), he would not have decided to write his own.

BSD

Although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD and FreeBSD descended, predated that of Linux.Linus Torvalds has said that if 386BSD had been available at the time, he probably would not have created Linux.

MINIX

In 1991 while attending the University of Helsinki, Torvalds became curious about operating systems and frustrated by the licensing of MINIX, which limited it to educational use only. He began to work on his own operating system which eventually became the Linux kernel.MINIX is an inexpensive minimal Unix-like operating system, designed for education in computer science, written by Andrew S. Tanenbaum. Starting with version 3 in 2005, MINIX has become free and redesigned for "serious" use.

Torvalds began the development of the Linux kernel on MINIX, and applications written for MINIX were also used on Linux. Later Linux matured and further Linux development took place on Linux systems. GNU applications also replaced all MINIX components, because it was advantageous to use the freely available code from the GNU project with the fledgling operating system. (Code licensed under the GNU GPL can be reused in other projects as long as they also are released under the same or a compatible license.) Torvalds initiated a switch from his original license, which prohibited commercial redistribution, to the GNU GPL. Developers worked to integrate GNU components with Linux to make a fully functional and free operating system.

        

Most Linux distributions support dozens of programming languages. The original development tools used for building both Linux applications and operating system programs are found within theGNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for Ada, C, C++, Java, and Fortran. First released in 2003, the Low Level Virtual Machine project provides an alternative open-source compiler for many languages. Proprietary compilers for Linux include the Intel C++ Compiler, Sun Studio, and IBM XL C/C++ Compiler. BASIC in the form of Visual Basic is supported in such forms as Gambas, FreeBASIC, and XBasic.

Most distributions also include support for PHP, Perl, Ruby, Python and other dynamic languages. While not as common, Linux also supports C# (via Mono), Vala, 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 and JikesRVM.

GNOME and KDE are popular desktop environments and provide a framework for developing applications. 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,CodeLite, Eclipse, Geany, ActiveState Komodo, KDevelop, Lazarus, MonoDevelop, NetBeans, Qt Creator and Omnis Studio, while the long-established editors Vim and Emacs remain popular.

The Free Software Foundation views Linux distributions that use GNU software as GNU variants and they ask that such operating systems be referred to as GNU/Linux or a Linux-based GNU system.The media and common usage, however, refers to this family of operating systems simply as Linux, as do many large Linux distributions (e.g. SUSE Linux and Mandriva Linux). Some distributions, notably Debian, use GNU/Linux. The naming issue remains controversial.