Linux :
Linux less frequently 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 on September 17, 1991 by
Linus Torvalds. The Free Software Foundation uses the name
GNU/Linux to describe the operating system, which has led to some controversy.
Linux was originally developed for personal computers based
on the Intel x86 architecture, but has since been ported to more platforms than
any other operating system. Because of the dominance of the Linux
kernel-based Android OS on smartphones, Linux has the largest installed base of
all general-purpose operating systems. Linux is also the leading operating
system on servers and other big iron systems such as mainframe computers, and
is used on 99.6% of the TOP500 supercomputers. It is used by around
2.3% of desktop computers. The Chromebook, which runs the Linux
kernel-based Chrome OS, dominates the US K–12 education market and represents
nearly 20% of the sub-$300 notebook sales in the US. Linux also runs on
embedded systems – devices whose operating system is typically built into the
firmware and is highly tailored to the system. This includes TiVo and similar
DVR devices, network routers, facility automation controls,
televisions, video game consoles and smartwatches. Many smartphones
and tablet computers run Android and other Linux derivatives.
The development of Linux is one of the most prominent
examples of free and open-source software collaboration. The underlying source
code may be used, modified and distributed—commercially or non-commercially—by
anyone under the terms of its respective licenses, such as the GNU General
Public License.
Typically, Linux is packaged in a form known as a Linux
distribution (or distro for short) for both desktop and server use. Some of the
most popular and mainstream Linux distributionsare Arch Linux,
CentOS, Debian, Fedora, Gentoo Linux, Linux Mint, Mageia, openSUSE and Ubuntu,
together with commercial distributions such as Red Hat Enterprise Linux and
SUSE Linux Enterprise Server. Distributions include the Linux kernel,
supporting utilities and libraries, many of which are provided by the GNU
Project, and usually a large amount of application software to fulfil the
distribution's intended use. Desktop Linux distributions include a windowing
system, such as X11, Mir or a Wayland implementation, and an accompanying
desktop environment such as GNOME or KDE Plasma 5; some distributions may also
include a less resource-intensive desktop, such as LXDE or Xfce. Distributions
intended to run on servers may omit all graphical environments from the
standard install, and instead include other software to set up and operate a
solution stack such as LAMP. Because Linux is freely redistributable, anyone
may create a distribution for any intended use.
History:
Antecedents:
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. First released in 1971,
Unix was written entirely in assembly language, as was common practice at the
time. Later, in a key pioneering approach in 1973, it was rewritten in the C
programming language by Dennis Ritchie (with the exception of some hardware and
I/O routines). The availability of a high-level language implementation of Unix
made its porting to different computer platforms easier.
Creation:
In 1991, while attending the University of Helsinki, Torvalds became curious about operating systems and frustrated by the licensing of MINIX, which at the time limited it to educational use only. He began to work on his own operating system kernel, which eventually became the Linux kernel.
Naming:
Linus Torvalds had wanted to call his invention "Freax", a portmanteau of "free", "freak", and "x" (as an allusion to Unix). During the start of his work on the system, some of the project's makefiles
included the name "Freax" for about half a year. Torvalds had already
considered the name "Linux", but initially dismissed it as too
egotistical.
In order to facilitate development, the files were uploaded to the FTP server (ftp.funet.fi) of FUNET in September 1991. Ari Lemmke, Torvalds' coworker at the Helsinki University of Technology
(HUT), who was one of the volunteer administrators for the FTP server
at the time, did not think that "Freax" was a good name. So, he named
the project "Linux" on the server without consulting Torvalds Later, however, Torvalds consented to "Linux".
Commercial and popular uptake:
Adoption of Linux in production environments, rather than being used
only by hobbyists, started to take off first in the mid-1990s in the
supercomputing community, where organizations such as NASA started to replace their increasingly expensive machines with clusters of inexpensive commodity computers running Linux. Commercial use followed when Dell and IBM, followed by Hewlett-Packard, started offering Linux support to escape Microsoft's monopoly in the desktop operating system market.
Current development:
Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries.Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.
Design:
A Linux-based system is a modular Unix-like
operating system, deriving much of its basic design from principles
established in Unix during the 1970s and 1980s. Such a system uses a monolithic kernel, the Linux kernel, which handles process control, networking, access to the peripherals, and file systems. Device drivers are either integrated directly with the kernel, or added as modules that are loaded while the system is running.
User interface:
The user interface, also known as the shell, is either a command-line interface (CLI), a graphical user interface (GUI), or through controls attached to the associated hardware, which is common for embedded systems. For desktop systems, the default mode is usually a graphical user interface, although the CLI is commonly available through terminal emulator windows or on a separate virtual console.CLI shells are text-based user interfaces, which use text for both input and output. The dominant shell used in Linux is the Bourne-Again Shell (bash), originally developed for the GNU project. Most low-level Linux components, including various parts of the userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication.
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Video input infrastructure:
Linux currently has two modern kernel-userspace APIs for handing video input devices: V4L2 API for video streams and radio, and DVB API for digital TV reception.Due to the complexity and diversity of different devices, and due to the large amount of formats and standards handled by those APIs, this infrastructure needs to evolve to better fit other devices. Also, a good userspace device library is the key of the success for having userspace applications to be able to work with all formats supported by those devices.
Development:
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 by far the most widely used.Some free and open-source software licenses 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 General Public License (GPL), is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU Project.
Community:
A distribution is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis, Debian being a well-known example. Others maintain a community version of their commercial distributions, as Red Hat does with Fedora, and SUSE does with openSUSE.In many cities and regions, local associations known as Linux User Groups (LUGs) seek to promote their preferred distribution and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. Many Internet communities also provide support to Linux users and developers. Most distributions and free software / open-source projects have IRC chatrooms or newsgroups. Online forums are another means for support, with notable examples being LinuxQuestions.org and the various distribution specific support and community forums, such as ones for Ubuntu, Fedora, and Gentoo. Linux distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list.
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Programming on Linux:
Linux distributions support dozens of programming languages.
The original development tools used for building both Linux applications and
operating system programs are found within the GNU toolchain, which includes
the GNU Compiler Collection (GCC) and the GNU Build System. Amongst others, GCC
provides compilers for Ada, C, C++, Go and Fortran. Many programming languages
have a cross-platform reference implementation that supports Linux, for example
PHP, Perl, Ruby, Python, Java, Go, Rust and Haskell. First released in 2003,
the LLVM project provides an alternative cross-platform 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, and in terms
of terminal programming or QuickBASIC or Turbo BASIC programming in the form of
QB64.
Hardware support:
The Linux kernel is a widely ported
operating system kernel, available for devices ranging from mobile
phones to supercomputers; it runs on a highly diverse range of computer architectures, including the hand-held ARM-based iPAQ and the IBM mainframes System z9 or System z10.
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