GNU in the context of Linux kernel

Linux (/ˈlɪnʊks/ LIN-uuks) is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution (distro), which includes the kernel and supporting system software and libraries—most of which are provided by third parties—to create a complete operating system, designed as a clone of Unix and released under the copyleft GPL license.

Thousands of Linux distributions exist, many based directly or indirectly on other distributions; popular Linux distributions include Debian, Fedora Linux, Linux Mint, Arch Linux, and Ubuntu, while commercial distributions include Red Hat Enterprise Linux, SUSE Linux Enterprise, and ChromeOS. Linux distributions are frequently used in server platforms. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses and recommends the name "GNU/Linux" to emphasize the use and importance of GNU software in many distributions, causing some controversy. Other than the Linux kernel, key components that make up a distribution may include a display server (windowing system), a package manager, a bootloader and a Unix shell.

The Linux Documentation Project (LDP) is a dormant all-volunteer project that maintains a large collection of GNU and Linux-related documentation and publishes the collection online. It began as a way for hackers to share their documentation with each other and with their users, and for users to share documentation with each other. Its documents tend to be oriented towards experienced users such as professional system administrators, but it also contains tutorials for beginners.

FreeBSD is a free-software Unix-like operating system descended from the Berkeley Software Distribution (BSD). The first version was released in 1993 developed from 386BSD, one of the first fully functional and free Unix clones on affordable home-class hardware, and has since continuously been the most commonly used BSD-derived operating system.

FreeBSD maintains a complete system, delivering a kernel, device drivers, userland utilities, and documentation, as opposed to Linux only delivering a kernel and drivers, and relying on third-parties such as GNU for system software. The FreeBSD source code is generally released under a permissive BSD license, as opposed to the copyleft GPL used by Linux. The project includes a security team overseeing all software shipped in the base distribution. Third-party applications may be installed using the pkg package management system or from source via FreeBSD Ports. The project is supported and promoted by the FreeBSD Foundation.

A Linux distribution, often abbreviated as distro, is an operating system that includes the Linux kernel for its kernel functionality. Although the name does not imply product distribution per se, a distro—if distributed on its own—is often obtained via a website intended specifically for the purpose. Distros have been designed for a wide variety of systems ranging from personal computers (for example, Linux Mint) to servers (for example, Red Hat Enterprise Linux) and from embedded devices (for example, OpenWrt) to supercomputers (for example, Rocks Cluster Distribution).

A distro typically includes many components in addition to the Linux kernel. Commonly, it includes a package manager, an init system (such as systemd, OpenRC, SysVinit, or runit), GNU tools and libraries, documentation, IP network configuration utilities, the getty TTY setup program, and many more. To provide a desktop experience (most commonly the Mesa userspace graphics drivers) a display server (the most common being the X.org Server, or, more recently, a Wayland compositor such as Sway, KDE's KWin, or GNOME's Mutter), a desktop environment (most commonly GNOME, KDE Plasma, or Xfce), a sound server (usually either PulseAudio or more recently PipeWire), and other related programs may be included or installed by the user.

Since the 1990s, there has been ongoing debate over whether operating systems that use the Linux kernel in combination with GNU software should be referred to as Linux or GNU/Linux.

Supporters of the term Linux argue that it is more widely used in the media and by the general public, and that it serves as a practical shorthand for systems that combine the Linux kernel with software from a variety of sources, including the GNU Project.

Objective-C is a high-level general-purpose, object-oriented programming language that adds Smalltalk-style message passing (messaging) to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTSTEP operating system. Due to Apple macOS’s direct lineage from NeXTSTEP, Objective-C was the standard language used, supported, and promoted by Apple for developing macOS and iOS applications (via their respective application programming interfaces (APIs), Cocoa and Cocoa Touch) from 1997, when Apple purchased NeXT, until the introduction of the Swift language in 2014.

Objective-C programs developed for non-Apple operating systems or that are not dependent on Apple's APIs may also be compiled for any platform supported by GNU GNU Compiler Collection (GCC) or LLVM/Clang.

S is a statistical programming language developed primarily by John Chambers and (in earlier versions) Rick Becker, Trevor Hastie, William Cleveland and Allan Wilks of Bell Laboratories. The aim of the language, as expressed by John Chambers, is "to turn ideas into software, quickly and faithfully". It was formerly widely used by academic researchers., but has now been superseded by the partially backwards compatible R language, a part of the GNU free software project. S-PLUS was a widely used commercial implementation of S that was formerly sold by TIBCO Software.

The GNU Compiler Collection (GCC) (formerly GNU C Compiler) is a collection of compilers from the GNU Project that support various programming languages, hardware architectures, and operating systems. The Free Software Foundation (FSF) distributes GCC as free software under the GNU General Public License (GNU GPL). GCC is a key component of the GNU toolchain which is used for most projects related to GNU and the Linux kernel. With roughly 15 million lines of code in 2019, GCC is one of the largest free programs in existence. It has played an important role in the growth of free software, as both a tool and an example.

When it was first released in 1987 by Richard Stallman, GCC 1.0 was named the GNU C Compiler since it only handled the C programming language. It was extended to compile C++ in December of that year. Front ends were later developed for Objective-C, Objective-C++, Fortran, Ada, Go, D, Modula-2, Rust and COBOL among others. The OpenMP and OpenACC specifications are also supported in the C and C++ compilers.