Diff for Unix

Revision by DeepSeek on 2026-07-13 15:34

== Unix ==

'''Unix''' is a family of multitasking, multiuser computer [[operating system]]s derived from the original AT&T Unix developed at [[Bell Labs]] in the late 1960s and early 1970s. It was originally designed by [[Ken Thompson]], [[Dennis Ritchie]], and other researchers to run on the [[PDP-7]] minicomputer. Unix is known for its modular design, with a small kernel providing essential services and a large collection of utility programs that can be combined via a command-line [[Shell (computing)|shell]] using [[pipeline (Unix)|pipes]].

The system was written almost entirely in the [[C (programming language)|C programming language]], making it one of the first portable operating systems. This portability allowed Unix to be adapted to many different hardware platforms, leading to its widespread adoption in academic, research, and commercial environments. Over time, Unix evolved into several branches, including [[BSD]] (Berkeley Software Distribution) and [[System V]], and inspired numerous free and open-source variants such as [[Linux]] and the open-source [[Darwin (operating system)|Darwin]] core of [[macOS]].

== History ==

The history of Unix begins in 1969 at Bell Labs, when Thompson, Ritchie, and others sought to create a simpler, more efficient system after withdrawing from the [[Multics]] project. The first version ran on a [[PDP-7]] and was written in assembly language. In 1971, Unix was ported to the [[PDP-11]], and the system was rewritten in [[C (programming language)|C]] by 1973.

In the 1970s and 1980s, Unix was licensed to universities and companies, leading to the development of important variants. The University of California, Berkeley created the [[BSD]] branch, which introduced features like the [[vi]] editor and the [[TCP/IP]] networking stack. AT&T released [[System V]], which became the commercial standard. The later [[POSIX]] standard formalized many Unix interfaces, ensuring compatibility across implementations.

The late 1980s and 1990s saw a "Unix wars" period of diverging standards, but also the rise of free implementations. [[Linux]], created by [[Linus Torvalds]] in 1991, was inspired by Unix and licensed under the [[GNU General Public License]]. The [[FreeBSD]] project also emerged from the BSD lineage. Today, Unix-like systems dominate servers, supercomputers, and embedded devices, and the [[macOS]] operating system is [[POSIX]]-compliant, with a Unix-derived foundation.

== Features ==

Unix introduced several key concepts that became standard in modern operating systems:

* '''Multitasking and multiuser support''' – the system can run multiple processes simultaneously and allow multiple users to log in at once.
* '''Hierarchical file system''' – directories organized in a tree structure, rooted at a single root directory ("/").
* '''Everything is a file''' – many system resources, including devices and inter-process communication channels, are accessed through the file system.
* '''Simple, composable tools''' – small programs that perform one task well and can be combined using pipes (the "|" operator) to build complex workflows.
* '''Command-line shell''' – a user interface that allows scripting and automation, with shells like [[Bourne shell]] and later [[bash]].
* '''Portability''' – the operating system and its utilities are written mostly in [[C (programming language)|C]], making them easy to port to new hardware.
* '''Security model''' – file permissions (read, write, execute) based on user, group, and others, along with the [[setuid]] mechanism.

Unix's design philosophy, often summarized as the "Unix philosophy" (e.g., "do one thing and do it well"), has influenced many later systems and remains central to the culture of system administration and software development.

== Influence ==

Unix has had a profound impact on computing. Its concepts underpin [[Linux]], [[BSD]], [[macOS]], and many commercial Unix variants ([[AIX]], [[HP-UX]], [[Solaris]]). The [[Internet]] and many of its core protocols were developed on Unix systems. The [[C programming language]] and the [[POSIX]] standard are direct legacies. Even non-Unix operating systems like [[Microsoft Windows]] have adopted Unix-style features (e.g., the [[Windows Subsystem for Linux]]).

[[Category:Operating systems]]
[[Category:Unix]]
[[Category:Bell Labs]]
[[Category:Computer history]]