User:NotSureWhatToPutHere/Sandbox

Note: This is a work in progress. Help wanted to cover some more complex OSes like Synthesis or seL4. I also propose we put less "relevant" OSes like the bajizillionth Unix clone under a new #Other alternative operating systems section rather than #Notable alternative operating systems.

Notable alternative operating systems

CP/M & DOS

CP/M was once a popular OS for 8080-based microcomputers that spawned several derivatives, some of which have survived into the 21st century, among them the DOS family. CP/M itself was mainly used on the Z80 and compatibles, a considerably enhanced 8080 derivative, for business applications.

FreeDOS

A libre x86 OS, which aims to be fully compatible with MS-DOS 6.0, its last standalone version. It's optionally shipped as the default OS for certain laptops, as a Windows alternative.

CP/M-65

A native CP/M port to the also hugely popular 6502, still under active development.

BSDs

The Berkeley Software Distribution (Wikipedia) was a widely adopted OS based on the original Research Unix source code, that brought many innovations to the post-Unix world, including Berkeley sockets. BSD itself disappeared mainly due to legal issues that made it lose momentum, but a series of contemporary systems emerged from the combination of the libre 386BSD port of 4.3BSD Net/2, the first distribution free of any AT&T code, and 4.4BSD-Lite2, the last improved BSD release.

NetBSD (website)

The first 386BSD fork, focuses on simplicity, clarity, and portability, the latter being its most well-known attribute. It's also the original home of the cross-platform pkgsrc package management system.

OpenBSD (website)

Forked from NetBSD, and originally having similar goals, it's become security-oriented and the source of lots of related features, such as W^X and kernel randomization. It has also spawned many userland subprojects, including LibreSSL, an OpenSSL fork subject to stricter security standards, OpenSSH, and Xenocara, its own Xorg build system/framework.

FreeBSD (website)

A more general purpose OS, and correspondingly popular BSD, especially for web serving purposes, it's considered by some to be the most direct 386BSD continuation. It's one of the few current Unices to still include compatibility layers for others by default, among them Linux and SVR4. It's also the home of the OpenZFS project, an effort to continue the open source development of Sun's ZFS, and the has served as the basis of many other distributions.

DragonFlyBSD (archived website)

Originally forked from FreeBSD due to performance concerns, it features an hybrid kernel greatly influenced by AmigaOS, and provides message passing, userland kernel virtualization, a dynamic devfs, and the HAMMER file system family.

TempleOS

Meant to be God's third temple, Temple OS (website) is a lightwight x86_64 OS built by its sole developer, Terry A. Davis in HolyC, a more dynamic C version of his invention, over the course of several decades.

ZealOS is a modernized, maintained fork, that strives to be simple, documented, and easily understandable over the course of a few days.

Collapse OS

Collapse OS, also known as the OS for the end of the world, is a cross-platform 8-bit OS, whose stated goal is to preserve the ability to program microcontrollers after the second stage of civilizational collapse. It's currently considered completed. Dusk OS, its 32-bit counterpart, designed to be useful during the first stage of the collapse, is under active development, however.

Plan 9

Plan 9 from Bell Labs is a distributed research OS that was supposed to replace its predecessor, 10th Edition Unix. It takes the everything is a file concept to the extreme via per-process namespaces and virtual files that effectively act as textual IPC. Both UTF-8 and the 9P protocol were originally implemented by Plan 9, the former as a way to support Unicode in a backwards-compatible way, and the latter as the unified medium-agnostic way to provide and consume inter-process services.

9front

The most popular fork, it started as a continuation due to a perceived lack of devoted development resources inside Bell Labs, and has accumulated various fixes and improvements, including better hardware support, updated drivers, and new utilities.

Inferno

A more indirect descendant, its kernel features the Dis register-based virtual machine, a JIT compiler, and some built-in modules for Limbo, a type-safe concurrent programming language. It can also run as an userspace program over Plan 9, Windows, and various Unices.