GNU is an extensive collection of free software, which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operating systems popularly known as Linux. Most of GNU is licensed under the GNU Project's own General Public License (GPL).
GNU Hurd is a collection of microkernel servers written as part of GNU, for the GNU Mach microkernel. It has been under development since 1990 by the GNU Project of the Free Software Foundation, designed as a replacement for the Unix kernel, and released as free software under the GNU General Public License. When the Linux kernel proved to be a viable solution, development of GNU Hurd slowed, at times alternating between stasis and renewed activity and interest.
Minix is a POSIX-compliant, Unix-like operating system based on a microkernel architecture.
Plan 9 from Bell Labs is a distributed operating system, originating in the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s, and building on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 is free and open-source. The final official release was in early 2015.
Darwin is an open-source Unix-like operating system first released by Apple Inc. in 2000. It is composed of code derived from NeXTSTEP, BSD, Mach, and other free software projects' code, as well as code developed by Apple.
QNX is a commercial Unix-like real-time operating system, aimed primarily at the embedded systems market. QNX was one of the first commercially successful microkernel operating systems. As of 2020, it is used in a variety of devices including cars and mobile phones.
L4 is a family of second-generation microkernels, used to implement a variety of types of operating systems (OS), though mostly for Unix-like, Portable Operating System Interface (POSIX) compliant types.
Cisco Internetwork Operating System (IOS) is a family of network operating systems used on many Cisco Systems routers and current Cisco network switches. Earlier, Cisco switches ran CatOS. IOS is a package of routing, switching, internetworking and telecommunications functions integrated into a multitasking operating system. Although the IOS code base includes a cooperative multitasking kernel, most IOS features have been ported to other kernels such as QNX and Linux for use in Cisco products.
The V operating system is a discontinued microkernel distributed operating system that was developed by faculty and students in the Distributed Systems Group at Stanford University from 1981 to 1988, led by Professors David Cheriton and Keith A. Lantz. V was the successor to the Thoth operating system and Verex kernel that Cheriton had developed in the 1970s. Despite similar names and close development dates, it is unrelated to UNIX System V.
XNU is the computer operating system (OS) kernel developed at Apple Inc. since December 1996 for use in the Mac OS X operating system and released as free and open-source software as part of the Darwin OS, which is the basis for the Apple TV Software, iOS, iPadOS, watchOS, and tvOS OSes. XNU is an abbreviation of X is Not Unix.
JavaOS is an operating system based on a Java virtual machine and predominantly used on SIM cards to run applications on behalf of operators and security services. It was originally developed by Sun Microsystems. Unlike Windows, macOS, Unix, or Unix-like systems which are primarily written in the C programming language, JavaOS is primarily written in Java. It is now considered a legacy system.
HelenOS is an operating system based on a multiserver microkernel design. The source code of HelenOS is written in C and published under the BSD-3-Clause license.
A hybrid kernel is an operating system kernel architecture that attempts to combine aspects and benefits of microkernel and monolithic kernel architectures used in computer operating systems.
Visual Studio Tools for Applications (VSTA) is a set of tools that independent software vendors (ISVs) can use to build customization abilities into their applications for both automation and extensibility. Those customization abilities can be used by end-users to tailor the ISV's application within a managed extensibility environment just like Visual Basic for Applications.
The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system. It is the portion of the operating system code that is always resident in memory, and facilitates interactions between hardware and software components. A full kernel controls all hardware resources via device drivers, arbitrates conflicts between processes concerning such resources, and optimizes the utilization of common resources e.g. CPU & cache usage, file systems, and network sockets. On most systems, the kernel is one of the first programs loaded on startup. It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit.
Symbian is a discontinued mobile operating system (OS) and computing platform designed for smartphones. Symbian was originally developed as a proprietary software OS for PDAs in 1998 by the Symbian Ltd. consortium. Symbian OS is a descendant of Psion's EPOC, and was released exclusively on ARM processors, although an unreleased x86 port existed. Symbian was used by many major mobile phone brands, like Samsung, Motorola, Sony Ericsson, and above all by Nokia. It was also prevalent in Japan by brands including Fujitsu, Sharp and Mitsubishi. As a pioneer that established the smartphone industry, it was the most popular smartphone OS on a worldwide average until the end of 2010, at a time when smartphones were in limited use, when it was overtaken by iOS and Android. It was notably less popular in North America.
Phantom OS is an operating system (OS) made by mostly Russian programmers. It is based on a concept of persistent virtual memory, and uses managed code. It is one of a few OSes not based on classic concepts of Unix-like systems. Its primary goal is to achieve simplicity and effectiveness in both the operating system and application software at the same time. It is free and open-source software (FOSS) released under a GNU Lesser General Public License (LGPL).
Redox is a Unix-like microkernel operating system written in the programming language Rust, which has a focus on safety, stability, and performance. Redox aims to be secure, usable, and free. Redox is inspired by prior kernels and operating systems, such as SeL4, MINIX, Plan 9, and BSD. It is similar to GNU and BSD, but is written in a memory-safe language. It is free and open-source software distributed under an MIT License.
Ghost OS is an open-source hobbyist operating system and kernel. It is under development since 2014 and currently compatible with the x86 platform.
Genode is a free and open-source software operating system (OS) framework consisting of a microkernel abstraction layer and a set of user space components. The framework is notable as one of the few open-source operating systems not derived from a proprietary OS, such as Unix. The characteristic design philosophy is that a small trusted computing base is of primary concern in a security-oriented OS.
