Android is a Linux-based operating system designed for touchscreen mobile devices. The first Android-powered phone was sold in October 2008.

This category treats software-oriented aspects of BIOSs. BIOS is an acronym for: Basic Input/Output System, of personal computers (PC). The BIOS is a chip inside a computer that starts (boots) the computer, runs the Power On Self Test (POST), and holds the buffers for sending information from any software in Random Access Memory (RAM), to any hardware device (via slots and ports) that information must go to. BIOS is also the name of the software that is inside, and runs from, a BIOS chip. The system as a whole is called 'the BIOS'. Making matters less clear, BIOS system and software are also termed 'firmware', to show that it is something that has traits between software and hardware. The PC BIOS was invented by the late programmer, and PC operating system (CP/M) pioneer Gary Kildall.

Boot Managers are small applications which allow a user to boot a computer into an operating system, or one of a selection of operating systems.

Capability, or capability-based, operating systems (OSs) are those which use, and are often structured via, capabilities (in some systems called a key), for security. Many OSs, such as Unix types, or later versions of Microsoft Windows, use privileges for security. Privileges apply to users, and are course-grained. Capabilities are somewhat similar, but apply to objects within the software environment, and are fine-grained. A capability is a communicable, unforgeable token of authority. It refers to a value that references an object, along with an associated set of access rights. User programs on capability OSs must use a capability to access an object; they are designed to directly share capabilities with each other according to the principle of least privilege, and with the OS infrastructure needed to make such transactions efficient and secure.

This category lists operating systems (OSs) based on closed source code. Some such OSs have open source variants (BeOS, DOS, Unix, VMS), or straddle these two licensing models (QNX). Closed Source computer programs, including OSs, are those that include no source code, and for which the source code is kept secret, or made available only for a fee, as in many realtime OSs.

This category contains sites dedicated to the various versions of the operating system CP/M, including historical information.

This category is for only websites cataloging operating systems (OSs), and related resources, via alphabetical or otherwise classified lists of resources, with no, or brief descriptions. For classified lists with more than brief descriptions, see Computers/Software/Operating_Systems/Guides.

This category covers operating systems (OSs) which were created, and have as a main or major purpose, to educate and teach about OS concepts, design, programming, and/or larger, more general system issues; and/or support other types of education (networking, mathematics); OSs existing solely or in large part, to educate. Mostly the links in this category point to other OS categories and OSs there. The only OSs listed exclusively here are those for which no better or clearer category seems suitable.

Operating systems with a small footprint which run on devices with small resources.

Any operating system (OS) can be extended before runtime, by two means: 1) Programming; if one has the source code, by programming (coding) and then compiling the new code into a new system, and/or, 2) Patches; by applying patches into a system. Extensible OS is the accepted term for what can be more precisely and correctly termed a runtime extensible OS. In such systems, application and/or user software, with normal user privileges, can provide extensions to OS (kernel) functions during runtime to adjust OS behavior to application needs, with good safety, security, and efficiency (enough to be useful). Such runtime modifiability is similar to what a reflective OS allows, and can be viewed as a limited type of (application-level) OS reflectivity. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OSs. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

Firefox OS is a Linux-based open-source operating system for smartphones and tablet computers. Its project name was Boot to Gecko (B2G). It is being developed by Mozilla, the non-profit organization best known for the Firefox web browser. Firefox OS runs HTML5-based web apps.

This category holds links for operating systems (OSs) based on, or which use heavily, functional programming and languages, and related topics, for which this is the main rationale.

This category holds links on Graphical User Interfaces (GUI, pronounced "Gooey"), and software and toolkits that support implementing and deploying graphics on computers, usually but not always via operating systems. GUI is a general name for any computer interface that substitutes graphics for hardware character generators. GUIs usually work via a keyboard and a pointing device such as a joystick, mouse, touchpad, trackball, and/or others.

This category is for only websites cataloging operating systems (OSs), and related resources, via alphabetical or otherwise classified lists of resources, with more than brief descriptions. For classified lists with no, or only brief descriptions, see Computers/Software/Operating_Systems/Directories.

Operating systems used to run mobile devices with small resources.

Formerly known as iPhone OS, iOS is the operating system developed and distributed by Apple for the iPhone, iPod Touch and the iPad.

Linux is a free Unix-type operating system originally created by Linus Torvalds and constantly developed further with the assistance of many developers from around the world. Linux includes true multitasking, virtual memory, shared libraries, demand loading, proper memory management, TCP/IP networking, and other features common with modern operating systems. Developed under the GNU General Public License, the source code for Linux is freely available to everyone. Linux can be downloaded for free off the Internet. There are many applications that provide Linux with the power and stability it enjoys today. The Linux category contains resources related to Linux and the Linux ecosystem.

The Mac OS is the original and still most popular operating system for the various versions of the Apple Macintosh computer, and Power PC. It was the first graphical window, menu, and icon based personal computer operating system, and had a strong influence on many other Operating Systems, such as the later Windows versions.

Mainframe computers are large systems that usually completely fill one or more rooms. Older makers: Burroughs, Honeywell, IBM, Sperry, Univac. Current makers: Unisys; of IBM compatible mainframes: Fujitsu Ltd., its US subsidiary Amdahl, Hitachi Ltd., IBM. IBM now dominates this market. Most other makers have been merged out of existence. Sperry and Univac merged into Sperry-Univac in 1955. Burroughs and Sperry merged into Unisys in 1986.

MeeGo is a Linux-based mobile operating system. It came to exist in 2010 as the merger of Intel’s Moblin project and Nokia’s Maemo project. It was hosted by the Linux Foundation, but it canceled MeeGo in September 2011 in favor of Tizen.

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When the collaboration began, Nokia was already developing the next version of Maemo. The Maemo 6 base was kept intact, but the Handset UX was shared, and the name changed to “MeeGo/Harmattan”. This powered the Nokia N9 smartphone.

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MeeGo’s successor is Mer, a fork of MeeGo.

This category is on operating systems (OSs) which main trait is that they have a microkernel architecture. A microkernel is a minimal OS kernel providing only basic OS services (system calls), while other services (usually done by kernels) are done by user-space programs called servers. Usually, microkernels provide services such as address space (memory) management, thread management, and inter-process communication, but not networking, or display. Later extensions of microkernel designs led to new architectures such as nanokernels, exokernels, and hardware abstraction layers (HAL). Monolithic kernels (DOS, Linux, most Unix, Windows, etc.) go in their own category. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OS. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

The Windows operating system is designed by the Microsoft Company.

Midrange computers were once called minicomputers. They have capacities in between desktop and mainframe computers, and sizes between a 19" color TV and a large refrigerator. Historical firms in this market were Data General, Digital Equipment Corp. (DEC), IBM, Prime. Compaq (via DEC merger) and IBM now dominate this market. Compaq (via DEC merger) makes and sells VMS, IBM makes and sells OS/400. Compaq bought and merged with DEC a few years ago and acquired VMS.

Most operating systems (OSs) in use are monolithic. In these, all source code is compiled into one logically undivided block of object code, though the source and/or object code may be segmented into different address spaces, unlike in a Single Address Space OS (SASOS). On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OSs. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

Network operating systems (NOSs) are OSs that exist mostly or fully for, which main reason for being, is to facilitate networking, between two or more computers, to operate and improve networks, with non-trivial networking (e.g., routing) included and/or built in, which need not be added later, and make little sense without their network functions. Many OSs have some networking ability, but not all such OSs are NOSs. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OS. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

This category is for object-oriented (OO) operating systems (OSs): OSs structured, organized, using all, most, or many of the principles of OO programming and related languages. Some such OSs are OO languages (Oberon, Self, Smalltalk, Squeak), some are written in OO languages (Java OSs in Java, Choices in C++), and some are written in procedural languages using OO structuring (GEOS and Unununium in Assembly). Of the later, many highly component-oriented OSs are also highly OO like, and are also listed here. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OS. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

This category lists operating systems (OSs) based on open source code. Some such OSs have closed source variants (BeOS, DOS, Unix, VMS), or straddle these two licensing models (QNX). Open Source computer programs (OSs are programs) are those that include source code, and/or for which the source code is freely available, or made available without a fee or limited permissions. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OS. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type. These links occupying the top of this page, above the links with descriptions, lead to other directory categories which hold open source OSs which have other, more distinctive traits that identify them as members of some class of OS found in the current directory taxonomy. OSs listed in this category are those that have no other distinctive traits by which to classify them in the current taxonomy. These all seem to have monolithic kernels. An OS is listed in this category if there seems no clearer, more specific category for it. This category also has some other links that are hard to fit elsewhere, of which there are always a few.

Open WebOS is a Linux operating system. Palm launched WebOS in January 2009 as the successor to Palm OS. It was acquired by Hewlett-Packard.

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After the failure of the HP TouchPad and the proposed sale of the HP Personal Systems Group, HP made the platform open source, and it became Open WebOS.

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WebOS was purchased by LG Electronics, which intends to use it for smart TVs.

This category contains resources related to the OS/2 and eComStation operating systems.

Parallel operating systems (OSs) are written for computers using two or more processors (called nodes), and where such processors are usually nearby each other, and usually linked via buses, and not networks. Parallel computers can run many types of programs far faster than normal one-processor computers, depending on the type of problem being computed. Programs written for, that work on, one-processor computers don't automatically work on parallel computers; programmers must specify explicitly how to divide computing work between all available nodes. Information on programming for parallel computers is in Parallel_Computing/Programming. Many libraries exist to help programmers write applications for parallel computers. Parallel computing is similar to distributed computing. Both involve dividing problems into pieces and assigning each part to one or more processors. Parallel computer nodes usually communicate with each other heavily during computations; distributed computer nodes usually communicate with each other lightly during computations, often because they are varying distances apart. Sites related to distributed computing are in Computers/Computer_Science/Distributed_Computing.

Persistence is the trait of maintaining system state despite discontinuities in operation or use, such as from one use of a program to the next use. In simple terms, persistent programs lose no, or little, information if the system becomes inoperative suddenly. As most computer users know, many computers often become inoperative suddenly, for two main reasons: the electric power stops, or a program crashes. Persistent operating systems (OSs) are OSs that maintain global persistence for all threads, processes, and programs that are running, as they run. When using persistent OSs, if the plug is pulled out suddenly, and the screen goes black, the computer can be plugged back in, and is up and running again quickly, almost exactly where it left off, losing no, or little (at most only a few seconds) work. Clearly, this demands some effort by designers, but is not difficult if one is willing to suffer a small performance loss. The difficulty lies in designing programs that are persistent with no performance lose.

All operating systems (OSs) in this category support POSIX standards fully or partly. POSIX is an acronym for: Portable Operating System Interface for UniX. Much like TRON, POSIX is not a body of computer code that is compiled and run on some processor. Rather, it is a set of standards (IEEE 1003.1): interfaces, design guidelines, software design specifications, defining (for creating) the computer code that will become language interfaces between an OS kernel and its programs, to give compatibility when moving programs between compatible systems. POSIX is made mostly of features from BSD Unix and Unix System V. Much like Open Source software, all POSIX standards are copyrighted (by the Institute of Electrical and Electronics Engineers, Inc., IEEE; new versions have joint copyright by IEEE and Open Group), but available for use by software developers anywhere in the world for free. Thus the OS architecture based on POSIX is an open architecture that invites and welcomes cloning and interoperability. On this page, OSs are arranged in three groups and levels: 1) Top group: issues spanning multiple unrelated OSs. 2) Middle group: types or classes of OS. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

Information about the PRIMOS Operating System developed by Pr1me Computers.

This category has information on only RealTime Operating Systems (RTOSs), and closely related material. Realtime systems are not the same as embedded systems. Realtime OSs can be used in general purpose computers, and in embedded types. Some embedded OSs are not realtime, and cannot serve some uses. Why segregate RTOSs so fully? Three clear reasons exist: 1) The functional divide between RTOSs and non-RTOSs is large, which profoundly effects design: all OSs must provide logically correct/precise results, but RTOSs must go beyond this and give temporal (time) correctness. RTOSs are the only logical and safe choice for time-critical uses. 2) More RTOSs than non-RTOSs (fewer non-RTOSs than RTOSs) are in use, in this solar system at least. 3) Directory user needs are different: those seeking information on RTOSs usually need no information on non-RTOSs, and vice versa, those interested in non-RTOSs usually need no information on RTOSs. On this page, links are arranged in three groups and levels: 1) Top group: issues spanning multiple unrelated OSs. 2) Middle group: types or classes of OS, or OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

Reflection: a method or means to let a system maintain information about itself (meta-information), and to use such to alter its behavior, to change, adapt; something acting upon itself. This is higher-order behavior than strict imperative models. More concretely, reflection is also an ability (for users) to modify software (even system software) of the underlying system during runtime, without leaving that system. Most programs written today are not reflective. With non-reflective systems, if one modifies (edits) any source code, one must recompile, and then restart it, thus leaving the system. With a reflective system, one can modify code (even kernel code), recompile, and replace the running system code as the system runs, with no restarting, rebooting, or often even leaving the editor. This allows and promotes more dynamic, fluid, productive work style. Such runtime modifiability is similar to what an extensible operating system (OS) allows, which can be viewed as a limited type of (application-level) OS reflectivity. Reflection, where program = data, simplifies writing compilers, interpreters, optimizers, theorem provers, and defining higher order functions. Reflective OSs are those that take advantage of such traits and abilities, to various ends. Many exist. Some are used daily, in working systems, but they do not dominate, and are not mainstream, yet. They are a very interesting and promising class of program. Some are found in research, where they form a fascinating branch of computer science. Some experts say they will grow more important in the future as computer power rises, programs grow more complex, and artificial intelligence properties are grafted onto, or blended with, OSs. Or, like so many other technologies, they may remain more marginal, used only in certain areas and applications. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OSs. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

This category is for operating systems (OSs) which main purpose is research into OSs and into larger, more general system issues. Mostly the links in this category point to other OS categories and OSs therein. The only OSs listed exclusively herein are those for which no better or clearer category seems suitable. On this page, OSs are arranged in two groups and levels: 1) Top group: types or classes of OSs, where research is more commonly done, experimental OSs are more likely to be found. 2) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

Sailfish OS is a Linux-based mobile operating system developed by Jolla in cooperation with the Mer project and supported by the Sailfish Alliance.

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Mer is a mobile-oriented software distribution, targeted at hardware vendors to serve as a base for Linux-based operating systems. It is an important element of the Sailfish OS.

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MeeGo was a Linux-based free mobile operating system project, which lives on in a fork called Mer.

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Jolla is a Finland-based company that develops and sells smartphones and the operating system Sailfish OS, which powers them.

Single Address Space Operating Systems (SASOSs) are OSs in which all code and data exists within one, big, shared address space, often threaded. Using one address space facilitates and enhances sharing and cooperation, because it lets addresses have a unique (for all time) representation or interpretation. Thus, pointer-based data structures can be directly communicated and shared between programs at any time, and can be stored directly on secondary storage with no need to translate. Such structures are simplified by using larger address spaces. All earlier OSs were SASOSs, because computers only used single address spaces; that was all that existed, there was nothing else. Segmented/paged address spaces were a later development. Most present, common personal computers use the x86 architecture, which began as the segmented 8088/8086; though i386 and later IA32 processors have a single address space (flat) memory mode. Future, larger processors may return more to single address spaces as the high-end of the computer industry moves to 64-bit CPUs. Or, OSs may keep using processes, which use a different address space for each process. Where SASOSs run as distributed OSs, SASOSs treat a network of nodes as one shared memory machine, using distributed virtual shared memory: DVSM. Some SASOS benefits:

1) Can be made as secure as traditional systems.

2) Are not inherently less efficient than traditional systems.

3) Improve performance over traditional systems on some types of important applications.

4) Give a dual cost advantage: lower initial cost, lower incremental cost.

This category is for submicrokernel operating systems: OSs with non-monolithic architectures based on structures smaller than microkernels. Varieties and synonyms: lightweight kernel, nanokernel, picokernel, femtokernel, exokernel, no-kernel, or closely related topics. Most, maybe all object-oriented OS architectures also qualify as submicrokernels. Traditional OS architectures limit application performance, flexibility, functionality by fixing interfaces and implementations of OS abstractions such as interprocess communication and virtual memory. Submicrokernels address these issues in varied ways. Most are runtime extensible. Exokernels address such issues by application-level management of physical resources: they put applications in control, to run 10x or more faster than normal OSs. On this page, OSs are arranged in three groups and levels: 1) Top group: types or classes of OS. 2) Middle group: OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.

The TI-99/4A Home Computer is a 'classic' computer system which was created and sold by Texas Instruments in the early 80's. Other systems generally considered to be in the TI-99 'family' include the TI-99/2, TI-99/4, TI-99/8, CC40, Geveve and the Tomy Tutor.

Tizen is a Linux-based operating system for multiple device categories.

The Tizen project resides within the Linux Foundation and is governed by a Technical Steering Group (TSG) composed of Samsung and Intel.

Tizen goes back to the Samsung Linux Platform (SLP) and the LiMo Project and Samsung also merged its homegrown Bada project into Tizen.

Intel put some of its MeeGo work into Tizen.

All operating systems (OSs) in this category support POSIX standards fully. The main standard defining what constitutes a Unix OS is POSIX, an acronym for: Portable Operating System Interface for UniX. Much like TRON, POSIX is not a body of computer code that is compiled and run on some processor. Rather, it is a set of standards (IEEE 1003.1): interfaces, design guidelines, software design specifications, defining (for creating) the computer code that will become language interfaces between an OS kernel and its programs, to give compatibility when moving programs between compatible systems. POSIX is made mostly of features from BSD Unix and Unix System V. Much like Open Source software, all POSIX standards are copyrighted (by the Institute of Electrical and Electronics Engineers, Inc., IEEE; new versions have joint copyright by IEEE and Open Group), but available for use by software developers anywhere in the world for free. Thus the OS architecture based on POSIX is an open architecture that invites and welcomes cloning and interoperability. Unix is a highly developed, mature, very stable, complex, and very powerful family of OSs for computers for running data processing and telephone systems. It provides multi-tasking, and multi-user abilities that let multiple programs run on one computer simultaneously, and let multiple users use one computer simultaneously; Unix systems can be servers, clients, and/or both, at once, all at the same time, as needed. On this page, links are arranged in three groups and levels: 1) Top group: issues spanning multiple unrelated Unix OSs. 2) Middle group: types or classes of OS, or OSs for which there are more than one instance of an OS of this name/type, an OS family. 3) Bottom group: specific Unix OSs.

This category holds links on operating systems (OSs) that run on computers, PCs and otherwise, using Intel and compatible x86-based architecture central processor units: CPUs. Main members of the Intel x86 family: 8086, 8088, 80186, 80286; and: IA32: 80386, 80486, 80586 (Pentium), 80686 (Pentium II), 80786 (Pentium III), 80886 (Pentium 4); and: IA64: 80986? (Itanium); and more to come. Some x86 compatibles: AMD (Advanced Micro Devices), Cyrix, Dragon, E2K (Elbrus), Transmeta, Winchip (Centaur, was IDT), etc. Links at the top of this page lead to other directory categories which hold OSs that run on x86s, and often on other architectures, but which have other, more distinctive traits that identify them as members of some class of OS found in the current directory taxonomy. OSs listed in this category are those that, for historic reasons, or the intent of program authors, run on x86s only, and have no other distinctive trait by which to classify them in the current directory taxonomy. These all seem to have monolithic kernels. An OS is listed in this category if there seems no clearer, more specific category for it. This category also has some other links that are hard to fit elsewhere, of which there are always a few.