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== Description ==
A Distributed operating system is an [[operating system]]. While thisThis statement ismay somewhatbe trivial, but it is not always overtlyovert and obvious; because athe distributed operating system is simultaneouslysuch aan integral part of the [[distributed system]]. This idea is synonymous to the square.consideration Beingof a [[Square (geometry)#Properties|square,]]. itA square might not immediately be recognized also as a rectangle. Although possessing all requisite [[Attribute (computing)|attributes]] defining a rectangle, buta nonethelesssquare’s isadditional attributes and specific configuration provide a disguise. At Theits core, the distributed operating system performsprovides allonly requisitethe activitiesessential services and suppliesminimal allfunctionality necessaryrequired functionalityof inan operating system, but its additional attributes and particular [[Computer configuration|configuration]] make it different. The Distributed operating system fulfills its capacityrole as operating system; butand does so in a manner indistinguishable from a centralized, [[Monolithic kernel|monolithic operating system]]. That is, atalthough distributed in nature, it supports the samesystem’s timeappearance more.as a singular, local entity.
An operating system, at its most basic level, is expected to isolate and manage the lower-level physical complexities of the [[hardware]] and associated resources. In turn, these low-level physical elements are organized into simplified logical [[abstractions]]. These abstractions are finally presented as higher-level [[Interface (computer science)|interfaces]] into the underlying hardware and [[Resource (computer science)|resources]]. The Distributed operating system not only fulfills its role in this capacity; but is capable of doing so in a manner indistinguishable from its more centralized counterparts. That is, although distributed in nature, it appears to the user as a singular and local entity; only exposing its unique distributed attributes if convenient or necessary for a specific purpose. Again, a square is a rectangle, the same in principle, different in configuration.
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An operating system, at a basic level, is expected to isolate and manage the physical complexities of lower-level [[hardware]] resources. In turn, these complexities are organized into simplified logical [[abstractions]] and presented to higher-level entities as [[Interface (computer science)|interfaces]] into the underlying [[Resource (computer science)|resources]]. These marshalling and presentation activities take place in a secure and protected environment, often referred to as the “[[Supervisor mode#Supervisor mode|system-level]],” and describe a minimal scope of practical operating system functionality. In graphical depictions however, most monolithic operating systems would be illustrated as a discrete container sandwiched between the local hardware resources below and application programs above. The operating system container would be filled with a robust compliment of services and functions to support as many potential needs as possible or practical. This full-featured collection of services would reside and execute at the system-level and support higher, “[[User space|user-level]]” applications and services.
In most graphic depictions, an operating system is illustrated as a discrete organizational container sandwiched between hardware and its resources below, and applications, programmers, and other "needy" entities above. A Distributed operating system, illustrated in a similar fashion, would completely contain the set of discrete and disseminated hardware elements within its container. It is the hardware that displays differing degrees of spatial separation, however it is the containment of these hardware elements that allow for a consistent, unified, singular, and local appearance.
A distributed operating system, illustrated in a similar fashion, would be a container suggesting [[Microkernel#Essential components and minimality|minimal operating system functionality and scope]]. This container would completely cover all disseminated hardware resources, defining the system-level. The container would extend across the system, supporting a layer of modular software components existing in the user-level. These software components supplement the distributed system with a configurable set of added services, usually integrated within the monolithic operating system (and the system-level). This division of minimal system-level function from additional user-level modular services provides a “[[separation of mechanism and policy]].” Mechanism and policy can be simply interpreted as "how something is done" versus "why something is done," respectively. Achieving this separation allows for an exceptionally loosely coupled, flexible, and scalable distributed system.
This is an exceptionally important and subtle distinction. It will serve to differentiate the Distributed operating system from other decentralized operating systems. And more importantly, it provides a foundation for many additional and beneficial services, which will be described in detail below. Simply said, it is solely the dissemination of hardware elements that "allows" for additional benefits and services. It is the extremely complex, sophisticated, and orchestrated utilization of this separation that instantiates the benefits.
== Overview ==
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