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In Computer science, cloud computing describes a type of outsourcing of computer services, similar to the way in which electricity supply is outsourced. Users can simply use it. They do not need to worry where the electricity is from, how it is made, or transported. Every month, they pay for what they consumed.

The idea behind cloud computing is similar: The user can simply use storage, computing power, or specially crafted development environments, without having to worry how these work internally. Cloud computing is usually Internet-based computing. The cloud is a metaphor for the Internet based on how the internet is described in computer network diagrams; which means it is an abstraction hiding the complex infrastructure of the internet.[1] It is a style of computing in which IT-related capabilities are provided as a service,[2] allowing users to access technology-enabled services from the Internet ("in the cloud")[3] without knowledge of, or control over the technologies behind these servers.[4]

According to a paper published by IEEE Internet Computing in 2008 "Cloud Computing is a paradigm in which information is permanently stored in servers on the Internet and cached temporarily on clients that include computers, laptops, handhelds, sensors, etc."[5]

Cloud computing is a general concept that utilizes software as a service (SaaS), such as Web 2.0 and other technology trends, all of which depend on the Internet for satisfying users' needs. For example, Google Apps provides common business applications online that are accessed from a web browser, while the software and data are stored on the Internet servers.

Cloud computing is often confused with grid computing (a form of distributed computing whereby a "super and virtual computer" is composed of a cluster of networked, loosely-coupled computers, working together to perform very large tasks), utility computing (the packaging of computing resources, such as computation and storage are provided as a measured service that have to be paid similar to a traditional public utility such as electricity)[6] and autonomic computing (computer systems capable of self-management).[7]

Many cloud computing deployments are powered by grids, have autonomic characteristics and are billed like utilities, but cloud computing can be seen as a natural next step from the grid-utility model.[8] Some successful cloud architectures have little or no centralised infrastructure or billing systems at all including peer-to-peer networks like BitTorrent and Skype.[9]

The majority of cloud computing infrastructure currently consists of reliable services delivered through data centers that are built on computer and storage virtualization technologies. The services are accessible anywhere in the world, with The Cloud appearing as a single point of access for all the computing needs of consumers. Commercial offerings need to meet the quality of service requirements of customers and typically offer service level agreements.[10]Open standards and open source software are also critical to the growth of cloud computing.[11]

As customers generally do not own the infrastructure or know all details about it, mainly they are accessing or renting, so they can consume resources as a service, and may be paying for what they do not need, instead of what they actually do need to use. Many cloud computing providers use the utility computing model which is analogous to how traditional public utilities like electricity are consumed, while others are billed on a subscription basis. By sharing consumable and "intangible" computing power between multiple "tenants", utilization rates can be improved (as servers are not left idle) which can reduce costs significantly while increasing the speed of application development.

A side effect of this approach is that "computer capacity rises dramatically" as customers do not have to engineer for peak loads.[12] Adoption has been enabled by "increased high-speed bandwidth" which makes it possible to receive the same response times from centralized infrastructure at other sites.

Cloud computing is being driven by providers including Google, Amazon.com, and Yahoo! as well as traditional vendors including IBM, Intel,[13]Microsoft[14] and SAP.[15] It can adopted by all kinds of users, be they individuals or large enterprises. Most internet users are currently using cloud services, even if they do not realize it. Webmail for example is a cloud service, as are Facebook and Wikipedia and contact list synchronization and online data backups.

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Cloud computing - Simple English Wikipedia, the free ...