In the past computing tasks such as word processing were not possible without the installation of application software on a user’s computer1). A user bought a license for each application from a software vendor and obtained the right to install the application on one computer system. With the development of LAN and more networking capabilities, the client-server model of computing was born, where server computers with enhanced capabilities and large storage devices could be used to host application services and data for a large workgroup. Typically, in client-server computing, a network-friendly client version of the application was required on client computers which utilized the client system’s memory and CPU for processing, even though resultant application data files (such as word processing documents) were stored centrally on the data servers. Multiple user licenses of an application were purchased for use by many users on a network.
Cloud computing differs from the classic client-server model by providing applications from a server that are executed and managed by a client’s web browser, with no installed client version of an application required. Centralization gives cloud service providers complete control over the versions of the browser-based applications provided to clients, which removes the need for version upgrades or license management on individual client computing devices. The term SaaS is sometimes used to describe application programs offered through cloud computing. A common shorthand for a provided cloud computing service (or even an aggregation of all existing cloud services) is The Cloud.
Any computer or web-friendly device connected to the Internet may access the same pool of computing power, applications, and files in a cloud-computing environment. Users may remotely store and access personal files such as music, pictures, videos, and bookmarks; play games; or do word processing on a remote server. Data is centrally stored, so the user does not need to carry a storage medium such as a DVD or thumb drive. Desktop applications that connect to internet-host email providers may be considered cloud applications, including web-based Gmail, Hotmail, or Yahoo! email services. Private companies may also make use of their own customized cloud email servers for their employees.
Cloud computing technologies are regarded by some analysts as a technological evolution, or may be seen as a marketing trap by others such as Richard Stallman.
Consumers now routinely use data-intensive applications driven by cloud technology that may have been previously unavailable due to cost and deployment complexity. In many companies, employees and company departments are bringing a flood of consumer technology into the workplace, which raises legal compliance and security concerns for the corporation which may be relieved by cloud computing.