Thin Client Definition

A thin client is a low-cost computing device in a client-server environment whose main or sole function is to process keyboard input and screen output and which accesses most or all application programs and data from a central server via a network.

The client-server architecture (i.e., network design) divides work between two separate, but linked, programs, referred to as clients and servers. A client is a computer, program or process that makes requests for information from another computer, program or process in a client-server relationship. Servers, which typically (but not necessarily) run on remote machines (i.e., computers located elsewhere on the network), handle requests from multiple clients, process the data as requested and return the results to the clients' computer screens.

Thin clients can be created in a combination of hardware and software. Or they can be created in software only and operate on a standard personal computer. Today most thin clients are the latter.

Thin client hardware normally require only a keyboard, a monitor and a network connection to access programs and resources. Dedicated thin clients usually do not have hard disk drives (HDDs), CDROM drives, floppy disk drives and expansion slots. This results in both lower cost and increased security.

The terms thick client and fat client are sometimes used to refer to networked computers on which a relatively larger amount of processing is performed. Such clients perform as much processing as possible locally and rely on servers mainly for data that is required for archival storage and communications.

Thin clients traditionally had a command line (i.e., text-only) user interface, and thus they were often referred to as text terminals. More recent thin clients have a GUI (graphical user interface), and many of them now use a web browser on top of the GUI to access the applications.

A number of advantages are claimed for using thin clients instead of ordinary personal computers in a networked situation in an organization. They include (1) greater ease of management of application software, (2) reduced hardware costs (because simpler and older computers can be used for clients), (3) lower maintenance costs (due to the simpler hardware, such as the lack of disk drives), (4) greater flexibility and (5) enhanced security and stability.

There are several reasons that the use of thin clients for networks can result in increased security and stability, including (1) fewer points of equipment failure (because the hardware can be simpler), (2) greater difficulty for viruses and other malware to enter the system (i.e., centralized malware protection because application programs and data do not reside on the clients) and (3) reduced incentive for theft (because thieves are usually interested in more advanced hardware).

There are also several disadvantages of using thin clients, including (1) the need for more costly servers (because little or no processing is done on the clients), (2) inferior multimedia performance for any given amount of bandwidth and (3) poor suitability for some programs which have been designed for use on personal computers which have their own processing and storage capabilities.

An X terminal is a thin client that is designed to run an X server. An X server is a program in the X Window System that runs on the local machines (i.e., the computers operated directly by users) and handles all access to the graphics cards, display screens and input devices (typically a keyboard and mouse) on those computers. The X Window System, often referred to merely as X, is a complete, cross-platform and free client-server system for managing GUIs on single computers and on networks of computers. Dedicated X terminals are no longer common because the same (and usually better) functionality can be provided at a lower cost by personal computers due to the large drop in their prices in recent years.

Created February 11, 2006.
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