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Types of computers and servers
Personal computer
A small, relatively inexpensive computer designed for an individual user.
Today, the world of personal computers is basically divided between Apple Macintoshes
and PCs. The principal characteristics of personal computers are that they are
single-user systems and are based on microprocessors.
An extremely lightweight personal computer. Notebook computers typically weigh
less than 6 pounds and are small enough to fit easily in a briefcase. Notebook
computers use a variety of techniques, known as flat-panel technologies.
Notebook computers come with battery packs that enable you to run them without
plugging them in. However, the batteries need to be recharged every few hours.
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Handheld computer
PDA
Short for personal digital assistant, also called as palmtops, hand-held computers
and pocket computers.it is a handheld device that combines computing, telephone/fax,
Internet and networking features. Unlike portable computers, most PDAs began
as pen-based, using a stylus rather than a keyboard for input. Some PDAs can
also react to voice input by using voice recognition technologies. PDAs of today
are available in either a stylus or keyboard version.
Tablet PC
Tablet PC, a type of notebook computer that has an LCD screen on which the user
can write using a special-purpose pen, or stylus. Tablet PCs also typically
have a keyboard and/or a mouse for input.
The tablet PC relies on digital ink technology, where a digitizer is laid under
or over an LCD screen to create an electromagnetic field that can capture the
movement of the special-purpose pen and record the movement on the LCD screen.
The effect is like writing on paper with liquid ink.
Midrange computer (minicomputer)
A midsized computer. In size and power, minicomputers lie between workstations
and mainframes. A minicomputer is a multiprocessing system capable of supporting
from 4 to about 200 users simultaneously.
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Mainframe computer
A very large and expensive computer capable of supporting hundreds, or even
thousands, of users simultaneously. In some ways, mainframes are more powerful
than supercomputers because they support more simultaneous programs.
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Supercomputer
The
fastest type of computer. Supercomputers are very expensive and are employed
for specialized applications that require immense amounts of mathematical calculations.
For example, weather forecasting requires a supercomputer. Other uses of supercomputers
include animated graphics, fluid dynamic calculations and nuclear energy research.
The chief difference between a supercomputer and a mainframe is that a supercomputer
channels all its power into executing a few programs as fast as possible, whereas
a mainframe uses its power to execute many programs concurrently.
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Application Servers
Sometimes referred to as a type of middleware, application servers occupy a
large chunk of computing territory between database servers and the end user,
and they often connect the two.
Audio/Video Servers
Audio/Video servers bring multimedia capabilities to Web sites by enabling them
to broadcast streaming multimedia content.
FTP Servers
One of the oldest of the Internet services, File Transfer Protocol makes it
possible to move one or more files securely between computers while providing
file security and organization as well as transfer control.
Mail Servers
Almost as ubiquitous and crucial as Web servers, mail servers move and store
mail over corporate networks (via LANs and WANs) and across the Internet.
News Servers
News servers act as a distribution and delivery source for the thousands of
public news groups currently accessible over the USENET news network.
Proxy Servers
Proxy servers sit between a client program (typically a Web browser) and an
external server (typically another server on the Web) to filter requests, improve
performance, and share connections.
Web Servers
At its core, a Web server serves static content to a Web browser by loading
a file from a disk and serving it across the network to a user's Web browser.
This entire exchange is mediated by the browser and server talking to each other
using HTTP.