DESKTOP
Desktop computers are
larger and not meant to be portable. They usually sit in one
place on
a desk or table and are plugged into a wall outlet for power.
The case
of the computer holds the motherboard,
drives,
power supply, and expansion cards.
This case may lay flat on the desk,
or it may be a tower that stands
vertically
(on the desk or under it). The computer usually has a separate
monitor
(either a CRT
or LCD)
although some designs have a display built into
the case. A separate keyboard and mouse allow the user to input
data
and commands.
Notebook or laptop
computers
are small and lightweight enough to be carried around with the
user.
They run on battery power, but can also be plugged into a wall
outlet.
They typically have a built-in LCD
display
that folds down to protect the display when the computer is
carried around.
They also feature a built-in keyboard and some kind of built-in pointing
device (such as a touch pad).
While some laptops are less powerful than typical
desktop machines, this is not true in all cases. Laptops,
however,
cost more than desktop units of equivalent processing power
because the
smaller components needed to build laptops are more expensive.
There are also less-powerful versions of notebook
computers
called subnotebooks, and netbooks that are used mainly to access
the Internet.
Tablet Computers and Smartphones
A Tablet Computer
(often just called a tablet) generally
has
the format of a handheld slate consisting of a large LCD
touchscreen
used for both input and output. Tablets typically include a WiFi
and/or
cellular network data connection to access the Internet. Tablets
run
applications specifically designed for these touchscreen
devices, but
they also can do some activities such as word processing or
spreadsheets,
although the lack of a physical keyboard usually makes such
activities
more cumbersome on tablets than they are on desktop or notebook
machines.
Examples of tablet computers include the Apple iPad and machines
from
various manufacturers that run the Android OS.
Smartphones are
high-end
mobile phones that typically run operating systems similar to
the tablet
computers discussed above, so they often share the same
applications
as tablets. They combine the features of a mobile phone, PDA
(see below),
camera, music player, GPS device,
etc. Many smartphones use a
touchscreen
for input, but some include physical keyboards.
PDAs and Palmtop Computers
A Personal Digital Assistant (PDA) is a handheld microcomputer that trades off power for small size and greater portability. They typically use a touch-sensitive LCD screen for both output and input (the user draws characters and presses icons on the screen with a stylus). PDAs communicate with desktop computers and with each other either by cable connection, infrared (IR) beam, or radio waves. PDAs are normally used to keep track of appointment calendars, to-do lists, address books, and for taking notes.
A palmtop or handheld
PC is a very small microcomputer that also
sacrifices power
for small size and portability. These devices typically look
more like
a tiny laptop than a PDA, with a flip-up screen and small
keyboard.
They may use Windows CE or similar operating system for
handheld devices.
Some PDAs and palmtops contain wireless networking
or cell
phone devices so that users can check e-mail or surf the web on
the move.
Workstations/Servers
A workstation is a powerful, high-end microcomputer. They contain one or more microprocessor CPUs. They may be used by a single-user for applications requiring more power than a typical PC (rendering complex graphics, or performing intensive scientific calculations).
Mainframes
A mainframe computer is a large, powerful computer that handles the processing for many users simultaneously (up to several hundred users). The name mainframe originated after minicomputers appeared in the 1960’s to distinguish the larger systems from the smaller minicomputers
Supercomputers | |||
A supercomputer is
mainframe computer that has been optimized for speed and
processing power.
The most famous series of supercomputers were designed by the
company
founded and named after Seymour Cray. The Cray-1
was
built in the 1976 and installed at Los Alamos National
Laboratory. Supercomputers
are used for extremely calculation-intensive tasks such
simulating nuclear
bomb detonations, aerodynamic flows, and global weather
patterns.
A supercomputer typically costs several million
dollars.
Recently, some supercomputers have been
constructed by
connecting together large numbers of individual processing units
(in
some cases, these processing units are standard microcomputer
hardware).
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