Lab-2 Hardware description

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					                                               Computer Hardware

A programmable machine. The two principal characteristics of a computer are:
          It responds to a specific set of instructions in a well-defined manner.

         It can execute a prerecorded list of instructions (a program).

Modern computers are electronic and digital. The actual machinery -- wires, transistors, and circuits -- is called hardware; the
instructions and data are called software.

All general-purpose computers require the following hardware components:

           memory : Enables a computer to store, at least temporarily, data and programs.
           mass storage device : Allows a computer to permanently retain large amounts of data. Common mass storage
          devices include disk drives and tape drives.
           input device : Usually a keyboard and mouse, the input device is the conduit through which data and instructions
          enter a computer.
           output device : A display screen, printer, or other device that lets you see what the computer has accomplished.
           central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions.

In addition to these components, many others make it possible for the basic components to work together efficiently. For
example, every computer requires a bus that transmits data from one part of the computer to another.

Computers can be generally classified by size and power as follows, though there is considerable overlap:

           personal computer : A small, single-user computer based on a microprocessor. In addition to the microprocessor, a
          personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for
          saving data.
           workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more
          powerful microprocessor and a higher-quality monitor.
           minicomputer : A multi-user computer capable of supporting from 10 to hundreds of users simultaneously.
           mainframe : A powerful multi-user computer capable of supporting many hundreds or thousands of users
           supercomputer : An extremely fast computer that can perform hundreds of millions of instructions per second.

Pronounced ramm, acronym for random access memory, a type of computer memory that can be accessed randomly; that is, any
byte of memory can be accessed without touching the preceding bytes. RAM is the most common type of memory found in
computers and other devices, such as printers.

Short for Universal Serial Bus, an external bus standard that supports data transfer rates of 12 Mbps. A single USB port can be
used to connect up to 127 peripheral devices, such as mice, modems, and keyboards. USB also supports Plug-and-Play
installation and hot plugging.
Also called a power supply unit or PSU, the component that supplies power to a computer. Most personal computers can be
plugged into standard electrical outlets. The power supply then pulls the required amount of electricity and converts the AC
current to DC current. It also regulates the voltage to eliminate spikes and surges common in most electrical systems. Not all
power supplies, however, do an adequate voltage-regulation job, so a computer is always susceptible to large voltage

A device that prints text or illustrations on paper. There are many different types of printers. In terms of the technology utilized,
printers fall into the following categories:
   daisy-wheel: Similar to a ball-head typewriter, this type of printer has a plastic or metal wheel on which the shape of each
character stands out in relief. A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the
character on the paper.Daisy-wheel printers produce letter-quality print but cannot print graphics.
   dot-matrix: Creates characters by striking pins against an ink ribbon. Each pin makes a dot, and combinations of dots form
characters and illustrations.
   ink-jet: Sprays ink at a sheet of paper. Ink-jet printers produce high-quality text and graphics.
   laser: Uses the same technology as copy machines. Laser printers produce very high quality text and graphics.
   LCD & LED : Similar to a laser printer, but uses liquid crystals or light-emitting diodes rather than a laser to produce an
image on the drum.
   line printer: Contains a chain of characters or pins that print an entire line at one time. Line printers are very fast, but produce
low-quality print.
   thermal printer: An inexpensive printer that works by pushing heated pins against heat-sensitive paper. Thermal printers are
widely used in calculators and fax machines.

A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a
hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to
be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display
screen moves in the same direction. Mice contain at least one button and sometimes as many as three, which have different
functions depending on what program is running. Some newer mice also include a scroll wheel for scrolling through long

A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a
hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to
be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display
screen moves in the same direction. Mice contain at least one button and sometimes as many as three, which have different
functions depending on what program is running. Some newer mice also include a scroll wheel for scrolling through long

Abbreviation of video graphics array, a graphics display system for PCs developed by IBM. VGA has become one of the de facto
standards for PCs. In text mode, VGA systems provide a resolution of 720 by 400 pixels. In graphics mode, the resolution is
either 640 by 480 (with 16 colors) or 320 by 200 (with 256 colors). The total palette of colors is 262,144.

Often abbreviated SATA or S-ATA, an evolution of the Parallel ATA physical storage interface. Serial ATA is a serial link -- a
single cable with a minimum of four wires creates a point-to-point connection between devices. Transfer rates for Serial ATA
begin at 150MBps. One of the main design advantages of Serial ATA is that the thinner serial cables facilitate more efficient
airflow inside a form factor and also allow for smaller chassis designs. In contrast, IDE cables used in parallel ATA systems are
bulkier than Serial ATA cables and can only extend to 40cm long, while Serial ATA cables can extend up to one meter.
Serial ATA supports all ATA and ATAPI devices.

(sku´zē) Short for small computer system interface, a parallel interface standard used by Apple Macintosh computers, PCs, and
many UNIX systems for attaching peripheral devices to computers. Nearly all Apple Macintosh computers, excluding only the
earliest Macs and the recent iMac, come with a SCSI port for attaching devices such as disk drives and printers.

(1) An interface on a computer to which you can connect a device. Personal computers have various types of ports. Internally,
there are several ports for connecting disk drives, display screens, and keyboards. Externally, personal computers have ports for
connecting modems, printers, mice, and other peripheral devices.

(mō´dem) (n.) Short for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over,
for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone
lines is transmitted in the form of analog waves. A modem converts between these two forms.

A camera that stores images digitally rather than recording them on film. Once a picture has been taken, it can be downloaded to
a computer system, and then manipulated with a graphics program and printed. Unlike film photographs, which have an almost
infinite resolution, digital photos are limited by the amount of memory in the camera, the optical resolution of the digitizing
mechanism, and, finally, by the resolution of the final output device. Even the best digital cameras connected to the best printers
cannot produce film-quality photos. However, if the final output device is a laser printer, it doesn't really matter whether you take
a real photo and then scan it, or take a digital photo. In both cases, the image must eventually be reduced to the resolution of the

The name of a popular wireless networking technology that uses radio waves to provide wireless high-speed Internet and network
connections. The Wi-Fi Alliance, the organization that owns the Wi-Fi (registered trademark) term specifically defines Wi-Fi as
any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE)
802.11 standards."

Often abbreviated as NIC, an expansion board you insert into a computer so the computer can be connected to a network. Most
NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks.

The main circuit board of a microcomputer. The motherboard contains the connectors for attaching additional boards. Typically,
the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the
controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive. Collectively, all
these chips that reside on the motherboard are known as the motherboard's chipset.

An electronic flash memory storage disk commonly used in consumer electronic devices such as digital cameras, MP3 players,
mobile phones, and other small portable devices. Types of memory cards include PCMCIA, CompactFlash, SD Card, MiniSD,
xD-Picture Card and others. Memory cards are usually read by connecting the device containing the card to your computer, or by
using a USB card reader.
Short for liquid crystal display, a type of display used in digital watches and many portable computers. LCD displays utilize two
sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the
crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass
through or blocking the light.

A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used
interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also
control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.

An electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance. Synonymous
with loudspeaker.

A component designed to lower the temperature of an electronic device by dissipating heat into the surrounding air. All modern
CPUs require a heat sink. Some also require a fan. A heat sink without a fan is called a passive heat sink; a heat sink with a fan is
called an active heat sink. Heat sinks are generally made of an aluminum alloy and often have fins.

A soft magnetic disk. It is called floppy because it flops if you wave it (at least, the 5¼-inch variety does). Unlike most hard
disks, floppy disks (often called floppies or diskettes) are portable, because you can remove them from a disk drive. Disk drives
for floppy disks are called floppy drives. Floppy disks are slower to access than hard disks and have less storage capacity, but
they are much less expensive. And most importantly, they are portable.

A type of display screen that has a touch-sensitive transparent panel covering the screen. Instead of using a pointing device such
as a mouse or light pen, you can use your finger to point directly to objects on the screen.
Although touch screens provide a natural interface for computer novices, they are unsatisfactory for most applications because
the finger is such a relatively large object. It is impossible to point accurately to small areas of the screen. In addition, most users
find touch screens tiring to the arms after long use.

A pointing device. Essentially, a trackball is a mouse lying on its back. To move the pointer, you rotate the ball with your thumb,
your fingers, or the palm of your hand. There are usually one to three buttons next to the ball, which you use just like mouse
The advantage of trackballs over mice is that the trackball is stationary so it does not require much space to use it. In addition,
you can place a trackball on any type of surface, including your lap. For both these reasons, trackballs are popular pointing
devices for portable computers.

A lever that moves in all directions and controls the movement of a pointer or some other display symbol. A joystick is similar to
a mouse, except that with a mouse the cursor stops moving as soon as you stop moving the mouse. With a joystick, the pointer
continues moving in the direction the joystick is pointing. To stop the pointer, you must return the joystick to its upright position.
Most joysticks include two buttons called triggers.
Joysticks are used mostly for computer games, but they are also used occasionally for CAD/CAM systems and other applications.
(row´ter) (n.) A device that forwards data packets along networks. A router is connected to at least two networks, commonly two
LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks

(swich) (n.) (1) In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link
layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol.
LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.

A device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines
using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced
series of dots. Multicolor plotters use different-colored pens to draw different colors.
In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is

A device that can read text or illustrations printed on paper and translate the information into a form the computer can use. A
scanner works by digitizing an image -- dividing it into a grid of boxes and representing each box with either a zero or a one,
depending on whether the box is filled in. (For color and gray scaling, the same principle applies, but each box is then
represented by up to 24 bits.) The resulting matrix of bits, called a bit map, can then be stored in a file, displayed on a screen, and
manipulated by programs.

Pronounced middy, an acronym for musical instrument digital interface, a standard adopted by the electronic music industry for
controlling devices, such as synthesizers and sound cards, that emit music. At minimum, a MIDI representation of a sound
includes values for the note's pitch, length, and volume. It can also include additional characteristics, such as attack and delay

An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-
ROMs and have become commonplace on modern personal computers. Sound cards enable the computer to output sound through
speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound
stored on a disk.

A board that plugs into a personal computer to give it display capabilities. The display capabilities of a computer, however,
depend on both the logical circuitry (provided in the video adapter) and the display monitor. A monochrome monitor, for
example, cannot display colors no matter how powerful the video adapter.

An input device that utilizes a light-sensitive detector to select objects on a display screen. A light pen is similar to a mouse,
except that with a light pen you can move the pointer and select objects on the display screen by directly pointing to the objects
with the pen.

An input device that enables you to enter drawings and sketches into a computer. A digitizing tablet consists of an electronic
tablet and a cursor or pen. A cursor (also called a puck) is similar to a mouse, except that it has a window with cross hairs for
pinpoint placement, and it can have as many as 16 buttons. A pen (also called a stylus) looks like a simple ballpoint pen but uses
an electronic head instead of ink. The tablet contains electronics that enable it to detect movement of the cursor or pen and
translate the movements into digital signals that it sends to the computer.

Short for CD-ReWritable disk, a type of CD disk that enables you to write onto it in multiple sessions. One of the problems with
CD-R disks is that you can only write to them once. With CD-RW drives and disks, you can treat the optical disk just like a
floppy or hard disk, writing data onto it multiple times.

Short for digital versatile disc or digital video disc, a type of optical disk technology similar to the CD-ROM. A DVD holds a
minimum of 4.7GB of data, enough for a full-length movie. DVDs are commonly used as a medium for digital representation of
movies and other multimedia presentations that combine sound with graphics.

Pronounced rahm, acronym for read-only memory, computer memory on which data has been prerecorded. Once data has been
written onto a ROM chip, it cannot be removed and can only be read.
Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being
nonvolatile, whereas RAM is volatile.

Pronounced cash, a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent
high-speed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching.

A highly integrated chip that contains all the components comprising a controller. Typically this includes a CPU, RAM, some
form of ROM, I/O ports, and timers. Unlike a general-purpose computer, which also includes all of these components, a
microcontroller is designed for a very specific task -- to control a particular system. As a result, the parts can be simplified and
reduced, which cuts down on production costs.
A device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in 1947 at Bell Labs,
transistors have become the key ingredient of all digital circuits, including computers. Today's microprocessors contains tens of
millions of microscopic transistors.

Another name for a chip, an integrated circuit (IC) is a small electronic device made out of a semiconductor material. The first
integrated circuit was developed in the 1950s by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor.
Integrated circuits are used for a variety of devices, including microprocessors, audio and video equipment, and automobiles.
Integrated circuits are often classified by the number of transistors and other electronic components they contain:
              -scale integration): Up to 100 electronic components per chip
                  -scale integration): From 100 to 3,000 electronic components per chip
   LSI (large-scale integration): From 3,000 to 100,000 electronic components per chip
   VLSI (very large-scale integration): From 100,000 to 1,000,000 electronic components per chip
   ULSI (ultra large-scale integration): More than 1 million electronic components per chip

(1) A collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a
highway on which data travels within a computer. When used in reference to personal       computers, the term bus usually refers
to internal bus. This is a bus that connects all the internal computer components to the CPU and main memory. There's also
an expansion bus that enables expansion boards to access the CPU and memory.
A magnetic disk on which you can store computer data. The term hard is used to distinguish it from a soft, or floppy, disk.
Hard disks hold more data and are faster than floppy disks. A hard disk, for example, can store anywhere from 10 to more than
100 gigabytes, whereas most floppies have a maximum storage capacity of 1.4 megabytes.

Short for Peripheral Component Interconnect, a local bus standard developed by Intel        Corporation. Most modern PCs
include a PCI bus in addition to a more general ISA expansion bus. PCI is also used on some versions of the Macintosh
computer. PCI is a 64-bit bus, though it is usually implemented as a 32-bit bus. It can run at clock speeds of 33 or 66 MHz. At
32 bits and 33 MHz, it yields a throughput rate of 133 MBps. Although it was developed by Intel, PCI is not tied to any
particular family of microprocessors. Also see PCI-X and PCI Express.

(sku´zē) Short for small computer system interface, a parallel
                                                             interface standard used by Apple Macintosh computers,
PCs, and many UNIX systems for attaching peripheral devices to computers. Nearly all Apple Macintosh computers,
excluding only the earliest Macs and the recent iMac, come with a SCSI port for attaching devices such as disk drives and

A high-capacity floppy disk drive developed by Iomega Corporation. Zip disks are slightly larger than conventional floppy disks,
and about twice as thick. They can hold 100 or 250 MB of data. Because they're relatively inexpensive and durable, they have
become a popular media for backing up hard disks and for transporting large files.

A machine that reads data from and writes data onto a disk. A disk drive rotates the disk very fast and has one or more heads that
read and write data.
There are different types of disk drives for different types of disks. For example, a hard disk drive (HDD) reads and writes hard
disks, and a floppy drive (FDD) accesses floppy disks. A magnetic disk drive reads magnetic disks, and an optical drive reads
optical disks.
Disk drives can be either internal (housed within the computer) or external (housed in a separate box that connects to the

The display part of a monitor. Most display screens work under the same principle as a television, using a cathode ray tube
(CRT). Consequently, the term CRT is often used in place of display screen.


(bī´ōs) Acronym for basic input/output system, the built-in software that determines what a computer can do without accessing
programs from a disk. On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial
communications, and a number of miscellaneous functions.


A port, or interface, that can be used for serial communication, in which only 1 bit is transmitted at a time.
Most serial ports on personal computers conform to the RS-232C or RS-422 standards. A serial port is a general-purpose
interface that can be used for almost any type of device, including modems, mice, and printers (although most printers are
connected to a parallel port).


A parallel interface for connecting an external device such as a printer. Most personal computers have both a parallel port and at
least one serial port.

On PCs, the parallel port uses a 25-pin connector (type DB-25) and is used to connect printers, computers and other devices that
need relatively high bandwidth. It is often called a Centronics interface after the company that designed the original standard for
parallel communication between a computer and printer. (The modern parallel interface is based on a design by Epson.)

A newer type of parallel port, which supports the same connectors as the Centronics interface, is the EPP (Enhanced Parallel
Port) or ECP (Extended Capabilities Port). Both of these parallel ports support bi-directional communication and transfer rates
ten times as fast as the Centronics port.

Macintoshes have a SCSI port, which is parallel, but more flexible.


A type of port developed by IBM for connecting a mouse or keyboard to a PC. The PS/2 port supports a mini DIN plug
containing just 6 pins. Most PCs have a PS/2 port so that the serial port can be used by another device, such as a modem. The
PS/2 port is often called the mouse port.


A short-range radio technology aimed at simplifying communications among Internet devices and between devices and the
Internet. It also aims to simplify data synchronization between Internet devices and other computers.

Products with Bluetooth technology must be qualified and pass interoperability testing by the Bluetooth Special Interest Group
prior to release. Bluetooth's founding members include Ericsson, IBM, Intel, Nokia and Toshiba.

Also see the Wireless LAN Standards chart in the Quick Reference section of Webopedia.


Abbreviation of either Intelligent Drive Electronics or Integrated Drive Electronics, depending on who you ask. An IDE interface
is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive.

Although it really refers to a general technology, most people use the term to refer the ATA specification, which uses this
technology. Refer to ATA for more information.


Abbreviation of either Intelligent Drive Electronics or Integrated Drive Electronics, depending on who you ask. An IDE interface
is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive.

Although it really refers to a general technology, most people use the term to refer the ATA specification, which uses this
technology. Refer to ATA for more information.

Abbreviated as IR, infrared is a wave of light that in the area beyond the visible part of the color spectrum. While it is invisible to
human eye infrared is often used to enhance visibility when using night vision devices.


A type of flat-panel display that works by sandwiching a neon/xenon gas mixture between two sealed glass plates with parallel
electrodes deposited on their surfaces. The plates are sealed so that the electrodes form right angles, creating pixels. When a
voltage pulse passes between two electrodes, the gas breaks down and produces weakly ionized plasma, which emits UV
radiation. The UV radiation activates color phosphors and visible light is emitted from each pixel.

Today, Plasma displays are becoming more and more popular. Compared to conventional CRT displays, plasma displays are
about one-tenth the thickness--around 4'', and one-sixth the weight--under 67 pounds for a 40" display. They use over 16 million
colors and have a 160 degree-viewing angle.

Plasma displays are manufactured by companies such as Panasonic, Fujitsu, and Pioneer.


(Pronounced as separate letters or as eye-sa). Short for Industry Standard Architecture bus, the bus architecture used in the IBM
PC/XT and PC/AT. The AT version of the bus is called the AT bus and became a de facto industry standard. Starting in the early
90s, ISA began to be replaced by the PCI local bus architecture. Most computers made today include both an AT bus for slower
devices and a PCI bus for devices that need better bus performance.


A rechargeable battery used in portable computer devices, such as notebook computers. The most common substances used in
computer battery packs are nickel cadmium (Nicad), nickel metal hydride (NiMH), and Lithium Ion.

A new type of battery, called a smart battery, provides the computer with information about its power status so that the computer
can conserve power intelligently. With a normal battery, the computer makes estimates about the battery's condition that are not
always correct.


A metal bridge that closes an electrical circuit. Typically, a jumper consists of a plastic plug that fits over a pair of protruding
pins. Jumpers are sometimes used to configure expansion boards. By placing a jumper plug over a different set of pins, you can
change a board's parameters.


Abbreviation of interrupt request line, and pronounced I-R-Q. IRQs are hardware lines over which devices can send interrupt
signals to the microprocessor. When you add a new device to a PC, you sometimes need to set its IRQ number by setting a DIP
switch. This specifies which interrupt line the device may use. IRQ conflicts used to be a common problem when adding
expansion boards, but the Plug-and-Play specification has removed this headache in most cases.

A storage medium from which data is read and to which it is written by lasers. Optical disks can store much more data -- up to 6
gigabytes (6 billion bytes) -- than most portable magnetic media, such as floppies. There are three basic types of optical disks:

   CD-ROM : Like audio CDs, CD-ROMs come with data already encoded onto them. The data is permanent and can be read
any number of times, but CD-ROMs cannot be modified.

   WORM : Stands for write-once, read -many. With a WORM disk drive, you can write data onto a WORM disk, but only once.
After that, the WORM disk behaves just like a CD-ROM.

                                                                                                                                 as EO
(erasable optical) disks.

These three technologies are not compatible with one another; each requires a different type of disk drive and disk. Even within
one category, there are many competing formats, although CD-ROMs are relatively standardized.


A special type of ink used by copy machines and laser printers. Toner consists of a dry, powdery substance that is electrically
charged so that it adheres to a drum, plate, or piece of paper charged with the opposite polarity.

For most laser printers, the toner comes in a cartridge that you insert into the printer. When the cartridge is empty, you can
replace it or have it refilled. Typically, you can print thousands of pages with a single cartridge.

(1) A removable storage medium (tape, disk, or memory chip). Some printers have slots in which you can insert cartridges to load
different fonts. A font loaded from a cartridge is called a font cartridge or cartridge font.

The term removable cartridge usually refers to a type of hard disk that you can remove. Removable cartridges offer the speed of
hard disks along with the portability of floppy disks.

(2) For laser and ink-jet printers, a toner cartridge is a metal container that holds the toner.

A device, like a tape recorder, that reads data from and writes it onto a tape. Tape drives have data capacities of anywhere from a
few hundred kilobytes to several gigabytes. Their transfer speeds also vary considerably. Fast tape drives can transfer as much as
20MB (megabytes) per second.

The disadvantage of tape drives is that they are sequential-access devices, which means that to read any particular block of data,
you need to read all the preceding blocks. This makes them much too slow for general-purpose storage operations. However, they
are the least expensive media for making backups.

(1) Spelled 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. The handwriting is digitized and can be converted to standard text through handwriting recognition, or it can
remain as handwritten text. The stylus also can be used to type on a pen-based key layout where the lettered keys are arranged
differently than a QWERTY keyboard. Tablet PCs also typically have a keyboard and/or a mouse for input.

In storage networking terminology, a Storage Area Network (SAN) is a high-speed subnetwork of shared storage devices. A
storage device is a machine that contains nothing but a disk or disks for storing data.

A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains
multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all

A passive hub serves simply as a conduit for the data, enabling it to go from one device (or segment) to another. So-called
intelligent hubs include additional features that enables an administrator to monitor the traffic passing through the hub and to
configure each port in the hub. Intelligent hubs are also called manageable hubs.

Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an
organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC
Cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times
and is now suitable for many types of devices. There are in fact three types of PCMCIA cards. All three have the same
rectangular size (85.6 by 54 millimeters), but different widths
                                                                                                 ROM or RAM to a computer.

         Type II cards can be up to 5.5 mm thick. These cards are often used for modem and fax modem cards.

                                                                                                 disk drives.


Short for personal digital assistant, a handheld device that combines computing, telephone/fax, Internet and networking
features. A typical PDA can function as a cellular phone, fax sender, Web browser and personal organizer. Unlike portable
computers, most PDAs began as pen-based, using a stylus rather than a keyboard for input. This means that they also
incorporated handwriting recognition features. 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.


Apple's iPod is a small portable music player. Users can transfer songs to their iPod with their computer, iTunes, and the iPod
software. Since the release of the Apple iPod in 2001, under the iPod brand Apple has released many variations of its product
such as the iPod classic, iPod Touch, iPod Shuffle, iPod Mini, iPod Nano and several spin-off devices such as the iPod Photo.

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