Ins _ Outs of computers - World of Teaching by fanzhongqing


									Input devices are used to get data into a system. The ideal input
devices would be able to get data into a system as accurately as
possible, in the least amount of time ands preferably without
human intervention. The device would also be relatively cheap.
Unfortunately, no perfect input device is available and the choice
is always a compromise. The fastest input devices are suitable
only for a narrow range of applications. Here are some of the main
input devices in use today.
The keyboard is the oldest and most familiar of all input devices. Keyboards are
intelligent devices and contain their own chips. Basically each key acts as a switch
which closes when the key is pressed. The microprocessor scans the keyboard
hundreds of times a second to see if a key has been pressed; if it has, a code that
depends on which key has been pressed is sent to the processing unit. The CPU
translates this code into an ASCII code (the code that computers use to represent
characters on the computer keyboard), which is then used by the computer program. A
standard keyboard is called a QWERTY keyboard because of the arrangement of the
letters of the top row of the alphabet key.
Enhanced / Extended Keyboard

                                   Ergonomic Keyboard

     Enhanced or Extended keyboard – Typically 101 keys
   laid out in the QWERTY fashion; connected to the
   computer by a cable
     Cordless keyboard – Uses infrared or radio wave
     Ergonomic keyboard – Designed to help prevent
   cumulative trauma disorder (CTD) or damage to nerve
   tissues in the wrist and hand due to repeated motion
A mouse is an input device that translates its movements on the
desktop into digital information; this is feed to the computer which
in turn causes the cursor to move on the screen. Underneath the
mouse is a ball which rotates as the mouse is moved on the desk,
and sensors pick up this movement. Mice usually have one, two
or three buttons, used which are to make selection on the screen

                          To see types of mouse's
                          click here
                         Types of Mice

Wheel                                                   Cordless
Mouse                                                   Mouse

          Wheel mouse – Contains a rotating
        wheel used to scroll vertically within a text
        document; connects to PS/2 port or USB
          Cordless mouse – Uses infrared signals
        to connect to the computer’s IrDA port; it
        must be within sight of the receiving port
Mouse buttons enable the user to initiate actions.
    Clicking (left-, right-, or double-clicking) allows the user
       to select an item on the screen or open a program or dialog box
     Click and drag – Holding down the left mouse button and moving
       the mouse enables the user to move objects on the screen
3. 2 button mouse
4. scrolling 2 button mouse
5. 3 button mouse
6. numeric keypad and mouse
       Is a control stick or joystick A    •
    or computer peripheral personal
 general control device consisting of
   a handheld stick that pivots about
   one end and transmits its angle in
         two or three dimensions to a
  Joysticks are often used to control      •
and usually have one ,video games
  whose state buttons-or more push
  can also be read by the computer.
     The term joystick has become a
   synonym for game controllers that
  can be connected to the computer
since the computer defines the input
                  ."as a "joystick input
       Apart from controlling games,       •
           joysticks are also used for
        controlling machines such as
     powered ,trucks ,cranes ,aircraft
 and some zero turning wheelchairs
 More recently .lawn mowers radius
       miniature joysticks have been
 adopted as navigational devices for
  smaller electronic equipment such            Joystick elements: 1. Stick 2. Base 3.
                    .as mobile phones          Trigger 4. Extra buttons 5. Autofire switch 6.
                                               Throttle 7. Hat Switch (POV Hat) 8. Suction
     A light Pen is a computer input device in the form of a light-
sensitive wand used in conjunction with the computer's CRT
  It allows the user to point to displayed objects, or draw on the
 touch screen but with greater screen, in a similar way to a
                                             positional accuracy.
A light pen can work with any CRT-based screens, but not with
             LCD monitor, projectors and other display device.
                          A light pen is fairly simple to implement
     The light pen works by sensing the sudden small change in
    brightness of a point on the screen when the electron gun
    refreshes that spot. By noting exactly where the scanning
                                   has reached at that moment.
         A type of display screen that has a touch sensitive
transparent panel covering the screen. Instead of using a
   pointing device such as a light pen or mouse, you can
 use your finger to point directly to object on the screen.
  Although touch screen provide a natural interface with for
     computers novices, they are unsatisfactory for most
 application 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 graphics tablet (or digitizing
tablet, graphics pad, drawing tablet
is a computer input device that
allows one to hand-draw images
and graphics, similar to the way one
draws images with a pencil and
A graphics tablet consists of a flat
surface upon which the user may
"draw" an image using an attached
stylus, a pen-like drawing
apparatus. The image generally
does not appear on the tablet itself
but, rather, is displayed on the
computer monitor
A magnetic stripe card is a type
of card capable of storing data by
modifying the magnetism of tiny
iron-based magnetic particles on a
band of magnetic material on the
card. The magnetic stripe,
sometimes called a magstripe, is
read by physical contact and
swiping past a reading head.
Magnetic stripe cards are
commonly used in credit cards,
identity cards, and transportation
tickets. They may also contain an
RFID tag, a transponder device
and/or a microchip mostly used for
business premises access control
or electronic payment.
A barcode reader (or
barcode scanner) is an
electronic device for reading
printed barcodes. Like a
flatbed scanner, it consists of
a light source, a lens and a
photo conductor translating
optical impulses into electrical
ones. Additionally, nearly all
barcode readers contain
decoder circuitry analyzing
the barcode's image data
provided by the photo
conductor and sending the
barcode's content to the
scanner's output port.
OCR Short for Optical Character Recognition or Optical Character Reader,
OCR is the process where images of letters can be entered into the computer
as data using a scanner or other hardware device. OCR is far from perfect,
but is currently the best method of digitizing typed pages of text. Some
computer fax applications also use OCR to transform incoming faxes from
graphics files into word processing documents.
Some examples of how an OCR may be used would be a company that has
hard copies of manuals or other company information and wanting to convert
them into data that can be easily accessed and stored. Another example is
companies and libraries taking copies of books, magazines, or other old
printed material and using an OCR to scan it into computers.
What is MICR?
Why Magnetic Ink?
What is MICR? It’s those mysterious, funny characters at the bottom of a check, sometimes referred
to as the MICR line. These characters are the key by which all checks are automatically processed
in the United States today. This automated process is based on a technology called Magnetic Ink
Character Recognition or MICR. As the name indicates, this technology uses magnetic reading to
identify these unique numbers and characters. Currently, the United States processes over 65 billion
checks and other financial documents per year based on the details of this MICR line.
MICR technology was developed in the mid-1950s to address the volume of checks that were being
processed manually. The goal was to accelerate the check routing process to route the check back
to the location where the funds exist and to settle the transfer of funds as soon as possible.
To address this problem, a group of individuals from the American Bankers Association and
Stanford University developed a set of 14 unique characters called E13B MICR fonts. These fonts
are printed with magnetic ink or toner that when magnetized, will emit a magnetic signal that
identifies each unique character. What do the characters mean? The digits 0-9 are self-explanatory.
However, the E138 fonts have four special symbols with the following meanings:
Optical Mark Reader/Recognition is a reader that detects marks in a certain
position on a piece of paper. In this method, special printed forms are
designed with boxes which can be marked with a dark pencil or ink. Each box
is annotated distinctly so that the user clearly understands what response
he/she marking.
Such a document is read by a document reader which transcribes the marks
into electrical pulses. These pulses are then transmitted to the computer.
These types of documents are applicable in areas where responses are one
out of a small number of alternatives.
The OMR is a powerful tool that has many features. If you are using casstat
(grading tests), the OMR will print the number of correct answers and the
percentage of correct answers at the bottom of each test. It will also record
statistical data about each question. This data is recorded in the output file
created when the forms are scanned.
A microphone, sometimes referred to as a mike or mic (both
pronounced /ˈmaɪk/), is an acoustic to electric transducer or sensor
that converts sound into an electrical signal.

Microphones are used in many applications such as telephones,
tape recorders, hearing aids, motion picture production, live and
recorded audio engineering, in radio and television broadcasting
and in computers for recording voice, VoIP, and for non-acoustic
purposes such as ultrasonic checking.
Point of sale or point of service (POS or PoS) can mean a
retail shop, a checkout counter in a shop, or the location
where a transaction occurs. More specifically, the point of
sale often refers to the hardware and software used for
checkouts -- the equivalent of an electronic cash register.
Point of sale systems are used in supermarkets,
restaurants, hotels, stadiums, and casinos, as well as
almost any type of retail establishment
EFTPOS is an electronic payment method which involves goods or
services being paid for at the point of sale. The transaction may be
initiated either by the EFTPOS card (Credit/Debit card) being swiped
through a card reading device prior to the authorization of the
transaction by means of PIN number being inputted via a hand held
pad by the customer or the cards swipe being followed by the
customer signing a paper voucher.
In computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object
(such as an ornament) and converts it to a digital image. Most scanners today are variations of the
desktop (or flatbed) scanner. The flatbed scanner is the most common in offices. Hand-held
scanners, where the device is moved by hand, were briefly popular but are now not used due to the
difficulty of obtaining a high-quality image. Both these types of scanners use charge-coupled device
(CCD) or Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a
photomultiplier tube as the image sensor.
Another category of scanner is a rotary scanner, used for high-speed document scanning. This is
another kind of drum scanner, but it uses a CCD array instead of a photomultiplier.
Other types of scanners are planetary scanners, which take photographs of books and documents,
and 3D scanners, for producing three-dimensional models of objects, but these types of scanner are
considerably more expensive than other types of scanners.
Another category of scanner are digital camera scanners, which are based on the concept of
reprographic cameras. Due to increasing resolution and new features such as anti-shake, digital
cameras have become an attractive alternative to regular scanners. While still containing
disadvantages compared to traditional scanners, digital cameras offer unmatched advantages in
speed and portability
digital camera is a camera that takes video or still photographs, or both, digitally by
recording images on a light-sensitive sensor.
Many compact digital still cameras can record sound and moving video as well as still
photographs. In the Western market, digital cameras outsell their 35 mm film counterparts.
Digital cameras can include features that are not found in film cameras, such as displaying
an image on the camera's screen immediately after it is recorded, the capacity to take
thousands of images on a single small memory device, the ability to record video with
sound, the ability to edit images, and deletion of images allowing re-use of the storage they
occupied. Digital cameras are incorporated into many devices ranging from PDAs and
mobile phones (called camera phones to vehicles. The Hubble Space Telescope and other
astronomical devices are essentially specialised digital cameras.
Webcams are small cameras, (usually, though not always,
video cameras) whose images can be accessed using the
World Wide Web, instant messaging, or a PC video
conferencing application. The term webcam is also used to
describe the low-resolution digital video cameras designed for
such purposes, but which can also be used to record in a non-
real-time fashion.
Web-accessible cameras involve a digital camera which
uploads images to a web server, either continuously or at
regular intervals. This may be achieved by a camera attached
to a PC, or by dedicated hardware. Videoconferencing cameras
typically take the form of a small camera connected directly to a
PC. Analog cameras are also sometimes used (often of the sort
used for closed-circuit television), connected to a video capture
card and then directly or indirectly to the internet
1. Printer
2. Visual Display Units
3. Graph plotters
4. Speakers
5. Arm robot
A computer printer, or more commonly a printer, produces a
hard copy (permanent human-readable text and/or graphics) of
documents stored in electronic form, usually on physical print
media such as paper or transparencies. Many printers are
primarily used as local computer peripherals, and are attached
by a printer cable to a computer which serves as a document
source. Some printers, commonly known as network printers,
have built-in network interfaces (typically wireless or Ethernet),
and can serve as a hardcopy device for any user on the
network. Individual printers are often designed to support both
local and network connected users at the same time.

                       Click here to Types of printers
1. Laser printer
2. Inkjet printers
3. Dot-matrix printer
                                      Disadvantages: Non-color laser
                                      printers are more expensive than
A laser printer is a common type of   ink-jet printers (but the difference
computer printer that rapidly         is narrowing). Color laser printers
produces high quality text and        are considerably more
graphics on plain paper. Like         expensive. (but their speed and
photocopiers, laser printers employ   high quality output means they are
a xerographic printing process but    becoming more popular).
differ from analog photocopiers in    Advantages: They are quiet and
that the image is produced by the     fast and produce high quality
direct scanning of a laser beam       printouts. Running cost are low
across the printer's photoreceptor    because although toner cartridges
                                      are expensive to replace, they last
                                      a long time.
How it works: The print head
contains tiny nozzles through         Disadvantages: The ink
which different coloured inks can     cartridges can be
be sprayed onto the paper to form     expensive so running
the characters or the graphic         costs can be high. The
images.                               printing speed is slow
The ink is forced out by heat or by   compared to a laser
tiny piezoelectric crystals which     printer.
change shape when an electric         Advantages: These
current is applied across them.       printers are relatively
                                      inexpensive and produce
                                      high quality black and
                                      white or colour printing.
                                     The printing quality is low - these
How it works:                        printers produce low to medium quality
This has a print head that           black and white printing and can only print
travels across the paper.            low resolution graphics.
The head has a set of pins           Because of the impact of the pins against
which are pushed out to form         the paper, these printers can be quite
the shape of each character
The pins hit an ink ribbon           The purchase cost is low and the
against the paper as the print       running costs are very low.
head moves along.                    They can print fairly quickly, particularly if
An animation showing how             you remember that multiple copies are
head of a 21 pin dot-matrix          being printed in one print run.
                                     They are robust and can operate in harsh
printer moves across the
paper, firing the pins that strike   If several sheets of self-carbonating paper
the ink against the paper.           are placed into the printer then the impact
                                     will produce multiple copies.
A monitor is a peripheral device which
displays computer output on a screen.
Screen output is referred to as soft copy.
Types of monitors:
   Cathode-ray tube (CRT)
   Liquid Crystal Display (LCD or flat-panel)
Resemble televisions
Use picture tube technology
Less expensive than a LCD
Take up more desk space
and use more energy than
LCD monitors
Cells sandwiched between two transparent layers form
Used for notebook computers, PDAs, cellular phones, and
personal computers
More expensive than a CRT monitor
Take up less desk space and use less energy than CRT
Types of LCD monitors:
     Passive-matrix LCD
     Active-matrix LCD
     Gas plasma display
     Field emission display
Screen size – The diagonal measurement of the screen
surface in inches (15, 17, 19, 21)
Resolution – The sharpness of the image determined by
the number of horizontal and vertical dots (pixels) that the
screen can display (800 x 600, 1024 x 768, 1600 x 1200)
Refresh rate – The speed at which the screen is redrawn
(refreshed) and measured in Hertz (Hz) (60Hz, 75Hz)
the flat-bed plotter uses high precision motors to draw on paper with
colored ink pens. The motors move an arm across the paper in the ‘x’
direction and a pen unit up and down the arm in the ‘y’ direction. An
electromagnet lifts and drops the pen onto the paper.
Plotters are often used in science and engineering applications for drawing
building plans, printed circuit boards and machine parts. They are fast and
accurate but relatively expensive compared to printers. They can
produce far larger printouts than standard printers, up to the size of a
small room.
 Braille printer - by converting text into the Braille code, this printer
produces patterns of raised dots on paper for use by the blind.
Computer speakers, or multimedia speakers, are external speakers, commonly
equipped with a low-power internal amplifier. The standard audio connection is a 3.5mm
(1/8 inch) stereo jack plug often color-coded lime green (following the PC 99 standard)
for computer sound cards. A few use an RCA connector for input. There are also USB
speakers which are powered from the 5 volts at 200 milliamps provided by the USB port,
allowing about 1-watt of output power.
A arm robot is a robot manipulator, usually programmable, with similar functions to a
human arm. The links of such a manipulator are connected by joints allowing either
rotational motion (such as in an articulated robot) or translational (linear) displacement.
[The business end of the kinematic chain of the manipulator is called the end effector
and it is analogous to the human hand. The end effector can be designed to perform any
desired task such as welding, gripping, spinning etc., depending on the application. For
example robot arms in automotive assembly lines perform a variety of tasks such as
welding and parts rotation and placement during assembly.

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