SCANNING DEVICES
(INPUT DEVICES)
Scanners
Scanners use laser beams and reflected light to translate
drawings, photos and even text into digital form. These images
can then be processed by a computer, displayed on a monitor,
stored on a storage device or communicated to another
computer. When scanning, you usually lay the image you want
to scan on a flat plate of glass on the scanner.
Barcode Readers
A barcode is made up of columns of thick and thin lines, at the
bottom of which a string of numbers is printed.
A laser beam from the scanner scans the item’s barcode and
the beam is reflected back from the barcode into the scanner.
The information provided by the differing thicknesses of line in
the barcode is then sent to a computer for processing.
Using the item number detected in the barcode, the computer
also searches its memory to find the matching item number
Magnetic Ink Character Recognition (MICR)
MICR is used to read data on cheques. Data such as cheque
number, bank branch code and account number are printed at
the bottom of the cheque using special magnetic ink. When the
cheque is cashed, the amount on the cheque is also typed onto
the cheque by the bank, using magnetic ink. The cheque can
then be processed using an MICR reader. The ink is
magnetised by the MICR reading, which then recognises the
magnetic pattern of the numbers. When the cheque is cashed
money will be transferred from the customer’s account to the
account of the person who has cashed the cheque.
Optical Mark Readers (OMR)
OMRS process marked data by detecting and measuring the
positions of dark patches on a sheet of paper. The OMR detects
the intensity of light reflected from certain areas on a form.
Dark areas reflect less light. The OMR recognises these dark
areas and sends this data to a computer.
Optical Character Recognition (OCR)
Optical Character Recognition (OCR) involves the reading of
text from paper and translating that text into electronic text in
the computer so that it can be manipulated. All OCR systems
include an optical scanner for reading text and sophisticated
software for analysing images.
Magnetic Strip Codes
A short length of magnetic tape can be sealed into plastic card
and be used to store data. When the card is used, the magnetic
strip can be read by a computer, which identifies the card and
the bank account of the card holder and transfers money as
needed.
Smart Cards
The smart card, also called a chip card, has a small microchip
attached to it. This chip provides a big security advantage over
magnetic strip cards. The computer chips also hold more
memory than magnetic strips.
Digital Cameras
Digital cameras do not have film but instead they have a
sensor that converts light into electrical charges. A processor
then converts this information into a digital data. The amount
of detail that the camera can capture is called the resolution
and it is measured in pixels. The more pixels your camera has,
the more detail it can capture. The information can then be
copied onto a computer disk. Using special software, the
images can be edited and displayed on the computer.
Voice Recognition
Voice recognition is the ability of a computer system to accept
spoken words as input for processing. The sounds are
converted into digital patterns and compared to stored
patterns in the computer. If a match is found, the word is
“recognised” and the computer can perform operation based
on that word.
Biometric Systems
Biometrics refer to the automatic identification of a person
based on his/her individual body characteristics (face,
fingerprints, hand geometry, iris, retina vein and voice).
SOFTCOPY OUTPUT
DEVICES
Cathode Ray Tubes
Images are represented on the screen by individual dots called
pixels. A pixel (short for picture element) is the smallest unit
on the screen that can be turned on and off or coloured in
different shades. The number of pixels determine the
resolution of the screen. Resolution is the clarity or sharpness
of an image when displayed on the screen. The more pixels
there are on a screen, the greater the level of detail that can
be shown in an image, and the higher the resolution. If the
resolution is low, images are displayed with jagged edges. A
screen with high resolution displays image with very sharp,
clearly defined lines and curves.
Flat Planel Display Screens
These screens consist of two plates of glass with a substance
in between them that creates the image on the screen. The
different types of flat screens are liquid crystal display (LCD),
electroluminescent display (EL) and gas-plasma display.
Video Graphics Card
A video graphics card, also called a video display adapter, is a
circuit board that determines the resolution, number of
colours, and speed with which images appear on the screen.
Output Of Sound
Normal music system speakers are used to output sound. The
quality of sound depends on the type of system used, the size
of the speakers and the computer’s audio card. The audio card
is a circuit board in the computer that processes sound.
HARDCOPY OUTPUT
DEVICES
Impact Printers
Impact printers produce their output when the printing
mechanism presses against a ribbon which then hits the paper.
The two main types of impact printers are dot matrix and line
printers.
A dot matrix contains a print head with pins arranged in a
rectangular matrix of rows and columns. These print one
character at a time. When a character or image is to be
printed, the pins that required to form that move forward and
strike an inked ribbon which then strikes the paper. Ink is
transferred from the ribbon to the paper.
A line printer prints one line at a time. The two main types
are chain printers which contain characters on a rotating
chain, and band printers which contain characters on a
rotating band.
Non-Impact Printers
Non-impact printers are faster, quieter and produce better
quality print than impact printers. Characters and images are
formed without the printing mechanism making any direct
physical contact with the paper. The main types of non-impact
printers are laser printers (page printers), inkjet printers and
thermal printers.
In a laser printer, a laser beam creates an image of a page on
a light sensitive drum, treated with a magnetically charged
powder called a toner. The paper is then pressed against the
drum and heat and pressure are applied. The image is then
transferred to the paper.
Inkjet printers produce their output by spraying small
electrically charged droplets of ink from four nozzle through
holes in a matrix, at high speed onto paper.
Thermal printers, like dot matrix printers, have a print head
that is made up of pins arranged in a matrix. These pins are
heated electrically and burn the characters onto heat-sensitive
paper.
Plotter
A plotter is a specialised output device designed to produce
high quality graphics in a variety of colours.
