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© Ashek Mahmud Khan, Dept. of CSE (JUST)

Peripherals and Interfacing

Input /Output Devices

What is input Devices?

Ans: An input device is any device that provides input to a computer. In computing, an input

device is a peripheral used to provide data and control signals to an information processing system

such as a computer or other information appliance. Examples of input devices include keyboards,

mouse, scanners, digital cameras and joysticks.

What is Output Devices?

Ans: An output device is an electromechanical device, which accepts data from a computer and

translates them in to a form, which is suitable for use by the out site world (the user) Several output

devices are available today. Examples of output devices Monitors, Printers, plotters, Screen

image projector, Voice response system.

What is digitizer?

Digitizer: Digitizer convert analog or physical input into digital image. This makes them related to

both scanners and mice, although current digitizer serve completely different role.

Feature: Digitizer is considered the most important feature of flexible-resolution and image

recognition.

What is the difference between Digitizer and Scanners?

Ans: Difference between Digitizer and Scanners-

Digitizer Scanners

(i) Digitizer convert analog or physical input

into digital image.

(i) A computer scanner optically scan an

object such as document and data convert the

information into a digital image.

(ii) Digitizer is a medium size machine. (ii) Scanner is large machine than Digitizer.

(iii) Digitizer converts point lines and area on

maps into digital data.

(iii) It converts document or image into

digital data.

What is Scanners?

Scanners: A computer scanner optically scan an object such as document and data convert the

information into a digital image. The two commonly used types are: (i) Flatbed scanner (ii) Hand-

held.scanner.

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(i) Flatbed scanner: A flatbed scanner is like a copy machine, which consists of a box having a

glass plate on its top and a lid that covers the glass plate. It takes about 20 seconds to scan a

document of size 21cm * 28cm.

(ii) Hand-held scanner: A hand-held scanner has a set of light emitting diodes encased in a small

case, which can be conveniently held in hand during operation.

Write the short note on OCR.

OCR: OCR stands for Optical Character Recognition. OCR is the recognition of printed or written

text characters by a computer. It is the application software that allows a computer to recognize

printed or written characters, e.g. letters, numbers, punctuation marks, and pictograms using an

optical scanner for input. OCR is being used by libraries to digitize and preserve their holdings.

Advanced OCR system can recognize hand printing.

Or,

OMR: OMR stands for Optical Mark Reader. A special scanning device that can read carefully

placed pencil marks on specially designed documents.

Difference between OCR and OMR.

OCR OMR

(i) OCR stands for Optical Character Recognition. (i) OMR stands for Optical Mark Reader.

(ii) OCR is used for converting printed documents

to an editable format.

(ii) OMR is typically used in grading.

(iii) OCR reads character. (iii) OMR reads marks.

OCR

Scanner

Bitmap

Page Of text

ASCII text 2-3

KB per page

Fig: OCR Mechanism

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© Ashek Mahmud Khan, Dept. of CSE (JUST)

(iv) OCR does require a complex recognition

engine.

(iv) OMR does not require a complex

recognition engine.

Bar code: A bar code (often seen as a single word, barcode) is the small image of lines (bars)

and space. A graphical representation of a product's identifying information formed by a two-

dimensional pattern of black and white shapes. Barcodes are able to be read by optical devices,

such as a barcode reader or scanner, and are most commonly composed of parallel black and white

lines. Barcodes are used to automate the transfer of product information, such as price, from the

product to an electronic system, such as a cash register. A bar code symbol typically consists of

five parts: a quite zone, a start character, data characters, a stop character, and another quiet zone.

Fig: Bar code

A barcode reader is used to read the code. The reader uses a laser beam that is sensitive to the

reflections from the line and space thickness and variation. The reader translates the reflected light

into digital data that is transferred to a computer for immediate action or storage.

The Purpose of a Barcode:

A barcode is a unique product identifier on retail products that includes a sequence of lines,

characters and numbers. Barcodes help track sales of products and relationships with customers.

Barcode Rader: A barcode reader is a device, which is used for reading barcode data. It may be a

hand-held scanner.

Magnetic card readers: A magnetic card reader is a device used to read magnetic stripe cards,

such as credit cards. No drivers needed. No software needed. Just pure wonderful serial.

Touch screen: A touch screen is a computer display screen that is also an input device. The

screens are sensitive to pressure; a user interacts with the computer by touching pictures or words

on the screen.

How it works!!-Touch screen technology.

(1) The touch sensor is a panel with a touch responsive surface. Systems are built based on

different types of sensor: Resistive, Surface wave and Capacitive.

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(2) The controller is the hardware that converts the voltage changes on the sensor into signals the

computer or other device can receive.

(3) Software tells the computer, smart-phone, game device etc. What’s happening on the sensor

and the information coming from the controller.

Printer: Printer is an output device that prints hard copy. There are various types of printers in use

today. Such dot-matrix printer, laser printer, toner printer, inkjet printers.

Dot-matrix printer: Dot-matrix printers are character printers, which print one character at a time.

Dot-matrix printers are uses a print head that runs back and forth, or in an up and down motion, on

the page and prints by impact.

Laser printer: Laser printers are page printers, which print one page at time. The main

components of a laser printer are a laser beam source, a multi-sided mirror, a photoconductive

drum and toner.

Difference between Printer and Scanner:

Printer Scanner

(i) Printer is an output device that prints hard

copy.

(i) The scanner is an input device that scans

image to be use for software manipulation.

(ii) A printer prints out documents. (ii) A scanner copies them into computer.

(iii) There are different kind of printers such

dot-matrix, laser printer, toner printer.

(iii) Scanner can be a flatbed scanner and hand

held scanner.

Monitors: Monitor are by far the most popular output devices used today for producing soft-copy

output. They display the generated output on a television like screen. Monitors are very similar to

televisions but usually display information at a much higher resolution. There are three types of

monitor. Such: (i) CRT monitor (ii) LCD monitor (iii) DLP monitor.

CRT (Cathode Ray Tube) monitor: It is an old monitor. It takes a large area on the desk and

spend more electricity than any other types of monitor. It uses very old format of monitor

technology and uses cathode ray tube.

LCD (Liquid Crystal Display) monitor: Sometimes it is called flat panel display. It is new

technology than CRT. LCD monitor spend less electricity than CRT monitor.

Advantage of LCD monitor:

(i) Low power Consumption.

(ii) Low cost.

(iii) Small size.

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© Ashek Mahmud Khan, Dept. of CSE (JUST)

Disadvantage of LCD monitor:

(i) LCD have less color capability.

(ii) Resolution is not as good as that of a CRT.

(iii) LCD’s do not emit light.

DLP (Digital light processing) monitor: Which uses very small mirrors to direct the light.

Difference between LCD and CRT monitor:

LCD CRT

(i) LCD means Liquid Crystal Display. (i) CRT means cathode ray tube.

(ii) Low power Consumption. (ii) High power Consumption.

(iii) Low cost. (iii) Low cost.

(iv) Small size. (iv) Large size

Mouse: 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.

Keyboard: External input device used to type data into some sort of computer system whether it

be a mobile device, a personal computer, or another electronic machine. A keyboard usually

includes alphabetic, numerical, and common symbols used in everyday transcription.

There are many types of computer keyboards. For instance, multimedia computer keyboard,

membrane computer keyboard, slim computer keyboard, Capacitive key switches etc.