Module 5 (Input Devices & OUTPUT DEVICES)

Structure of the Lesson

9.1 Objectives

9.2 Introduction

9.3 Input devices

9.3.1 Keyboard

9.3.2 Mouse

9.3.3 Joy Stick

9.3.4 Trackball

9.3.5 Light Pen

9.3.6 Touch Pad

9.3.7 Digitizer

9.3.8 Scanner

9.3.9 MICR

9.3.10 OCR

9.3.11 OMR

9.3.12 Biometric Devices

9.3.13 Magnetic Card

9.4 Summary

9.5 Glossary

9.6 Suggested Answer to SAQ

9.7 References/Bibliography

9.8 Suggested readings

9.9 Model Questions

9.1 Objectives

CPU processes the data for computer and generates the information. But for execution, data and program must be entered into the memory.  The job of entering data and instruction in computer is done by means of input devices.  Instructions are created by the programmer in the software industry, but data is created in varied number of  places in many ways. Before entering the data in computer memory for execution, it must be translated in to computer understandable form. This conversion job is done by input devices. There are some data or input which can go directly in computer memory for processing e.g. bar codes; speech data etc. For this type of input, we use direct input devices like bar code reader, MICR, Optical Mark Reader etc. Some data is in English like language, for these types of data we use manual devices like keyboard, mouse etc. This chapter will give detail information and functioning of both direct and manual input devices.

9.2 Introduction

We had already studied that; computer receives the input and delivers the output through input and output unit. Input and output devices are the hardware elements of input and output unit of the computer system. These devices are interface between the user and computer. These devices mediate the interaction between computers and external environment. Input devices are used to command or to give instructions to computer. Output devices communicate the result generated by computer to external environment. Input output devices are hardware devices as well as input/output channels. As computer is an electronic device it receives commands as electronic signals. So, input devices translates the user action into signals, Similarly, Computer generates the results in the form of signals and output channels translate these signals into human under stable language.

9.3 Input devices

Input devices are essential hardware components of computers. These devices help the user to input the commands for computer. Input devices are the hardware which input the data for computer into main memory. These devices are also called input peripherals. Without these devices, computer is handicapped and cannot input data or instruction for execution. Some commonly used Input devices and their functioning is listed below.

9.3.1 Keyboards

Keyboard is the basic and essential component of computer system. This device is used to key in commands and data into the computer. Computer is incomplete without keyboard. It is primary input device. A standard keyboard has 101 keys and each key is responsible to send different signals to CPU.

·       Functioning of keyboard

When we press key from keyboard, then a very small chip inside the keyboard called keyboard controller receives this keystroke and stores a code of that keystroke in keyboard buffer (a small temporary memory to store data). The stored code is called key scan code (identifying as number). Now keyboard controller sends the signals to CPU. This signal is called interrupt. CPU handles this interrupt, by putting aside the job which it is processing and reads the key scan code from keyboard buffer and store it in to main memory. Keyboard buffer can actually store a number of keystrokes at once. 

·       Keyboard keys

Most commonly used keyboard has 101 keys and more

a) Alphabetic keys: These are alphabet keys from a-z. There are two shift keys to make them capital. Also there is a caps lock key to change the uppercase (capital letters) and lowercase (small letters) mode of keyboard.

b) Numeric keys:  The numeric keys are located on the keyboard at two places. You can see on the top row above the alphabet keys.  A second set of these keys is on the right hand side of the keyboard. 

c) Function keys: There are 12 function keys named as F1, F2, F3,…,F12 on the keyboard. Each key has its own specific function in different software.

d) Arrow keys:    There are four arrow keys for cursor movement on the screen  i.e. Top arrow key, bottom arrow key , right arrow key, left arrow key. These keys have special space on keyboard called arrow keypad. These key functions are also available on numeric keypad and we can use them with num lock off.

e) Control key: This key does not have its own special purpose. It is used with combination of other keys to generate different commands.

f) Shift key: This key is used for typing capital letters and special characters. Some times it is used to generate special commands for computer.

g) Backspace and Del key: Backspace key is used to delete the character left on the cursor position. Del key is used to delete the character on the right hand side of cursor.

h) Spacebar: To enter space between two words.

i) Enter key: As name suggests this key is used to enter the command to computer system. This key is also used to enter new line in the document.

Keyboard

·       Standard  Keyboards

The standard 101/102-key PC keyboard layout was invented by Mark Tiddens of Key Tronic Corporation in 1982. This layout was the foundation for the next generation of keyboard. Thin keyboard contains alphabet keys, numeric keys, Tab key, Caps lock key, function keys etc. This keyboard has special port to connect with computers called PS/2 port.    

·       USB Keyboards

This is latest innovation in keyboard interfacing with PC i.e. USB port. This port is called Universal serial bus port. Now, these days, keyboard connector to computer is USB port instead of PS/2.  USB port is standard port which can be used to interface computer with all hardware devices. No special port for special hardware is required.

To use a USB keyboard Computer must

■ Have a USB port in the system

■ It should run Microsoft Windows 98 or above version of  operating system in computer.

■ Have motherboard with USB support features.

USB support features means; Motherboard should have a highly advanced chipset that provides support to the interface of USB keyboard with Operating system GUI.

·       Portable Keyboards

Due to progress of technology, computer has become portable; due to this the size of input device like keyboard has become smaller in size with reduction of keys in standard layout. Different hardware companies have given different layout of keyboard with theirs portable computers, but unfortunately none of them has become a standard, In concern with portability, many types of keyboard are available like software keyboard, projected keyboard, Foldable keyboard etc.

9.3.2 Pointing Devices (Mouse)

The mouse was invented in 1964 by Douglas Englebart from Stanford Research Institute (SRI) (Source Wikipedia). Pointing device mouse resembles with rat. Now these days, this device has become the essential part of every computer. All window based PC’s use mouse. However, with this device you can not type. It is a pointing device that lets you move a cursor on the screen just by moving a mouse around the flat surface.  Basically, this input device is used for Graphical user interface. The pointer is an on screen object, looks like an arrow, used to select text and interact with the GUI program. This pointer is also called mouse pointer.

Mouse

Basic structure of Mouse

Mouse has three basic buttons

Left button: Clicking of left button means to press the  left button. This button is used for selecting and other operation in mouse functioning.

Right Button: This button has a special use. This button is used for popup menus and other options depending upon the software we are using.

Center button: This button is also called scroll button. This button is responsible for the scrolling in the document.

There are four basic functions of a mouse

A)    Clicking          B) Double clicking      C) Right clicking         D) Dragging

·         Types of mouse: There are three basic types of mouse:-

1.      Mechanical mouse

2.      Optical mouse

3.      Optmechanical mouse

Mechanical Mouse

Earlier this was the most popularly used pointing device . A mechanical mouse contains a small rubber ball that protrudes through a hole in the bottom of the mouse case. The ball rolls inside the case, when mouse is moved on the flat surface.  There are two rollers inside the mouse that touch the rubber ball. One roller is to detect the motion along x-axis and other to detect the motion along y-axis. When the ball rotates the roller moves. Each of the rollers is connected to the shaft which spins a disk with holes in it, so moving a mouse moves the disk. On the either side of disk there is an infrared sensor. These sensors sensitize the movement of roller with the movement of balls.

Optical Mouse

Now with modern PC, we are using optical mouse. This is new generation of mouse. This mouse works with the science of optics. This mouse depends on optics ( light rays ) for the functioning. Optical mouse uses light to track the movement instead of a ball, this ball has small LED (Light emitting Diode). These LED reflect the light on optical sensor. These sensors are responsible for sensing the reflected light by LED and control the motion of pointer according to it.

Optmechanical Mouse

This mouse is a mixture of the technology used in optical and mechanical mouse. This mouse takes the input as movement of rubber ball and this input is translated into signals for computer by optical sensors. This mouse works on the technology of optical as well as mechanical mouse.

Optical mouse VS Mechanical mouse.

1. In optical mouse the movement of cursor is dependent upon the light sensors but in mechanical mouse, movement of cursor depends upon the mechanical movement of the rubber ball.

2. Mechanical mouse is heavier than optical mouse.

3. Optical mouse is faster than mechanical mouse.

4. Optical mouse is more sensitive than mechanical mouse and should be handled with care.

5. The life of optical mouse is more than mechanical mouse.

6. Dust clustering problem is there in mechanical mouse around the roller. In optical mouse there is no such problem.

7. Mechanical mouse can work on any flat surface like glass etc. But the optical mouse can not work well on the reflecting surface like glass. Now these days many manufacturers have offered wireless keyboard and mouse. These devices have either infrared port or short range radio Tran receivers to communicate with PC. These devices are used widely in home offices and as a game controller. The technology behind the wireless mode is infrared rays and radio transreceivers. But better, is radio frequency input device. Major vendors for these devices are Logitech, Microsoft and many more.

Major issues with wireless pointing Device

Wireless devices attach with computer without any wire. They communicate with computer    through wireless signals.

·         Hindrance issue:  Infrared wireless does not work well if there is hindrance between the infrared sensors.

·         Battery life: These devices work with battery such as AAA battery. Battery life is usually rated at about six months. Be sure, you have spare batteries for the input device to avoid failures due to running out of battery power.

·         Location: The range of wireless devices can vary from 6 feet to as much as 30 feet. If you try to use these devices out of range they will not work well.

9.3.3 Joystick

Joystick is input device used as game control for playing games. It consists of a small, vertical lever mounted on a base that is used to steer the screen object. Some joysticks are mounted over keyboard, other function as stand alone unit. The joystick can be moved left or right, forward or backward. . The movement of the joystick is responsible for the cursor movement on the screen. Potentiometer is attached on the base of joystick. The handle of the joystick is for measurement of movement and there is spring which returns the handle to center position when it is released. It has one or more button and is programmed to act as switches and is responsible for the particular action on the screen. For Beginners it is difficult to use and control joystick, because the slight movement of handle is amplified 5 or ten tomes movement of the object on the screen. Joystick is used to control the velocity of the cursor on the screen rather than to absolute position the object on the screen. Some joystick can be twisted clockwise or anticlockwise directions.  Joysticks connect with computer by basic USB port and often have its device driver; it should be installed first into computer to connect the functioning of joystick with computer.

Joystick

9.3.4 Trackball

Trackball is a pointing device made up of ball held by socket of sensor to detect the movement of the ball about two axes. The rolling of the ball send the coordinate information to the sensor and these information is transmitted to computer in the form of signals to the computer and computer controls the movement of cursor according to that. The ball is rolled by the user with thumb or hand. User can rest his thumb on the naked ball and finger on the buttons. To move the cursor on the screen user rolls the ball and to select the operation user click the button. Trackball has a wider range of working than a mouse. In case of mouse the edges of working area may hinder the movement of mouse; operator will have to lift and reposition the mouse. This problem does not remain with trackball. These devices  are mostly used with portable PC and are widely used for designing purpose.

Trackball

9.3.5 Light Pen

A light pen is a small pen shaped device, which contains light sensors. The light pen is used to select the object on the screen by tapping the pen on the screen or by pointing the device on the object location and pressing the button on the pen. The light pen does not need a special screen . It works on normal display screen.  It allows the user to draw on the screen . It works well with normal CRT display but not works with LCD display device.  It is simple to implement and use. There is a light sensor on the tip of the pen, and senses the light coming from the screen and sends the signal to the computer. This pen consists of a photocell placed in a small tube. As the user moves on the tip of the pen over the screen surface, cells are responsible to sense the light coming from display screen.. It has immense application in the field of computer aided designing.

Light Pen

9.3.6 Touch Screen

This is a commonly used input device in computers and mobiles. The touch screen are sensitive to pressures. Computer inputs the command and instructions to the computer by touching the screen. This input device needs a special type of GUI software for interaction purpose only.

Technologies used in touch screen

Resistive: In this technology, the screen panel is coated with a thin electrically resistive layer that is sensible to register the change  in current  by simple touch and convert it to signals for processing. Devices with these technology is cheaper than others and provide 75% of clarity and are very sensitive to sharp touch, it may damaged by touch of sharp objects.

Capacitive: This technology uses a material for screen panel that stores electrical charge. When screen is touched, a small amount of electric charge is drawn to the point of contact. The circuit inside the panel measures the charge and sends the information to controller for processing. A finger or stylus is used for touching purpose. Theses technological devices have high clarity.

Surface wave: Wave technology is used in display panels. Ultrasonic waves passes over the touch panels. When panel is touched, the waves get absorbed on that portion of the panel. This absorption is registered and sent to the controller for processing.  These screens are much sensitive and may be easily damaged by outside elements.

9.3.7 Digitizer

A digitizer or graphic tablet is similar to a light pen: however, instead of drawing on the screen, a separated small surface tablet is used which a special stylus is moved. The work surfaces of these tablets contain hundred of copper wires in the form of a grid, which are connected to the computer. Each copper wire receives electric pulses.  When stylus or pen is moved on copper wired surface, it sensitize the electric pulses and coverts it onto signals and passes it to controller for processing.  Digitizer has immense applications in graphics and designing industry. With this device objects can be drawn or erased and coordinates can be marked on the screen. Digitizers are normally used in mechanical and architectural fields for drawing. With this device sketch of the drawing is traced and convert it into digital form.

Graphic Tablet

9.3.8 Scanners

A scanner read text, photographs and graphics from paper which are converted into digital information for processing, storage and output.  These devices are responsible for converting the hard copy data into digital data.  Scanner scans a pattern from the paper and generates the digital signals corresponding to the pattern. Scanner uses light to examine the patterns.  

Scanners are of two types

Handheld scanners: These devices read data like bar code in books and from any packed material. These scanners use laser technology to scan the data. It has a set of light emitting diodes. It is placed over the material to be scanned and slowly dragged from top to bottom. The light emitted by the diodes is not reflect by the dark portion of the data written on the paper. This information is converted into data and stored as bitmap.

Flat-bed scanner: It consists of a box with glass plate on top which is used for placing the document which is to be scanned. The light beam is situated under the glass plat and moved in horizontal or vertical direction to scan the paper. Light beam projected on the paper under the glass, light does not reflects back from the darken area of the paper which is sensitize by the sensor and converted it into digital information for processing.

Various types of scanner device are there, and used as input devices in various applications.

 9.3.9 MICR

MICR is a short form for Magnetic Ink Character Recognition. This technology was suggested in 1950 by bankers of United state of America. During 1958, American Bankers Association (ABA) actually implemented this technology in their banks.  This technology is related to the recording of information on document by means of magnetic ink. Magnetic ink contains magnetic particles, which are charged to read printed characters. When documents having magnetic ink character are passed through a strong magnetic field, the ink coded characters become magnetized and are recognized by the magnetic ink document reader. This technology uses magnetically chargeable ink to print the numbers and special characters on the banking cheques or other   financial documents. This ink is used to print the cheque number or account number and also digital information of the bank like IFSC code of branch etc.  MICR technology is widely used in banking industry. Because it allows the digital processing  of printed data.

Advantages of MICR

·         Magnetic ink characters are machine readable, so they can be used directly for computer input.

·         It reduces the amount of data entering job to input the necessary information in to computer for processing.

·         Magnetic ink characters can even read a roughly handled document

·         MICR code are human readable, so that the characters read by these devices are easily cross checked by humans.

·         It is a compact machine and easy to store and handle.

MICR

9.3.10 OCR

OCR (Optical Character Recoginition) special kind of scanner, which is used to convert soft copy of a printed materials. This matter may be bar codes, text or may be graphics. Bar code reader or scanner falls in this category. Optical character recognition readers examine a character as collection of small dots. Once the whole character is scanned and converted into digital pattern of dots. It is matched with pre stored digital patterns to recognize the character. Whichever presorted pattern is matches or nearly matches with scanned pattern , the corresponding character is considered to be read.

Advantages

·         OCR is used in digitization of data and knowledge. OCR is highly used in library to digitize books and other information to preserve the knowledge forever.

·         OCR reduces the effort of data entering

·         It provides the accuracy.

Disadvantages

·         It is expensive

·         It can recognize only printed data, not hand written data

OCR

9.3.11 OMR

OMR is a short form of Optical Mark Reader. OMR is a method to convert the marks made by pen or pencil at a predefined position on paper and convert it into digital information. The OMR data enter system works to convert the presence or absence of marks into a computer data file. In this method special preprinted format are designed for marked input data from user. OMR used for multiple choice question answer sheets where large data is accepted. These preprinted filled documents are passed under a light source and presence of mark is detected by measuring very accurately. The position of marks is identified and converted it into relevant digital data for further processing. In competitive exams OMR sheet is given to students to marks their answer by dots on relevant box. These answer sheets are passed through the laser light. The darkened areas on the sheet do not reflect the light and marks are identified on particular location.

Advantages

1)      It maximizes the data reliability

2)      It is cost effective

3)      It processes the bulk of data in fraction of seconds.

4)      Easy to implement and use.

Disadvantages

1)      They are slow devices as compared to other digital device.

2)      Unable to read roughly handled document

3)      It is forced to work in the given answer format.

OMR

9.3.12 Biometric Devices

Biometric is a blend of two Greek words, 'bio' and ‘metric’, which means measurement of living organisms. These devices are scanners. Which scan the biological information from the human body. They scan different biological traits of person like fingerprint, retina and face. This technology has popularized due to progress in criminal and forensic science during the 19th century, when scientists are able to use biometrics to catch criminals by identifying their fingerprints. They use to store the fingerprints of criminals in memory of computer. They do have the database of fingerprint of all criminals. When they found any fingerprint at crime scene. They use computer software to compare the found fingerprint with database fingerprints to identify the criminals.

Various types of biometric devices are there

• Face scanner:  This device scans the faces and stores the measurement and geometric information of the face into computer. The geometry of face is like Distance between the person’s chin, eyes, nose and mouth, the shape of jaws etc.
• Finger scanner - Biometric finger scanner identifies the persons by their finger print. Fingerprint is a unique trait of every person. Every person has a very distinct  finger prints. So the information of finger scanning is done by finger print scanner and store in computer.
• Hand scanner - Like your fingerprint, the palm of your hand is also unique to you. A biometric hand scanner will identify the person by the palm of their hand.
• Retina scanner: This scanner scans the retina of the eye and converts it into digital information for storage purposes. Like fingerprints retina of the eye is also a unique biological trait.  Retina scanner is just mounted in front of the eye and it scans the image. This scanner is a very sensitive scanner and used is for some special purposes.

Advantages

1)   These scanners are widely used for security purposes. Biometric devices are widely used, to prevent the entry of unauthorized person in restricted area.

2) Finger print scanners are used in multinational companies to mark attendance.

3)   Widely used in laptops to prevent the unauthorized access to your important data.

9.3.13 Magnetic Card

A magnetic card is a rectangular object that contains a magnetic strip. This magnetic strip is responsible for storing data magnetically. This information may be about your bank account or about the information of an employee. To read the information a magnetic card reader is required which retrieves the stored information on the card. The examples of a magnetic card are ATM cards, Credit card etc. These cards are swiped through the magnetic card reader. Magnetic card reader reads the magnetic information on the card and converts it into digital data for further processing. Magnetic card reader is widely used in ATM machine and shopping mall or retail stores.

9.4 Summary

This Chapter has given an introduction to the Input/output devices. It gives a detailed listing of the various types of input devices. The concepts are also very clearly understood by observing the figures in the chapter. The Chapter also gives us the knowledge of devices like OMR, MICR and Biometric Devices etc. Various input devices have been introduced with the technological advancement to facilitate the human jobs. These input devices are widely used in almost every field and also new devices have emerged according to their need and utility in their respective fields. For example, MICR was suggested by the banking industry and thus it was invented for banking industry. Biometrics devices were suggested by Security agencies and hence invented for these industries and also widely used in other organization for different purposes.

9.5 Glossary

·         Keystroke                                    A key press is called keystroke

·         Keyboard buffer             A small memory to store keystroke

·         LED                                 Light Emitting Diode

·         USB                                  Universal Serial Bus

·         OCR                                 Optical Character Recognition

·         OMR                                Optical Mark Reader

·         MICR                               Magnetic Ink Character Recognition

·         LBA                                 Logical Block Address

·         Infra Red Sensor                        The sensor to sense the infrared light

·         LCD                                 Liquid Crystal Display

·         ATM                                Automatic Teller Machine

·         CRT                                 Cathode Ray Tube

9.6 Suggested Answer to SAQ

Question: Explain the functioning of most commonly used keys on keyboard?

Ans:   Most commonly used keyboard has 101 keys and more, but only 101 keys are of important keys.

a) Alphabetic keys: These are alphabet keys from a-z. There are two shift keys to make them capital. Also there is a caps lock key to change the uppercase (capital letters) and lowercase (small letters) mode of keyboard.

b) Numeric keys:  The numeric keys are located on the keyboard at two places. You can see it on the top row above the alphabet keys. A second set of these keys is on the right hand side of the keyboard. 

c) Function key: There are 12 function keys named as F1, F2, F3,…,F12 on the keyboard. Each key has its own specific function in different software.

d)  Arrow keys: There are four arrow keys for cursor movement on the screen  i.e. Top arrow key, bottom arrow key, right arrow key, left arrow key. These keys have special space on keyboard called arrow keypad. These key functions are also available on numeric keypad and we can use them with num lock off.

e)   Control key: This key does not have its own special purpose. It is used with combination of other keys to generate different commands.

f) Shift key: This key is used for typing capital letters and special characters. Some times, it is used to generate special commands for computer.

g) Backspace and Del key: Backspace key is used to delete the characters left on the cursor position. Del key is used to delete the characters on the right hand side of cursor.

h) Spacebar: To enter space between two words.

i) Enter key: As name suggests, this key is used to enter the command to computer system. This key is also used to enter new line in the document.

Question: Explain the advantages and disadvantages of OCR?

Ans:     Advantages

1)      OCR is used in digitization of data and knowledge. OCR is highly used in library to digitize books and other information to preserve the knowledge forever.

2)      OCR reduces the effort of data entering

3)      It provides the accuracy.

Disadvantages

1)                  It is expensive.

2)                  It can recognize only printed data, not hand written data

Question: Explain the various types of Biometric devices?

Ans :  Various type of scanners are

• Face scanner:  This device scans the faces and stores the measurement and geometric information of the face into computer. The geometry of face is like Distance between the person chin, eyes, nose and mouth, the shape of jaws etc.
• Finger scanner - Biometric finger scanner identifies the person by their fingerprint. Fingerprint is unique trait of every person. Every person has unique fingerprints. So the information of finger scanning is done by finger print scanner and store in computer.
• Hand scanner - Like your fingerprint, the palm of your hand is also unique to you. A biometric hand scanner will identify the person by the palm of their hand.
• Retina scanner: This scanner scans the retina of the eye and converts it into digital information for storage purpose. Like fingerprints retina of eye is also a unique biological trait.  Retina scanner is just mounted in front of the eye and it scans. This scanner is very sensitive scanner and used for some special purposes.

Question: Explain the functioning of MICR?

MICR is used for reading the information written on the document with magnetic ink. Magnetic ink contains magnetic particles, which are charged to read printed characters. When documents having magnetic ink character are passed through a strong magnetic field, the ink coded characters become magnetized and are recognized by the magnetic ink document reader. This technology uses magnetically chargeable ink to print the numbers and special characters on the banking cheques or other financial documents. This ink is used to print the cheque number or account number and also digital information of the bank like IFSC code of branch etc. 

Question: Define Keyboard?

      Ans:   The primary input device for most computers, consisting of keys with letters of the alphabet, digits, punctuation, and function control keys.

Question: Explain joystick?

An input device generally used for games software, usually consisting of a central upright stick that controls horizontal and vertical motion and one or more buttons to control discrete events, such as firing guns. More complex models can resemble flight yokes and steering wheels or incorporate tactile feedback.

9.7 References/Bibliography

• Introduction to Computers, Peter Nortron, Tata Mc-graw Hill Publishing company Limited.
• Computer Fundamentals, P.K Sinha, BPB Publications
• Introduction to Computers  By Gary Shelly, Steven Freund, Misty Vermaat, Published By Shelly Cashman Series
• Introduction  to computer by Raj Mohan Joshi, Published by Isha Books, New Delhi
• Introduction to Computer Science , by ITL Education Solutions Limited, Published Pearson education ltd.

9.8 Suggested Readings

• Introduction to Computers, Peter Nortron, Tata Mc-Graw Hill Publishing company Limited.
• Computer Fundamentals, P.K Sinha, BPB Publications
• Introduction to Computers  By Gary Shelly, Steven Freund, Misty Vermaat, Published By Shelly Cashman Series
• Introduction  to computer by Raj Mohan Joshi, Published by Isha Books, New Delhi

9.9 Model Questions

·         Write about Input & output Devices?

·         What is difference between OCR and OMR?

·         Is Touch Screen an Input Device? Suggest your comments?

·         How does a Keyboard Work?

·         Explain the working of  Bar code scanner?

·         What is Light Pen?

·         Explain various types of Pointing Devices?

·         Write a note on Magnetic Card reader and its applications?

Structure of Lesson

10.1 Objectives

10.2 Introduction

            10.2.1            Video output Devices

                                    10.2.1.1 CRT Monitor

                                    10.2.1.2 Flat panel Monitor: LCD

                                    10.2.1.3   Flat Panel Monitor: Plasma Display

                                    10.2.1.4 Flat Panel Display: LED

                                   

            10.2.2            Audio output devices

10.2.2.1 Sound cards

10.2.2.2 Speakers

10.2.2.3 Headphones and Earphones

10.2.3 Other types of Display devices

10.3   Summary

10.4   Glossary

10.5   Suggested Answer to SAQ

10.6   References/Bibliography

10.7   Suggested Readings

10.8   Model Questions

10.1 Objectives

This chapter introduces the reader to monitors, sound systems and others. Reader will learn about the different types of monitor commonly used with computer and also the information about the functioning of monitor. This chapter will also give some tips and criteria for judging the performance. This chapter will also introduce other output unit which we are using in our computers also That output devices are sound out devices like speakers, headphones etc.

10.2 Introduction

The display devices are playing important role as interface between user and computer. Before the invention of these display devices we used teletypewriter as output device, this device was large and very loud and generated the output on the paper by printing on a roll of paper. But, with the invention of monitor as a display device, the nature of computer processing has changed its definition. With the invention and advancement of technology, the monitor has changes its shape, size and functioning. Sound output devices have also been introduced in computer system as output devices. So we can classify the output devices into two basic types

·         Video Output devices

·         Audio Output devices.

10.2.1 Video output Devices

The  most important output devices attached to our computers are Monitors, LCD’s, LED’s etc. We use different names and with each day they are improving with new features like HD, 3D, smart display etc. But, there are some basic characteristics by which we can differentiate the monitors from one another.

      Size: The size of monitor affects the vision of image on the monitor. Of course, with bigger the size of the screen bigger, the object will appear on the screen. So size of the monitor is measured diagonally in inches. A 19 inch monitor measures 19 inches from the lower left to the upper right corner. This is the actual view area of the screen. The flat panel display device has larger view area than other monitors.

      Resolution: This term refers to the sharpness and clarity of the picture. A monitor resolution is determined by the number of pixels on the screen, expressed as matrix. The more the pixels on the screen more the better is the resolution and so better is the picture quality of the monitor.
There are various standard for monitor resolution. The video graphic array (VGA) standard is 640 X 480 pixels and also various standards also given in table.     

Resolution	Abbreviation	Standard Designation
640×480	VGA	Video Graphics Array
800×600	SVGA	Super VGA
1,024×768	XGA	Extended Graphics Array
1,280×1,024	SXGA	Super XGA
1,600×1,200	UXGA	Ultra XGA

      Refresh Rate: Refresh rate  is defined as  the brightness of the screen. It is defined as the number of times per second that the electron guns scan every pixel on the screen. Refresh is rate measured in Hertz, or cycles in one second. A display device with 100Hz refresh rate means that device refreshing the screen 100 times in one second. Higher the refresh rates higher the quality of computer.

Dot Pitch: This is another critical characteristic of the display device. Dot pitch is the distance between the pixels. It is measured in millimeters. Higher the dot pitch, lesser will be the quality of image. For better quality of image the dot pitch should be less. The display device having dot pitch 0.44mm has lesser picture quality than a device having 0.28 mm dot pitch. Lesser dot pitch should be demanded. On the basis of above characteristics we have following generations of display devices.

A video adapter is hardware mounted on the motherboard expansion slot. Bur first let us get introduces to video adapter, it provides the interface between your computer and your monitor and transmits the signals that appear as images on the display. The quality and standard of video adapter is responsible for the display characteristics i.e. resolution, color depth etc. The following list of standards video adapters belong to different generation:-

·         MDA (Monochrome Display Adapter)

·         HGC (Hercules Graphics Card)

·         CGA (Color Graphics Adapter)

·         EGA (Enhanced Graphics Adapter)

·         VGA (Video Graphics Array)

·         SVGA (Super VGA)

·         XGA (Extended Graphics Array)

·         UVGA (Ultra VGA) SXGA (Super XGA) UXGA (Ultra XGA)

10.2.1.1 CRT Monitor

CRT monitor is an output device that uses Cathode ray Tube to display information. Cathode ray tube is a large vacuum tube mounted with electron gun. CRT monitor consist of vacuum tube enclosed in a glass case.

The back of monitor is equipped with electron gun. The gun shoots electrons through a magnetic coil. This coil is responsible to hit the beam at particular location of the screen. The screen is coated with phosphorus chemical. This chemical has a unique property that it glows when they are struck by charged particles. The charged particles that are electrons hit the area of screen that area of the coated screen illuminated. The coated screen is organized in to grid of dots. Each dot is called Pixel. Each pixel has unique address. Actually, electron gun does not just focus on a spot and shoot electrons at it. It systematically aims at every pixel on the screen. Like human eyes reading, while reading we start reading from the top of the page and read each character group of character sense as a word and group of word sense as a line and group of line sense as a paragraph and this process keeps on till the end of page. Similarly electron gun starts from upper edge of the screen and scan each pixel with electron gun till it reaches the lower edge of the screen.  The intensity of each electron beam is controlled by circuit. On the basis of intensity of beam, monitors are categorized as

·         Monochrome Monitor: This type of monitor display only one color, The beam intensity determine pixel is on (White) or off (black) i.e.  Black and white

·         Grayscale Monitor: Display varying intensities from light gray to black

·         Color monitor: Can display 16 million colors. These monitors have three electron guns. Each gun is responsible to emit the primary color beam that is RED, GREEN, BLUE (RGB). Each Pixel includes three phosphorus particles for RED, Green and Blue beam. The beam of these three guns focus on each particle of pixel, the phosphorus light up. The pixel can have different colors by combining , the various intensity of the three beams.

                       

10.2.1.2 Flat panel Monitor: LCD

An LCD or Liquid crystal display is a type of output device flat panel monitors. LCD is very thin and light in weight as compare to CRT monitors. These flat panel devices widely are used in portable computers. LCD’s are a another generation of monitors, with high resolution and are widely used devices than CRT. Even in stationary PC, they had taken the place of CRT monitors; they take less space on desk and run cooler than traditional CRT monitors. LCD is composed of several layers. Those layers include two polarized panels, with a liquid crystal solution with them. These layers are transparent. Light is passed through these layers and the layer of liquid crystal get charged with various intensity and is colorized and produces image.

 

LCD

The major drawback of LCD is that the image on LCD is difficult to see in bright light. Another major drawback of LCD is viewing angles. An angle from the image on screen is viewed clearly. For a clear visibility of the screen,  you have to sit exactly front of the screen. Technological advancement has extended the viewing angles of LCD. This technological advancement has categories the LCD in two main categories.

The Active matrix Display: This pixel assigns the transistor to each pixel. And each pixel is turned on and off individually in case of monochrome monitor. Three transistors are packed for each pixel for RGB color. This enhancement allows the pixel to be refreshed rapidly. It displays the ‘Thin Film Transistor’ technology (TFT), which employs four transistors for each pixel. Most computer note books and desktop computers are using active-matrix LCD.

 Passive-Matrix Displays: Passive matrix LCD depends on transistors for each row and column of pixels. The number of transistors along the  horizontal and vertical edges determines the resolution of the screen. The color displayed by a pixel is determined by the electricity coming from the transistor. They are inexpensive in matrix and have very narrow viewing angle and also their refresh rate is very low.

Advantages of LCD

• Low power consumption and low cost.
• Small in size
• Light in weight.
• No geometric distortion.

Disadvantages

• LCD does not emit light, so the image has very little contrast
• Display is dependent on viewing angle

10.2.1.3   Flat Panel Monitor: Plasma Display

Plasma display device is visual display which creates an image by causing a series of gas filled cells to get illuminated by means of electric current.  Each cell represents a picture element. It uses neon gas and electrode above and below the gas.  Depending on the color of gases, the color  is displayed. Basically cell holds mixtures of gases. With the flow of current from these gases, the mixture burns up and emits light of different colors. Just like electric tube, tube is filled with gas and when current passes through the tube the gas inside the tube is heated and emits light.  Every pixel is made up of three cells called sub pixels. Each sub pixel has differently colored phosphorus, one sub pixel has red light phosphorus, the other has green light phosphorus and another one has blue light phosphorus. These three colors mix together and create the overall color of the pixel.

Advantages

• Resolution is good
• It has fewer glares.
• There is no flickering
• Images are brighter than CRT
• There is no problem of viewing angle like LCD

Disadvantages

• Uses lot of power as compare to LCD
• Costly and sensitive technology

10.2.1.4 Flat Panel Display: LED

An LED is Light emitting diode. LED display is flat panel display, which uses the matrix of light emitting diodes for video display. They are widely used as a component of a larger display, especially for outdoor display. The first LED flat panel television screen was developed, demonstrated and documented by James P.Mitchell in  1977 (source Wikipedia). It was monochromatic by design. LED has come in to existent to cover a long way. In 2000, LCD took over the high market and replaces the CRT. With the introduction of HD (High Definition) in market, technology moved the trend of market from LCD to LED. LCD uses cold cathode fluorescent tubes to project a white light on to the pixel to make up the screen. But in LED changes that cold cathode fluorescence is replaced with diode devices, the remaining technology is same. LED is also called LED backlit LCD. This is a new generation of LCD. LED is much thinner than LCD TV and is also energy efficient. They can also provide larger color range, producing vibrant pictures.  On the basis of technology LED TV is classified into three ways.

·         LED edge Lighting: With this technology, white LED Edge lighting are used to shine across the display. LEDs are formed around the border of the screen, using a special transmission panel to spread the light evenly behind the screen. This technology is commonly used in LED’s, because it provides thinness.

·         RGB LED Backlit set: This is further a improvement of technology to provide improved colors.  It allows Local Dimming. Local dimming is a process by which LED controls the color intensity of each part of the screen locally to create more dynamic pictures.

·         Organic Light emitting diode: This is future technology of LED. This technology emerges from organic light emitting diode. The organic material used to create semiconductors, which allows bendable light and displays the image. With this technology you can wrap your TV like poster and can carry it with you any where.

         

10.2.2 Audio output devices

10.2.2.1 Sound cards

A sound card is internal expansion device fitted into the motherboard expansion slot and is responsible to process the audio signals to and from the computer under the control of computer program. This provides the internal face between the external devices and to control the audio devices through computer programs. Sound cards are typically used to provide the audio facilities for multimedia applications like video editing, sound engineering, presentation, composition of music and educations. Some sound cards are mounted on motherboard on expansion slot of the motherboard and others may plug in through USB port. Digital sound reproduction is usually done with multichannel DACs, which are capable of simultaneous and digital samples at different pitches and volumes.  Most sound cards have line in connector to input signals from sound source. The sound card converts this sound signal into digital one to store into secondary storage device.  A sound card actually has both input and output functions. If anyone wants to use computer microphone to record voice, the microphone can be connected to computer through input jack. Other input devices that can be connected to the sound card are CD Rom, DVD drive etc. To play back audio, the sound card reverses the process. That is, it translates digital sound into the electric currents  that are sent to the speakers, which  are connected to the card on output jack of card. With appropriate software, we can do much more than simply record and play back digitized sound. Sound editing program allow you to view the sound wave and edit it. You can cut bits of sound copy them and amplify the part and can create exotic sounds.

10.2.2.2 Speakers

Speaker is  most commonly and widely used sound output device used along with computer.  Sound card generates very small non amplified sound signals. You need external amplification of the sound signals. This amplification is done by speakers.  Conventional speakers were large and generate the magnetic interference with computer screen.  Small sized speakers are needed with computers, they should also have with magnetic shielding in the form insulation is to nullify the electronic distortion.  Audio adapter is responsible to prove the quality to speakers. 16-bits audio adapter is more powerful than 8 bit audio adapter and provides better quality to speakers.  Human hearing range is 20Hz -20,000 Hz. of sound wave. No system generates this range perfectly.  A very good quality might cover 30Hz – 2300Hz of frequency. The quality of speakers also depends upon the harmonic Distortion. It is the distortion generated by the speaker during amplifying process. Harmonic distortion is the sound send to the speaker and sound generated by the speaker. This distortion is measured in percentages. An acceptable level of distortion is 1%. The commonly audio system available today is stereo, which uses two speakers placed to overlie sound.  Four points surround sound uses four speakers plus a subwoofer to surround sound effects; the four speakers are placed around the listener, and the subwoofer is usually placed near a wall. Surround sound, also referred to as Dolby Digital or DTS Surround sound, uses five speakers plus a subwoofer. The fifth speaker is placed between the front two speakers to fill in any missing sound caused by incorrect speaker.

10.2.2.3 Headphones and Earphones

Many computer users prefer listening to audio through headphones and headset, rather than speakers. These devices are helpful when using a portable computer, which do not have very high quality speakers, or when playing audio might disturb other people. Headphones include a pair of speakers which are attached to an adjustable strap that can be fitted to head. Today, we have inexpensive, high quality, light weight and comfortable to wear speakers in market.  So Earphones, headphones are hardware device that can plug into computer (line out) or speakers and allow private listening to audio without disturbing anyone else. It is like small speakers on ears.  Some headset includes one or two speakers and a microphone, all mounted to an adjustable head strap. The headset microphone plugs into the sound card’s microphone input and the speakers connect to the sound card’s speakers jack. Headset replaces both remote microphones and speakers and is useful for speech recognition applications, or when using computer to make phone calls or participate in videoconferences.

10.2.3 Other Types of Display devices

• Paper white display: These devices are some times used by document designer such as desktop publishing specialists, newspaper or magazine publisher to provide high quality printed document.  It provides high contrast between the monitor’s white background and displayed text graphics, which usually appear in black. An LCD version of paper white display is called a page-white display.

• Electronic Paper Display (EPD):  Electronic paper display (EPD) is a technology that uses an electrically-charged surface giving  the look and feel of ink on paper. EPDs are very thin and need power only if a new image is requested. Unlike conventional displays that make use of backlighting technology for illuminating pixels, an EPD uses a scientific phenomenon called electrophoresis, which refers to the motion of electrically-charged molecules within an electrical field. All these circuits form a screen having a calculable resolution. This can be managed by a graphics chip or display driver. EPD is used in e-books, smart card displays, status displays, mobile phones, electronic shelf labels, e-newspapers, wrist watches, etc.

• Data projectors: To get a presentation on big screen data projectors are becoming very common. They are also called Digital light projectors or video projectors. A data projector plugs into one of the computer port and then projects the video output onto an external surface. Any projector can work in either still video mode or full video mode, and can display output like animations or movies etc. New models use Digital Light processing technology to project brighter, crisper images. DLP devices use a special microchip called digital micro mirror device, which actually uses mirrors to control the image display.

10.3 Summary

Computers can communicate information to users in several ways, but most exciting types of output are those that appeal to the senses. It is one thing to read text and information from paper and it is other  to see those things on the screen with sound effects.  Modern technology has improved the display and sound system. We can take output from computer in two ways, by display devices and through sound output devices.  We have different display devices like CRT monitor, LCD, LED and plasma display devices. These devices are using improved technology for better output, reduced the size and  consume less energy. These devices have come in to existence with demand of user and new trends of market. Sound output devices have changed the meaning of sound industry now sound is digitally managed. A new field of engineering has emerged due these devices, which is sound engineering.

10.4 Glossary

·         CRT           Cathode ray tube (monitor)

·         VDU          Video display unit (monitor)

·         LCD         Liquid crystal display – as available on hand held games and potables

·         LED            Light Emitting Diode

·         CRT           Cathode-ray tube

·         AMD         Advanced Micro Devices

·         IP               Internet Protocol

·         DLP           Data Light Processing

·         DTS           Dolby Digital System

·         EDP           Electronic Page Display

·         DAC           Digital Adapter Card

·         TFT            Thin Film Transistors

10.5 Suggested Answer to SAQ

Question: What is Refresh Rate?

Refresh rate  is defined the brightness of the screen. It is defined as the number of times per second that the electron guns scan every pixel on the screen. Refresh rate is measured in Hertz, or cycles in one second. A display device with 100Hz refresh rate means that device refreshing the screen 100 times in one second. Higher the refresh rates higher the quality of computer.

Question: Explain the term Dot Pitch?

This is another critical characteristic of the display device. Dot pitch is the distance between the pixels. It is measured in millimeters. Higher the dot pitch lesser will be the quality of image. For better quality of image the dot pitch should be less. The display devices having dot pitch 0.44mm has lesser picture quality that a device having 0.28 mm dot pitch. Lesser dot pitch should be demanded.

Question: What are the advantage and disadvantages of LCD?

Advantages of LCD

• Low power consumption and low cost.
• Small in size
• Light in weight.
• No geometric distortion.

Disadvantages

• LCD does not emit light, so the image has very little contrast
• Resolution is poor
• Display is depends on viewing angle

Question: What is VGA?

Video graphics array, this provides graphics resolution of 1024 x 768 pixels and allows 256 colors.

Question: What is SVGA?

Super Video Graphics Array allows 16.7 million color hues and above.

Question: What is difference Active matrix display and passive matrix display?

The Active matrix Display: This pixel assigns the transistor to each pixel. And each pixel is turned on and off individually in case of monochrome monitor. Three transistors are packed for each pixel for RGB color. This enhancement allows the pixel to be refreshed rapidly. It displays the ‘Thin Film Transistor’ technology (TFT), which employs four transistors for each pixel. Most computer note books and desktop computers are using active-matrix LCD.

Passive-Matrix Displays: Passive matrix LCD depends on transistors for each row and column of pixels. The number of transistors along horizontal and vertical edges determines the resolution of the screen. The color displayed by a pixel is determined by the electricity coming from the transistor. They are inexpensive in matrix and have very narrow viewing angle and also their refresh rate is very low.

Question: Classify the LED TV on the basis of technology?

On the basis of technology LED TV is classified as

·         LED edge Lighting: With this technology White LED Edge lighting are used  to shine across the display. LEDs are formed around the border of the screen, using a special transmission panel to spread the light evenly behind the screen. This technology is commonly used in LED’s, because it provides thinness.

·         RGB LED Backlit set: This is further improvement of technology to provide improved colors.  It allows Local Dimming. Local dimming is a process by which LED controls the color intensity of each part of the screen locally to create more dynamic picture.

·         Organic Light emitting diode: This is the future technology of LED. This technology emerges from organic light emitting diode. The Organic material is used to create semiconductor, which allows bendable light and displays. With this technology, you can wrap your TV like poster and can carry it with you any where.

Question: What is Electronic paper display?

Electronic paper display (EPD) is a technology that uses an electrically-charged surface giving the look and feel of ink on paper. EPDs are very thin and need power only if a new image is requested. Unlike conventional displays that make use of backlighting technology for illuminating pixels. An EPD uses a scientific phenomenon called electrophoresis, which refers to the motion of electrically-charged molecules within an electrical field. All these circuits form a screen having a calculable resolution. This can be managed by a graphics chip or display driver. EPD is used in e-books, smart card displays, status displays, mobile phones, electronic shelf labels, e-newspapers, wrist watches, etc.

10.6 References/Bibliography

• Introduction to Computers, Peter Nortron, Tata Mc-graw Hill Publishing company Limited.
• Computer Fundamentals, P.K Sinha, BPB Publications
• Introduction to Computers  By Gary Shelly, Steven Freund, Misty Vermaat, Published ByShelly Cashman Series
• Introduction  to computer by Raj Mohan Joshi, Published by Isha Books, New Delhi
• Introduction to Computer Science , by ITL Education Solutions Limited, Published Pearson education ltd.

10.7 Suggested readings

·         Handbook of Visual Display Technology

Chen, Janglin, Cranton, Wayne, Fihn, Mark (Eds.) 2012

·         Computer Graphics: Systems and Applications

Editor-in-chief: Encarnacao, Jose Luis 2012

·         New Perspectives on Computer Concepts 2014: Comprehensive

 By June Jamrich Parsons, Dan Oja

·         Computer-based Instruction: Design and Development

 By Andrew S. Gibbons, Peter G. Fairweather

·         Computer Graphics: Principles and Practice

 Edited by James D. Foley

10.8 Model Questions

·         How CRT Works?

·         What is the difference between LCD and Plasma TV?

·         What is Resolution?

·         What is difference between LED and LCD TV?

·         Explain the main technological characteristics of speakers?

·         Write about Active-Passive Matrix Displays?

·         Explain the functioning of data projectors?

·         Explain the functioning of sound card?