UNIT-1 : INPUT-OUTPUT DEVICES UNIT STRUCTURE 1.1 Learning Objectives 1.2 Introduction 1.3 Input Devices 1.3.1 Keyboard 1.3.2 Mouse 1.3.3 Light Pen 1.3.4 Touchscreen 1.3.5 Scanner 1.3.6 Joystick 1.3.7 Web Camera 1.4 Output Device-1: Monitor 1.4.1 Block Diagram of Monitor 1.4.2 Pixel and Resolution 1.4.3 Basic Overview of CRT and TFT(LCD) monitor 1.5 Output Device-2: Printer 1.6 Let Us Sum Up 1.7 Further Readings 1.8 Answers To Check Your Progress 1.9 Possible Questions 1.1 LEARNING OBJECTIVES After going through the unit you will be able to- • Identify different types of Input devices. • Describe about the different output devices. • Distinguish between different types of monitors. • Describe about the different types of printers. Elements of Computer Hardware 7 m Unit-i Input-Output Devices 1,2 INTRODUCTION This unit basically deals with the different types of input and output devices to a computer. These devices enable us to interact with the computer and get our required job done. In this unit you will learn about the different types of input-output devices and their applications. You will also know about their advantages, working principles and their interfacing with the com puter. 1,3 INPUT DEVICES Input device is an electromechanical device that allows the user to feed information into the computer. It is used for analysis, storage, and to give commands to the computer. An input device captures information in hu man readable form and converts it into computer readable form (binary form).Examples of input devices include the Keyboard, Mouse, Modem, Joystick, Digitizing pen and tablet, microphone. Touch screen. Scanner, camera. 1.3.1 Keyboard It is the main input device used in most of the computer systems. It has letter and number keys, and some function keys and computer specific task keys. That allows the user, to - use an English-like language to issue instructions to an electronic environ ment. It uses a cursor to keep your place on the screen and to let you know where to begin typing. You are! able to input commands, type data into documents. Fig. 1.1 : Original View of a multimedia keyboard (Source:joey, ubuntu-rocks. org) Elements of Computer Hardware Input-Output Devices Unlt-1 compose documents, draw pictures with the use of certain keys, pull down menus, and respond to prompts issued by the computer. The keyboard contains special keys to manipulate the user inter face. When a key is touched, an eiectrical impulse is sent through the device which is picked up by the operating system software, and sent through the computer to be processed. The keyboard operates as a typical typewriter and uses a standard "QWERTY" keyboard. QWERTY is the way the keyboard is set up for typing. If you look at the keyboard under the top number row, you will see that the alphabet top row begins with QWERTY. 1,3,2 Mouse The mouse is a hand heid pointing device that iets you point to and selects items on your screen. It also enables you to move a cursor or pointer on a screen just by moving the mouse over a flat surface. In a PC mouse there are mostly 2-3 buttons. The mouse is included in almost every computer that is sold today. Besides becoming an important input tool, it has provided access to the computer for many individuals with disabilities that might not otherwise have the oppor tunity to use the computer. Types of Mouse; Basically there are three types of mouse, viz.- • Mechanical mouse • Optomecahnical mouse • Optical mouse Fig 1.2: Original view of a mouse (Source: lmgs.tootoo.com) A mechanical mouse consist a rubber or a metal ball under it, free to move in any direction. Mechanical sensors detect the movement of the ball and consequently move the cursor on the screen. Optomechanical mouse is similar to a mechanical mouse, only dif- ' ference is that it uses optical sensors to detect the movement of the Elements of Computer Hardware Unit-1 Input-Output Devices ball. Optical mouse uses a light emitting diode and a photodiode to detect the movement of the mouse. 1.3.3 Light Pen The pen lets you draw on what is cailed a digitizing tablet that mir rors the surface area of the computer screen. The pen can be used as a standard mouse (without wires connected to it) or aiso as a free flowing drawing device. The pen is usefui for drawing since draw ing graphics with a mouse tends to be somewhat difficult. A iight pen basically consists of light sensors. When it touches the digitizing tablet the computer detects the location of its touch and works ac cordingly. 1.3.4 Touch Screen The touch screen lets the user touch the area to be activated by using the finger or hand. A touch screen can detect exactly the place where the screen is touched. It is most useful to people who are not experienced of using computers peripheral devices. The edge of a touch screen emits horizontal and vertical lines that criss-cross the screen. Whenever a finger touches the screen,the beams are inter rupted and detect location of touch. 1.3.5 Scanner It allows a PC to convert a picture or object into digital code that al lows the computer to display and use an image. A scanner's sophi stication is the ability to translate <«( an unlimited number of analog Fig. 1.3: A scanner voltage levels to digital values. The (Sourcexen.wiki2buy. com) 10 Elements of Computer Hardware Input-Output Devices Unit-1 scanner takes the information it sees on a page and converts into code that the computer can use. A picture once scanned can be edited, printed, or used in an application. Scanners can come with specialized software called optical character recognition (OCR). This software can read text as printed or written. The information can then be manipulated in the computer. 1.3.6 Joystick Joysticks are also a type of input device to a computer, it consist of a stick mounted on a base, the stick is movable to left, right, fonvard and backward and when released it comes to the centre again. The cursor on the computer screen moves according to the movements of the joystick. Joysticks are mostly used while playing computer games as it allows the user to move quickly. 1.3.7 Web Camera Web cameras are basically video and image capturing device just like a ordinary video camera or photo graphic camera. Here there is no photo film as in conventional camera. It contains mainly-a lens /^if for focussing, image sensor and / ' some electronic circuitry for digi- tizing the image sensed by the im- V age sensor. They are basically con- ^ nected to the computer through / " ^ \ USB port. The main use of the web- . % cam is in videophone or video conferencing system. Fig. 1.4: Web Camera (Source: www.buymebuyme.com) Now a day, an advanced version of web camera is available which is known as IP camera and these camera can be controlled remotely with the help of LAN/WAN. Elements of Computer Hardware 11 Unit-1 Input-Output Devices CHECK YOUR PROGRESS-1 J. State true or false: (i) Keyboard enables us to enter or type text on a computer. (ii) Mouse is one of the pointing devices. 2. Fill in the Blanks: (i) Light pens have sensors. (ii) Scanner are used for an image. (iii) Web cameras are basically and capturing device, (iv) The edges of a _ emits horizontal and vertical lines that criss-cross the screen, (v) There are basically types of mouse. 14 OUTPUT DEVICE-1: MONITOR The monitor is the common output device mostly used. It can be thought of as a high resolution TV set. The monitor can also determine if the dis play will be color, black and white, or include graphical objects (pictures). The monitor displays text and images (pictures) converted to output from the video adapter. The video adapter is an expansion card that plugs into the motherboard. The adapter changes the instructions from the central processing unit(CPU) into a way that the monitor can understand it. Most computer monitors are based on Cathode Ray Tube(CRT) technol ogy. The basic operation of these tubes is similar to that in television sets. With the widespread use of smaller computers like PDAs and laptops PDA: Personal nowadays, a new type of display screen Liquid Crystal Display(LCD) has Digital Assistant. been used. 1.4.1 Block Diagram of Monitor The following figures shows the block diagram (fig 1.5) of a CRT Monitor and the fig 1.6 shows a typical CRT monitor with cover re moved showing its internal parts. 12 Elements of Computer Hardware Input-Output Devices Unit-1 AUX AUX I AUX COMPOSITE VIDEO 1 I SOURCE j^MONITO^ Lrru I 1 I— I AUX I TDS COMPOSITE VIDEO I DISPLAY CONSOLE I monitor' CATHODE VIDEO 1/2 SELECT VIDEO FILAMENT CONTROL TV BRIGHTNESS MONITOR FUNCTION CONTROL CONTRAST MONITOR COMPOSITE VIDEO PANEL CRT +1&V\+15V' TO ALL V. FUNCTIONS POWER -15V 1, AND TV DISTRI MONITORS BUTION •tSV CONTROL HORIZONTAUVERTICAL BLANK FUNCTION ¥ PANa SWEEP FLYBACK SYNC PULSE GENERATOR FUNCTION HORIZONTAL/VERTICAL YOKE, Fig. 1.5: Block Diagram of CRT Monitor (Source: www.tpub.com) CRT Mounting CRT HV Connector Screw (1 of 4) CRT Neck Board (Covered by Shield) DAG Costing on CRT CRT HV Cable Access Holes for RGB Deflection Yoke Adjustments EC Power Purity/Static Connector Convergence Magnet Rings Mainboard iorizontal Output Transistor (HOT) _ ^ Ferrite Core for Video Cable rpI Supression Mostly Behind Shield (Mostly Behind« i.* j Focus screen (G2) Heat Sink HniA ^vra PnnnprtnrConnector Heat Sink) Control Qgntjoi (porHOT) Fig.