Input and Output UNIT 4 INPUT OUTPUT DEVICES Devices Structure Page No. 4.0 Introduction 76 4.1 Objectives 76 4.2 Input Output Devices 76 4.3 What is a Port ? 78 4.3.1 Parallel Port 78 4.3.2 Serial Port 79 4.3.3 Universal Serial Bus (USB) 79 4.3.4 Small Computer System Interface (SCSI) Port 79 4.4 Input Devices 80 4.4.1 Keyboard 80 4.4.2 Mouse 81 4.4.3 Digitizing (Graphic) Tablet 82 4.4.4 Trackball 82 4.4.5 Joystick 83 4.5 Pick Devices 84 4.5.1 Light Pens 84 4.5.2 Touch Screens 84 4.6 Source Data Entry Devices 85 4.6.1 Digital Camera 85 4.6.2 Scanner 86 4.6.3 Optical Mark Reader (OMR) 86 4.6.4 Magnetic Ink Character Reader (MICR) 87 4.6.5 Bar-Code Reader 87 4.6.6 Magnetic Stripe Reader 87 4.7 Output Devices 88 4.7.1 CRT Monitor 88 4.7.2 LCD Monitor 89 4.7.3 Thin Film Transistor Liquid Crystal Display (TFT LCD) 90 4.7.4 LED Monitor 90 4.7.5 Projection Displays 90 4.7.6 Printers 93 4.7.7 Plotters 97 4.7.8 Speaker and Microphones 97 4.8 Summary 99 4.9 Answers to Check Your Progress 100 4.10 Further Readings 103 75 Basics of Computer Hardware 4.0 INTRODUCTION In the previous unit, we have discussed the history of computer systems and methods to store data in computers. In this unit we shall discuss something about input/output devices and their functions. Input/output devices constitute a major part of a computer system. These are also called peripheral devices. Without I/O devices, a user cannot communicate with the computer. They are required to enter data and instructions in a computer so that the computer can process that data and provide the result to the user through output devices. In computer, inputs are the signals and data received by the system and outputs are the signals and data which are generated from the system. First we will discuss briefly about input/output devices and then move on to the function and structure of input and output devices. And finally, we will discuss about recent trends in input devices such as digital camera, barcode reader, magnetic ink character recognition and magnetic stripe reader such as ATM machines and Electronic Point of Sale (EPOS). 4.1 OBJECTIVES After studying this unit you should be able to understand: the basic concepts of input/output devices; functions of input/output devices; types of input/output devices; types of Ports; types of monitors, printers, scanners and graphics tablet; and newer technologies in computer hardware. 4.2 INPUT OUTPUT (I/O) DEVICES Inputs are data The computer will be of no use if it is not communicating with the external world. Thus, or signals a computer must have a system to receive information from the outside world and must received by the be able to communicate results to the external world. Thus, a computer consists of computer system. An Input input/output devices. Input and output devices can also be written as I/O devices. unit takes the input and converts it into Input and output devices of a computer system are the devices that connect you to binary form, so computer. Input devices let you to transfer data and user command into the computer that it can be system. I/O devices are used to interact with the computer system. For example, you can understood by the computer type in data by using a keyboard, or you can input data in picture form by using a scanner in computer system. 76 On the other hand, output devices display the result of input data or signals after Input and Output Devices processing it. Examples of these could be your computer’s monitor, which displays all the programs which are running on the computer, as well as the printer, which will print out a hard copy of the information which is saved in your computer. Input and output devices allow the computer system to interact with the outside world by moving data into and out of the computer system. Examples of some input devices are: Keyboard Mouse Joystick Microphone Bar code reader Graphics tablet Pen drive CD/DVD Digital Camera An output device is used to send data out of the system. The user sees the result after processing of data by the computer through output devices. Examples of some output devices are: Monitor Printer Plotter Speaker Input and output devices are also called I/O devices. They are directly connected to an electronic module called I/O module or device controller. For example, the speakers of a multimedia computer system are directly connected to a device controller called an audio card, which in turn is connected to the rest of the system. Input and output devices are similar in operation but perform opposite functions. It is through the use of these devices that the computer is able to communicate with the outside world. Input data for the computer system could be in any of the following forms : Manual inputs from a keyboard or console. Analog inputs from instruments or sensors. Inputs from a storage device, such as pen-drive, CD’s and Floppy Drives. The speed of a processor is far more than the input devices, such as the keyboard of computer system. Computer systems can process hundreds or thousands of computer words or characters per second. Thus, a study of the first method, i.e. manual input 77 Basics of Computer reflects the inability of human-operated keyboards or keypunches to supply data at a Hardware speed that matches the speed of digital computers. Check Your Progress - 1 Part I: State True/False 1) Keyboard is an input device. True / False 2) Monitor is an input device. True / False 3) Printer is an input device. True / False 4) Graphic Tablet is an input device. True / False 5) Joy-stick is an output device. True / False 6) Speaker is an output device. True / False 7) Microphone is an input device. True / False Part II: Short answer type questions 1) What do you mean by input devices? …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. 2) What do you mean by output devices? …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. 3) Name some input and output devices. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. 4.3 WHAT IS PORT ? I/O ports are the Port is a connecting socket, outside the system into which different types of cables are interfaces through plugged. It is a specific place from which other devices can be physically connected. I/O which computers ports are the interfaces through which computers communicate with external devices communicate with external devices such as such as printers, modems, joysticks and terminals. There are many types of ports used in printers, modems, computer system. Some of them are given as follows. joysticks and terminals 4.3.1 Parallel Port Various peripherals can be connected through parallel port, which is a parallel communication physical interface. A parallel port transmits 8 bits of a byte of data in parallel. It is used for transmitting fast data over short distances. It is used to connect a printer to a computer. Since a parallel port transmits an entire byte at a time, it operates 78 I/O devices at a relatively high speed. A Parallel port is primarily used to connect printers Input and Output Devices to a computer and hence it is often called a printer port. Figure 4.1: Parallel Port 4.3.2 Serial Port Serial port transmits one bit of a byte, one at a time as a single stream of bits. It is meant for transmitting slow data over long distances. Communication over a phone is an example of serial communication. It is a serial communication physical interface which transmits one bit at a time. Dial-up modems and serial mice use serial ports. Figure 4.2: Serial Port 4.3.3 Universal Serial Bus (USB) A USB Port can connect up to 127 peripheral devices such as a digital camera, digital speakers, scanners, speakers etc. It permits Plug and Play – configuring of expansion cards and peripheral devices as and when they are installed. Figure 4.3: USB 4.3.4 Small Computer System Interface (SCSI) Port SCSI-Small Computer System Interface Port allows data to be transmitted in a daisy chain to up to 7 devices at a speed higher (32 bits at a time) than those possible with serial and parallel ports. It is a fast data transmitting device and is used to connect HDD, CD ROM drives and scanners with the computer system. 79 Basics of Computer Hardware 4.4 INPUT DEVICES In this section we will discuss various types of input devices used for entering data into the computer system. These are: 4.4.1 Keyboard It is the most common input device used for entering data and information into the computer system. This is the standard input device attached to all computers. The keyboard is a primary device for inputting text by pressing a set of keys. All the keys are neatly mounted in a keyboard connected to the computer system. Keyboard devices can be classified into two types general purpose keyboards and special purpose keyboards. General purpose keyboard are standard keyboards used with most computer system. They are called general purpose because that have enough keys to make them useful for any type of application. The layout of keyboard is just like the traditional typewriter of the type QWERTY.