WHAT IS INPUT OUTPUT (I/O) DEVICES
The computer will be of no use if it is not communicating with the external world. Thus, a computer must have a system to receive information from the outside world and must be able to communicate results to the external world. Thus, a computer consists of input/output devices. Input and output devices can also be written as I/O devices.
Input and output devices of a computer system are the devices that connect you to computer. Input devices let you to transfer data and user command into the computer system. I/O devices are used to interact with the computer system. For example, you can type in data by using a keyboard, or you can input data in picture form by using a scanner in computer system.
On the other hand, output devices display the result of input data or signals after 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 reflects the inability of human-operated keyboards or keypunches to supply data at a speed that matches the speed of digital computers.
Check Your Progress
Part I: State True/False
1)
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Keyboard is an input device.
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True / False
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2)
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Monitor is an input device.
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True / False
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3)
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Printer is an input device.
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True / False
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4)
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Graphic Tablet is an input device.
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True / False
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5)
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Joy-stick is an output device.
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True / False
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6)
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Speaker is an output device.
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True / False
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7)
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Microphone is an input device.
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True / False
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(1) True
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(2)
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False
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(3)
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False
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(4)
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True (5) False
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(6) True
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(7)
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True
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Part II: Short answer type questions
1) What do you mean by input devices?
Input devices let you input data and other information into the computer. They are used to give special instructions to the computer so that it will know what to do. Input devices transfer data and user commands into the computer system. Input devices are used to interact with the computer system. Inputs are data or signals received by the computer system.
For example, you can type in data by using a keyboard, or you can input data in picture form by using a scanner.
2) What do you mean by output devices?
Output devices display the result of your computer's computations. Examples of these are your computer's monitor. Output devices are those devices which display the result of input data or signals after processing it. When data is given to the computer to process then the processed data, in form of the desired result, comes out of the system through output devices.
3) Name some input and output devices.
Examples of Input devices are:
Keyboard, Mouse, Joystick, Microphone, Bar code reader and Graphics tablet. Examples of output devices are:
Monitor, Printer, Plotter and Speaker
WHAT IS PORT ?
Port is a connecting socket, outside the system into which different types of cables are plugged. It is a specific place from which other devices can be physically connected. I/O ports are the interfaces through which computers communicate with external devices such as printers, modems, joysticks and terminals. There are many types of ports used in computer system. Some of them are given as follows.
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 I/O devices at a relatively high speed. A Parallel port is primarily used to connect printers to a computer and hence it is often called a printer port.
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.
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.
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.
INPUT DEVICES
In this section we will discuss various types of input devices used for entering data into the computer system. These are:
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. It also contains some extra command keys and function keys. It contains a total of 101 to 104 keys. You have to press a correct combination of keys to input data. The computer can recognize the electrical signals corresponding to the correct key combination and processing is done accordingly.
The User can enter data into the computer by pressing a set of keys on the keyboard. In a keyboard letters are printed on the keys. The first keyboard was developed in the 18th century and was named as a QWERTY keyboard. A Computer keyboard includes control circuitry which converts the key pressed by the user into key codes so that the computer can understand it. Now-a-days wireless keyboards are also being used which increase user freedom. The wireless feature is achieved by infrared signals or by radio frequency.
In general, a computer keyboard has following keys :
1. Alphanumeric Keys: It includes letters and numbers.
2. Punctuation Keys: These include comma, period, semicolon etc. and
3. Special Keys: These can be function keys, control keys, arrow keys and Caps lock keys etc.
All the modern keyboards of computer are classified as:
(a) Original PC keyboard having 84 keys;
(b) Advance Technology (AT) Keyboard having 101-104 keys; and
(c) Multimedia Keyboard having 120 – 140 keys.
Mouse
A Mouse is a handy device which can be moved on a smooth surface to cause the movement of a cursor on the screen. It is a pointing device which is used to input data and information into the computer system by pointing on it. Physically, a mouse contains a small case, held under one of the user's hands with one or more buttons. For GUI-based systems a mouse is an essential pointing-device. The cursor of the mouse moves in the same direction in which the mouse ball rolls.
Its name is derived from its shape, which looks a bit like a mouse, with its connecting wire that one can imagine to be the mouse's tail. A Mouse rolls on a small ball and has two or three buttons on the top. When you roll the mouse across a flat surface on the screen, sensors sense the mouse in the direction of mouse movement. The cursor moves very fast with a mouse giving you more freedom to work in any direction. It is easier and faster to move through a mouse compared to movement using keys.
Types of Mouse
Mouse could be mechanical, optical or cordless types. Further information regarding these types are as follows :
Mechanical Mouse : Mechanical Mouse uses ball for the movement of cursor on the computer screen. When the ball is rolled in any direction, a sensor of the mouse detects it and also moves the mouse pointer in the same direction.
Optical Mouse : Optical Mouse uses Laser rays for the movement of cursor on the computer screen. It is an advanced pointing device. Movement is detected by sensing changes in the reflected light rather than the motion of a rolling sphere.
Cord-Less Mouse : Cord-Less Mouse is battery driven and does not need any wire for the physical connection with the motherboard. It transmits data through infrared or radio signal.
Computer mice are very useful in designing pictures and graphs and computer and video games by multimedia designers. A Mouse pad is required to move the mouse because it provides a smooth surface. However, an optical or laser mouse doesn't require a mouse pad.
Digitizing (Graphic) Tablet
Digitizing or Ggraphics' tablet is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper. These tablets may also be used to capture data of handwritten signatures. Some tablets are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers. These are used by architects, engineers and designers in Computer Aided Design (CAD) for designing purposes, such as buildings, cars, mechanical parts, robots etc. These are also used in Geographical Information System (GPS) for digitizing of maps.
Graphics tablet is most suited for artists and those who want the natural feel of a pen-like object to manipulate the cursor on their screen. Wacom is the most well known manufacturer of graphics tablets, and is incredibly well respected.
Trackball
Trackball is a moveable ball mounted on a stationary device, which can be rotated manually by using fingers. It is also a pointing device. In a trackball, the ball is placed on the top along with buttons which can be rolled with the fingers. These are used in playing video games.
Mouse and mobile phones are equipped with trackballs to navigate addresses as well as play games.
Joystick
Joystick is a remote control device for a computer which is used for playing video games to indicate the position. It has a stick that pivots on a base and is used for controlling the action in video games. The User moves a spherical ball with the help of a stick in the joystick as opposed to the trackball where fingers are used for moving the ball.
Joysticks are also used for controlling machines such as cranes, trucks, underwater unmanned vehicles, flight simulators, industrial robots etc.
The Joystick shown in Figure has a base and a handle for controlling the movement of the cursor on the screen.
Check Your Progress
Part I: True / False
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1)
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Cordless mice are directly connected with computer.
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True / False
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2)
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Mechanical mice use laser rays for movement.
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True / False
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3)
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Mouse is not a pointing device.
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True / False
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4)
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Floppies are used to store data.
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True / False
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5)
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Scanner is used to print documents.
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True / False
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6)
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Printer is used to display pictures.
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True / False
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7)
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Monitor is used to scan pictures.
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True / False
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(1) False (2) False (3) False (4) True (5) False (6) False
(7) False
Part II: Short answer type questions
1) What do you mean by keyboard?
A Keyboard is one of the most important input devices and is used to input data into the computer system. Keyboards contain letters, numbers, function keys, arrow keys and some special keys on it. A User enters data into the computer by pressing a set of keys on the keyboard.
2) What do you mean by mouse and what are its types?
A Computer mouse is an input device. It is used to point on the instructions and
commands are input by clicking on them by it. A mouse has two or three buttons on it and is moved on a mouse pad which gives a smooth surface for its movement. A
Mouse is a very useful input pointing device in a GUI environment.
Different types of mice are: Optical mouse, mechanical mouse, wireless mouse
3) What do you mean by scanners and what are their functions?
A Scanner is an input device which is used to input data in the form of pictures. It optically scans images, printed text, handwriting, or an object, and converts it to a
digital image.
4) What do you mean by joystick and trackballs in a computer system?
A Joystick is a remote control device for a computer which is used for playing video games to indicate position. It has a stick that pivots on a base and is used for controlling the action in video games. A Joystick is an input device of a computer. Joysticks are also used for controlling machines such as cranes, trucks, underwater unmanned vehicles, flight simulators, industrial robots etc.
A Trackball is a moveable ball mounted on a stationary device. It can be rotated manually by using the fingers. It is also used in playing video games. In Modern computers, a Mouse and in mobile phones trackballs are used to navigate addresses as well as play games. These are also used in playing video games.
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