Input and Output Devices | Cyber Olympiad for Class 9 PDF Download

Input Devices

When you work with the computer, you feed your data and instructions through some devices the computer. These devices are called Input devices. Such a device converts data or information into a form that can be understood by the computer. A good input device should provide timely, accurate, and useful data to the main memory of the computer for processing.
The following are the most useful input devices:

Keyboards

A keyboard is a device used to encode data by key depression, which enters information into a computer system. The keyboard converts alphabet and numbers, and other special symbols into electrical signals that the processor can understand and process. These signals are sent to the computer’s CPU.
The following is a list of commonly used keys that have special functions (keep in mind that key functions can change depending on the program you are using):

• Backspace: This key deletes letters backward. 
• Delete: This key deletes letters placed towards the right of the cursor. 
• Shift: This key, when pressed with another key, will perform a secondary function. 
• Spacebar: This key enters a space between words or letters. 
• Tab: This key will indent what you type, or move the text to the right. The default indent is usually ½ inch. 
• Caps Lock: Pressing this key will make every letter you type appear in capital letters. 
• Control (Ctrl): This key, when pressed with another key, performs a shortcut.
• Enter: This key either gives you a new line or executes a command (pressed in a word processing program, it begins a new line). 
• Number Keypad: These are exactly the same as the numbers at the top of the keyboard. it is also called a num pad. some people just find them easier to use in this position. 
• Arrow Keys: Like the mouse, these keys are used to navigate through a document or page.

Mouse

An object used as a pointing and drawing device is called a mouse which usually has a scroll wheel and buttons and is connected to the system unit through a serial port. As the mouse is moved across the flat mouse pad in any direction, it locates the pointer correspondingly on the screen. Then it issues commands using the selection buttons on the mouse. Many portable microcomputers such as laptops use trackballs instead of mice.
Different ways of using the mouse cause specific things to happen on the monitor:

• Click: Pressing and releasing a button. 
• (left) Single-click: Clicking the left button once. 
• (left) Double-click: Clicking the button thee quickly. 
• Right-click: Clicking the right (secondary) button. 
• Middle-click: clicking the scroll button. 
• Drag: Se lecting, pressing and holding a button (left) on the object and moving the object without releasing the mouse.

Touch Screen

A touch screen is a monitor that allows users to interact with a computer system by touching an area of the display screen. The screen is covered with a clear plastic layer that has a matrix of cells. A user touches a graphic button that displays options on the screen. Touch screens are easy to use. Thus, many kiosks use touch screens as input devices.

Light Pen 

A light pen is a light-sensitive pen-like device used by pointing it at the display surface. A user brings the light pen to the desired point on the screen and presses a button, causing it to identify the current location. It is used to select options from a menu or to draw images.

Track Ball 

The trackball is an input device used in a notebook or laptop computer, instead of a mouse. This is a ball that is half inserted into its base and by moving fingers over the ball one can move the pointer on the screen. A trackball requires less space than a mouse. A trackball comes in various shapes like a ball, a button, and a square.

Joystick 
The joystick is also a pointing device used to move the cursor position on the monitor. It is a stick with a ball at both ends. The lower spherical ball moves in a socket. The joystick can be moved in all four directions. It is mainly used in Computer-Aided Designing(CAD) and playing computer games.

Digitizer Tablet  
It is also called a graphics tablet or just a digitizer. The digitizer is a tablet used to sketch new images or trace old photographs. The user uses a pen-like device called a cursor to draw images. Designers and architects usually use digitizers. The light pen and digitizer technologies are used for pen-based computing. It converts analog data to digital information.
Scanner
A scanner is a device that reads spatial patterns such as images, graphics, and texts, and then generates digital signals of that pattern. The digital format of the data may be processed by a computer, stored on a disk, printed by a printer, or displayed on a monitor. Scanners are commonly used to capture graphic images that can then be placed on a page or on any document. Scanners usually include optical character recognition (OCR) software so that they can read and capture texts directly through optical scanning.

Bar Code Readers 
A bar code is a specialized code represented by sets of parallel bars of varying thickness and separation. This is used for the fast identification of items with an optical scanner. The optical scanner is called a bar code reader. The bar code reader is a photoelectric scanner that reads the bar code image converts it into an alphanumeric value which is then fed to the computer.
Magnetic Data Entry 
There are two technologies in magnetic data entry. A magnetic ink character recognition (MICR) technology reads iron oxide ink preprinted or encoded on checks, deposit slips, or documents. A MICR reader electronically captures data, by first magnetizing the magnetic ink characters and then sensing the signal. Another form of magnetic data entry is the magnetic strip technology that makes computers read credit cards. The dark magnetic stripe on the back of the credit card is the iron oxide coating. A magnetic stripe reader reads this magnetic strip. The main advantage of MICR is that it is less error-prone.
Microphone 
A microphone is an acoustic-to-electric transducer or sensor and is used to convert sound signals into electrical signals. It was originally invented by Emile Berliner in 1877 and allows the user to record voices or sounds and place them on computers, generally as a wave file. To connect a microphone, one has to insert its plug into the back of a computer system (generally written as mic next to it). Integrated microphones can be found on laptops and in some desktop monitors. These microphones usually look like a small hole in front of the computer which when spoken into will record your voice.
Optical Character Reader(OCR) 
OCR is an input device used to read printed text. OCR scans text character by character optically, converts them into a machine readable code, and stores the text in the memory of the computer.

Output Devices 

Output devices of a computer are types of peripheral hardware connected to the computer either using cables or over a wireless network. An output given by the computer can be in the form of a display on the screen or a printed document or a sound that is played. Whether you have desktop computers, laptop computers, or supercomputers, you will require at least one output device.
The following are some output devices.
Monitor 
A monitor is also called Video Display Terminal (VDT) on the Visual Display Unit (VDU). The user can view the visual display of the processed data on the monitor. Computer monitors come in a variety of screen sizes and visual resolutions. All monitors have a video card that processes the data into images, to be eventually displayed. Cathode Ray Tube (CRT) and flat panel display monitors are of two types. CRTs are cheaper and have a good viewing angle. They are also bulkier and consume more power. On the other hand, the flat panel displays have no magnetic interference and are lighter. They are also costlier.
Visual Display Unit (VDU) 
A computer display is also called a display screen or video display terminal (VDT) or Visual Display Unit. A monitor is a screen used to display the output. Images are represented on monitors by individual dots called pixels. The density of the dots determines the clarity of images or their resolution.
Characteristics of (VDU)
Screen resolution: This is the degree of sharpness of a displayed character or image. The screen resolution is usually expressed as the number of columns by the number of rows. A 1024×768 resolution means that it has 1024 dots in a line and 768 lines. A smaller screen looks sharper on the same resolution. Another measure of display resolution is a dot pitch.
Interlaced/Non-interlaced: An interlaced technique refreshes the lines of the screen by exposing all odd lines first, followed by all even lines. A non-interlaced technology that is developed later refreshes all the lines on the screen from top to bottom. The non-interlaced method gives a more stable video display than the interlaced method. It also requires twice as much signal information as interlaced technology.
There are two forms of display: Cathode-Ray Tubes (CRTs) and Flat-Panel Displays.
Cathode Ray Tubes (CRT): A CRT is a vacuum tube used as a display screen. Although CRT means only a tube, it usually refers to all monitors. IBM and IBM compatible microcomputers operate in two modes unlike Macintosh-based entirely on graphics mode. They are a text mode and a graphics mode. Application programs switch computers into appropriate display mode The content of the CRT display is made up of pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form the whole character. Most screens display 80 characters of data lines horizontally and 25 lines vertically.
There are some disadvantages of CRT:

• They are large in size. 
• They have high power consumption.

Flat Panel Displays: Portable computers such as a laptop use flat panel displays because they are more compact and consume less power than CRTs. Portable computers use several kinds of flat panel screens.
Their display screens are smaller in size, weigh less, and consume less power than the CRT monitors. Some of the uses of these flat monitors are found in calculators, video games, monitors, laptop computers, graphics displays.
The flat-panel display is divided into two categories:

• Emissive Displays: The emissive displays convert electrical energy into light. Examples are plasma panels and LED(Light-Emitting Diodes). 
• Non-Emissive Displays: The non-emissive displays convert optical effects to convert sunlight or light from some other source into graphics patterns. An example is an LCD(Liquid-Crystal Device)
  (i) Liquid-Crystal Displays (LCDs): A display technology that creates characters by means of reflected light and is commonly used in digital watches and laptop computers. LCDs replaced LEDs (light-emitting diodes) because LCDs consume less power
  (ii) Display (LED): A flat panel display technology that actively emits light at each pixel when it is electronically charged. This provides a sharp, clear image and wide viewing angle.
  (iii) Gas Plasma Displays: This is also called a gas panel or a plasma panel and is another flat-screen technology. A plasma panel contains a grid of electrodes in a flat, gas-filled panel. The image can persist for a long time without refreshing in this panel. The disadvantages of the gas plasma displays are that they must use AC power and are not capable of showing sharp contrast.

Printer

A printer is an external hardware device, which takes processed data from the computer to generate a hard copy of the same. After the monitors, printers are the most used output devices and they are commonly used to print text data, images, etc. There are three main types of computer printers, namely inkjet, laser, and dot-matrix printers. The dot matrix printer is an impact printer. which uses striking pins against a ribbon to produce the characters in order to print the data. The inkjet printer uses magnetized plates that spray ink on the paper to produce the data. On the other hand, laser printers use a laser beam to produce the data.
A printer is an output device that produces a hard copy of the data. The resolution of printer output is expressed as DPI. Printers can be classified into different categories First, the printers can be divided into three categories on the basis of the way they print.

• Serial Printers: It is also called a character printer which prints a single character at a time. They are usually inexpensive and slow. 
• Line Printer: It prints a line at a time. They are expensive and very fast. Line printers use a band, a chain, etc. 
• Page Printer: It is also called a laser printer. It prints a page at a time, uses a laser to produce page images. The pitching quality of the computer is the best. This is a little bit expensive, but the price of the personal laser printer is decreasing. The price range of the personal laser printer is around $ 400, today.
  Printers can also be classified into two categories according to the use of a hammer. 
• Impact Printers: A hammer hits ribbons, papers, or print head. Dot-matrix and daisy-wheel printers are examples sot impact printers.
• Characteristics of impact printers are the following:
  (i) Very low consumable costs
  (ii) Very noisy
  (iii) Useful for bulk printing due to low cost
  (iv) There is physical contact with the paper to produce an image.
• Non-impact Printers: They do not have the hammer and do not hit on the ribbons. An example is an ink-jet and laser printer. Another classification can be made on the basis of the way they form characters.
• Bit-Mapped Printers: Images are formed from groups of dots and can be placed anywhere on the page. They have many printing options and good printing quality. They use PostScript as a standard language for instructing a microcomputer.

Character-based Printers: Printers print characters into the lines and columns of a page. These printers use a predefined set of characters and are restricted in the position of characters.
Microcomputers use five kinds of printers. They are:

• Daisy-Wheel Printer: Daisy-Wheel is a printer mechanism that uses any kind of hub (wheel) having a set of spokes at the margin of the hub. The wheel can be removed to use a different character set. At the end of each spoke is a raised image of a type character. When the wheel is turned and the required character is aligned to the print hammer, the character is then struck onto a ribbon and onto a paper with the hammer.
  Daisy-Wheel printer prints typewriter-like very high-quality characters. However, they are slower and less reliable. They are used in offices that require few letters to be sent with very high-quality users of microcomputers seldom use this printer because the better dot-matrix printers and inexpensive laser printers are available today.
• Chain Printer: A chain printer uses a printing mechanism that uses character typefaces linked together in a chain. A standard character set may have 48,64 on 69 characters. The chain spins horizontally around a set of hammers aligned with each position. When the required character is in front of the selected print position, the hammer in that position hits the paper into the ribbon against the character in the chain.
• Dot-Matrix Printer: Dot-matrix printers are printers that write characters and form graphic images using one or two columns of tiny dots on a print head. The dot hammer moving serially across the paper strikes an inked ribbon and creates images on paper. Dot-matrix printers are popular printers used with microcomputers because these printers are highly reliable and inexpensive. They are used for tasks where a high-quality image is not essential.

Disadvantages of this printer are

• Slow speed 
• Poor quality

lnk-Jet Printer: It is a printer mechanism that sprays one or more colors of ink at high speed onto the paper and produces high-quality printing. This printer also produces color printing as well as high-quality images. That is, ink-jet printers can be used for a variety of color printing at a relatively low cost. Ink-jet printing has two methods: The continuous stream method and the drop-on-demand method.

Laser Printer: A laser printer is a printer that uses the electro-photographic method used in a copy machine. The printer uses a laser beam light source to create images on a photographic drum. Then the images on the drum are treated with a magnetically charged toner and then are transferred onto a paper. A heat source is usually applied to make the images adhere.

Advantages of a laser printer are:

• Very high-quality output 
• High-quality graphics 
• Supports many fonts and different characters size 
• Very high speed.

Disadvantages of hares printer are:

• Expires 
• Cannot produce multiple copies in a single printing

Speaker

A speaker is a hardware device, which is connected to a computer’s sound card, which outputs the sound generated by the card. Audio data generated by the computer is sent to the audio card that is located in the expansion slot. The card translates the data into audio signals, which are then sent to either the speakers or the headphones. In the initial phase, computers had onboard speakers, which generated a series of different tones and beeps. When multimedia and computer games become popular, better quality speakers known for higher quality sound effects and music came into the market.

Projector

It is a hardware device with which an image and text are projected onto a flat screen. Image data is sent to the video card by the computer which is then translated into a video image and sent to the projector. A projector is often used in meetings to make presentations as it allows the display to be visible to a larger audience. The two types of projectors available in the market today are. Ceiling mount projector and table mount projector.

Plotter 

Plotters, like printers, create a hard copy of a digitally rendered design. The design is sent to a plotter through a graphics card and the image is created using a pen. In simple words, plotters basically draw an image using a series of straight lines. A drum plotter uses a drum, on which the paper gets wrapped. The plotter pen moves across the drum to produce plots. The other type of plotter is the flatbed plotter. The paper is placed on the bed and graphics are drawn on it. This kind of plotter is used for larger drawings.

Braille Embosser/Display

It is an impact printer that prints Braille output by punching dots on the paper. Before printing, the data should be first translated into Braille by using Braille translation software. Braille Display is an alternative for a monitor. This device displays the output Braille characters by raising nylon or metal pins on a flat surface. The data that is highlighted on the computer screen will automatically be displayed on the device by converting the text to Braille.