INPUT-OUTPUT DEVICES

Input DevicesAn input device is any hardware component that

allows you to enter data and instructions onto a computer. Most Widely used input devices are

1. Keyboard2. Mouse3. Microphone4. Scanner5. Digital camera 6. Stylus7. Joysticks8. Light Pen

KEYBOARDThe most commonly used input device is the keyboard on which data is entered by manually keying in or typing certain keys. A keyboard typically has 101 or 105 keys.

Keyboard Cont.

The keyboard allows the computer user to enter words, numbers, punctuation, symbols, and special function commands into the computer’s memory.

MOUSEIs a pointing device which is used to control the movement of a mouse pointer on the screen to make selections from the screen. A mouse has one to five buttons. The bottom of the mouse is flat and contains a mechanism that detects movement of the mouse.

Variants of the Mouse - Trackpads• A trackpad is a touch-sensitive pad that provides the same functionality as a mouse.

• To use a trackpad, you glide your finger across its surface.

• Trackpads provide a set of buttons that function like mouse buttons.

Variants of the Mouse - Trackballs• A trackball is like a mouse turned upside-down.

• Use your thumb to move the exposed ball and your fingers to press the buttons.

Many styles of trackball are available.

ScannerScanner is a light sensitive device that helps you copy or capture images, photos, and artwork that exist on paper.

                                                                   

Digital cameraA digital camera can store many more pictures than an ordinary camera. Pictures taken using a digital camera are stored inside its memory and can be transferred to a computer by connecting the camera to it. A digital camera takes pictures by converting the light passing through the lens at the front into a digital image.

MicrophoneMicrophone is a input device

used to input audio to Computer.

• Three main types of microphones are:Desktop microphonesHeadsetsDirectional microphones

                     

          

                                                                   

                     

          

StylusesStylus is an input device consisting of a thin

stick that uses pressure to enter information or to click and point

• Styluses are used with:PDAs Tablet PCsGraphics tablets

                                                                   

Joystick

The main use of a joystick is to play computer games by controlling the way that something moves on the screen.

Light pen•A light pen is a small ‘pen-shaped’ wand, which contains light sensors. •It is used to choose objects or commands on the screen either by pressing it against the surface of the screen or by pressing a small switch on its side. •A signal is sent to the computer, which then works out the light pen’s exact location on the screen. •The advantage of a light pen is that it doesn’t need a special screen or screen coating.

Output Devices An output device is any hardware

component that conveys information to one or more people. Three commonly used output devices are

1.Printer2. Monitor 3. Speakers

Monitors

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.

Cathode-Ray Tube (CRT) Flat- Panel Display

Cathode Ray Tube (CRT) Monitors

A CRT monitor contains millions of tiny red, green, and blue phosphor dots that glow when struck by an electron beam. Electron beam travels across the screen to create a visible image.

In a CRT monitor tube, the cathode is a heated filament.

The heated filament is in a vacuum created inside a glass tube. The electrons are negative and the screen gives a positive charge so the screen glows.

Flat Panel Display - Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, graphics display.

The flat-panel display is divided into two categories: Emissive Displays - The emissive displays are devices

that convert electrical energy into light. Example are plasma panel and LED(Light-Emitting Diodes).

Non-Emissive Displays - The Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. Example is LCD(Liquid-Crystal Device)

Speakers A speaker is a device that

produces computer output as sound. Speakers are common devices in computer systems Examples include:• Built-in speaker• Two-device set speakers• Surround sound speakers

                     

          

                     

          

Printer A printer produces a

paper copy of information generated by a computer.

There are two types of printers:

Impact Printers Non-Impact Printers

Impact PrintersThe impact printers print the characters by striking

them on the ribbon which is then pressed on the paper.

Characteristics of Impact Printers are the following: Very low consumable costs Very noisy Useful for bulk printing due to low cost There is physical contact with the paper to produce

an imageThese printers are of two types Character printers Line printers

Non Impact PrintersNon-impact printers print the characters without

using ribbon. These printers print a complete page at a time so they are also called as Page Printers.

These printers are of two types Laser Printers Inkjet PrintersCharacteristics of Non-impact Printers Faster than impact printers. They are not noisy. High quality. Support many fonts and different character size.