Input & Output Devices

 Keyboard  Mouse  Touchpad  Tracker balls  Joystick  Touch screen  Scanner  Digital Camera  Webcam

 Visual Display Unit (VDU)  Printers  Dot-matrix Printer  Inkjet Printer  Laser Printer

 Plotter  Speakers

Input devices are used to put data & instructions into a computer. There are 2 main types of input device: Direct & Manual.

Direct input devices: -

They can input large amounts of data quickly and accurately without any need for human intervention. Barcode readers and optical mark readers are examples of direct input devices.

Manual Input Devices: -

They are used by people to enter data by hand. The most commonly used input devices are Mouse and the Keyboard.

The Keyboard is the most common type of input device. Ordinary computer keyboards have their keys arranged in a similar way to those on a typewriter. This way of arranging the keys is called QWERTY because of the order in which the keys appear on the first row of letters. This layout was originally designed to separate common letterpairs, in order to prevent nearby type-bars on a manual typewriter jamming the mechanism when typing at speed. Keyboards are now available with different layouts designed help users type more quickly and comfortably. Computer Keyboards also have extra function keys which can carry out different tasks depending on the software The whole CPU being used. inside a Keyboard

A mouse is a pointing device. It is the next most common type of input device after the keyboard. A mouse is moved around by the user on a flat surface next to the computer. When a mouse is moved, a small ball underneath turns, which directs the cursor to move. An increasingly type of mouse is the optical mouse. The distance and direction the mouse has moved is worked out from differences in the pictures by a processor inside the mouse. Information about the movement of the mouse is then sent to the computer as a set of coordinates. An optical mouse also generates a light. A ball mouse An optical

Touch pads & trackballs are the same, they are also types of pointing devices. They are often used instead of mouse on portable computers which are laptops.

A track ball

A touch pad

The main use of joystick is to play computer games by controlling the way that something moves on the screen. Joysticks can be used to control movement from side to side, up and down & diagonally and horizontally. A joystick will have few buttons which can be used to make something happen like making a character in a game jump or attack or defense etc.

A Joystick

Touch screen can detect exactly where on its surface it has been touched. There are several ways in which this can be done. One common type of touch screen uses beams of invisible infra – red light which shine from top to bottom and side to side in front of the screen. The beams of light forms a grid that divides up the screen. Touch screens are used mainly because they are easy to keep clean and re program when changes are to be made. Touch screen

A scanner can be used to input pictures or text into the computer. There are 2 main types of scanners: hand held & flat – bed scanners work by passing a beam of bright light over an image. Data about the amount of light reflected by the different parts of the picture is collected by sensors inside the scanners. This data is used to produce a digital image of the picture that the computer can display on the screen. Once the image/text has been scanned it can be saved and changed using some special software's. Hand Held Scanners

Flat Bed Scanners

A digital camera can store many more pictures than an ordinary camera. The storage depends on the memory space. We can also shoot videos with it. The images & videos can be transferred using a USB to the computer. They are an other common type of digital camera. Webcams can take photographs and capture moving images which can be saved on the computer and can be sent through internet while chatting. The people who are chatting can view each other on

A graphics tablet consists of a flat surface and a stylus(pen), which can be used to produce free hand drawings or trace around shapes. When the stylus touches the surface of the graphics tablet, data about its position is sent to the computer. This data is used to produce on the screen an exact copy of what is being drawn on the surface of the graphics tablet.

Graphics Tablet

A microphone is used to input sound into a computer system. Microphones are often used for voice recognition systems, which convert sounds made by a user into text on the screen or commands the computer can carry out. Systems like this are very useful for people who can’t use ordinary input devices such as mouse and keyboard. As computers become more powerful in the future, voice recognition will be a much more common input method for all computer users.

Microphone

A light pen is a small “pen - shaped” wand which contains light sensors. The light pen 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. This sends a signal to the computer, which then woks out the light pen’s exact location on the screen. The advantage of the light pen is that , unlike a “touch – screen”, it doesn’t needs a special screen or screen coating.

Light Pen

Before an output can be produced by a computer it must have an output device connected to it. The output devices that you are most probably most used to will be the screen (or monitor) and the printer. Another sort of output that you will have experienced when using a computer is sound, which is output through a speaker. In the next slides I am going to describe the main types of devices that are used to get output from a computer.

A visual Display Unit (VDU) or a monitor is an output device that accepts video signal direct from a computer. Monitors can display graphics, text and video. The size of a monitor is measured in inches diagonally across the screen; 15, 17, 19 and 21 inch monitors are the most common sizes. A color monitor can display from 16 to over 1 million different colors. Color monitors are sometimes called RGB monitors because they accept three separate signals – Red, Green and blue.

Visual Display Unit (VDU)

A printer is an output device that produces a printout or hard copy of the output from a computer. There are many types of printer available and which one you choose will depend on how much you want to pay for the printer, the cost of the paper and the ink it uses, what quality of print you want and whether you are going to print just text, graphics, or graphics and text together. The most common types of printer are dot matrix, inkjet and laser printer. The speed of printers can be measured in characters per second (CPS) or pages per minute (PPM), the higher the values are, the faster the printer can produce output.

A dot matrix printer forms characters and graphics on the paper by producing pattern of dots. If you look closely at a print out from a dot matrix printer you will see the tiny dots which make up the printout. The part of the printer which forms the pattern of dots is called the print head. Dot matrix printers are relatively cheap and so is the stationery that they use. The quality of dot matrix printer depends on the pins there in print head. ‘9’ pin print will produce poor print and ‘24’ pin print will produce much good print than the ‘9’ pin print. These printers often make noise.

Dot Matrix Printer & Printout

Inkjet printers work like Dot Matrix printer (the printouts that they produce are made up of patterns of very small Dots) but the printer head has a set of tiny holes rather than pins. As the print head moves across the paper, ink is forced out through the holes to form the image. Inkjet Printers are very quite to operate and can produce good quality printouts of both graphics and text. Relatively cheap color graphics can be printed using a color inkjet.

Inkjet Printer

A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and MFPs, laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor. A laser beam projects an image of the page to be printed onto an electrically charged rotating drum coated with selenium. Laser Printer

A plotter is a vector graphics printing device that connects to a computer. There are two types of main plotters. Those are pen plotters and electrostatic plotters. Pen plotters print by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art, rather than raster graphics as with other printers. Pen plotters can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pens.

Plotter

A speaker, or speaker system is an electro acoustical transducer that converts an electrical signal to sound. The term loudspeaker can refer to individual transducers (known as drivers), or to complete systems consisting of a enclosure incorporating one or more drivers and electrical filter components. Loudspeakers, just as with other electro acoustic transducers, are the most variable elements in an audio system and are responsible for the greatest degree of audible differences between sound systems.

Speaker s