Set-3
- input-output devices (abbreviated I/o devices) provide the capability to a computer system to communicate with its external environment (its users)they are also known as peripheral devices
- An input device is an electromechanical device that accepts data from outside world and translate them into a form a computer can interpret
- keyboard devices are the most commonly used input devices today they allow data entry into a computer system by pressing a set of keys (labeled buttons) mounted on a keyboard
- A graphical user interface (GUI) provides a screen with graphic icons (small images on the screen ) or menus and allows a user to make rapid selections from them to give instructions to a computer
- point-and -draw devices are input devices used to rapidly point to and select a graphic icon or menu item from multiple options displayed on a screen many of these devices are also useful for effectively creating graphic elements on the screen such as lines curves and freehand shapes some commonly used point and draw devices are mouse trackball joystick electronic pen and touch screen
- data scanning devices are input devices that allow data entry from source documents directly some of them are also capable of recognizing marks or characters
- An image scanner is an input device that translates paper documents into an electronic format for input to a computer input documents may be typed text pictures graphics or even handwritten material image scanners use optical technology for converting an image into electronic form
- An optical character recognition (OCR) device is a scanner equipped with character recognition software users use it for inputting text documents and storing them in a form suitable for doing word processing that is a computer can interpret a document stored in this manner as letters numbers and special characters
- An optical mark reader (OMR) is a scanner which can recognize a pre-specified type of mark made by pencil or pen we can use OMR device for any input data that is of a choice or selection nature
- Bar codes represent alphanumeric data by a combination of adjacent vertical lines (bars) by varying their width and spacing between them A bar-code reader is a device for reading (decoding) bar-coded data
- banking industry uses magnetic-ink character recognition (MICR) technology for faster processing of large volume of cheques besides enabling faster processing of cheques this technology also ensures greater accuracy of data entry because of mostly pre-printed information on the cheque and direct feeding of the cheques to the computer
- A digitizer is an input device used for converting (digitizing) pictures maps and drawings into digital form for input to computers this enables re-creation of the drawing from stored information and easy incorporation of change in the drawing whenever required
- electronic cards are small plastic cards having encoded data appropriate for the application for which they are used an electronic card reader normally connected to a computer reads the data encoded on an electronic card and transfers it to the computer for further processing
- Speech recognition devices are input devices that allow a person to input data to a computer system by speaking to it
- A vision input system allows a computer to accept input by seeing an object input data in this case is normally an object’s shape and features in the form of an image
- An output device is an electromechanical device that accepts data from a computer and translate them into a form suitable for use by outside world (users)
- computer output generated by output devices are of two types soft copy output and hard copy output soft copy output is temporary in nature because it does not appear on a paper or some material that a user can carry for showing to others or for filing and use later when he/she is not using a computer hard copy output is permanent in nature because it appears on a paper or some material that a user can carry for showing to others or for filing and use later when he/she is not using a computer
- monitors are the most popular soft-copy output device used today they display output on a television like screen
- a monitor is associated usually with a keyboard and together they form a video display terminal (VDT) often referred to as just terminal A terminal serves as both an input and output device it is the most popular input/output (I/O) device used today
- printers are the most popular hard copy output devices used today based on the printing technology used we classify printers as dot matrix printers inkjet printers drum printers chain band printers and laser printers according to printing approach that a y printers as impact printers and non-impact printers
- dot matrix printers are character printers that form characters images as patterns of dots
- inkjet printers are character printers that form characters and images by spraying small drops of ink on paper
- drum printers are line printers that print characters by striking a set of hammers on an inked ribbon and paper placed against a solid cylindrical drum with characters embossed on its surface in the form of circular bands
- chain/band printers are line printers that print characters by striking a set of hammers on an inked ribbon and paper placed against a metallic chain/band on which all characters of the character set supported by the printer are embossed
- laser printers are page printers that produce high quality output by forming characters and images with tiny ink particles
- A plotter is an ideal output device for architects engineers city planners and others who need to generate high precision hard copy graphic output of varying sizes two types of plotters in common use are drum plotter and flatbed plotter
- screen image projector is an output device which is used to project information from a computer on a large screen (such as a cloth screen or wall) so that a group of people can view it simultaneously
- A voice response system enables a computer to talk to a user two types of voice response systems are voice reproduction system and speech synthesizer a voice reproduction system produces audio output by selecting an audio output from a set of pre recorded audio response on the other hand a speech synthesizer converts text information into spoken sentences