To be useful, a computer system needs to communicate with its external environment. The input-output devices provide the capability to a computer system. They are also known as peripheral devices because they surround a computer’s CPU and memory.
Input devices are used to enter data from outside world into primary storage, and output devices supply the results of processing from primary storage to users. A wide variety of I/O devices is now available.
For a particular application, one type may be more suitable than another type. Some devices are used for both input and output functions. It is important to note that the speed of I/O devices is very slow as compared to the speed of primary storage and CPU. This is because their speed in most cases depends on the movement of mechanical parts, and the potential for improvement in speed of such parts is limited. It is therefore, difficult to produce I/O devices that can match processor and memory speeds, and there is a constant demand for faster and faster I/O devices.
- [#1] – Introduction to Computer Fundamentals
- [#2] – Basic computer organization
- [#3] – Number systems
- [#4] – Computer Codes
- [#5] – Computer Arithmetic
- [#6] – Processor and Memory
- [#7] – Secondary Storage Devices
- [#8] – Input-Output Devices
- [#9] – Computer software
- [#10] – Planning the Computer Program
- [#11] – Computer Languages
- [#12] – System Implementation and Operation
- [#13] – Operating Systems
- [#14] – Application Software packages
- [#15] – Business Data Processing
- [#16] – Data Communications and Computer Networks
- [#17] – The Internet
- [#18] – Multimedia
- [#19] – Classification of Computers
- [#20] – Introduction to C Programming Language
Points To Remember:
- 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 translates them into a form a computer can interpret.
- An output device is an electromechanical device that accepts data from a computer and translates them into a form suitable for use by outside world (users).
- 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) neatly mounted on a keyboard connected to the computer system.
- 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 can also be used effectively to create 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 used for direct data entry into a computer system from source documents. 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 that can be stored in a computer. Input documents may be typed text, pictures, graphics, or even handwritten material.
- An optical character recognition (OCR) device is a scanner equipped with character recognition software. It is used for inputting text documents and storing them in a form suitable for doing word processing of the documents. That is, a computer can interpret the stored document as letters, numbers, and special characters.
- An optical mark reader (OMR) is a scanner capable of recognizing a pre-specified type of mark made by pencil or pen. Any input data of a choice or selection nature can be recorded for OMR input.
- Bar codes represent alphanumeric data by a combination of adjacent vertical lines (called bars) by varying their width and spacing between them. A bar-code reader is a scanner used for reading (decoding) bar-coded data.
- Magnetic-ink character recognition (MICR) technology is used by banking industry for faster processing of large volume of cheques. This technology also ensures accuracy of data entry because most of the information is pre-printed on the cheque and is fed to a computer directly.
- A digitizer is an input device used for converting (digitizing) pictures, maps, and drawings into digital form for storage in computers. This enables recreation of the drawing from stored information and easy incorporation of changes 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 is normally connected to a computer and is used to read data encoded on an electronic card and transfer it to a 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.
- Computer output generated by output devices are of two types – soft-copy output and hard-copy output. Soft-copy outputs are temporary in nature and vanish after use. Hard-copy outputs are permanent in nature and can be kept in paper files or can be looked later when the person is not using a computer.
- Monitors are the most popular output device used today for producing soft-copy output. They display the generated output on a televisions like screen.
- A monitor and a keyboard are usually associated together to 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 with today’s computers.
- Printers are the most popular output devices used today for producing hard-copy output.
- Dot-matrix printers are character printers that form characters and all kinds of images as patterns of dots.
- Inkjet printers are character printers that form characters and all kinds of images as 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 very high quality output by forming characters and all kinds of images with very tiny ink particles.
- Plotters are an ideal output device for architects, engineers, city planners, and others who need to generate high-precision, hard-copy graphic output of widely varying sizes. Two commonly used types of plotters are drum plotter and flatbed plotter.
- Screen image projector is an output device used to project information from a computer on to a large screen (such as cloth screen or wall) so that a group of people can view it simultaneously.
- Voice response systems enable computers to talk to their users. They are of two types- voice reproduction system and speech synthesizer. A voice reproduction system produces audio output by selecting an appropriate audio output from a set of pre-recorded audio responses. On the other hand, a speech synthesizer converts text information into spoken sentences.
List of Questions
- Why I/O devices are necessary for a computer system?
- What are peripheral devices? Why they are so called?
- Differentiate between an input and output device. Can a device be used as both an input and output device? if no, explain why. If yes, give an example of such a device.
- Why I/O devices are very slow as compared to the speed of primary storage and CPU?
- What is an input device? Name some commonly used input devices.
- What are keyboard devices?
- What are point-and-draw devices? Name some commonly used point-and-draw devices.
- What is a mouse? Explain how it is used to notify the system of a particular user choice out of a given set of choices on a monitor’s screen.
- What is a trackball? How it is different from a mouse?
- Explain how a trackball is used to notify the system of a particular user choice out of a given set of choices on a monitor’s screen.
- What is a joystick? How it is different from a trackball? Write some uses of a joystick.
- Explain how an electronic pen is used as an input device.
- What is a touch screen device?
- Write some applications for which touch screen is the most suitable input device.
- What is an information kiosk? Write some uses of an information kiosk.
- Write short notes on:
- What are data scanning devices? How do they help in improving input device data accuracy as compared to keyboard devices?
- What is an image scanner?
- Differentiate between a flatbed and a hand-held image scanner.
- What are the limitations of an image scanner when it is used for inputting text documents? How an OCR device overcomes these limitations?
- What is an OCR device? list some of its advantages and limitations for inputting text documents.
- What is an OMR device? Explain the technique used by it for recognitionj of marks. Write some applications that make use of it.
- What are bar codes? How does a bar-code reader read bar-coded data? Write a use of a bar-code reader.
- What is the Universal Product Code (UPC)? Which input device is used for inputting data based on UPC?
- What is an MICR device? Which industry is the primary user of MICR?
- Explain how an MICR device helps in faster processing of bank cheques with greater accuracy.
- What is the main limitation of MICR technology?
- What is a digitizer? What are its two main components? What are its main areas of application?
- Explain how a digitizer can be used to convert a drawing into digital form for storage in computers.
- What is an electronic card? Write two applications where electronic cards can be used effectively.
- What is a speech recognition device? Why do currently available speech recognition devices have limited success?
- Write some applications of speech recognition systems.
- What is a vision-input system? Write some applications of vision-input systems.
- Write short notes on:
Optical Mark Reader (OMR)
Optical Character Recognition (OCR)
Speech recognition devices
Magnetic-ink Character Recognition (MICR)
- Write short notes on:
Data scanning devices
- What is an output device? Name some commonly used output devices.
- Differentiate between soft-copy and hard-copy outputs.
- Name two output devices used for producing soft-copy output and two output devies used for producing hard-copy output.
- What is a computer terminal? Why it is so called?
- What is a monitor device? Name the two basic types of monitors along with their relative advantages and disadvantages.
- What is a flat panel monitor? Where it is commonly used?
- What is a printer? What are the commonly used types of printers?
- Differentiate between impact and non-impact printers. Write their relative advantages and disadvantages. Name few printers of both types.
- Explain the printing mechanism of dot-matrix printers.
- List key features and limitations of dot-matrix printers.
- Explain the printing mechanism of inkjet printers.
- List key features and limitations of inkjet printers.
- Explain the printing mechanism of drum printers.
- List key features and limitations of drum printers.
- Explain the printing mechanism of chain/band printers.
- List key features and limitations of chain/band printers.
- Explain the printing mechanism of laser printers.
- List key features and limitations of laser printers.
- Write short notes on:
- What is a plotter? What types of users need it?
- Explain the working mechanism of a drum plotter.
- Explain the working mechanism of a flatbed plotter.
- What is a screen image projector? What it is used for?
- What is a voice response system? Write some of its typical applications?
- What is a voice reproduction system? How does it function? Write some of its applications.
- What is a speech synthesizer? How does it function? Write some of its applications.
- Write short notes on:
Screen image projector
Voice response systems
Voice reproduction system
- Write the full forms of following abbreviations: