Input and output devices
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The document discusses various input and output devices for computers. It describes keyboards, mice, scanners, light pens, and microphones as common input devices. Keyboards convert pressed keys into electronic signals representing input, while mice allow cursor movement on screen using light sensors. Light pens detect screen light to select menu options. Microphones record sound as computer files. The document also outlines visual display units, plotters, printers, and speakers as major output devices, describing how printers can be either impact-based or non-impact and how speakers produce sound from computer audio.
Input and output devices
- 2. Some input devices are :- i. Keyboard ii. Mouse iii. Scanner iv. Light pen v. Microphone
- 3. Keyboard It is the most commonly used input device. It has various keys like numeric keys, alphabetic keys, function keys, symbol keys, special keys like delete, arrow keys. When a key is pressed an electric signal exclusive for each key is generated which passes to the control unit. So , the input signal is converted into computer understandable code by the keyboard itself.
- 4. Another very popular device is mouse. It is about the size of human palm and rolls on a small bearing and has one or more buttons on the top. When a user rolls mouse on a flat surface, the cursor moves accordingly on the screen. Nowadays mouse is in great demand. It uses the reflected light to sense the direction of the movement.
- 6. It is a device for direct data entry. A special pen which has photo cells in its tube is attached to the monitor. When the pen is brought in contact with the screen, it detects the light emitted by the screen and this light activates the photocells. These photocells when activated generate electric pulses. Electric pulses send data to the computer and it can detect which menu option has been selected.
- 7. Microphone is a device which records voice or sound and puts it in the computer in form of a file. This file has as an extension .wav. Many laptops and some desktop monitors have inbuilt microphone in the form of a small hole in the front, otherwise a microphone is easily available in the market at a very low cost. Many microphones come with a headset earphones too.
- 8. Some output devices are:- i. Visual Display Unit(VDU) ii. Plotters iii. Printers a).Impact printers b).Non-impact printers iv. Speakers
- 9. It is used to view the output generated by the CPU in text or pictorial form. A VDU is similar to a television screen and consists of a cathode ray tube (CRT). Some characteristics of VDUs are:- • Display Colors • Size • Resolution
- 10. These are used to display graphical output. Flat Bed Plotters use a fixed paper and a pen-holding mechanism is allowed to move over it. Drum plotters use a paper placed over a drum that rotates back and forth to produce an up-down motion. One or more pens containing same or different inks are mounted horizontally and their movement is controlled through a computer.
- 11. They are the most commonly used output devices which produce a permanent copy of the output on a paper called the hardcopy. The digital copy of the documents stored in the memory is called the softcopy. Two broad categories of printers are :- a).Impact printers b).Non-impact printers
- 12. Printers in which the paper comes in direct contact with the printer ribbon and printer head are called impact printers. Common Categories:- • Dot matrix printers • Daisy wheel printers
- 13. Printers where paper does not come in the direct contact with the printer head are called non-impact printers. These use techniques like thermal, electrostatic, laser, chemical or inkjet technologies. Common Categories:- • Laser printer • Inkjet printer
- 14. Speakers They are also known as multimedia speakers and add life to music, movies and games on PCs by providing required sound effects. Speakers come in various sizes, output quality and price range. The speakers are equipped with low-power internal amplifiers and normally have a plug in connector lime green in color. Many VDUs have built-in speakers with very basic configuration. Mostly the external speakers are two plastic boxes which have the volume and tone control buttons.