Subject: Computer Basics
These are the devices which enable our senses to persive the result of computer processing to see the result and display it. Example of output devices are monitor, printer etc.
LCD (liquid crystal display): In LCD, liquid crystalline material is sandwiched between two glasses or plastic plates. The front plate is transparent and back plate I reflective. There is coating of thin film on the front plate. The coating is transparent and conducting. The segment on the LCD screen are in the shape of desired character. An electrically conductive film or back plane is put on the segment and the back plate, electric field is created on the region under the segment. The electrical field makes change in transmission of light through region under a segment. There are two types of commonly available LCD. They are: Dynamic Scattering LCD and Field effect.
Plasma Display: In plasma display, ionized gas is sandwiched between two glasses plates. There are a number of thin parallel wires running horizontally and vertically. A small amount of current is passed in horizontal and vertical wires to cause the gas to glow at the spot at the intersection of the wires. Plasma display devices can be seen from the wide angle 160 degree. In plasma display phosphor material is used for its shape.
Light Emitting Diode (LED): This type of display device multiple light emitting diode in specific way required to display the output. LED display are used as:
LED display are mostly used in seven segment display. A seven segment display is simple and they are used to display digits and hexa -decimal letters. To display number and entire alphabet. In dot matrix display particular dot point can be swiched on to display any alpha- numeric characters.
Cathode Ray Tube: When high voltage is applied in the electron glass of CRT tube, electrons get generated from the cathode. Electron travel in the straight line due to anode present in opposite side as in figure. Deflecting coil enables the electron beam to strike at the desire location of the phosphorus coated screen. When the electron beam strikes the screen, the light gets emitted and image is observed. Method of display:
Printer is an output device which produces hard copy output and not required electric power as they are printed on paper to read after printing. They provide information in a permanent readable form classification of printer.
Quality The quality of printer depends on resolution. The number of dot point per unit area or sharpness of text images per inch is called resolution. The high resolution printer has higher quality than lower resolution.
Impact printer: This type of printer produces sound while printing. The sound is produced when the printing head strikes the ink coated ribbon and paper. Example: dot matrix printer, drum printer, band printer etcâ€¦
Non-impact printer: This type of printer produces low sound or donâ€™t produce any sound while printing. Because in this type of printer, printing head does not strike the ink coated ribbon. Example laser printer, inkjet printer etcâ€¦
speed: The impact printers are slower than non-impact printer. The more expensive the printer the more fast it is.
Memory: The printer which have its own memory can hold the process data and has higher speed. The memory of the printer is called spooter directly where files to be printed is queues.
Colour: The colourful text and graphics are more attractive than plain text and graphics. Color printer are quality printer than non-color printer.
Dot matrix printer: It is slow, noisy printer where printing head contains matrix of pins. The number of pins denote the quality of output. The number of pins available on the head maybe 7, 9, 14, 18 or 24. This type of printer produce characters strictly pins against ink ribbon to print closely spaced dots in appropriate shape.
Laser printer: It is non-impact high resolution printer and can print entire page at a time. It can print 8-10 pages per minute. In laser printer the paper is passed from electrically charged wire that stimulate either-ve or +ve charge depending upon the tonner vibration. The â€“ve charged paper remain white whereas +ve charged region paper remain black (attract carbon particle from the tonner and become permanent black in color in the form of text or graphics.)
|CRT monitor||LCD monitor|
|i. It is made by glass and heavier.||i. It is made by liquid crystal material and |
|ii. It is cheaper and not portable.||ii. It is expensive and portable.|
|iii. It produces low quality.||iii. It produces high quality output.|
|Impact printer||Non-Impact printer|
|i. It produces sound while printing.||i. It does not produce sound while printing.|
|ii. It is cheaper.||ii. It is expensive.|
|iii. It prints slowly.||iii. It prints fastly.|
|iv. E.g. Dot matrix||Iv . E.g. Laser|
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