January 23, 2009

Computer Graphics Assignment

What is a keyboard?
  • A keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, which act as electronic switches.
  • A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol.
  • However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence.
  • While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands. The keyboard switch matrix is wired to its inputs and it processes the incoming keystrokes and sends the results down a serial cable (the keyboard cord) to a receiver in the main computer box.
  • The keyboard is used to type text or numbers into a word processor, text editor or other program.
  • Keyboards are also used for computer gaming.
  • A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine.
Types of keyboard:
  1. Standard
  2. Gaming and Multimedia
  3. Thumb-sized
  4. Numeric
  5. Chorded
  6. Virtual
  7. Touch Screen
  8. Foldable
  9. Wireless
What is CRT?
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to form images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms (oscilloscope), The single electron beam can be processed in such a way as to display moving pictures in natural colors.The CRT uses an evacuated glass envelope which is large, deep, heavy, and relatively fragile. The earliest version of the CRT was invented by the German physicist Ferdinand Braun in 1897 and is also known as the 'Braun tube'In television sets and computer monitors the entire front area of the tube is scanned systematically in a fixed pattern called a raster. An image is produced by modulating the intensity of the electron beam with a received video signal Graphical displays for early computers used vector monitors, a type of CRT similar to the oscilloscope but typically using magnetic, rather than electrostatic, deflection. Magnetic deflection allows the construction of much shorter tubes for a given viewable image size CRTs have a pronounced triode characteristic, which results in significant gamma
CRT screens have much deeper cabinets compared to LCD screens for a given screen size. LCDs have generally inferior color rendition due to the fluorescent lights that can be used as backlights, even though they can be brighter overall. CRTs can be useful for displaying photos with a high pixels per unit area and correct color balance. The end of most high-end CRT production in the mid 2000s (including high-end Sony, and Mitsubishi product lines) means an erosion of the CRT's capability
CRTs are also still popular in the printing and broadcasting industries as well as in the professional video, photography, and graphics fields due to their greater color fidelity and contrast, better resolution when displaying moving images, and better view from angles, although improvements in LCD technology increasingly alleviate these concerns. The demand for CRT screens is falling rapidly,[9] and producers are responding to this trend
CRTs operate at very high voltages, which can persist long after the device containing the CRT has been switched off and/or unplugged. Residual charges of hundreds of volts can also remain in large capacitors in the power supply circuits of the device containing the CRT; these charges may persist. Modern circuits contain bleeder resistors, to ensure that the high-voltage supply is discharged to safe levels within a couple of minutes at most. These discharge devices can fail even on a modern unit and leave these high voltage charges present. The final anode connector on the bulb of the tube carries this high voltage


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