Output Devices

Output Devices

1. CRT VDUs

   • The first computer monitors used cathode ray tubes (CRT). CRT VDU stands for Cathode Ray Tube Video Display Unit.
   • They were monochrome and flickered, they also provided poor images. They were good because they were superior to previous models

2. Dot Matrix Printers

   • The print head contains a grid of pins and different combinations of pins are pushed out to form different characters. The print head then hits a carbon ribbon leaving an impact on the paper
   • Cheap to buy and maintain, Can print on, continuous stationary, Create carbon copies, Robust and work well in harsh dirty conditions (garages/factories. Poor print quality, Very slow, Noisy, Cant produce colour copies

3. Plotters

   • Plotters are a specialist type of printer which is able to draw high quality images on very large pieces of paper. They are used by engineers, architects and map-makers to draw plans of buildings, diagrams of machines or large scale maps. A plotter draws images using a pen that can be lowered, raised and moved across the paper to form continuous lines. The electronically controlled pen is moved around the paper by computer controlled motors.
   • Drawings are of the same quality as if an expert drew them, Larger sizes of paper can be used, Plotters are slower than printers because each line is drawn separately. They are often more expensive than Printers. They do not produce very high quality text printouts

4. Speakers

   • Most computers are fitted with a small internal speaker which can produce beeping sounds to alert you if you make an error. Computers can also be fitted with a sound chip which can enable sound to be output through external speakers
   • Everyone in the room can hear the output. Helps blind people. Can disturb people. High quality speakers can be expensive

5. Drivers

   • A device driver is a computer program that operates or controls a particular type of device that is attached to a computer.
   • Need knowledge to initially set up. Drivers are hardware-dependent and operating-system specific.

6. LCD Monitors

   • LCD stands for liquid crystal display. It is a type of monitor that was used after CRT. It is a flat panel display
   • They produced images of higher quality and took up less space than CRT VDUs. LCD monitors are also easier on the eyes. They are more fragile and more expensive than CRT VDUs. LCD monitors can only display information well at the resolution they were designed for. At any other resolution, image quality will suffer.

7. LED Displays

   • An LED display is a flat panel display, which uses light-emitting diodes as a video display.
   • LED is a lot thinner than the LCD or Plasma. At the moment the price of LED are pretty high compare to LCDs. Suffers from motion blur

8. Laser Printers

   • Powdered ink ‘Toner’ is fused onto paper by heat and pressure.
   • High quality print outs (best), Fast print outs (fastest), Very quiet printing (quietest), Cost per page is low (cheapest). Most expensive to buy, maintain and repair, Bulky

9. Inkjet printers

   • Operate by heating the ink as it flows through a set of tiny nozzles. The hearting process causes a small droplet of ink to form. This is then released as a single dot which forms part of a letter or image
   • Cheap, Compact, Cartridges cost less than toners to replace, Product medium quality printouts, Speed fast than dot-matrix but slower than laser, Noisier than a laser, Colour printing can be very slow, Print outs cost more than a laser, Ink will smudge while wet, Colours don’t often look the same as on the screen, Cartridges can dry out

10. Resolution

    • When someone describes a 'high resolution' monitor, they mean that it can display a large number if pixels per inch. Pixel is short for Picture Element. A pixel is the smallest individual dot that can be displayed on a computer monitor. Each pixel is given a colour and brightness value. An image is made up of many pixels. The quality of the image depends on the number of pixels per inch that make up the image.
    • With more pixels, you can further crop the images for a telephoto effect. Also, if you want to print huge enlargements (like really large posters), more megapixels is advantageous. Besides the storage space disadvantage, software will take longer to process these enormous image files.

11. Spooling and buffering

    • Spooling: Processes are not suspended for a long time. Need large amounts of disk space. Buffering: Can receive data at a high speed, Works at different speeds
    • Spooling, an acronym of Simultaneous Peripheral Operation On-line (SPOOL), puts data into a temporary working area so it can be accessed and processed by another program or resource. Buffering allows data to be stored temporarily into a reserved area of memory (the buffer).

12. Actuator

    • The 'actuator' is the name given to a device that moves something when commanded to do so.
    • A linear actuator has a long lifetime with little or no maintenance at all. Low force.