These are the cheapest, and are the most popular printer for at home. They spray jets of ink as the paper is fed past the print head
These are more expensive. They are the most versatile output device. Pages are set up in full before printing. The 4 main parts are:
- Rotating Electrostatic Drum - has an electrical charge
- Laser - etches on to the drum a negative image of the page that will be printed. Where the laser hits the drum, the electric charge is removed
- Toner Cartridge - contains ink. When the drum passes over the toner cartridge, the ink is attracted to the charged areas. Ink is transferred onto printer paper
- Fuser Unit - heats the paper to fuse the ink to it
The user needs to think about what they want before buying a printer.
Inkjets are very cheap to buy, laser printers are fairly expensive
Laser printers have a high page-per-minuter rate
Laser printers produce higher quality documents than inkjet
Laser printers are often more cost effective
Other types of printers are:
- Dot Matrix
- Graph Plotters
- Thermal Printers
Dot matrix printers nowadays are mainly used for printing reciepts - they print a series of dots
Braille printers, also called embossers, are used to create sequences of rasied dots
Graph plotters have an automated arm which disperses ink - used for large sheets of paper
Thermal printers can also be used for printing reciepts, and are a lot quieter and faster at printing than a dot matrix printer.
Monitors are probably the most obvious output device. The main considerations are:
- Screen size
- Picture quality/resolution
Monitor screen size is measured in inches from corner-to-corner. The most common sizes are between 17" and 22"
Resolution tells you how many pixels the monitor can display - usually 1280x1024 pixels. Dot pitch tells you the distance between the pixels, so lower value = sharper picture.
Most new computer systems have flat panel screens using TFT (thin film transistor) or LCD (liquid crystal display) technology. These are thin, lightweight and portable compared to the old CRT (cathode ray tube) monitors - these have virtually died out.
Plasma screens are also popular - these can give better picture quality, especially for larger screen sizes (between 35" and 50"). This makes them more suitable for specialist uses, e.g. for presentations.
LCD and plasma have pretty much replaced CRTs in the television market too.
The newer technologies have some disadvantages too:
- LCD screens don't always give as good picture quality as CRTs and can be hard to view at certain angles
- Some LCDs can struggle with moving images, giving a smearing effect.
- Plasma screens are hot too touch and are prone to image burn if screen saves aren't used.
Acuators are output devices that are able to perform simple mechanical tasks.
- These are powered by electrical signals
- These are powered by fluid pressure controlled be the computer.
- They are slow, but very powerful
- These are like hydraulic acuators, but powered by air pressure.
- Less powerful, but more responsive
- These are often used by companies for presentations
- They project a computers output onto a large screen - can be used to show text, images and videos etc.
- These are another fairly obvious output device for any system requiring sound.
- In some cases, speakers might be used as a primary output device - for someone who is visually impaired.