Monitor/data projector
The most commonly used output device is the first place that you would expect to see the results of your input and that would be the screen in front of you.
The image on the screen is made up of hundreds (and thousands) ot tiny dots called pixels (picture elements). Each dot is assigned a specific colour (one of 32000 different colours) and in this way the image is built up. The job of the video card is to redraw the screen when changes have taken place in order to produce a smooth and elegant image.
This to know about the screen image:
the colour depth (how many different colours can be reproduced at each pixel)
The resolution (how many pixels are used to create the entire screen, normally represented as a width X height expression (1024X768)
The more pixels your screen image has and the more colours that can be represented the more memory is needed by the video card to store the image.
The technology has advanced to the point that even an entry level video card built in to a bottom of the range motherboard will be able to produce a screen image at a resolution and colour depth far grater than most monitors can represent.
Types of screens:
Cathode ray tube
A large and energy inefficient screen type where a beam of electrons is blasted against the inside of a phosphor coated glass screen. When the phosphor coating gets hit by the electron beam it glows for fraction of a second.
The inside of the screen but be repeatedly scanned at over 50Hz in order to fool your eyes into believing that there is a steady image in front of you. this is known as the refresh rate... higher is better. No refresh rate is required with other screen types.
Plasma
more commonly used in TV sets than in computer monitors because plasma screens have a lower resolution than LCD because the pixels are quite large. They are excellent for larger TV screens because they can change colours very quickly, which reduces artefacts on the screen like blurs and trails
plasma screens user more electricity than LED screens and are not as environmentally friendly because they contain noble gasses
LCD (with a fluorescent light as a back light or with LED's as a back light)
Liquid Crystal Display is a very popular screen type found in all portable computers and more commonly with desktops these days.
LCDs are environmentally friendly because of low power consumption, especially when they use Light emitting diodes as the back light.
Printer
Printing technologies have evolved over the years and we are now able to find a wide variety of printers that fill all the niches of printing.
dot matrix
This printer is an impact printer that allows each character to be formed from a matrix of 9 (low res) or 24pins (higher resolution)
On the 9 pin printer very limited font choice can be accommodated and images..... not so good
24 pin allows a wider variety of cont choices and images can be printed but you would be disappointed with the output when you compare it to a laser of inkjet printer
daisy wheel
With a Daisy wheel printer you could support a wide range of different fonts, in order to change the font you would need to change the daisy wheel. printing of images is a no go with this type of printer
line printer
a Line printer is similar to a dot matrix printer except that instead of having a vertical line of 9 or 24 pins to produce the output, it has a line of pins as wide as the page and uses the line of pins to produce the output. it was designed for very high speed and low resolution printing, like bank statements or financial statements that would be thousands of pages long. These printers used fan fed paper and could really spew our pages at a rate that no other printer type has been able to match to this day.
phaser
Phaser printers were developed by Xerox and used melted wax instead of ink to make the images on the paper. They are able to produce beautiful glossy full colour pages that are water proof. They are very expensive to buy and very expensive per page to use and are often found in design studios where the quality of the printed output is of a very high importance
ink jet
The ink jet printer is a technology where the liquid ink is sprayed onto the paper surface in tiny jets (hence the name)
They are very cheap to buy but are quire expensive per page
ironically you can often buy the printer for less than the cost of the replacement cartages.
There are ideal for the home user who would only require a very low number of printed pages per month
laser
In this technology the entire page is charged negatively with static electricity, then the image is traced out by a laser onto the paper surface. Where ever the laser has hit the page that part of the page is charged positively. The page is then passed through a cloud of very fine negatively charged toner. Where the paper has not been hit by the laser the negatively charged paper will repel the negatively charged toner and the paper will stay clear. Where the positively charged paper meets the negatively charged toner, the toner will stick.
The page is then heated to melt the toner onto the page and the image it complete.
Laser printers are more expensive to buy than ink jet but the cost per page is lower.
plotter
A Plotter is a printer with a pen as the point of contact. The pen is dragged across the surface of the page as instructed by the print job
Plotters can hold very large pieces of paper up to A1
They are most commonly used by architects and draughtsmen for printing the plans of a structure out
vinyl cutter
a vinyl cutter is a plotter with a sharp knife instead of a pen.
These devices are used to cut lettering for signs and large posters
3D printer
These devices user various different techniques to produce a 3 dimensional object
Most use tiny drops of wax or latex to deposit layer after layer one on top of the other until the object has been constructed.
These devices are used to create prototypes that can be assessed for real world functionality before they go into mass production.
Speakers/Headphones
Speakers or headphones are needed in order to make the output from the sound card audible. Most portable computers have the speakers built in but on desktops a set of speakers is often required. More often than not amplified speakers in the configuration 2.1 (two channels[left and right] plus a base) or 5.1(5 speakers plus base) or 7.1 for the full surround sound experience.
Servo motor
Motors can be attached to the output ports of a computer and connected to anything that can be moved. This will allow you to close a window, turn a switch on or off from the computer. If the computer is also connected to the internet then you could close the same window from anywhere in the world as long as you could connect to the internet. Adding servo motors to a controller box and connecting that to your computer can be a heap of fun.... you can fully automate and remote control your world.