Thus, Things to Consider When Choosing a Printer:

How much output?	What speed is needed? Is heavy-duty equipment necessary?
Quality of output needed?	Letter quality? Near letter quality? Draft?
Location of printer?	How big a footprint can be handled? Is loudness important?
Multiple copies needed?
Color print needed?

Screens

Screen Features

The device which displays computer output to us has various names:
Screen	from "computer screen" or "display screen"
Monitor	from its use as a way to "monitor" the progress of a program
VDT	= video display terminal  from early network terminals
CRT	= cathode ray tube   from the physical mechanism used for the screen.
VDU	= visual display unit  to cover all the mechanisms from desktop CRTs to LCD flat screens on laptops to LED screen on palmtops

Making Colored Pictures c rt screen:

A standard monitor screen is a CRT (cathode ray tube). The screen is coated on the inside surface with dots of chemicals called phosphors. When a beam of electrons hits a dot, the dot will glow. 

On a color monitor these phosphor dots are in groups of three: Red, Green, and Blue. This RGB system can create all the other colors by combining what dots are aglow.

There are 3  signals that control the 3 electron beams in the monitor, one for each RGB color. Each beam only touches the dots that the signal tells it to light. All the glowing dots together make the picture that you see. The human eye blends the dots to "see" all the different colors.

A shadow mask blocks the path of the beams in a way that lets each beam only light its assigned color dots. (Very cool trick!) 

Lcd screen

LCD (Liquid Crystal Display) screens use an entirely different technique. The screen is still made of dots but is quite flat. LCD displays are made of two layers of a polarizing material with a liquid crystal solution in between. An electrical signal makes the crystals line up in a way that keeps light from going through entirely or just partly. A black screen has all the crystals lined up so that no light gets through. 

A color LCD screen uses groups of 3 color cells instead of 3 phosphor dots. The signal for a picture cleverly lets just the right spots show their colors. Your eye does the rest.

Scan Pattern

There are two patterns used by different monitors to cover the whole screen. Both scan across the screen, in a row 1 pixel high, from left to right, drop down and scan back left. 

The non-interlaced pattern scans each row of pixels in turn, from top to bottom. This type is more prone to flicker if the scan has not started over by the time the phosphor dots have quit glowing from the last scan. This can make your eyes hurt or even make you nauseous.

The interlaced pattern scans every other row of pixels. So the odd rows are done, then the even rows, in the same left to right to left way. But since the rows of pixels are very close together, the human eye doesn't notice as easily if a row has gone dim before it is rescanned. Much friendlier to your eyes and stomach.