LESSON 3 : OUTPUT DEVICES

What is Output?

Input
Processing
Output
Storage

Output is data that has been processed into useful form, now called Information

Types of Output

	Hard copy: printed on paper or other permanent media
	Soft copy: displayed on screen or by other non-permanent means

Categories of Output


Text documents including reports, letters, etc.	Graphics charts, graphs, pictures	Multimedia combination of text, graphics, video, audio

The most used means of Output are the printer and the computer screen. Let's look at the features of each.

PRINTER

The job of a printer is to put on paper what you see on your monitor. How easy this is to do and how successfully it is done determines whether or not you are happy with your printer choice.

Monitor screens and printers do not use the same formatting rules. In the olden days of computers, the way something looked on the screen could be VERY different from how it would look when printed.

Early word processors didn't have a way to show what the printed version would look like. Now a word processor that doesn't have print preview, would be laughed off the shelf. Most have a WYSIWYG view, where you see almost exactly what the document will look like in print, while you are still working on it.

How fast?

The speed of a printer is measured in:

cps	= characters per second
lpm	= lines per minute
ppm	= pages per minute
The faster the printing, the more expensive the printer.

What paper type used?

Continuous-Form Paper

Advantage:	Don’t need to put in new paper often
Disadvantage:	May need to separate the pages and remove the strips of perforations

Single Sheet

Advantage:	Can change to special paper easily, like letterhead or envelopes
Disadvantage:	Must add paper more often

What print quality?

LQ	Letter Quality =	as good as best typewriter output
NLQ	Near Letter Quality =	nearly as good as best typewriter output
Draft	used internally or for a test print
The better the quality, the slower the printing.

A more numerical measure of print quality is printer resolution. Measured in dots per inch (dpi), this determines how smooth a diagonal line the printer can produce. A resolution of 300 dpi will produce text that shows jagged edges only under a magnifying glass. A lower resolution than this will produce text with stair-step edges, especially at large sizes. Even higher resolutions are needed to get smooth photo reproduction. Professionals in graphics use 1200 to 2400 dpi printers.

What will it print?

Printers vary in what varieties of type they can print. You must know the limits of your printer to avoid unhappy surprises!

Typeface

Set of letters, numbers, and special characters with similar design
Sample fonts

Styles

Bold, italic, underlined...

Size

Measured in points
One point = 1/72 of an inch like: 12 pt 18 pt 24 pt 36 pt
Use 10 or 12 pt for writing a letter or report.

Font

A complete set of letters, etc. in the same typeface, style, and size

Color

Printing in color takes longer, uses more expensive inks/toner, looks best on more expensive papers, but can add a lot to the quality of the output

Graphics

Pictures add a lot to a document, but not all printers can print graphics.

How big?

The footprint, or the physical size of a printer, determines where it can be placed.

What kind of cable connection?

Serial cable	Sends data only 1 bit at a time Printer can be up to 1000 feet away from the computer. Maximum data transfer speed = 115 kilobits/s (.115Mbits/s)
Parallel cable	Sends data 8 bits at a time Printer must be within 50 feet of the computer. Maximum data transfer speed: 115 kilobytes/s (.115MBYTES/s). This is 8 times faster than the maximum serial speed. Newer printers may need bi-directional cable so that the printer can talk back to the computer. Such a cable is required if the printer can give helpful error messages. It's startling, but nice, the first time your computer politely says "Ink is getting low" or "Please place paper in the AutoSheet feeder."
USB cable	Printer must be within 5 meters (16.5 feet) of the computer, when connecting straight to the computer. [You can hook up several 5 m. cables and USB hubs in a chain - up to 25 meters.] Maximum data transfer speed: 12 megabits/s (1.5 MBYTES/s) Lots faster!
Best choice: The new USB (Universal Serial Bus) connection is likely your best choice, if your printer can use it. It is faster and a USB connector can be unplugged and re-plugged without turning off the system. USB ports are gradually, but rapidly, replacing parallel ports. The printer cannot handle the data as fast as the USB port can send it. The real limit on how fast a printer works is in how fast printer can get the characters onto the paper. Serial cable may have to be used if a printer is shared in a fairly large office, due to the length needed.