Information Technology

Output Devices

Lecture 6

Presented by Miss N. Nembhard

Output Devices

Receives an electrical signal and produces data or information.

The purpose of an output device is to translate data and information from electrical impulses (digital) to human readable format.

The Monitor

An output device which is necessary for the computer to display an output to the user.

The video display Adapter (video card) on the motherboard allows information to leave the processor and appear on the monitor.

Types of Printers

1.Liquid Crystal Display (LCD)• These monitors are much thinner and lighter than the

bulkier CRT monitors. They also use a lot less energy. LCD monitors use to be very expensive but the prices have fallen drastically.

2. Cathode Ray Tube (CRT)• These are bulky monitors that look like old fashioned

TVs. They are usually much cheaper than LCDs.

Terms Associated with the Monitor

Soft copy - copy of a file shown on the screen. It is intangible.

Pixel (Picture Element) - A single point (a dot) in an electronic image. The greater the number of pixels, the better the quality of the image.

Screen Clarity

Screen clarity depends on three things: Resolution - Defines the clarity of an image

and is specified as the number of dots per inch (dpi). Normally measured by the number of pixels that can be displayed.

Dot Pitch - Amount of space between pixels Refresh Rate - Number of times per seconds

that the pixels are recharged so that their glow remains bright.

The Printer

An output device that produces tangible copies or hard copies.

Hard copy -A tangible copy of a document produced by the printer e.g. flyer, letter, book, a card etc.

Categories of Printers

There are two main categories of printers:

Impact - the printing mechanism makes physical contact with the paper

Non-Impact - No physical contact between the printing mechanism and the paper.

Types of Impact Printers

There are two main types of impact printers:1. Line Printers

2. Character printers

Both types of impact printers print on perforated paper.

Line Printers

Printers that can use multiple print hammers to print an entire line of text at one time (or at least fast enough so that it appears so).

Disadvantages:1. It cannot print graphics

2. The text it prints is of low quality

Character (Serial) Printers

Character or serial printers are printers that print a character at a time.

These are slower than line printers

Types of Character Printers

The two main types of character printers are:1. Daisy wheel

2. Dot matrix printers

Daisy wheel

Daisy wheel printers – uses a wheel containing characters that rotates until the right character is facing the paper.

Although it prints high quality text, it cannot print graphics. Printing different types of font is also impractical since the wheel have to be changed in order to get a different font.

Dot Matrix Printer

The dot matrix printer have a head capable of firing tiny pins arranged in a matrix. As the print head moves back and forth, these pins strike the ribbon causing dots to be made on the paper.

These same dots can be used to print text as well as graphics

Some dot matrix printer can also print in color.

Dot Matrix Printers

They are used to print bills or forms that require carbon copies

Print special reports that require large continuous sheets some payroll and accounting sheets

Advantages of Impact Printers

Produces carbon copies of information being printed.

Inexpensive Maintenance is inexpensive Uses ink ribbons which are inexpensive

Disadvantages of Impact Printers

They are relatively slow Draft quality is low Ink ribbons have short lives Noisy

Non Impact Printers

Non-Impact printers are printers that print using methods that do not involve striking the paper or an ink ribbon.

They are generally faster than most impact printers and quieter.

Some types are much more expensive than impact printers

Non-Impact printers do not use perforated paper

Types of Impact Printers

Inkjet printer Laser printer Thermal printer

Inkjet Printer

They squirt very small drops of ink on the paper in order to produce text and images.

They are commonly used in the home. The are relatively cheap and produce

high quality output at relatively high speed.

Laser Printer

A very fast printer that utilizes a laser beam along with a toner and a photoconductive rotating drum in order to produce very high quality output.

They are faster than inkjet printers They are called page printers because it

appears that they print an entire page at one time.

They are usually limited to office use because they are expensive.

Thermal Printers

They print by using heat. Some thermal printers use special heat-sensitive paper.

Heat is applied to the paper to form text and graphics

They have low maintenance cost since there is not the need to buy toner or print ribbon.

Some fax machines print using this method.

Advantages of Non-impact Printers

Produce high quality and high speed output

Almost noiseless uses toner or ink cartridges, which are

longer lasting

Disadvantages of Non-Impact Printers

Printers are usually expensive Maintenance is also expensive Toner is relatively expensive

Types of Printers

Dot Matrix: Impact printer

Inkjet: Non-Impact printer

Laser: Non-Impact printer

Plotter Output device used

to produce high quality drawings (images) and large hard copies e.g. posters.

Chosen over printers when high quality graphics and making large clear posters.

Plotters continued

Have built in microprocessors that converts characters and instructions into a series of coordinates, which the plotter then plots.

Produces high resolution images Used by engineers, graphic designers,

architects.

Speakers

Sound cards code audio signals into signals which can be used by the speaker, which in turn amplifies them.

Sub woofers - Speaker system that can be attached to your PC and speakers to enhance your sound effects.

Computer Output on Microfilm

Computer output on film rather than on paper.

Stores images on plastic films.

Images are held in a much reduced format.

Microfilm

Reels of films used to store data or images.

Primarily used to store for preserving journals and news papers and hold hundreds of prints on one film.

Microfiche

Flat individual sheets of film.

Primarily used to preserve government document and college catalogues. A special reader is needed to view the pages stored.

Multimedia Projector

Works with a variety of media, e.g. computer, camera, printer and the scanner.

It projects and magnifies images on a large white screen normally mounted on a wall some distance from the computer.

Other Types of Output Devices

Audio output devices for example:– Speakers

– Head-phones

– Earphones

Human Readable vs Machine Readable

Human Readable - output devices that produce hard or soft copies of information or data that can be read and interpreted by humans

Machine readable - devices that output in a form only a computer can process.

Activity1. Explain the following terms associated with the

monitor:

a. Resolution

b. Pixel

c. Dot Pitch

d. Refresh Rate

2. Identify the two main types of printers

3. Give an example of each of the two types of printers you identified above.

4. Differentiate between the terms : “hardcopy” and “softcopy”.

References

Information Technology for CSEC, Kelvin Skeete & Kyle Skeete