Computer Fundamental

MSCH 233

Lecture 6

Printers

Printer is an output device which convert data into printed form. The output from a printer is referred to as a print-out.

Printers vary in: Cost Speed Print Quality Noise Capability

There are two types of printers: Impact printers Non impact printers

Impact Printers

Impact printers is like a typewriter uses some form of strike-on method to press a carbon or fabric ribbon against paper to create a character

Example:

Dot-matrix printers

Dot-matrix printers

Create characters from a rectangular grid of pins. The pins strike against a carbon ribbon to print on paper.

Produce low resolution72 or 144 dots per inch (dpi).

Slow & cheaper than laserSuitable for drafts , and not recommended

for reports or books that have a wide audience.

Non-impact Printers

Non-impact printer is a printer that produce images by methods other than the strike-on methods

Examples: Ink-jet Laser Thermal Imagesetters Plotters

Ink-jet Printers

Operates by projecting small ink droplets onto paper to form the required image.

Use color ink.Quite fast, silent, not so expensive as a

laser printerSuitable for graphics application.Can expect high quality results when the

resolution is 720 dpi

Laser Printer

Produces at great speed and very high resolution of 600/2400 dpi.

Scans the images with a laser beam and transfer it to paper with a special ink power.

Colored laser printers are still expensive for home users

Reasons it’s preferred by experts: Have wide range of scalable fonts. Emulate different language systems Produce graphics

Thermal Printer

It use heat, a special kind of paper and electrosensitive methods.

Silent and inexpensive some color models cost too much.

Less popular than ink-jet and laser printers because they are slow, the paper is expensive an the image deteriorate over time.

Imagesetters

Produce very high resolution output up to 3540 dpi on paper or microfilm

Extremely fastUsed in desktop publishing.Too expensive for home or small offices.

Plotter Printer

Special king of printerUse ink and fine pens held in a carriage to

draw very detailed designs on paper.Used for construction plans, engineering

drawings and other technical illustrations.

Computers for the disabled

Adding assistive technology to computers to help blind , deaf, and motor disabled to use computers in their jobs, learn at school, interact with their families at home.

Blind Users

Blind users need to have their computers adapted with technologies like Braille, magnification, speech synthesis , and Optical Character Recognition (OCR)

Braille Keyboard: allow users to easily identify each key. For Braille output there are printers that emboss Braille on both sides of a page.

Magnification Program: used for someone with limited but usable vision. The program will enlarge text appearing on the screen by up to 16 times. In addition, they are now being developed with various levels of speech output capability.

Speech-synthesis: used to read loud the work on the computer. It has a speech synthesizer, which produce the audio output. The program reads menu from word processor, database, and the web.

OCR: Uses a flatbed scanner and specialize OCR software to read printed material and sent the text to the computer. Then the Computer produce a copy of the text in Braille , a magnified copy or a version that can be read load by Speech-synthesis system.

Deaf Users

Deaf Users can overcome many communication difficulties with the aid of visual alert and electronic note takers.

Visual Alert: indicators that alert the deaf user when there is an error. Instead of hearing a sound, the user alerted by a menu bar blinking or by a message on the screen.

Electronic note-taker: it a device that print out what is spoken in meetings or business presentation, where lip-reading is not possible.

Motor-impaired workers

Are unable to work on a standard keyboard uses on screen keyboards, adaptive switches and voice recognition systems.

On screen keyboard: are software images of a keyboard that appear on the screen and may be activated with a trackball, touch screen, screen-pointing device, or eye movement. The eye-gazed system is activated by the user’s eye when they pause on a key for 2 or 3 seconds.

Adaptive Switches: comes in shapes and sizes. They are operated by muscle movements or breath control.

Voice Recognition System: Allow the computer to interpret human speech, transforming the words into digitized text or instructions.