Output devices
GOOD DAY, students. This is lesson four of our series of lessons. In this week’s lesson, we will examine the selection of appropriate output devices to meet the needs of specified applications.
OUTPUT DEVICES
An output device is a device which receives data in the form of electrical pulses from the CPU, as was shown in the data-processing cycle. It then converts this data into a form that can be understood by the user, a machine or another process.
There are two main categories of output devices:
■ Soft-copy output devices
■ Hard-copy output devices.
Soft-copy output devices get information to a computer monitor or other temporary output device that you can see but not necessarily touch (intangible).
THE MONITOR/VDU/SCREEN
This device provides output to the user. The video display adapter on the motherboard allows information to leave the processor and appear on the monitor. This type of copy that the monitor shows is known as ‘soft copy’ which, as stated above, is intangible.
KEY TERMS ASSOCIATED WITH THE MONITOR
■ Resolution – This is measured based on the output quality of the screen. If the monitor displays graphics and video images accurately, in that there are no grains, colour change or distortion, the resolution is good. In addition, the greater the pixels per inch of the screen, the higher the resolution.
■ Pixel – The short meaning for ‘picture element’ is referring to the dot per inch of the screen. The greater the number of pixels, the better the quality of the image.
AUDIO OUTPUT DEVICES
Audio output devices include those devices that output voice or voice-like sounds, and those that output music and other sound. These include headphones, speakers, earphones, sound cards, etc.
Multi-media projector –This is a device that is used primarily for projecting text, images, video and audio content. This device is commonly used by teachers, public speakers, business personnel, etc, to educate, to project PowerPoint presentations, to inform, etc. It may also be used for entertainment purposes, such as for the projection of a movie.
VISUAL (HARD-COPY) OUTPUT DEVICES
Hard-copy output devices are those that provide output on printed paper or other permanent media that is human-readable (tangible). Examples of devices that produce hard copy are: printers, plotters and microfiche. Examples of hard-copy documents would include a flyer, a letter, a book, a card, and so on.
PRINTERS
The purpose of the printer is to display on paper the information shown on the computer screen. The quality of what is on paper and how fast the information is put on the paper is dependent on your choice of printer.
Printer quality – This is determined by the printer’s resolution, which is measured in dots per inch (dpi). This determines how smooth a diagonal line the printer will produce. Thus, to output text or graphics (such as photos) at a high quality, the resolution would have to be quite high.
There are two types of printers: impact printers and non-impact printers.
IMPACT PRINTERS
With this type of printer, a hammer strikes an inked ribbon on to the paper to form a character, like a typewriter. Thus, the printing mechanism makes physical contact with the paper. One such printer is the dot matrix printer.
DOT MATRIX
This printer is relatively inexpensive and can print between 100-200 cps. Typically, a character is made up of a dot matrix 5 x 7. The characters are printed one at a time. Similar to how a score board shows its data, that’s how characters are formed using the dot matrix. Some printers are unable to produce graphics, only letters and numbers, such as the dot matrix.
ADVANTAGES
■ Inexpensive
■ Can make multicopy forms
DISADVANTAGE
■ Slow
■ Can be noisy
Application: The dot matrix printer is used in banks and at the pharmacy for the printing of receipts that needs to be printed in duplicate.
NON-IMPACT PRINTERS
With this type of printer there is no actual striking of the paper. Instead, it uses ink spray or toner powder, heat and special paper. Thus, the printing mechanism does not make physical contact with the paper. Non-impact printers include ink jet, thermal and laser printers.
INK JET
The ink jet printer, in comparison to the dot matrix or daisy wheel printer, has a much faster printing mechanism. Characters are formed by spraying ink on to the paper.
ADVANTAGES
■ It is quiet.
■ It produces high-quality text and graphics.
■ It is able to print colour.
■ It is faster than impact printers.
DISADVANTAGES
■ Cannot produce multiple copies.
■ The ink can smear on the paper after printing is done.
This is used for printing everyday documents, such as a letter, project, PowerPoint presentation, photographs, etc.
THERMAL PRINTER
This type of printer uses heat on chemically treated paper to form characters and images. A thermal printer is similar in nature to a fax machine that uses special rolls of paper.
ADVANTAGE
■ It is quiet.
DISADVANTAGES
■ It is expensive and requires a special paper to print.
■ It cannot produce multiple copies of a document.
Application: These printers are used at some POS terminals to print receipts.
LASER PRINTER
Laser printers are extremely fast and they can produce high-quality output. They can also print one page at a time. Laser printers work like a copy machine, using toner and a heat bar.
ADVANTAGES
■ Very fast (they can print from four to 16 pages per minute).
■ The produce high-quality printing.
■ They are extremely quiet.
■ They can print colour.
DISADVANTAGES
■ They are expensive to buy.
■ They cannot use multiple-copy paper.
These are used for printing of high-quality documents, images, etc, in schools, offices and business places. Additionally, they are ideal for printing several pages of a document in a short period of time.
3D PRINTERS
3D printing is carried out with a manufacturing process that creates a physical object from a digital design. There are different 3D printing technologies and materials you can print with, but all are based on the same principle: a digital model is turned into a solid, three-dimensional physical object by adding material, layer by layer.