Hard-copy output devices
GOOD DAY, students. This is lesson four in series of lessons. In this week’s lesson, I will be concluding output devices. At the end of this lesson, you should be able to define the term ‘hard-copy’, distinguish between the different impact and non-impact printers.
Hard-copy output devices are devices 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 hardcopy 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, just like the examples given above, with the pictures. The quality of what is on paper and how fast the information is put on the paper is dependent on the choice of printer.
CHARACTERISTICS OF PRINTERS
Printer speed – The speed of a printer is measured in: CPS = Character per second LPM = Lines per minute PPM = Pages per minute
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.
ADVANTAGES
Less expensive. Can make multiple copies of a document (carbon copies or multiform).
DISADVANTAGES
Noisy. Quality is poor. Poor graphics or none at all. Impact printers include: Dot matrix, daisy wheel and ‘band’ or ‘train’ printer.
TYPES OF IMPACT PRINTERS DOT MATRIX
This printer is relatively inexpensive and can print between 100-200cps. 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 scoreboard shows its data, that’s how characters are formed using the dot matrix. Some printers are unable to produce graphics, only letters and numbers.
ADVANTAGES
Inexpensive. Can make multicopy forms.
DISADVANTAGE
Slow.
DAISY WHEEL
This printer operates at slow speeds, less than 75cps. It is noted for letter quality and is used extensively for professional word processing. Characters are fully formed on the ‘petals’, like typewriter keys. The petal strikes an inked ribbon to produce a character.
ADVANTAGE DISADVANTAGES
Very slow (will print between 20 to 80cps). Only one font can be used at a time because one must change out the daisy wheel to change fonts. Cannot print graphics.
BAND OR ‘TRAIN’ PINTER
The character set is in a continuous loop of characters. Usually, the complete character set is repeated several times around the loop. The loop rotates in a horizontal line. There is a set of hammers across the paper. The hammer for each character position strikes the paper and a carbon on to the right character on the chain as it goes around.
ADVANTAGES
Very fast. Will print up to 3,000 lines per minute.
DISADVANTAGES
Very expensive. Very loud.
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.
ADVANTAGES
Quiet. Can print graphics and often a wider variety of fonts than impact printers.
DISADVANTAGE
More expensive. Cannot produce multiple carbon copies. Non-Impact printers include: Ink jet, thermal and laser printers.
TYPES OF NON-IMPACT 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
Quiet. Produces high-quality text and graphics. Able to print colour. Faster than impact printers.
DISADVANTAGES
Cannot produce multiple copies. Ink can smear on the paper after printing is done.
THERMAL PRINTER
This type of printer uses heat on chemically treated paper to form characters. A thermal printer is similar in nature to a fax machine that uses special rolls of paper.
ADVANTAGE
Quiet.
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DISADVANTAGES
Expensive and requires a special paper to print. Cannot produce multiple copies of a document.
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 machines, using toner and a heat bar.
ADVANTAGES
Very fast (they can print from 4 to 16 pages per minute). Produce high-quality printing. Extremely quiet. Can print colour.
DISADVANTAGES
Expensive to buy. Cannot use multiple-copy paper.
PLOTTERS
A plotter is a special-purpose output device (considered to be also a printer) that is used to produce sophisticated graphs, charts, maps and three-dimensional graphics as well as high-quality, coloured documents. It can also be used to print larger size documents. There are two main categories of plotters: vector and raster plotter.
MICROFICHE
The computer can output tiny images on rolls/sheets of microfilm. Microfiche is a rectangle sheet of microfilm large enough to contain a number of pages (or frames) of data. It can store from 30 to 300 pages. One microfiche is equivalent to 200 pages of A3 paper.
DISK OR TAPE
This is a triple-purpose media. It is used for input, storage and output. The CPU can send output directly to disks or tapes. It is also classified as being a machine-readable device. We have come to the end of this lesson. See you next week. Remember, if you fail to prepare, you prepare to fail.