Output Devices
Output devices are those devices which translate information process by the computer into a form which we can understand. Output devices are divided into two types namely: Hard copy output and soft copy devices.
HARDCOPY OUTPUT DEVICES
Printers
A printer is a device which prints information sent from a computer on to paper, Printers can be divided into two broad groups, namely: Impact Printers and non-impact printers\
Impact Printers
Impact printer is a printer with mechanism which hits something to create a character. Typically a metal type - element bangs against an ink - coated ribbon on to paper. The two main types of impact printers are dot matrix and line printers
Dot Matrix printers
This technique for printing or displaying builds up characters as a pattern of dots with a 'matrix' which comprises a rectangle of possible dot positions.
A dot matrix printer contains a print head with pins(18 or 24) arranged in a rectangular matrix of rows and column. Those print one character at a particular time, depending of course on how the pins within the head are aligned. When a character or image is to be printed the pins that are required to from that character move forward and strike an inked ribbon, which then strikes the paper, Ink is transferred from the ribbon to the paper.
The quality of print is very good. A 24 - pin, which prints the best quality in terms of a dot matrix printer, can print 144 dots per inch (dpi). These printers are fast becoming obsolete but are still in use by companies that print multiple copies of documents such as invoices.
Line Printer: A line printer is a printer which prints one line at a time. It contrast with serial printer, which prints one character at a time. Line printers are generally faster and more complicated, so they tend to be more expensive, some of these printers print up to 3000 lines per minute, There are two types of line printers, they are Chain Printers, which contain characters on a rotating chain, and band printers which contain characters on a rotating band.
NON-IMPACT PRINTERS
This is a printer which works with something hitting a piece of paper, Example include thermal, electronic and ink-jet printers. Non-impact printers are faster, quieter and produce better quality print than impact printers. The beauty of this type of printer is that characters and images are formed without the printing mechanism making any direct physical contact with the paper.
Laser Printers: These Printers produce a very high quality output (letter Quality of LQ) with resolutions varying from 300 dots per inch (dpi) to 1200 dots per inch (dpi) and at terrific speeds. Laser printers are also known as page printers, and in some cases can produce more than 40 pages per minutes.
Laser Printers use the same principles with photocopying for printing a laser bean creates an image of a page on a light sensitive drum, treated with a magnetically charged powder called a toner. The paper is then pressed against the drum and heat and pressure are applied, The image is then transferred to the paper.
InkJet Printer: An Alternative to daisywheel printers as a printing technique which produces letter quality output good enough for work processing. A, B, Dick, now a GEC subsidiary, invented ink-jet printing and holds the patent; IBM is one of very few companies with a working ink-jet printer to sell, though it seems to have lost some enthusiasm for the idea. The quality which varies from 320 dpi to 720 dpi, is very high. Inkjet printers can print text and graphics in colour or black and white. The major difference between inkjet printers and Laser printers is that sometimes inkjet printing has more of a tendency to smudge. Inkjet printers are cheap compared to laser printers.
Thermal Printers: A thermal Printer is a type of non-impact which involves building up a character on the sheet by scorching dots on the paper in the appropriate shape. It sounds chumsy but thermal printers are neat, silent and reasonably fast. One disadvantage, though, is that they are not cheap; and they tend to need special coated paper, because trying to put a black dot on to ordinary paper by heat does not work too well.
Hard-copy Devices
Printers: it may be defined as a machines used for obtaining printed output, otherwise known as hard-copy.
TYPES OF PRINTERS
the main types of printers are: character printers, line printer, Optical printer and page printer
