A printer is an output device makes a hardcopy from a softcopy.
Parameters or Criteria to Evaluate a Printers
A printer can be evaluated by four criteria:
1. Resolution: Printing resolution means the quality of image in a print. It is usually measured in dots per inch (dpi). The more dots a printer can print in one inch area, the picture quality is more high. A medium quality printer can print 300 dpi or 600 dpi.
2. Speed: Printing speed means how fast a printer can print. It is usually measured in page per minute (ppm). For some printer it is measured in character per second (cps). A graphics can take longer printing time than a text or character. The speed can be 6 to 20 ppm.
3. Initial Cost: Initial cost means the price of a new printer. The cost of a new printer is dramatically fallen in recent years.
4. Cost of Operation: The cost of operation means the cost of ink or toner and maintenance. The cost of operation increases with the quality of printing.
Classification of Printers
Printers are classified according to following criteria:
1. According to Printing Capability:
Printing capability means how much a printer can print at a time. Under this classification printers are following three types:
(a) Character Printer: A character printer can print one character (text) at a time. Example, Dot matrix printer, Ink jet printer etc.
(b) Line Printer: A line printer can print one line of characters (texts) at a time. Printing quality (resolution) is not high but high speed printing (up to 3000 lines of text per minute). Example, Chain printer.
(c) Page Printer: A page printer can print one page of characters (texts) at a time. Printing quality (resolution) is high and high speed printing (up to 3000 lines of text per minute). Example, Chain printer.
2. According to Printing Mechanism:
Printing mechanism means how a printer print a character. Under this classification printers are following two types:
(a) Impact Printer: Impact printer uses print head to generate the shape of a character. The head is used to strike on a ribbon against a paper to make a carbon-copy of a character. Example: Dot matrix printer, Daisy wheel printer etc.
(b) Nonimpact Printer: Nonimpact printer does not use any head to generate the shape of characters. Instead of that, it uses ink spraying or light falling mechanism to generate the characters on paper. Example: Ink jet printer, Laser printer etc.
Dot Matrix Printer
A dot matrix printer is a character type impact printer. Its printing mechanism can be compared with a type writing machine.
This printer uses a head with tiny (short) pins. The pins are arranged in row by column form like a matrix. This arrangement of pins can make any shape of characters. When a character is needed to take print, then only those pins of the matrix which are associated to generate the shape of that character are move forward from the head. The head then strikes on the ribbon against a paper and only the forwarded pins touches the ribbon. As a result a shape of the desired character is generated on the paper like a carbon copy. At the end of a line the page is scrolled up and the print head starts to take print of the next line.
As this is an impact type printer it produces bad noise during print. It is a slower printer because the mechanical movement of head is needed.