Printers

A printer is an output device that produces a hard copy of data. The resolution of printer output is expressed as DPI. Printers can be classified into different types in several ways. First, the printers can be divided into three categories by the way they print.

• Serial Printers: Also called a character printer. Print a single character at a time. They are usually inexpensive and slow.

• Line Printers: Print a line at a time. They are expensive and very fast. Line printers use a band, a chain, etc.

• Page Printers: Also called a laser printer. Print a page at a time. They usually use a laser to produce page images. Quality is best. This is a little bit expensive, but the price of the personal laser printer is decreasing. The price range of the personal laser printer is around $400, today.

• Impact Printers: Hammer hits ribbons, papers or print head. Dot-matrix and daisy-wheel printers are the example. Noisy.

• Nonimpact Printers: They do not have the hammer and do not hit. An example is an ink-jet and laser printer.

• Bit-Mapped Printers: Images are formed from groups of dots and can be placed anywhere on the page. They have many printing options and good printing quality. They use PostScript as a standard language for instructing a microcomputer.

• Character-based Printers: Printer print characters into the lines and columns of a page. These printers use predefined set of characters and are restricted in position of characters.

Daisy-Wheel Printer

Daisy-Wheel is a printer mechanism that uses any kind of hub (wheel) having a set of spokes at the margin of the hub. The wheel can be removed to use a different character set. The end of each spoke is a raised image of a type character. When the wheel is turned and the required character is aligned to the print hammer, the character is then struck into a ribbon and onto a paper with the hammer.
Daisy-Wheel Printer prints typewriter-like very high quality characters. However, they are slower and less reliable than dot-matrix printers. Microcomputer users seldom use this printer, because the better dot-matrix printers and inexpensive laser printers are available today.

Chain Printer

A chain printer uses a printing mechanism that uses character typefaces linked together in a chain. The chain spins horizontally around a set of hammers aligned with each position. When the required character is in front of the selected print position, hammer in that position hits the paper into the ribbon against the character in the chain.
This printer is not commonly found around microcomputers, because it is a very expensive, high-speed machine designed originally for mainframes and minicomputers. Chain printers are very reliable and can speed up to 3000 lines per minute.

Dot-Matrix Printer

Dot-matrix printers are printers that write characters and form graphic images using one or two columns of tiny dots on a print head. The dot hammer moving serially across the paper strikes an inked-ribbon and creates images on paper.
Dot matrix printers are popular printers used with microcomputers, because the printers are highly reliable and inexpensive. They are used for tasks where a high-quality image is not essential. Many users, however, move from dot printers to laser printers, because the price of laser printers is falling down. Several kinds of dot matrix printers are available with print heads that have 7, 9, 18, or 24 pins.

Ink-Jet Printer

Ink-jet is a printer mechanism that sprays one or more color of ink at high speed onto the paper and produces high-quality printing. This printer also produces color printing as well as high-quality image. That is, ink-jet printers can be used for variety of color printing at a relatively low cost. Ink-jet printing has two methods: Continuous stream method and drop-on- demand method.

Laser Printer

A laser printer is a printer that uses the electrophotograpic method used in a copy machine. The printer uses a laser beam light source to create images on a photographic drum. Then the images on the drum are treated with a magnetically charged toner and then are transferred onto a paper. A heat source is usually applied to make the images adhere.
In 1984, Hewlett-Packard introduced the first desktop laser printer, called the LaserJet. The laser printer revolutionized personal computer printing and has spawned desktop publishing.
The laser printer produces high-resolution letters and graphics quality images, so it is adopted in applications requiring high-quality output. Although a high-priced color laser printer is also available in the market, a less expensive, desktop gray scale laser printer is widely used. Recently, the laser printer is gaining its market share dramatically, mainly because the lowered price and the quality.

Soft/Hard Copy: The images output on a monitor screen are often called soft copy. Information output on paper is called hard copy.

DPI: Dpi refers to a dot per inch. This is the number of dots printed within a linear inch.

Desktop Publishing: This means that the use of a microcomputer to produce high-quality printed output. This requires a desktop publishing software, a high-speed microcomputer, a big display monitor and a laser printer. The software specially designed for desktop publishing enables users to merge text and graphics.