Printers

• A printer is a piece of hardware for a computer.
• Printer accepts text and graphic output from a computer and transfers the information to paper, usually to standard size sheets of paper.
• Printers may vary in size, speed, sophistication and cost.

Common qualities of printer

Color

• Color is important for users who need to print pages for presentations or maps and other pages where color is part of the information.
• Color printers can also be set to print only in black-and-white.
• Users who don't have a specific need for color and who print a lot of pages will find a black-and-white printer cheaper to operate.

Resolution

• Printer resolution is usually measured in dots per inch (dpi).

Speed

• Speed of the printer becomes important if you do much printing.
• Color printer are slower than normal printer.

Memory

• Most printers come with a small amount of memory that can be expanded by the user.
• Having more than the minimum amount of memory is helpful and faster when printing out pages with large images or tables with lines around them.

Types of printer

Impact printers

• An impact printer makes contact with the paper.
• It usually forms the print image by pressing an inked ribbon against the paper using a hammer or pins.

Examples:

Dot matrix printers

• The dot-matrix printer uses print heads containing from 9 to 24 pins.
• These pins produce patterns of dots on the paper to form the individual characters.
• If there is more pins, the clearer the letters on the paper.
• Dot  matrix printers are inexpensive and typically print at speeds of 100-600 characters per second.

Daisy wheel printers

• In order to get the quality of type found on typewriters, a daisy wheel impact printer can be used.
• It is called daisy wheel printer because the print mechanism looks like a daisy, at the end of each petal is a fully formed character which produces solid-line print.
• Its speed is slow typically 25-55 characters per second.

Line printers

• Line printers or line-at-a-time printers can print a whole line at once.
• They can typically print the range of 1,200 to 6,000 lines per minute.
• They are used in business where large amount of material are printed.
• Drum, chain and band printers are line-at-a-time printers.

Drum printer

• A drum printer consists of a solid, cylindrical drum that has raised characters in bands on its surface.
• Typical speeds of drum printers are in the range of 300 to 2000 lines per minute.
• One revolution of the drum is required to print each line, that means that all characters on the line are not printed at exactly the same time.

Chain printers

• A chain printer uses a chain of print characters wrapped around two pulleys.
• Circuitry inside the printer detects when the correct character appears at the desired print location on the page.
• The chain keeps rotating until all the required print positions on the line have filled, then the page moves up to print the next line.
• Speeds of chain printers range from 400 to 2500 characters per minute.

Band printers

• A band printer operates similar to chain printer except it uses a band instead of a chain.
• Band printer has a steel band divided into five sections of 48 characters each.
• Font styles can easily be changed by replacing a band or chain.

Non-impact printers

• Non-impact printers do not use a striking device to produce characters on the paper; and because these printers do not hammer against the paper they are much quieter.

Examples:

Ink-jet printers

• Ink-jet printers work in the same as dot-matrix printers in the form images or characters with little dots.
• Ink-jet printers form characters on paper by spraying ink from tiny nozzles through an electrical field.
• It can print approximately 250 characters per second.
• The ink is absorbed into the paper and dries instantly. Various colors of ink can also be used.
• These printers produce less noise and print in better quality with greater speed.

Laser printers

• A laser printer works like a photocopy machine.
• Laser printers produce images on paper by directing a laser beam at a mirror which bounces the beam onto a drum.
• The drum has a special coating on it to which toner (an ink powder) sticks.
• Laser printers use buffers that store an entire page at a time, when a whole page is loaded, it will be printed.
• These printers can print eight pages per minute, but faster and print approximately 21,000 lines per minute, or 437 pages per minute if each page contains 48 lines.

Advantages

• The main advantage of Laser printer is its speed & efficiency at which it prints high quality graphics & text.
• Laser printers produce high quality output as compared to other printers.
• Laser printers are quite and does not produce disturbing sounds.
• They are also capable to produce color prints.

Disadvantages

• They are relatively costly as compared to other printers.
• The maintenance, repair & servicing charges are also high of these printers.
• Laser printers emit small amount of ozone and are hazardous to health and the atmosphere.