A computer printer is a very important I/O peripheral device. A printer is an output device. A printer connected to a computer allows users to take printout of text and graphics on the plain papers. The printout is also called hardcopy because printout is permanent in nature. Printers are broadly classified by the manner the image is formed on the paper that is whether the output produced is result of physical contact of the print mechanism with the paper or without physical contact. There are two categories of printers:
- Impact printers
- Non-impact printers
An impact printer has machinery that resembles to that of a typewriter. The characters or images are formed by striking a print hammer or wheel against an inked ribbon, which makes an image on paper. The various types of impact printers are:
A dot-matrix printer has a print head which contains small pins. These small pins strike with the inked ribbon installed in the printer, to form characters or images. The Print heads may have 9, 18, or 24 pins. The 24-pin head produces the best print quality. Color ribbons are available.
Characters of Dot-matrix printers are:
- Speed : 40 to 300 characters per second
- Low cost
- Ability to create multiple copies of a page at once.
- Poor graphics image quality
A daisy-wheel printer is a serial impact printer. That means it prints character by character. This printer has a metal or plastic disk which contains all the numbers, letters and other characters. To print a character, the printer rotates the disk to the particular character then strikes hammer on each character into the ink ribbon. Daisy-wheel printers are now not in use because of:
- Low print quality
- Slow speed, about 10 to 75 characters per second
- No graphics printing option
Chain printer is also a character printer. It has a chain or metallic band that contains the embossed characters. This chain rotates horizontally in front of paper. A complete chain has five sections with each section having 48 characters. To print a character, the print chain rotates and the hammer strikes the ink ribbon into the paper. The chain printers are fastest impact printers with a speed of 400 to 2500 characters per second. Chain printers are also called as band printers.
Drum printer consists of solid, cylindrical drum which has a complete set of characters for each print position on a line on the surface. The drum continuously rotates behind an inked ribbon and paper is placed in the front of the ribbon. Same or identical characters, in a line, are printed simultaneously at all required positions. One line is printed in one complete revolution of the drum, so all the characters in a line are not printed simultaneously. Approximate speed of drum printers is 300 to 2000 lines per minute
Line printers are high-speed printer that can print an entire line at one time. Maximum speed of line printers is printing about 3,000 lines per minute. The disadvantages of line printers are
- Low print quality
- Very noisy.
- Graphics not supported
Non-impact printers produce very less noise because they don’t physically hit the page. Presently non-impact printers are being used everywhere. Types of non-impact printers are:
Similar to dot-matrix printers, laser printers also make images using dots. Laser printers have their own small dedicated processor which is stored in a ROM Chip.
Laser printers are very popular because they:
- Produce precise, sharp and crisp images of text and graphics.
- Have good resolution ranging from 300 dpi to 1200 dpi.
- Can print 4-32 text pages per minute using individual microcomputers, and approximately 120 pages per minute for mainframes.
- Inbuilt RAM chip to store output ram computer.
To print, ink-jet printers form images with little dots. They sprinkle with high speed tiny, electrically charged drops of ink from four nozzles through holes in a matrix onto paper. Ink-jet printers are color printers. Features of inkjet printers:
- Less expensive
- Least noise
- Low resolution and less speed than laser printers
- High resolution printers are very slow
These are portable printers. It uses small heating elements to throw out ink from print heads with 128 nozzles. Because of multiple nozzles output produced is of good quality and at high speed.
Thermal printers work by pressing heated pins over heat-sensitive paper. Thermal printers are used in fax machines and calculators. Characteristics of thermal printers are:
- fast and less noisy
- no ink required
- consumable material is paper
Plotters are used in engineering applications where accuracy and precision are required. It prints images on paper according to given commands from a computer. Plotters can draw continuous lines using a pen, whereas other printers draw lines by printing a closely positioned series of dots. Multicolor plotters draw colored images. Plotters are expensive than printers.
Printers are explained in this articles as they are very important I/O peripheral device. Both impact and non-impact printers have their own significance and uses. Now-a-days, non-impact printers are replacing by impact printers and eventually impact printers will be out of market. Non-impact printers are less noisy but can be really have printers which are literally silent?