1. Introduction of Computer
1.3 Components of Computer System?
1.3.4 Other Output Unit
Printers are primary output devices used to prepare permanent documents for human use. Printers are classified as:
i). Letter Quality Printer
ii). Line Printer
These operate like a typewriter, pressing a typeface against paper and inked ribbon. e.g. daisy-wheel printer , dot-matrix printer.
i). Letter Quality Printer: These are also called character printers or serial printers because they print one character at a time. They produce a very high quality print image (one that is very clear and precise) because the entire character is formed with a single impact such as a Daisy Wheel Printer or a Dot Matrix Printer.
a) DMP (Dot Matrix Printer): These are serial printers, i.e., they print one character at a time. Each character is printed as a pattern of dots.
b) Daisy Wheel Printer: These printers have a print wheel with a set of print characters on the outside tips of flat spokes. You can print a specific character through spinning the wheel.
ii). Line printers
These are very high speed printers, which cater to huge volumes of output requirements of large computer organisations. These are known as Line printers because they use impact methods to produce one line at-a-time printed output. e.g. chain printer, band printer, drum printer.
The ink jet printer ejects a steady stream of ink drop towards the printed page. The drops are selectively discarded by electrostatic attraction to leave only those that are needed to form the desired symbol. Those that are not needed are captured in a tiny gutter & filtered to remove impurities. They are then recirculated through the drop-generating mechanism.
iii). Laser Printer
This printer is much less mechanical than impact printer (that is, no print heads move, no print hammers hit). resulting in much higher speeds and quieter operation. The process resembles the operation of a photocopy machine.
The major advantages of laser printers are:
1. Very high speed.
2. Low noise level.
3. Low maintenance requirements.
4. Very high image quality.
5. Excellent graphics capabilities.
This is one of the most important Peripheral device in the computer system. The following different kinds of display devices are available:
1.Liquid crystal Display(LCD):
Earlier LCDs were used commonly in watches and clocks . But nowadays LCD is applied to display devices of a computer. The major advantage of LCD is the low eneregy consumption.They also have colour capability but the image quality is relatively poor.
A large screen upon which images are projected replaces a personal size of the previous displays. These systems can be connected to computer and whatever appears on the computer terminal gets enlarged and projected on a large screen. Another method is to connect a computer to an LCD Flat screen and to project the LCD Image using Overhead projector. These are popularly used for seminars, classroom lectures and presentations etc.