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e\L-lovely-eng\comm1-1.pmd IInd 16-9-11 IIIrd 27-12-11 IVth 4-1-12

Unit 1: Introduction to Computers

Printers: The printer takes the information on your screen and transfers it to paper or a hard copy.
There are many different types of printers with various levels of quality. The three basic types of Notes
printer are; dot matrix, inkjet, and laser.
• Dot matrix printers work like a typewriter transferring ink from a ribbon to paper with a
series or ‘matrix’ of tiny pins.
• Ink jet printers work like dot matrix printers but fires a stream of ink from a cartridge directly
onto the paper.
• Laser printers use the same technology as a photocopier using heat to transfer toner onto
paper.

What do you mean by printer? Explain the different types of printers.

Modem: A modem is used to translate information transferred through telephone lines, cable, satellite
or line-of-sight wireless.
The term stands for modulate and demodulate which changes the signal from digital, which
computers use, to analog, which telephones use and then back again. Digital modems transfer digital
information directly without changing to analog.
Modems are measured by the speed that the information is transferred. The measuring tool is called
the baud rate. Originally modems worked at speeds below 2400 baud but today analog speeds of
56,000 are standard. Cable, wireless or digital subscriber lines can transfer information much faster
with rates of 300,000 baud and up.
Modems also use Error Correction which corrects for transmission errors by constantly checking
whether the information was received properly or not and Compression which allows for faster
data transfer rates. Information is transferred in packets. Each packet is checked for errors and is re-
sent if there is an error.
Anyone who has used the Internet has noticed that at times the information travels at different
speeds. Depending on the amount of information that is being transferred, the information will
arrive at it’s destination at different times. The amount of information that can travel through a line
is limited. This limit is called bandwidth.
There are many more variables involved in communication technology using computers, much of
which is covered in the section on the Internet.
Scanners: Scanners allow you to transfer pictures and photographs to your computer. A scanner
‘scans’ the image from the top to the bottom, one line at a time and transfers it to the computer as a
series of bits or a bitmap. You can then take that image and use it in a paint program, send it out as
a fax or print it. With optional Optical Character Recognition (OCR) software you can convert printed
documents such as newspaper articles to text that can be used in your word processor. Most scanners
use TWAIN software that makes the scanner accessable by other software applications.
Digital cameras allow you to take digital photographs. The images are stored on a memory chip or
disk that can be transferred to your computer. Some cameras can also capture sound and video.
CASE: The case houses the microchips and circuitry that run the computer. Desktop models usually
sit under the monitor and tower models beside. They come in many sizes, including desktop, mini,
midi, and full tower. There is usually room inside to expand or add components at a later time. By
removing the cover off the case you may find plate covered, empty slots that allow you to add
cards. There are various types of slots including IDE, ASI, USB, PCI and Firewire slots.
Depending on the type notebook computers may have room to expand . Most Notebooks also have
connections or ports that allows expansion or connection to exterior, peripheral devices such as
monitor, portable hard-drives or other devices.

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