Question 1:

What is the diferrence between dot-matrix , inkjet and laser printer ?

Answer :
Dot Matrix printer uses a print head with a 9 , 18 or 24 rigid vertical wires that form symbols by stricking a ribbon to create a matrix , or grid , of dots on the paper . The more dots in a matrix and the closer together the dots are , the better the quality of the symbol formed .

Inkjet Printer form dots on paper by spraying ink from a row of tiny nozzles.

Laser printer use a laser beam to 'write' dots on a drum coated with light-sensitive material . The pattern of dots is then transferred to paper using a toner .

Question 2 :

What is modem ?

Answer :
Modem is a communication device that modulates computer signals into outgoing audio signals and demodulates incoming audio signals into computer signals.