also the places and examples of their use
What is a moden? The answer to your second question is: Its about the materialsLet me give you an example: CD-ROM: Take a sheet of aluminum foilPlace it flat on a flat cutting board, then poke holes in various places with a forkThese holes are permanent and will not healThis is the way a CD/CD-Rom worksHoles are actually drilled through some metal with a powerful laser beamWhere the holes are become 0 and where the holes are not become 1READ-WRITE: Sprinkle a handful of rice on the cutting boardCover with a fresh piece of aluminum foilThen run your hand or a rolling pin over the foilYou will see 'bumps' in the foil Remove the foil, remove the rice and put the foil back down and run over it with the rolling pinThis tends to make the 'bumps' disappearPut rice down in a different pattern, smooth and you get a new set of bumpsThis is exactly the way a computer-burned CD-R or CD-RW worksA sheet of foil is sandwiched between layers of plasticA weak laser in your burner melts the plastic which creates a 'bump' in the foilCD drives read the bumps as 0 and non-bumps as 1Hope this helps.
