How is information written on CDs and floppy disks?
On music and computer CD’s, the information is held in the form of a long spiral line of pits or craters winding around the centre of the CD. The information is read by shining a laser onto the track with amount of reflection being used to decide whether a pit is present or not. On floppy disks the information is stored magnetically with small areas of the disk being set to that of a north or south magnet. As the disk rotates it moves under a head which can detect and alter (if wanted) the magnetic state of each small area.
