This is how the electronic head can both write to or read from the disk surface. Inside the CD-Rom is a laser that reflects light off of the surface of the disk to an electric eye. This is quite a bit more than the 1.44MB that a floppy disk stores. A DVD or Digital Video Disk holds even more information than a CD, because the DVD can store information on two levels, in smaller pits or sometimes on both sides. There are several reasons why portable storage is so important.
Floppies make it possible to backup important information in case it is lost by the computer.
RAM loses its memory each time the computer is turned off, but ROM keeps information stored even when the computer is not turned on. Well, sometimes computers have problems that can cause them to crash . A crash is something that happens inside the computer's circuits and can make it forget things. Having important information backed up on disks will allow you to put it back into your computer's memory. Disks also allow information to be transferred between different computers.