The CD/DVD are optical mass storage media. They can store more information in a small space than floppy disks but less than hard disks.

They have a capacity of hundred of MB.

One of the major features of CD/DVD recorders and players is their information transmission speed: a higher speed indicates a better system response. Early CD recorders and players had speeds of 1x, 2x, 3x, but speeds have gradually increased. Today’s speeds are calculated by multiplying by 150.

For example, 48x indicates a speed 48×150 = 7200 kB/sec.