A CD or compact disk holds around 700mb of information. This is the equivalent of around 486 floppy disks  (capacity at 1.44mb) for the 700mb size CD  .

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On a single sided DVD or digital versatile disk, it can hold around 4.7gb of data . This is roughly 4700mb so it would be the equivalent of around 6 CDs at the capacity of 700mb  .

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This is based on storing data only, when hold music or videos, the disks capacity are then based on playing time.

So for a 700mb CD it can hold roughly about 80 minutes of decent quality video or music. Considering most films are longer than 80 minutes, it meant that two or more CDs where needed to watch a film.

A single sided DVD can hold up to 6 hours (low low quality ) and around 1 hour high quality video.

There are also dual layer DVD disks which are 8.5gb or around 8704mbs , so that would be the equivalent of 12 CDs.

Recently a new form of digitial media has emerged called Blu Ray, this technology is mainly for showing high definition or HD movies. The capacity of such a disk is 50gb or around 51200mb so this would be the equivalent of aorund 73 CDs.