CDs and DVDs possess the same shape and size but that is where the similarities end. The differences lie in the make up of the surface of the disc which are invisible to the naked eye. There are many different things between the two, such as what they hold and how much they can hold.
When you discover how the data storage is implemented on both CDs and DVDs you will understand how the big difference in capacities is achieved. A laser is used to burn pits around a spiral groove in the disc. A laser is an intensely focused beam of light and all lasers operate on a particular wave length. A smaller wave length will create a smaller pit. Consequently you can have more pits in the same amount of surface area on a DVD, which explains the large difference in storage capacity.
DVDs and CDs are digital storage mediums which basically means that all data is stored as ones and zeros. The pits and lands (where there are no pits) on the DVDs and CDs represent ones and zeros. The laser light will reflect off the lands but not off the pits when the disc is being read. Optical technology reads the data and converts into the ones and zeros that your computer can then understand.
As thinkers, mankind has ever divided into two sects, Materialists and Idealists; the first class founding on experience, the second on consciousness; the first class beginning to think from the data of the senses, the second class perceive that the senses are not final and say, The senses give us representations of things, but what are the things themselves, they cannot tell. The materialist insists on facts, on history, on the force of circumstances and the animal wants of man; the idealists on the power of Thought and Will, on inspiration, on miracle, on individual culture.
—Ralph Waldo Emerson (1803–1882)
The tracks of a DVD are narrower as well, which allows for more tracks per disc and translates into more capacity than a CD. The average DVD can hold 4.5GB of data that is 6 times more than a CD at around 700MB.
As the pits on a DVD are smaller the physical make up of a DVD has to be different to a CD in order to allow the laser to focus on them. This is achieved by using a thinner plastic substrate than in a CD, which means that the laser needs to pass through a thinner layer, with less depth to reach the pits.
DVDs will access data at a much faster rate than a CD can. A 52X CD-ROM can read data at 8.4Mb a second while a 24X speed DVD can read data at about 32MB a second. This is a massive speed increase.
To write it, it took three months; to conceive it three minutes; to collect the data in it—all my life.
—F. Scott Fitzgerald (1896–1940)
CDs and DVDs possess the same shape and size but that is where the similarities end. When you discover how the data storage is implemented on both CDs and DVDs you will understand how the big difference in capacities is achieved. DVDs and CDs are digital storage mediums which basically means that all data is stored as ones and zeros. The tracks of a DVD are narrower as well, which allows for more tracks per disc and translates into more capacity than a CD. As the pits on a DVD are smaller the physical make up of a DVD has to be different to a CD in order to allow the laser to focus on them. DVDs will access data at a much faster rate than a CD can.
With Blu-Ray being the new kid on the block and because it has such a massive storage ability DVDs will slowly be phased out as will CDs. CDs are still widely availabe but I imagine they will eventually go the way of the floppy disk as new technologies keep emerging. For additional related information on Compact disks and DVDs in regards to presentation and marketing check out the following website CD DVD Packaging. With Blu-Ray being the new kid on the block and because it has such a massive storage ability DVDs will slowly be phased out as will CDs.