So What’s So Different About CDs and DVDs
Even though both CD and DVD disks have the same media size and shape, the things they have in common end there. 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. As the disc spins a laser is moved across the surface to burn pits in a spiral groove around the disc. Because lasers operate on a particular wave length a smaller wave length will burn a smaller pit. A smaller pit obviously takes up less space and ultimately resulting in the ability to store more information in the same amount of surface area.
Digital data is data that is stored as a series of ones and zeros. DVDs and CDs are digital data storage mediums so everything, including audio and video, is stored as ones and zeros. Pits and lands (no pits) burned onto the surface of the disc are what make up the ones and zeros. The laser light will reflect off the lands but not off the pits when the disc is being read. The information from the laser is converted by way of a microprocessor into digital data that a computer can understand.
The spiral groove on a DVD is also narrower than a CD. This equates to a longer track and subsequently more data storage capacity. The average single layer DVD holds 4.5 GB of data, while a CD holds only 700 MB..
A DVD has smaller pits and the lasers need to focus on them so the physical make up of a CD is slightly different to a DVD. 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.
DVD technology also has a much faster rate of reading and processing data. 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.
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 available but I imagine they will eventually go the way of the floppy disk as new technologies keep emerging. For more related information on CDs and DVDs in regards to presentation and marketing take a look at the following website CD and DVD Packaging