So What Is So Different About CDs and DVDs
CDs and DVDs have 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. The biggest difference that you will probably notice is that a DVD can hold far more data than a CD.
It becomes apparent how the big difference in storage capacity is achieved when you understand how data is written to a CD or DVD. By moving a laser across a spinning disc pits are burned into a spiral groove that covers the complete surface. Lasers have a wave length and the longer the wave length the bigger the pit. DVD lasers have a substantially smaller wave length than a CD laser. 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. Pits and lands (no pits) burned onto the surface of the disc are what make up the ones and zeros. When the disc is read the laser moves around the discs surface and is reflected off the lands but not off the pits. The information from the laser is converted by way of a microprocessor into digital data that a computer can understand.
Because the spiral groove is narrower on a DVD than a CD it is subsequently longer and able to hold more data. The most common DVD format can hold 4.5GB of data which is approximately six times more than a CD which only holds 700MB. Other DVD formats can hold a lot more given that they are double sided or dual layered.
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.
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.
DVD’s are currently the format of preference for many consumers nowadays but expect them to be taken over by Blu-Ray discs in the next few years. CDs will be available for a while yet but as Blu-Ray prices come down and storage needs continually spiral upwards I can’t see them lasting forever. For additional related information on Compact disks and DVDs in regards to presentation and marketing check out the following website CD and DVD Packaging
Guide on how to convert files to pdf format at How to PDF
