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.
The reason for the big difference in the amount of data storage will become apparent when you understand how data is written to or burned to CDs and DVDs. As the disc spins a laser is moved across the surface to burn pits in a spiral groove around the disc. A laser is an intensely focused beam of light and all lasers operate on a particular wave length. 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.
DVDs and CDs are digital storage mediums which basically means that all data is stored as ones and zeros. Pits and lands (an area where there are no pits) represent ones and zeros. The laser light will reflect off the lands but not off the pits when the disc is being read.
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 DVD can hold 4.5GB of data that is 6 times greater than a CD at around 700MB.
The DVD has a thinner plastic substrate than a CD making it easier for the laser to pass through and get reflected back.
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.
CDs are still widely available but I imagine they will eventually go the way of the floppy disk as new technologies keep emerging.
Additional resources:
Logitech left handed mouse
microsoft trackball
microsoft wireless notebook optical mouse 4000
children's computer keyboard
waccom
The reason for the big difference in the amount of data storage will become apparent when you understand how data is written to or burned to CDs and DVDs. As the disc spins a laser is moved across the surface to burn pits in a spiral groove around the disc. A laser is an intensely focused beam of light and all lasers operate on a particular wave length. 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.
DVDs and CDs are digital storage mediums which basically means that all data is stored as ones and zeros. Pits and lands (an area where there are no pits) represent ones and zeros. The laser light will reflect off the lands but not off the pits when the disc is being read.
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 DVD can hold 4.5GB of data that is 6 times greater than a CD at around 700MB.
The DVD has a thinner plastic substrate than a CD making it easier for the laser to pass through and get reflected back.
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.
CDs are still widely available but I imagine they will eventually go the way of the floppy disk as new technologies keep emerging.
Additional resources:
Logitech left handed mouse
microsoft trackball
microsoft wireless notebook optical mouse 4000
children's computer keyboard
waccom
