Difference Between CD and DVD (With Table)

Media storage in computer systems has evolved exponentially in the last couple of decades. From floppy disks to CDs and DVDs to USBs and now SSDs and HDDs, methods of memory storage have come a long way. Improvements in computer technology have made it possible to store large bits of data in the smallest of devices, taking a fraction of the storage space.

CD vs DVD

The main difference between CD and DVD is that although DVDs are made from the same materials like CDs, there are two reflective layers in DVDs which allow for more storage space, as opposed to only one reflective layer in CD. Thus DVD can hold more bits of data than a CD, increasing its efficiency as well as the quality of storage.

A Compact Disc (CD) is an optical disc that is used to store bits of data. The storage capacity of a normal CD is 700 MB, with each byte comprising 14 bits. The first layer of a CD is constructed of Polycarbonate plastic which is used to store the data. The data is stored in pits indented onto the polycarbonate surface.

Digital Versatile Disc (DVD) was invented to provide a way of storing digital data without losing the quality of the data. Since digital data is usually big, there was a need for a more effective means of storage. A typical DVD can store 7 times as much data as a CD.

Comparison Table Between CD and DVD

Parameters of ComparisonCDDVD
DefinitionCD stands for Compact Disc and it is an optical disc used to store bits of dataDVD stands for Digital versatile Data and it is an optical disc used specifically to store digital or video data
Storage capacityCD can store 700MB of dataA typical DVD can store 4.7 to 17 GB of data
Storage layersThere is only one storage layer in CDsThere are two storage layers in DVDs
Metal layer positionThe metal layer used for recording is positioned at the topThe metal layer used for recording is positioned at the middle
Spacing between recording pitsThere are 0.834 micrometers of spacing between each pitThere is 0.4 micrometer of spacing between each pit

What is CD?

Compact Disc (CD) is a type of optical disc used for storing bits of data. The storage capacity of a typical CD is 700MB, where one byte comprises 14 bits. CDs use laser light to retrieve data. The data is store in the polycarbonate layer, which is the first layer in a CD. The layer is indented with pits which are used for storing data.

The distance between each pit is 0.834micrometer. The data is engraved in the pits using high-intensity laser light. A thin aluminum material protects the recording layer, which is then coated with a thin layer of acrylic for more protection. There is only one reflective layer in a CD hence only a single layer of storage is available in a CD. For reading the bits stored in a CD, laser light is targeted on the pits on the polycarbonate layer. The pits reflect a portion of the light, which is detected by a photodetector inside the CD player.

The detected light portion is then interpreted by the integrated circuit in the CD player and is read in the form of bits of data. As there is only one layer of polycarbonate in a CD, the storage capacity is very limited. Hence over the years, CDs have become obsolete.

What is DVD?

Digital Versatile Disc (DVD) is an optical disc used specifically to store digital or video data. Since video data usually consist of a large byte of data, the storage capacity of DVD is also accordingly large. The storage capacity of a typical DVD ranges from 4.7 to 17 GB. This is due to the construction of the DVD. DVD is made from the same materials as a CD but it consists of twice as many layers as a CD.

In a DVD the data is stored onto a polycarbonate layer. In a CD, there is only one layer of polycarbonate. Hence the storage capacity of a CD is very limited. On the other hand, in a DVD there are two polycarbonate layers. Since there are two reflective layers in a DVD, there is twice as much storage space available in a DVD. The bits of data are engraved onto pits indented on the polycarbonate surface of the DVD.

In a DVD the pits are more closely spaced. The distance between two consecutive pits on a DVD is 0.4 micrometers. As there is dense packing of pits on a DVD, more bits can be stored, increasing the storage capacity of the DVD. Hence DVD is a more efficient and effective method of storing digital data than a CD.

Main Differences Between CD and DVD

  1. CD stands for Compact Disc. It is a type of optical disc used for storing bits of data. DVD stands for Digitally Versatile Disc and it is an optical storage media used specifically for storing digital or video data. 
  2. The storage capacity of a CD is 700MB. The storage capacity of DVD ranges from 4.7GB to 17 GB.
  3. There is only one layer of polycarbonate in a CD. There are two polycarbonate layers in a DVD.
  4. In a CD the metal layer used for recording is locate at the top. In a DVD the metal layer used for recording is located at the middle of the disc
  5. The spacing between each pits used for recording data in a CD is 0.834 micrometers. The pit spacing in a DVD is 0.4 micrometer.

Conclusion

The invention of optical discs for storing data provided a better alternative to using the floppy disc for storing bits of data.

Optical discs provided higher storage capacity while reducing the physical space of the data storing medium.

The two types of optical discs used more frequently are CDs and DVDs. CDs were invented first by companies like Sony and Phillips.

CDs provided a compact and quick method of storing computer data. DVDs use the same principle for storing data as CDs, but DVDs offer much more storage and efficiency than CDs.

Thus with the advent of DVDs, CDs became obsolete as DVDs offered a more efficient and effective method of storing data than CDs.

References

  1. https://www.aes.org/e-lib/online/browse.cfm?elib=12144
  2. https://www.google.com/books?hl=en&lr=&id=BGnxDwAAQBAJ&oi=fnd&pg=PR9&dq=compact+disc&ots=36ebh0vDhz&sig=MK0tsVuMoSNZYf9C_xlZQe4eBFE
  3. https://ieeexplore.ieee.org/abstract/document/7243464/
  4. https://iopscience.iop.org/article/10.1143/JJAP.37.2257/meta

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2D vs 3D