Difference between CD and DVD



In computers, several types of secondary storage devices like CDs, DVDs, Blue-Ray Discs, HDDs, etc. are used for permanent storage of data and information. Both CD and DVD are the types of optical storage devices whose operation is based on the optical effects. Both CD and DVD use red LASER to perform read and write operations. However, they are quite different from each other in many aspects.

In this article, we will discuss all the important differences between CD and DVD. Let's start with some basics of CD and DVD.

What is a CD?

CD stands for Compact Disk. CD is an optical storage device used in computers for the permanent storage of data and information. It is an external storage device as it can be separated from the computer without using any tool. CD is also categorized as a secondary memory device because it is used to store those parts of data on which the CPU is not currently working.

CD was the first step toward the digital coding of information that uses a new coding technique in which a 14-bit code indicates a unit of computer memory. This coding technique also helps in error detection. CD was used for a long period in place of magnetic disks due to their low cost and significantly high storage capacity.

CD makes use of laser light to read and write the data. Where the intended portion of the CD reflects the laser beam which is then detected by a photodetector. The most common variants of CD are – CD–ROM, CD-R (Recordable), and CD-RW (Re-Writable).

What is a DVD?

DVD stands for Digital Versatile Disk. It is also an optical storage device that is used as the secondary storage media in computers. The construction and operation of DVDs are almost similar to that of CDs. The major difference is that a typical DVD can acquire about 7 times more amount of data as compared to a CD.

DVDs can render multimedia files like videos with excellent picture quality and also provide random access to data. In the case of DVDs, the commonly used error detection and correction techniques are – RS-PC (Reed-Solomon Product-Code) and recording code EFMPlus (Eight-to-Fourteen Modulation Plus).

The main reasons behind the larger storage capacity of a DVD as compared to a CD are that the DVD provides dense packing of the data bits, uses a laser beam of shorter wavelength, and uses a two-sided disc. Just like CD, DVD is also available in three common variants, i.e. DVD-ROM, DVD-R, and DVD-RW.

Difference between CD and DVD

Both CD and DVD are optical storage devices having similar constructional and observational features, however there are several differences between them, which are highlighted in the following table −

Parameter CD DVD
Definition CD stands for Compact Disk. DVD stands for Digital Versatile Disk.
Size CD size is 700 MB. DVD size ranges from 4.7 GB to 17 GB.
Recording Layer Recording layer or metal layer is close to top of the disk. Recording layer or metal layer is close to middle of the disk.
Pits CD have single layer of pits. DVD have double layers of pits.
Space between loops Space between spiral loops is 1.6 micrometer in CD. Space between spiral loops is 0.74 micrometer in DVD.
Space between pits Space between pits is 0.834 micrometer in CD. Space between pits is 0.40 micrometer in DVD.
Correction code CIRC and EFMP are used as error correction code. RS-PC and EFMPlus are used as error correction code.
Data Transfer Rate Data Transfer Rate is 1.4 to 1.6 Mb/Sec. Data Transfer Rate is 11 Mb/Sec.
Channel Bit Length Channel Bit Length in CD is 300 nanometer. Channel Bit Length in CD is 113 nanometer.
Numeric Aperture Numeric Aperture of CD is 0.45. Numeric Aperture of DVD is 0.6.
Thickness CD thickness is 1.2 mm. DVD thickness is 0.6 mm.

Conclusion

The most significant difference that you should note here is that a CD has a storage capacity of about 700 MB, while a DVD has a comparatively higher storage capacity, ranging from 4.7 GB to 17 GB. Also, CDs are mainly used for the storage of audio files, while DVDs are considered a universal format storage because they can store multimedia files like audio files, video files, images, etc.


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