Full Form of CD
CD Full Form is Compact Disc. It is a kind of optical disk used for storing digital data such as text, video, audio etc. It was originally used for storing music and other forms of sound which was popularly known as “Audio CD”. Later CDs were made which were capable of storing other types of computer files. A compact disc is a round, small, portable medium, mostly made up of molded polymer, used to store media such as audio, video, and text electronically in digital format. CDs are designed strictly according to the international standards set by Philips and sony, the pioneers in manufacturing CDs, in order to be universally compatible.
The diameter of a CD is 4.72 inches (120 millimeters) and its thickness is 0.47 inches (1.2 millimeters). The positioning hole, present in the middle of the CD is 0.59 inch (15 millimeters) in diameter. Mostly CDs weigh around 15 grams. It can store about 74 minutes of data. However, most CDs can only hold up to 50 minutes of audio, which is only recorded on the underside of the disc. The data recorded on the CDs takes the form of a continuous spiral which starts from the inside then moving outwards. This spiral, also known as track, is made up of indentations known as pits, bifurcated by sections known as lands.
A miniature laser beam which moves along the track is responsible for the reflection of light back to a photosensor. The sensor gets more amount of light when on land than on pit, and these variations in light intensity get converted into electrical signals which represent the music originally recorded. Earlier, CDs used to be read-only, i.e. they could only be used to read the data they have, the user could not transfer his data into the CD. But, now rewritable CDs are also available. Other popular variations of the compact disk are CD-i, CD-RW, CD-ROM, CD-W, CD-ROM XA, video CD, photo CD.