Compact Disk or CD as it is commonly known is an optical disk used to store data and information. Made of a polycarbonate material and as light as 20 grams, CD has a standard radius of 6 centimeters. Philips and Sony were one of the first manufacturers of the CD in mid 1970’s, by the end of 1980’s CD were becoming highly popular and became as preferred means of data storage.
Any form of data be it music files, text files, graphics, movies etc can be stored on the compact disk. A standard CD has about 700-800 MB (megabytes) of data storage capacity. The data in CD is stored in the divisions called pits which are embedded in the spiral tracks over the polycarbonate layer.
This polycarbonate layer is in turn covered by reflective layer (usually aluminum) and on top of that is added another layer of acrylic is added for protection. Labels at last are etched on the acrylic layer.
CD-ROM player is a device which is used to read and write the CDs. The two types of CDs are CD-R and CD-RW. CD-R is a cheaper because the data once written on this can not be erased and stays there. Whereas CD-RW (read/write) is a re-recordable CD where you can re-write the data on the CD as an when you require. CD-RW is tad expensive than CD-R.
CD is a sensitive device which is quite vulnerable to dust and scratches. During recent years use of CD has dropped considerably because people prefer to the pen drives or the USB which much more portable and can hold large amount of data.
