Data storage media is used to record and store large-scale data from computer systems. Examples include optical disks and magnetic tapes. Data storage media, such as magnetic tape, consists of a magnet oxide coating on a thin plastic strip that is commonly used for backup and archiving. An optical disc is a type of data storage media that is made of polycarbonate, which allows data to be read by a laser light that shines through the polycarbonate hitting the data layer. Storage on digital optical media has the advantage of large capacity. Optical media are used for storing digital sounds, images, and data. Three types of optical media can be used to store digital information: CD-ROM; Write Once, Read Many (WORM); and rewritable media. CD-ROM, CD-R, and WORM technologies provide long-term storage of digital information because they cannot be erased or revised.