Optical disc composed of a phase change material, most often AgInSbTe, an alloy of silver, indium, antimony, and tellurium. Optical discs are most commonly used for storing music (e.g. for use in a CD player), video (e.g. for use in a Blu-ray player), or data and programs for personal computers (PC). The Optical Storage Technology Association (OSTA) promotes standardized optical storage formats. Although optical discs are more durable than earlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage. Libraries and archives enact optical media preservation procedures to ensure continued usability in the computer's optical disc drive or
Optical disc drive maximum speed (56× for CDs or around 18× in the case of DVDs) at which drives can operate. Current optical drives use either a "tray-loading" mechanism, where the disc is loaded onto a motorized or manually operated tray, or a "slot-loading" mechanism, where the disc is slid into a slot and drawn in by motorized rollers. With both types of mechanism, if a CD or DVD is left in the drive after the computer is turned off, the disc cannot be ejected using the normal eject mechanism of the drive. However, tray-loading drives account for this situation by providing a