There are basically two types of disk storage for computers: magnetic and optical. In magnetic storage, data is recorded magnetically on rotating disks. Optical disc storage is similar to magnetic disk storage in basic operation, but it reads and writes using light (optically) instead of magnetism. Although most magnetic disk storage is fully read and write capable many times over, many optical storage media are either read-only or write-once. Note the convention in which we refer to magnetic as disk and optical as disc. This is not a law or rule but is followed by most in the industry.
At one time, it was thought that optical storage would replace magnetic as the primary online storage medium. However, optical storage has proven to be much slower and far less dense than magnetic storage and is much more adaptable to removable-media designs. As such, optical storage is more often used for backup or archival storage purposes and as a mechanism by which programs or data can be loaded onto magnetic drives. Magnetic storage, being significantly faster and capable of holding much more information than optical media in the same amount of space, is more suited for direct online storage and most likely won't be replaced in that role by optical storage anytime soon.
Optical technology standards for computers can be divided into three major types:
- CD (compact disc)
- DVD (digital versatile disc)
- BD (Blu-ray disc)
All of these are descended from popular music and video entertainment standards; CD-based devices can also play music CDs, and DVD and BD-based devices can play the same video discs you can purchase or rent. However, computer drives that can use these types of media also offer many additional features.
In the following sections, you will learn how optical drives and media are similar, how they differ from each other, and how they can be used to enhance your storage and playback options.